Electric Fishing Fry Index Survey - Camel

Semi & Fully Quantitative Electric Fishing Surveys

River Camel

January 2023

Hannah Winchester

Westcountry Rivers Trust Electrofishing Survey Report - River Camel, 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 Electrofishing Survey Report - River Camel, 2022

Executive Summary

Westcountry Rivers Trust (WRT) undertook electric fishing (EF) surveys throughout the River Camel catchment during the summer of 2022. The surveys are a continuation of monitoring undertaken as part of the Water for Growth Project (W4G) and is the sixth year of Fry Index Survey monitoring, the second year of additional quantitative areabased surveys conducted on the catchment and the final year being funded by this project. Both salmon and trout are present throughout the Camel catchment with most of the salmon spawning occurring on the main river, whereas most of the trout spawning occurred in tributaries. It should also be noted that summer 2022 was the driest since 1995 as well as the second hottest year on record. Conservation strategies, such as the Defend/Repair/Attack approach, have been applied on a sub-catchment level dependent on classifications received during the semi-quantitative surveys. Works undertaken through the W4G project have been commented on where it is believed fish passage improvements have increased salmonid recruitment or where fish passage concerns are restricting access to certain areas.

1. Introduction

The Westcountry Rivers Trust (WRT) undertook semi-quantitative fry index and quantitative area-based electric fishing surveys of the River Camel catchment in August 2022. This was the sixth consecutive year of fish monitoring undertaken by WRT as part of the monitoring for the Water for Growth Project (W4G) and forms part of establishing a long-term dataset of semi-quantitative fry numbers and quantitative fry and parr density.

This year the sites were selected from the list of 2021 sites with the addition of one new site (Figure 1), however, there were a few sites not surveyed by WRT as these were monitored by the Environment Agency as part of their six-year cycle Water Framework Directive monitoring. It is hoped that these sites will continue to be surveyed every year to build a strong baseline dataset for the catchment.

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 where possible. In upland streams and shallower sections of rivers, an electric fishing backpack is used and therefore this type of kit was used for all the Camel surveys.

Figure 1 Survey site location, River Camel, 2022

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 considered 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 can 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 cost-effective, 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 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 many 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

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, 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/Attack’ 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)

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 loosely determined.

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 move the river reaches of the Camel up from the unstable point (i.e., poor fish stocks and habitat) to the broad top of 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.

2.4Site Selection

Survey sites on the River Camel were selected to provide representative samples from distinct river reaches, characterised by habitat type, proximity to barriers and proximity to targeted restoration works. Sites are proposed by WRT and will help to contribute to a longer-term EF survey dataset where trends can be established, and positive or negative patterns of salmonid recruitment inferred based on the findings within a sub catchment.

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

2.5 Field Sampling and Data Analysis

Permission for all sites was established before electric fishing surveys took place and each site was surveyed 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. Numbers or density estimates 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 semi-quantitative electric fishing survey results were 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.

The quantitative results were analysed using the statistical quantitative Zippin removal model (Zippin, 1958) to determine an estimated population size. Population estimates for the area fished are used to calculate the density of population per 100m2. The results from the Zippin removal model were then used to classify each site using the National Fisheries Classification Scheme (Table 2).

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

Westcountry Rivers Trust Electrofishing Survey Report - River Camel, 2022

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 85mm (Figure 3) and trout fry were considered to be any individual measuring up to 100mm (Figure 4).

Table 2 National Fisheries Classification Scheme

Figure 3 Salmon fry length frequency distribution, River Camel 2022

Figure 4 Trout fry length frequency distribution, River Camel 2022

Atlantic salmon frequency distribution, 2022

Brown trout frequency distribution, 2022

3. Results and Discussion

WRT surveyed 24 semi-quantitative sites and one quantitative site on the Camel in August 2022. Weather and general survey conditions were dry and very warm which resulted in extremely low river levels and increased water temperatures. It should be noted that the summer of 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.

