TORRIDGE CATCHMENT FRY INDEX FISH SURVEY 2016
River Torridge
Report written by Adrian Dowding & Phil Turnbull
Rain-Charm House Kyl Cober Parc Stoke Climsland Callington Cornwall PL17 8PH Tel: +44 (0) 1579 372140 Email: info@wrt.org.uk Web: www.wrt.org.uk With special thanks to the financial support from the Torridge Fisheries Association and and With thanks to the BiffaAward ‘Restoring Freshwater Mussel Rivers in England’ project
Torridge Catchment Fry Index Fish Survey
2016
Contents 1.
Introduction .................................................................................................................................. 1 1.1 Freshwater Pearl Mussels ........................................................................................................... 2
2.
Field sampling and data analysis methods .................................................................................... 3
3.
Results........................................................................................................................................... 4 3.1
Summary ............................................................................................................................... 5
3.2 GIS mapping ................................................................................................................................ 7 4.
Discussion ..................................................................................................................................... 9
5.
Conservation and River Improvement Strategy .......................................................................... 12 Recommended Actions ............................................................................................................... 15
Summary Recommendations .............................................................................................................. 23 Hatchery release site recommendations .................................................................................... 24 Bankside tree management ........................................................................................................ 25 6.
Acknowledgements..................................................................................................................... 26
7.
References .................................................................................................................................. 26
8.
Appendix ..................................................................................................................................... 28 Torridge Catchment Salmon Classification Map ............................................................................. 28 Torridge Catchment Trout Classification Map ................................................................................ 29 Torridge Catchment Salmon Conservation Strategy Map ............................................................... 30 Torridge Catchment Trout Conservation Strategy Map .................................................................. 31
Table 1: Semi-quantitative abundance categories for salmon fry (Crozier & Kennedy, 1994) .............. 3 Table 2: River Torridge Survey sites and classifications for 2016 .......................................................... 4
Torridge Catchment Fry Index Fish Survey
2016
1. Introduction Measuring the state of fish populations in a river is essential to manage not only the fishery as a whole, but to gauge the health of the river and to predict future river issues that may require attention. The Westcountry Rivers Trust (WRT) performed semi-quantitative fry index electrofishing surveys across the length and breadth of the Torridge catchment in order to assess the juvenile populations of salmonids which are generally recognised as the most sensitive populations of fish to poor water quality, sedimentation and pollution events. This was the first year of fish monitoring of this type in the river Torridge catchment, and begins what we hope to be the establishment of a long term data set for the catchment, which is extremely valuable for keeping a continued ‘monitoring of the pulse’ of the rivers. The surveys were performed on a 35 site scale in 2016, with the aim to steadily increase this number as our understanding of the catchment increases, and landowner engagement continues. The first overview picture has been formed, which will aid in establishing areas to concentrate conservation efforts. The surveys were designed to complement the Environment Agency (EA) electric fishing monitoring undertaken annually, although both data sets use different methodologies with the primary difference being the use of fully quantitative depletion methods used by the EA and a semiquantitative fry index method used by WRT (to be detailed in field sampling and data analysis methods section). The strength of the fry index survey is to enable a quick, affordable, semi-quantitative, catchmentwide view of the fry (the first year or 0+ age group cohort) life stage only. As this survey is indicative of a single year, it is important to interpret the results with caution, however by looking at the first year life stage of fish there is merit through indications of how successful last year’s spawning was or how fluctuations in juvenile stock will transpose to future year’s breeding stock. This electro-fishing survey will aid as a tool to monitoring and inform appropriate habitat restoration works when funding is available. Survival of salmonid fry to the end of the first summer is known to be poor. Up to 90% of the alevins that emerge from redds will not survive. Even in good quality habitat with a rich food supply, high densities of fish will undergo strong competition for resources with each individual trying to gain a profitable feeding station. The fry index surveys are used as a coarse measure of fry abundance at each particular site. For each single year it also gives a broad indicator of salmonid spawning success across a catchment. The semi-quantitative methodology is primarily used as a means of guiding conservation and fisheries actions on the ground. It is less accurate than fully-quantitative depletion methodologies or single catch netted semi-quantitative surveys. Nevertheless, what this method lacks in terms of accuracy it makes up for in speed and efficiency. It is based on scientific study and can be calibrated to individual catchments by comparison to fully quantitative statistics. Using this method fisheries managers are able to trial and test conservation measures to best fit the catchment, using a
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repeating cycle of affordable monitoring and action, building site-specific knowledge and improvements over time - this flexible and responsive approach is known as ‘adaptive management’. In general the rivers of North Devon are short and steep in the headwaters with a spate (or flashy) characteristic nature. The upland reaches tend to be moorland (e.g. Dartmoor, Meddon) where rainfall falls on the oligotrophic moorlands and flows quickly downstream picking up little in the way of nutrients until it meets the lower sections of the main tributaries. Once out of the short upland sections the water flows through mid and lowland valleys where agriculture and forestry are the main surrounding land use with intermittent villages and towns before reaching the Taw and Torridge Estuary near Barnstaple. Typically, these rivers have the following issues relating to the success of salmonid fish: • • • •
Barriers to migration. Lack of functioning habitats. Degraded habitats (particularly at vital life cycle stages). Anthropogenic pressures in terms of modifications to aquatic environments, inputs from adjacent land management and infrastructure.
