Electric Fishing Fry Index Survey - Teign

Electric Fishing Fry Index Survey

River Teign

January 2023

Hannah Winchester

Image copyright: Mike Rego 2022

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Westcountry Rivers Trust is an environmental charity established in 1995 to restore, protect and improve the rivers, streams, and water environments in the region for the benefit of wildlife and people.

This report has been written and prepared by: Hannah Winchester

Published by: Westcountry Rivers Trust Rain Charm House, Kyl Cober Parc, Stoke Climsland, Callington, Cornwall, PL17 8PH.

Tel: 01579 372140

Email: info@wrt.org.uk

Web: www.wrt.org.uk

Charity no. 1135007

Company no. 06545646

Document history:

© Westcountry Rivers Trust: 2023. All rights reserved. This document may be reproduced with prior permission of the Westcountry Rivers Trust

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Executive Summary

Westcountry Rivers Trust (WRT) undertook electric fishing (EF) surveys throughout the river Teign catchment during the summer of 2022. The surveys are a continuation of monitoring undertaken during the Catchment Restoration Fund programmes which took place 2012-2015 and are now possible through donations from the Teign Restoration Project, monitoring under the South West Water (SWW) South Teign Gravel Augmentation Project (reported separately, however, results included here for catchment context) and the Woodland Trust. Both salmon and trout are present throughout the Teign, and numbers are highest along the main river stem with some natural annual fluctuations. It should be noted that summer 2022 was the driest since 1995 as well as the second hottest year on record. Despite this, high numbers of juvenile Atlantic salmon (Salmo salar) were recorded. Conservation strategies, such as the Defend/Repair/Attack approach, can be applied on a sub catchment level with recommended fisheries management actions suggested to either improve or maintain salmonid habitat and numbers.

Westcountry

Rivers Trust Electric Fishing Survey Report - River Teign, 2022

1. Introduction

The Westcountry Rivers Trust (WRT) undertook semi-quantitative fry index electric fishing survey of the River Teign catchment in August and September 2022. This was the tenth year of fish monitoring undertaken by WRT and forms part of establishing a long-term dataset of semi-quantitative fry numbers.

This year, the survey programme was largely based around the 2021 programme, however, there were some sites not fished by WRT as these were either monitored by the Environment Agency or not fishable due to river conditions. It is hoped that the programme will continue to be surveyed every year to build a strong baseline dataset for the catchment. An additional four surveys were conducted as part of the South West Water gravel augmentation project associated with Fernworthy Reservoir, and a donation from the Woodland Trust allowed WRT to expand the survey program by an additional five sites.

Figure 1 Survey site location, River Teign, 2022

2. Methodology

2.1 Electric Fishing Protocols

Electric fishing uses a controlled electric current to induce fish to swim toward an anode and into a hand net, and thereby be counted and assessed. When carried out correctly by experienced and qualified surveyors it is not harmful to fish and the fish are released back to the same location they were caught. In upland streams and shallower sections of rivers, an electric fishing backpack is preferred and therefore this type of kit was used for all the Teign surveys.

There are several approaches to electric fishing assessments in rivers; quantitative, area semi-quantitative and time semi-quantitative methodologies. All three methods have their advantages and disadvantages.

Quantitative electric fishing is a thorough methodology that has the highest degree of accuracy of all the methods. The main disadvantages of this approach are it is less mobile than backpack equipment and it takes longer to undertake surveys. It is therefore more costly than other approaches. With this method, an area of river is netted off and the fish are removed from this defined stretch in multiple passes until sufficient fish are removed to form a very accurate assessment of species and numbers. It is not required to remove all the fish from the area but rather ensure a consistent fishing method that gives a linear decrease in the number of fish caught per pass. The overall catch decline gives an accurate estimate of the total number of fish in the location. This is known as the ‘depletion’ methodology.

An area-based semi-quantitative electric fishing methodology follows the same process as quantitative electric fishing but only a single pass is carried out. A lack of multiple passes renders the method only semi quantitative and therefore less accurate, but it has the advantage of being much quicker than the depletion method, and it is suitable for use on all waterbody types. It is able to detect multiple species and is reasonably accurate but is less time efficient and therefore costlier than a time-based methodology (described below).

A time-based, semi-quantitative electric fishing methodology differs from both the approaches described above. Instead of limiting the area fished (by use of nets) it limits the amount of time used to fish to assess fish numbers. As no nets are deployed, fish in deeper sections of large rivers can frequently avoid capture using this method. It is therefore only suitable to assess salmonid fry, who are restricted to a shallower section of upland streams and rivers. This method is extremely rapid and therefore costeffective, allowing for deployment across whole river catchments although its major drawback is its lower accuracy than netted approaches.