As in previous years, the 2022 surveys demonstrates that the Camel catchment supports excellent salmonid spawning and the importance of large main river stem spawning sites for salmon production. Whereas trout rely more on important side tributaries. Of the 24 semi-quantitative sites surveyed for salmon fry there were six excellent classifications, three fair classifications, one poor classifications and 14 absent classifications. Of the 24 semi-quantitative sites surveyed for trout fry there were six excellent classifications, nine good classifications, four fair classifications and five poor classifications. Most of the salmon spawning occurred on the main River Camel and one site at the bottom of the Waterloo Stream With the exception of some low salmon numbers found on the River Ruthern, Nanstallon and Coldrinick Stream, most other tributaries were absent of salmon fry. Trout spawning occurred at all survey sites. All excellent sites were located on smaller tributaries, with the exception of Worthyvale, with the lowest numbers being on the main river, usually where salmon fry recruitment was excellent. A total of 360 salmon (349 in 2021) and 548 trout (936 in 2021) were caught across all sites which included the number of salmon and trout parr caught at each semi-quantitative site, but these do not have any formal classification associated.

Table 3 River Camel semi-quantitative salmon and trout fry classifications including parr results, 2022 (ordered from upstream to downstream)

Westcountry Rivers Trust Electrofishing Survey Report - River Camel, 2022

Table 4 Camel salmon fry historic classifications 2017-2022.

Salmon fry classifications

Westcountry Rivers Trust Electrofishing Survey Report - River Camel, 2022

Westcountry Rivers Trust Electrofishing Survey Report - River Camel, 2022

Table 5 Camel trout fry historic classifications, 2017-2022.

Trout fry classifications

Westcountry Rivers Trust Electrofishing Survey Report - River Camel, 2022

Trout fry classifications

Figure 5 Annual percentage split of semi-quantitative salmon fry classifications from 2017-2022

Average Salmonid Fry Catch Numbers 2017-2022

A fully quantitative survey was conducted upstream of Keybridge weir, however, the survey was void due to sudden heavy rain which rapidly increased river levels making it unsafe, as well as increased turbidity making spotting fish extremely difficult. Both salmon and trout fry and parr were caught but no formal classifications were possible.

Figure 6 Annual percentage split of semi-quantitative trout fry classifications from 2017-2022

Figure 7 Mean annual semi-quantitative salmonid fry caught per site from 2017-2022

Camel Brown Trout Classifications Stack

Westcountry Rivers Trust Electrofishing Survey Report - River Camel, 2022

Table 6 River Camel quantitative trout fry and parr classifications including density per 100m2

Site Name River Trout Fry Trout Parr US Keybridge De Lank void void

Table 7 River Camel quantitative salmon fry and parr classifications including density per 100m2

Site Name River Salmon Fry Salmon Parr US Keybridge De Lank void void

Table 8 River Camel quantitative results in comparison to 2021

Table 9 River Camel quantitative results in comparison to 2021

Figure 8 Total catch for salmon and trout derived from semi-quantitative data (including total number of fry per survey site), River Camel 2022

Figure 9 Semi-quantitative salmon fry classification, River Camel 2022

Figure 10 Semi-quantitative trout fry classification, River Camel 2022

Main River Camel

Salmon recruitment occurred mostly on the main River Camel with five excellent sites being present at Trecarne, Wenford Bridge, Tresarett, Waterland and Colquite (31, 57, 61, 36 and 33 fry recorded, respectively). This was an improvement from only two excellent sites recorded in 2021. The furthest upstream sites located in the upper main river were Worthyvale and Trekeek and although no salmon fry were located at either sites, a single salmon parr was recorded at the Worthyvale site in 2021. Works to remove barriers at this sites are planned to take place in the summer of 2023 which could benefit access to salmon upstream.