This report is to inform fisheries associations and catchment partner groups of the results from the surveys undertaken by WRT in 2016 and to advise on fish habitat improvements and management. WRT and the wider catchment partnership will work towards a full Catchment Fisheries Programme in the future.
1.1 Freshwater Pearl Mussels Westcountry Rivers Trust (WRT) has joined in partnership with Devon Wildlife Trust (local lead partner), North Devon Biosphere Service, Tarka Country Trust and the Environment Agency, to protect and restore the freshwater pearl mussel (FPM) populations in the South West of England. As part of the larger national project (Restoring Freshwater Mussel Rivers in England) lead by the Freshwater Biological Association in Cumbria, WRT has been involved in the creation of a captive rearing facility, which has provided success in the production of a new generation of FPM to be introduced into the River Torridge. Freshwater pearl mussels’ life cycle is inextricably linked to the salmonid fish (salmon and trout) in that the FPM must spend approx. 10 months clamped onto the fish’s gill filaments. A good abundance of fish and gills is therefore essential to the survival of FPM as both the fish and mussels have the ecological survival strategy of producing many offspring with a low probability of surviving to adulthood. Fertilised FPM eggs develop in a pouch on the gills of the female mussel, and released between June – September as tiny larvae (0.6 - 0.7mm) called glochidia. Resembling tiny adult mussels, the glochidia drift in open river water until they come in contact with fish gills, where they clamp onto the gill filament and grow in the hyper-oxygenated environment. Although technically a parasitic action, the mussels appear to cause no harm to their hosts. In the following April-June they detach and settle in clean sand or gravel, achieving effective dispersal within the river system. Of particular importance for this life-stage is the presence of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta). To supplement the work of the captive rearing facility, WRT performs fish surveys
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within the River Torridge to identify whether natural fish populations are present to support the FPM life cycle in an area. Furthermore, WRT carries out water quality testing, to help identify areas where remaining FPM can thrive, and help determine the reasons why the natural populations have been in decline. The neighbouring River Taw catchment presents an even further impacted FPM population, and it is hoped that the successes from the Torridge FPM reintroduction program can inform on how a similar program can be successfully implemented to help save the River Taw FPM, and keep this fascinating and important species thriving in North West Devon rivers.
2. Field sampling and data analysis methods Each site was electro-fished by a two-person team using an electrofishing single anode backpack. The surveys were fished at the same settings of 50Hz with a voltage setting appropriate to the conductivity of the water. The operatives fished continuously for a standard five minutes within fry habitat where sufficient area was available. 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. Based on the lengths of fish captured during the survey, first year ‘fry’ life-stage fish were determined by working out the length frequency and separating the age class based upon the modal distributions. Fry numbers recorded at each site were classified as excellent to poor (or absent) according to the methodology by Crozier & Kennedy (1994) (Table 1). The classification scheme has been taken from the original salmon fry index provided within this paper and was derived through establishing a relationship with equivalent fry numbers captured within quantitative surveys at sample sites within Ireland. Within this assessment report, the salmon fry classification has been used as a surrogate for trout fry. Results should therefore be treated with some caution. It would increase the robustness of the method to be calibrated to local conditions, and for trout, to conduct the method alongside Environment Agency quantitative electric fishing surveys in future years.
Table 1: Semi-quantitative abundance categories for salmon fry (Crozier & Kennedy, 1994)
Density Classification
Semiquantitative (n/5min fishing)
A (excellent) B (good) C (fair) D (poor) E (absent)
>23 11-23 5-10 1-4 0
Quantitative (n 100m2) >114.7 69.1-114.6 41.1-69.0 0.1-41.0 0
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Any fry that were missed or escaped during electro-fishing were noted and assigned to either the trout or salmon group depending on the relative percentage of each species recorded at the site.
3. Results WRT surveyed 35 sites within the River Torridge catchment as part of the 2016 season. These sites were chosen under the criteria of widespread surveying across the catchment, in areas expected to act as sites for migratory salmonid recruitment. Table 2 shows the results from the surveys based on Salmon classifications as determined in Crozier and Kennedy (1994) above.
Table 2: River Torridge Survey sites and classifications for 2016
River
Site Name
2016 Trout Class
2016 Salmon Class
Hatchery Release (2016)
Torridge
Fordmill Farm
Poor
Absent
Torridge
West Putford
Absent
Absent
Whiteleigh Water
Weekpark Plantation
Absent
Absent
River Waldon
Bradworthy
Poor
Absent
River Waldon
Sutcombe Bridge d/s Heddon
Absent
Absent
Torridge
Black Torrington
Absent
Absent
Mussel Brook
u/s Westover Bridge
Absent
Absent
Wagaford Water
Stewdon Moor
Absent
Absent
River Lew
Lewer Bridge
Absent
Absent
River Lew
Hatherleigh, Littlewood
Absent
Absent
River Lew
d/s Crowden
Absent
Poor
Northlew Stream
Ashbury
Poor
Poor
✓
River Lew
South Yeo, Northlew
Absent
Poor
✓
Hookmoor Brook
Lower Gorhuish Br.
