ChesMMAP Final Report 2008

FINAL REPORT

Data collection and analysis in support of single and multispecies stock assessments in Chesapeake Bay: The Chesapeake Bay Multispecies Monitoring and Assessment Program

Prepared for: Virginia Marine Resources Commission and U.S. Fish & Wildlife Service

For Sampling During: Calendar Year 2008 and Previous Years

Project Number: F-130-R-4

Submitted: May 2009

Prepared by: Christopher F. Bonzek James Gartland RaeMarie A. Johnson Robert J. Latour, Ph.D School of Marine Science College of William and Mary Virginia Institute of Marine Science Gloucester Point, VA 23062

Table of Contents Introduction

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1

Methods

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3

Results

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8

Species Data Summaries

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Atlantic croaker Black seabass Bluefish Butterfish Kingfish Northern puffer Scup Spot Striped bass Summer flounder Weakfish White perch

…………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. ………………………………………………………………….

9 11 13 14 15 17 18 19 20 23 24 25

Literature Cited

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Species Data Tables and Figures Atlantic croaker Black seabass Bluefish Butterfish Kingfish Northern puffer Scup Spot Striped bass Summer flounder Weakfish White perch

…………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. …………………………………………………………………. ………………………………………………………………….

Water Quality Figures Temperature Salinity Dissolved oxygen

…………………………………………………………………. …………………………………………………………………. ………………………………………………………………….

247 263 279

Appendix 1 – Species data summaries for blue crab (male and adult female) …………………………………………………………………. and clearnose skate

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Appendix 2 - Use of Yield-Per-Recruit and Egg-Per-Recruit Models to Assess Current and Alternate Management Strategies for the Summer Flounder Recreational Fishery in Virginia: An Application of Data ……………………………………………..

Collected by the ChesMMAP Trawl Survey

329

31 49 67 85 99 117 131 149 167 189 207 225

Introduction

Historically, fisheries management has been based on the results of single‐species stock assessment models that focus on the interplay between exploitation level and sustainability.

There currently exists a suite of standard and accepted analytical frameworks (e.g., virtual population analysis (VPA), biomass dynamic production modeling, delay difference models, etc.) for assessing the stocks, projecting future stock size, evaluating recovery schedules and rebuilding strategies for overfished stocks, setting allowable catches, and estimating fishing mortality or exploitation rates. A variety of methods also exist to integrate the biological system and the fisheries resource system, thereby enabling the evaluation of alternative management strategies on stock status and fishery performance. These well‐established approaches have specific data requirements involving biological (life history), fisheries‐ dependent, and fisheries‐independent data (Table 1). From these, there are two classes of stock assessment or modeling approaches used in fisheries: partial assessment based solely on understanding the biology of a species, and full analytical assessment including both biological and fisheries data.

Table 1. Summary of biological, fisheries‐dependent and fisheries‐independent data requirements for single‐species analytical stock assessment models.

Data Category Assessment Type Data Description Biological / Life History Partial Growth (length / weight) Maturity schedule Fecundity Partial recruitment schedules Longevity Life history strategies (reproductive and behavioral) Fishery‐Dependent Data Analytical Catch, landings, and effort Biological characterization of the harvest (size, sex, age) Gear selectivity Discards/bycatch Fishery‐Independent Data Analytical Biological characterization of the population (size, sex, age) Mortality rates Estimates of annual juvenile recruitment

Although single‐species assessment models are valuable and informative, a primary shortcoming is that they generally fail to consider the ecology of the species under

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management (e.g., habitat requirements, response to environmental change), ecological interactions (e.g., predation, competition), and technical interactions (e.g., discards, bycatch) (NMFS 1999, Link 2002a,b). Inclusion of ecological processes into fisheries management plans is now strongly recommended (NMFS 1999) and in some cases even mandated (NOAA 1996).

Multispecies assessment models have been developed to move towards an ecosystem‐based approach to fisheries management (Hollowed et al. 2000, Whipple et al. 2000, Link 2002a,b).

Although such models are still designed to yield information about sustainability, they are structured to do so by incorporating the effects of ecological processes among interacting populations.

Over the past several years, the number and type of multispecies models designed to provide insight about fisheries questions has grown significantly (Hollowed et al. 2000, Whipple et al.

2000). While this growth has been fueled primarily by the need to better inform fisheries policy makers and managers, recent concerns about effects of fishing on the structure of ecosystems have also prompted research activities on multispecies modeling and the predator‐prey relationships that are implied. From a theoretical perspective, basing fisheries stock assessments on multispecies rather than single‐species models certainly appears to be more appropriate, since multispecies approaches allow a greater number of the processes that govern population abundance to be modeled. However, this increase in realism leads to an increased number of model parameters, which in turn, creates the need for additional types of data.

In the Chesapeake Bay region, there has been a growing interest in ecosystem‐based fisheries management, as evidenced by the recent development of fisheries steering groups (e.g., ASMFC multispecies committee), the convening of technical workshops (Miller et al. 1996; Houde et al. 1998), and the goals for ecosystem‐based fisheries management set by the Chesapeake Bay 2000 (C2K) Agreement. In many respects, it can be argued that the ecosystem‐ based fisheries mandates inherent to the C2K Agreement constitute the driving force behind this growing awareness. The exact language of the C2K agreement, as it pertains to multispecies fisheries management, reads as follows:

1. By 2004, assess the effects of different population levels of filter feeders such as menhaden, oysters and clams on bay water quality and habitat.

2. By 2005, develop ecosystem‐based multispecies management plans for targeted species.

3. By 2007, revise and implement existing fisheries management plans to incorporate ecological, social and economic considerations, multispecies fisheries management and ecosystem approaches.

If either single‐species or ecosystem‐based management plans are to be developed, they must be based on sound stock assessments. In the Chesapeake Bay region, however, the data

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needed to perform single and multispecies assessments has been either partially available or nonexistent.

The Chesapeake Bay Multispecies Monitoring and Assessment Program (ChesMMAP) was developed to assist in filling these data gaps, and ultimately to support bay‐specific stock assessment modeling activities at both single and multispecies scales. While no single gear or monitoring program can collect all of the data necessary for both types of assessments, ChesMMAP was designed to maximize the biological and ecological information collected for several recreationally, commercially, and ecologically important species in the bay.

In general, ChesMMAP is fishery‐independent monitoring survey that uses a large‐mesh bottom trawl to sample late juvenile‐to‐adult fishes in the mainstem of Chesapeake Bay. This program currently provides data on relative abundance, length, weight, sex ratio, maturity, age, and trophic interactions for several important fish species that inhabit the bay seasonally. This report summarizes the data generated from the field and laboratory components of this project.

Among the research agencies in the Chesapeake Bay region, only VIMS has a program focused on multispecies issues involving the adult (i.e., harvested) components of the exploited fish species that seasonally inhabit the bay. The multispecies research program at VIMS is comprised of three main branches: field data collection (ChesMMAP), laboratory processing (The Chesapeake Trophic Interactions Laboratory Services – CTILS, and ChesMMAP), and data analysis and multispecies modeling (The Fisheries Ecosystem Modeling and Assessment Program ‐ FEMAP). The research group is also responsible for executing the nearshore trawl survey for the North East Area Monitoring and Assessment Program (NEAMAP). In this report, we summarize the ChesMMAP field, laboratory, and data analysis activities through the 2008 sampling year.

The following Tasks are addressed in this report: • Task 1 – Conduct research cruises • Task 2 – Synthesize data for single species analyses • Task 3 – Quantify trophic interactions for multispecies analyses • Task 4 – Estimate abundance

Methods

Task 1 – Conduct research cruises

In 2008, five research cruises were conducted bimonthly from March to November in the mainstem of Chesapeake Bay. The timing of the cruises was chosen so as to coincide with the seasonal abundances of fishes in the bay. The R/V Bay Eagle, a 19.8m aluminum hull, twin diesel vessel owned and operated by VIMS, served as the sampling platform for this survey.

Fishes (and select invertebrates) were collected using a 13.7m (headrope length) 4‐seam bottom trawl manufactured by Reidar’s Manufacturing Inc. of New Bedford, MA. The wings and body of the net are constructed of twisted #21 nylon twine (15.2cm stretch mesh), and the 3

codend is constructed of #48 twine (7.6cm stretch mesh). The legs of the net are 6.1m and connected directly to 1.3m x 0.8m steel‐V trawl doors weighing 71.8kg each. The trawl net is deployed with a single‐warp system using 9.5mm steel main cable and a 37.6m bridle constructed of 7.9mm wire rope.

For each cruise, the goal was to sample 80 sites throughout the mainstem of Chesapeake Bay. Sampling sites were selected using a stratified random design. The bay was stratified by dividing the mainstem into five regions of 30 latitudinal minutes each (the upper and lower regions being slightly smaller and larger than 30 minutes, respectively). Within each region, three depth strata ranging from 3.0m‐9.1m, 9.1m‐15.2m, and >15.2m were defined. A grid of 1.9km2 cells was superimposed over the mainstem, where each cell represented a potential sampling location. The number of stations sampled in each region and in each stratum was proportional to the surface area of water represented. Stations were sampled without replacement and those north of Pooles Island (latitude 39o 17’) have not been sampled since July 2002 due to repeated loss of gear. In the future, we plan to use sidescan sonar to identify potential sampling locations in this area.

Tows were conducted in the same general direction as the tidal current (pilot work conducted using the net monitoring gear in November 2001 indicated that the survey gear performed most consistently when towed with the current rather than against the current). The net was generally deployed at a 4:1 scope, which refers to the cable length: water depth ratio. For shallow stations, however, bridle wires were always fully deployed, implying that the scope ratio could be quite high in these particular situations. The target tow speed was 6.5 km/h but occasionally varied depending on wind and tidal conditions. Based on data collected from the net monitoring gear, tow speed and scope were adjusted occasionally to ensure that the gear maintained proper geometry. Tows were 20 minutes in duration, unless obstructions or other logistical issues forced a tow to be shortened (if the duration of a tow was at least 10 minutes, it was considered valid). Computer software was used to record data from the net monitoring gear (i.e., wingspread and headrope height) as well as a continuous GPS stream during each tow. On occasions when the monitoring gear failed, the trawl geometry was assumed to follow cruise averages and beginning and ending tow coordinates were recorded by hand from the vessel’s GPS system.

Task 2 – Synthesize data for single species analyses

Once onboard, the catch from each tow was sorted and measured by species and size‐class if distinct classes within a particular species were evident. A subsample of each species/size‐class was further processed for individual weight determination, stomach contents, ageing, and determination of sex and maturity stage. In addition to these biological data, water temperature, salinity, and dissolved oxygen readings from both the surface and bottom were recorded at each sampling location.

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Single‐species assessment models typically require information on (among others) age‐, length‐, and weight‐structure, sex ratio, and maturity stage. Data were synthesized to characterize annual length‐ and age‐frequency distributions. Analytical computer programs to characterize each of the assessment‐related data elements (length, weight, age, sex, maturity) were developed to allow for the summarization of these characteristics across a variety of spatial and temporal scales (e.g., by year, season, or region of the bay) for each species.

Task 3 – Quantify trophic interactions for multispecies analyses

In addition to the population‐level information described under Task 2, multispecies assessment models require information on predator‐prey interactions across broad seasonal and spatial scales. In general, these procedures involve examining the stomach contents of predators and identifying each prey item to the lowest possible taxonomic level. As such, stomach samples were collected and preserved in the field and were processed at VIMS following standard diet analysis procedures (Hyslop 1980). Several diet indices were calculated to identify the main prey types for each species sampled by the ChesMMAP Survey: %weight, %number, and %frequency‐of‐occurrence (only %weight analyses are presented in this report).

These indices were coupled with the information generated from Task 2 and age‐, length‐, and sex‐specific diet characterizations were developed for each species. Efforts also focused on characterizing spatial and temporal variability in these diets.

As noted above, several diet index values were calculated to identify the main prey in the diet of predators in the mainstem Chesapeake Bay. Since trawl collections essentially yield a cluster of fish at each sampling location, these indices were calculated using a cluster sampling estimator (Buckel et al. 1999).

Specifically, the contribution of each prey type to the diet (%Qk, where Qk is any of the aforementioned index types) is given by:

n

%Qk =

∑M q i =1 n

i ik

∑M i =1

, (1) i

where

wik * 100 , wi

and where n is the number of trawls containing the predator of interest, Mi is the number of that predator collected at sampling site i, wi is the total weight of all prey items encountered in the stomachs of that predator collected from sampling location i, and wik is the total weight of prey type k in those stomachs.

qik =

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Task 4 – Estimate abundance

Time‐series of relative abundance information can easily be generated from the basic catch data of a monitoring survey. For each species sampled by the ChesMMAP Survey, a variety of relative abundance trends can be generated according to year, season, and location within Chesapeake Bay. Absolute abundance estimates can be generated for each species by combining relative abundance data with area swept by the trawl and gear efficiency information. Area swept was calculated for each tow by multiplying tow distance (provided by GPS) by average wingspread (provided by net monitoring gear). Gear efficiency estimates, gained through hydroacoustic data collection as described in previous project reports, have been estimated for two species common in ChesMMAP catches (Atlantic croaker and white perch) and results are currently under review for publication in the primary literature.

While minimum total or absolute abundance estimates are important for certain bioenergetic and ecosystem level analyses, fishery assessments typically depend upon relative abundance indices from surveys as important indicators of abundance. Therefore, considerable effort was expended this year to develop relative abundance indices for species inhabiting Chesapeake Bay using ChesMMAP data. Analyses were undertaken to determine the most appropriate calculation methods to produce such indices. The relative abundance indices presented in this report should be considered preliminary as further analyses are planned.

Abundance index analyses conducted to date include: 1. Creating 3‐D figures (included in Results) for each species which visually display differences in catch rates by year, month, region, and depth stratum.

2. Constructing general linear models (GLM) (not shown in this report) to identify significant differences in catch rates for each species among months, regions, and depth strata. The purpose of these first two analyses was to determine the geographic and temporal maximum catch rates for each species to define which data to use and which to exclude in developing indices.

3. Using the limiting parameters described above, developing annual geometric mean catch per area swept indices for each species for all ages combined, according to the formula:

I

where:

exp

1

1

I = Index C = number or biomass caught at a station a = area swept at a station i = ith stratum n = number of strata w = stratum weight

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2

Arithmetic means for total abundance (i.e., across all age‐classes) are also presented for comparative purposes.

4. Three different methods were explored for developing age‐specific abundance indices.

These were: A. Age proportion. With this method, considered the least reliable, the overall index developed above was partitioned according to the proportion of specimens in each age class, according to the formula:

B.

C.

D.

E.

(3)

where: Iage = Age‐specific index

I = Overall index as per equation 1

a = number of specimens at age collected by the survey

A = total number of specimens collected by the survey

Expansion of data collected from specimens subsampled for ageing. As described under Task 2, at each station a subsample of specimens of each species are dissected for later age determination. During data post processing, expansion factors are calculated and included in the ChesMMAP data base such that each of these subsampled specimens represents a a number of individuals in the total catch. In effect, using these expansion factors yields age‐frequency information at the catch level. For example, if a total of 20 individuals are captured at a station and 5 of them are dissected for age determination, each fish subsampled for ageing is assigned an expansion factor of 4, meaning that each of these subsampled fish represents 4 fish in the total catch. Age‐specific indices were calculated with the same formulae as used for the overall abundance, but using only the appropriately (age‐0,1,2, etc.) aged fish and the appropriate expansion factors at each tow.

Age‐length key. An alternative method (suggested to the researchers during a recent peer review process of the NEAMAP program) was to partition the length‐ frequencies at each station by age‐class according to an age‐length key calculated from samples captured and aged during the entire cruise. This metric was then used as previously described.

These age‐specific abundance indices were calculated for the youngest and/or most abundant one‐to‐three age classes but could be determined for each age‐ class captured. For a small number of species, hard‐part samples have not been completely analyzed for the most recent year (or in an even smaller number of cases, for any years).

For this report, results from all three methods are presented. In the future, we will evaluate which of the methods is most appropriate. The factors which will be used in the evaluation include consistency with other measures of abundance, measures of variability, and internal consistency. Further, we will

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evaluate the relative strengths and weaknesses of each method. For example, a weakness of the sub‐sample expansion method is that it depends heavily on a relatively small number of aged specimens at each station; likewise the age‐ length key method can arbitrarily re‐assign aged specimens to a different age class based solely on length.

5. As mentioned, most indices presented in this report were calculated using geometric means. Many surveys use geometric means for calculation of survey indices as these data have often been shown to be log‐normally distributed (Pennington and Stromme 1998). However, other distributions and data transformations (e.g. delta distribution, gamma distribution) have been shown to be more appropriate for some survey data. In the future we plan to examine the distributions of ChesMMAP abundance data on a species‐specific basis.

Results

Task 1 – Conduct Research Cruises

Throughout the first six years of sampling, the number of fish collected each year by the ChesMMAP survey was fairly consistent and ranged from approximately 31,000 (in 2003 and 2007) to 48,000 (in 2004 – Table 1). This number decreased to about 26,000 in 2008 due in large part to a decline in the catch of Atlantic croaker from an average (2002‐2007) of 14,300 to only 6,300. Each year, between 3,900 and 6,000 pairs of otoliths have been collected, the majority of which have been processed for age determination. Similar numbers of stomachs have been collected and processed for diet composition information annually.

Table 1. The number of specimens collected, measured and processed for age determination and diet composition information from ChesMMAP, 2002 – 2008.

Year Fish Fish Otoliths Otoliths Stomachs Stomachs collected measured collected processed collected processed 2002 32,019 23,605 5,487 4,481 4,559 3,006 2003 30,924 20,828 3,913 3,046 3,250 2,294 2004 47,622 31,245 5,169 4,283 4,272 3,164 2005 45,204 36,909 6,065 4,999 5,067 3,205 2006 43,957 31,243 5,413 4,221 4,402 2,855 2007 30,893 22,124 4,282 3,252 3,669 2,828 2008 26,299 19,594 4,204 2,611 3,674 3,397

Tasks 2‐4 – Data Summaries

The data summaries in this report represent a subset of the biological and ecological analyses which could be calculated from the ChesMMAP data set. For those species which are well‐ sampled by the survey, overall and age‐specific abundance estimates are presented.

Abundance is presented both in units of minimum trawlable abundance (as in previous

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ChesMMAP reports) and in relative index units using abundance per area swept. Relative abundance index calculations were based on limiting the data used for each species to the months, regions, and depth strata of maximum abundance over all years (Table 2). Length‐ frequency, age‐frequency (for those species for which ageing has been completed) and overall diet summaries are also presented. Some analyses (e.g. sex ratios, length‐weight relationships, growth equations) presented in previous project reports are not included. It is assumed that, when needed, assessment scientists and managers will require specific analyses of these data types which could not be fully anticipated in this report. Therefore, only those general data summaries of the most universal possible use are included. The profiles that follow are organized first by species and then by type of analysis (‘Task’). Each Task element (single‐ species stock parameter summarizations, trophic interaction summaries, and estimates of abundance) is included but is not labeled with a Task number and is not necessarily shown in Task number order (note also that not all analysis types are available for all species).

For each species, the following data summaries are presented (note that some data/analyses may not be available for all species):

1) Minimum trawlable abundance, in numbers and biomass, by year, month, and region within the bay.

2) Comparison of catch rates by year, cruise (i.e., month), region, and depth stratum.

3) A table containing relative abundance indices. Overall and age‐specific (where appropriate) indices are presented. For age‐specific indices, results from three different calculation methods are shown.

4) Figures presenting overall area‐swept abundance indices by number and biomass, calculated using both geometric and arithmetic means.

5) Figures presenting age‐specific geometric mean abundance indices, in numbers and biomass, from three different calculation methods.

6) A series of GIS figures showing total abundance at each sampling site overlaid on the survey depth strata, for each year and cruise.

7) Length‐frequency data by year.

8) Age‐frequency distributions by year (for those species where appreciable numbers have been captured and otoliths have been processed).

9) Diet analyses by weight, using all data collected and analyzed 2002‐2008.

Species Data Summaries

Atlantic Croaker (Micropogonias undulatus)

Abundance: Atlantic croaker is among the most abundant species in ChesMMAP survey catches, especially during the May and July cruises each year, with minimum trawlable number (MTN) estimates typically reaching 30‐40 million and minimum trawlable biomass (MTB) between 5‐10 million kg (Figure 1). The majority of fish are captured in Regions 4 and 5 (Virginia). Catches decline in September and November as this summer resident species leaves bay waters. No inter‐annual trend in abundance was apparent during first six years of sampling, but abundance 9

in 2008 decreased about 50%. Croaker are typically about four times more abundant in mid‐ depth (30’ – 50’) and deep sampling sites (>50’) than at shallow (10’ – 30’) stations (Figure 2 and Figures 5‐11).

Relative abundance indices for all ages combined calculated as geometric and arithmetic means follow similar trends, both in numbers and biomass (Figure 3, Table 3) and all indices reflect low abundance in 2008.

Age specific geometric mean abundance indices using the Expanded and Age‐Length methods generally follow similar trends (with the exception of age‐0 indices in 2008 where the Expanded index increased while the Age‐Length index declined). The scales of the indices from the two calculation methods are different, however, with the Age‐Length methodology yielding higher values (Figure 4, Table 3). It is notable that low abundance of age‐0 fish in 2007 was followed by very low abundance of age‐1s in 2008 and, as age‐1 specimens generally constitute a large proportion of the overall catch, this contributed to the low overall abundance indices for this species. With the exception of the Age‐Length numerical index, estimates of the 2008 year‐ class were higher than for 2007 so it will be worth watching whether these fish contribute to a higher age‐1 (and overall) index in 2009.

Length and Age: Specimens between 14mm and 499mm in length (Figure 12) and between age 0 and 15 (Figure 13) appear in survey data; most individuals range between 150mm and 350mm and ages 1‐5. Croaker to age 8 are not uncommon for this survey. During 2008, program personnel attended an Atlantic croaker ageing workshop sponsored by the Atlantic States Marine Fisheries Commission. The consensus report from that workshop set a birth date of 1 January each year, as that date is the approximate mid‐point of spawning in the southern portion (i.e., south of Cape Hatteras) of the species’ range. Spawning north of Hatteras, including Virginia’s waters, occurs several months earlier, and is often complete by early December. As a result, all croaker ages in the ChesMMAP data base were adjusted down one year and it is now possible to capture age‐negative 1 fish in the survey. This occurs when fish spawned in late summer and autumn of a given year are collected during the September or November cruises of that year. Those fish are not considered age‐0 (or young‐of‐the year) until that upcoming January, so to place them in the correct year‐class, they are assigned an age‐ negative 1.

The length distribution of this species changes considerably year‐to‐year as year‐ classes of either extremely high or extremely low abundance move through the stock. For example, a highly abundant 2002 year class seen as a peak in the length‐frequency histograms between 2003 and 2007 and as a distinctly abundant year class in the age‐frequency figures even into 2008. There appears to be evidence of mildly to highly successful year classes in 2003, 2004, and 2005 so the stock should remain plentiful in coming years. The fact that the pattern of year class abundance remains relatively constant from year to year (i.e. that relative peaks and valleys tend to increment each year) indicates both that the survey gear fishes consistently over time and that laboratory ageing methods do not vary.

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Diet: Miscellaneous polychaetes (22.4%) represent the largest single prey type in the diet of Atlantic croaker and all worms combined (39.4%) represent the largest taxonomic group.

Unidentifiable material (16.7% ‐ likely constituted largely of worms and soft‐bodied molluscs) is the second largest single prey type. Molluscs (15.9%, mostly bivalves) and crustaceans (15.6%, with the largest prey type being mysids) were nearly equal in importance. It is notable that, in the habitats sampled by the survey, blue crabs did not constitute a significant prey type (defined here as 1% of the diet). Six other categories of prey constituted a total of 12.2% of the diet, by weight (Figure 14).

Figure 1. Atlantic croaker minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay 2002‐2008.

Figure 2. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for Atlantic croaker.

Table 3. Abundance indices (numbers and biomass) for Atlantic croaker, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 3. Overall abundance indices (number and biomass) for Atlantic croaker based on geometric (A) and arithmetic (B) means.

Figure 4. Atlantic croaker age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐0 (B), age‐1 (C) and age‐2 (D) specimens.

Figures 5 – 11. Abundance (kg per hectare swept) of Atlantic croaker in Chesapeake Bay, 2002‐ 2008.

Figure 12. Atlantic croaker length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 13. Atlantic croaker age‐structure in Chesapeake Bay, 2002‐2008.

Figure 14. Atlantic croaker diet in Chesapeake Bay, 2002‐2008 combined.

Black Seabass (Centropristis striata)

Abundance: The ChesMMAP survey gear and sampling methodology are not considered particularly effective for this structure‐oriented species (locations of known complex bottom structures and other ‘hangs’ are purposely avoided). However, enough individuals are captured for a certain amount of information to be extracted from survey samples. Catches are typically highest during the July, September and November cruises and are concentrated in Regions 4 11

and 5 but are not uncommon in Region 3. Significant differences in catch rates among depth strata were not observed (Figures 15‐16, 19‐25).

Overall relative abundance indices expressed either in numbers or biomass and calculated both at geometric and arithmetic means exhibit consistent inter‐annual patterns. While 2008 abundance was estimated as the lowest value in the time series, it is difficult to discern a time series trend (Figure 17). As catch rates for this species are low and inconsistent, confidence limits on the abundance estimates are broad.

Age‐specific geometric mean abundance indices are presented for both age‐0 and age‐1. Both the Expanded and Age‐Length indices indicate that after hovering at very low levels for the first four survey years, the Age‐0 index increased in 2006 and again in 2007 and then remained at a relatively high level in 2008. Age‐1 indices exhibit a generally downward trend throughout the survey years and interestingly do not reflect (given a one year lag) the higher abundance in the Age‐0 indices. It must be stressed again that catch rates for this species are low and abundance indices generated from these survey data may not be reliable.

Length and Age: Specimens captured in the survey tend to be relatively small (<250mm) and young (age‐0 and age‐1) though individuals up to 270mm have been sampled (Figure 26).

Ageing of samples from earlier survey years was completed in 2008 and revealed that in most years the survey catches are dominated by age‐1 specimens, though in the past two survey years the number of age‐0 specimens has increased (Figure 27). Comparisons of abundance estimates between this and other surveys has not yet been accomplished but may give insight as to the reliability of data from this and other surveys.