These findings support that there is quality habitat available through most of the extent of the main river, enabling consistent salmon spawning and free access for migration from bottom to the upper reaches. WRT have worked extensively in the River Camel catchment through the Water for Growth project improving fish passage by either easing barriers or removing where possible. In addition to this, ongoing habitat works are being undertaken in the catchment on key areas to help improve the shade/light regime and improve the general quality of habitat available for salmonids. With salmon now being caught in the upper reaches of the main river, it appears this work may have enabled more fish to reach valuable spawning grounds with the salmon parr at the Worthyvale site. Further monitoring will highlight the success of salmon spawning in these upper reaches. Brown trout fry were found in far lower numbers than salmon fry, with most sites being classified as ‘poor’. It is apparent that when salmon fry dominated sites, trout fry numbers are far lower, possibly being outcompeted for available habitat. This is further supported by the abundance of trout fry at Worthyvale and Trekeek, where no salmon fry were recorded and trout were found in relatively good abundance. It could be possible that trout fry that normally use the main river to spawn are being outcompeted by high numbers of salmon spawning, opting to use the smaller, more available side tributaries.

River Ruthern

Salmon fry recruitment was relatively low on the River Ruthern, with only two fair classifications being achieved at Cotton Woods and Ruthern Airfield, and salmon were absent from Tremor Bridge and US Treliver. The furthest upstream site extent where salmon fry were recorded was Ruthern Airfield, with seven fry recorded in close proximity to Cotton Woods, which recorded nine salmon fry. Although salmon recruitment was still low in 2022, both sites have increased from a poor to fair classification. Both sites were relatively low down on the river and appeared to lack a lot of quality spawning, fry and parr habitat, which could support a lack of salmon and trout fry abundance. Brown trout recruitment can be quite sporadic on the River Ruthern, 2022 results supported this with an increase in abundance at all sites with Ruthern Airfield and Tremore Bridge both increasing from fair to good. Where salmon are absent, trout usually take residence when competition is low, this doesn’t appear to be the case in the lower/mid stretches.

However, US Treliver did achieve a good classification for trout with 23 fry and does lend itself to the notion that there is more quality habitat available in the upper reaches of the Ruthern. Through the Water for Growth project two barriers, located in proximity of the Whitehay and Treliver survey sites, have both received intervention work to improve passability, after one of the structures was considered a medium to high impact obstacle to migrating salmonids. It is hoped over the coming years, these survey sites will see an increase in salmon as more quality habitat has been made available and more easily accessible in all flow conditions.

Waterloo Stream

The Waterloo Stream sites were new for 2021 and all sites were absent for salmon fry when originally surveyed. For the 2022 surveys, a new site was added which was located approximately 30 meters upstream of the confluence which resulted in an excellent classification with 30 salmon fry. The Waterloo Stream contains a varied habitat of good quality, so this appears not to be the limiting factor in salmon absence. Moreso, trout fry were in high numbers with US Mill House and US of Weir achieving excellent classifications of 41 and 48 fry, respectively. During the work of the Water for Growth project, several barriers were highlighted low down on the Waterloo Stream, which appear to be high impact barriers, and could support why salmon fry have not been found further upstream. This is further supported by the excellent site which was located below all barriers on this stream. Works are scheduled to take place in the summer of 2023 to the barriers most downstream on this section which should allow access to quality habitat present above this.

De Lank

Salmon fry recruitment was absent at the two semi-quantitative sites, Pumphouse and Bradford Bridge, on the De Lank. Similar to the Waterloo Stream, the De Lank River has an abundance of varied habitat of high quality and is a particularly large tributary of the main River Camel. Therefore, it is believed that this is not the limiting factor as to why salmon fry were absent from these sites, supported by the good amount of trout fry caught at the Pump House site. Usually, trout are in high numbers at the Bradford Bridge site but there was a large growth of weed at the survey site which made conditions extremely difficult to spot fish. Salmon are absent from this site due to it being location above the De Lank quarry with no salmon records since surveying started at this site. A further quantitative survey was conducted upstream of Keybridge weir, however, unfortunately the survey was void due to sudden heavy rain which rapidly increased river levels making it unsafe, as well as increased turbidity making spotting fish extremely difficult. Both salmon and trout fry and parr were caught but no formal classification was possible. The De Lank quarry, which has been operating for many decades, is situated a little upstream of the Pump House site and is known to have caused a major and complete barrier to migrating salmon. The results of long-term quarrying at this site have had a negative impact not only on fish passage but the quality of habitat downstream as

