Consultation Draft TAY DISTRICT FISHERIES MANAGEMENT PLAN. Prepared by the Tay District Salmon Fisheries Board on behalf of the Tay Foundation

Transcription

1 Consultation Draft TAY DISTRICT FISHERIES MANAGEMENT PLAN Prepared by the Tay District Salmon Fisheries Board on behalf of the Tay Foundation March 2009

2 Contents 1. Introduction 2 2. The Tay district 4 3. Fish and fisheries in the Tay district Factors affecting fish stocks and catches Actions required to protect and improve fish stocks Monitoring of fish stocks Developing the fisheries Delivering improvements References Glossary of acronyms Consultation 76

3 1. Introduction This plan sets out the priority activities which have been identified for managing freshwater fish populations within the Tay fishery district and for the development of freshwater fisheries. The plan relates to all fish species within the district, although it does naturally concentrate most on those species which have a value in terms of fishing. Fisheries management in the Tay district is delivered by several different organisations. The main organisation is the Tay District Salmon Fisheries Board (TDSFB) which has had a statutory remit to protect and improve salmon and sea trout fisheries since the 1860s. It is the only organisation which currently employs any staff and is principally funded by levies on salmon fishing proprietors. Three charitable organisations also exist, namely the Tay Foundation, the Tay Ghillies Association and the River Earn Improvement Association. These organisations raise funds or receive donations which are spent on fisheries management and educational projects on the river. The financial turnover of these trusts is relatively low compared to some on other rivers. All three work closely with TDSFB. There are also four Protection Orders (Tay, Earn, Tummel-Garry and part of upper Spey) within the district which requires four liaison committees. The Tay Liaison Committee is particularly active and in addition to managing the PO and it has to some extent adopted a role in freshwater fisheries management. Fishery proprietors and their staff and angling clubs are also heavily involved in various aspects of management. While not directly involved in fisheries management a number of statutory bodies have key indirect roles. Scottish Natural Heritage is particularly important as the Tay and its tributaries (but not including the Earn and the Eden) have been designated an EU Special Area of Conservation for Atlantic Salmon, the three species of lampreys and otters and the Firth of Tay has been designated an SAC for common seals. Scottish Natural Heritage is primarily responsible for safeguarding the SACs but there is an onus on competent authorities, which includes the TDSFB to uphold the objectives of the SACs which is to maintain a favourable conservation status of the designated species. The Scottish Environment Protection Agency will also play an increasing role because of its traditional role in maintaining water quality and increasingly by implementing the provisions of the EU Water Framework Directive. This has given SEPA new powers to regulate abstraction, engineering and other activities and has placed a requirement on SEPA to monitor fish populations. As the objectives of an SAC take precedence over the WFD, protection of salmon and its habitat must become one of SEPA s key objectives. The Scottish Government, and in particular Fisheries Research Services, whose main Freshwater Laboratory is based in Pitlochry with an outstation at Almondbank, has clearly also a vital role to play. Another key player in the district is Scottish & 2

4 Southern Energy plc whose many hydro installations give rise to numerous fisheries issues which are managed by dedicated fisheries and environmental staff. In identifying priorities this plan seeks to find a common purpose between the respective interests and to help take freshwater fisheries management forward in the coming years. 3

5 2. The Tay district 2.1 Introduction The River Tay district is the largest fishery district in Scotland. It is comprised of the entire catchment of the River Tay and all its tributaries, the rivers Earn and Eden and the sea coast between Fifeness and the Red Head at Arbroath. Figure 2.1: The main rivers and lochs in the Tay district 2.2 Geology The Tay District covers a wide range of geological types, perhaps as diverse as any single catchment in Scotland. The dominant geological feature is the Highland Boundary Fault (HBF) which dissects the district in two. To the north of the HBF are mainly pre-cambrian metamorphic rocks. Those in the area north of the River Lyon and to the west of the River Tilt, are mainly ancient rocks of the Moine Supergroup, the dominant rock in the northern highlands of Scotland. To the south and east of these are a suite of younger metasediments of the Dalradian Supergroup. The Dalradian rocks are less strongly metamorphic, more mineralogically varied and less acidic. In general the Dalradian rocks in Tayside seem to be fairly neutral and even slightly basic in terms of ph. They even include metamorphosed limestone. Granite intrusions are relatively scarce in the Tay catchment, largely confined to the Tummel catchment west of Loch Rannoch. Other smaller intrusions occur in the upper catchments of the River Tilt and the River Isla. 4

6 Immediately to the south of the HBF the catchment is underlain by Devonian old red sandstones, although in practice these frequently comprise mudstone and conglomerates. They give rise to richer streams than either the Dalradian or Moine rocks to the north. The Sidlaw / Ochill complex which borders either side of the Firth of Tay are formed of extrusive lavas which are contemporaneous with the Devonian sandstones. To the south, the catchment of the River Eden is again mainly underlain by Devonian rocks but the succession eventually progresses into Carboniferous lava (Lomond Hills) and mountain limestone. Coal measures are encountered only a short distance beyond the boundary of the Tay district. Figure 2.2: Main rocks types, Tay district 2.3 Topography The topography of the Tay catchment is strongly influenced by the underlying geology. At the most basic level, to the north west of the Highland Boundary Fault the country is upland and to the south east, lowland. 5

7 The uplands are mainly comprised of hills ranging from 750m to 1250m dissected by steep sided U shaped glaciated valleys through which the main tributaries flow. The smaller tributaries which drain the higher mountain plateaux, generally enter the larger glens as hanging valleys, steep cascades down to the valley floors. The glens of Tayside are particularly steep sided as they have been scoured lower than the other large rivers of Scotland. For example, at Kenmore the Tay has an altitude of approximately 100m while at an equivalent distance upstream the Spey and Dee are at approximately 200m. The Dochart at Crianlarich is at an altitude of approximately 150m, while at an equivalent distance the Tweed is at 170m, the Spey 240m and the Dee 350m. Deep ribbon lakes such as Loch Tay and Loch Rannoch have been scoured out by the action of ice in a number of these valleys. To the south of the HBF the country is lower and more gently rolling, an area of deep soils derived from glacial tills, or especially along the Tay valley, glacial outwash. This area is crossed by two ranges of modest hills, the Sidlaws which runs from the northeastern end of Strathearn, to the north of Dundee and into Angus and the Ochills which form the southern boundary of Strathearn and merge into the spine of northern Fife. These two ranges are the remnants of an ancient anticline which collapsed to form a graben (rift valley) through which the River Earn and the Tay s long estuary, the Firth of Tay, flows. In its final reaches the lower Tay is confined in a shallow gorge as it breaks through the Sidlaw Hills chain at Perth. At Perth the river then becomes tidal and broadens out on to the floor of the graben, or the Carse of Gowrie as it is known, a wide low plain which stretches approximately 20 miles to Dundee. Figure 2.3: Topography of the main sub catchments (Coastal catchments are excluded as information was unavailable for these) 6

8 Figure 2.4: Superficial deposits, Tay District 2.4 Climate The climate of the Tay catchment is dominated by the prevailing westerly airflow from the Atlantic Ocean and its interaction with the catchment s relief. This has created a climatic gradation between the higher western part of the catchment and lower eastern areas. The west is much wetter, on average cooler and receives less sunshine than eastern third of the catchment, although the immediate coastal fringe can be cooled in summer by proximity to the North Sea. Rainfall varies from over 1500mm per annum in the west to under 700mm in the eastern lowlands. 2.5 Hydrology The physical and climatic diversity of the Tay catchment is reflected in the hydrology of its tributaries. The areas of high rainfall and high relief are characterised by flashy streams which rise and fall rapidly in response to rainfall. During the winter and the spring flows from the highest areas can be regulated by snowfall and snow melt, but the importance of this effect has reduced in recent years due to the trend towards milder winters. By the time the higher tributary flows reach the main stem of the Tay the flashiness is naturally modulated by the buffering effect of large lochs like Loch Tay, Loch Ericht and Loch Rannoch. The narrow steep sided glens of Tayside made it an attractive area for hydro-electric exploitation and from the 1930s to the 1960s an extensive network of reservoirs, abstractions and cross-catchment transfers was created in the western half of the Tay district. This exacerbated the natural buffering effects of lochs and created highly regulated river systems in both the Tay and the Earn. 7