In weighing up the pros and cons of the various approaches it is worth considering what would be required for a truly reliable method. In scientific publications it is usually considered that if an approach is accurate 95% of the time then this is an acceptable

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

standard. Such an approach would be said to have sufficient statistical power to answer the question asked, for example, ‘has this habitat improvement resulted in more fish in the area studied?’. For an electric fishing methodology to have sufficient statistical power it requires a large number of sites to be fished in a fully-quantitative depletion methodology over a number of years. As such an effort is rarely practicable and will cost more than the habitat improvements it attempts to measure, this approach is rarely applied in the UK. River managers in the UK have limited budgets and therefore it is the case that an electric fishing programme of insufficient statistical power to achieve 95% confidence is usually accepted as a compromise between accuracy and cost.

Bearing in mind the limits of statistical power that these approaches usually have (as practically applied), it is important to consider the aim of a given electric fishing programme. In the case of WRT’s catchment scale electric fishing programme, the aim is to build up historical data on each catchment to provide information as to how to best take action to improve the fish stocks for salmon and trout. To achieve this, the largest number of sites possible for maximum catchment coverage must be fished over several consecutive years to i) guide current/future conservation strategies and ii) identify whether or not the actions taken on the catchment have had a positive effect on fish numbers. Most importantly the electric fishing programme is specified to be carried out at a catchment scale where salmon and trout spawning areas occur. As most rivers have many tributaries or main stems of considerable length, a relatively large number of sites are required for full coverage. This typically equates to between 20 to 100 sites on rivers in southwest England, depending on the river catchment geography. All things considered; a timed semi-quantitative approach was considered most appropriate for the WRT electric fishing programme. This method will indicate the main issues and areas that need addressing on a river catchment including:

• Upstream barriers to fish-passage

• Degraded habitat quality

• The upper limit of salmon spawning

• Successfully/unsuccessfully enhanced habitat

• Catchment-scale fry migration due to river levels

• Point source and diffuse pollution

2.2 Life Cycle and Bottlenecks

Classifications for each sub catchment were analysed and given an average score based on the number of classifications received which were then used in the final classification and Defend Repair Attack (DRA) strategy. A higher number of sites surveyed allowed for a more accurate score, so some caution is advised when low or singular sites were surveyed for some sub catchments. The aim of the semi-quantitative electric fishing program is to identify issues that prevent salmonids from effectively completing their life-cycle, and then proposing solutions that are proportionate to the issue at hand. It is useful to adopt certain conceptual frameworks to each of these aims,

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

and in this report, we will use two of these frameworks; the ‘habitat bottlenecks’ that describe the causes of issues in salmonid ecology (Figure 2), and the ‘Defend/Repair/Restore’ conservation strategy framework which describes the appropriate habitat action depending on the ecological situation found at the site.

2.3 Catchment-Based Fisheries Conservation Strategy (Defend/Repair/Attack)

Classifications for each sub catchment were analysed and given an average score based on the number of classifications received which were then used in the final classification and Defend Repair Attack (DRA) strategy. A higher number of sites surveyed allowed for a more accurate score, so some caution is advised when low or singular sites were surveyed for sub catchments. In using the fry index classification, catchment population abundance monitoring and determining the river reach density classification, a series of priority areas can be outlined, and management recommendations made tailored to the particular species. Recommendation actions broadly follow the Defend/Repair/Attack concept, developed by Ronald Campbell of the Tweed Foundation. For every river reach that is classified, a management action can be recommended

Whilst this provides a useful structuring framework, the reality of given situations can bring many complexities and lies on a continuum between these extremes. The goal is to improve the river reaches of the Teign to a healthy, natural riverine ecosystem. Where the populations are in a very poor state, radical actions may be required to see a change. Conversely, where the stocks are already good, habitat re-engineering and stocking operations would be inappropriate. Actions to achieve these improvements can be divided between ‘fish stock actions’ such as fish translocations or bag limits for anglers and ‘fish habitat actions’ such as removing barriers to migration or coppicing. In many situations, both types of action will be required. This concept helps divide catchment scale management for fisheries into priorities and therefore can help to maximise multiple benefits through targeted work.

Figure 2 Diagrams defining salmonid habitat bottlenecks (Summers et al, 1996)

2.4Site Selection

Survey sites on the Teign were selected to provide representative samples from distinct river reaches, characterised by habitat type, proximity to barriers and proximity to targeted restoration works such as under the gravel augmentation project. Sites are proposed by WRT and Teign Angling and Conservation Association (TACA), following on from the Dart and Teign River Improvement Project (DTRIP) and will help to contribute to a longer-term EF survey dataset where trends can be established, and positive or negative patterns of juvenile salmonid populations identified based on the findings within a sub catchment.

