Electric Fishing Fry Index Survey - Exe

Electric Fishing Fry Index Survey

River Exe

January 2023

Hannah Winchester

Westcountry Rivers Trust Fry Index Survey Report - River Exe 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

With contributions by: Phillip Turnbull BSc MIFM

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 Fry Index Survey Report - River Exe 2022

Executive Summary

Westcountry Rivers Trust (WRT) undertook electric fishing (EF) surveys throughout the River Exe catchment during the summer of 2022. A reduced programme of 52 Fry Index Surveys were performed in the River Exe catchment to complement the Environment Agency (EA) Water Framework Directive programme of electric fishing surveys. Notable omissions from the Fry Index Survey included the main River Barle and Little Exe, due to high density of EA sites in these tributaries.

This report focuses on the WRT performed Fry Index Surveys (FIS) and the historic 15 year data set. The summer of 2022 was the driest since 1995 as well as the second hottest year on record, which emphasised the importance of ensuring open and free migration for migratory salmonids, with the 2022 FIS data providing consistent evidence for the Strategic Exe Weirs programme.

The Danes Brook was a new addition to the River Exe FIS programme and was revealed to be highly productive for both salmon and trout. This indicates the Danes Brook as a productive and important tributary, and it is recommended the Danes Brook remain a regular survey area in the future.

Other notable salmon observations include two excellent sites on the main stem of the River Exe, a good site in the Iron Mill Stream and low numbers of salmon were found at the most upstream site indicating a good degree of penetration within this tributary. Trout production was most notable in smaller rivers where salmon production was poor, including the upper Quarme, upper Dane’s Brook, upper Batherm and Upper Lowman, and particularly the River Pulham which produced excellent trout results throughout. 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.

1. Introduction

Westcountry Rivers Trust (WRT) undertook semi-quantitative fry index electric fishing survey (FIS) of the River Exe catchment in July-September 2022. This was the 15th year of fish monitoring undertaken by WRT and forms part of establishing a long-term dataset of semi-quantitative fry numbers. A total of 52 sites were surveyed during the 2022 season across the catchment. This is a reduced programme compared to recent years as the Environment Agency (EA) conducted a catchment-wide electric fishing programme as part of Water Framework Directive monitoring. The Fry Index Survey sites were chosen to complement the EA programme and provide additional data for a more complete assessment of Atlantic salmon recruitment.

Sites were selected in order to direct the survey for maximum benefit to inform future works, as discussed with the River Exe & Tributaries Association (RETA). The River Exe has the most developed Fry Index Survey data set in the south west, and it is hoped this highly valuable baseline data will continue to be collected in future years. This will enable production of project development bids based on evidence, and ensure available resources are targeted according to up-to-date knowledge of the fisheries production in the catchment. The River Exe Tributaries Association have been key in undertaking some of the fisheries management actions in previous years.

Figure 1 Survey site location, River Exe, 2022

2. Methodology

2.1 Electric fishing protocols

Electric fishing uses a controlled electric current to induce fish through various reactive stages, the most useful of which are stimulation of swimming toward an anode and temporary paralysis which enables easy capture by a hand net. When performed correctly by appropriately qualified and experienced surveyors it is the safest method of surveying regarding fish welfare, requiring minimal handling and ensuring all caught fish are released back to the same location in a time efficient manner. In upland streams and shallower sections of rivers, an electric fishing backpack can be used for portability and therefore this type of kit was used for all the Exe 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 include reduced mobility and increased time per site for effective survey. It Is therefore more costly than other approaches. With this method, an area of river is netted off and the fish are removed through a constant effort methodology 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 allows for an accurate estimation of the total number of fish in the surveyed area 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 often deemed 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 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 stop-nets, the survey is time-limited for active surveying (‘trigger-on’), whereby only fish caught within the set time limit are assessed. As no nets are deployed, fish in deeper sections of large rivers can frequently avoid capture using this method. It is therefore generally only suitable to assess fry habitat, as juvenile fish are most often restricted to shallower habitat, such as riffle habitat for salmonid species. Classified as a rapid methodology, time-based semi-quantitative electric fishing is cost-effective for a catchment-wide

application, and therefore highly suitable for index surveys. Index surveys are best used in conjunction with a programme of fully quantitative or area-based semi-quantitative methods, acting as complementary by providing a calibrated wide-area picture to compare to more detailed area-based methods.