9 Figure 2.5: Schematic representation of hydro-electric regulation in the Tay district as established by the North of Scotland Hydro Electric Board. Figure 2.6: Examples of annual hydrographs for the rivers Dochart, Ericht and Eden. The Ericht and especially the Dochart have more spikey hydrographs than the Eden and the Dochart had many more significant rises than the Eden, illustrating the fact that the Dochart catchment, rising near to the west coast, receives more rainfall events than Fife (Data courtesy of SEPA and 8

10 Figure 2.7: Examples of annual hydrographs above and below Loch Tay. The flow entering Loch Tay at Killin is much more variable than the flow leaving at Kenmore. The effect of Loch Tay is to reduce the relative amplitude of flow peaks and to prolong spates. (Data courtesy of SEPA and Figure 2.8: Examples of annual hydrographs above and below Pitlochry Dam. The flow on River Tummel has been modified by hydro electric exploitation. There is now a guaranteed minimum flow of 18 cumecs, although drought flows would have been much less historically. The Garry flow is now much more spikey than the Tummel. (Data courtesy of SEPA and The average flow in each of the major tributaries of the River Tay is shown in Figure 2.9. A major feature is how great flows in the main stem of the Tay are compared to the various tributaries. The Tay has the highest flow of any river in Britain. By the time the River Earn enters the estuary the average flow is approximately 200 cumecs. 9

11 Figure 2.9: Mean annual flows at SEPA gauging stations on the major tributaries in the Tay District. Units are cumecs. (Data from National River Flow Archive) The Tay estuary, the Firth of Tay, is a large estuary, extending over 20 miles long and over two miles wide at its widest point. Saline intrusions penetrate almost as far upstream as the confluence of the River Earn. The estuary is characterised at low tide with extensive areas of sandflats and is obviously an area of powerful tidal currents. 2.6 Land use Land use within the Tay district is strongly dependent on factors like geology, topography, soil and climate. In the lowlands of Perthshire, Angus and northern Fife, i.e. the area to the south and east of the Highland Boundary Fault, the main land use is arable or mixed farming. Crops like barley, oilseed rape, wheat, potatoes, occasionally oats or vegetables predominate. There is also a significant amount of soft fruit, especially raspberries and strawberries. In some localities grass may be included in the rotation, and beef cattle and to some extent sheep are also significant. This is especially true in the steeper areas such as the Sidlaw Hills. There is however very little dairy farming in the district. North of the HBF, in the flat floor of the Tay valley itself, a sliver of mixed farming penetrates deep into the upland area, practically as far upstream as Loch Tay. But in most of the river valleys improved grassland is the predominant land use on the flood plains and lower slopes and both beef cattle and sheep are produced. At about the 300m contour improved grassland generally gives way to unimproved grassland which is predominantly grazed by sheep. On the higher slopes unimproved grassland eventually grades through into open moorland which is the most extensive land use 10

12 in upland Tayside. In the north and east of the highland area this is generally heather rich moorland, but in the far west grass tends to dominate as opposed to heather, on account of wetter climate and in some instances heavier grazing pressure. The moorland areas are to a lesser or greater extent grazed by sheep but deer stalking is a common upland land use across the region. In the drier eastern half of the region many of the moors are managed for grouse shooting. Pheasant shooting is also widely practiced in both the upland valleys and in the lowlands. There is a significant amount of woodland in the Tay District, but mainly in the upland areas. For the most part, larger forestry plantations are located in the intermediate altitude moorland areas along the middle and upper sections of the main stem of the River Tay or in the upper Tummel catchment. There are few woodlands in the higher interior moorlands. Thus forestry tends to be concentrated on the Dalradian as opposed to the Moine rocks, though there are exceptions. There are of course also areas of forestry throughout the lowland area which is pretty much studded with small woods. The Tay district is by and large a rural catchment. There are a few urban centres, notably the cities of Dundee and Perth. Urbanisation is therefore largely restricted to the coastal / lowland area. Along the coastal strip are a number of streams and rivers which discharge directly into the sea, such as the River Eden or the Eliot Burn or into the lower Firth of Tay, such as the Dighty Water. The watercourses of the lowland area are in general very different in character to those of the uplands. Most of the smaller tributaries have been greatly modified in the past and are generally channelised. Only some of the larger lowland watercourses, such as the rivers Earn and Isla, are not. These rivers mainly drain the upland part of the district but on the lower straths are characterised by gravel beds, steep sandy / silty banks and meandering. Like the lower Tay tributaries these streams all drain lowland areas and have been subject to considerable modification through channelisation and land drainage activities. Figure 2.10: Main land-uses, Tay District 11

13 2.7 Water Quality The level of water quality throughout Tayside is generally high with respect to normal indicators of pollution. According to SEPA s water quality classification in 2006 most of the rivers in highland Perthshire were either A1 (excellent) or A2 (good). A significant proportion of streams in the lowlands were classified as B (moderate), but only the upper Dean Water below Forfar Loch, the lower Dighty Water near Dundee and part of the lower Eden below Cupar were classified as C (poor). Athough the Tay is not grossly polluted, water chemistry does vary according to geology, land use etc. There is a gradation in chemistry between the softest water streams in the north west (granite and Moine rocks) and the hardest water streams in the south east (Devonian and Carboniferous rocks). A simple index of ion concentration is electrical conductivity. Data collected by the TDSFB are shown in Figure Figure 2.11: Electrical conductivity of streams in the Tay district sampled by TDSFB 12

14 3. Fish and fisheries in the Tay district For Scotland, the Tay district has relatively diverse fish fauna. The following species are thought to be native to the area: salmon, brown and sea trout, allis shad, arctic char, eel, flounder, brook, river and sea lamprey, perch?, three spined stickleback, stoneloach, sparling and twaite shad. Species which have been introduced into the district include: common bream, common carp, chub, crucian carp, dace, grass carp, grayling, ide, minnows, pike, roach, rudd, tench, rainbow trout, brook trout and vendace. 3.1 Salmon (Salmo salar) Salmon are the most economically important of the exploited species of fish in the Tay district. They occur in practically all watercourses large enough to accommodate them which have access to the sea. These are mainly the larger mainstem tributaries because salmon access has always been limited in the upland part of the Tay catchment because the smaller side valley tributaries are generally too steep. The distribution was slightly different in the past. In the late nineteenth and early twentieth centuries easing of waterfalls and fish pass construction apparently improved access to the River Tilt, upper Tummel, the upper Garry and other tributaries. Following hydro exploitation salmon were denied access to the upper Garry and the headwaters of the Lyon. New access was intended to be created in the River Lochay and the Abhainn Duibhe. Easing work on waterfalls was also conducted on the rivers Almond and Lyon, but the most spectacular success was the easing of Craighall Linn on the Ericht circa 1960, funded by the Hydro Board. 13

15 Figure 3.1: Modern distribution of salmon in the Tay district. Figure 3.2: Probable historical distribution of salmon in the Tay district based on presence of natural obstructions to migration. 14

16 The reported salmon catch has averaged approximately 10,000 in recent years, 99% of which are caught by angling. Salmon angling takes place throughout the length of the mainstem of the Tay, its major tributaries and the rivers Earn and Eden. Annual reported rod catches increased from the 1950s to the 1970s but since the mid 1990s the average catch has dropped from the peak years (Fig. 3.3). However, catches in the spring months show a decline since the 1970s. The bulk of the annual catch since the 1960s has comprised summer and especially autumn catches. Autumn catches have increased markedly since the 1950s. Significant net fisheries were removed from the Tay estuary in the 1990s which has helped offset the real decline in the pre-fishery abundance of salmon returning to the coast during the summer. Salmon which always returned after the end of the netting season (20 August) will not have been affected. In 2003 it was estimated that approximately 35,000 salmon angler-days were made in the Tay district per annum. Of these about 15,000 were by anglers who resided outwith Scotland, mainly in England. As these especially would require local accommodation etc, it is estimated salmon angling on the Tay generates some millions of pounds for the local economy. Figure 3.3: Monthly angling catches of salmon, Tay district, October September August July June May April March February January Trout (Salmo trutta) Brown trout are the most widely distributed fish in the Tay district, occurring in all subcatchments and in many of the steep tributaries which are inaccessible to salmon. Sea trout are a form of the same species but their potential distribution is of similar to that of salmon, although some obstructions are more easily passed by sea trout than salmon (e.g. the Findhu Burn). Even in habitat which is otherwise accessible, brown trout are the dominant form in the upland part of the Tay catchment, but sea trout have traditionally been most relatively numerous in the 15