2.5 Field Sampling and Data Analysis

Permission for all sites was established before electric fishing surveys took place and each site was electric fished by a two or three-person team. The voltage of the unit was set at each site depending on the water conductivity, measured using a handheld conductivity meter. The operatives fished continuously for a standard five minutes over suitable fry habitat without the use of stop nets. The fishing area was variable, and the length of fishing time was fixed. Fish were collected in a net and placed into an aerated holding bucket before processing.

All salmonids were identified to species and fork length was measured and recorded. Counts were recorded for all other species captured. Habitat features such as land use, substrate type and shading were recorded at each site. Any fry that were missed or escaped during electric fishing were assigned to either trout or salmon groups depending on the relative percentage of each species already recorded at the site.

The results of the electric fishing survey are classified according to the methodology of Crozier and Kennedy (1994), displayed in Table 1, with each site being given an equivalent density classification compared to quantitative monitoring. This semi-quantitative methodology was designed by Crozier and Kennedy for both salmon and trout. However, the results for trout need adjustments to consider the difference in the regression line for trout and salmon as described by Crozier and Kennedy.

Based on the lengths of fish captured during the survey, using a length frequency histogram, salmon fry were considered to be any individual that measured up to 90mm

Table 1 Semi-quantitative abundance categories for salmon fry (Crozier & Kennedy, 1994)

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

(Figure 3) and trout fry were considered to be any individual measuring up to 100mm (Figure 4).

Atlantic salmon frequency distribution, 2022

Brown trout frequency distribution, 2022

3. Results

WRT surveyed 41 semi-quantitative sites on the River Teign in August and September, a repeat of the 2021 program. In addition to four sites on the South Teign (for South West Water), a further five semi-quantitative surveys were funded by donations towards the River Teign electric fishing programme by the Woodland Trust. Survey conditions were challenging, with high air and water temperatures, and a degree of habitat fragmentation was recorded. It should be noted that summer 2022 was the driest since 1995 as well as the second hottest year on record. As with previous years, surveyors kept a close eye on river water temperatures to ensure surveying did not proceed if water temperatures exceeded 18°C, in accordance with Environment Agency guidance.

Figure 3 Salmon fry length frequency distribution, River Teign 2022

Figure 4 Trout fry length frequency distribution, River Teign 2022

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

As in previous years, the 2022 catchment survey demonstrates that the Teign catchment supports excellent salmonid spawning and the importance of large, main river stem spawning sites for salmon reproduction. There were 13 excellent classification sites in 2022 for salmon fry, along with six good sites. Salmon fry were absent from 17 of the 49 sites (35%), with some of these sites being historically absent of salmon, mainly due to obstructions and poor habitat Trout numbers remain quite robust, there were 12 excellent classification sites for trout fry as well as ten good classification sites in 2022, with trout fry absent from nine of the 49 sites (18%). A total of 1184 salmon (fry and parr) and 767 trout (fry and parr) were caught across all 49 sites in the Teign catchment. The best performing sites for juvenile salmonids were; Sowton Mill on the main River Teign (203 salmon fry) and the Liverton Brook for trout fry (53) Although most of the salmon spawning occurs on the main river, some tributaries, such as the Blackaton Brook also produced strong scores (Table 2). Considering the prevailing conditions over summer, this slight increase in total catch is considered a positive outcome.

South Teign results are discussed as part of a separate report, as the surveys are associated with monitoring of the gravel augmentation and habitat improvements associated with the South West Water asset, Fernworthy Reservoir. However, notably salmon fry were recorded again at Yardworthy/Wonacott, this represents the farthest penetration of salmon through the River Teign catchment, approximately 45km from the tidal estuary.

Table 2 River Teign salmon and trout fry classifications for 2022 (ordered from upstream to downstream)

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Table 3 Comparative salmon fry results including historic WRT data. *sites funded by SWW, **Woodland Trust sites

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Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Table 4 Comparative trout fry results including historic WRT data. *sites funded by SWW, **Woodland Trust sites

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Usually where salmon fry are absent from a riffle site, trout fry predominated Conversely, where large numbers of juvenile salmon are found, the brown trout are often outcompeted and ‘pushed out’ into other habitats such as smaller tributaries. Therefore, any sites where large numbers of salmon are recorded alongside low trout numbers should not be taken as a lack of trout, it is highly likely that the brown trout are not truly absent, but that the surveys did not locate them. Examples of such sites would be ‘Mill End’ , ‘Rushford Mill’ and ‘D/S Fingle Bridge’ in Table 2.