In weighing up the pros and cons of the various approaches it is worth considering what would be required for a truly reliable method. It is often 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 several years. As such an effort is rarely practicable and may in fact 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 provide the desired outcomes as stated:

1. Guide current/future conservation strategies based on evidence, and

2. Identify whether or not the actions taken on the catchment have had a positive effect on fish recruitment

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 help 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/Restore’ conservation strategy framework which describes the appropriate habitat action depending on the ecological situations observed during surveys.

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 River Exe catchment 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

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

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.

2.4 Site Selection

Survey sites on the Exe were selected to provide representative samples from distinct river reaches, characterised by habitat type, proximity to barriers and proximity to targeted restoration works under the gravel augmentation project. Sites are proposed by WRT and RETA, selected to inform how best to utilise available resources and monitor the effects of delivered works towards the desired goals.

2.5 Field Sampling and Data Analysis

Permission for all sites was established before 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 aerated buckets 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 recorded and assigned post-hoc 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.

Data missing only relevant for some trout results between 2008-2010.

Length frequency histograms were used to identify age cohort size categories. Salmon fry were considered to be any individual that measured up to 110mm (Figure 3) and trout fry were considered to be any individual measuring up to 105mm (Figure 4).

Atlantic

Brown

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

Figure 3: Salmon fry length frequency distribution, River Exe 2022

Figure 4: Trout fry length frequency distribution, River Exe 2022

salmon frequency distribution, 2022

trout frequency distribution, 2022

3. Results & Discussion

WRT surveyed 52 semi-quantitative sites on the Exe Catchment between July and September 2022. Survey conditions were mostly optimal. It should be noted that summer 2022 was the driest since 1995 as well as the second hottest year on record. River water temperatures were closely monitored to ensure no surveying was performed when water temperatures exceeded 18°C, in accordance with Environment Agency guidance. The Exe catchment Fry Index Surveys were delayed until later in the season which reduced the risk of encountering conditions unsuitable for surveying

Providing justified reasons for the results on an annual basis can be challenging but examining the sub-catchments and sites through historic and comparable data helps highlight matters of concern and direct suitable actions to overcome them. Long-term data also highlights good examples and features that support populations in order to inform management. Fry index survey results indicate where action may be required and work best when combined with wider habitat/catchment observations and data. Fry index surveys can be invaluable for allocating limited resources for best effect, by providing catchment wide data, catchment wide ground observations, and a highly useful tool for assessing efficacy of mitigative action.

Table 2: River Exe semi-quantitative salmon and trout fry classifications including additional parr caught for 2022 (ordered from upstream to downstream)

Westcountry Rivers Trust Fry Index Survey Report - River Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River Exe 2022

3.1 Salmon and Trout Comparative Tables

Table 3: Salmon fry results including previous WRT data.

Westcountry Rivers Trust Fry Index Survey Report -

River Exe 2022

Westcountry Rivers Trust Fry Index Survey Report -

River Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River

Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River

Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River

Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River

Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River

Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River Exe 2022

Table 4: Comparative trout fry results including historic WRT data.

Westcountry Rivers Trust Fry Index Survey Report - River

Exe 2022

Westcountry Rivers Trust Fry Index Survey Report -

River Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River

Exe 2022

Westcountry Rivers Trust Fry Index Survey Report -

River Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River

Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River

Exe 2022

Westcountry Rivers Trust Fry Index Survey Report -

River Exe 2022

Westcountry Rivers Trust Fry Index Survey Report - River Exe 2022

3.2 Comparative Total catch and Distribution maps

Figure 5: Comparative total catch for salmon and trout, River Exe 2022

Figure 6: Salmon distribution and classifications, River Exe FIS 2022

Figure 7: Trout distribution and classifications, River Exe FIS 2022

3.3 Classification stacks & mean total fry per site

Figure 8: Stacked bar chart displaying annual percentage split of salmon fry classifications from 20102022.