17 River Earn. Some sea trout also run the Eden, the Almond and Isla to a lesser extent up the main stem Tay. Both brown and sea trout are exploited by anglers. Formerly there was a significant sea trout net fishery, but with the exception of a small scale fishery on the Earn, these have closed. The most popular area for sea trout angling is the River Earn where anglers specifically fish for them in the summer, including night time fishing. On the Tay the majority of sea trout are caught as a by-catch by salmon anglers, although in the lower reaches between Perth and Stanley some anglers do specifically fish for sea trout on summer evenings. Sea trout abundance and catches have declined markedly, and continue to decline, in the Tay and neighbouring districts since a period of very high abundance in the 1960s. As with salmon, marine factors seem certain to be a major factor. Returns are now so poor than in 2009 the Tay District Salmon Fisheries Board has recommended a policy of total catch-andrelease for sea trout. Brown trout are widely fished for throughout the Tay district, more widely than any other species. Brown trout angling takes place throughout the Tay and its tributaries and in the numerous lochs throughout the district. However, numbers caught have not been established nor has its economic value. 3.3 Grayling (Thymallus thymallus) Grayling were apparently introduced to the Tay at Kenmore in the nineteenth century and have spread throughout the mainstem of the Tay, the Isla, the lower Tummel and the Earn. Grayling angling is popular in winter, especially on parts of the lower and middle Tay, the Isla, Earn and the Tummel. As they are generally released they are not exploited in the same way as salmon and trout have been. Little information is available on numbers caught, the value of the fishery and even less on grayling stock levels, but anecdotal evidence suggests that catches have declined in recent years. Figure 3.4: Grayling records in the Tay district 16

18 3.4 Pike (Esox lucius) Pike are widely distributed in many of the lochs in the Tay catchment (e.g. Loch Tay, Loch Tummel, Loch Rannoch, Loch Freuchie, Marlee). They are also found in some of the larger rivers such as the mainstem of the Tay where they are present in slow flowing pools and backwaters. It is not clear whether or not pike are indigenous to the area, although they were historically spread as a source of food, for example by monastic houses. Whatever their history they are now well established where they occur. Pike angling is also popular on a number of lochs within the Tay district. However, little information is available on numbers caught or the value of the fishery. Figure 3.5: Pike records Tay district 3.5 Eel (Anguilla Anguilla) Eels are widespread in those parts of the Tay district easily accessible to the sea. Their distribution has been reduced by the construction of hydro-electric dams. They are unable for example to ascend the fish pass at Pitlochry Dam which was designed for salmon. Any eels recorded upstream in recent decades are likely to have been residuals from before the dam was closed by virtue of the fact that eels are very long lived. They are uncommon in higher upland tributaries where salmon may be present. They are most common in lowland areas. There has been very little directed fishing for eels in the Tay district, most eels are caught accidentally if bait is used for other species. The abundance of eels has declined markedly in recent years as a result of a national decline in elver recruitment. As a consequence the Scottish Government introduced a complete prohibition on fishing for or taking eels on 26 January

19 Figure 3.6: Eel records from the Tay district 3.6 Arctic char (Salvelinus alpinus) Arctic char are found in a number of the deeper lochs in the Tay catchment such as Loch Tay, Loch Rannoch, Loch Earn and Loch Loch. They are an important native species in conservation terms. Of particular interest is the fact that in lochs like Rannoch there are different forms, pelagic and benthic. Currently there is only a limited amount of angling for char and there is little information on catches or its economic importance. Figure 3.7: Arctic char records from the Tay district 18

20 3.7 Flounder (Platichthys flesus) Flounders are commonly found in the estuary of the Tay and in the lower reaches of the Tay, Earn, Eden and Dighty Water. Electrofishing at low tide below the Friarton Bridge revealed large numbers of juvenile flounder. Occasional specimens have been found further upstream, notably in Glenfarg reservoir where they were pumped from an abstraction point on the lower Earn. Little is known about the status of the population. They are caught by anglers in tidal reaches, but probably mainly as a bycatch. Figure 3.8: Flounder records, Tay district 3.8 Lamprey The three species of lamprey (book, river and sea) all occur within the district and have a wide distribution. They are not fished for in any way but have a high conservation value and are included in the Tay SAC species list. 3.9 Perch (Perca fluviatilis) Perch are widely distributed in the Tay district and mainly found in stillwaters or slower flowing rivers. Some lochs, like Loch Tummel, have large populations. Some angling for perch does take place, but there is little information on catches or any economic value. 19

21 Figure 3.9: Perch records, Tay district 3.10 Three spined stickleback (Gasterosteus aculeatus) Sticklebacks are widely found throughout the Tay district. The map of records is likely to seriously underestimate their distribution. They are not fished for. Figure 3.10: Records of three spined sticklebacks, Tay district 20

22 3.11 Stoneloach (Barbatula barbatulas) Stoneloach are widely found throughout the Tay district. They are found in both lowland tributaries and intermediate upland tributaries. However, they do not seem to occur in higher altitude oligotrophic tributaries. They are not fished for. Figure 3.11: Stoneloach records, Tay district 3.12 Sparling (Osmerus eperlanus) There is a population of sparling (smelt) in the Firth of Tay which formerly supported a commercial fishery. But as this fishery has not operated for some years the current status of the stock is not known. However, the Tay Salmon Fisheries Company in conjunction with Fife Council are planning to commence an investigation into the size of the population, presumably with a view to resuming a fishery Minnow (Phoxinus phoxinus) Although not native, the minnow has become one of the most widespread fish species in the Tay district. They are found from lowland tributaries to the most oligotrophic upland areas including the upper Lyon and the Ba. They are not fished for but minnows have in the past been sought for as bait for other fish species, namely trout and pike, which may have been a factor in their spread. 21

23 Figure 3.12: Minnow records, Tay district 3.14 Roach (Rutilus rutilus) Next to the minnow roach are the most widely distributed cyprinid species within the Tay district. Roach are alleged to have been introduced to the River Tay during the Second World War and spread throughout the Tay, into the Isla, Earn and up into the Lunan system. A particularly large population existed in the Perth Harbour area and that was a popular area for coarse fishermen. However, roach have more recently become rare in the Tay but a large population has developed in Loch Tay. It is not known whether those roach colonised from the River Tay or from a separate introduction. Roach have been introduced into a number of smaller stillwaters for angling, e.g. Dunmore Loch at Pitlochry or Kingennie Fishery, Broughty Ferry. 22

24 Figure 3.13: Roach records, Tay district 3.15 Other cyprinids In addition to minnow and roach the following cyprinids are known to occur in the Tay district: common bream, common carp, chub, crucian carp, dace, ide, rudd, tench and grass carp. These have been stocked into small stillwaters such as Dunmore Loch, Laird s Loch and Kingennie fishery but as yet have not escaped into the wider catchment, as far as is known. It is thought that coarse fishing may be a growing sector of angling locally but no data on catches or the value of this fishery have been obtained. Figure 3.14: Distribution of bream, common carp, chub, crucian carp, dace, ide, grass carp, rudd and tench in the Tay district 23

25 3.15 Rainbow trout (Oncorhynchus mykiss) Rainbow trout are not known to reproduce successfully in the Tay district but they are stocked regularly on a put-and-take basis in a number of fisheries across the district. These are mainly in large ponds or small lochs. Escaped rainbow trout have also occurred from time to time in the vicinity of some of the rainbow trout farms in the district. Figure 3.15: Locations of put-and-take fisheries stocked with rainbow trout (red) and areas where escaped rainbow trout are commonly found (yellow) 3.16 Vendace (Coregonus albula) A small number of Vendace were introduced to Loch Earn some years ago. A very small population may be present. 24