Figure 5 Total catch for salmon and trout fry, River Teign 2022

Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Figure 6 Salmon fry classifications, River Teign 2022

Figure 7 Trout fry classifications, River Teign 2022

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

The graph below helps to illustrate the long-term trends and variability of salmon and trout fry numbers in the Teign catchment. Individual trends in salmon and trout can be visualised, along with the combined average fry numbers for the river. Salmon data is shown to be more variable year to year, whereas trout data tends to be more stable, with

Figure 8 Stacked bar charts showing percentage split of salmon fry classifications, annually.

Figure 9 Stacked bar charts showing percentage split of trout fry classifications, annually.

Teign Salmon Fry Classification Stack

Teign Trout Fry Classification Stack

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

a general upward trend. This assessment suggests that average salmon and trout fry catch has increased since 2021 with more salmon than trout overall, as expected possibly due to a focus on salmon habitat sites. The average fry numbers were highest in 2013, followed by the lowest in 2014. However, number and location of sites do change year on year so although an average can be produced and aid in visualising salmonid density in the catchment there are several influential variables to consider.

Annual

In general, 2022 shows an improvement on the 2021 data for both salmon juveniles (Figure 8), brown trout juveniles (Figure 9) and the overall juvenile salmonid population (Figure 10) across the Teign catchment and its tributaries. Some exceptional sites were recorded on the main river for Atlantic salmon, with ‘Rushford Mill’ (128 fry), ‘D/S Clifford Bridge’ (116 fry), ‘D/S Clifford Bridge (149 fry) and ‘Sowton Weir’ (203 fry) (refer to Table 2). It has been considered that these high numbers may have been a result of condensed habitat due to low water. However, the author would submit that this is not the case, as the limiting factor in semi-quantitative surveying is time (5 minutes of fishing) and so the same fishing effort is delivered regardless of wetted area.

The results also elegantly illustrate the interspecific competition that occurs when high numbers of juvenile Atlantic salmon are present. For example, in the same exceptional sites above, trout were absent from all cited surveys apart from ‘Rushford Mill, where one brown trout was found (refer to Table 2). Furthermore, where Atlantic salmon juveniles were not present, strong numbers of brown trout were recorded. Examples from smaller tributaries and the main stem of the Teign include the ‘Rookery Brook’ (0 Atlantic salmon

Figure 10 Annual salmonid fry mean catch data, with combined mean data

salmonid fry survey data for the Teign catchment (20122022)

– 42 brown trout), ‘Liverton Brook’ (0 - 53), ‘Beetor Bridge’ on the River Bovey (0 – 43) and at ‘Halls Cleave’ on the main River Teign (0 – 35) (refer to Table 2).

Overall, 2022 in comparison to previous years has shown positive results for the spawning production of both brown trout and Atlantic salmon.

4. Recommendations

The WRT EF surveys are undertaken to gain an understanding on annual recruitment of salmon and trout, but they have slightly different habitat preferences, and one species will often dominate over the other where the other has limited or no presence. There will be natural annual variations in populations, and this is to be expected depending on the success of the adult return numbers, winter river conditions and habitat limitations that may arise. Despite trout fry populations increasing in some areas, it is equally important that defence strategies are put in place to maintain good recruitment and to restore numbers elsewhere in the Teign. In areas where salmon have decreased, the repair strategy and appropriate actions should be implemented where funding allows. Therefore, management strategies need to be considered for each species, hence a conservation strategy for both salmon and trout.

The strategy for restoration and conservation of sites suggested here broadly follows the “Defend, Repair, Attack” (DRA) concept (Table 5) developed by Ronald Campbell of the Tweed Foundation, and has, in the past, been applied locally in the Exe catchment by the River Exe and Tributaries Association project. The fry productivity of the rivers is assessed by a combination of historic semi-quantitative electric fishing results. These results are then applied in context of existing plans (e.g. Salmon Action Plan, habitat walkover surveys and genetic data) to produce assessments and recommendations for each subcatchment of the river. These sub-catchments are classified according to three levels: Defend, Repair, and Attack.

Despite the DRA strategy being a useful tool to identify and prioritise works in catchments, the requirements of waterbodies can rarely be quite so clear cut. The coloured arrow in Table 5 represents the continuum of the three strategies and the goal for each waterbody; to move all the Teign sites from their current position to somewhere in the Defend category, or to ensure they remain in this status if fish stocks are already good.

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

These areas have good fish stocks and habitat and need safeguarding actions to ensure no decline occurs.