Absent
Poor
✓
Medland Brook
Stocken Bridge
Absent
Absent
✓
Scobchester Stream
Broomshill Bridge
Poor
Absent
✓
Jacobstowe Stream
Niases Farm
Poor
Absent
✓
Beckamoor Brook
Jacobstowe
Absent
Poor
✓
Monkokehampton Mill Leat
Hatchery Leat
Absent
Good
✓
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✓
Torridge Catchment Fry Index Fish Survey
River
Site Name
2016
2016 Trout Class
2016 Salmon Class
Okement
South Dornaford
Poor
Absent
Eoke - Fatherford Moor Brook
Lower Halstock
Absent
Absent
East Okement
Okehampton
Absent
Good
West Okement
Meldon
Poor
Poor
Hole Brook
Monkokehampton
Poor
Poor
Dolton Brook
d/s Dolton Brook, Brightley
Poor
Absent
Little Mere
Mere South
Absent
Absent
River Mere
Mere North
Poor
Absent
River Mere
Merton Mill
Absent
Absent
Woolleigh Brook
u/s Bridge Woods
Absent
Absent
Torridge
Warham Loop
Absent
Absent
Torridge
Blinsham Loop
Absent
Absent
Torridge
Darkham Loop
Absent
Poor
Langtree Lake
Clements Hill
Absent
Absent
Monkleigh Stream
Old Quarry
Absent
Absent
Huntshaw Water
Huntshaw Mill Bridge
Absent
Absent
Hatchery Release (2016)
3.1 Summary Salmon Atlantic salmon fry were absent from many sites in the 2016 survey. Sites that would have been expected to provide some evidence of salmon recruitment, for example the Warham Loop, Blinsham Loop, and sites where hatchery reared fry were released, provided no evidence of survival to the latter summer period. Where salmon fry were recorded, abundance was very low and specimens often appeared emaciated. The River Okement and East Okement provided exceptions by scoring Good at the Hatchery Leat and Okehampton sites, respectively. The Okehampton site in particular is of high interest, as no hatchery release is conducted here, whereas the Hatchery Leat site received hatchery reared salmon fry in winter-spring 2016. These sites, and particularly the Okehampton site, were characterised by clean, highly suitable gravel matrices and well oxygenated flows, providing clean riffle for egg survival and subsequent fry habitation. Other hatchery release sites provided Absent or Poor scores, usually linked with very low flows at the fishing sites. Some sites identified to survey within the catchment were impossible to fish due to 5|P age
✓
✓
Torridge Catchment Fry Index Fish Survey
2016
no physical water flow. Hatchery release sites that were found to have no river flow and therefore no fish survival were Dunsland Brook (South Hathersly) and Berrydown Stream (Berrydown). These sites are not detailed in the above table as they were not fished, but would likely have added to the ‘absent’ results had fishing been possible. Furthermore, the Beckamoor Brook (Jacobstowe) release site was exceptionally low, leading to a 3-minute survey, cut short due to high risk of damage to surviving/resident salmonid fry. River gravel concretion was frequently encountered, due to high levels of interstitial sediment loads, often accompanied by smothering algal growth when light penetration allowed. However, many of the survey sites were considered as significantly over-shaded, either by unmanaged bankside tree growth or highly incised banks.
Trout Trout fry abundance was similar to that of salmon fry, with many sites producing no trout fry. Trout scores for fry abundance did not raise higher than Poor, indicating the severity of gravel sedimentation. Where salmon were recorded without trout presence, the habitat was much more favourable for salmon fry. Excluding the Okement, trout fry condition appeared to be generally of higher quality, indicating the increased resilience of brown trout over Atlantic salmon. However, the Absent and Poor scores indicate severe habitat degradation throughout the Torridge catchment, presenting largely as high sediment loads, severe bank incision, over shading, algal growth, and bankside poaching from livestock.
The classification and the conservation strategy figures below are displayed at A4 page size in the Appendix.
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3.2 GIS mapping
Figure 1: Location of survey sites (left) and relative catch for brown trout and Atlantic salmon (right)
Figure 2: Total Atlantic salmon catch (left) and salmon classification (right)
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Figure 3: Total brown trout catch (left) and trout classification (right) The GIS maps for both salmon and trout (Figure 1) reveal the highest abundance for young of the year (0+) fish is located in the South East of the River Torridge catchment. The South East of the catchment consists of the River Okement, which springs from the North of Dartmoor, and consequently flows with oligotrophic moorland water less impacted through land management pressures. As a result, the habitats encountered were notably less sedimented and produced very low conductivity readings (40-60ÂľS), suggesting low input from anthropogenic activities. Due to the reduced impact, the river Okement, and in particular the East Okement, is a highly important recruitment area for salmon in the Torridge catchment. Elsewhere in the catchment, absent or poor scores were recorded, revealing the severity of impacts from agriculture, forestry, urbanisation and other industry on the river Torridge and tributaries. Trout were recorded within the upper reaches of the River Torridge catchment, however again in low abundance. It worth noting that the number of sites fished is limited in the upper reaches. Westcountry Rivers Trust (WRT) aims to increase the number of sites surveyed to further the accuracy of results displayed, and better inform targets made under the Conservation Strategy outlined in section 5.