26 4. Factors affecting fish stocks and catches 4.1 Marine mortality Following a peak in the 1960s and 70s, there has been a progressive decrease in the survival of salmon in the sea and an associated decline in growth rates and condition. This has affected all of the British Isles and has been most marked since Recent smolt to adult survival rates (5 10%) may be less than 25% of peak levels (perhaps > 40%). Large scale hydrobiological changes in the north Atlantic, which may be driven by climate change, are now generally thought responsible. However, there is concern that some pelagic or shellfish fisheries could have a compounding impact by removing food and through salmon bycatch. Changes in marine mortality appear to have had a differential effect on different sub-populations of salmon. Spring salmon, in particular the very early running large 3SW fish, appear to have been very badly affected, whereas late running grilse populations which return in the autumn and may migrate to a different area of the ocean have been less affected and indeed are still at a much higher level than they were from the 1920s to the 1950s. Buyouts of the Tay s estuarine net and coble fisheries in the 1990s and the gradual cessation of other coastal and high seas fisheries has helped offset the impact of increased marine mortality, especially on those fish which enter freshwater during what was the netting season, i.e. summer. This has most notably benefited the River Ericht. As most commercial fisheries did not operate effectively in early spring or after 20 August the long term decline in spring fish and more recent decline in autumn fish reflects the full impact of reduced marine survival. A similar problem has almost certainly affected sea trout over a similar period and their abundance has reduced markedly since the 1960s. This is likely to have been driven by both climatic and industrial fishing pressures, such as the ongoing Danish sandeel fishery and the historic sprat fishery. The resulting reduction in egg deposition by sea trout may have had an effect on brown trout populations. 4.2 Natural obstructions to fish migration The great majority of upland tributaries of the Tay and Earn which are under 10 metres wide are not accessible to adult salmon, sea trout or river brown trout for any significant distance because of impassable waterfalls. Probably in no other large Scottish river is such a high proportion of the catchment naturally inaccessible to migrating fish. The total inaccessible area is equivalent in size to the North Esk and puts the Tay at an immediate disadvantage as a salmon and sea trout river. Most salmon production has to take place in the mainstem of the Tay or in large tributaries. However, while salmon can cope in such environments, trout are greatly 25

27 disadvantaged as trout spawning and juvenile habitat is typically found in streams under two or three metres wide. Trout recruitment is therefore likely to be greatly restricted in the upland part of the catchment. Many of the inaccessible smaller tributaries are populated by isolated relic brown trout populations above the waterfalls from which some downstream leakage of juveniles will occur, but such will be limited by low fecundity. Some waterfalls are also partial barriers to migration according to flows and water temperature and can be passed only under suitable conditions. Natural barriers not only limit the distribution of migratory species but also more recently introduced species. Figure 4.1: Absolute barriers to upstream fish migration. Red - areas to which access to migratory fish is currently blocked by natural barriers. Yellow areas to which access is currently blocked by man-made barrier / abstraction. Orange areas where access is blocked by natural barriers, but where man-made barriers would still apply in the absence of natural barriers. Blue areas formerly blocked by natural barriers which were opened by the North of Scotland Hydro Electric Board. 4.3 Water chemistry / nutrients Water chemistry is a major control on the production of juvenile salmonids in the Tay catchment, especially in upland areas. Even where physical habitats are good, salmonid production can be low where chemical fertility is poor. Some of the highest standing stocks of juvenile salmon are in fact found in lowland streams draining enriched arable land in spite of other problems associated with agriculture. A readily measured surrogate for ionic concentration in river water is electrical conductivity. There is a broad gradient in conductivity from west to east across the 26

28 Tay catchment (Fig. 4.2). The lowest conductivities are found on the granitic and Moine rocks of Rannoch and Black Mount. The second lowest are found in the River Lyon downstream of hydro-electric reservoirs. The highest conductivities are found in the eastern lowlands but even the north-eastern uplands have higher conductivities than the west. This explains why the River Ericht is the most productive for salmon of all the Tay s upland tributaries. Even at an altitude of 300m most salmon smolt after only two years while at similar or even lower altitudes in the Lyon, Tilt or Almond most smolt after 3 years. Figure 4.2: Electrical conductivity of areas of the Tay district sampled by TDSFB Much of the variation in stream fertility will be related to geology, but anthropogenic effects are also important. These can both add to or reduce nutrient levels. Nutrient inputs are widely assumed to be undesirable and indeed they may be when excessive. However, it is increasingly being appreciated that they can have a positive effect on fisheries in some situations. For example, the abundance of juvenile salmon in the Cononish / Fillan Water is low upstream of the village of Tyndrum but markedly higher below it. This has been found to coincide with a large increase in the abundance of Chironomid (midge) larvae which probably have responded to enrichment from Tyndrum sewage treatment works and agricultural sources. It is recognised that nutrient enhancement to help fisheries is a relatively novel concept and may be controversial, especially given a dominant culture in SEPA and other organisations towards reducing man-made inputs and preventing eutrophication. However, there is growing appreciation that upland regions of Scotland may in fact have suffered from decreasing fertility as a result of human activity, or cultural oligotrophication. 27

29 There are several possible causes of cultural oligotrophication in the Tay catchment Upland acidification While Tayside has never been recognised as an area suffering from acute acidification from atmospheric pollution, there is evidence that there has been some impact. Loch bed sediment core analysis has shown that since the industrial revolution there has been a decrease in ph in Loch Laidon on Rannoch Moor and more widely in the Cairngorms (Flower et al. 1988; Jones et al. 1993) Damming and flow regulation The headwaters of the River Lyon were dammed in the 1950s and the river is now maintained by a compensation flow drawn off from the lower levels of storage reservoirs. Under dry weather conditions this flow has a poorer chemistry (lower ph, conductivity, alkalinity, calcium and higher iron, manganese, zinc and aluminium) than tributaries flowing into the reservoir. This may mean that the chemistry of the River Lyon is poorer than it would have been naturally. Similar impacts may occur downstream of other reservoirs. The increased dry weather flows which occur on the Tummel downstream of Pitlochry Dam and the Tay below Loch Tay as a result of hydro regulation will presumably increase the proportion of relatively nutrient poor western water in the main stem of the Tay in dry summers Land use impacts Certain types of land use can reduce nutrient leaching in the uplands. However, this is still an area which has not been well researched but the debate is developing. Issues which need to be considered include the long history of grazing without nutrient replacement, muirburning and the acidifying effects of heather and forestry. 4.4 Water abstraction Water abstraction is a major issue in Tayside. Some extreme examples exist, even of total abstraction of some significant rivers. Some of the most damaging abstractions have been in existence for some time and sanctioned by statute. However, the EU Water Framework Directive has recently given SEPA the power to require retrospective improvements, should they choose to use it. This is therefore a particularly relevant time to consider abstraction. Water is abstracted for four main purposes; hydropower, irrigation, water supply and fish farming. 28

30 4.4.1 Hydro-power The Tay catchment has the most extensive hydro-electric system in Scotland. Numerous tributaries are abstracted to feed reservoirs and power stations. In some instances a hands-off or compensation flow has to be maintained but in many cases complete abstraction occurs except when very high flows result in spillage at intake weirs. Most of the total abstractions are located on relatively small streams, but some occur on significant rivers, the most notable being the River Garry. Abstraction mitigation provisions are more common in the southern half of the district (Earn to Lyon) which was planned after the Second World War than in the northern half (Tummel Garry) half which was planned during the Second World War. Figure 4.3: Hydro electric abstraction points in the Tay District. Red SSE schemes which are totally abstracted, blue SSE schemes which are totally abstracted except during periods of low flow, green SSE schemes where a compensation or hands-off flow is stipulated, yellow smaller private schemes which pre-date SEPA s Controlled Activities Regulations. Most of the abstracted streams are steep and inaccessible to adult salmonids, so in most instances only resident brown trout populations are affected. Given the number of such abstractions the amount of steep stream habitat in Tayside may have been significantly reduced. The most significant effects on migratory fish are on the Garry, as mentioned earlier, and the River Lochay where there is still a flow but significantly reduced in summer. 29