Figure 9: Stacked bar chart displaying annual percentage split of trout fry classifications from 20102022

Exe Salmon Fry Classification Stack

Exe Trout Fry Classification Stack

Salmonid fry catch numbers for annual survey sites in the Exe catchment 2010-2022

3.4 Sub-catchment Discussions

Danes Brook

A new tributary for River Exe Fry Index Surveys, the Danes Brook is a tributary of the River Barle with the confluence a few miles upstream of Dulverton. Results suggested that all four sites were of good productivity for salmon and indicating that the Danes Brook is another Exmoor river of high importance for the River Exe salmon fishery.

The volunteer led redd surveys of winter 2021/22 confirmed this, with a high density of possible redd sightings recorded. It is recommended that the Danes Brook be included in the future FIS programme as an indicator of performance. This may not need to be every year depending on available resource.

The Barle and tributaries continue to dominate the salmon production in the River Exe, highlighting the importance of ensuring open access to and from this crucial recruitment habitat. The Strategic Exe Weirs programme is a key delivery mechanism for achieving this goal, and the annual Fry Index Surveys are an important evidence base to support continued efforts to delivery fish passage improvements between the Exe Estuary and Exmoor National Park.

Quarme

The River Quarme sites were restricted to the upper reaches of the tributary, to complement EA surveys lower in the catchment. Salmon production was poor, with the EA sites picking up a few juvenile salmon and WRT sites finding none. Conversely, the upper Quarme produced good to excellent results for trout for FIS sites. This may support the hypothesis that trout do well where salmon productivity is low, perhaps due to reduced competition. Following the Bridgetown Weir fish passage improvements, it will

Figure 10: Mean annual salmonid fry caught per site from 2010 - 2022

be interesting to see if salmon production increases in the Quarme system. Although the impact of multiple in-river barriers downstream of Bridgetown may still affect numbers of adult fish reaching the upper Exe, reducing the impact of this final barrier can only have a positive effect on fish reaching these upper reaches. It is recommended that the River Quarme continues to be a focus for opportunities to improve in-channel habitat and catchment management through programmes such as the River Exe Project and Headwaters of the Exe.

Pulham and Haddeo

Two sites on the Pulham and 12 sites on the Haddeo River were fished in 2022. The Haddeo sites are selected as part of monitoring of gravel augmentation and habitat improvement works under the South West Water gravel augmentation programme, these sites are discussed in a separate report.

Both sites on the Pulham were absent of salmon, with excellent scores for trout. This again highlights the importance of the Pulham for trout production in the Haddeo and upper Exe catchment. The lack of salmon production was disappointing when considering the excellent site in the lower Pulham in 2021. However, the increased production in the Haddeo may indicate that adult salmon did not penetrate as far up the river.

A Fisheries Water Bank release was coordinated in December 2021 in an attempt to attract fish into the upper Haddeo and potentially towards the Pulham. This was in part due to the excellent score in the Pulham 2021 electric fishing results. This may be a notable factor in the recording of salmon fry in the Haddeo upstream of Bury in 2022, but not as far as the Pulham. Fisheries Water Bank releases are a highly valued resource for fisheries management in the Exe catchment. However, releases are volumetrically and subsequently temporarily limited, and therefore effects on fish migration are unlikely to match more natural spate conditions. A release was also coordinated in December 2022 that was similar to the release of December 2021. Conditions in the Haddeo since the December 2022 release have remained similar to conditions following the December 2021 release e.g. no major spate conditions.

Brockey and Iron Mill Stream

The Brockey 2022 results were poor for both species, with no salmon found and very few trout fry by WRT. The Brockey received some gravel cleaning activity in the reach that produced a good salmon result in 2008, although this may be directly attributable to stocking activity. The gravel cleaning revealed severe sedimentation with limited mitigation opportunity with the chosen technique (water pump). Depending on results of the 2023 surveys, gravel cleaning may be adapted to a hand-tool approach to assess efficacy of this medium-term mitigation tool.

