Results & Discussion

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.

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

3.4 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

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.

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

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.

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.