31 4.4.2 Agricultural irrigation Agricultural irrigation is a significant issue during dry summers in the eastern part of the Tay district where rainfall is relatively low and where demanding crops such as potatoes and soft fruit are widely grown. Some smaller streams can have the bulk of, or even all of their flow abstracted. A particular danger is when several abstractors remove water from the same stream at the same time. This is a particular threat to smaller lowland streams where brown and sea trout spawn. Since 2006 these abstractions have required a licence from SEPA. It is understood these are currently under review by SEPA with a view to producing some form of management plan Public water supplies Public water supplies are sourced from a number of locations in the catchment but because they are much fewer and the proportion of the flow abstracted is generally much less, the impacts of water supply abstractions are much less significant than hydropower or perhaps even irrigation Fish farms Two rainbow trout farms abstract water directly from the River Earn, one abstracts from the River Almond and one from the River Ericht. During periods of low flow some of these fish farms abstract the greater part of the flow. For example Westmill fish farm on the Ericht has a licence from SEPA to abstract 2 cumecs of water which may be more than the entire flow in a drought. The potential impact of these abstractions depends not only on the proportion of the flow abstracted but the distance between the point of abstraction and the return of the water. In some cases this extends to only a few hundred metres but in the case of Westmill it extends for 4 kilometres. The effects of these abstractions are to interfere with the upstream and downstream migration of adult salmon and smolts and to reduce juvenile salmon habitat in the abstracted area. At Westmill the abstraction reduces the dilution of the discharge of Blairgowrie sewage treatment works. Fishlegal (formerly known as the Anglers Conservation Association) have threatened legal action against Westmill to reduce the abstraction, which the operators admit could be done by partially recirculating the flow. However, under their recent acquired powers SEPA have promised a review of this abstraction in the 2008/09 financial year and the results are awaited. 4.5 Man-made obstructions Dams, weirs, road culverts and other constructions do partially or fully obstruct the passage of migratory fish from some parts of their natural range in the Tay district (Fig. 4.4). However, the extent of this problem is much less significant in the Tay District than on some other rivers which have a greater industrial history or a greater level of natural fish access (See Section 4.2). 30

32 Figure 4.4: Tributaries from which migratory fish have no access on account of artificial weirs contravening the Fish Passes and Screens Regulations (red) and limited access (green) Fish passes were provided at a number of hydro dams to allow salmon passage. In most instances these appear to work satisfactorily although some problems can occur. A particular issue at some installations is that migrations may be delayed because of the preferential attraction of flows from adjacent turbine tailrace discharges or delays because of low temperatures. At Pitlochry Dam small grilse can sometimes penetrate the trash screen below the tailrace and become trapped upstream of the screen. It has been found, however, that on lifting the screens trapped fish usually leave quickly followed by a sudden rise in counts in the fish pass. This management policy has been adopted for several years. 4.6 Predation Piscivorous birds Significant numbers of goosanders, red-breasted mergansers and cormorants use the River Tay and its tributaries and / or stillwaters within the district. Goosanders which are the most prevalent species on the rivers may have been absent from the UK prior to the 1870s but their numbers have expanded markedly due to factors like climate amelioration, reduced persecution and perhaps reduced abundance of pine martens which would raid the nests which are made in hollow trees (Leslie Hatton & Marquiss 2004). The loose Tay district goosander population amounts to approximately 200 birds but this can be temporarily augmented by birds on passage (e.g. migrant males which sometimes accumulate on the lower Tay during the salmon smolt run) and males from the southern UK are increasingly summering in the Eden estuary (Leslie Hatton & Marquiss 2004). Mergansers breed along the mainstem of the Tay and its large tributaries but unlike goosanders are 31

33 largely absent during winter. Cormorants are prevalent on stillwaters but some are always present on the lower Tay or slow flowing tributaries such as the Isla, but usually in much smaller numbers than sawbills. Larger numbers of cormorants are normally only seen on running water during hard winter weather. These birds eat a wide variety of fish species but juvenile salmon and trout dominate the diet of sawbills. While trout may be preferentially taken if available, juvenile salmon tend to dominate the areas most frequented by sawbills. Sawbills do take advantage of smolt migration bottlenecks, e.g. by congregating below the tailrace at Pitlochry Dam but the significance of concentrations of goosanders in the lower reaches of the Tay and Earn in winter is not known. It has been assumed that nonsalmonids (e.g. flounders and eels) may dominate the diet, but there is increasing appreciation that pre-smolting salmon accumulate in the lower reaches of rivers in winter. Cormorants prefer to take larger prey than sawbills and in stillwaters will even take fully grown stocked trout which result in a direct cost to the fisheries. In rivers they appear to prefer larger species such as brown trout and grayling as opposed to salmon. While in rivers overall bird predation may have a significant effect on salmon resident species like brown trout and grayling may in fact be most impacted Pike Pike, which are not indigenous to the catchment, are now widely found in throughout the Tay district. The introduction of pike will have fundamentally altered the fish population structures of those lochs in which they occur. Concerns over perceived pike predation on migrating salmon smolts and brown trout populations did in the past result in some local attempts at pike control. The benefits or otherwise of such actions remain a matter of controversy. However, an increasing number of anglers appreciate pike as a sport fish in their own right, and even if it were justified, pike control is likely to meet with vigorous opposition. In any event pike are so well established in most places for any form of control to be ineffectual Seals The Firth of Tay has one of the highest concentrations of seals in eastern Scotland and is an EU Special Area of Conservation for common seals. Seals haul out on the Abertay Sands between feeding forays in the North Sea where the seals mainly appear to forage on the sea bed for sandeels, flatfish and gadoids (trawler discards?). In 2006 the Sea Mammal Research Unit counted 1379 grey seals and 342 common seals. The national grey seal population continues to expand at 2.5% per year and may now exceed 130,000 but for unknown reasons common seals are declining and in the Tay have halved since The effect of seals on migrating salmonids in the Tay is unknown. While salmonids cannot be a major component of their diet, simple arithmetic suggests that even the occasional capture of a salmon or sea trout by each seal would amount to a very significant loss. 32

34 Figure 4.5: Common seals (foreground group) and grey seals (rear group) hauled out on a sandbank at Tentsmuir, May 2008 (photo courtesy of J. Apthorp). Occasionally, seals of both species penetrate the upper Tay estuary and even into freshwater proper on the Tay, Earn and Eden. This behaviour has increased since the 1990s and mainly occurs in autumn and winter when incoming salmon and descending kelts are most abundant. The significance of this predation on salmon and sea trout populations is not known, but there has been a marked impact on salmon angling in tidal angling beats of the Tay. Worst affected is the Perth town water. Formerly, salmon would accumulate there during dry autumns but this scarcely happens now Dolphins Perhaps as a result of the elimination of the Dundee sewage discharge from the Firth of Tay, bottlenose dolphins are increasingly seen around the mouth of the Tay where in summer they have been observed to catch salmon. There is no information on the scale of this predation but cetacean toothmarks are sometimes found on salmon caught in the Tay. These are often misidentified as seal damage Mink American mink are thought to be widespread in the Tay district. They can be significant predators of juvenile salmonids in small streams (Heggenes & Borgstrøm 1988). However, as the great majority of smaller streams in Tayside are inaccessible to migratory fish anyway, any impact they may have is probably greatest on brown trout which are reliant on smaller streams. Mink also have significant effects on wider biodiversity and other initiatives have been or may be launched to attempt to control mink. A major effort is being expended to eradicate mink from the Cairngorms National Park for the benefit of significant water vole populations and 33

35 there is a desire to extend this initiative further to prevent recolonisation from outside by involving local estates and other parties such as TDSFB. The Tay Western Catchment Project has also identified an important water vole population in Glen Lochay and has also recommended mink control. 4.7 Floods In recent decades rainfall and its intensity has increased in the western part of the Tay district. This, and sudden thaws of snow, appears to have increased the frequency of large winter floods. Intense local summer deluges have also become more common. Consequently there has been an increase in landslides and gully erosion which has increased sediment loads in some upland streams and rivers. Bank and bed erosion has also increased in tributaries and the main stem of the Tay. The short-term effects of such floods may be to increase redd damage and even washout of juvenile fish and invertebrates. However, in some areas increased gravel inputs may have increased salmonid spawning habitat but in areas already replete with gravel, habitats for older stages of fish could be lost as pools become filled with gravel and sediment. 4.8 Summer flows and juvenile salmon habitat As most of the smaller tributaries of the Tay are inaccessible to migratory fish, the great majority of salmon must be produced in larger tributaries or in the main stem of the Tay. Electrofishing surveys conducted by TDSFB have indicated that salmon fry are largely restricted to very shallow marginal riffle areas in the Tay which is a very small proportion of the channel width in the main stem. The abundance of such habitat is likely to vary under different flows which may mean that fry survival is affected by summer flows. Very high summer flows would be expected to be poor. Fry in these marginal areas may also be vulnerable to sudden drops in flow, which can sometimes be caused by hydro operations. 4.9 Egg deposition Owing to the recent decrease in the marine survival, weight and condition of salmon (section 4.1) and the compounding effect of fishing mortality, there must be an increasing likelihood that insufficient salmon (and sea trout) ova are deposited to maintain maximum smolt production. The extent to which parts of the Tay or its tributaries may be understocked by salmon has not been widely determined, because it is costly to do. However, most tributaries of the Tay system contain good densities of juvenile salmon which are comparable with other rivers in Scotland. Annual counts of salmon ascending Pitlochry Dam and the River Ericht appear remarkably consistent, which is indicative of a system regulated by density dependent factors. However, experimental stocking experiments by TDSFB have confirmed that the River Lochay and western Tummel catchment are seriously understocked, but those 34