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4. Discussion Fish are a highly effective ecological quality indicator due to a proven sensitivity to a range of environmental pressures and subsequent habitat degradation, and have been used as a key biological quality element for assessment under major legislation, namely the Water Framework Directive. Migratory fish species, for example anadromous salmonids, are vulnerable to diverse pressures across a range of habitats, due to use of extended aquatic ecosystems during various life stages. Therefore, they act as high quality indicators for overall ecosystem integrity and connectivity. Salmonid sensitivity to environmental pressures is particularly evident through early ontogenetic (development) stages. Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) spawn by making depressions in appropriately sized gravels to form a redd, into which eggs are laid, fertilised and buried. To supply the eggs and newly hatched progeny (alevins) with oxygen, water must be able to flow through the interstitial spaces within the substrate. Therefore, sedimentation of river gravels disrupts salmonid recruitment through mechanical blockage of spawning gravels, causing asphyxiation of eggs and alevins, and can produce a concretion effect providing a difficult substrate through which to dig. Furthermore, excess organic matter through anthropogenic introduction, and reduction of metabolic waste removal through restricted flows, can increase the local biological oxygen demand (BOD) within the redd and surrounding aquatic environment, causing bacterial activity to strip the water of available oxygen leading to further respiratory distress. Small increases in sediment input is often reflected in salmon and trout recruitment success. Once free swimming, salmon and trout fry (young of the year/0+) feed primarily on a varied diet of macroinvertebrate species. Freshwater macroinvertebrates are sensitive to a range of pollutants, with a decreased ability to locally migrate compared with fish species. Therefore, habitat degradation in the form of pollution will negatively impact macroinvertebrate community diversity and abundance. Consequently, this will impact the success of local salmon and trout recruitment. In addition to the necessity for connectivity throughout the system, a high level of natural habitat complexity is necessary to provide adequate shelter for individual fish throughout freshwater growth stages, therefore a high fry abundance is reflective of good physical habitat quality. Therefore, WRT believes that conducting catchment scale surveys for the presence and abundance of salmon and trout fry helps to indicate the general health of a river system, and supports in the effective application of resources to tackle negative impacts. Moreover, angling is an important economic factor in many rural areas in the UK; salmonid species are of particular interest in the South West of England. Thus, the monitoring of salmon and trout population recruitment success, and consequent management decisions, have a far-reaching impact on the livelihood of residents in the West Country. The results from the 2016 Torridge catchment fish surveys reveal a poor year for recruitment. Weather patterns are likely to have had significant impact on the success of salmonid spawning. Autumn 2015 produced the third lowest average UK rainfall figures since 1914, followed by a persistent sub-tropical airflow between November ’15 and February ‘16. Coupled with above average sea surface temperatures, periods of intense rainfall from notable low pressure events caused average river flows in the South West to range between high and exceptionally high through January, and remaining above normal in February (for more, please refer to Marsh et al., 2016). 9|P age
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Atlantic salmon eggs are extremely fragile until development into eyed ova (formation of embryo), typically after ~245 degree days. At normal January river temperatures, this equates to approximately a one month period. Strong winter river flows can cause severe mechanical damage to salmonid spawning redds, thus significantly impacting survival of delicate eggs. This period of high flows was followed by a dry summer in 2016, resulting in severe low flows by September 2016 in many upper reaches of the Torridge catchment. Combined, the high winter and low summer flows created difficult conditions for salmonid fry survival in smaller upstream tributaries. Historical manipulation of river channels, presenting mainly as canalisation for land drainage, further exacerbates the effect of flows, producing high energy chutes with uniform bank and substrate structures which provide little shelter in high flows, and quick drainage of systems in low flows. Additionally, compacted soils from modern agricultural practices further contribute to the significant flashy nature of headland waters. However, further downstream areas of increased habitat complexity and observed good flows throughout the summer, for example the Warham, Blinsham and Darkham Loop sites, still produced Absent or Poor results. Sedimentation of spawning habitat was high at many of the survey sites, with severe sediment input witnessed across the Torridge catchment. Due to a combination of land drainage, channel modification, and a shift to more frequent extreme rainfall events, many rivers in the clay soil areas of North West Devon have become highly incised through excessive erosion of river banks and bed. Soil erosion is well documented as a major source of sediment in river channels. Animal access was frequently observed, with bankside poaching and consequent lack of marginal plant growth presenting a regular input of sediment, especially within smaller tributaries. The lack of marginal growth was often exacerbated by over-shading from unmanaged bankside tree growth. Good light penetration at spawning habitats is important to maximise productivity through the food-web, ensuring high holding capacity for salmonid fry. However, in some areas of good light penetration, high levels of input from enriched run-off and sediment-bound nutrients produces eutrophic conditions and subsequent excessive algal growth. Therefore, increasing light in key areas may have the negative effect of smothering of fry habitat with algae, reducing suitability for diverse macroinvertebrate communities. Thus, increasing light penetration must be accompanied by addressing nutrient and sediment input. The notable exception to the above was the Okehampton (East Okement) site. Due to the proximity to Dartmoor National Park, and significantly less impacted nature, a “Good” classification for salmon was awarded. Although heavily shaded by mature trees, and the A30 road bridge, this site was characterised by little sediment accretion and highly oxygenated water of much reduced input from agriculture and urbanisation. This suggests that the presence of sediment is a major factor to consider when relating to salmonid fry abundance. The other site to be awarded a “Good” classification for salmon was the Hatchery Leat (Okement) site. However, this may have been confounded by the addition of stock from the salmon hatchery. A total of 11 sites were stocked with fry from the salmon hatchery. Five of these sites returned positive catch results, six of them returned no catch. Of the five sites that did return catch results, four achieved a “Poor” score, with specimens appearing of low condition factor. Observations indicate a lack of suitable habitat, primarily flow and gravel matrices, to be a likely reason for poor returns. The one site that produced a “Good” return was in the River Okement, which presents more suitable habitat and increased flow from Dartmoor headwaters. Due to the proven migration 10 | P a g e
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of adult returning salmon through the River Okement to the Okehampton site, it is unclear as to whether the “Good� result recorded from the Hatchery Leat site is due to the effective stocking from the hatchery, or from natural spawning from returning adults. Regular monitoring is necessary to assess the effectiveness of the hatchery release at this site, with a planned break in stocking to determine the source of surviving fry or an effective way of marking released fish for identification. Due to the discussed environmental pressures, it is imperative that existing migratory salmonid populations have open passage throughout the catchment, ensuring a healthy distribution. Not only does this increase the holding capacity of a system due to increased habitat availability, but it also helps to protect the catchment scale population from isolated pollution or low flow incidents. Barriers to migration can therefore severely impact the stability and robustness of catchment scale fish populations. A migration barrier is any object or activity that causes unusual migration behaviour, due to induced stress or avoidance of unfavourable conditions. Thus, altered distributions of spawning populations may result, causing increased density of spawning activity and subsequent progeny habitat usage. This acts to decrease the population potential through intense resource competition. It is recommended that potential migration barriers be identified throughout the Torridge catchment, with the intention of performing coarse resolution rapid assessments to produce options appraisals for advice on improving fish passage. The Torridge electrofishing surveys in 2016 have begun to establish a baseline upon which we can build to show a consistent annual reflection of the fish health in the catchment. As the data sets continue and develop over time more sites will be added to define more detail and increase accuracy for informing management decisions. It is important to maintain the full catchment coverage to monitor and detect issues or negative trends in the early stages.