These areas have moderate fish stocks, and fish habitat in a moderate condition; these areas need assisted habitat recovery to move them into the Defend category.

These areas have poor fish stocks, and the habitat is significantly degraded. These areas need drastic intervention such as habitat reengineering in order to improve their status.

Table 5 Defend/Repair/Attack strategy

Table 6 Teign sub catchment classification and DRA strategy.

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Recommended works:

Gravel augmentation: Continue to conduct gravel augmentation on the South Teign and monitor gravel deposition through gravel audit surveys to determine requirement for future gravel augmentations.

Fencing: Riparian zones identified as receiving significant livestock access, with apparent habitat degradation, should be fenced to limit trampling and bank side poaching Precautions should be taken to ensure livestock can access drinking water supply. Effective buffer strips dependant on site characteristics is advised.

Coppicing: Targeted selective coppicing of woodland and abandoned riparian coppice adjacent to juvenile habitat riffles should be undertaken This will increase primary productivity and food source for juvenile fish. Shade should be maintained on deeper pools and runs for water temperature and adult fish habitat cover.

Erosion Control: Fencing and effective marginal habitat management will reduce erosion. However, where specific areas of high pressure and vulnerability are identified, erosion

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

protection measures such as woody debris installation, environmentally sensitive revetments, and strategic tree planting would be advantageous.

Fish Passage Assessment: Assessment of potential fish migration barriers using the Coarse Resolution Rapid Assessment technique developed by the Scottish and Northern Irish Forum For Environmental Research (SNIFFER). A standardised survey technique to assess impact of in-channel structures.

In-Channel Habitat Restoration: Installation and construction of habitat enhancing features, including woody debris introduction, flow manipulation with groins and kickers, bank reprofiling for marginal zonation, strategic tree planting, gravel introduction and riffle creation, and historic channel restoration. Advanced management usually applied post success of other recommended actions.

Modify flow regime: Where flows are impacted by storage reservoirs, liaise with service provider to discuss and inform of findings of EF surveys to determine management of flow regime from impoundments at appropriate times of years for fisheries benefit.

Walkover Surveys: Recording of habitat availability relating to ontogenetic stages of fish, including observed local land use and factors negatively impacting habitat quality. Often the starting point for work in an area following from poor fry index survey results. An important component of catchment management. Walkovers essentially build wide scale understanding of a catchment and allow forging of relationships with local landowners.

Interpretation: Sensitive spawning sites can be exposed to disturbance at key times of year. Interpretation boards can be used to inform of salmonid presence and advise on in river site avoidance.

Assess monitoring effort: By adapting survey effort, appropriate information can be gained according to strategic plans for the catchment based on current and historic data. It is recommended that redd observations be encouraged annually to coincide with fry index survey data. Continue with volunteer invertebrate monitoring e.g. Riverfly, and WRT recommended the Citizen Science Investigation (CSI) programmes run by WRT.

These works should be tailored to each sub catchment and prioritised according to the status of the river bodies. Table 7 displays the recommended works required in each waterbody to restore habitat and increase fry populations.

Gravel augmentation on the South Teign continued in 2022 with 96 tonnes of granite gravel introduced into the South Teign at two sites, below the dam wall and at Yardworthy Farm. Fisheries bank releases is currently under investigation on the South Teign and Fernworthy Dam SWW have recently begun a compensation flow release from the Kennick, Tottiford and Trenchford reservoirs. SWW is undertaking adaptive management trials on the Beadon Brook to improve the habitat for salmonids under an AMP7 (20202025) Water Industry National Environment Programme (WINEP) scheme to meet the Heavily Modified Water Body (HMWB) requirements to mitigate the impact of Kennick, Tottiford and Trenchford (KTT) reservoirs on the Beadon Brook. The first gravel

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

augmentation activities were carried out by WRT in 2022, with approximately 30 tonnes of granite gravel transferred to the brook. Monitoring is being carried out to determine success of this and scalability of the gravel augmentation for future years.

Westcountry Rivers Trust Electric Fishing Survey Report - River Teign, 2022

Table 7 Recommended DRA actions for Teign sub catchments

5. Acknowledgements

Thanks to all landowners involved for their kind permission and to the Environment Agency for providing consent for the surveys.

We would also like to thank the Teign Angling and Conservation Association, South West Water and the Woodland Trust for providing funding, donation and support for the 2022 surveys. Particular thanks go to TACA volunteer Neil Yeandle and River Teign Restoration Project Officers Geoff Stephens and Louise Davis for their efforts in making up the electric fishing team and to Roger Furniss for his involvement and efforts in planning these surveys.