36 problems are long standing and have been exacerbated by fish access problems. There is no information on juvenile numbers in deeper habitats in the main stem of the Tay which may be a less suitable for juvenile salmon and where any reduction in smolt production might be expected to occur first Overshading by riparian trees Dense shade cast by closely spaced trees like alder along narrow streams can reduce food for fish and suppress bankside and emergent grasses and waterweeds which provide valuable fish cover, especially in fertile lowland streams. Tree shading was relatively unimportant in the past but is now widespread (Fig. 4.7) and will continue to increase unless checked. At present the most affected streams are the Errochty Water, Lunan Water, Ordie Burn and tributaries in Strathearn. The Tay DSFB commenced thinning work on the Errochty Water in 2008 and this will continue in Figure 4.7: Areas of the Tay district which are accessible to salmon which are densely (red) and partially (yellow) shaded by riparian woodland 4.11 Riparian grazing There is increasing awareness nationally that riverine fish habitats can be impaired by overgrazing of the riparian zone. Grazing can remove the cover provided by marginal vegetation, accelerate bank erosion leading to wider, shallower and slower channels and increase sediment loads. However, there is as yet an almost complete absence of quantitative information on the effects of this on different stream types. In comparison with some other parts of the British Isles the effect of grazing on fish habitat is of lesser significance in the Tay district. Grazing does most damage in 35

37 relatively small streams which have easily erodible banks, gravel or sand beds and subject to high cattle or sheep densities, i.e. low gradient streams flowing through improved grassland. As much of the lowland part of the Tay district is arable this is generally not an issue. While there is a significant amount of riparian grazing in upland parts of the Tay district the coarser bed and bank materials provide a much greater resilience to grazing. Indeed in some stony tributaries some grazing induced erosion may actually be beneficial (section ). The effect of grazing is therefore variable and highly dependent on local factors. However, those stretches of river which are accessible to migratory salmonids and where grazing has significantly contributed to the erosion of soft banks are shown in Fig 4.6. Areas of particular impact include the lower mainstems of the Isla and the Earn and to a lesser extent the mainstem of the Dochart. These three areas share a common feature in that they have low gradients and are prone to flooding which has meant that stock grazing is the most appropriate landuse and fencing is considered impractical. Figure 4.6: Areas of those parts of the Tay district which are accessible to salmon where stock grazing has contributed to significant erosion of riverbanks (as yet excluding the River Eden and Dighty Water) 4.12 Floodplain encroachment by woodland In a number of areas there has been significant encroachment of woodland, both broadleaved and coniferous, along river margins and in the wider floodplain. Closely spaced trees affect the hydraulics of floodplains and can reduce overland conveyance during floods which in turn results in a concentration of flow in the river channel which can lead to enhanced erosion. In several locations increased destabilisation appears to be related to floodplain encroachment. 36

38 4.13. Ecological impacts on rivers regulated by reservoirs A recent study instigated by TDSFB showed the invertebrate community in the upper River Lyon has been radically altered by damming and flow regulation (Jackson et al. 2007). While there have been few other similar studies in Scotland, downstream impacts of reservoirs which release compensation or hydro generation flows are well appreciated in other countries and may occur elsewhere in the Tay district. Reported impacts include the following Changes to the flow regime Flow regulation generally means a reduction in flow variation, although this can take different forms. All dams in the Tay district will reduce the frequency of high flow events and reduce the size of peak flows. However, some like Pitlochry Dam, have actually increased the average daily flow and below other dams drought flows have been eliminated. The resulting changes to scour regimes have resulted in changes in substrate (further exacerbated by sediment starvation from upstream), algae growth and habitat suitability for invertebrates and fish. Fish migration patterns can also change. Although overall flow variation may be reduced, some hydro operations may result in an increased level of smaller scale variation which is particularly notable for its speed. This is particularly the case where demand-led power stations discharge directly into a river, for example Lubreoch power station (River Lyon), Lochay power station (River Lochay) and Gaur power station (River Gaur). While Pitlochry power station (River Tummel) and Dalchonzie power station (River Earn) are meant to dampen out fluctuations these also are not immune. The biological consequences of such disturbance on fish habitats and fish have not been assessed in the Tay district Thermal impacts Water discharged from dams may have an unnatural temperature regime, especially when water is drawn off from the base of a dam, as is commonly the case for hydropower. The temperature of the compensation flow in both the River Lyon and the Errochty Water is suppressed in spring / early summer but increased during winter. None of the other regulated tributaries have been monitored yet nor are the full biological consequences understood. However, temperature changes could have wide ranging effects, from impacts on primary and invertebrate production to direct impacts on fish growth, timing of migrations and timing of spawning Impacts on water chemistry Deep storage reservoirs can affect river water chemistry. For example, low nutrient flood water is stored up and released gradually. Nutrients can also be stripped from the water by biological activity within the reservoir. When anaerobic conditions exist in the deepest parts of the reservoir (the hypolimnium ) minerals can be chemically reduced leading to increased concentrations of metal ions such as iron and 37

39 manganese. As a practical example, the flow emanating from the Loch Lyon reservoir was found to have a lower ph, alkalinity and dissolved calcium than inflowing tributaries but it was higher in less desirable iron, manganese, zinc and aluminium ions (also see Fig 4.2). During low flow periods even the nutrient status of the Tay itself may have been reduced because of the increased contribution of lower nutrient status water from the west. This may occur because the summer level of Loch Tay is likely to have been increased because of the gradual transfer of water from the Lyon and Orchy catchments through Lochay and Finlarig power stations. Furthermore, the minimum discharge now permissible in the Tummel (18 cumecs) is much higher than natural drought flows were and then enhanced flow is mainly composed of stored low nutrient water from the western Tummel, upper Garry and even upper Spey catchments. Similar effects could also occur on the River Earn Downstream fish passage at hydro intakes Downstream movements of fish are at risk from the many hydro-electric intakes in the Tay catchment (Fig. 4.8). Most of the intakes are situated in relatively small upland streams which are inaccessible to migratory salmonids, although there may still be small isolated populations of brown trout. Those high intakes which were installed by the NoSHEB were only fitted with trash screens and there are no precautions to prevent entrainment of small trout. However, high intakes on new private run-of-river schemes approved through SEPA s CAR process are generally being fitted with finer bar screens which, in theory at least, prevent trout larger than fry from being entrained. Figure 4.8: Hydro generating installations with smolt passage issues. Red salmon smolts present, green existing intakes where no smolts are present, yellow intakes in planning 38