Westcountry Rivers Trust Electrofishing Survey Report - River Camel, 2022

the natural flow of spawning gravel has been inhibited. This is apparent at the Pump House site which produces no salmon fry due to very little habitat, as it is dominated by large, immobile boulders, fine sands in deeper pools and gullies. As you travel downstream, side tributaries seem to supplement gravel inputs although there is still a lack of the full gravel matrix required by salmonid species, particularly salmon. Both 2021 and 2022 resulted in a single salmon parr being caught at this site, which further supports that salmon are making it to the quarry but unable to reach large amounts of habitat upstream. Discussions are ongoing with the quarry operators and WRT Officers working on the Water for Growth project to identify possible options to improve fish passage in the future. However, this is not a quick fix due to the scale of the problem and length of river affected. Although salmon were present at the US Keybridge site, it is hoped that this will continue to increase as a considerable boulder weir was removed in Autumn 2020, as part of the Water for Growth project, which lies only several hundred meters downstream of this site improving fish passage considerably. In addition to this a gravel augmentation took place at the Keybridge site in 2022, which will supplement some of the missing gravel fractions and it is hoped that in conjunction with the removal of barriers and planned habitat works that this will all aid in recruitment of salmonids.

Allen

Salmon fry were absent at both the semi-quantitative sites on the River Allen, Trewen and Delabole. Both sites lie in the upper most reaches of the river which highlights salmon are not utilising the entire river to spawn. However, both sites did achieve excellent classifications with 46 and 39 trout fry, which highlights the quality habitat available and an increase in recruitment at both sites. Fish passage works have been conducted at the Trewen site; salmon have not yet been recorded since the continuation of monitoring but it can take years for salmon to re-establish themselves in areas which they have not been present for prolonged periods of time. Although salmon are absent, this site does produce very high numbers of trout each year.

Crowdy, Stannon, Grey Lake, Coldrinick Stream, Nanstallon and St Laurance

These smaller tributaries were either absent of salmon or held very few. For example, Nanstallon had the most salmon fry recorded from the smaller tributaries with seven fry, an improvement from the absent classification in 2021. It was commented that the habitat was not very suitable for a fry survey, so after relocating the site 100 meters upstream in a shallow riffle, a number of fry were discovered. The Coldrinick Stream received a poor classification, with one salmon fry being recorded which is the lowest classification since 2018. This stream is very small and due to the 2022 drought and resulting low river levels, there was very little habitat present and may have displaced fish into other areas of the river or dropped back into the main river. High Steps on the Crowdy usually produces high numbers of trout and excellent classifications but unusually this year only produced four fish. US Allensford and US St Laurence Bridge all achieved good and excellent classifications for trout fry. Although most of the salmon

spawning occurred on the main River Camel, these surveys have highlighted the importance of these smaller tributaries for salmon and trout spawning. More so, it is imperative to have quality tributaries available for trout when competition is high from salmon on the main river and alternative habitat is available. Further surveying on similar tributaries in the Camel catchment would enable WRT to highlight where salmonid species are spawning to maintain good habitat or possibly highlight where habitat may need improving to be able to direct and target future work.

4. Recommendations

The WRT electric fishing surveys are undertaken to gain an understanding of year-on-year 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 recruitment of a species. 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 10) 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 10 represents the continuum of the three strategies and the goal for each waterbody (Table 11); to move all the Camel 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.

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 10 Defend/Repair/Attack strategy

Table 11 Camel sub catchment classification and DRA strategy.

Westcountry Rivers Trust Electrofishing Survey Report - River Camel, 2022

5. Acknowledgements

Westcountry Rivers Trust would like to thank all landowners who gave us permission to undertake surveys on the River Camel catchment. We would also like to thank the Camel Fisheries Association, Natural England, and the Environment Agency.