The Iron Mill Stream produced one good site for salmon fry; ‘D/S Iron Mill Bridge’. This is the best result achieved for salmon fry during WRT surveys, reasons for this are unclear. Riparian shade management and in-river habitat improvements are recommended as mitigation to attempt to improve salmon survival in the Iron Mill Stream. This should be

accompanied by continued volunteer-led redd surveys in the Iron Mill Stream to identify where spawning may be occurring with limited egg survival to summer fry to target mitigation efforts.

Elsewhere in the Iron Mill Stream salmon were either absent or present in very low numbers. However, one salmon fry was found at ‘Great Wood’ which indicates a high degree of penetration into the system, including traversal of notable in-river partial barriers and increasing confidence that further gains could be made for salmon in this tributary.

Batherm and Lowman

The Batherm returned good salmon fry near the confluence with the main River Exe. Trout fry were generally found throughout the system, with two good sites; one at North Hayne Farm and one at Batherm Bridge. The Batherm is a small flowing tributary and the good results near the confluence may be an indication that survival was limited by low flows upstream.

The upper Batherm has historically produced widespread salmon, albeit in low numbers, in 2012 and 2013, and around the Shillingford area in 2017. Further investigation is needed as to whether salmon were stocked in these years. Stocking or not, this shows that the upper Batherm is capable of holding juvenile salmon and is the preferred area for targeted works, preceded by walkover surveys to identify potential barriers.

The Lowman returned no salmon and a few trout fry, except for the most upstream site which returned a good result for trout fry. The low flow conditions in the Lowman did not inspire confidence of juvenile salmonid survival, with high levels of turbidity evident. It is no surprise to find the most productive site in the upper reaches where catchment activity has less potential to impact juvenile salmonids. The Lowman received some gravel cleaning activity in autumn 2022. Results from Fry Index Surveys in 2023 may feed into decisions of where to apply gravel cleaning effort.

Main Exe

The main River Exe was primarily surveyed for continuity, to highlight possible areas of juvenile survival during low flow years, and as an indication of possible areas for juvenile drift settlement. Notable salmon fry in the main river following a low flow year may indicate adult salmon failing to traverse River Exe barriers between Tiverton and Exmoor. The main River Exe is subject to regular high flows during winter and spring, and it would not be expected for high juvenile survival in any ‘normal’ year due to redd washout. 2010 produced some excellent salmon sites, although there is lack of regular data to enable further comment regarding how normal this was previously.

The number of Main River Exe sites was limited in 2022 due to a restricted programme, with chosen sites linked to research conducted by students from the University of Plymouth. Interestingly, in the exceptionally dry year of 2022, the Main River Exe north of Tiverton produced some good and excellent results, including 30 and 32 salmon fry found

at Hatswell and Cove Davis Beat, respectively. These sites contain classically identifiable salmon riffles; pool habitat followed by well sorted gravel riffles. As part of the student research, these sites received some gravel cleaning activity. However, due to these results it is recommended this is not repeated.

Trout fry were largely absent from the main river sites. This is not surprising given trout will generally migrate to smaller tributaries to spawn. Any baseline to compare to, is confounded by lack of recording of trout fry during the 2010 survey. It is recommended that sites in the Main River Exe upstream of Tiverton continue to be surveyed on a regular basis to assess the contribution of the main river against flow conditions that year. Following the exceptionally low flows of 2022, it will be worth considering 2023 results against the possibility of increased production in Main River Exe sites, although recent spate conditions may limit this.

It is recommended to consider continuous data loggers in the main river and/or regular reporting of water quality through the WRT Citizen Science Investigations (CSI) volunteer programme to establish baseline levels of pollution and catchment response to rainfall events. Capital grants for farmyard interventions can then be prioritised and further monitored to gauge their effectiveness.