40 However, there are ten hydro intakes at lower elevations at which migratory fish are present and have to be catered for. Six of these are operated by SSE and four are operated by other operators. The major issues at each are as follows: Gaur Dam Large fish are excluded from the turbine intake by a coarse vertical bar screen but smolts are not because the NoSHEB considered that medium head Francis turbine did not pose a significant risk to smolts, but this has not been tested using modern techniques. It is the understanding of TDSFB that the original turbine has since been replaced with a turbine with an extra runner. When the main turbine is not operating, a compensation flow is maintained in the river by a smaller compensation turbine. As its closely spaced runners would definitely kill smolts an agreement was made between SSE and TDSFB such that this turbine is not operated during the smolt migration period and the compensation flow is passed via the fish pass Dunalastair Dam Dunalastair Dam diverts the main flow of the River Tummel into an aqueduct which leads to Tummel Bridge power station. Smolts are deflected from the aqueduct back into the River Tummel by an array of one by half inch steel mesh screens. No problems are assumed, but the effectiveness has not been tested using modern methods Clunie Dam One by half-inch steel mesh smolt screens were originally fitted to the intake to the Francis turbines and smolts were meant to leave Loch Tummel via the adult salmon pass which was located nearby. However, in the 1980s Fisheries Research Services proved that the relative attraction of the much greater turbine flow meant that 70% of smolts failed to leave the loch. As mortality reduced to 30% when smolts were allowed to pass through the turbines the screens were removed. Numbers of adult salmon counted ascending the Clunie Dam fish pass then increased markedly over several years but these have stabilised suggesting the recovery may have reached its limits under prevailing marine survival rates Pitlochry Dam Salmon smolts descend through the adult salmon pass, or via the large Kaplan turbines, which have been assumed to be smolt-friendly. However, it is the understanding of TDSFB that recent trials at Torr Achilty, a similar dam on the River Conon, have shown that significant smolt mortality occurred when the station was running at a low generation load and the guide vanes almost closed. There must therefore be a concern that this may also occur at Pitochry. 39

41 Stronuich Dam Stronuich Dam on the River Lyon diverts water into a tunnel to feed Lochay Power Station (high head Francis turbine). One by half-inch steel mesh screens are used to exclude smolts and divert them towards the adult fish pass (Borland lift). There is no information on the guiding efficiency of these screens or whether significant numbers of smaller juvenile salmon or other species pass through Earn Weir Water is drawn off Loch Earn by means of a tunnel to supply Dalchonzie power station (low head Kaplan). As at Pitlochry, there are no smolt screens but the same low load concerns must also apply Stanley Mills Npower renewables operate a small Kaplan turbine (800 MW) in a lade by the River Tay at Stanley Mills. A flow of up to 14 cumecs is abstracted from the Tay and a large array of vertical bar screens (12 mm gaps) has been installed within the lade to deflect smolts into a bywash. The bywash takes the form of a pipe which is fixed to the bottom of the lade and terminates in an overhang, several metres above the level of the tailrace. The bywash water and smolts and any other fish exit the pipe in a rapid jet which is forced by several metres of head and crashes into the tailrace below. An appraisal of the screen s effectiveness was conducted when the station was commissioned but the TDSFB consider the approach taken may have been fundamentally flawed and major questions remained unanswered. Given the large number of smolts which could be put at risk by this facility further appraisal work is required Stormontfield Generator This is a small generator (100 kw, low head Francis turbine) operated by TLS Hydro Power Ltd and is situated on the Stormontfield Lade which abstracts water from the River Tay opposite Stanley Mill. A 10 mm vertical bar screen has been installed upstream of the powerhouse to deflect smolts into a bywash. The screens are of a less robust construction than those used at Stanley Mills and are in need of refurbishment. The effectiveness of this screen has not been fully tested but the dimensions of the screen are such that under certain conditions water velocities may be high enough to pin smolts to the screen. Indeed some dead smolts have been found on the screens under conditions when the screens have been partially clogged with debris Cromwellpark Generator At Cromwellpark, Almondbank, water is drawn off the River Almond into a lade to power a 100 kw low head Francis turbine, the same type as at Stormontfield. A vertical louver screen has been installed just upstream of the powerhouse to divert 40

42 smolts into a bywash. TDSFB have significant concerns regarding the effectiveness of this screen and the sufficiency of the bywash and are in negotiation with the operator to improve its performance Mill of Ruthven generator This is a small station on the River Isla. Smolts are screened from the intake by physical screens. As with all such systems there is always concern that maintenance is required to ensure safe smolt passage Smolt passage at fish farms Four fish farms abstract water from tributaries in the Tay district. In all instances screening has been provided to prevent smolts and other fish entering the fish farm. No problems have been reported at College Mill or Kindrochet fish farms. However, TDSFB has expressed concern at West Mill, Blairgowrie and negotiations with the operators are ongoing. The location of the bywash relative to the screened intake is such that during periods of lower flow migrating smolts may be delayed. Smolt screens at Drummond fish farm are also adequate but in the past some aspects of the management of these screens has been found to reduce their effectiveness Losses of smolts in stillwaters Smolts migrating from some of the most distant tributaries of the Tay district have to negotiate some large lochs; e.g. Loch Tay, Loch Rannoch, Loch Tummel and Loch Earn. There is some evidence from tagging studies on Loch Tay and on the Conon that smolts may suffer significant mortality when migrating through such water bodies. The are precedents for transporting smolts around large waterbodies but solutions may be costly in terms of capital and running costs and may have unintended biological consequences. A better understanding of the extent of this problem is required Sheep Dip The introduction of synthetic pyrethroid sheep dips in the 1990s created a very serious pollution threat. These dips are extremely toxic to freshwater invertebrates and very small discharges can devastate invertebrate communities for kilometres. At least two severe incidents have occurred on the River Earn and SEPA have expressed concerns regarding other tributaries. Fortunately the situation has improved. SP dips have been withdrawn from sale since SEPA have also prioritised monitoring in the most vulnerable areas and sheep dip inspections are now part of the conditions under cross compliance for single farm payments. Market and other forces are also reducing sheep numbers. However, should any of these conditions change and SP dips make a return, the threat will be real once again. 41

43 4.18 Diffuse pollution from agriculture Diffuse pollution from agriculture has been identified by SEPA as one of the most significant environmental impacts on the ecological status of waterbodies in the Tay district. The streams considered to be most at risk by SEPA are all in the lowlands (Fig. 4.9) where the main problems are run-off of excess nutrients and other agrichemicals from land, run-off from farm yards and steadings and run-off of sediments from bare fields. This is most acute where sloping fields are bare in winter following autumn ploughing or potato harvesting. Sediment release caused by poaching of the ground by livestock is also a local issue (section 4.10). Figure 4.9: Waterbodies in the Tay district identified by SEPA as being most impacted by diffuse pollution from agriculture. Diffuse pollution is not only generated in fields adjacent to major fish holding watercourses but from any part of the drainage system, including the smallest ditches and temporary rills which may form in fields following heavy rain. Control of diffuse pollution requires targeted action on critical hotspots throughout entire farms. Potential solutions include improved nutrient budgeting, installation of permanently vegetated buffer strips and other silt trapping features along critical pollutant pathways and changes to agricultural practice, for example the adoption of conservation tillage techniques. 42

44 Figure 4.10: Much of the diffuse pollution in the Tay district emanates from cultivated land surfaces in winter which may be some way from fish-holding watercourses. Stock management on farms can also be a significant issue. These sources of pollutants require solutions to be implemented throughout the farm and not just immediately adjacent to streams. The scale of the task required to defeat diffuse pollution is beyond any individual fishery management organisation and must be tackled through collaborative efforts with SEPA, Scottish Government, SAC and others. While the existence of diffuse pollution can be readily observed, its effect on fish, is in fact less well demonstrated in the Tay district. Some of the most abundant populations of juvenile salmon in the district, though not brown trout, are found in some of the most intensively farmed subcatchments in Strathmore Alien species A number of introduced species threaten fish populations and fisheries in the Tay district Gyrodactylus salaris This is a parasite which lives on the skin of juvenile salmon in freshwater and is native to rivers flowing into the Baltic. It has been spread to some rivers in western Norway where it causes very high rates of mortality in salmon which have no immunity to it. It is not present in the UK, but would be devastating to native salmon populations were it to arrive. It is probably the biggest single potential threat to Scottish salmon generally. Fortunately this parasite cannot survive in salt water and is only likely to arrive because of anthropogenic means. The prevention of the introduction of this parasite is a national and local priority Signal crayfish American signal crayfish have been found at a number of sites within the Tay district (Figure 4.11). They have become established in the upper River Earn centred in the vicinity of Drummond Trout Farm. They were also introduced into a pond in Strathardle but this and a nearby pond were poisoned with natural pyrethrum in 43