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5. Conservation and River Improvement Strategy The above evidence needs to be used to provide the most effective outcomes in dealing with the state of fish populations and our catchment river’s health in general. Using the Fry Index classifications there needs to be priority areas within the catchment that are targeted for conservation activity. This strategy broadly follow the Defend/Repair/Attack concept developed by Ronald Campbell of the Tweed foundation, and has been applied locally in the Exe catchment by the RETA/WRT surveys that have been conducted for a number of years now. The fry productivity of the rivers is assessed by a combination of data over the last five years semi-quantitative electrofishing results, alongside EA quantitative electrofishing sites where possible. These results are then applied in context of existing knowledge (e.g. plans, habitat walkover surveys, and genetic data) to produce assessments and recommendations for each sub-catchment of the river. These sub-catchments are classified according to three levels: Defend, Repair, and Attack.
Defend These areas have good fish stocks and habitat, and need safeguarding actions to ensure no decline occurs. Repair 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. Attack 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. Please note these do not relate to the Water Framework Directive (WFD) classifications.
Whilst this provides a useful structuring framework, and something of a ‘traffic lights’ system, reality is always complex and lies on a continuum between these extremes. A useful way to visualize this continuum is the inverted pyramid figured below. The goal of this report is to move the subcatchments of the Torridge up the pyramid 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, major interventions such as habitat re-engineering or the possibility of 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. 12 | P a g e
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Such actions can involve the third and volunteer sectors as well as statutory bodies, for example a fishing club may choose to adopt catch and release in a poorly performing tributary, but only maintain bag limits on those that are doing well, without the EA having to resort to Bylaw restrictions.
Figure 4: Fish conservation management developed by the Tweed Foundation.
Table 3 shows the management recommendations for the Torridge catchment, divided into subcatchments. Conservation strategy recommendations have been made in accordance with the current Fry Index results following the above attack/defend continuum. It may be of benefit to assess if these geographical divisions of the Torridge into sub-catchments are biologically divided as well (i.e. separate fish populations per sub-catchment). This can be achieved by using genetic markers to identify the populations within the catchment. The Water Framework Directive fish category status has been included for comparison. It is apparent that the data collected by Westcountry Rivers Trust contrasts with the WFD status for most sub-catchments. The Whiteleigh Water and Mussel Brook differ only slightly, and may be due to conditions on the day dictating population distribution. The discrepancies observed may be due to the difference between the data year used for WFD status. Furthermore, WFD status data is based on a small frequency of fully quantitative surveys, whereas the Fry Index Class data is based on catchment wide semi-quantitative surveys. Different data sets act as complimentary to help build a more complete understanding. WRT suggests deciding action plans based on catchment scale data to increase effectiveness and efficiency regarding resource management.
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Table 3: Average fry index class for the River Torridge sub-catchments, including Conservation Strategy status. Water Framework Directive fish status data based on latest data. Average Fry Index Class Conservation Strategy
Sub-Catchment
Trout Upper Torridge
Salmon
Water Framework Directive WFD Fish Status
Absent
Absent
Good
Attack
Attack
(2014 cycle 1)
Poor
Absent
High
Attack/Repair
Attack
(2015 cycle 2)
Whiteleigh Water
Absent
Absent
Poor
Attack
Attack
(2015 cycle 2)
Mussel Brook
Absent
Absent
Poor
Attack
Attack
(2015 cycle 2)
Absent
Poor
Attack
Attack/Repair
Poor
Fair
Attack/Repair
Repair
Poor
Absent
Attack/Repair
Attack
Absent
Waldon
Lew
Okement
Dolton
Mere
Lower Torridge
Woolleigh
Langtree
Huntshaw
Good (2015 cycle 2) Good (2014 cycle 1)
Reasons for not achieving Good n/a
n/a
Suspect data Probable mixed agricultural, sediment, fine sediment n/a
n/a
Not available
n/a
Absent
Moderate
Attack
Attack
(2015 cycle 2)
Probable mixed agricultural, sediment, fine sediment
Absent
Absent
Attack
Attack
Not available
n/a
Absent
Absent
High
Attack
Attack
(2015 cycle 2)
Absent
Absent
Moderate
Attack
Attack
(2015 cycle 2)
Probable mixed agricultural, nutrients, phosphate
Absent
Absent
Attack
Attack
Not available
n/a`
n/a
Table 4 identifies key recommended actions related to the attack/defend Conservation strategy outlined above. A description of the recommended actions, outlining the key objectives for each action, is included below.