Diet: Though the sample size is relatively small (154 specimens, 97 clusters of specimens) and the size range of samples is limited, the diet data is probably the most valuable ChesMMAP contribution for this species. Crustaceans (68.9%), dominated by mysids (19.7%) and mud crabs (10.5%), contribute the highest portion of the diet, by weight. Fish constitute 7.8% of the diet with bay anchovy (2.4%) the largest component among identifiable species. A variety of worms (6.1%) molluscs (4.9%) and other less prominent or unidentifiable taxa constitute the remainder of the diet (Figure 28).

Figure 15. Black sea bass minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay 2002‐2008.

Figure 16. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for black seabass.

Table 4. Abundance indices (number and biomass) for black seabass, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

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Figure 17. Abundance indices (number and biomass) for black seabass based on geometric (A) and arithmetic (B) means.

Figure 18. Black seabass age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐0 (B), age‐1 (C) specimens.

Figures 19 – 25. Abundance (kg per hectare swept) of black seabass in Chesapeake Bay, 2002‐ 2008.

Figure 26. Black sea bass length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 27. Black sea bass age‐structure in Chesapeake Bay, 2002‐2008.

Figure 28. Black sea bass diet in Chesapeake Bay, 2002‐2008 combined.

Bluefish (Pomatomus saltatrix)

Abundance: Due to the fast‐swimming and pelagic nature of bluefish, this species also is not considered to be well sampled by ChesMMAP, though some useful assessment‐related information can be generated from these survey data (Figure 29). When captured, typically between one and five specimens occur in a tow, though as many as 42 have been collected in a single sampling event. Bluefish are usually captured in either the shallow (10’‐30’) or mid‐depth (30’‐50’) strata. Catches are typically highest late in the year, presumably as the young‐of‐the year fish are moving into deeper waters in preparation for outmigration from the bay (Figure 30). Abundance is normally highest in Regions 4 and 5 but notable exceptions occur such as a single capture of 26 specimens in Region 1 during the September 2008 cruise (Figures 33‐39).

Abundance indices for all ages of bluefish combined have varied without trend over the survey years (Figure 31). Patterns between indices by number and weight as well as between geometric and arithmetic calculation methods are nearly identical. The exception is that the arithmetic indices increased in 2008 while those calculated by geometric mean decreased. This is likely due to the single large catch of individuals that occurred in Region 1 in September as the geometric mean would moderate such an event and the arithmetic mean would not.

Specific estimates of abundance for age‐0 and age‐1 specimens also tend to vary without trend and there is good agreement between the Expanded and Age‐Length calculation methods.

Confidence limits tend to be narrower for the Age‐Length indices than for the Expanded ones, most likely due to the spotty nature of survey captures for bluefish (Figure 32). Future work must include comparison of ChesMMAP indices to those generated by other surveys.

Length and Age: Most individuals sampled in the survey are less than 350mm and, due to the number of small number of specimens captured and protracted spawning season of this 13

species, it is difficult to differentiate cohorts in length frequencies (Figure 40). Nearly all ChesMMAP bluefish are either age‐0 or age‐1 and in most years the majority of specimens captured are age‐0 (Figure 41).

Diet: Diet data presented here are consistent with previous studies in showing that bluefish are highly piscivorous (Figure 42). For the 224 specimens examined, which represent 127 clusters, bay anchovy constitute 44.4% of the diet of sampled specimens, Atlantic menhaden 11.9%, and all fish species together represent 83.6%. Crustaceans (mainly mysids) represent 13.7% and Loligo squid 1.8% of the diet of observed fish.

Figure 29. Bluefish minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

Figure 30. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for bluefish.

Table 5. Abundance indices (number and biomass) for bluefish, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 31. Abundance indices (number and biomass) for bluefish based on geometric (A) and arithmetic (B) means.

Figure 32. Bluefish age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐0 (B), age‐1 (C) specimens.

Figures 33 – 39. Abundance (kg per hectare swept) of bluefish in Chesapeake Bay, 2002‐2008.

Figure 40. Bluefish length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 41. Bluefish age‐structure in Chesapeake Bay, 2002‐2008.

Figure 42. Bluefish diet in Chesapeake Bay, 2002‐2008 combined.

Butterfish (Peprilus triacanthus)

Abundance: Butterfish abundance follows a generally predictable annual pattern, building from near‐zero during March, increasing abundance (albeit low) through the spring and summer, and reaching a maximum generally during the September and November cruises (Figure 43). Most butterfish are captured in Regions 4 and 5 (Virginia) but the species is common in the northern regions (2 and 3) during some cruises (assumed to follow patterns of salinity). Catches are usually highest in the mid‐depth (30’‐50’) strata (Figures 44, 46‐52).

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Abundance indices (geometric and arithmetic, numbers and biomass) increased between 2002 and 2004, decreased through 2007 then turned upward slightly in 2008 (Figure 45, Table 6).

Age‐specific indices have not yet been calculated for this species (see next section).

Length and Age: This program (and others) has found butterfish extremely difficult to age. We are still investigating methods to obtain accurate age determinations from otolith samples.

Yearly length frequency diagrams (Figure 53) appear to reveal at least two year classes of varying strength present in the Chesapeake Bay fish during any given year, however this will require further analysis. Ageing has been accomplished for specimens captured from NMFS surveys (Kawahara, 1978) so it may be possible to estimate ChesMMAP ages from length‐age keys.

Diet: Analyses of butterfish stomachs from early program years revealed a high percentage of generally unidentifiable gelatinous zooplankton and other unidentifiable items. It was determined that further analyses of butterfish diets was not an efficient use of resources and the decision was made to discontinue preservation and analysis of butterfish stomachs.

Figure 43. Butterfish minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

Figure 44. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for butterfish.

Table 6. Abundance indices (number and biomass) for butterfish, overall (calculated as geometric and arithmetic means).

Figure 45. Abundance indices (number and biomass) for butterfish based on geometric (A) and arithmetic (B) means.

Figures 46 – 52. Abundance (kg per hectare swept) of butterfish in Chesapeake Bay, 2002‐2008.

Figure 53. Butterfish length‐frequency in Chesapeake Bay, 2002‐2008.

Kingfish (Menticirrhus spp.)

The ranges of two closely related species, the northern kingfish (Menticirrhus saxatilis) and the southern kingfish (Menticirrhus americanus) overlap in Chesapeake Bay. While some specimens are easily separable, many are not. We have therefore adopted the practice of combining all of these specimens into a single category of kingfish (Menticirrhus spp.).

Abundance: After several survey years of varying without apparent trend, abundance of kingfish in the survey increased substantially in 2008 with peak abundance estimates at least twice any 15

previous estimate (Figure 54). Prior to 2008 only 11 tows had resulted in catches of 10 or more specimens, but in 2008, 8 tows in that range occurred including 5 tows with capture rates between 21 and 63 fish.

This species is generally absent in the survey during March, increases steadily through the summer and fall, and then decreases again in November as fish begin to move offshore.

Abundance is nearly always highest in Region 5 and no differences in catch rates among depth strata are apparent (Figure 55, Figures 58‐64).

Abundance indices for specimens of all ages combined, both geometric and arithmetic means for both numbers and biomass, show consistent year‐to‐year estimates with 2008 being the highest year in the time series (Figure 56, Table 7). Prior to 2008, age‐specific abundance estimates vary without apparent trend. There is generally good (though not perfect) agreement within age classes between calculation methods and between estimates by number or by weight (Figure 57). As this species is of lesser management interest in Virginia, ageing of 2008 specimens has not yet been completed.

Length and Age: Due to the relatively small number of specimens captured during any particular year, it is difficult to interpret length frequencies, though at least two cohorts are apparent in some years (Figure 65). Specimens between ages 0 and 7 have been captured with most being age‐4 or less. Year‐classes of high (e.g. 2002) and low (e.g. 2004) abundance do seem to track through the stock from year to year, which indicates consistent survey sampling and otolith analysis.

Diet: The largest taxa of prey items in kingfish stomachs are crustaceans (41.0%), primarily small shrimps and crabs. Molluscs and worms constitute 33.9% and 10.6% of the diet, respectively, with fish comprising an additional 6.1% (Figure 67).

Figure 54. Kingfish minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

Figure 55. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for kingfish.

Table 7. Abundance indices (number and biomass) for kingfish, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 56. Abundance indices (number and biomass) for kingfish based on geometric (A) and arithmetic (B) means.

Figure 57. Kingfish age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐0 (B), age‐1 (C) and age‐2 (D) specimens.

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Figures 58 – 64. Abundance (kg per hectare swept) of kingfish in Chesapeake Bay, 2002‐2008.

Figure 65. Kingfish length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 66. Kingfish age‐structure in Chesapeake Bay, 2002‐2007.

Figure 67. Kingfish diet in Chesapeake Bay, 2002‐2008 combined.

Northern Puffer (Sphoeroides maculatus)

Abundance: Typical patterns of abundance for this species in the survey are for minimal numbers in spring and early summer, and a peak in abundance during the November cruise, perhaps as the summer residents are migrating toward offshore wintering grounds. Catches are consistently highest in Regions 4 and 5, though the species is common into Region 3. Most specimens are captured in the shallow and mid‐depth strata (Figures 68‐69, 71‐77). As catches in the survey are spotty, estimates of abundance for this species are of unknown reliability.

Relative abundance indices from survey data have varied without trend since 2002. Indices calculated as both geometric and arithmetic means, based on both numbers and biomass, tend toward good agreement (Figure 70, Table 8). Ageing of preserved hard parts has not yet been attempted for this species, so age‐specific indices are not available.

Length and Age: Specimens between approximately 50mm and 270mm have been captured, though most individuals measured between 100mm and 250mm. The length composition varies year to year likely as a result of varying year‐classes entering and leaving the bay stock (Figure 78). However, as this is not a high priority species, ageing has not been completed.

Diet: Crustaceans (40.0%), primarily small crab species, molluscs (18.4%), and worms (12.1%), constitute the majority of identifiable items in the stomachs of this species. Unidentifiable material constitutes a significant (13.8%) portion of prey items examined (Figure 79).

Figure 68. Northern puffer minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

Figure 69. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for northern puffer.

Table 8. Abundance indices (number and biomass) for northern puffer, overall (calculated as geometric and arithmetic means).

Figure 70. Abundance indices (number and biomass) for northern puffer based on geometric (A) and arithmetic (B) means.

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Figures 71‐77. Abundance (kg per hectare swept) of northern puffer in Chesapeake Bay, 2002‐ 2008.

Figure 78. Northern puffer length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 79. Northern puffer diet in Chesapeake Bay, 2002‐2008 combined.

Scup (Stenotomus chrysops)

Abundance: Survey catches of scup are typically rare during spring through early summer and nearly always reach a peak in September before declining again in November as fish leave bay waters (Figure 80, Figures 84‐90). The species is most abundant in Region 5 and is rarely captured north of Region 4. It is important to note that 2007 data are limited due to cancellation of the September cruise. Scup are typically most abundant in shallow strata (10’‐ 30’) and mid‐depth strata (30’‐50’) and are rarely captured in waters over 50’ (Figure 81).

Discerning trends over the time series is problematic due to the difficulty in interpreting 2007 data when the September cruise was cancelled resulting from a budget shortfall. Geometric mean indices for both number and biomass indicate relatively high abundance in 2007 while arithmetic mean indices show a downward trend since a time series peak in 2005. All indices however show a time series low abundance in 2008 (Figure 82, Table 9).

Ageing of 2008 specimens has not been completed so age‐specific indices are not yet available for 2008. For 2002‐2007 however, there is good agreement among indices calculated using the Expanded and Age‐Length methods for both number and biomass within age groups. No apparent trend is observed for age‐class specific indices except that peak time‐series abundance was seen in either 2004 or 2005 (Figure 83).

Length and Age: Most specimens captured in the survey are less than 200mm and at least two year classes are apparent in length data (Figure 91). A backlog of otoliths collected in previous survey years was completed. Nearly all specimens captured are either age‐0 or age‐1 so it is difficult to discern whether year‐class abundance can be followed in age frequency figures (Figure 92).

Diet: Worm species constitute a near majority (49.8%) of identifiable items in scup stomachs (Figure 93) but unidentifiable prey (likely largely constituted of worms and other soft‐bodied prey) also make up a large portion (24.7%). Crustaceans (15.6%) are also a major prey source, consisting primarily of mysids and skeleton shrimp.

Figure 80. Scup minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

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Figure 81. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for scup.

Table 9. Abundance indices (number and biomass) for scup, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 82. Abundance indices (number and biomass) for scup based on geometric (A) and arithmetic (B) means.

Figure 83. Scup age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐0 (B), age‐1 (C) specimens.

Figures 84 –90. Abundance (kg per hectare swept) of scup in Chesapeake Bay, 2002‐2007.

Figure 91. Scup length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 92. Scup age‐structure in Chesapeake Bay, 2002‐2007.

Figure 93. Scup diet in Chesapeake Bay, 2002‐2008 combined.

Spot (Leiostomus xanthurus)

Abundance: Spot are typically among the most abundant species in the survey during all cruises except March. Likewise the species is well distributed throughout the bay, though concentrations are highest in Regions 4 and 5. They are well distributed across all depth strata as well (Figures 94‐95). The species appears to invade the bay earlier and remain abundant later in the fall during recent years compared to early survey years. Whether this is environmentally related or a result of other factors is unknown.

Abundances (all ages combined) over the times series vary considerably year to year and though no trend is apparent, abundance decreased in 2008. Patterns between geometric and arithmetic means and expressed in numbers and biomass are consistent (Figure 96).

With the exception of the Age‐Length biomass index, age‐0 indices show peak recruitment in 2003 and a generally downward trend since. The Age‐Length biomass index exhibits a higher peak in 2007. Age‐1 indices are consistent in measuring peak abundance in 2007 with all other years being relatively flat.

Length and Age: Individuals between 100mm and 250mm are most common in the survey, with a smaller number of specimens up to 300mm occasionally captured (Figure 105). The largest

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individuals are most often captured in Regions 2 or 3. Nearly all fish in the survey are either age‐0 or age‐1 with the oldest fish captured at age‐4 (Figure 106).

Diet: Considerable progress was made in 2008 in analysis of a backlog of preserved spot stomachs. Not surprisingly, the largest single prey type is unidentified material (36.9%) followed by worms (32.6%) which for the most part were not identifiable to specific taxa, molluscs (13.3%), and crustaceans (8.2%) (Figure 107).

Figure 94. Spot minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

Figure 95. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for spot.

Table 10. Abundance indices (number and biomass) for spot, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 96. Abundance indices (number and biomass) for spot based on geometric (A) and arithmetic (B) means.

Figure 97. Spot age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐0 (B), age‐1 (C) specimens.

Figures 98 – 104. Abundance (kg per hectare swept) of spot in Chesapeake Bay, 2002‐2008.

Figure 105. Spot length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 106. Spot age‐structure in Chesapeake Bay, 2002‐2008.

Figure 107. Spot diet in Chesapeake Bay, 2002‐2008 combined.

Striped Bass (Morone saxatilis)

Abundance: Intra‐annual patterns of abundance for striped bass typically follow a similar pattern. Large numbers of spawning migrants are captured during the March cruise, followed by lower numbers in May as the spawners leave the bay. Lower catches occur in July and September, and higher numbers are encountered again in November as fish school before leaving the bay for offshore wintering grounds. Most striped bass are captured in Regions 1 – 3 (Maryland waters) but the species occurs regularly in samples from all bay locations. In March, catches are high in all depth strata, but in other survey months catch rates are highest in waters less than 50’ (Figures 108‐109, Figures 114‐120).

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Two sets of abundance indices have been calculated for this species: one using data from the March cruise which assesses abundance of the spring spawning stock, and one using data from November which characterizes the number of summer residents as they school together in the fall.

Geometric mean March abundance, with all ages combined, expressed both as numbers and biomass, show peaks in 2004 and 2008. Arithmetic mean indices are somewhat more difficult to interpret but seem to show peak abundances in 2005 and 2008 (Figure 110, Table 11).

Potentially meaningful age‐specific indices could be calculated to age 5 or 6 but for purposes of brevity only those for ages 1‐3 are presented here (Figure 111). Generally, these indices exhibit large year to year variations with trends difficult to discern.

Patterns in November indices for all ages combined are difficult to interpret. The indices vary widely using either geometric or arithmetic means, without discernable trend. Geometric mean indices for number and biomass generally follow similar inter‐annual patterns, as do those using arithmetic means, but patterns between the two calculation methodologies do not track with one another (Figure 112, Table 12). Likewise no obvious trend is apparent in age‐specific indices, though the 2003 year class is measured in relatively high abundance as age‐1, age‐2 and age‐3. Within an age class patterns of abundance are generally consistent whether measured using the Expanded calculation or the Age‐Length indices, for both numbers and biomass (Figure 113).

Length and Age: Most specimens captured in the survey are about 600mm or less (ages 1 – 7).

The largest individuals approach 1000mm and are captured during spring spawning. Due to the relatively long‐lived nature of this species, the varying life history scenarios for different portions of the stock and associated variable growth rates, along with variable young‐of‐year recruitment, it is difficult to differentiate year‐classes within length‐frequency histograms (Figure 121). However, age distribution figures (Figure 122) readily reveal year‐class strength (high peaks during one year tend to follow into succeeding years, as do low abundances) and this phenomenon is being used in attempting to validate results of young‐of‐year seine surveys.

The oldest specimen yet sampled by the survey, at age‐20 (1988 year class), was captured in 2008.

Diet: Results of diet analyses from this study differ appreciably from previous studies using specimens from Chesapeake Bay (Figure 123). While fish comprise the largest taxonomic group in the diet (42.3%), this survey consistently finds that bay anchovy contributes the highest proportion by weight (16.8%) among fishes, with Atlantic menhaden a distant second (9.5%).

Further, crustaceans such as mysids and amphipods constitute 18.3% and 5.5% respectively, a sharp contrast to previous studies; and worms make up another 15.7%. These differences from previous diet studies are likely the result both of sampling methodological differences (the broad temporal and geographic scale of ChesMMAP as well as the trawl gear used) and analytical/mathematical differences in calculating percentages in the diet. In brief, this study calculates fish diets using cluster‐sampling theory and analytical methods whereas previous 21

studies are thought to have used the assumption of simple random sampling of fish. This is discussed thoroughly in a paper recently submitted for publication in the primary literature.

Figure 108. Striped bass minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

Figure 109. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for striped bass.

Table 11. Abundance indices (number and biomass) for striped bass (March), overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 110. Abundance indices (number and biomass) for striped bass (March) based on geometric (A) and arithmetic (B) means.

Figure 111. Striped bass (March) age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐1 (B), age‐2 (C) and age‐3 (D) specimens.

Table 12. Abundance indices (number and biomass) for striped bass (November), overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 112. Abundance indices (number and biomass) for striped bass (November) based on geometric (A) and arithmetic (B) means.

Figure 113. Striped bass (November) age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐1 (B), age‐2 (C) and age‐3 (D) specimens.

Figures 114 – 120. Abundance (kg per hectare swept) of striped bass in Chesapeake Bay, 2002‐ 2007.

Figure 121. Striped bass length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 122. Striped bass age‐structure in Chesapeake Bay, 2002‐2008.

Figure 123. Striped bass diet in Chesapeake Bay, 2002‐2008 combined.

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Summer Flounder (Paralichthys dentatus)

Abundance: The typical intra‐annual pattern of numerical abundance for summer flounder shows catches increasing monthly throughout the sample year, with highest catches in September and/or November. Biomass estimates however, tend to reach a high level in May and remain relatively constant for the rest of the year (Figure 124). This interesting pattern likely results as more numerous but smaller individuals become available to the survey as the sampling season progresses. Summer flounder are most abundant in Regions 4 and 5 but are common in Regions 2 and 3 as well. A slightly higher catch rate is exhibited for mid‐depth (30’ – 50’) and deep (>50’) stations than in shallow (10’ – 30’) waters (Figure 125). The highest catches of summer flounder often occur along the eastern portions of Regions 4 and 5 but this is not an absolute (Figures 128‐134).

Abundance indices for all ages combined have varied considerably over the time series without an overall trend, whether calculated as geometric or arithmetic means, or expressed as numbers or biomass (Figure 126, Table 13). Age‐specific indices follow consistent patterns within an age‐class but no obvious visual correlation is apparent among age‐classes (Figure 127).

Length and Age: Fish which measure between approximately 200mm and 500mm are most prevalent in survey samples though fish as large as 760mm have been captured (Figure 135). In several years a large number of fish under 300mm (likely age‐0) can be differentiated in length‐ frequency graphs. Most fish in the survey are age‐5 and under and the oldest fish yet captured are three specimens at age‐12. In age classes older than age‐2 it appears to be more difficult, compared to other species, to follow abundance trends of particular year classes in successive years (Figure 136). This could be the result of differential migration patterns among different sized fish or of fishery preferences and/or regulations.

Diet: Fish comprise a slight majority (50.7%) of summer flounder diets in the survey, with the primary prey being bay anchovy (17.7%), weakfish (9.6%), and spot (7.4%) (Figure 137).

Crustaceans constitute just slightly less of the diet (45.4%) with the main prey types being mysids (23.1%), mantis shrimp (11.0%), and sand shrimp (6.9%). The high prevalence of fish in summer flounder stomachs, especially for larger individuals, leads to the conclusion that this species should be considered a top predator in Chesapeake Bay along with striped bass, bluefish, and weakfish (Latour et al. 2008).

Figure 124. Summer flounder minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

Figure 125. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for summer flounder.

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Table 13. Abundance indices (number and biomass) for summer flounder, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 126. Abundance indices (number and biomass) for summer flounder based on geometric (A) and arithmetic (B) means.

Figure 127. Summer flounder age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐0 (B), age‐1 (C) and age‐2 (D) specimens.

Figures 128 – 134. Abundance (kg per hectare swept) of summer flounder in Chesapeake Bay, 2002‐2008.

Figure 135. Summer flounder length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 136. Summer flounder age‐structure in Chesapeake Bay, 2002‐2008.

Figure 137. Summer flounder diet in Chesapeake Bay, 2002‐2008 combined.

Weakfish (Cynoscion regalis)

Abundance: Weakfish is among the most abundant species in survey samples over most seasons and locations. Catches are typically low in March but by May fish have begun to migrate into the bay and remain abundant in the survey throughout the rest of the year. Peak catches are usually in September and decline somewhat in November as fish begin their late fall migration out of the bay (Figures 138‐139). After reaching a survey peak in 2004, it appears that abundance has declined over the last three years. Catches are typically higher in mid‐ depth (30’ – 50’) and deep (>50’) stations than at shallow ones (10’ – 30’) (Figures 142 – 148).

Consistent with recent coast wide trends, abundance over all age groups increased between 2002 and 2005 and has steadily declined since, reaching a time series low in 2008 (Figure 140, Table 14) . This pattern is consistent for both geometric and arithmetic indices, expressed either in numbers or biomass. The pattern of increasing abundance until 2004 or 2005 and decreasing abundance since is seen in each of the age‐specific indices as well (Figure 141).

Length and Age: Most weakfish captured by the survey are between 100mm and 350mm.

Minimum and maximum sizes found during the six survey years are 23mm and 616mm respectively (Figure 149). With only a few exceptions, most fish captured over 400mm were sampled during the first two years of the survey (2002 and 2003). Likewise, the age structure of Chesapeake Bay weakfish has compressed over the past seven years with few individuals older than age‐2 captured in recent years and almost none older than age‐3 (Figure 150).

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Diet: Fish, primarily bay anchovy (31.7%), comprise a majority (55.4%) of prey types in the weakfish diet (Figure 151). Notably, weakfish account for 4.9% of prey in the diet of weakfish, by weight. The relatively low percent of Atlantic menhaden seen in the survey stomach samples (3.3%), when compared to earlier studies, may be due to the truncation of the size range of weakfish in Chesapeake Bay. Crustaceans (38.4%) constitute most of the remainder of the diet with mysids (30.0%) contributing the largest share by a large margin.

Figure 138. Weakfish minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

Figure 139. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for weakfish.

Table 14. Abundance indices (number and biomass) for weakfish, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 140. Abundance indices (number and biomass) for weakfish based on geometric (A) and arithmetic (B) means.

Figure 141. Weakfish age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐0 (B), age‐1 (C) and age‐2 (D) specimens.

Figures 142 – 148. Abundance (kg per hectare swept) of weakfish in Chesapeake Bay, 2002‐ 2008.

Figure 149. Weakfish length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 150. Weakfish age‐structure in Chesapeake Bay, 2002‐2008.

Figure 151. Weakfish diet in Chesapeake Bay, 2002‐2008 combined.

White Perch (Morone americana)

Abundance: White perch are extremely abundant in survey samples throughout each year in Regions 1 and 2 and are common into Region 3 (Figure 152). Estimates of numerical and biomass abundance were highest in 2006 and 2007, except for a single cruise in September 2004 when a small number of very large catches resulted in the highest abundance estimates of the survey. Due to this species’ concentration in the shallow waters of Region 1 (Figures 158‐ 164), catches are highest in the shallowest strata (10’ – 30’), followed by the mid‐depth strata

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(30’ – 50’), with this species rarely seen in samples from the deepest stations (>50’) (Figure 153).

As with striped bass, indices of abundance are presented for both the spring (March) spawning population and for the fall (November) when fish again school together. For the spring spawning aggregation, overall abundance indices (geometric and arithmetic mean, for numbers and biomass) generally estimate higher abundance since 2006 than in previous survey years, though the patterns among the various indices do not follow identical inter‐annual patterns (Figure 154, Table 15). As this species is long‐lived and is not fully recruited to the survey gear until at least age‐3, age‐specific indices are difficult to interpret. Indices beyond age‐5 could be calculated from survey data but have not been presented here for the sake of brevity (Figure 155). Fall indices (all ages combined) were highest in 2004 and show a generally declining trend since (Figure 156, Table 16). Again, the age‐specific indices are difficult to interpret, though in at least some cases it does seem possible to follow abundant year classes through successive yearly indices (Figure 157).

Length and Age: All white perch of sizes greater than approximately 150mm are well sampled in the survey (Figure 165). Due to the relatively small maximum size, long life, and slow growth rates it is difficult to separate year‐classes of this species using length‐frequency. The peak of abundance in 2007 and 2008 samples was at a smaller size then during previous years. This species is not well sampled by the survey until approximately age‐2 or 3 (Figure 166), however past that age the survey appears to well represent all age classes. The species age distribution appears to be regulated by the relative success of each year‐class. Year‐class specific peaks in abundance can be easily followed during successive years in survey samples (e.g., 1993, 1996, 2000, 2003 year‐classes).