45 2006 in order to prevent colonisation of the River Ardle. Subsequently another population was found in ponds and a stream close to the Shee Water. They have also been found in the Rankielor Burn, a tributary of the Eden and in the Dighty Burn near Monifieth. Unconfirmed reports of signal crayfish have also been made in the lower Ericht and on the River Tay near both Dunkeld and Scone. Signal crayfish are a highly aggressive invasive species which can form very dense populations and can fundamentally affect the ecology of stillwaters and rivers. They are omnivorous and will eat fish, invertebrates, waterweed and detritus. Once established they are as yet extremely difficult to control let alone eradicate. Even from the source areas already established it is probably inevitable their numbers will expand markedly. It is only a matter of time. Figure 4.11: Locations of signal crayfish, Tay district Non-native fish species Since August 2008 introductions of all freshwater fish (other than salmon and sea trout) must be licensed by the Scottish Government. However, prior to that time there were wide-spread introductions of non-native fish species or transfers of native species from outside the district. These have most commonly included rainbow and brown trout and various coarse fish species. When done inappropriately such introductions can impact on native fish populations, even of the same species, and wider aspects of biodiversity. This is also one of the main potential routes for the introduction of fish diseases and parasites. Most of the local introductions of signal crayfish and Argulus foliaceus, for example, have either directly or indirectly resulted from introductions or culture of rainbow trout. 44

46 Many of the deliberate introductions are made to enclosed waters, whether cage and run-of-river fish farms or ponds containing stocked trout or coarse fish. However, containment is a major concern. A major concern is to contain these species, whether it be rainbow trout escaping from fish farms or fish stocked into stillwaters. There are six rainbow trout farms in the district, four run of river (two on the upper Earn, one on the Almond and one on the Ericht) and two cage sites (Loch Earn and Loch Tay) Freshwater lice (Argulus) Two species of the freshwater fish louse Argulus have been found in the Tay district. The riverine species, Argulus coregoni, is established in slower flowing sections of the lower Earn, lower Tay and lower Isla. It was also spread to Glenfarg reservoir with abstracted water from the River Earn. Argulus foliaceus, a stillwater species, was first recorded in the Tay district at Sandyknowes rainbow trout fishery, Bridge of Earn, in the mid 1990s. Significant mortalities of rainbow trout occurred. It has since been recorded in Lindores Loch, Fife, and Fingask Loch, Blairgowrie, which are both stocked rainbow trout fisheries. Such are the scale of infestation which can occur in warm summers that the stocking of rainbow trout has been suspended at Lindores in summer. Argulus foliaceus is a very serious threat to other lowland shallow stillwaters where high summer water temperatures can be generated. It threatens any salmonid fisheries in them and may be untreatable. Figure 4.12: Locations where Argulus has been found, Tay district 45

47 Invasive plants While not always a direct fisheries issue several invasive plant species are becoming increasingly common in the Tay district. Compared to some other districts giant hogweed is as yet very localised. However, Himalayan balsam is widespread (Fig. 4.13) and continues to spread rapidly. On banks which are not grazed it competes vigorously with existing flora and rapidly achieves dominance over native species. Japanese knotweed is much less widespread, although it is extensive on some parts of the Earn, but is an extremely pernicious plant, which can completely dominate riverbanks and can as yet only be eliminated by protracted use of herbicide. Figure 4.13: Sites where Himalayan balsam was present and not present, 2006 Figure 4.14: Sites where Japanese knotweed was present and not present,

48 4.20 Multi-stock interceptory net fisheries While almost no legal commercial salmon netting now occurs within the Tay district some fisheries still operate in the North Sea off the coast of Northumberland and in the neighbouring Esk district and beyond. Recaptures of adult salmon tagged in the Tay as smolts by Fisheries Research Services prove these fisheries do catch a proportion of Tay salmon. While the scale of these fisheries has reduced considerably it is possible that perhaps as many as several thousand salmon may be lost to the Tay system annually through such fisheries Illegal fishing Illegal fishing for salmon and trout was formerly a considerable problem in the Tay district. The scale of these activities has markedly reduced in recent decades. Very few cases relating to salmon are now reported to the Procurator Fiscal and most of these are for angling related offences. While poaching is not as attractive as it once was there is still a latent threat and activity would certainly increase in the absence of an enforcement effort. Therefore the Tay District Salmon Fisheries Board still expends a significant part of its expenditure in this area Forestry Forestry can have significant effects on freshwater fisheries. Ploughing of steep upland soils in high rainfall areas can lead to erosion and increased loads of sediment in receiving watercourses. Rapidly growing trees take up nutrients, reducing the amount of nutrient leakage into water courses, although this can be offset by artificial fertilisation. The litter from coniferous trees has an acidifying effect on the soil which can be exacerbated by conifers ability to scavenge acidifying pollutants from the atmosphere. Coniferous forests, and indeed broadleaves, can increase the rate of evapo-transpiration in summer, leading to lower summer flows. When planted close to narrow watercourses the shade created by coniferous trees can suppress biological activity. However, the extent to which any of these becomes a problem in reality depends on local factors. There is a significant amount of forestry in the Tay district, although it still amounts to a relatively small proportion of the overall total area (Fig. 4.15). The greatest concentration is in the central upland area, on Dalradian rocks which are relatively well buffered and relatively resistant to acidifying effects. The area most at risk from acidification must be the extensive forest on granite in the south Rannoch area with the Strathfillan / Tyndrum area being next most vulnerable. In practice, salmonid productivity is indeed relatively low in the forested Abhainn Duibhe at Rannoch, but the River Fillan is particularly productive of juvenile salmon, both in terms of density and growth rates in spite of forestry. Indeed its productivity increases as the proportion of forested catchment increases. Also, while forestry does cover a large area, relatively few watercourses which are accessible to migratory fish do in fact flow through these. Therefore overshading by 47

49 conifers is not as extensive a problem for migratory fish as shading by broadleaved trees (Section 4.11), although there are places where it does occur. Figure 4.15: Distribution of woodland, Tay district 4.23 Climate change The expected continued rise in global temperatures will become a major challenge for freshwater fisheries in the Tay district. There will be impacts at sea which will have a major bearing on migratory fish populations in ways which may be very difficult to predict. But within freshwater there will be winners and losers. Species like Arctic char which had a low thermal tolerance may be earliest affected, then brown trout. Salmon may be initially be more resilient as they have a higher thermal tolerance than brown trout. Indeed, if peak summer temperatures are not excessive they may benefit from an extended growing period in spring and autumn. Any increase in extreme weather events, whether flash floods or droughts, may prove even more damaging. Warmer conditions will however be more beneficial for cyprinid species and will see increasing occurrence of parasites like Argulus Morphology The shape and physical features of river and stream channels are a fundamental part of the habitat of fish and their food sources. These do vary naturally but human impacts have been significant. Important issues include: 48

50 Juxtaposition of spawning and rearing habitats for salmon and trout For natural reasons, rivers rarely have an ideal juxtaposition of spawning areas and juvenile habitat. There is usually a surfeit of one or the other. In most river habitat enhancement schemes in the British Isles the issue has been to increase juvenile habitat at the expense of spawning habitat but in the upland tributaries of the Tay the main issue is more likely to be a surfeit of bouldery habitat suitable for salmon parr with relatively few areas of good spawning gravels. In most instances this is a product of the channel slope (e.g. Ardle, Blackwater, Tilt and Ruchill) but sediment starvation below dams or natural lochs may be an issue in some others (e.g. upper Lyon, Errochty water, Tummel below Loch Tummel). Figure 4.16: In many parts of the British Isles there is a surfeit of shallow spawning habitats, often exacerbated by grazing induced erosion (left). However, many of the Tay s upland tributaries are dominated by bouldery habitat (right) which is good for salmon parr but poor for spawning Channel realignment In low gradient agricultural areas the great majority of streams have been subjected to historical channelization i.e. natural meandering channels have been straightened for drainage purposes. Channelization is usually considered a bad thing as it often results in a loss of natural physical variation. Restoration of channel sinuosity is now widely promoted in the UK and is often considered to be one of the key goals of the Water Framework Directive. However, channelization does usually result in an increase in channel slope which could in some instances have improved habitats for juvenile salmon which prefer faster flowing riffle habitats. Therefore, like many other issues, the effects of channelization are likely to be specific to individual streams Bank and flood protection works In some parts of the Tay catchment considerable lengths of embankments and levees have been erected to prevent flooding of adjoining land. There is also a lesser amount of artificial bank protection works to prevent erosion. While some of these works can actually be beneficial for freshwater fisheries, there have been negative 49