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Recommended Actions FENCING: Riparian zones identified as receiving significant livestock access, with apparent habitat degradation, should be fenced to limit trampling and bank side poaching. To include measures ensuring livestock drinking water supply is not impacted. Effective buffer strips dependant on site characteristics is advised. Wide margins and new tree planting may help stabilise banks. COPPICING: Targeted selective coppicing of woodland and abandoned riparian coppice adjacent to juvenile habitat riffles should be carried out. 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. GRAVEL CLEANING: Key areas of high spawning potential have been identified, however high sediment loads impact viability and survival of early life stages. Whilst continued efforts are underway to influence policy and land management practices, selective gravel cleaning should be carried out to ensure available spawning habitat for the coming season. 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. FARM ADVICE: A key management strategy for the protection and enhancement of riverine systems. Approaching and working with local agricultural businesses to offer guidance on best environmental practice, and the use of grants for application of the recommended actions outlined. 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. DATA LOGGERS: Install water quality data loggers at key sites. This will define the water quality indicators and produce a tracing mechanism for potential negative inputs to the river. An advanced technique for areas where specific potential issues have been identified. Loggers can be moved to further identify and trace issue to specific locales. WALKOVER SURVEYS: Recording of habitat availability relating to ontogenetic stages of fish, including observed local land use and factors negatively impacting habitat quality. A highly important component of catchment management, essential building large scale understanding of a catchment, and engagement with local land owners. Often the starting point for work in an area and building a current picture of the river system.
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Table 4: Recommended actions for the River Torridge Sub-catchments, based on the Conservation Strategy outlined in section 5
Action Sub catchment
Fencing
Coppicing
Gravel Cleaning/Restore
Erosion Control
Fish Passage Assessment
Land Management Advice
In-Channel Habitat Restoration
Data Loggers
Walkover Surveys
Upper Torridge
✓
✓
✓
✓
✓
✓
✓
✓
✓
Waldon
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Whiteleigh Water Mussel Brook
✓
✓
✓
✓
Lew
✓
✓
✓
✓
✓
✓
✓
Okement
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Dolton
✓
Mere
✓
Lower Torridge
✓
Woolleigh Langtree Lake Huntshaw Water
✓
✓ ✓
✓
✓
✓
✓
✓
✓
✓
✓ ✓
✓
✓
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Salmon
Figure 5: Torridge Salmon Conservation Strategy map. White zones indicate areas where no data was collected in 2016.
Figure 5 indicates the general distribution for juvenile (0+ age group) Atlantic salmon abundance across the Torridge catchment, relating to the Conservation Strategy. The map indicates a general distribution towards the Southern areas of the catchment. The Northern area of the catchment, which includes the majority of the main river Torridge, presents a lack of juvenile Atlantic salmon observed during the 2016 electrofishing surveys. The river Lew catchment shows a general repair/attack strategy, due to the average “Poor” scores relating to very few 0+ Atlantic salmon found. The main Okement and East Okement provide a more positive average, due in part to the “Good” scores from the East Okement. It is therefore of high importance that this area receive attention to protect from further degradation. It is worth noting that the number of surveys in the Torridge catchment is still at a reserved density. Increasing the number of surveys will help further identify areas in need of immediate attention, and increase the accuracy of results and consequent management strategies. 21 | P a g e
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More information may be needed to determine where conservation efforts are best placed in the near future. With such low or absent numbers in the North half of the catchment, there may be inherent problems that need addressing before attempting to improve the direct fish habitat. It is known that the main River Torridge (through expert opinion associated with the freshwater pearl mussel project) suffers with a lack of river bed armouring and gravel conveyance in terms of geomorphology. The river bed composition is integral to survival of the fish life cycle and needs to be addressed. The power within the Torridge is perceived to be greater in recent history with the river reacting to rainfall quicker and rising and falling in level more quickly. This means more water is being conveyed at peak flow times and thus more energy and power exists to move the river bed. A river system is supposed to have an equal amount of bed load conveyance as there is gravel recharge, i.e. gravel entering the river system. When the balance is disrupted the net result is for gravels to deplete and the river shows areas of exposed bedrock which are not conducive to fish spawning.
Trout
Figure 6: Torridge Trout Conservation Strategy map. White zones indicate areas where no data was collected in 2016.
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Figure 6 indicates the general distribution for 0+ brown trout abundance across the Torridge catchment, relating to the Conservation Strategy. The brown trout map contrasts with the Atlantic salmon map by displaying increased abundance at the upper most reaches of the catchment (source to Dipple Water), reflected also in the Dolton Brook. However, a repair/attack strategy due to average “Poor� scores is still of highest concern. The river Lew and Okement catchments present reduced abundance compared to A. salmon. The severe low flows encountered in the upper reaches and headwaters, habitats of which brown trout are naturally more able to utilise, may account for the poor recruitment witnessed by the 2016 electrofishing surveys. It is important that yearly monitoring continue to ensure trends can be recognised to help focus resources for the most effective outcomes. It is worth noting that the number of surveys in the Torridge catchment is still at a reserved density. Increasing the number of surveys will help further identify areas in need of immediate attention, and increase the accuracy of results and consequent management strategies.