Diet: While unidentified material represents the largest single item in white perch stomachs (18.9%), crustaceans (34.8%) constitute the largest identifiable taxon with amphipods (16.6) as the primary prey, followed by mud crabs (4.7%) and copepods (4.1%). Worms (22.8%), primarily Nereis clam worms (14.6%) and other polychaetes (8.2%), are the second most abundant prey, followed by bivalve molluscs (14.7%). Notably, a small number of bay anchovy (2.2%) are present in white perch stomachs (Figure 167).

Figure 152. White perch minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002‐2008.

Figure 153. Comparison of ChesMMAP catch rates by year, cruise (month), and region (A) and year, cruise (month), and depth stratum (B) for white perch.

Table 15. Abundance indices (number and biomass) for white perch (March), overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

26

Figure 154. Abundance indices (number and biomass) for white perch (March) based on geometric (A) and arithmetic (B) means.

Figure 155. White perch (March) age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐3 (B), age‐4 (C) and age‐5 (D) specimens.

Table 16. Abundance indices (number and biomass) for white perch (November), overall (calculated as geometric and arithmetic means) and by age (geometric means only, age‐specific indices based on three calculation methods).

Figure 156. Abundance indices (number and biomass) for white perch (November) based on geometric (A) and arithmetic (B) means.

Figure 157. White perch (November age‐specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age‐length keys for age‐3 (B), age‐4 (C) and age‐5 (D) specimens.

Figures 158 – 164. Abundance (number per hectare swept) of white perch in Chesapeake Bay, 2002‐2007.

Figure 165. White perch length‐frequency in Chesapeake Bay, 2002‐2008.

Figure 166. White perch age‐structure in Chesapeake Bay, 2002‐2007.

Figure 167. White perch diet in Chesapeake Bay, 2002‐2008 combined.

Water Quality

Figures 168 – 181. Interpolated bay‐wide water temperature values 2002‐2008, surface and bottom.

Figures 182 – 195. Interpolated bay‐wide salinity values 2002‐2008, surface and bottom.

Figures 196 – 209. Interpolated bay‐wide dissolved oxygen values 2002‐2008, surface and bottom.

27

Appendix 1

Abundance data summaries for a selection of common species which are not considered as recreational species for funding and management purposes are provided in the Appendix. The species are: Blue crab – males and mature females Clearnose skate

Appendix 2

Use of Yield‐Per‐Recruit and Egg‐Per‐Recruit Models to Assess Current and Alternate Management Strategies for the Summer Flounder Recreational Fishery in Virginia: An Application of Data Collected by the ChesMMAP Trawl Survey.

Literature Cited

Buckel, J.A., D.O. Conover, N.D. Steinberg, and K.A. McKown. 1999. Impact of age‐0

bluefish (Pomatomus saltatrix) predation on age‐0 fishes in Hudson River Estuary:

evidence for density‐dependant loss of juvenile striped bass (Morone saxatilis).

Canadian Journal of Fisheries and Aquatic Sciences 56:275‐287.

Hollowed, A.B., N. Bax, R. Beamish, J. Collie, M. Fogarty, P. Livingston, J. Pope, and J.C. Rice.

2000. Are multispecies models an improvement on single‐ species models for measuring fishing impacts on marine ecosystems? ICES Journal of Marine Science 57:707‐719.

Houde, E.D., M.J. Fogarty and T.J. Miller (Convenors). 1998. STAC Workshop Report: Prospects for Multispecies Fisheries Management in Chesapeake Bay. Chesapeake Bay Program, Scientific Technical Advisory Committee.

Hyslop, E.J. 1980. Stomach content analysis – a review of methods and their

application. Journal of Fish Biology 17:411‐429.

Kawahara. S. 1978. Age and growth of butterfish, Peprilus triacanthus (Peck), in ICNAF Subarea 5 and Statistical Area 6. ICNAF Sel. Pap. 3, International Communications of Northwest Atlantic Fisheries, Dartmouth, Nova Scotia, Canada B2Y 3Y9, p. 73‐78.

Latour, R.J., J. Gartland, C.F. Bonzek, and R.A. Johnson. 2008. The trophic dynamics of summer flounder (Paralichthys dentatus) in Chesapeake Bay. Fishery Bulletin 106:47‐57.

Link, J.S. 2002a. Ecological considerations in fisheries management: when does it

matter? Fisheries 27(4):10‐17.

28

Link, J.S. 2002b. What does ecosystem‐based fisheries management mean?

Fisheries 27:18‐21.

Miller, T.J., E.D. Houde, and E.J. Watkins. 1996. STAC Workshop Report: Prospectives on Chesapeake Bay fisheries: Prospects for multispecies fisheries management and sustainability. Chesapeake Bay Program, Scientific Technical Advisory Committee.

NMFS (National Marine Fisheries Service). 1999. Ecosystem‐based fishery management. A report to Congress by the Ecosystems Principles Advisory Panel. U. S. Department of Commerce, Silver Spring, Maryland.

NOAA (National Oceanic and Atmospheric Administration). 1996. Magnuson‐Stevens Fishery Management and Conservation Act amended through 11 October 1996. NOAA Technical Memorandum NMFS‐F/SPO‐23. U. S. Department of Commerce.

Pennington, M. and T. Stromme. 1998. Surveys as a research tool for managing

dynamic stocks. Fisheries Research 37: 97‐106.

Whipple, S. J., J. S. Link, L. P. Garrison, and M. J. Fogarty. 2000. Models of predation and fishing mortality in aquatic ecosystems. Fish and Fisheries 1:22‐40.

29

Table 2. Selected Months, Regions, and Depth Strata data used for abundance indices for each species

Species

Sp. Code

Month

Region

Depth

03 05 07 09 11 01 02 03 04 05 01 02 03 Atlantic croaker

0005

black seabass

0002

bluefish

0009

butterfish

0004

kingfish sp.

0013

northern puffer

0050

scup

0001

spot

0033

striped bass (March)

0031

striped bass (November)

0031

summer flounder

0003

weakfish

0007

white perch (March)

0032

white perch (November)

0032

Additional species blue crab - ad. female

6143

blue crab - male (May-July)

6141

blue crab - male (Sept-Nov)

6141

clearnose skate

0170

30

Atlantic Croaker

31

Figure 1. Atlantic croaker minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay 2002-2008.

A

B

32

Figure 2. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for Atlantic croaker.

A

B

33

Table 3. Abundance indices (number and biomass) for Atlantic croaker, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

All Ages

Geometric Mean 2002 102.15 2003 169.67 2004 1,155.96 2005 602.01 2006 437.37 2007 670.24 2008 43.81 Arithmetic 2002 2003 2004 2005 2006 2007 2008

Age 0

LCI

Mean 3,451.42 3,068.49 8,102.31 4,969.55 4,231.14 9,511.12 969.43

By Proportion 2002 2003 2004 2005 2006 2007 2008

Index

Age 1

Age 2

By Proportion 2002 2003 2004 2005 2006 2007 2008

CV

Year

248.72 369.64 2,143.38 1,194.33 965.44 1,729.20 93.96

603.56 803.88 3,973.51 2,368.47 2,129.60 4,458.78 200.25

8.0 6.6 4.0 4.8 5.8 6.3 8.2

5,470.85 5,869.85 12,133.42 7,253.19 5,990.41 16,514.94 1,764.86

7,490.27 8,671.22 16,164.54 9,536.83 7,749.69 23,518.76 2,560.29

18.5 23.9 16.6 15.7 14.7 21.2 22.5

63.70 29.41 149.11 76.72 145.64 58.90 41.75

22.97 5.50 11.55 6.16 10.76 0.00 26.98

12.2 29.8 15.2 18.8 13.3 0.0 9.1

133.27 56.72 285.44 147.05 301.02 130.24 81.35

8.8 9.4 6.4 7.4 7.2 9.6 8.7

By Aged Sub-Sample Expansion 2002 1.70 3.88 2003 77.23 174.69 2004 0.68 1.93 2005 31.38 72.06 2006 17.10 6.55 2007 147.92 433.87 2008 3.55 1.44

7.80 393.59 4.11 163.84 42.38 1268.83 7.47

18.6 7.8 25.8 9.5 15.1 8.8 20.5

By Age-Length Key 2002 20.77 2003 101.41 2004 86.87 2005 141.44 2006 87.94 2007 287.78 2008 8.39

80.79 442.69 271.80 562.10 345.63 1971.22 26.59

8.8 6.8 5.6 6.1 6.6 7.2 9.7

By Proportion 2002 2003 2004 2005 2006 2007 2008

894.70 31.08 11.50 14.67 1200.95 245.19 245.12

By Aged Sub-Sample Expansion 2002 1.09 2.91 2003 4.18 1.47 2004 99.62 218.28 2005 3.55 8.10 2006 61.80 28.60 2007 13.55 44.82 2008 3.08 7.00

By Age-Length Key 2002 15.80 2003 20.97 2004 383.10 2005 78.97 2006 118.54 2007 135.93 2008 12.11

30.84 38.57 703.62 143.75 235.18 327.36 23.49

Geometric Mean 2002 36.53 2003 53.02 2004 347.90 2005 155.43 2006 131.50 2007 152.22 2008 11.86 Arithmetic 2002 2003 2004 2005 2006 2007 2008

Mean 711.36 594.17 2,127.74 1,100.03 1,016.09 1,598.09 107.79

6.32 9.89 476.85 17.22 132.23 143.26 14.68

22.9 22.6 7.2 15.7 9.1 15.0 16.2

59.33 70.27 1291.61 261.01 465.62 786.40 44.77

9.2 8.0 4.6 6.0 6.2 7.5 9.8

34

Index

UCI

CV

77.40 100.89 597.50 285.63 255.73 346.35 21.73

162.78 191.17 1,025.66 524.18 496.40 786.44 39.17

8.4 6.9 4.2 5.4 6.0 7.0 9.1

1,190.21 1,209.44 3,179.13 1,830.34 1,527.69 2,440.90 244.95

1,669.06 1,824.71 4,230.52 2,560.65 2,039.30 3,283.71 382.10

20.1 25.4 16.5 20.0 16.7 17.3 28.0

9.97 213.68 26.06 276.71 198.10 894.70 31.08

By Aged Sub-Sample Expansion 2002 2.30 4.06 2003 1.16 0.35 2004 1.30 2.36 2005 0.77 1.49 2006 2.32 1.44 2007 0.00 0.00 2008 2.42 3.54

6.76 2.47 3.91 2.51 3.51 0.00 5.01

13.2 30.6 15.7 18.8 12.8 0.0 9.3

52.50 9.67 20.98 20.29 40.07 22.58 22.85

7.9 10.1 6.5 5.3 5.1 11.2 6.0

By Aged Sub-Sample Expansion 2002 0.85 1.72 2003 22.13 43.23 2004 0.42 1.10 2005 10.57 20.01 2006 6.38 2.95 2007 32.93 77.84 2008 1.75 0.79

3.00 83.57 2.09 37.17 12.76 182.19 3.24

19.3 8.6 26.2 9.8 15.6 9.7 21.3

By Age-Length Key 2002 14.59 2003 36.32 2004 16.47 2005 35.47 2006 22.31 2007 70.62 2008 4.44

25.89 54.39 23.32 52.56 31.98 146.21 7.23

45.35 81.21 32.87 77.66 45.66 301.59 11.47

8.3 4.9 5.2 4.8 5.0 7.2 9.8

By Proportion 2002 2003 2004 2005 2006 2007 2008

179.20 7.19 3.58 4.00 334.78 58.64 64.93

By Aged Sub-Sample Expansion 2002 0.71 1.72 2003 2.28 0.92 2004 38.62 75.02 2005 2.02 4.09 2006 20.23 11.07 2007 5.79 15.08 2008 1.61 3.28

3.34 4.62 144.89 7.57 36.33 37.08 6.01

23.3 22.6 7.5 16.0 9.2 15.5 17.0

By Age-Length Key 2002 15.96 2003 6.40 2004 84.10 2005 18.75 2006 38.58 2007 33.71 2008 9.74

44.39 12.11 182.18 43.04 84.56 129.45 28.78

7.4 6.3 4.0 5.9 4.7 7.9 8.8

By Age-Length Key 2002 17.14 2003 3.81 2004 9.82 2005 10.87 2006 19.68 2007 6.43 2008 11.14

By Proportion 2002 2003 2004 2005 2006 2007 2008

9.97 213.68 26.06 276.71 198.10 894.70 31.08

41.20 212.17 153.83 282.21 174.58 753.68 15.09

LCI

By Proportion 2002 2003 2004 2005 2006 2007 2008

64.84 6.42 134.21 59.94 72.41 2.46 0.19

By Aged Sub-Sample Expansion 2002 5.91 11.87 2003 2.23 0.61 2004 2.87 5.97 2005 1.44 3.18 2006 6.01 3.18 2007 0.00 0.00 2008 9.00 15.73

By Age-Length Key 2002 30.18 2003 15.03 2004 77.66 2005 39.80 2006 70.20 2007 26.34 2008 21.19

By Weight UCI

30.16 6.16 14.42 14.90 28.14 12.24 16.01

20.18 1.75 37.41 14.34 19.18 0.49 0.04

26.75 8.85 123.85 28.49 57.19 66.29 16.88

Figure 3. Overall abundance indices (number and biomass) for Atlantic croaker based on geometric (A) and arithmetic (B) means.

A

B

35

Figure 4. Atlantic croaker age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-0 (B), age-1 (C) and age-2 (D) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐0

Age‐0

Age‐Length

Age‐Length

B

C

Age‐0

Age‐0

Expanded

Expanded

Age‐1

Age‐1

Age‐Length

Age‐Length

Age‐1

Age‐1 36

Figure 4. continued.

D

Expanded

Expanded

Age‐2

Age‐2

Age‐Length

Age‐Length

Age‐2

Age‐2

37

38

March

May

July

September

Figure 5. Abundance (kg per hectare swept) of Atlantic croaker in Chesapeake Bay, 2002.

November

39

March

May

July

September

Figure 6. Abundance (kg per hectare swept) of Atlantic croaker in Chesapeake Bay, 2003.

November

40

March

May

July

September

Figure 7. Abundance (kg per hectare swept) of Atlantic croaker in Chesapeake Bay, 2004.

November

41

March

May

July

September

Figure 8. Abundance (kg per hectare swept) of Atlantic croaker in Chesapeake Bay, 2005.

November

42

March

May

July

September

Figure 9. Abundance (kg per hectare swept) of Atlantic croaker in Chesapeake Bay, 2006.

November

43

March

May

July

Figure 10. Abundance (kg per hectare swept) of Atlantic croaker in Chesapeake Bay, 2007.

November

44

March

May

July

Figure 11. Abundance (kg per hectare swept) of Atlantic croaker in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 12. Atlantic croaker length-frequency in Chesapeake Bay 2002-2008.

45

Expanded Number

Figure 13. Atlantic croaker age-structure in Chesapeake Bay, 2002-2008.

46

Figure 13. continued.

C 47

Figure 14. Atlantic croaker diet in Chesapeake Bay 2002-2008 combined.

48

Black Sea Bass

49

Figure 15. Black sea bass minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay 2002-2008.

A

B

50

Figure 16. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for black seabass.

A

B

51

Table 4. Abundance indices (number and biomass) for black seabass, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

LCI

Index

By Weight UCI

CV

All Ages Geometric Mean

Age 1

LCI

Index

0.47 0.40 0.14 0.08 0.08 0.33 0.07

0.87 0.77 0.37 0.28 0.37 0.83 0.26

1.38 1.23 0.65 0.52 0.73 1.52 0.49

19.3 20.5 28.9 34.7 37.1 26.5 35.5

Geometric Mean 2002 0.18 2003 0.08 2004 0.08 2005 0.04 2006 0.01 2007 0.11 2008 0.02

Arithmetic Mean 2002 10.05 2003 4.83 2004 2.18 2005 0.85 2006 0.00 2007 6.78 2008 0.00

16.55 12.11 5.86 6.08 9.89 16.74 6.16

23.05 19.39 9.54 11.31 21.98 26.70 12.53

19.6 30.0 31.4 43.0 61.1 29.7 51.6

Arithmetic Mean 2002 0.83 2003 0.13 2004 0.29 2005 0.01 2006 0.00 2007 0.36 2008 0.00

1.41 1.02 0.91 0.74 0.67 1.07 0.49

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.71 0.69 0.35 0.26 0.23 0.50 0.14

2002 2003 2004 2005 2006 2007 2008

Age 0

Year

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.04 0.03 0.03 0.00 0.07 0.33 0.13

By Aged Sub-Sample Expansion 2002 0.04 0.00 2003 0.03 0.00 2004 0.03 0.00 2005 0.00 0.00 2006 0.14 0.00 2007 0.32 0.07 2008 0.19 0.03

0.13 0.08 0.09 0.00 0.33 0.65 0.38

100.0 100.0 100.0 0.0 59.7 38.8 41.8

By Age-Length 2002 2003 2004 2005 2006 2007 2008

0.14 0.09 0.15 0.00 0.37 0.65 0.43

28.9 64.5 56.1 0.0 49.2 38.8 38.7

Key 0.04 0.00 0.00 0.00 0.00 0.07 0.05

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.09 0.04 0.07 0.00 0.17 0.32 0.22

By Aged Sub-Sample Expansion 2002 0.63 0.32 2003 0.44 0.18 2004 0.37 0.14 2005 0.28 0.08 2006 0.24 0.01 2007 0.38 0.09 2008 0.03 0.00

1.00 0.77 0.64 0.51 0.51 0.75 0.09

21.2 27.9 29.0 34.6 47.6 36.3 100.0

By Age-Length 2002 2003 2004 2005 2006 2007 2008

1.17 1.17 0.63 0.51 0.53 0.75 0.12

19.6 20.6 28.9 34.9 42.9 36.3 70.7

Key 0.40 0.38 0.14 0.08 0.03 0.09 0.00

0.75 0.73 0.36 0.27 0.26 0.38 0.05

52

CV

0.32 0.20 0.19 0.14 0.13 0.28 0.10

0.47 0.34 0.32 0.24 0.26 0.47 0.18

19.4 29.0 29.0 35.1 44.1 28.8 39.9

2.00 1.90 1.54 1.47 1.48 1.79 0.97

20.7 43.4 34.2 49.1 60.0 33.3 49.6

By Aged Sub-Sample Expansion 2002 0.02 0.00 2003 0.01 0.00 2004 0.02 0.00 2005 0.00 0.00 2006 0.03 0.00 2007 0.17 0.04 2008 0.07 0.00

0.06 0.04 0.05 0.00 0.09 0.33 0.14

100.0 100.0 100.0 0.0 79.2 38.9 46.7

By Age-Length 2002 2003 2004 2005 2006 2007 2008

0.13 0.00 0.31 0.00 0.23 1.00 0.76

8.3 0.0 8.7 0.0 1.1 3.8 14.3

Key 0.09 0.00 0.21 0.00 0.22 0.81 0.37

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.71 0.69 0.35 0.26 0.23 0.50 0.14

UCI

0.11 0.18 0.26 0.00 0.22 0.91 0.55

0.01 0.01 0.01 0.00 0.02 0.11 0.05

By Aged Sub-Sample Expansion 2002 0.23 0.12 2003 0.17 0.06 2004 0.18 0.07 2005 0.13 0.04 2006 0.09 0.00 2007 0.09 0.02 2008 0.01 0.00

0.34 0.29 0.31 0.24 0.20 0.17 0.02

21.1 31.8 29.1 34.8 53.5 39.1 100.0

By Age-Length 2002 2003 2004 2005 2006 2007 2008

1.39 2.58 1.53 0.91 0.87 0.52 0.00

3.4 7.5 2.3 5.6 9.0 9.6 0.0

Key 1.14 1.57 1.33 0.67 0.54 0.33 0.00

1.26 2.03 1.43 0.79 0.70 0.42 0.08

Figure 17. Abundance indices (number and biomass) for black seabass based on geometric (A) and arithmetic (B) means.

A

B

53

Figure 18. Black seabass age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-0 (B), age-1 (C) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐0

Age‐0

Age‐Length

Age‐Length

B

C

Age‐0

Age‐0

Expanded

Expanded

Age‐1

Age‐1

Age‐Length

Age‐Length

Age‐1

Age‐1 54

55

56

March

May

July

Figure 19. Abundance (kg per hectare swept) of black seabass in Chesapeake Bay, 2002.

September

November

57

March

May

July

Figure 20. Abundance (kg per hectare swept) of black seabass in Chesapeake Bay, 2003.

September

November

58

March

May

July

Figure 21. Abundance (kg per hectare swept) of black seabass in Chesapeake Bay, 2004.

September

November

59

March

May

July

Figure 22. Abundance (kg per hectare swept) of black seabass in Chesapeake Bay, 2005.

September

November

60

March

May

July

Figure 23. Abundance (kg per hectare swept) of black seabass in Chesapeake Bay, 2006.

September

November

61

March

May

July

Figure 24. Abundance (kg per hectare swept) of black seabass in Chesapeake Bay, 2007.

November

62

March

May

July

Figure 25. Abundance (kg per hectare swept) of black seabass in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 26. Black sea bass length-frequency in Chesapeake Bay, 2002-2008.

63

Figure 27. Black seabass age-structure in Chesapeake Bay, 2002-2008.

64

Figure 27. continued.

65

Figure 28. Black sea bass diet in Chesapeake Bay, 2002-2008 combined.

66

Bluefish

67

Figure 29. Bluefish minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B

68

Figure 30. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for bluefish.

A

B

69

Table 5. Abundance indices (number and biomass) for bluefish, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

LCI

Index

By Weight UCI

CV

All Ages Geometric Mean

Age 1

LCI

0.25 0.73 0.25 0.70 0.24 0.89 0.17

0.57 1.25 0.55 1.20 0.56 1.93 0.50

0.97 1.93 0.91 1.85 0.96 3.52 0.91

25.0 16.4 24.3 16.4 25.7 20.3 30.1

Geometric Mean 2002 0.18 2003 0.35 2004 0.17 2005 0.40 2006 0.11 2007 0.58 2008 0.11

Arithmetic Mean 2002 3.71 2003 5.19 2004 3.78 2005 16.39 2006 3.05 2007 12.02 2008 0.00

9.99 29.14 9.25 39.71 7.64 24.18 39.14

16.26 53.09 14.72 63.03 12.23 36.33 101.91

31.4 41.1 29.6 29.4 30.0 25.1 80.2

Arithmetic Mean 2002 1.39 2003 0.00 2004 1.21 2005 2.82 2006 0.27 2007 3.66 2008 0.00

2002 2003 2004 2005 2006 2007 2008

Age 0

Year

By Proportion 2002 2003 2004 2005 2006 2007 2008

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.25 1.07 0.39 1.11 0.43 1.30 0.34

Index

UCI

CV

0.42 0.61 0.37 0.68 0.29 1.19 0.35

0.70 0.93 0.60 1.01 0.50 2.05 0.63

26.1 18.8 25.0 17.4 29.4 21.0 31.9

3.68 8.04 2.99 8.52 1.98 8.76 14.18

5.97 16.45 4.78 14.22 3.70 13.85 37.81

31.2 52.3 29.9 33.5 43.3 29.1 83.3

0.32 0.11 0.12 0.09 0.13 0.62 0.14

By Aged Sub-Sample Expansion 2002 0.23 0.05 2003 1.05 0.60 2004 0.38 0.14 2005 1.00 0.58 2006 0.44 0.18 2007 1.62 0.75 2008 0.45 0.15

0.45 1.61 0.66 1.54 0.76 2.94 0.84

39.3 17.0 29.1 17.1 26.9 21.1 31.5

By Aged Sub-Sample Expansion 2002 0.16 0.03 2003 0.49 0.28 2004 0.23 0.08 2005 0.55 0.33 2006 0.21 0.08 2007 0.93 0.45 2008 0.31 0.09

0.31 0.72 0.41 0.82 0.35 1.55 0.57

40.6 18.4 30.8 18.0 29.8 21.5 33.8

By Age-Length 2002 2003 2004 2005 2006 2007 2008

0.54 1.69 0.74 1.62 0.89 2.84 0.81

29.4 16.4 26.1 16.9 25.3 21.1 31.3

By Age-Length 2002 2003 2004 2005 2006 2007 2008

1.44 3.41 3.82 2.93 2.17 8.41 2.59

6.4 4.1 7.2 7.8 7.4 2.2 5.5

Key 0.12 0.65 0.19 0.61 0.23 0.73 0.15

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.32 1.10 0.44 1.05 0.52 1.58 0.44

Key 0.99 2.52 2.25 1.72 1.36 6.81 1.79

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.32 0.11 0.12 0.09 0.13 0.62 0.14

1.21 2.94 2.95 2.27 1.73 7.57 2.16

0.18 0.53 0.26 0.63 0.22 0.81 0.24

By Aged Sub-Sample Expansion 2002 0.34 0.11 2003 0.09 0.00 2004 0.11 0.00 2005 0.17 0.02 2006 0.12 0.00 2007 0.21 0.00 2008 0.06 0.00

0.62 0.20 0.23 0.33 0.28 0.46 0.16

32.4 59.6 48.2 42.7 59.9 50.1 71.5

By Aged Sub-Sample Expansion 2002 0.26 0.08 2003 0.06 0.00 2004 0.09 0.00 2005 0.13 0.02 2006 0.10 0.00 2007 0.21 0.00 2008 0.05 0.00

0.48 0.15 0.18 0.25 0.23 0.47 0.14

34.1 61.0 48.2 42.7 60.0 50.8 71.3

By Age-Length 2002 2003 2004 2005 2006 2007 2008

0.70 0.43 0.32 0.42 0.28 1.02 0.36

28.6 29.6 40.8 32.4 53.8 31.0 55.4

By Age-Length 2002 2003 2004 2005 2006 2007 2008

1.61 1.53 1.21 1.00 0.00 4.65 0.00

4.9 3.9 3.0 9.3 0.0 11.1 0.0

Key 0.16 0.10 0.03 0.08 0.00 0.18 0.00

0.40 0.25 0.16 0.24 0.13 0.55 0.16

70

Key 1.20 1.21 1.02 0.61 0.00 2.01 0.00

1.40 1.36 1.11 0.80 1.21 3.12 0.62

Figure 31. Abundance indices (number and biomass) for bluefish based on geometric (A) and arithmetic (B) means.