The Calverleigh River

The Calverleigh River is heavily impacted by sediment. One salmon fry was found by WRT at the site near to the confluence with the main River Exe. This indicates that salmon will explore and use this tributary. No further salmon were found by WRT. Conversely, good numbers of trout fry were found by WRT at the upstream site. No trout were found at the confluence site. The Calverleigh has limited potential to contribute to the salmon fishery. Continued surveying allows to observation of the catchment, however targeted works or surveying should be prioritised in tributaries more likely to respond positively towards fishery production.

Culm and the Culm tributaries

The Culm has potential to provide refuge, spawning and rearing habitat for salmonids, with physical habitat structure suited to support salmonid fry populations. However, the River Culm has been well known for habitat degradation such as excessive sediment ingress and general poor water quality, as highlighted by the moving of the South West Water abstraction point upstream of the Culm confluence with the River Exe. There is continued effort through land-based projects in the River Culm catchment, which are to be encouraged and where appropriate partnered with to provide localised habitat improvements where historic data suggests previous salmonid recruitment success.

Salmon were absent from all sites in 2022 and trout fry were found upstream of Cullompton but not downstream. Though this is not fully conclusive due to the limitations of surveying small areas of river in a whole sub-catchment, it does again indicate the salmonid production is becoming increasingly pressured towards more upstream areas less at risk of catchment activities. The River Culm catchment is subject to multiple

projects, and requires significant improvements to catchment management to achieve notable salmonids fishery production improvements.

Large reaches of the river could be considered ‘lowland’ river, and subject to increased risk of high temperatures during summer months. Continuing to include the Culm in Fry Index Surveys would be useful for assessment and comparison to more upland tributaries in terms of value for salmonid recruitment. It is recommended that the Culm be included in long-term goals for temperature logging in the catchment.

4. Recommendations

4.1 Defend/Repair/Attack

The WRT EF 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. Where fry populations appear stable at within expectations for a low impact area, it is important that defence strategies are put in place to maintain good recruitment and to help restore numbers elsewhere in the Exe. In areas where fry have decreased then the attack or repair strategies should be implemented as appropriate and where funding allows.

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 RETA through the River Exe Project, following results from the fry index surveys. 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. DEFRAs Salmon Five Point Approach, habitat walkover surveys and genetic data) to produce assessments and recommendations for each sub-catchment of the river.

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 Exe 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.

Defend

Repair

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.

Maintain bag limits

Habitat Safeguarding

Catch and release

Assisted habitat recovery

Stock action Habitat

The DRA strategy for each sub catchment is summarised in Table 6, and high -level recommendations suggested in Table 7

Table 6: Exe sub catchment classification and DRA strategy.

Defend/Repair/Attack strategy

Sub-catchment

Calverleigh River

Culm

Average Fry Index Class & Conservation Strategy

Culm tributaries

Recommended works:

Gravel augmentation: Continue to trickle feed gravel, and sporadically 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 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 porosity 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.

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 life 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 and an important component of catchment management. Walkovers essentially build wide scale understanding of a catchment and allow forging of relationships with local landowners.

Interpretation signage: 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 at areas of increased public traffic to raise awareness of importance for salmonids

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. For example, assess FIS sites for applicability towards favoured management strategy –e.g., new sites to more accurately record impact of habitat targeted works. 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 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.

Table 7: Recommended DRA actions for Exe sub catchments

5. Acknowledgements

Westcountry Rivers Trust would like to thank all the landowners involved for their kind permission and keen interest. Thanks also go to Mike Holland, and the wider Fisheries & Biodiversity Team at the Environment Agency for the consent of selected sites and providing valuable extra data.

We would also like to thank the River Exe and Tributaries Association for donations towards the annual surveys. Special thanks go to Roger Furniss from RETA for informing the planning stages to direct the surveys to key areas within the catchment.

Westcountry Rivers Trust looks forward to continuing to work with RETA in building valuable data, guiding relevant management actions and taking part in discussions and action to restore the catchment.