Summary Recommendations Tree and bank management to protect against erosion and stabilise river banks is necessary across the upper catchment, whilst improving and enhancing in-river fish habitat through woody debris introduction. Livestock access is severe in the Upper Torridge and associated tributaries. Areas of highest impact can be identified through walkover surveys. The concept of walkover surveys to detail fish habitat is highly recommended as the surveys qualify and quantify available habitat whilst at the same time provide direct observations throughout the catchment which help identify river protection aspects. This will help increase the accuracy of resource prioritisation. Gravel cleaning would be beneficial in areas where we know fish get to, mainly in the Okement and Lew sub-catchments, to help maximise the survival of current wild Torridge salmon stocks. Fish migration access is extremely important in the Torridge: possibly more so where cumulative factors mean that overall survival of diadromous fish appears low. It is recommended that a SNIFFER rapid coarse migration assessment be conducted on known downstream weirs to incorporate a scientific evidence base with observed migration, and to qualify if expenditure is justified in improving the migration for all fish species across the Torridge catchment. Continued water monitoring through the FPM project, and tracing upstream to locate areas of highest input. Once major input is identified, expertise within the WRT can be employed to work with the affecting industry and reduce impacts on the rivers. Gravel reintroduction in the Upper Torridge may restore spawning distribution potential. This is a very real possibility based on historic dredging (since stopped) for flood defence at Taddiport. Assess whether the Torridge salmonid fish species are genetically different from the Yeo (Bideford) and Duntz sub-catchment and assess whether the fish are likely to be unique to this sub-catchment or diverse throughout the Torridge. If these fish are likely to intersperse then the Yeo 23 | P a g e
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(Bideford)/Duntz sub-catchment should be considered for inclusion in future surveys as it is a large catchment area that may include possibility for improving total Torridge fish populations.
Hatchery release site recommendations Recommended areas for hatchery reintroduction Site
Grid Reference
Notes
Hookmoor Brook, Lower Gorhuish Bridge
SX 53107 98728
Northlew Stream, Ashbury
SX 50935 97569
Could increase stocking around this area
Monkokehamoton Mill Leat
SS 58022 05318
Good catch in main channel close by (SS 57829 05447)
Dolton Brook site
SS 55811 11594
Multiple small riffles in area
Medland Brook, Stocken Bridge
SS 55167 00448
East Okement, Fatherford Moor Brook
SX 59963 93670
Waldon, Sutcombe Bridge
SS 36352 10519
Could include a second site on the Waldon
Lew, South Yeo Northlew
SS 51332 00803
Could increase stocking around this area
Darkham Loop, d/s of weir*
SS 50271 17152
Poor catch in 2016
Areas where reintroduction took place in 2016, but considered high risk due to summer flows Site
Grid Reference
Beckamoor Brook, Jacobstowe
SS 58092 01963
Scobchester Stream, Broomshill Bridge
SX 51376 98058
Dunsland Brook, South Hatherleigh
SS 54302 03868
Berrydown Stream
SX 60557 98938
Jacobstowe Stream, Niases Farm
SS 58854 00951
Langtree Lake, Clements Hill
SS 46637 17389
Notes Survey cut short due to high risk of damage to surviving salmonid fry.
Highly silted, limited survival potential, consider seeding tributary south of carpark at SS 46830 17469.
Through the dedication of the Torridge Fisheries Association volunteer salmon hatchery programme there is the opportunity for salmon fry to be reintroduced to the River Torridge at or near FPM sites. The introduction at one or many of these sites would be advantageous to the conservation of this protected species.
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Bankside tree management Below are some examples of rivers in the catchment with common noted river protection possibilities. A high proportion of sites surveyed were over-shaded (Pic 01) and tunnelled (Pic 03) and would benefit greatly from selective coppicing to allow in sunlight and possibly laying of smaller stems in line with the river flow to provide some bank protection and woody debris introduction. Site (Pic 02) along Northlew is a good example of what some of the head waters could look like, and so is the (Pic 04) on the Waldon, although invasive non-native Himalayan Balsam is a problem. Site
01
02
03
04
05
06
(06) is highly silted, but recently fully coppiced which could be thought of as extreme in terms of light introduction (depending on full reason for coppicing), but shows positive bank regrowth and stabilisation. Livestock access was duly noted in multiple areas and it is recommended that this be 25 | P a g e
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stopped altogether, or at least controlled. Woody debris (Pic 05) may need managing to prevent blockages in the form of debris dams, but could be realigned to keep the benefits of woody debris habitat in the water whilst reducing flood risk or potential migration obstacles.
6. Acknowledgements This work could not have taken place without the financial support of the Torridge Fisheries Association for which Westcountry Rivers Trust and the wider North Devon Catchment Partnership are very grateful. The survey was additionally supported by the BiffaAward ‘Restoring Freshwater Mussel Rivers in England’ project and we acknowledge grateful thanks for both funds, without which the surveys couldn’t have taken place. Local knowledge and voluntary input from the Torridge fisheries group who meet quarterly is also very appreciated as this helps bring a lot if information together in one room on a regular timetable and co-ordinates the fisheries activity in the catchment. Westcountry Rivers Trust could not perform this valuable work without the co-operation and kind permission of the multitude of land owners, river owners and tenants looking after the area. We thank you for working with us and supporting us in our work and hope to build an ever increasingly positive relationship for your businesses and the river.