A

B

71

Figure 32. Bluefish age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-0 (B), age-1 (C) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐0

Age‐0

Age‐Length

Age‐Length

B

C

Age‐0

Age‐0

Expanded

Expanded

Age‐1

Age‐1

Age‐Length

Age‐Length

Age‐1

Age‐1

72

73

74

March

May

July

Figure 33. Abundance (kg per hectare swept) of bluefish in Chesapeake Bay, 2002.

September

November

75

March

May

July

Figure 34. Abundance (kg per hectare swept) of bluefish in Chesapeake Bay, 2003.

September

November

76

March

May

July

Figure 35. Abundance (kg per hectare swept) of bluefish in Chesapeake Bay, 2004.

September

November

77

March

May

July

Figure 36. Abundance (kg per hectare swept) of bluefish in Chesapeake Bay, 2005.

September

November

78

March

May

July

Figure 37. Abundance (kg per hectare swept) of bluefish in Chesapeake Bay, 2006.

September

November

79

March

May

July

Figure 38. Abundance (kg per hectare swept) of bluefish in Chesapeake Bay, 2007.

November

80

March

May

July

Figure 39. Abundance (kg per hectare swept) of bluefish in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 40. Bluefish length-frequency in Chesapeake Bay, 2002-2008.

81

Figure 41. Bluefish age-structure in Chesapeake Bay, 2002-2008.

82

Figure 41. continued.

83

Figure 42. Bluefish diet in Chesapeake Bay, 2002-2008 combined.

84

Butterfish

85

Figure 43 Butterfish minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B

86

Figure 44. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for butterfish.

A

B

87

Table 6. Abundance indices (number and biomass) for butterfish, overall (calculated as geometric and arithmetic means).

By Number Year

LCI

Index

By Weight UCI

CV

Year

All Ages Geometric Mean

LCI

1.73 6.95 18.15 6.05 3.50 1.49 3.40

4.61 16.50 41.04 13.14 7.02 4.24 7.54

10.52 37.53 91.25 27.34 13.29 10.02 15.60

20.9 13.8 10.5 13.1 13.9 22.4 15.5

Geometric Mean 2002 0.48 2003 1.92 2004 3.92 2005 1.52 2006 0.98 2007 0.49 2008 1.10

Arithmetic Mean 2002 10.45 2003 217.08 2004 160.64 2005 142.87 2006 54.82 2007 4.06 2008 89.65

134.15 408.88 551.89 237.72 118.16 75.97 186.54

257.85 600.67 943.14 332.57 181.50 147.88 283.44

46.1 23.5 35.4 20.0 26.8 47.3 26.0

Arithmetic Mean 2002 0.46 2003 10.85 2004 11.19 2005 7.04 2006 2.98 2007 0.13 2008 7.41

2002 2003 2004 2005 2006 2007 2008

88

Index

UCI

CV

1.14 3.83 7.00 2.76 1.75 1.18 2.06

2.08 6.98 12.03 4.59 2.82 2.18 3.46

24.1 16.0 11.7 15.1 16.3 24.2 16.8

5.95 25.70 47.80 13.48 8.60 5.36 15.34

11.44 40.55 84.41 19.93 14.22 10.58 23.27

46.2 28.9 38.3 23.9 32.7 48.8 25.9

Figure 45. Abundance indices (number and biomass) for butterfish based on geometric (A) and arithmetic (B) means.

A

B

89

90

March

May

July

Figure 46. Abundance (kg per hectare swept) of butterfish in Chesapeake Bay, 2002.

September

November

91

March

May

July

Figure 47. Abundance (kg per hectare swept) of butterfish in Chesapeake Bay, 2003.

September

November

92

March

May

July

Figure 48. Abundance (kg per hectare swept) of butterfish in Chesapeake Bay, 2004.

September

November

93

March

May

July

Figure 49. Abundance (kg per hectare swept) of butterfish in Chesapeake Bay, 2005.

September

November

94

March

May

July

Figure 50. Abundance (kg per hectare swept) of butterfish in Chesapeake Bay, 2006.

September

November

95

March

May

July

Figure 51. Abundance (kg per hectare swept) of butterfish in Chesapeake Bay, 2007.

November

96

March

May

July

Figure 52. Abundance (kg per hectare swept) of butterfish in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 53. Butterfish length-frequency in Chesapeake Bay, 2002-2008.

97

98

Kingfish (spp.)

99

Figure 54. Kingfish minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B

100

Figure 55. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for kingfish.

A

B

101

Table 7. Abundance indices (number and biomass) for kingfish, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

All Ages

Age 0

Age 1

Age 2

LCI

Index

By Weight UCI

Geometric Mean 2002 0.72 2003 1.47 2004 0.74 2005 1.70 2006 2.95 2007 1.23 2008 4.37

1.89 3.33 1.57 3.45 6.27 3.09 9.06

3.86 6.57 2.79 6.33 12.39 6.51 17.86

Arithmetic Mean 2002 12.62 2003 22.06 2004 4.15 2005 28.61 2006 39.99 2007 21.08 2008 71.03

49.91 53.77 32.38 57.91 96.73 60.55 287.14

87.20 85.49 60.60 87.20 153.48 100.01 503.25

By Proportion 2002 2003 2004 2005 2006 2007 2008

CV

Year

LCI

Index 0.98 1.88 0.85 1.68 2.97 1.61 3.68

1.81 3.37 1.45 2.76 5.12 2.98 6.32

25.3 19.8 22.8 17.2 15.7 22.1 14.5

37.4 29.5 43.6 25.3 29.3 32.6 37.6

Arithmetic Mean 2002 3.16 2003 5.87 2004 0.33 2005 5.38 2006 9.23 2007 3.98 2008 14.02

8.75 15.31 8.54 10.82 17.95 11.99 54.13

14.34 24.76 16.75 16.26 26.66 19.99 94.24

31.9 30.8 48.1 25.1 24.3 33.4 37.1

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.48 0.06 0.14 0.53 0.36 0.46

By Aged Sub-Sample Expansion 2002 0.57 0.06 2003 0.00 0.18 2004 0.27 0.08 2005 0.17 0.57 2006 0.24 0.00 2007 0.00 0.20 2008

1.34 0.50 0.49 1.11 0.58 0.53

43.9 70.9 34.5 32.8 55.6 66.9

By Aged Sub-Sample Expansion 2002 0.21 0.00 2003 0.00 0.08 2004 0.07 0.02 2005 0.03 0.15 2006 0.07 0.00 2007 0.00 0.08 2008

By Age-Length Key 2002 0.17 2003 0.00 2004 0.07 2005 0.21 2006 0.09 2007 0.21 2008

1.52 0.69 0.48 1.24 1.03 1.56

35.7 55.6 34.7 30.8 38.9 33.2

By Age-Length Key 2002 1.50 2003 2004 0.33 2005 0.47 2006 0.72 2007 1.10 2008

By Proportion 2002 2003 2004 2005 2006 2007 2008

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.64 0.89 0.15 1.13 0.84 0.56

1.61 0.84 0.40 0.74 1.15 1.78

1.09 1.72 0.37 1.71 0.98 0.90

31.5 30.7 52.5 26.1 39.9 45.8

By Aged Sub-Sample Expansion 2002 0.11 0.35 2003 0.16 0.49 2004 0.00 0.09 2005 0.21 0.51 2006 0.05 0.26 2007 0.01 0.21 2008

By Age-Length Key 2002 0.34 2003 0.53 2004 0.17 2005 0.58 2006 0.65 2007 0.34 2008

1.00 1.38 0.45 1.27 1.32 0.98

1.99 2.72 0.79 2.28 2.28 1.91

28.7 25.7 28.5 22.3 20.4 28.5

By Age-Length Key 2002 7.42 2003 7.87 2004 2.11 2005 4.10 2006 1.50 2007 2.36 2008

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.06 1.71 0.70 0.38 2.23 0.58

By Proportion 2002 2003 2004 2005 2006 2007 2008

8.81 10.85 2.49 4.68 2.05 3.95

55.7 72.1 38.6 38.8 78.6 75.0

1.74

2.4

0.46 1.07 1.69 2.69

6.8 15.5 14.6 13.8

0.62 0.90 0.20 0.89 0.52 0.44

31.8 31.0 52.2 26.7 40.5 47.1

10.43 14.82 2.93 5.33 2.73 6.30

3.3 5.8 4.7 3.1 9.0 12.1

0.23 1.77 0.99 0.74 1.95 0.78

69.4 26.2 27.1 34.3 22.5 36.5

1.16 27.92 17.81 4.99 12.49 6.58

1.0 6.2 5.3 3.1 4.8 13.0

0.03 0.97 0.38 0.19 1.05 0.30

By Aged Sub-Sample Expansion 2002 0.00 0.13 2003 1.50 0.56 2004 0.33 0.85 2005 0.61 0.16 2006 0.88 2.08 2007 0.75 0.19 2008

0.34 2.99 1.57 1.22 4.05 1.57

70.2 25.6 26.7 34.1 22.0 34.5

By Aged Sub-Sample Expansion 2002 0.00 0.09 2003 0.95 0.38 2004 0.23 0.56 2005 0.39 0.11 2006 0.51 1.11 2007 0.40 0.09 2008

By Age-Length Key 2002 0.05 2003 0.62 2004 0.38 2005 0.46 2006 1.72 2007 0.64 2008

0.42 3.04 1.69 1.76 6.35 2.79

37.6 24.4 25.5 22.8 16.6 23.0

By Age-Length Key 2002 1.10 2003 12.74 2004 9.67 2005 3.85 2006 7.57 2007 2.28 2008

102

0.51 0.20 0.14 0.29 0.18 0.22

0.33 0.50 0.08 0.55 0.40 0.29

By Aged Sub-Sample Expansion 2002 0.18 0.57 2003 0.27 0.86 2004 0.00 0.16 2005 0.37 0.93 2006 0.08 0.46 2007 0.03 0.40 2008

0.22 1.56 0.92 1.01 3.47 1.49

CV

24.4 19.1 20.5 16.7 15.4 21.6 13.6

0.92 0.11 0.26 1.10 0.76 0.88

0.72 0.28 0.26 0.64 0.49 0.76

UCI

Geometric Mean 2002 0.40 2003 0.90 2004 0.40 2005 0.91 2006 1.57 2007 0.71 2008 1.99

1.13 18.93 13.17 4.39 9.75 3.99

Figure 56. Abundance indices (number and biomass) for kingfish based on geometric (A) and arithmetic (B) means.

A

B

103

Figure 57. Kingfish age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-0 (B), age-1 (C) and age-2 (D) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐0

Age‐0

Age‐Length

Age‐Length

B

C

Age‐0

Age‐0

Expanded

Expanded

Age‐1

Age‐1

Age‐Length

Age‐Length

Age‐1

Age‐1

104

Figure 57. continued.

D

Expanded

Expanded

Age‐2

Age‐2

Age‐Length

Age‐Length

Age‐2

Age‐2

105

106

March

May

July

Figure 58. Abundance (kg per hectare swept) of kingfish in Chesapeake Bay, 2002.

September

November

107

March

May

July

Figure 59. Abundance (kg per hectare swept) of kingfish in Chesapeake Bay, 2003.

September

November

108

March

May

July

Figure 60. Abundance (kg per hectare swept) of kingfish in Chesapeake Bay, 2004.

September

November

109

March

May

July

Figure 61. Abundance (kg per hectare swept) of kingfish in Chesapeake Bay, 2005.

September

November

110

March

May

July

Figure 62. Abundance (kg per hectare swept) of kingfish in Chesapeake Bay, 2006.

September

November

111

March

May

July

Figure 63. Abundance (kg per hectare swept) of kingfish in Chesapeake Bay, 2007.

November

112

March

May

July

Figure 64. Abundance (kg per hectare swept) of kingfish in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 65. Kingfish length-frequency in Chesapeake Bay, 2002-2008.

113

Figure 66. Kingfish age-structure in Chesapeake Bay, 2002-2007.

114

Figure 66. continued.

115

Figure 67. Kingfish diet in Chesapeake Bay, 2002-2008 combined.

116

Northern Puffer

117

Figure 68. Northern puffer minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B

118

Figure 69. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for northern puffer.

A

B

119

Table 8. Abundance indices (number and biomass) for northern puffer, overall (calculated as geometric and arithmetic means).

By Number Year

LCI

Index

By Weight UCI

CV

Year

All Ages Geometric Mean

LCI

13.07 5.72 0.29 1.80 1.03 9.28 0.90

37.25 15.25 1.20 5.48 3.77 24.88 2.79

102.97 38.25 2.73 14.02 10.22 64.15 6.55

13.7 15.8 33.7 22.5 27.4 14.2 25.9

Geometric Mean 2002 3.23 2003 1.41 2004 0.14 2005 0.67 2006 0.48 2007 2.76 2008 0.36

Arithmetic Mean 2002 143.65 2003 84.24 2004 2.68 2005 0.00 2006 13.94 2007 30.91 2008 8.63

215.28 169.23 31.35 112.08 45.57 138.34 49.29

286.90 254.21 60.03 233.76 77.21 245.77 89.94

16.6 25.1 45.7 54.3 34.7 38.8 41.2

Arithmetic Mean 2002 11.43 2003 7.21 2004 0.00 2005 0.18 2006 2.06 2007 2.38 2008 0.85

2002 2003 2004 2005 2006 2007 2008

120

Index

UCI

CV

6.49 3.38 0.60 1.72 1.43 5.88 0.94

12.26 6.95 1.23 3.42 2.98 11.57 1.78

14.2 20.2 35.6 24.4 27.9 15.7 27.0

19.30 23.84 5.84 11.13 5.95 18.70 4.25

27.17 40.47 12.08 22.09 9.84 35.02 7.65

20.4 34.9 53.4 49.2 32.7 43.6 40.0

Figure 70. Abundance indices (number and biomass) for northern puffer based on geometric (A) and arithmetic (B) means.

A

B

121

122

Figure 71. Abundance (kg per hectare swept) of northern puffer in Chesapeake Bay, 2002.

123

Figure 72. Abundance (kg per hectare swept) of northern puffer in Chesapeake Bay, 2003.

124

Figure 73. Abundance (kg per hectare swept) of northern puffer in Chesapeake Bay, 2004.

125

Figure 74. Abundance (kg per hectare swept) of northern puffer in Chesapeake Bay, 2005.

126

Figure 75. Abundance (kg per hectare swept) of northern puffer in Chesapeake Bay, 2006.

127

Figure 76. Abundance (kg per hectare swept) of northern puffer in Chesapeake Bay, 2007.

128

Figure 77. Abundance (kg per hectare swept) of northern puffer in Chesapeake Bay, 2008.

Expanded Number

Figure 78. Northern puffer length-frequency in Chesapeake Bay, 2002-2008.

129

Figure 79. Northern puffer diet in Chesapeake Bay, 2002-2008 combined.

130

Scup

131

Figure 80. Scup minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B

132

Figure 81. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for scup.

A

B

133

Table 9. Abundance indices (number and biomass) for scup, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

LCI

Index

By Weight UCI

CV

All Ages Geometric Mean

Age 1

LCI

1.22 2.48 6.18 6.37 4.02 7.21 0.41

3.61 5.28 13.00 13.78 10.69 19.32 1.24

8.58 10.34 26.31 28.64 26.21 49.33 2.56

23.9 16.1 12.7 12.9 17.2 15.1 28.6

Geometric Mean 2002 0.34 2003 0.81 2004 1.40 2005 1.68 2006 1.02 2007 1.09 2008 0.13

Arithmetic Mean 2002 0.00 2003 58.87 2004 0.00 2005 316.79 2006 103.40 2007 92.81 2008 2.92

137.00 148.29 525.42 746.34 331.79 272.11 32.70

322.28 237.71 1,076.01 1,175.88 560.19 451.41 62.48

67.6 30.2 52.4 28.8 34.4 32.9 45.5

Arithmetic Mean 2002 0.00 2003 3.44 2004 0.00 2005 14.60 2006 4.19 2007 3.05 2008 0.00

2002 2003 2004 2005 2006 2007 2008

Age 0

Year

By Proportion 2002 2003 2004 2005 2006 2007 2008

By Proportion 2002 2003 2004 2005 2006 2007 2008

1.62 1.15 0.46 9.82 7.13 2.11

Index

2.08 2.47 4.52 4.95 3.56 4.19 0.75

29.2 17.7 16.1 14.4 18.4 19.0 32.0

9.84 8.34 26.83 33.72 12.97 7.53 2.13

24.68 13.24 55.55 52.83 21.75 12.00 4.39

75.4 29.4 53.5 28.3 33.9 29.7 53.2

1.09 0.65 0.29 2.62 2.06 0.89

44.9 33.7 52.6 20.5 22.8 36.8

4.31 2.82 1.70 6.32 10.20 4.68

15.1 14.8 16.5 7.3 14.8 17.3

1.20 2.09 4.16 1.76 1.22 2.98

35.8 19.2 16.9 24.1 30.2 21.2

5.91 6.44 15.17 7.78 3.33 12.40

10.8 9.9 7.8 13.8 13.0 20.2

0.46 0.33 0.09 2.13 1.36 0.25

2.64 2.05 0.94 10.14 7.80 2.67

40.7 31.8 44.9 17.8 22.0 34.6

By Aged Sub-Sample Expansion 2002 0.47 0.04 2003 0.35 0.10 2004 0.13 2005 1.49 0.71 2006 1.15 0.52 2007 0.44 0.10 2008

By Age-Length 2002 2003 2004 2005 2006 2007 2008

3.00 4.78 3.12 18.50 12.26 5.57

33.6 18.3 21.2 12.9 19.4 26.0

By Age-Length 2002 2003 2004 2005 2006 2007 2008

By Proportion 2002 2003 2004 2005 2006 2007 2008

1.29 2.61 1.70 9.60 5.44 2.45

Key 1.45 1.07 0.65 3.40 2.71 1.32

By Proportion 2002 2003 2004 2005 2006 2007 2008

1.95 4.10 11.82 3.91 3.56 17.22

2.60 1.81 1.11 4.68 5.44 2.63

0.56 1.17 2.40 0.85 0.68 2.04

By Aged Sub-Sample Expansion 2002 1.91 0.53 2003 4.09 1.83 2004 10.92 5.10 2005 3.46 1.32 2006 2.57 0.80 2007 11.97 4.59 2008

4.56 8.17 22.32 7.57 6.07 29.11

30.2 18.1 13.5 21.9 26.9 16.4

By Aged Sub-Sample Expansion 2002 0.58 0.14 2003 1.26 0.65 2004 2.41 1.25 2005 0.99 0.43 2006 0.65 0.22 2007 1.64 0.75 2008

By Age-Length 2002 2003 2004 2005 2006 2007 2008

7.10 9.24 24.59 16.68 11.48 38.25

23.5 16.0 12.7 13.3 18.2 15.1

By Age-Length 2002 2003 2004 2005 2006 2007 2008

Key 1.12 2.31 5.88 4.29 2.24 6.15

3.15 4.82 12.27 8.67 5.36 15.75

134

CV

1.03 1.51 2.64 2.99 2.03 2.29 0.41

By Aged Sub-Sample Expansion 2002 1.04 0.14 2003 0.98 0.28 2004 0.42 0.04 2005 4.91 2.13 2006 3.53 1.33 2007 1.16 0.27 2008 Key 0.31 1.26 0.77 4.76 2.13 0.81

UCI

Key 2.48 2.84 6.61 2.43 1.37 2.01

3.90 4.35 10.10 4.49 2.20 5.35

Figure 82. Abundance indices (number and biomass) for scup based on geometric (A) and arithmetic (B) means.

A

B

135

Figure 83. Scup age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-0 (B), age-1 (C) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐0

Age‐0

B

Age‐Length

C

Age‐Length

Age‐0

Age‐0

Expanded

Expanded

Age‐1

Age‐1

Age‐Length

Age‐Length

Age‐1

Age‐1 136

137

138

March

May

July

Figure 84. Abundance (kg per hectare swept) of scup in Chesapeake Bay, 2002.

September

November

139

March

May

July

Figure 85. Abundance (kg per hectare swept) of scup in Chesapeake Bay, 2003.

September

November

140

March

May

July

Figure 86. Abundance (kg per hectare swept) of scup in Chesapeake Bay, 2004.

September

November

141

March

May

July

Figure 87. Abundance (kg per hectare swept) of scup in Chesapeake Bay, 2005.

September

November

142

March

May

July

Figure 88. Abundance (kg per hectare swept) of scup in Chesapeake Bay, 2006.

September

November

143

March

May

July

Figure 89. Abundance (kg per hectare swept) of scup in Chesapeake Bay, 2007.

November

144

March

May

July

Figure 90. Abundance (kg per hectare swept) of scup in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 91. Scup length-frequency in Chesapeake Bay, 2002-2008.

145

Figure 92. Scup age-structure in Chesapeake Bay, 2002-2007.

146

Figure 92. continued.

147

Figure 93. Scup diet in Chesapeake Bay, 2002-2008 combined.

148

Spot

149

Figure 94. Spot minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B

150

Figure 95. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for spot.

A

B

151

Table 10. Abundance indices (number and biomass) for spot, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

LCI

Index

By Weight UCI

CV

All Ages Geometric Mean

Age 0

Age 1

LCI

12.04 50.52 19.46 55.67 48.46 37.63 25.11

18.30 84.13 30.36 78.53 67.68 64.51 37.76

27.56 139.67 47.08 110.61 94.36 110.08 56.54

6.6 5.7 6.2 3.9 3.9 6.3 5.4

Geometric Mean 2002 4.06 2003 12.90 2004 5.73 2005 11.65 2006 11.00 2007 9.87 2008 6.17

Mean 435.53 633.37 481.34 1,355.35 1,130.93 1,130.89 928.62

614.27 1,484.52 618.63 1,699.56 1,493.69 1,531.86 1,267.25

793.02 2,335.67 755.91 2,043.77 1,856.45 1,932.84 1,605.87

14.5 28.7 11.1 10.1 12.1 13.1 13.4

Arithmetic Mean 2002 49.93 2003 67.18 2004 52.52 2005 139.58 2006 115.18 2007 101.39 2008 70.42

2002 2003 2004 2005 2006 2007 2008 Arithmetic 2002 2003 2004 2005 2006 2007 2008

Year

By Proportion 2002 2003 2004 2005 2006 2007 2008

By Aged Sub-Sample Expansion 2002 4.93 3.39 2003 33.06 17.71 2004 7.63 4.99 2005 14.19 10.43 2006 12.78 9.19 3.47 2007 2.29 2008 6.44 4.40

7.02 61.01 11.44 19.19 17.64 5.07 9.24

8.5 8.5 8.5 5.2 5.8 10.2 8.0

By Age-Length Key 2002 8.79 2003 35.94 2004 12.68 2005 37.49 2006 32.68 2007 21.37 2008 19.06

12.85 58.24 18.97 52.01 44.87 34.91 28.04

18.58 93.99 28.16 72.01 61.46 56.65 41.05

6.6 5.8 6.3 4.0 4.0 6.6 5.5

By Proportion 2002 2003 2004 2005 2006 2007 2008

6.41 29.43 9.42 28.23 28.60 25.96 17.82

UCI

CV

5.70 19.49 8.12 15.22 14.28 14.64 8.39

7.86 29.20 11.36 19.79 18.44 21.52 11.30

7.4 6.4 6.9 4.5 4.4 6.6 6.0

88.82 258.70 71.16 185.95 157.15 140.15 95.16

127.71 450.22 89.79 232.33 199.13 178.91 119.90

21.9 37.0 13.1 12.5 13.4 13.8 13.0

By Aged Sub-Sample Expansion 2002 2.01 1.47 2003 8.73 5.43 2004 2.44 1.71 2005 2.93 2.30 2006 3.32 2.62 2007 0.99 0.68 2008 1.74 1.31

2.68 13.73 3.36 3.69 4.15 1.36 2.26

9.0 9.1 9.6 6.4 6.0 12.3 8.5

By Age-Length Key 2002 11.53 2003 12.45 2004 8.08 2005 9.01 2006 10.87 2007 14.81 2008 9.74

15.95 20.76 11.40 13.23 15.05 24.79 18.02

2.8 4.2 3.3 3.5 2.9 4.1 5.4

By Proportion 2002 2003 2004 2005 2006 2007 2008

11.15 54.04 19.53 49.10 38.15 35.70 19.63

Index

By Proportion 2002 2003 2004 2005 2006 2007 2008

3.47 12.52 5.22 9.52 8.05 8.10 4.36

13.57 16.11 9.61 10.93 12.80 19.19 13.29

2.00 6.82 2.52 5.47 6.03 5.89 3.96

By Aged Sub-Sample Expansion 2002 6.28 4.00 2003 11.54 6.87 2004 9.11 5.82 2005 27.65 18.86 2006 20.06 13.83 51.12 2007 29.99 2008 13.84 9.13

9.60 18.99 13.97 40.35 28.91 86.65 20.75

9.5 9.2 8.5 5.5 5.8 6.6 7.1

By Aged Sub-Sample Expansion 2002 2.67 1.83 2003 4.67 2.98 2004 3.53 2.44 2005 8.69 6.40 2006 6.37 4.73 2007 12.38 8.37 2008 4.67 3.34

3.77 7.09 4.96 11.69 8.49 18.12 6.40

10.0 10.2 9.1 5.9 6.3 6.9 7.7

By Age-Length Key 2002 7.79 2003 22.77 2004 10.97 2005 23.85 2006 25.89 2007 24.83 2008 14.55

16.58 56.37 24.31 44.83 48.19 65.91 30.01

6.9 6.1 6.6 4.3 4.2 6.4 5.6

By Age-Length Key 2002 10.54 2003 9.01 2004 8.57 2005 11.01 2006 9.59 2007 25.76 2008 7.84

15.76 17.10 12.48 17.00 14.41 39.67 14.86

3.5 5.7 3.5 3.8 3.7 3.0 5.9

11.43 35.93 16.41 32.75 35.37 40.57 20.95

152

12.91 12.46 10.36 13.70 11.77 31.99 10.84

Figure 96. Abundance indices (number and biomass) for spot based on geometric (A) and arithmetic (B) means.

A

B

153

Figure 97. Spot age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-0 (B), age-1 (C) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐0

Age‐0

B

Age‐Length

C

Age‐Length

Age‐0

Age‐0

Expanded

Expanded

Age‐1

Age‐1

Age‐Length

Age‐Length

Age‐1

Age‐1

154

155

156

March

May

July

Figure 98. Abundance (kg per hectare swept) of spot in Chesapeake Bay, 2002.

September

November

157

March

May

July

Figure 99. Abundance (kg per hectare swept) of spot in Chesapeake Bay, 2003.

September

November

158

March

May

July

Figure 100. Abundance (kg per hectare swept) of spot in Chesapeake Bay, 2004.

September

November

159

March

May

July

Figure 101. Abundance (kg per hectare swept) of spot in Chesapeake Bay, 2005.

September

November

160

March

May

July

Figure 102. Abundance (kg per hectare swept) of spot in Chesapeake Bay, 2006.

September

November

161

March

May

July

Figure 103. Abundance (kg per hectare swept) of spot in Chesapeake Bay, 2007.

November

162

March

May

July

Figure 104. Abundance (kg per hectare swept) of spot in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 105. Spot length-frequency in Chesapeake Bay, 2002-2008.

163

Expanded Number

Figure 106. Spot age-structure in Chesapeake Bay, 2002-2008.

164

Figure 106. continued.

165

Figure 107. Spot diet in Chesapeake Bay, 2002-2008 combined.

166

Striped Bass

167

Figure 108. Striped bass minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B

168

Figure 109. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for striped bass.

A

B

169

Table 11. Abundance indices (number and biomass) for striped bass (March), overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

All Ages

Year LCI Geometric Mean 2002 0.49 2003 44.38 2004 178.07 2005 42.58 2006 19.81 2007 45.18 2008 90.24 Arithmetic Mean 2002 0.00 2003 261.25 2004 397.71 2005 419.70 2006 190.32 2007 269.60 2008 335.03

Age 1

By Proportion 2002 2003 2004 2005 2006 2007 2008

By Number Index 2.77 107.12 286.92 98.11 46.71 104.79 171.19

8.53 256.59 461.93 224.39 108.39 241.38 323.98

34.9 9.3 4.2 8.9 10.7 8.9 6.2

Year LCI Geometric Mean 2002 0.40 2003 23.51 2004 110.84 2005 25.43 2006 16.56 2007 26.38 2008 60.89

84.87 390.46 508.39 1,421.23 387.36 367.94 545.03

200.45 519.68 619.06 2,422.77 584.40 466.27 755.03

68.1 16.5 10.9 35.2 25.4 13.4 19.3

Arithmetic Mean 2002 0.00 2003 136.32 2004 299.40 2005 66.76 2006 152.22 2007 153.70 2008 295.22

Age 2

By Proportion 2002 2003 2004 2005 2006 2007 2008

1.72 2.22 35.50 7.06 4.17 0.30 10.44

By Proportion 2002 2003 2004 2005 2006 2007 2008

By Age-Length Key 2002 0.16 2003 31.09 2004 18.03 2005 19.46 2006 4.96 2007 19.11 2008 5.37

1.45 69.08 28.16 46.09 10.19 39.87 9.82

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.20 27.74 95.89 4.52 28.67 26.75 66.84

By Weight Index

CV

5.80 140.70 297.38 108.47 92.61 122.90 268.43

35.1 10.8 4.7 8.9 11.3 9.3 7.6

73.10 366.21 412.52 424.61 354.97 212.18 750.60

154.00 596.10 525.64 782.45 557.73 270.65 1,205.98

55.3 31.4 13.7 42.1 28.6 13.8 30.3

0.73 0.45 57.07 1.79 2.22 0.20 11.73

81.0 72.0 34.5 74.0 0.0 0.0 63.2

By Aged Sub-Sample Expansion 2002 0.17 0.00 2003 0.00 0.10 2004 0.38 0.09 2005 0.12 0.00 2006 0.00 0.00 2007 0.00 0.00 2008 0.00 0.04

5.09 4.46 61.30 13.36 8.82 0.65 18.24

40.4 22.6 7.4 13.8 19.6 46.8 10.7

By Age-Length Key 2002 2.13 2003 1.18 2004 8.20 2005 3.53 2006 5.06 2007 0.30 2008 5.26

By Proportion 2002 2003 2004 2005 2006 2007 2008

UCI

2.08 57.93 181.67 52.78 39.54 57.24 128.13

1.28 1.08 2.46 0.86 0.00 0.00 0.52

0.93 42.19 30.72 78.85 7.83 38.22 10.92

By Aged Sub-Sample Expansion 2002 0.07 1.58 2003 14.37 31.68 2004 3.24 1.28 2005 9.90 26.44 2006 3.45 1.06 2007 8.13 18.38 1.62 2008 0.42

Age 3

CV

0.97 0.83 90.13 3.32 2.62 0.36 15.67

By Aged Sub-Sample Expansion 2002 0.37 0.00 2003 0.00 0.35 2004 1.09 0.26 2005 0.29 0.00 2006 0.00 0.00 2007 0.00 0.00 2008 0.00 0.20

By Age-Length Key 2002 0.21 2003 0.90 2004 20.39 2005 3.53 2006 1.72 2007 0.02 2008 5.80

UCI

2.69 1.47 11.14 4.77 6.10 0.38 7.81

0.56 0.29 0.74 0.33 0.00 0.00 0.10

91.9 78.2 36.1 74.7 0.0 0.0 66.8

3.35 1.81 15.02 6.33 7.31 0.46 11.40

6.3 7.0 5.5 6.9 4.0 9.0 7.9

0.70 22.82 19.45 42.42 6.62 20.88 8.18

5.25 68.46 6.89 68.09 8.63 40.12 3.82

46.5 10.8 21.5 13.9 25.8 12.7 31.7

By Aged Sub-Sample Expansion 2002 0.04 0.92 2003 5.38 10.45 2004 1.62 0.71 2005 5.40 12.16 2006 1.96 0.73 2007 4.22 7.86 2008 0.84 0.24

2.53 19.52 3.03 26.07 4.05 14.04 1.71

46.9 12.0 22.3 14.0 24.6 12.1 32.1

4.19 152.01 43.69 107.38 20.04 82.05 17.38

41.9 9.2 6.3 10.8 13.1 9.6 11.1

By Age-Length Key 2002 1.97 2003 38.66 2004 8.46 2005 41.82 2006 7.56 2007 25.05 2008 4.93

3.12 51.32 11.11 61.32 12.24 37.83 6.92

4.72 68.03 14.52 89.69 19.48 56.90 9.57

11.6 3.5 5.0 4.5 8.4 5.5 7.0

By Proportion 2002 2003 2004 2005 2006 2007 2008

0.15 15.00 60.72 2.43 24.27 14.61 50.03

By Aged Sub-Sample Expansion 2002 0.00 0.53 2003 21.24 7.84 2004 30.92 63.98 2005 1.87 6.09 2006 24.32 10.21 2007 7.30 15.75 2008 38.48 20.80

1.58 54.96 131.28 16.49 56.19 32.79 70.49

61.9 14.9 8.5 23.1 12.6 12.5 8.1

By Aged Sub-Sample Expansion 2002 0.00 0.38 2003 13.35 5.49 2004 19.17 35.61 2005 1.33 3.87 2006 15.72 7.04 2007 6.00 12.36 2008 18.87 10.78

1.13 30.74 65.43 9.19 33.76 24.51 32.51

66.9 14.9 8.3 23.3 13.0 12.5 8.7

By Age-Length Key 2002 0.00 2003 8.21 2004 45.18 2005 4.40 2006 10.32 2007 12.89 2008 30.22

1.32 44.80 131.12 13.91 52.77 45.73 88.03

53.6 13.3 6.0 11.6 12.2 9.4 6.6

By Age-Length Key 2002 0.84 2003 20.75 2004 48.47 2005 5.70 2006 28.77 2007 22.04 2008 35.23

0.92 53.18 75.86 10.79 77.46 38.33 59.66

1.7 6.5 2.7 6.5 6.2 3.9 3.3

0.50 19.53 77.11 7.98 23.67 24.48 51.72

170

0.88 33.33 60.66 7.89 47.33 29.10 45.88

Figure 110. Abundance indices (number and biomass) for striped bass (March) based on geometric (A) and arithmetic (B) means.

A

B

171

Figure 111. Striped bass (March) age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-1 (B), age-2 (C) and age-3 (D) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐1

Age‐1

B

Age‐Length

C

Age‐Length

Age‐1

Age‐1

Expanded

Expanded

Age‐2

Age‐2

Age‐Length

Age‐Length

Age‐2

Age‐2

172

Figure 111. continued.

D

Expanded

Expanded

Age‐3

Age‐3

Age‐Length

Age‐Length

Age‐3

Age‐3

173

Table 12. Abundance indices (number and biomass) for striped bass (November), overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

All Ages

Year LCI Geometric Mean 2002 36.65 2003 2.31 2004 84.14 2005 12.87 2006 132.62 2007 2.91 2008 10.39 Arithmetic Mean 2002 97.90 2003 27.25 2004 323.73 2005 0.00 2006 247.52 2007 1.76 2008 98.98

Age 1

Age 2

Age 3

By Proportion 2002 2003 2004 2005 2006 2007 2008

By Number Index

UCI

CV

96.88 17.49 248.09 78.83 252.55 24.60 54.66

253.42 102.32 727.77 458.41 480.12 166.79 270.91

10.4 29.5 9.7 20.0 5.8 29.0 19.7

Year LCI Geometric Mean 2002 21.75 2003 2.30 2004 20.03 2005 7.68 2006 46.40 2007 3.12 2008 8.54

543.21 60.25 646.59 1,214.56 429.69 229.72 274.21

988.51 93.25 969.45 3,105.42 611.86 457.69 449.45

41.0 27.4 25.0 77.8 21.2 49.6 32.0

Arithmetic Mean 2002 99.73 2003 10.64 2004 60.13 2005 0.00 2006 117.81 2007 42.76 2008 28.74

By Proportion 2002 2003 2004 2005 2006 2007 2008

33.83 0.14 77.93 2.67 14.18 0.08 5.00

By Weight Index

UCI

CV

48.19 5.86 51.19 37.98 110.92 24.49 44.47

105.35 13.27 128.49 174.03 263.22 156.61 215.70

9.9 19.0 11.5 20.5 9.1 28.1 20.5

156.03 25.46 138.05 564.08 232.22 198.55 266.45

212.34 40.27 215.97 1,472.90 346.64 354.33 504.16

18.0 29.1 28.2 80.6 24.6 39.2 44.6

16.83 0.05 16.08 1.29 6.23 0.08 4.07

By Aged Sub-Sample Expansion 2002 25.13 6.62 2003 0.00 0.46 2004 176.98 63.00 2005 15.08 2.87 2006 8.97 36.21 2007 0.00 0.00 2008 1.75 13.41

88.56 1.66 493.95 65.84 137.84 0.00 74.57

18.9 80.1 9.9 25.7 18.2 0.0 31.1

By Aged Sub-Sample Expansion 2002 7.91 2.48 2003 0.00 0.30 2004 24.07 10.70 2005 5.59 1.28 2006 2.48 5.94 2007 0.00 0.00 2008 1.24 7.46

21.83 0.98 52.74 18.01 12.82 0.00 30.92

21.5 80.9 11.8 28.1 17.8 0.0 31.1

By Age-Length Key 2002 10.03 2003 0.03 2004 52.23 2005 2.17 2006 22.71 2007 0.00 2008 1.59

62.99 0.90 426.16 33.89 133.44 0.00 36.26

13.4 45.9 10.4 25.5 10.8 0.0 29.2

By Age-Length Key 2002 12.84 2003 0.25 2004 16.26 2005 2.45 2006 7.84 2007 0.00 2008 12.81

32.07 0.36 42.57 10.46 19.92 0.00 36.62

7.1 8.0 7.0 16.3 8.3 0.0 8.0

By Proportion 2002 2003 2004 2005 2006 2007 2008

25.57 0.40 149.78 9.52 55.46 0.00 8.82

By Proportion 2002 2003 2004 2005 2006 2007 2008

32.62 6.89 26.57 63.36 42.31 8.97 3.49

20.39 0.30 26.43 5.29 12.60 0.00 21.79

16.22 2.31 5.48 30.53 18.58 8.93 2.84

By Aged Sub-Sample Expansion 2002 12.08 28.38 2003 0.59 3.90 2004 5.88 0.79 2005 6.63 37.47 2006 3.86 0.12 2007 0.21 5.41 0.25 2008 0.00

64.98 14.14 25.45 192.93 20.07 32.94 0.56

12.0 35.5 34.9 22.2 46.4 44.9 51.0

By Aged Sub-Sample Expansion 2002 7.53 16.83 2003 0.45 2.61 2004 3.11 0.49 2005 4.15 19.27 2006 2.24 0.09 2007 0.18 3.95 2008 0.21 0.00

By Age-Length Key 2002 20.56 2003 1.64 2004 7.17 2005 9.62 2006 9.99 2007 0.85 2008 2.26

116.21 11.10 73.68 286.57 53.95 36.43 18.96

10.8 22.0 17.2 20.6 12.6 35.5 21.7

By Age-Length Key 2002 32.84 2003 3.34 2004 10.34 2005 12.85 2006 5.72 2007 30.18 2008 6.03

43.65 4.53 14.66 64.79 10.41 36.04 9.11

By Proportion 2002 2003 2004 2005 2006 2007 2008

3.52 1.52 17.11 1.75 68.07 6.25 17.36

By Proportion 2002 2003 2004 2005 2006 2007 2008

49.27 4.65 23.71 54.25 23.57 7.33 7.07

7.07 4.53 82.92 3.63 155.00 6.28 21.34

36.26 8.02 10.32 78.76 8.65 19.79 0.48

12.8 35.6 35.9 22.8 46.5 44.9 51.1

57.90 6.05 20.63 311.53 18.37 43.01 13.55

3.6 7.1 5.9 18.6 10.9 2.4 7.9

By Aged Sub-Sample Expansion 2002 0.00 1.13 2003 1.16 0.00 2004 0.34 3.62 2005 0.00 1.13 2006 41.18 8.63 2007 0.00 2.80 2008 6.64 1.32

3.90 3.66 14.90 4.50 183.65 16.41 24.14

54.7 50.1 40.4 63.0 19.7 57.0 29.3

By Aged Sub-Sample Expansion 2002 0.00 1.02 2003 1.02 0.00 2004 0.29 2.87 2005 0.00 1.09 2006 34.83 7.59 2007 0.00 2.54 2008 6.36 1.28

3.38 3.10 10.56 4.08 148.43 14.43 22.80

54.7 50.0 40.5 59.9 20.0 58.3 29.4

By Age-Length Key 2002 6.09 2003 2.21 2004 7.47 2005 1.68 2006 31.46 2007 1.08 2008 5.20

22.73 10.39 82.58 24.76 186.08 34.55 86.98

11.8 17.6 17.4 26.7 10.1 33.0 21.0

By Age-Length Key 2002 11.76 2003 4.16 2004 21.26 2005 13.23 2006 30.26 2007 29.63 2008 40.04

21.20 6.28 43.04 36.97 144.65 76.17 72.10

4.9 4.7 5.0 7.8 9.1 5.9 3.6

11.97 5.04 25.61 7.32 76.93 7.59 22.36

174

15.83 5.13 30.31 22.25 66.48 47.62 53.77

Figure 112. Abundance indices (number and biomass) for striped bass (November) based on geometric (A) and arithmetic (B) means.

A

B

175

Figure 113. Striped bass (November) age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-1 (B), age-2 (C) and age-3 (D) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐1

Age‐1

B

Age‐Length

C

Age‐Length

Age‐1

Age‐1

Expanded

Expanded

Age‐2

Age‐2

Age‐Length

Age‐Length

Age‐2

Age‐2

176

Figure 113. continued.

D

Expanded

Expanded

Age‐3

Age‐3

Age‐Length

Age‐Length

Age‐3

Age‐3

177

178

March

May

July

Figure 114. Abundance (kg per hectare swept) of striped bass in Chesapeake Bay, 2002.

September

November

179

March

May

July

Figure 115. Abundance (kg per hectare swept) of striped bass in Chesapeake Bay, 2003.

September

November

180

March

May

July

Figure 116. Abundance (kg per hectare swept) of striped bass in Chesapeake Bay, 2004.

September

November

181

March

May

July

Figure 117. Abundance (kg per hectare swept) of striped bass in Chesapeake Bay, 2005.

September

November

182

March

May

July

Figure 118. Abundance (kg per hectare swept) of striped bass in Chesapeake Bay, 2006.

September

November

183

March

May

July

Figure 119. Abundance (kg per hectare swept) of striped bass in Chesapeake Bay, 2007.

November

184

March

May

July

Figure 120. Abundance (kg per hectare swept) of striped bass in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 121. Striped bass length-frequency in Chesapeake Bay, 2002-2008.

185

Expanded Number

Figure 122. Striped bass age-structure in Chesapeake Bay, 2002-2008.

C 186

Figure 122. continued.

C

Expanded Number

C 187

Figure 123. Striped bass diet in Chesapeake Bay, 2002-2008 combined.

188

Summer Flounder

189

Figure 124. Summer flounder minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B

190

Figure 125. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for summer flounder.

A

B

191

Table 13. Abundance indices (number and biomass) for summer flounder, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

All Ages

Age 0

Age 1

Age 2

LCI

Index

By Weight UCI

Geometric Mean 2002 78.01 2003 17.65 2004 25.11 2005 87.92 2006 94.41 2007 53.32 2008 44.17

117.08 30.97 40.19 128.89 148.16 99.48 74.37

175.47 53.82 63.97 188.75 232.20 184.87 124.77

Arithmetic Mean 2002 244.92 2003 142.45 2004 152.28 2005 228.92 2006 290.70 2007 195.49 2008 241.78

346.04 199.02 271.26 296.42 348.21 267.81 340.22

447.16 255.60 390.24 363.93 405.72 340.14 438.66

By Proportion 2002 2003 2004 2005 2006 2007 2008

CV

CV

80.47 20.97 24.60 70.54 76.41 56.98 42.04

4.9 9.5 6.6 4.5 4.9 7.4 6.9

14.6 14.2 21.9 11.4 8.3 13.5 14.5

Arithmetic Mean 2002 117.70 2003 65.48 2004 17.68 2005 89.59 2006 90.84 2007 59.72 2008 80.31

165.27 103.55 108.68 119.97 123.42 83.20 114.94

212.84 141.63 199.69 150.36 156.01 106.67 149.58

14.4 18.4 41.9 12.7 13.2 14.1 15.1

By Aged Sub-Sample Expansion 2002 12.79 8.66 2003 2.22 3.57 2004 4.45 3.02 2005 4.08 5.85 2006 11.79 8.26 2007 7.28 11.98 2008 7.36 4.97

18.71 5.49 6.38 8.24 16.65 19.36 10.71

6.8 11.5 9.0 7.8 6.3 8.8 7.9

By Age-Length Key 2002 19.99 2003 14.13 2004 13.33 2005 9.07 2006 18.08 2007 13.62 2008 13.63

26.31 18.42 16.60 10.69 22.32 18.19 17.90

34.54 23.93 20.61 12.57 27.52 24.18 23.42

4.0 4.2 3.6 3.0 3.2 4.6 4.4

By Proportion 2002 2003 2004 2005 2006 2007 2008

27.43 3.89 8.68 13.36 25.96 13.74 14.24

By Aged Sub-Sample Expansion 2002 1.97 3.80 2003 1.64 2.93 2004 1.27 2.16 2005 6.20 9.78 2006 2.17 3.71 2007 1.34 3.09 2008 1.08 2.10

6.77 4.87 3.40 15.13 5.99 6.14 3.62

15.3 14.6 14.4 8.5 12.8 19.8 17.7

By Age-Length Key 2002 8.34 2003 11.98 2004 4.37 2005 19.10 2006 10.64 2007 9.48 2008 7.00

18.48 28.58 7.67 27.53 16.51 20.11 15.65

7.1 6.9 6.2 2.8 3.8 6.5 7.5

3.21 1.07 1.79 6.28 4.32 2.17 4.42

22.6 19.4 23.2 12.8 16.9 31.3 16.7

18.99 17.43 12.65 27.01 23.26 12.01 58.45

5.6 5.2 3.6 4.3 4.0 10.3 5.5

By Proportion 2002 2003 2004 2005 2006 2007 2008 6.4 11.3 8.7 7.7 6.4 8.1 7.2

By Age-Length Key 2002 33.60 2003 8.59 2004 13.51 2005 17.51 2006 38.37 2007 31.04 2008 22.08

55.61 14.48 21.95 26.53 62.61 55.27 36.89

91.61 24.00 35.29 39.94 101.79 97.83 61.21

6.1 8.7 7.3 6.0 5.8 7.0 6.8

By Proportion 2002 2003 2004 2005 2006 2007 2008

18.19 9.89 5.83 50.65 24.99 28.63 13.82

By Aged Sub-Sample Expansion 2002 2.80 5.78 2003 2.21 4.12 2004 1.84 3.32 2005 11.10 18.76 2006 3.25 6.04 2007 1.86 4.69 2008 1.49 3.07

11.09 7.17 5.57 31.26 10.67 10.31 5.66

15.1 14.3 14.4 8.2 12.9 19.8 17.5

By Age-Length Key 2002 10.21 2003 7.24 2004 5.78 2005 37.58 2006 18.26 2007 19.93 2008 9.13

16.63 11.73 8.48 53.32 26.62 34.15 13.95

26.72 18.65 12.26 75.48 38.60 58.02 21.08

7.9 8.5 7.5 4.3 5.4 7.3 7.2

By Proportion 2002 2003 2004 2005 2006 2007 2008

28.63 13.82 13.58 2.91 5.13 15.17 16.31

7.44 3.05 3.25 9.62 7.80 6.49 6.29

UCI

53.90 12.40 16.53 49.25 51.51 33.46 26.31

82.97 14.05 24.34 37.86 92.55 110.28 58.74

Key 4.70 1.92 2.11 6.22 4.94 3.70 3.71

Index

4.2 7.8 6.1 3.9 4.5 6.7 5.9

By Aged Sub-Sample Expansion 2002 49.95 29.91 2003 4.55 8.13 2004 14.69 8.71 2005 13.69 22.90 2006 55.06 32.59 2007 28.78 56.57 2008 34.71 20.34

By Age-Length 2002 2003 2004 2005 2006 2007 2008

LCI

Geometric Mean 2002 35.99 2003 7.18 2004 11.01 2005 34.30 2006 34.61 2007 19.48 2008 16.33

59.58 9.72 21.10 34.97 74.67 40.86 40.26

By Aged Sub-Sample Expansion 2002 0.76 1.80 2003 0.73 0.40 2004 0.49 1.10 2005 4.19 2.41 2006 1.49 2.94 2007 1.15 0.34 2008 1.39 2.70

Year

By Proportion 2002 2003 2004 2005 2006 2007 2008

18.19 9.89 5.83 50.65 24.99 28.63 13.82

12.49 18.59 5.83 22.95 13.28 13.87 10.54

9.63 4.89 6.25 1.17 2.11 5.80 5.67

3.46 1.14 1.96 6.89 5.24 2.44 4.74

22.5 19.4 23.1 12.7 16.7 30.8 16.7

By Aged Sub-Sample Expansion 2002 0.72 1.69 2003 0.69 0.38 2004 0.46 1.02 2005 3.85 2.23 2006 1.29 2.49 2007 1.03 0.30 2008 1.33 2.55

11.52 4.62 4.81 14.64 12.04 10.94 10.30

9.2 11.7 10.8 8.2 9.0 11.6 11.0

By Age-Length Key 2002 9.96 2003 9.65 2004 8.61 2005 15.48 2006 14.14 2007 4.41 2008 25.50

192

13.80 13.01 10.45 20.49 18.17 7.39 38.69

Figure 126. Abundance indices (number and biomass) for summer flounder based on geometric (A) and arithmetic (B) means.

A

B

193

Figure 127. Summer flounder age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-0 (B), age-1 (C) and age-2 (D) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐0

Age‐0

Age‐Length

Age‐Length

B

C

Age‐0

Age‐0

Expanded

Expanded

Age‐1

Age‐1

Age‐Length

Age‐Length

Age‐1

Age‐1

194

Figure 127. continued.

D

Expanded

Expanded

Age‐2

Age‐2

Age‐Length

Age‐Length

Age‐2

Age‐2

195

196

March

May

July

September

Figure 128. Abundance (kg per hectare swept) of summer flounder in Chesapeake Bay, 2002.

November

197

March

May

July

September

Figure 129. Abundance (kg per hectare swept) of summer flounder in Chesapeake Bay, 2003.

November

198

March

May

July

September

Figure 130. Abundance (kg per hectare swept) of summer flounder in Chesapeake Bay, 2004.

November

199

March

May

July

Figure 131. Abundance (kg per hectare swept) of summer flounder in Chesapeake Bay, 2005.

September

November

200

March

May

July

September

Figure 132. Abundance (kg per hectare swept) of summer flounder in Chesapeake Bay, 2006.

November

201

March

May

July

Figure 133. Abundance (kg per hectare swept) of summer flounder in Chesapeake Bay, 2007.

November

202

March

May

July

September

Figure 134. Abundance (kg per hectare swept) of summer flounder in Chesapeake Bay, 2008.

November

Expanded Number

Figure 135. Summer flounder length-frequency in Chesapeake Bay, 2002-2008.

203

Expanded Number

Figure 136. Summer flounder age-structure in Chesapeake Bay, 2002-2008.

204

Expanded Number

Figure 136. continued.

205

Figure 137. Summer flounder diet in Chesapeake Bay, 2002-2008 combined.

206

Weakfish

207

Figure 138. Weakfish minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B

208

Figure 139. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for weakfish.