7. References Armstrong, J.D., Kemp, P.S., Kennedy, G.J.A., Ladle, M. and Milner, N.J. (2003). Habitat requirements of Atlantic salmon and brown trout in rivers and streams. Fisheries Research. 62(2): 143-170 Collins, A.L., Walling, D.E., Stroud, R.W., Robson, M. and Peet, L.M (2010). Assessing damaged road verges as a suspended sediment source in the Hampshire Avon catchment, southern United Kingdom. Hydrological processes. 24: 1106-1122 Crozier, W.W. and Kennedy, G.J.A. (1994). Application of semi-quantitative electrofishing to juvenile salmonid stock surveys. Journal of fish biology. 45(1): 159-164 Everard, M. and Kataria, G. (2011). Recreational angling markets to advance the conservation of a reach of the Western Ramganga River, India. Aquatic conservation: Marine and freshwater ecosystems. 21(1): 101-108 Franssen, J., Blais, C., Lapointe, M., Bérubé, F., Bergeron, N. and Magnan, P. (2012). Asphyxiation and entombment mechanisms in fines rich spawning substrates: experimental evidence with brook trout (Salvelinus fontinalis) embryos. Canadian journal of fisheries and aquatic sciences. 69(3): 587599 Hawkes, H.A. (1998). Origin and development of the biological monitoring working party score system. Water research. 32(3): 964-968 Hendry, K. and Cragg-Hine, D. (2003). Ecology of the Atlantic salmon, Salmo salar: Conserving natura 2000 rivers, ecology series No. 7. Peterborough: English Nature 26 | P a g e
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Hendry, K., Cragg-Hine, D., O’Grady, M., Sambrook, H. and Stephen, A. (2003). Management of habitat for rehabilitation and enhancement of salmonid stocks. Fisheries Research. 62(2): 171-192 Jonsson, B. and Jonsson, N. (2011). Ecology of Atlantic salmon and brown trout: Habitat as a template for life histories. London: Springer Kemp, P., Sear, D., Collins, A., Naden, P. and Jones, I. (2011). The impacts of fine sediment on riverine fish. Hydrological processes. 25: 1800-1821 King, M. (2007). Fisheries biology, assessment and management (2nd ed.). Oxford: Blackwell Publishing Klemetsen, A., Amundsen, P.A., Dempson, J.B., Jonsson, B., Jonsson, N., O’Connell, M.F. and Mortensen, E. (2003). Atlantic salmon Salmo salar L., brown trout Salmo trutta L. and Arctic charr Salvelinus alpinus (L.): A review of aspects of their life histories. Ecology of freshwater fish. 12: 1-59 Marsh, T.J., Kirby, C., Muchan, K., Barker, L., Henderson, E. and Hannaford, J. (2016). The winter floods of 2015/2016 in the UK – a review. Wallingford: Centre for Ecology and Hydrology Mawle, G.W. and Peirson, G. (2009). Economic evaluation of inland fisheries. Bristol: Environment Agency. Nislow, K.H. and Armstrong, J.D. (2012). Towards a life-history-based management framework for the effects of flow on juvenile salmonids in streams and rivers. Fisheries management and ecology. 19: 451-463 Pérez-Domínguez, R., Maci, S., Courrat, A., Lepage, M., Borja, A., Uriarte, A., Neto, J.M., Cabral,H., St.Raykov, V., Franco, A., Alvarez, M.C. and Elliott, M. (2012). Current developments on fish-based indices to assess ecological-quality status of estuaries and lagoons. Ecological Indicators. 23: 34-45 Pettine, M., Ruhhiero, A., Fazi, S., Buffagni, A., Anderson, J.M., Roncak, P. and Friberg, N. (2005). Organic pollution in rivers. In A.G. Solimini, A.C. Cardoso and A. Heiskanen (Ed.), Indicators and methods for the ecological status assessment under the Water Framework Directive: Linkages between chemical and biological quality of surface waters (pp. 99-116). Luxemburg: European Commission Directorate-General Joint Research Centre; Institute for Environment and Sustainability Roni, P., Hanson, K. and Beechie, T. (2008). Global review of the physical and biological effectiveness of stream habitat rehabilitation techniques. North American journal of fisheries management. 28(3): 856-890 Skinner, A., Young, M. and Hastie, L. (2003). Ecology of the freshwater pearl mussel, Margaritifera margaritafera: Conserving natura 2000 rivers, ecology series No. 7. Peterborough: English Nature Thorstad, E.B., Whoriskey, F., Rikardsen, A.H. and Aarestrup, K. (2011). Aquatic nomads: The life and migrations of the Atlantic salmon. In Ø. Aas, S. Einum, A. Klemetsen and J. Skurdal (Eds.), Atlantic salmon ecology (pp. 1-32). Oxford: Blackwell Publishing Ltd
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8. Appendix Torridge Catchment Salmon Classification Map
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Torridge Catchment Trout Classification Map
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Torridge Catchment Salmon Conservation Strategy Map
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Torridge Catchment Trout Conservation Strategy Map
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