A

B

209

Table 14. Abundance indices (number and biomass) for weakfish, overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

All Ages

Age 0

Age 1

Age 2

LCI

Index

By Weight UCI

Geometric Mean 2002 14.48 2003 110.35 2004 110.42 2005 157.06 2006 59.22 2007 18.68 2008 14.33

37.67 249.92 236.74 383.25 138.87 68.04 34.98

95.56 564.41 506.27 933.12 323.86 241.25 83.44

Arithmetic Mean 2002 351.18 2003 902.73 2004 791.47 2005 1,157.15 2006 502.64 2007 289.77 2008 140.62

719.92 1,265.51 1,260.59 1,670.63 813.55 751.72 380.27

1,088.66 1,628.30 1,729.71 2,184.12 1,124.47 1,213.68 619.92

By Proportion 2002 2003 2004 2005 2006 2007 2008

CV

Year

LCI

Index

UCI

CV

12.5 7.4 6.9 7.5 8.5 14.8 11.9

Geometric Mean 2002 4.64 2003 12.52 2004 22.88 2005 27.91 2006 10.84 2007 4.03 2008 3.50

10.44 25.62 42.11 58.88 20.59 11.38 6.76

22.22 51.45 76.84 123.00 38.37 29.48 12.41

14.5 10.3 7.8 8.9 9.8 17.9 13.3

25.6 14.3 18.6 15.4 19.1 30.7 31.5

Arithmetic Mean 2002 45.02 2003 100.94 2004 101.04 2005 140.91 2006 48.30 2007 29.66 2008 16.32

102.52 162.39 200.25 242.46 84.72 71.79 39.72

160.01 223.83 299.47 344.02 121.14 113.92 63.13

28.0 18.9 24.8 20.9 21.5 29.3 29.5

By Proportion 2002 2003 2004 2005 2006 2007 2008

14.70 60.12 127.24 98.82 50.35 29.54 26.92

11.55 96.50 26.30 94.20 48.13 21.37 4.08

By Aged Sub-Sample Expansion 2002 14.20 5.95 2003 28.25 66.71 2004 37.71 18.52 2005 66.11 138.87 2006 57.11 25.81 2007 15.56 53.00 2008 7.86 3.09

32.22 155.72 75.78 290.53 124.93 175.03 18.18

14.4 10.0 9.4 7.4 9.5 14.8 17.7

By Aged Sub-Sample Expansion 2002 3.01 1.54 2003 4.30 8.00 2004 3.08 1.96 2005 4.41 7.11 2006 4.72 2.85 2007 2.23 5.40 2008 0.91 0.46

5.32 14.29 4.62 11.18 7.50 11.68 1.50

16.4 12.0 11.4 9.7 11.3 18.4 20.8

By Age-Length Key 2002 5.19 2003 54.59 2004 26.36 2005 70.11 2006 25.84 2007 13.70 2008 2.95

11.83 116.97 50.95 149.08 55.78 44.78 7.43

25.58 249.35 97.65 315.77 119.11 141.60 17.01

14.3 7.9 8.1 7.5 9.3 14.9 17.8

By Age-Length 2002 2003 2004 2005 2006 2007 2008

8.81 18.97 6.38 14.39 9.72 15.91 4.29

8.8 6.7 7.0 6.1 7.3 13.2 12.8

By Proportion 2002 2003 2004 2005 2006 2007 2008

14.70 60.12 127.24 98.82 50.35 29.54 26.92

Key 3.94 8.85 3.52 7.46 4.85 4.18 1.69

By Proportion 2002 2003 2004 2005 2006 2007 2008

5.96 13.03 4.78 10.41 6.92 8.36 2.77

3.20 9.89 4.68 14.47 7.14 3.58 0.79

By Aged Sub-Sample Expansion 2002 3.59 9.96 2003 7.04 16.95 2004 33.24 70.39 2005 19.02 50.83 2006 10.08 23.89 2007 2.34 8.68 2008 4.06 10.18

25.18 39.08 147.85 133.16 54.91 27.11 23.69

18.2 13.9 8.6 12.0 12.6 23.5 16.4

By Aged Sub-Sample Expansion 2002 1.88 4.49 2003 3.02 6.07 2004 10.49 18.83 2005 6.37 13.24 2006 3.58 7.06 2007 1.25 3.67 2008 1.55 3.36

9.47 11.45 33.21 26.52 13.19 8.73 6.46

18.9 14.5 9.1 12.4 13.5 23.8 18.2

By Age-Length Key 2002 6.39 2003 25.28 2004 56.14 2005 37.35 2006 21.34 2007 5.57 2008 7.20

16.93 54.12 113.21 87.72 46.00 18.27 16.46

42.51 114.60 227.29 204.22 97.85 55.57 36.18

15.4 9.2 7.3 9.3 9.7 18.2 13.2

By Age-Length Key 2002 15.22 2003 12.23 2004 21.02 2005 17.63 2006 11.31 2007 6.18 2008 7.09

27.09 18.93 31.13 26.32 17.06 13.86 11.95

47.66 29.01 45.89 39.05 25.48 29.78 19.72

8.2 6.8 5.4 5.8 6.6 13.5 9.2

By Proportion 2002 2003 2004 2005 2006 2007 2008

29.54 26.92 6.66 78.51 57.51 162.67 30.72

By Proportion 2002 2003 2004 2005 2006 2007 2008

4.94 5.21 1.85 8.05 10.23 24.99 4.56 3.61 13.45 12.94 55.95 10.48 8.10 1.93

27.4 15.6 14.5 10.7 13.8 24.6 25.8

33.28 48.88 32.17 103.21 24.12 45.27 5.94

9.4 8.0 5.2 3.8 7.9 7.5 8.4

By Aged Sub-Sample Expansion 2002 0.89 2.86 2003 13.84 5.47 2004 6.55 15.62 2005 83.97 32.43 2006 7.45 17.28 2007 7.08 1.95 2008 0.64 1.78

6.88 33.03 35.58 215.01 38.54 21.13 3.68

26.4 15.4 14.0 10.5 13.3 24.1 25.6

By Aged Sub-Sample Expansion 2002 0.56 1.68 2003 6.67 3.07 2004 3.26 6.71 2005 26.93 12.70 2006 2.99 5.76 2007 3.39 1.12 2008 0.41 1.03

By Age-Length Key 2002 3.99 2003 19.04 2004 24.01 2005 47.65 2006 15.11 2007 3.66 2008 2.30

23.42 91.63 90.43 266.89 64.80 38.53 8.75

16.5 10.2 8.4 9.0 10.1 20.5 15.6

By Age-Length Key 2002 10.17 2003 15.90 2004 16.13 2005 53.16 2006 9.47 2007 15.99 2008 2.96

10.04 42.08 46.82 113.16 31.56 12.57 4.67

210

18.56 28.03 22.84 74.12 15.22 27.04 4.24

Figure 140. Abundance indices (number and biomass) for weakfish based on geometric (A) and arithmetic (B) means.

A

B

211

Figure 141. Weakfish age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-0 (B), age-1 (C) and age-2 (D) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐0

Age‐0

Age‐Length

Age‐Length

B

C

Age‐0

Age‐0

Expanded

Expanded

Age‐1

Age‐1

Age‐Length

Age‐Length

Age‐1

Age‐1 212

Figure 141. continued.

D

Expanded

Expanded

Age‐2

Age‐2

Age‐Length

Age‐Length

Age‐2

Age‐2

213

214

March

May

July

Figure 142. Abundance (kg per hectare swept) of weakfish in Chesapeake Bay, 2002.

September

November

215

March

May

July

Figure 143. Abundance (kg per hectare swept) of weakfish in Chesapeake Bay, 2003.

September

November

216

March

May

July

Figure 144. Abundance (kg per hectare swept) of weakfish in Chesapeake Bay, 2004.

September

November

217

March

May

July

Figure 145. Abundance (kg per hectare swept) of weakfish in Chesapeake Bay, 2005.

September

November

218

March

May

July

Figure 146. Abundance (kg per hectare swept) of weakfish in Chesapeake Bay, 2006.

September

November

219

March

May

July

Figure 147. Abundance (kg per hectare swept) of weakfish in Chesapeake Bay, 2007.

November

220

March

May

July

Figure 148. Abundance (kg per hectare swept) of weakfish in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 149. Weakfish length-frequency in Chesapeake Bay, 2002-2008.

221

Expanded Number

Figure 150. Weakfish age-structure in Chesapeake Bay, 2002-2008.

222

Expanded Number

Figure 150. continued.

223

Figure 151. Weakfish diet in Chesapeake Bay, 2002-2008 combined.

224

White Perch

225

Figure 152. White perch minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay, 2002-2008.

A

B C 226

Figure 153. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for white perch.

A

B

227

Table 15. Abundance indices (number and biomass) for white perch (March), overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

All Ages

Age 3

LCI

Index

Geometric Mean 2002 17.37 2003 23.65 2004 251.74 2005 54.70 2006 80.02 2007 492.01 2008 1,093.51

34.54 134.47 613.19 307.46 409.69 2,585.63 2,630.10

67.76 743.62 1,491.55 1,707.13 2,080.73 13,569.92 6,323.88

Arithmetic Mean 2002 0.00 2003 0.00 2004 256.54 2005 842.51 2006 0.00 2007 861.36 2008 3,236.33

2,824.79 2,209.43 4,480.66 3,448.17 10,370.24 12,919.30 6,365.58

6,451.12 4,483.73 8,704.79 6,053.83 24,327.45 24,977.24 9,494.82

By Proportion 2002 2003 2004 2005 2006 2007 2008

Age 5

CV

By Age-Length Key 2002 1.61 2003 1.55 2004 8.32 2005 4.14 2006 15.94 2007 45.78 2008

5.01 5.65 26.16 22.89 93.10 234.13

By Proportion 2002 2003 2004 2005 2006 2007 2008

2.50 15.64 155.04 36.03 23.16 780.07

Year

LCI

Index

UCI

CV

9.2 17.4 6.9 14.9 13.5 10.5 5.6

Geometric Mean 2002 7.91 2003 10.29 2004 70.25 2005 15.54 2006 21.16 2007 88.02 2008 149.87

15.29 43.10 153.17 74.28 88.65 345.93 309.63

28.79 171.26 332.58 341.68 361.72 1,351.07 638.58

10.8 18.0 7.7 17.5 15.5 11.6 6.3

64.2 51.5 47.1 37.8 67.3 46.7 24.6

Arithmetic Mean 2002 0.00 2003 83.63 2004 34.31 2005 126.72 2006 0.00 2007 209.42 2008 300.40

498.37 353.70 878.56 567.24 1,449.16 1,229.34 657.60

1,126.70 623.78 1,722.80 1,007.75 3,508.61 2,249.27 1,014.80

63.0 38.2 48.0 38.8 71.1 41.5 27.2

1.65 1.90 6.63 0.47 43.76 6.70

45.4 100.0 42.6 100.0 24.3 37.6

3.91 4.98 21.04 12.17 96.01 102.84

22.6 28.6 24.8 30.4 13.8 8.3

By Proportion 2002 2003 2004 2005 2006 2007 2008

1.84 17.49 45.90 32.95 91.59 95.83

By Aged Sub-Sample Expansion 2002 1.86 0.11 2003 0.00 0.67 2004 6.09 0.56 2005 0.00 0.25 2006 101.07 20.63 2007 0.60 7.07 2008

Age 4

By Weight UCI

6.36 3.64 31.31 0.96 480.59 39.64

45.1 100.0 38.7 100.0 16.8 38.7

12.83 16.35 78.10 110.10 521.84 1,180.88

23.2 25.3 16.2 24.2 18.9 14.8

0.82 5.60 11.47 7.96 19.82 12.82

By Aged Sub-Sample Expansion 2002 0.67 0.05 2003 0.00 0.43 2004 2.00 0.18 2005 0.00 0.14 2006 11.90 2.72 2007 0.33 2.20 2008

By Age-Length Key 2002 0.82 2003 0.63 2004 1.83 2005 0.87 2006 12.39 2007 26.73 2008

By Proportion 2002 2003 2004 2005 2006 2007 2008

1.99 2.12 6.90 3.97 35.04 52.66

1.11 5.01 38.73 8.70 5.01 104.36

By Aged Sub-Sample Expansion 2002 0.63 3.16 2003 0.00 0.00 2004 0.00 1.54 2005 0.16 7.15 2006 0.00 2.32 2007 65.07 597.26 2008

9.59 0.00 5.48 56.04 17.16 5,416.66

32.8 0.0 50.1 46.4 70.8 17.2

By Aged Sub-Sample Expansion 2002 0.30 1.28 2003 0.00 0.00 2004 0.02 0.75 2005 0.11 2.85 2006 0.00 1.17 2007 16.20 81.35 2008

2.99 0.00 2.02 12.33 5.54 393.41

34.0 0.0 48.6 46.1 71.3 17.8

By Age-Length Key 2002 2.37 2003 1.48 2004 23.21 2005 9.49 2006 2.20 2007 168.38 2008

16.14 11.29 144.94 261.73 59.07 4,767.81

20.0 23.4 11.0 20.3 27.9 12.3

By Age-Length Key 2002 0.73 2003 0.18 2004 3.62 2005 2.51 2006 3.18 2007 18.56 2008

4.53 4.54 26.88 31.57 15.35 501.10

25.8 41.2 18.5 23.5 16.1 17.7

By Aged Sub-Sample Expansion 2002 0.35 1.80 2003 0.18 0.00 2004 0.00 1.28 2005 6.23 0.59 2006 0.00 2.65 2007 4.18 0.34 2008

4.83 0.63 5.00 31.95 17.60 19.00

35.5 100.0 58.8 38.3 63.0 41.0

By Age-Length Key 2002 0.80 2003 2.04 2004 3.57 2005 4.10 2006 7.11 2007 18.66 2008

5.38 5.90 16.93 47.56 51.94 67.12

25.9 13.5 15.5 20.4 15.5 8.6

By Proportion 2002 2003 2004 2005 2006 2007 2008

6.60 4.52 58.44 51.51 12.87 897.75

By Proportion 2002 2003 2004 2005 2006 2007 2008

3.15 9.41 37.57 40.28 36.59 65.98

By Aged Sub-Sample Expansion 2002 0.79 4.20 2003 0.34 0.00 2004 0.00 2.24 2005 14.83 0.97 2006 0.00 5.73 2007 10.66 0.60 2008

14.10 1.40 11.83 125.94 57.07 83.94

32.3 100.0 58.7 37.7 56.5 40.4

By Age-Length Key 2002 2.69 2003 3.77 2004 18.24 2005 12.48 2006 10.37 2007 32.20 2008

19.40 26.79 90.55 294.89 241.16 587.68

19.8 18.0 10.4 18.6 19.3 14.6

7.68 10.51 40.97 62.15 51.47 138.79

228

2.09 1.56 10.35 9.69 7.27 98.11

1.39 3.02 9.38 9.73 7.92 8.83

2.39 3.58 8.05 14.74 19.72 35.60

Figure 154. Abundance indices (number and biomass) for white perch (March) based on geometric (A) and arithmetic (B) means.

A C

C C

B

229

Figure 155. White perch (March) age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-3 (B), age-4 (C) and age-5 (D) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐3

Age‐3

Age‐Length

Age‐Length

B

C

C C

C

Age‐3

Expanded

Expanded

C

C

Age‐3

C C

Age‐4

Age‐4

Age‐Length

Age‐Length C

C

Age‐4

Age‐4

230

Figure 155. continued.

D

Expanded

Expanded C

C C

Age‐5

Age‐Length

Age‐Length

Age‐5

Age‐5

C

Age‐5

231

Table 16. Abundance indices (number and biomass) for white perch (November), overall (calculated as geometric and arithmetic means) and by age (geometric means only, age-specific indices based on three calculation methods).

By Number Year

All Ages

Age 3

Age 4

LCI

Index

Geometric Mean 2002 3,423.04 2003 1,570.71 2004 10,477.01 2005 1,693.76 2006 1,993.28 2007 1,420.14 2008 1,223.69

8,321.84 2,099.49 18,675.01 6,349.76 6,130.12 3,517.65 3,523.12

20,229.37 2,806.16 33,287.11 23,797.09 18,848.23 8,710.94 10,139.89

Arithmetic Mean 2002 5,241.84 2003 1,921.59 2004 12,138.76 2005 192.62 2006 3,256.12 2007 1,238.42 2008 1,227.34

15,903.80 2,668.73 22,194.14 12,112.39 8,924.72 4,759.40 5,598.42

26,565.76 3,415.87 32,249.53 24,032.16 14,593.31 8,280.38 9,969.50

By Proportion 2002 2003 2004 2005 2006 2007 2008

CV

Index

UCI

4.9 1.9 2.9 7.5 6.4 5.6 6.5

Geometric Mean 2002 380.87 2003 164.74 2004 1,027.25 2005 146.72 2006 212.50 2007 137.48 2008 78.79

1,035.74 204.01 1,890.79 524.02 533.27 332.70 270.29

2,813.69 252.60 3,479.53 1,865.00 1,335.93 803.16 921.41

7.2 2.0 4.0 10.1 7.3 7.6 10.9

33.5 14.0 22.7 49.2 31.8 37.0 39.0

Arithmetic Mean 2002 558.75 2003 211.65 2004 1,181.82 2005 33.31 2006 285.83 2007 140.24 2008 48.81

2,182.67 295.89 2,263.68 963.14 744.60 428.44 536.06

3,806.58 380.13 3,345.53 1,892.97 1,203.37 716.63 1,023.30

37.2 14.2 23.9 48.3 30.8 33.6 45.4

Year

LCI

By Proportion 2002 2003 2004 2005 2006 2007 2008

443.84 273.02 1,397.97 680.49 1,370.44 130.37

CV

55.24 26.53 141.54 56.16 119.22 12.33

By Aged Sub-Sample Expansion 2002 70.52 3.51 2003 0.00 19.04 2004 112.92 1.93 2005 0.00 17.66 2006 2,687.89 977.25 2007 0.00 0.00 2008

1,132.47 4,435.18 4,424.97 624.91 7,389.88 0.00

32.4 90.1 38.6 60.0 6.4 0.0

By Aged Sub-Sample Expansion 2002 13.57 1.30 2003 0.00 4.75 2004 23.62 1.08 2005 0.00 4.39 2006 153.51 56.16 2007 0.00 0.00 2008

91.23 128.81 291.00 47.44 416.66 0.00

34.4 89.1 38.6 65.2 9.9 0.0

By Age-Length Key 2002 283.11 2003 173.90 2004 2,604.23 2005 159.41 2006 832.92 2007 135.88 2008

672.39 202.47 4,674.67 573.16 2,743.27 341.27

1,595.06 235.70 8,390.53 2,054.15 9,029.84 854.85

6.6 1.4 3.5 10.0 7.5 7.9

By Age-Length Key 2002 12.14 2003 2.06 2004 46.38 2005 5.19 2006 35.71 2007 7.98 2008

33.75 6.59 92.85 19.13 124.43 13.89

90.88 17.86 184.92 64.43 427.62 23.69

13.7 22.4 7.5 19.6 12.7 9.4

By Proportion 2002 2003 2004 2005 2006 2007 2008

601.56 244.12 4,721.84 744.11 346.48 1,061.25

By Proportion 2002 2003 2004 2005 2006 2007 2008

74.87 23.72 478.07 61.41 30.14 100.37

By Aged Sub-Sample Expansion 2002 4.82 105.78 2003 141.94 314.28 2004 54.55 1,123.08 2005 2.37 66.95 2006 0.00 5.43 2007 115.85 446.30 2008

Age 5

By Weight UCI

By Age-Length Key 2002 349.11 2003 311.02 2004 2,474.85 2005 309.19 2006 48.82 2007 588.45 2008

840.41 344.73 4,388.15 1,009.19 187.74 1,386.97

By Proportion 2002 2003 2004 2005 2006 2007 2008

758.09 146.93 1,144.08 831.80 547.46 89.76

1,956.77 694.42 22,746.01 1,368.80 117.12 1,711.31

31.1 6.9 21.4 35.6 78.2 11.0

By Aged Sub-Sample Expansion 2002 1.90 18.63 131.77 2003 11.30 24.07 50.10 2004 14.82 145.13 1,349.06 2005 0.43 10.57 92.45 2006 0.00 2.42 21.99 2007 8.41 36.46 148.16 2008

32.1 11.1 22.3 42.7 77.5 19.1

2,021.16 382.08 7,780.03 3,288.88 714.03 3,267.23

6.5 0.9 3.4 8.5 12.7 5.9

By Age-Length Key 2002 14.71 2003 5.12 2004 70.46 2005 11.70 2006 3.10 2007 34.19 2008

39.53 11.63 122.02 41.13 11.50 53.06

103.55 25.07 210.77 138.73 37.07 82.05

12.8 14.3 5.6 16.0 22.0 5.4

By Proportion 2002 2003 2004 2005 2006 2007 2008

94.35 14.28 115.83 68.64 47.62 8.49

By Aged Sub-Sample Expansion 2002 8.73 47.16 2003 0.51 0.00 2004 0.00 0.28 2005 38.93 2.49 2006 0.37 16.15 2007 0.32 0.00 2008

237.38 1.29 1.12 456.20 214.44 1.30

20.6 50.6 100.0 33.1 44.5 100.0

By Age-Length Key 2002 21.87 2003 2.86 2004 21.31 2005 14.71 2006 7.48 2007 3.82 2008

139.27 7.74 77.17 142.74 136.18 14.53

11.2 11.6 8.4 14.3 19.7 13.5

By Aged Sub-Sample Expansion 2002 32.61 344.05 2003 0.80 0.00 2004 0.00 0.42 2005 234.38 8.21 2006 0.52 70.45 2007 0.56 0.00 2008

3,541.40 2.24 1.87 6,017.67 3,363.97 2.78

19.9 50.0 100.0 29.7 45.1 100.0

By Age-Length Key 2002 466.53 2003 96.20 2004 804.73 2005 266.76 2006 139.33 2007 40.60 2008

2,617.09 123.10 2,561.78 2,480.69 2,227.46 607.47

6.1 1.3 4.0 8.3 10.9 13.2

1,105.36 108.83 1,435.98 814.17 558.22 158.10

232

55.64 4.81 40.76 46.52 33.11 7.65

Figure 156. Abundance indices (number and biomass) for white perch (November) based on geometric (A) and arithmetic (B) means.

A

B

233

Figure 157. White perch (November age-specific geometric mean abundance indices (number and biomass) based on age proportion of geometric mean total abundance (A) and based on expansion of aged samples and on age-length keys for age-3 (B), age-4 (C) and age-5 (D) specimens.

A

Proportion

Proportion

Expanded

Expanded

Age‐3

Age‐3

Age‐Length

Age‐Length

B

C C

C C

Age‐3

Age‐3

Expanded

Expanded C

C C

Age‐4

Age‐Length

Age‐Length

Age‐4

Age‐4

C

Age‐4

234

Figure 157. continued.

D

Expanded

Expanded

C C

Age‐5

Age‐5

Age‐Length

Age‐Length

Age‐5

Age‐5

235

236

March

May

July

Figure 158. Site-specific white perch abundance (number per hectare swept), 2002.

September

November

237

March

May

July

Figure 159. Site-specific white perch abundance (number per hectare swept), 2003.

September

November

238

March

May

July

Figure 160. Site-specific white perch abundance (number per hectare swept), 2004.

September

November

239

March

May

July

Figure 161. Site-specific white perch abundance (number per hectare swept), 2005.

September

November

240

March

May

July

Figure 162. Site-specific white perch abundance (number per hectare swept), 2006.

September

November

241

March

May

July

Figure 163. Abundance (number per hectare swept) of white perch in Chesapeake Bay, 2007.

November

242

March

May

July

Figure 164. Abundance (kg per hectare swept) of white perch in Chesapeake Bay, 2008.

September

November

Expanded Number

Figure 165. White perch length-frequency in Chesapeake Bay, 2002-2008.

243

Expanded Number

Figure 166. White perch age-structure in Chesapeake Bay, 2002-2007.

244

Expanded Number

Figure 166. continued.

245

Figure 167. White perch diet in Chesapeake Bay, 2002-2008 combined.

246

Water Temperature

247

248

March

Figure 168. Surface temperature in Chesapeake Bay, 2002.

July

September

November

249

March

Figure 169. Bottom temperature in Chesapeake Bay, 2002.

July

September

November

250

March

May

Figure 170. Surface temperature in Chesapeake Bay, 2003.

July

September

November

251

March

May

Figure 171. Bottom temperature in Chesapeake Bay, 2003.

July

September

November

252

March

May

Figure 172. Surface temperature in Chesapeake Bay, 2004.

July

September

November

253

March

May

Figure 173. Bottom temperature in Chesapeake Bay, 2004.

July

September

November

254

March

May

Figure 174. Surface temperature in Chesapeake Bay, 2005.

July

September

November

255

March

May

Figure 175. Bottom temperature in Chesapeake Bay, 2005.

July

September

November

256

March

May

Figure 176. Surface temperature in Chesapeake Bay, 2006.

July

September

November

257

March

May

Figure 177. Bottom temperature in Chesapeake Bay, 2006.

July

September

November

258

March

May

Figure 178. Surface temperature in Chesapeake Bay, 2007.

July

November

259

March

May

Figure 179. Bottom temperature in Chesapeake Bay, 2007.

July

November

260

March

May

Figure 180. Surface temperature in Chesapeake Bay, 2008.

July

September

November

261

March

May

Figure 181. Bottom temperature in Chesapeake Bay, 2008.

July

September

November

262

Salinity

263

264

March

Figure 182. Surface salinity in Chesapeake Bay, 2002.

July

September

November

265

March

Figure 183. Bottom salinity in Chesapeake Bay, 2002.

July

September

November

266

March

May

Figure 184. Surface salinity in Chesapeake Bay, 2003.

July

September

November

267

March

May

Figure 185. Bottom salinity in Chesapeake Bay, 2003.

July

September

November

268

March

May

Figure 186. Surface salinity in Chesapeake Bay, 2004.

July

September

November

269

March

May

Figure 187. Bottom salinity in Chesapeake Bay, 2004.

July

September

November

270

March

May

Figure 188. Surface salinity in Chesapeake Bay, 2005.

July

September

November

271

March

May

Figure 189. Bottom salinity in Chesapeake Bay, 2005.

July

September

November

272

March

May

Figure 190. Surface salinity in Chesapeake Bay, 2006.

July

September

November

273

March

May

Figure 191. Bottom salinity in Chesapeake Bay, 2006.

July

September

November

274

March

May

Figure 192. Surface salinity in Chesapeake Bay, 2007.

July

November

275

March

May

Figure 193. Bottom salinity in Chesapeake Bay, 2007.

July

November

276

March

May

Figure 194. Surface salinity in Chesapeake Bay, 2008.

July

September

November

277

March

May

Figure 195. Bottom salinity in Chesapeake Bay, 2008.

July

September

November

278

Dissolved Oxygen

279

280

March

July

Figure 196. Surface dissolved oxygen in Chesapeake Bay, 2002.

September

November

281

March

July

Figure 197. Bottom dissolved oxygen in Chesapeake Bay, 2002.

September

November

282

March

May

July

Figure 198. Surface dissolved oxygen in Chesapeake Bay, 2003.

September

November

283

March

May

July

Figure 199. Bottom dissolved oxygen in Chesapeake Bay, 2003.

September

November

284

March

May

July

Figure 200. Surface dissolved oxygen in Chesapeake Bay, 2004.

September

November

285

March

May

July

Figure 201. Bottom dissolved oxygen in Chesapeake Bay, 2004.

September

November

286

March

May

July

Figure 202. Surface dissolved oxygen in Chesapeake Bay, 2005.

September

November

287

March

May

July

Figure 203. Bottom dissolved oxygen in Chesapeake Bay, 2005.

September

November

288

March

May

July

Figure 204. Surface dissolved oxygen in Chesapeake Bay, 2006.

September

November

289

March

May

July

Figure 205. Bottom dissolved oxygen in Chesapeake Bay, 2006.

September

November

290

March

May

July

Figure 206. Surface dissolved oxygen in Chesapeake Bay, 2007.

November

291

March

May

July

Figure 207. Bottom dissolved oxygen in Chesapeake Bay, 2007.

November

292

March

May

July

Figure 208. Surface dissolved oxygen in Chesapeake Bay, 2008.

September

November

293

March

May

July

Figure 209. Bottom dissolved oxygen in Chesapeake Bay, 2008.

September

November

294

Appendix 1 Blue Crab and Clearnose Skate Abundance

295

Figure A1. Male blue crab minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay 2002-2008.

A

B

296

Figure A2. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for male blue crab.

A

B

297

Table A1. Abundance indices (number and biomass) for male blue crab, overall (calculated as geometric and arithmetic means).

By Number Year

LCI

Index

By Weight UCI

CV

Year

All Ages Geometric Mean

LCI

6.23 6.71 3.33 8.70 12.78 2.88 11.63

10.57 10.36 5.38 14.64 19.52 6.75 18.58

17.50 15.72 8.39 24.23 29.57 14.48 29.35

9.6 8.0 10.4 8.7 6.6 16.9 7.4

Geometric Mean 2002 2.27 2003 2.33 2004 1.43 2005 3.28 2006 3.98 2007 1.27 2008 4.01

Arithmetic Mean 2002 99.56 2003 75.44 2004 42.18 2005 106.49 2006 141.54 2007 30.17 2008 0.00

137.46 111.66 66.95 208.37 199.77 56.68 260.89

175.36 147.87 91.72 310.26 257.99 83.20 522.51

13.8 16.2 18.5 24.4 14.6 23.4 50.1

Arithmetic Mean 2002 14.80 2003 11.34 2004 6.72 2005 19.27 2006 19.67 2007 4.94 2008 0.79

2002 2003 2004 2005 2006 2007 2008

298

Index

UCI

CV

3.40 3.37 2.11 4.97 5.45 2.61 5.74

4.92 4.75 2.97 7.32 7.34 4.74 8.08

10.0 9.3 10.8 9.3 6.9 18.1 7.8

21.06 17.18 11.79 39.54 27.56 10.23 41.70

27.31 23.01 16.86 59.81 35.45 15.51 82.61

14.9 17.0 21.5 25.6 14.3 25.8 49.1

Figure A3. Abundance indices (number and biomass) for male blue crabs based on geometric (A) and arithmetic (B) means.

A

B

299

300

March

May

July

Figure A4. Abundance (kg per hectare swept) of male blue crab in Chesapeake Bay, 2002.

September

November

301

March

May

July

Figure A5. Abundance (kg per hectare swept) of male blue crab in Chesapeake Bay, 2003.

September

November

302

March

May

July

Figure A6. Abundance (kg per hectare swept) of male blue crab in Chesapeake Bay, 2004.

September

November

303

March

May

July

Figure A7. Abundance (kg per hectare swept) of male blue crab in Chesapeake Bay, 2005.

September

November

304

March

May

July

Figure A8. Abundance (kg per hectare swept) of male blue crab in Chesapeake Bay, 2006.

September

November

305

March

May

July

Figure A9. Abundance (kg per hectare swept) of male blue crab in Chesapeake Bay, 2007.

November

306

March

May

July

Figure A10. Abundance (kg per hectare swept) of male blue crab in Chesapeake Bay, 2008.

September

November

Figure A11. Mature female blue crab minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay 2002-2008.

307

Figure A12. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for mature female blue crab.

A

B

308

Table A2. Abundance indices (number and biomass) for mature female blue crab, overall (calculated as geometric and arithmetic means).

By Number Year

LCI

Index

By Weight UCI

CV

Year

All Ages Geometric Mean

LCI

4.43 21.35 11.31 43.13 69.77 6.14 394.22

21.32 57.50 39.42 139.51 238.13 25.47 668.82

90.84 152.13 131.70 446.38 807.04 97.05 1,134.20

22.8 11.8 16.1 11.7 11.1 20.0 4.1

Geometric Mean 2002 1.92 2003 2.44 2004 3.97 2005 12.05 2006 17.01 2007 2.51 2008 53.62

Arithmetic Mean 2002 0.00 2003 198.90 2004 69.71 2005 342.82 2006 345.69 2007 35.03 2008 961.56

492.33 350.12 407.89 925.16 673.94 290.00 1,618.83

997.98 501.33 746.06 1,507.49 1,002.20 544.97 2,276.10

51.4 21.6 41.5 31.5 24.4 44.0 20.3

Arithmetic Mean 2002 0.00 2003 17.65 2004 11.51 2005 55.91 2006 48.05 2007 5.80 2008 127.55

2002 2003 2004 2005 2006 2007 2008

309

Index

UCI

CV

7.04 6.44 10.56 29.91 42.78 7.61 93.35

21.12 15.10 25.90 72.21 105.43 20.08 161.98

24.3 19.2 17.2 12.6 11.8 20.8 6.0

67.75 43.76 55.66 128.91 92.77 39.37 228.82

137.92 69.88 99.80 201.92 137.48 72.94 330.10

51.8 29.8 39.7 28.3 24.1 42.6 22.1

Figure A13. Abundance indices (number and biomass) for mature female blue crabs based on geometric (A) and arithmetic (B) means.

A

B

310

311

March

May

July

September

Figure A14. Abundance (kg per hectare swept) of mature female blue crab in Chesapeake Bay, 2002.

November

312

March

May

July

September

Figure A15. Abundance (kg per hectare swept) of mature female blue crab in Chesapeake Bay, 2003.

November

313

March

May

July

September

Figure A16. Abundance (kg per hectare swept) of mature female blue crab in Chesapeake Bay, 2004.

November

314

March

May

July

September

Figure A17. Abundance (kg per hectare swept) of mature female blue crab in Chesapeake Bay, 2005.

November

315

March

May

July

September

Figure A18. Abundance (kg per hectare swept) of mature female blue crab in Chesapeake Bay, 2006.

November

316

March

May

July

Figure A19. Abundance (kg per hectare swept) of mature female blue crab in Chesapeake Bay, 2007.

November

317

March

May

July

September

Figure A20. Abundance (kg per hectare swept) of mature female blue crab in Chesapeake Bay, 2008.

November

Figure A21. Clearnose skate minimum trawlable abundance estimates in numbers (A) and biomass (B) in Chesapeake Bay 2002-2008.

A

B

318

Figure A22. Comparison of ChesMMAP catch rates by year, cruise, and region (A) and year, cruise, and depth stratum (B) for clearnose skate.

A

B

319

Table A3. Abundance indices (number and biomass) for clearnose skate, overall (calculated as geometric and arithmetic means).

By Number Year

LCI

Index

By Weight UCI

CV

Year

All Ages Geometric Mean

LCI

1.93 2.31 0.56 1.69 8.34 3.86 3.02

3.82 4.51 1.34 3.51 16.60 9.04 6.26

6.92 8.16 2.49 6.56 32.18 19.75 12.08

15.8 14.9 23.7 17.2 11.1 15.7 14.9

Geometric Mean 2002 2.18 2003 2.50 2004 0.61 2005 1.82 2006 10.12 2007 4.64 2008 3.61

Arithmetic Mean 2002 24.26 2003 20.20 2004 0.00 2005 23.06 2006 101.94 2007 22.45 2008 38.56

57.81 52.66 47.36 49.69 169.05 228.46 103.84

91.37 85.13 105.76 76.31 236.16 434.47 169.13

29.0 30.8 61.7 26.8 19.8 45.1 31.4

Arithmetic Mean 2002 36.54 2003 33.50 2004 0.00 2005 34.79 2006 140.95 2007 79.46 2008 71.38

2002 2003 2004 2005 2006 2007 2008

320

Index

UCI

CV

4.46 5.05 1.46 3.90 20.89 11.11 7.76

8.35 9.45 2.76 7.52 42.11 24.97 15.68

15.9 15.2 23.6 17.4 11.0 15.3 14.8

92.60 65.39 62.35 70.04 235.99 277.82 162.84

148.66 97.29 136.46 105.29 331.03 476.18 254.30

30.3 24.4 59.4 25.2 20.1 35.7 28.1

Figure A23. Overall abundance indices (number and biomass) for clearnose skate based on geometric (A) and arithmetic (B) means.

A

B

321

322

March

May

July

Figure A24. Abundance (kg per hectare swept) of clearnose skate in Chesapeake Bay, 2002.

September

November

323

March

May

July

Figure A25. Abundance (kg per hectare swept) of clearnose skate in Chesapeake Bay, 2003.

September

November

324

March

May

July

Figure A26. Abundance (kg per hectare swept) of clearnose skate in Chesapeake Bay, 2004.

September

November

325

March

May

July

Figure A27. Abundance (kg per hectare swept) of clearnose skate in Chesapeake Bay, 2005.

September

November

326

March

May

July

Figure A28. Abundance (kg per hectare swept) of clearnose skate in Chesapeake Bay, 2006.

September

November

327

March

May

July

Figure A29. Abundance (kg per hectare swept) of clearnose skate in Chesapeake Bay, 2007.

November

328

March

May

July

Figure A30. Abundance (kg per hectare swept) of clearnose skate in Chesapeake Bay, 2008.

September

November

Appendix 2 Use of Yield-Per-Recruit and Egg-Per-Recruit Models to Assess Current and Alternate Management Strategies for the Summer Flounder Recreational Fishery in Virginia: An Application of Data Collected by the ChesMMAP Trawl Survey

Introduction Summer flounder (Paralichthys dentatus) are found along the eastern seaboard of North America from Nova Scotia to Florida, and are most abundant between Massachusetts and North Carolina (Ginsberg 1952, Leim and Scott 1966, Gutherz 1967).

This species supports valuable commercial and recreational fisheries throughout southern New England and the Mid-Atlantic Bight, which includes Virginiaâ&#x20AC;&#x2122;s waters. With respect to the summer flounder recreational fishery, Virginia has historically ranked third, behind only New Jersey and New York, in terms of annual landings by weight.

Approximately 90% of the summer flounder recreational harvest in Virginia is taken from Chesapeake Bay, and within this estuary recreational landings of flounder far exceed the commercial harvest of this species (Pers. comm. from the National Marine Fisheries Service, Fisheries Statistics Division).

The U.S. Atlantic coast stock of summer flounder was declared overfished in 2000, and the original stock rebuilding deadline of 2010 was extended to 2013 with the 2006 reauthorization of the Magnuson Stevens Fishery Conservation and Management Act (MSFCMA) (Public Law 94-265, NEFSC 2008). This stock is currently managed through total allowable landings (TAL), with 60% of the annual quota allocated to the commercial fishery and 40% to the recreational. Summer flounder TAL has been reduced dramatically in recent years as pressure has mounted to rebuild this stock by the aforementioned deadline. The most recent stock assessment indicated that overfishing of

329

this stock is not occurring and that the spawning stock biomass (SSB) of summer flounder is currently at 73% of the target level (NEFSC 2008).

Virginia has traditionally used minimum legal harvest sizes and possession limits to control effort and landings in its summer flounder recreational fishery. As TAL, and in turn recreational quotas, has tightened in recent years, minimum legal harvest sizes for flounder taken from Virginia waters by recreational fishermen have typically increased (Figure 1). Because summer flounder have been shown to exhibit sexually dimorphic growth patterns (most fish greater than 17â&#x20AC;? total length are female) both in Chesapeake Bay and the nearshore ocean waters of Southern New England and the Mid-Atlantic Bight (Figure 2a.,b.), questions have been raised as to whether the implementation of relatively large minimum size limits, and therefore the restriction of fishing pressure almost exclusively to the larger, breeding females, is a sound management strategy given stock rebuilding needs. Further, shore-based recreational fishermen have claimed that these increases in minimum harvest sizes violate National Standard 4 of the MSFCMA (i.e., â&#x20AC;&#x153;allocations must be fair and equitable to all fishermenâ&#x20AC;?) since large flounder tend to inhabit deeper waters and therefore are relatively unavailable close to the shore. Based on these concerns, an assessment of current and alternate management strategies for the summer flounder recreational fishery in Virginia is warranted.

Yield-per-recruit (YPR) and egg-per-recruit (EPR) models have been used as measures of harvest and egg production, respectively, in previous investigations designed to assess the effects of various management strategies on fishery yields and stock size (egg production assumed proportional to stock size) (Prager et al. 1987, Barbieri et al.

1997, Olney and Hoenig 1999, Piner and Jones 2004). Specifically, it has been assumed

330

that management options that result in greater egg production (EPR) at a given level of harvest (YPR) should result in an increase in stock size (while maintaining harvest) and therefore be more compatible with rebuilding, while those that produce a larger YPR at a given level of egg production should provide a greater benefit to the fishery in terms of harvest while maintaining equivalent stock size and rebuilding potential.

In this segment of the report, we use data on summer flounder collected by the ChesMMAP Trawl Survey from 2002 to 2007 along with YPR and EPR models in an effort to: 1) evaluate the compatibility of the current Virginia strategy of increasing minimum legal size limits for the summer flounder recreational fishery with stock rebuilding needs; and 2) assess the rebuilding potential of a combination slot and trophy size limit for this fishery relative to the 2008 minimum legal harvest size.

Harvest trade-offs required to implement the slot/trophy option while maintaining equivalent egg production (stock size and rebuilding potential) are also explored.

Methods Model Definition and Parameterization Equilibrium YPR Definition An equilibrium YPR model was used to calculate harvest (in terms of weight kg)-per-recruit at a given instantaneous rate of fishing mortality (F) for a summer

331

flounder population at equilibrium under various management scenarios for the Virginia recreational fishery (Olney and Hoenig 1999). The model is defined by

A

YPRF =

S

∑∑ N a =1 s =1

*Wa , s*

a ,s

(

− M s −(F*sela , s ) F*sela , s * 1− e M s + (F*sela , s )

2000

) ,

(1)

where Ms is the instantaneous rate of natural mortality for summer flounder of sex s (i.e., male or female), Wa,s is the average weight (kg) of a summer flounder of age a, sex s, sela,s is the relative selectivity of the fishing gear (hook and line, in this case) for age a,

sex s, and where

N a , s = N ( a −1), s * e

− M s − ( F * sel ( a −1 ),s )

.

For each management scenario, harvest-per-recruit was calculated over a range of F. The various management measures were represented by manipulating the sela,s term.

That is, as the legal harvest size for the summer flounder recreational fishery changed, the size, and therefore age, of the fish exposed to the fishery (selected by the gear) changed.

For the purposes of this study, it was assumed that all fish of legal size were equally vulnerable to capture by the recreational gear, while those not of legal size were unavailable for harvest (i.e., had to be released if captured and no mortality due to capture). This assumption results in a knife-edge selection curve for the gear. Also, while number of recruits were set as 1000 male (N0,MAL) and 1000 female (N0,FEM) for this investigation, any initial number of recruits would have been acceptable as yield was

332

calculated on a per-recruit basis. The remaining terms were either taken from the primary literature or obtained through data on summer flounder collected by the ChesMMAP Trawl Survey. Because the majority of the summer flounder recreational fishery in Virginia occurs within the ChesMMAP survey area, and approximately 85% of the annual summer flounder catch by the ChesMMAP Trawl Survey is taken from the Virginia portion of the bay, the flounder data collected by this program represent the population available to this fishery. The parameterization of these remaining terms is described below, and it should be noted that these terms were estimated separately for males and females as maximum age and growth rate have been observed to differ between sexes for summer flounder (Smith and Daiber 1977, Bonzek et al. 2007, Bonzek et al. 2008).

Parameterization

Instantaneous rate of natural mortality (Ms): Estimates of Ms were generated by combining sex-specific observations of summer flounder maximum age with Hoenigâ&#x20AC;&#x2122;s (1983) relationship between maximum age and mortality. The maximum age estimate used for male summer flounder was 10 years, yielding an MMAL of 0.44; females live to 20 years, resulting in an MFEM of 0.22 (Terceiro 2002, Brust 2007, ChesMMAP unpbl. data).

Weight at age (Wa,s): Estimates of summer flounder weight at age by sex (Wa,s) were obtained by combining sex-specific length at age growth models with sex-specific weight at length relationships for flounder. Specifically, for each age, summer flounder length on August 1 (the annual midpoint and peak of the summer flounder recreational fishery in Virginia) was combined with the weight at length relationships to generate the Wa,s term

333

for the YPR model used in this study. All individual length, weight, and age data for summer flounder inhabiting the Virginia portion of Chesapeake Bay were collected by the ChesMMAP Trawl Survey from 2002 to 2007. The collection of individual length and weight data from summer flounder is described earlier in this report.

For ageing, the right sagittal otolith was used to determine the age of each flounder sampled for full processing (described earlier in the report) by the ChesMMAP Survey. Sample preparation followed the protocols outlined in Sipe and Chittenden (2001). Specifically, a thin transverse section was cut through the nucleus of an otolith and the resulting section was mounted on a glass slide. Annuli were counted as opaque bands when viewed under a dissecting microscope using transmitted light. Annuli counts, date of capture, and the standard January 1 birthdate, were used to assign fractional ages to each specimen. The choice of birthdate used to assign fractional ages does not affect the results of the investigation. That is, a November 1 birthdate, which represents the approximate peak of the summer flounder spawning season, would have yielded identical results with respect to YPR and EPR. Length at age

Following the assignment of fractional ages, it was necessary to identifying the model that best described the length at age relationship for summer flounder. This was accomplished by fitting a set of candidate models to these data and applying model selection procedures to identify the most parsimonious explanation of the data (Burnham and Anderson 2002). Since the competing models were not hierarchical, the Akaike Information Criterion (AIC) was used for model selection (Yamaoka et al. 1978). Again, models fitting and selection occurred separately for males and females.

334

With respect to the candidate models, the von Bertalanffy growth equation was fitted to the summer flounder age/length data:

La = L∞ (1 − e − k ( a −a0 ) ) ,

(2)

where L∞ is the asymptotic length, k is the instantaneous growth coefficient, and a0 is the hypothetical age at which the fish would be zero length.

The second alternative model considered was the Richards (1959) model:

(

La = L∞ 1 − δe − k ( a −a0 )

)

1

δ

,

(3)

where δ ≠ 0. This model was chosen primarily because of its flexibility.

The final alternative model tested was the sine wave growth von Bertalanffy length-at-age model (Pitcher and MacDonald 1973):

(

)

La = L∞ exp 1 − e ( −( C sin( 2π *( a − s1 ))+ k ( a −a0 ) ,

(4)

where C is a constant that controls the magnitude of the within-year growth oscillations and s1 controls the starting point of the sine. This model allows for smooth changes in growth rate, with growth rate increasing to a maximum in mid-season.

Parameter estimates for each of these models were obtained using nonlinear regression techniques, which require the following general assumptions; 1) the expected

335

value of εi, the error term associated with the ith observation, is equal to zero, 2) the εi are independent, identically distributed normal random variables, and 3) the variance of εi is constant regardless of the value of the independent variable.

Visual inspection of the εi showed that approximately 50% were negative for each sex implying that assumption (1) was reasonable. The null hypothesis that the εi were normally distributed was not rejected for the majority of the age groups for both sexes (Kolomogorov-Smirnov test, p >0.05). The age groups where the test for normality failed were generally those with the smallest number of length observations (i.e., the older ages). Hence, assumption (2) was adopted given the robustness of regression methods to failures of this assumption and the belief that with increased sample sizes of these age groups, the associated length data would follow a normal distribution.

Assumption (3) did not hold (homogeneity of variance test, p < 0.05) for the males or females, which presented a choice to either assume a multiplicative error structure or adjust for heteroscedasity. We opted to invoke the method of weighted least squares (WSS) for parameter estimation under the assumption of an additive error structure since visual inspection of the residuals for each sex showed only a marginal increase in variance about the von Bertalanffy growth curve. Implicit in the use of WSS is the notion that the variance of εi is a function of age and that the values of that function are known, at least up to a constant of proportionality. The weighting factor was assumed to be the inverse of the number of length observations at each age value.

According the AIC statistics, the five parameter model developed by Pitcher and MacDonald (1973) provided the best explanation of the length/age relationship for each sex, followed by the von Bertalanffy growth equation. The Richards (1959) model

336

provided the poorest fit of the three. As a result, the Pitcher and MacDonald (1973) growth model was used to model summer flounder length at age by sex for this study (Figure 3).

Weight at length

With respect to the estimation of summer flounder weight at length by sex, the power function was fitted to the flounder length/weight data:

W i = ÎąLbi ,

(5)

where Îą determines the steepness of the slope and b scales the height of the curve (Quinn and Deriso 1999).

An alternative model considered was the exponential function:

W i = K 1e K 2 Li ,

(6)

where K1 scales the y-axis intercept and K2 determines the steepness of the curve.

Again, parameter estimates for all models were obtained using nonlinear regression techniques, which require the same general assumptions as outlined above for the length at age models. Visual inspection of the Îľi showed that approximately 50% were negative for each sex implying that assumption (1) was reasonable. As with the age/length analysis, instances where the weight at length data were not normally distributed for males or females generally occurred when sample sizes were low. Hence, assumption (2) was adopted under the logic described above. Again, assumption (3) did

337

not hold for either sex (homogeneity of variance test, p < 0.05), however, with no appreciable increase in variance about the power function, WSS assuming an additive error structure was used to derive parameter estimates. Here, the weighting factor was the inverse of the number of weight observations at each length value. Overall, the traditional power model provided the best overall description of the weight at length data for both males and females according to the AIC statistics (Figure 4).

Equilibrium EPR Definition

The equilibrium EPR model used to investigate egg production-per-recruit (and therefore relative stock size and rebuilding potential) at a given instantaneous rate of fishing mortality (F) for a summer flounder population at equilibrium under various management scenarios for the Virginia recreational fishery is defined by

A

EPRF =

∑N a =1

a , FEM

* E a , FEM * Pa , FEM

2000

,

(7)

where Ea,FEM is the fecundity of a female summer flounder at age a, Pa,FEM is the proportion of females mature at age a, and where

N a , FEM = N ( a −1),FEM * e

− M FEM − ( F * sel ( a −1 ),FEM )

.

For each management scenario, EPR was calculated over a range of F. Again, the various management measures were represented by manipulating the sela,s term, and the

338

number of recruits were set as 1000 male (N0,MAL) and 1000 female (N0,FEM). Although males do not produce eggs and could have been excluded from this calculation, they were included in the initial number as they count as recruits to the population. It should be noted, however, that while the exclusion of male recruits from this model would have affected the absolute values of egg production-per-recruit, the relative EPR across management scenarios would not have changed (i.e., exclusion of males would have lead to a doubling of all EPR values calculated in this investigation, as the denominator in Equation (7) would have been 1000). The remaining terms were either taken from the primary literature or obtained through data on summer flounder collected by the ChesMMAP Trawl Survey, and the parameterization of these terms is described below.

Parameterization

Fecundity at age (Ea,FEM): The fecundity of a female summer flounder at age a was calculated by combining a fecundity at length model with the female length at age model described earlier. Specifically, fecundity at length was taken from the primary literature (Morse 1981). By combining this relationship with the La,FEM term taken from Equation (4) above for female summer flounder, fecundity at age was given by

E a , FEM = 7.7975 x10 â&#x2C6;&#x2019;4 â&#x2C6;&#x2014; L3a.,402 FEM .

It should be noted that the La,FEM term was obtained by calculating female length on November 1 for each age using the seasonal growth model, as this date represents the peak of the summer flounder spawning season.

339

(8)

Proportion mature at age (Pa,FEM): Binary logistic regression was used to determine the proportion of female summer flounder mature at age a (Pa,FEM). Each flounder sampled by the ChesMMAP Trawl Survey for full processing (described elsewhere in the report) was assigned a zero if the fish was immature and a one if it was mature. These data were then fitted using the logit function by

Logit ( p ) = β + α * a ,

(9)

where β is the intercept term and α is the coefficient of the independent variable (age).

This relationship was then used to determine the proportion of female summer flounder mature at age a (Figure 5).

Transitional YPR As noted above, the equilibrium YPR model can be used to determine harvestper-recruit for a population at equilibrium. The U.S. Atlantic coast stock of summer flounder is currently in the rebuilding phase, however, so it is unlikely that this stock is in equilibrium. Further, non-equilibrium situations are likely created whenever any changes to harvest restrictions are implemented, even for a population at equilibrium. The results generated by the equilibrium YPR model should therefore be interpreted as a long-term perspective of what can be expected in terms of harvest-per-recruit under each management scenario (i.e., yield once the population reaches equilibrium under a given harvest strategy). Unfortunately, the equilibrium YPR does not provide insight into the short-term impacts of a particular management measure on yield. Transitional (i.e., nonequilibrium) YPR does provide this information, however.

340

The transitional YPR model follows the equilibrium YPR model given in Equation (4); model inputs include sela,s, Ms, and Wa,s as defined above. Rather than setting the number of recruits at some arbitrary number (e.g., 1000 male and 1000 female recruits), however, and generating the population structure based on an equilibrium assumption (Table 1a.), initial population structure is based on the relative abundances of the various age-classes (i.e., abundance of an age-class is given in relation to the other age-classes) in the population at the time at which a particular management option is implemented. For this investigation, the relative abundances of the age-classes of summer flounder in the Virginia portion of Chesapeake Bay were generated using agefrequency data for summer flounder collected by the ChesMMAP Trawl Survey. This non-equilibrium population structure is then projected into the future under a given F and management scenario (represented by the sela,s term) until an equilibrium population structure is attained (Table 1b. - number of years to equilibrium is equivalent to the number of age-classes in the population). A YPR is generated for each year in the projection, providing information on short-term harvest, while the YPR of the final year in the projection (when the population has reached equilibrium) is equivalent to the YPR that would be generated from Equation (4) using the same F. Transitional EPR While the equilibrium EPR provides information regarding egg production (and it is assumed, relative stock size) on more of a long-term scale, it fails to convey short-term information for non-equilibrium populations. A transitional (non-equilibrium) EPR model, however, does produce this information. The transitional EPR follows Equation (7), as Ea,FEM and Pa, FEM are included in this non-equilibrium model. Again, rather than

341

starting with an arbitrary number of recruits and generating a population structure based on an equilibrium assumption (Table 1a.), the initial population structure is constructed using the relative abundances of the various age-classes in the population at the time at which a particular management option is implemented (Table 1b). Age-frequency data for summer flounder collected by the ChesMMAP Trawl Survey were used to represent initial population structures for the non-equilibrium EPR. Similar to the approach taken with the transitional YPR model, the non-equilibrium population structure is then projected into the future under a given F and management scenario (represented by the sela,s term) until an equilibrium population structure is attained. An EPR is generated for

each year in the projection, providing information as to how egg production (and therefore stock size) would be impacted in the short-term, while the EPR of the final year in the projection (when the population has reached equilibrium) is equal to the EPR that would be generated from Equation (7) using the same F.

Assessment of Current Management Strategies

Equilibrium YPR and EPR models were used to assess the compatibility of Virginia’s current management strategy for its recreational summer flounder fishery, increasing minimum legal harvest size, with coastwide stock rebuilding needs.

Specifically, summer flounder equilibrium YPR and EPR were calculated for a range of F (i.e., 0.0, 0.1, 0.2. 0.28, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5

yr-1) for each of the minimum legal harvest sizes implemented since 2005 (i.e., 16.5” in 2005 & 2006, 18.5” in 2007, and 19” in 2008). We chose to evaluate the compatibility of the Commonwealth’s current management strategy with rebuilding goals beginning with

342

the 2005 fishing season, since quotas have consistently tightened (and, in turn, minimum sizes have steadily increased) since this time as pressure has mounted to rebuild by the 2013 deadline. This approach supported an evaluation of relative egg production (and therefore relative stock size) under each of the minimum legal harvest sizes at various levels of harvest (YPR), of relative harvest levels across these management scenarios at equivalent levels of egg production, and of relative egg production and harvest for each minimum size regulation at particular levels of F (which is assumed to be proportional to effort).

The short-term effects each of these management measures were evaluated by projecting a non-equilibrium population structure to equilibrium and calculating YPR and EPR for each year from the time at which a particular management option was implemented to that at which the population reached equilibrium. Because each projection is made for a particular F (rather than over a range of F as seen with the equilibrium models), F=0.28 yr-1 was chosen as this was identified as the instantaneous fishing mortality rate for this stock during the time period covered in this investigation (NEFSC 2008). A 16.5” minimum harvest size limit along with F=0.28 yr-1 was implemented for a 2005 non-equilibrium population structure, which was generated using age-frequency data on summer flounder collected by the ChesMMAP Trawl Survey from 2002 to 2005, and this projection was allowed to run to equilibrium. The projection provided a measure of relative harvest and egg production (YPR and EPR) by year as the population moved toward equilibrium under a 16.5” minimum size. Because the minimum size was increased to 18.5” in 2007, the 2007 population structure from the 16.5” projection was taken as the initial population for an 18.5” minimum size, F=0.28

343

yr-1 scenario and projected forward to equilibrium. This allowed for a comparison of YPR and EPR by year for the 18.5” minimum size relative to the 16.5” minimum.

Finally, the 2008 population structure from the 18.5” projection was taken as the starting point for a 19” minimum size, F=0.28 yr-1 projection, since the minimum legal size was increased to 19” at that time. This projection was also allowed to run to equilibrium, facilitating comparisons of relative egg production and harvest by year with the two smaller minimum legal size limits.

Assessment of Alternate Management Strategies

As noted above, concerns have been raised regarding the strategy of increasing minimum legal harvest size for the summer flounder recreational fishery in Virginia in response to tightening quotas and stock rebuilding needs both because targeting larger flounder for harvest places almost all of the fishing pressure on the most fecund breeding females, and because these larger fish are relatively unavailable to shore-based anglers.

As an alternative to the minimum legal size management strategy, we investigated summer flounder yield and egg production under a slot and trophy fish management scenario.

Specifically, we compared equilibrium YPR and EPR over the range of F defined above for a 19” minimum size limit (the 2008 regulation) with that for a 15”-18” slot limit, 22”+ trophy fish combination. The slot was chosen as it gives female summer flounder the opportunity to spawn at least once before entering the fishery and includes a portion of the male population, which is effectively absent from the fishery under the current minimum size regulations. The 22+ trophy fish was added because it was felt that

344

most anglers would be reluctant to forgo the opportunity to harvest a very large summer flounder, if captured. Transitional YPR and EPR models were also constructed for each of these management scenarios, using an initial non-equilibrium population structure for 2008 generated from summer flounder age-frequency data collected by the ChesMMAP Trawl Survey from 2005-2007. This approach enabled the comparison of relative egg production and harvest by year as the summer flounder population moved toward equilibrium under each of these management options.

Finally, because the weight of fish harvested is often less important to recreational anglers than is the opportunity to harvest a number of fish, YPR was calculated in terms of numbers (rather than weight) for each of these management options. This was accomplished by eliminating the Wa,s term from Equation (4), and facilitated the comparison of harvest with respect to number at equivalent levels of egg production (stock size and rebuilding potential).

Results and Discussion Assessment of Current Management Strategies

Equilibrium EPR/YPR curves over a range of F are given for each of the minimum legal harvest sizes implemented for the summer flounder recreational fishery in Virginia since 2005 (Figure 6). These curves indicate that at equilibrium, for any given level of harvest (YPR), a larger minimum legal harvest size will result in a greater egg production (EPR) and in theory, stock size. Therefore, increasing minimum legal size to achieve a particular level of harvest for this recreational summer flounder fishery appears to have the potential to result in larger stock size. From a long-term perspective then,

345

Virginiaâ&#x20AC;&#x2122;s strategy of increasing minimum legal harvest size in response to stock rebuilding needs has been compatible with those needs. While it was noted above that summer flounder exhibit sexually dimorphic growth patterns, females typically grow faster and larger than males, and that increasing minimum legal harvest size tends to place most (if not all) of the recreational fishing pressure directly on the most fecund breeding females, it appears that the loss of egg production through the harvest of large females is more than compensated by the reduction of fishing pressure on the smaller, but more numerous, mature females. It is likely that this compensation is possible due to the early maturation and high fecundity of the summer flounder (Figure 7).

A key assumption for the notion that increased egg production will result in a long-term increase in stock size is that egg viability must be equivalent across all sizes of spawning summer flounder. Deviations from this assumption (e.g., if eggs spawned by larger females are of higher quality and therefore more viable than those spawned by younger, smaller fish), have the potential to invalidate our conclusions regarding the relationship between minimum legal harvest size and stock size (from egg production) at a given level of harvest. Also, it was assumed that only flounder of legal size experienced fishing mortality (release mortality for sub-legal fish was minimal), which has been the subject of some debate. Data on the relationship between minimum legal harvest size and release mortality would be necessary to assess the validity of this assumption and quantify the effects of release mortality on YPR and EPR. Unfortunately, this information is presently unavailable.

These equilibrium YPR/EPR curves also indicate that, for the three minimum legal harvest sizes implemented for this summer flounder recreational fishery since 2005,

346

it is possible to achieve varying levels of yield (YPR) while maintaining a particular potential stock size (EPR). Specifically, for any given level of summer flounder EPR, a greater harvest can be gained by using a larger minimum legal size, which again is likely related to the early maturation and high fecundity of this species. The current regulatory process for the summer flounder recreational fishery along the U.S. Atlantic Coast requires that each state either adopt coastwide or develop individual equivalent management measures designed to ensure that state-specific harvest quotas are not exceeded. These YPR/EPR analyses show however, that if provided with a target F and minimum legal harvest size based on some desired level of egg production, states could use such analyses to generate alternate management options that would be equivalent with respect to egg production (and therefore stock size and rebuilding potential), but may provide the state with a greater yield than would otherwise be allowed under the current management structure. This type of strategy was employed by Rhode Island in the 1980s to develop management options for the striped bass fishery (Prager et al. 1987).

Finally, the equilibrium YPR/EPR curves show that, among the minimum legal harvest sizes implemented from 2005 to 2008, egg production increases with minimum size through all levels of effort. In particular, assuming effort is proportional to F, egg production increases with increasing minimum legal size not only at lower levels of effort, but this trend holds at high levels of effort as well, indicating that the largest minimum legal size should afford the most protection to stock size and egg production should effort increase dramatically for some reason. Again, it appears that Virginiaâ&#x20AC;&#x2122;s strategy of increasing minimum legal harvest size in the face of rebuilding needs has been consistent with these needs.

347

Transitional YPR and EPR models were constructed for the 16.5”, 18.5”, and 19” minimum legal harvest sizes beginning with the non-equilibrium population structures from 2005, 2007, and 2008, respectively (corresponding to the years in which each of these minimum sizes were implemented) and with F=0.28 yr-1 (Figure 8). Each of these management scenarios were projected to 2021 to facilitate comparisons among the measures, as this was the earliest year in which all three projections would reach equilibrium. The transitional YPR/EPR models indicate that the shift to an 18.5” minimum size in 2007 from the 16.5” minimum resulted in a reduction in yield in 2007 relative to the harvest had the smaller minimum size been retained for that year. The egg production under each of these regulations was approximately equal in 2007. For each of the subsequent years to 2021, the yield from the 18.5” minimum size at F=0.28 yr-1 was less than that under the 16.5” minimum, but the egg production, and therefore stock size and rebuilding potential, was greater. Similarly, when shifting from the 18.5” minimum legal size to the 19” minimum in 2008, yield was smaller each year with the larger minimum size relative to the 2007 regulation, egg production was equivalent to the 18.5” measure for the first year of the 19” regulation, and egg production under the larger minimum harvest size was greater for each of the following years.

One of the main concerns with using the equilibrium YPR and EPR models is that they only provide information regarding yield and egg production at equilibrium (longterm), and do not supply any indication as to whether a particular change in management regulations could produce a short-term population collapse. Based on the results presented for the transitional YPR/EPR, it does not appear that Virginia’s strategy of increasing legal minimum harvest size for the summer flounder recreational fishery posed

348

any such risk to the stock. Also, it should be noted that, while the projections for each of these management scenarios used F=0.28 yr-1, it would be possible to construct a similar analysis where the desired F varied by management strategy. Such an analysis could prove useful when trying to determine the short-term impacts of a management option that has been shown to generate equivalent egg production (potential stock size) but larger yield and F through equilibrium YPR/EPR modeling efforts.

Assessment of Alternate Management Strategies

A 15”-18” slot, 22”+ trophy management option for the summer flounder recreational fishery in Virginia was compared to the 2008, 19” minimum legal harvest size using equilibrium YPR and EPR models (Figure 9). For all levels of yield, the 19” minimum size limit was associated with a greater egg production, and therefore potential stock size. These results indicate that the current strategy of using a relatively large minimum harvest size is more compatible with rebuilding goals at a particular level of harvest than the slot/trophy combination modeled in this investigation. All combinations of the 15”-18” slot limit, as well as two alternates (i.e., 15”-17” and 16”-18”), and trophy sizes ranging from 21”+ to 24”+ yielded similar results. Also, for a given level of egg production (EPR), the 19” minimum legal size resulted in a greater yield than any of the slot/trophy options tested. Finally, egg production was greater under the 2008, 19” minimum size limit for all levels of F, indicating that this large minimum size is a safer option from a stock rebuilding standpoint even if effort was to increase dramatically.

Overall, it appears that the Virginia strategy of implementing relatively large minimum

349

harvest sizes for its summer flounder recreational fishery is more compatible with stock rebuilding needs than are the slot/trophy options tested here.

Transitional YPR/EPR projections were developed for the 15”-18” slot, 22”+ trophy management option as well as for the 19” minimum legal size to compare the short-term effects of each of these measures on harvest and egg production. Both projections used 2008 as the initial year for implementation of these options and ran to 2021, the year in which equilibrium would be reached for each of these management scenarios in the models. Yield was greater under the slot/trophy combination from 2008 to 2011, while harvest was larger with the 19” minimum from 2012 to 2021 (Figure 10).

Egg production was greater under the 19” minimum legal size relative to the slot/trophy option for all years. Overall, it appears that the large minimum size was more compatible with rebuilding needs relative to the slot/trophy in the short-term as well, but that neither option would result in a short-term stock collapse. While both management scenarios were modeled using transitional YPR and EPR under the same F, it would be possible to conduct a similar analysis with F differing between options (i.e., to investigate the shortterm effects of various management options identified by equilibrium models as having equivalent egg production but varying YPR and F) if so desired.

As noted earlier, measuring yield in terms of weight when evaluating management options for a recreational fishery may not be entirely appropriate, as often recreational fishermen are more interested in the number, rather than the biomass, of fish that they are permitted to harvest. This consideration prompted an evaluation of the harvest trade-offs necessary to maintain equivalent egg production if a shift from a 19” minimum legal harvest to a 15”-18” slot, 22”+ trophy combination was desired.

350

Assuming that the current F with the 19” minimum harvest size is 0.28 (NEFSC 2008), YPR in terms of weight under this regulation was determined to be 0.190 kg recruit-1, based on the models used in this investigation (Figure 11). Equivalent egg production (and therefore stock size and rebuilding potential) was maintained under the aforementioned slot/trophy combination when yield was 0.171 kg recruit-1, meaning that a 10% reduction in harvest with respect to weight would be necessary relative to the 19” minimum. When yield was calculated in terms of number (by eliminating the Wa,s term in Equation 4), however, the YPR under the 19” minimum size at F=0.28 yr-1 was 0.113 fish recruit-1. At an equivalent level of egg production, yield under the 15”-18” slot, 22”+ trophy combination was 0.155 fish recruit-1, representing a 37% increase in the number of summer flounder that could be harvested. This relatively large increase in permissible harvest with respect to number without loss of egg production is likely possible because summer flounder fecundity, while large at the population level at smaller fish sizes (Figure 7), is much greater at the individual level at larger sizes (i.e., it takes the removal of several, smaller mature females to equal the egg loss incurred by the removal of a single, larger one). Furthermore, the slot/trophy combination includes males in the exploitable segment of the population, which are typically not found at larger sizes and do not contribute to the loss of egg production upon harvest.

Finally, it is important to note that while implementing the aforementioned slot/trophy scenario should allow for an increase in the total number of summer flounder harvested by the recreational fishery, individual fishermen may or may not realize an increase in the number of flounder that they are permitted to land. If, by implementing the slot/trophy combination, effort were to increase dramatically (e.g., due to the

351

inclusion of more shore-based anglers in the fishery), the number of fish that any given angler may harvest per day or per season may not increase, and perhaps could decline, relative to the current management strategy. Evaluating potential changes in effort in the summer flounder recreational fishery in Virginia due to changes in management regulations was beyond the scope of this investigation, but the quantification of this relationship would be necessary before setting possession limits for a slot/trophy combination, if such a management option was considered desirable.

References

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Trenton, NJ 15p.

Burnham, K.P., and D.R. Andersen. 2002. Model selection and multimodel inference: a practical information-theoretic approach. Springer-Verlag, New York, NY. Ginsberg, I. 1952. Flounders of the genus Paralichthys and related genera in American waters. Fishery Bulletin 52:267-351.

Gutherz, E.J. 1967. Field guide to the flatfishes of the family Bothidae in the western North Atlantic. U.S. Fish and Wildlife Service, Bureau of Commercial Fisheries, Circular 263.

Hoenig, J.M. 1983. Empirical use of longevity data to estimate mortality rates. Fishery Bulletin 90:276-284.

Leim, A.H., and W.B. Scott. 1966. Fishes of the Atlantic Coast of Canada. Bulletin of the Fisheries Research Board of Canada 155:1-485.

Morse, W.W. 1981. Reproduction of the summer flounder, Paralichthys dentatus.

Journal of Fish Biology 19:189-203.

Northeast Fisheries Science Center (NEFSC). 2008. 47th Northeast Regional Stock Assessment Workshop (47th SAW) Assessment Summary Report. US Department of Commerce, Northeast Fisheries Science Center Reference Document. 08-11; 22 p.

Olney, J.E., and J.M. Hoenig. 1999. Cobia (Rachycentron canadum) in Chesapeake Bay: Reproduction, age, growth, and management options for the recreational fishery. In Proceedings of Special Symposium: Research on Recreational Fishes and Fisheries (J.E. Olney and J. Travelstead, eds.), p. 59-63. Virginia Institute of Marine Science, Gloucester Point, VA.

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Piner, K.R., and C.M. Jones. 2004. Age, growth and the potential for growth overfishing of spot (Leiostomus xanthurus) from the Chesapeake Bay, eastern USA. Marine and Freshwater Research 55: 553-560.

Pitcher, T.J., and P.D.M. Macdonald. 1973. Two models for seasonal growth in fishes.

The Journal of Applied Ecology 10:599-606.

Prager, M.H., Oâ&#x20AC;&#x2122;Brien, J.F., and S.B. Saila. 1987. Using lifetime fecundity to compare management strategies: a case history for striped bass. North American Journal of Fisheries Management 7: 403-409.

Quinn, T.J., and R.B. Deriso. 1999. Quantitative Fish Dynamics. Oxford University Press, Oxford, UK. Richards, F.J. 1959. A flexible growth model for empirical use. Journal of Experimental Botany 10:290-300.

Sipe, A.M., and M.E. Chittenden Jr. 2001. A comparison of calcified structures for ageing summer flounder, Paralichthys dentatus. Fishery Bulletin 99:628-640.

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Yamaoka, K., T. Nakagawa, and T. Uno. 1978. Application of Akaikeâ&#x20AC;&#x2122;s Information Criterion (AIC) in the evaluation of linear pharmacokinetic equations. Journal of Pharmacokinetics and Biopharmaceutics 6:165-175.

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Table 1a. A generalized population structure based on an assumption of equilibrium and used in equilibrium yield-per-recruit and egg-per-recruit modeling. The N column gives number at age, and the R term represents hypothetical recruitment.

Age

N

0

R

1

Re-Z

2

Re-2Z

12 Re-12Z Table 1b. A generalized population structure based on an assumption of non-equilibrium and used in transitional yield-per-recruit and egg-per-recruit modeling. The Ia term represents an index of abundance at age a.

Age Yr 1

Yr 2

Yr 3

Yr 12

0

I0

I0

I0

I0

1

I1

I0e-Z

I0e-Z

I0e-Z

2

I2

I1e-Z

I0e-2Z

I0e-2Z

12

I12

I11e-Z I10e-2Z

I0e-12Z

355

Figure 1. Coastwide quota (millions of pounds) for the U.S. Atlantic Coast summer flounder recreational fishery, along with minimum legal harvest size of summer flounder for the recreational fishery in Virginia, given by year (2003 – 2008).

16.5” min. size

6

Recreational alloction (10 lbs)

13 12 11

17” min. size

10 9 8

16.5” min. size

17.5” min. size

7

18.5” min. size

6 5 2002

2003

2004

2005

356

2006

19” min. size 2007

2008

2009

Figure 2a. Length-frequency, by sex, of summer flounder collected by the ChesMMAP Trawl Survey from 2002 to 2007. Males are given in blue while females are given in red.

800

Females Males

700

Total catch

600 500 400 300 200 100 0 5

7

9

11

13

15

17

19

21

23

25

27

Total length (in.)

Figure 2b. Length-frequency, by sex, of summer flounder collected by the NEAMAP Trawl Survey (nearshore coastal ocean, Marthaâ&#x20AC;&#x2122;s Vineyard, MA to Cape Hatteras, NC) in 2007. Males are given in blue while females are given in red.

120

Females Males

100

Total catch

80 60 40 20 0 4

6

8

10

12

14

16

18

20

Total length (in.)

357

22

24

26

28

Figure 3. Length at age, by sex, of summer flounder collected by the ChesMMAP Trawl Survey from 2002 to 2007. Males are represented in blue while females are given in red, and seasonal growth models are given for each in corresponding colors.

Female: La = 631.4*(1-e (-(0.07*sin(2 Ď&#x20AC;*(a-0.62))+0.29(a+1.01)))) 800

Male: La = 417.3*(1-e (-(-0.15*sin(2Ď&#x20AC;*(a-1.12))+0.61(a+0.56))))

Total length (mm)

700 600 500 400 300 200 100 0

2

4

6

8

Age

358

10

12

14

Figure 4. Weight at length, by sex, for summer flounder collected by the ChesMMAP Trawl Survey from 2002 to 2007. Males are given in blue while females are represented in red, and weight at length models are provided for each in corresponding colors.

-9 3.3138 Female: Wa = 1.517x10 * La

6

-9 3.1927 Male: Wa = 3.209x10 * La

5

Weight (kg)

4 3 2 1 0 100

200

300

400

500

Total length (mm)

359

600

700

800

Figure 5. Probability of encountering a mature female summer flounder by age (equivalent to percentage of mature female summer flounder by age). Individual observations of female summer flounder maturity at age are given by black dots (0 = immature, 1 = mature); data are from summer flounder collected by the ChesMMAP Trawl Survey from 2002 to 2007. The model of summer flounder maturity at age is given by the red line and is provided by the corresponding equation.

Probability mature

1.0

0.8

Logit(p) = 4.16 â&#x20AC;&#x201C; 3.23*(age)

0.6

0.4

0.2

0.0 0

2

4

6

Age

360

8

10

12

14

Figure 6. Equilibrium egg-per-recruit (EPR) versus yield-per-recruit (YPR by weight – kg) for summer flounder under the current minimum harvest size management strategy implemented by Virginia for its recreational fishery. The purple line represents EPR/YPR over a range of instantaneous rates of fishing mortality (F) under a 16.5” minimum size limit (regulation in 2005 & 2006), the green line an 18.5” minimum size limit (2007 regulation), and the black line a 19” size limit (2008 regulation). Points represent particular F on the summer flounder available for harvest. Beginning at the upper left portion of each curve, fishing mortalities are F = 0.0, 0.1, 0.2, 0.28, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5 yr-1. Note that EPR increases with increasing minimum size over all levels of F.

2500000

F=0.1

More yield at EPR with larger min. size

Eggs-per-recruit

2000000

1500000

More eggs at YPR with larger min. size

19” (2008)

1000000

F=0.5

18.5” (2007)

16.5”

500000

(2005 & 2006)

0 0.00

0.05

0.10

0.15

0.20

Yield-per-recruit (kg)

361

0.25

0.30

Figure 7. Population-level relative egg production by length (total length) for summer flounder in the absence of fishing. These values were generated by combining average fecundity at age with the relative number of female summer flounder at each age, assuming 1000 recruits and an equilibrium population structure where M = 0.22 yr-1 and F = 0 yr-1. Average fecundity at age was produced by combining length at age and fecundity at length.

Total egg production (106)

600

500

400

300

200

100

0 10

12

14

16

18

20

Total length (in.)

362

22

24

26

Figure 8. Transitional (non-equilibrium) egg-per-recruit (EPR) versus yield-per-recruit (YPR by weight – kg) for summer flounder under the current minimum harvest size management strategy implemented by Virginia for its recreational fishery. The purple line gives EPR/YPR by year to equilibrium under a 16.5” minimum size limit (regulation in 2005 & 2006), the green line for an 18.5” minimum size (2007 regulation), and the black line for a 19” size limit (2008 regulation). Initial population structure for the 16.5” projection was taken from summer flounder age-frequency data collected by the ChesMMAP Trawl Survey between 2002-2005, while the initial structure for the 18.5” projection was taken as the 2007 population from the 16.5” projection. The 2008 population structure from the 18.5” projection was used as the starting point for a 19” minimum size.

1600000 2021

19”

Eggs-per-recruit

1500000

2021

1400000

18.5” 2009

1300000 2009 2021

2008

1200000

2008

1100000

2007

2009 2008 2007 2006

16.5”

2005

1000000 0.08

0.10

0.12

0.14

0.16

Yield-per-recruit (kg)

363

0.18

0.20

0.22

Figure 9. Equilibrium egg-per-recruit (EPR) versus yield-per-recruit (YPR by weight – kg) for summer flounder under the 2008 minimum harvest size regulation (19”) implemented by Virginia for its recreational fishery, and a slot/trophy management option. The orange line represents EPR/YPR over a range of instantaneous rates of fishing mortality (F) under a 15”-18” slot, 22”+ trophy combination, and the black line the 19” minimum size limit. Points represent particular F on the summer flounder available for harvest. Beginning at the upper left portion of each curve, fishing mortalities are F = 0.0, 0.1, 0.2, 0.28, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5 yr-1. Note that EPR is greater with the 19” minimum size over all levels of F.

2500000

F=0.1

More yield at EPR with 19” min. size

Eggs-per-recruit

2000000

1500000

More eggs at YPR with 19” min. size

1000000

19”

F=0.5 500000

15-18”, 22”+ 0 0.00

0.05

0.10

0.15

0.20

Yield-per-recruit (kg)

364

0.25

0.30

Figure 10. Transitional (non-equilibrium) egg-per-recruit (EPR) versus yield-per-recruit (YPR by weight – kg) for summer flounder under the 2008 minimum harvest size regulation (19”) implemented by Virginia for its recreational fishery, and a slot/trophy management option. The orange line gives EPR/YPR by year to equilibrium under a 15”-18”, 22”+ slot/trophy combination, and the black line for a 19” size limit. Initial population structure for each of these projections was taken from summer flounder agefrequency data collected by the ChesMMAP Trawl Survey from 2005-2007.

1800000

19”

2021

1700000 2021

Eggs-per-recruit

1600000

15-18”, 22”+

2011

1500000 1400000

2011

2010 2010

1300000 2009 2009

1200000 1100000 1000000 0.10

2008

0.12

0.14

0.16

0.18

Yield-per-recruit (kg)

365

0.20

0.22

Figure 11. Equilibrium egg-per-recruit (EPR) versus yield-per-recruit (YPR by weight – kg) for summer flounder under the 2008 minimum harvest size regulation (19”) implemented by Virginia for its recreational fishery, and a slot/trophy management option. The orange line represents EPR/YPR under a 15”-18” slot, 22”+ trophy combination, and the black line the 19” minimum size limit. The horizontal black dotted line represents harvest trade-offs, both in terms of biomass (YPR) and number (NPR – number-per-recruit) of summer flounder harvested, between these management options under the assumption of a current F = 0.28 yr-1 for the 19” minimum size limit.

2500000

NPR = 0.113 fish/rec.

Eggs-per-recruit

2000000

YPR = 0.190 kg/rec.

1500000

YPR = 0.171 kg/rec.

10% REDUCTION – biomass harvest

1000000

19”

NPR = 0.155 fish/rec.

500000

37% INCREASE – numbers harvest

15-18”, 22”+ 0 0.00

0.05

0.10

0.15

0.20

Yield-per-recruit (kg)

366

0.25

0.30