Vertebrate species: fish


1106 Atlantic salmon    Salmo salar   
   Follow link for UK biodiversity information on this species.

Background to selection

Distribution of SACs with species 1106 Salmo salar.  Click image for enlarged map.
Distribution of SACs with species 1106 Salmo salar. Click image for enlarged map.

Description and ecological characteristics

 

The Atlantic salmon Salmo salar is an anadromous species (i.e. adults migrate from the sea to breed in freshwater). Spawning takes place in shallow excavations called redds, found in shallow gravelly areas in clean rivers and streams where the water flows swiftly. The young that emerge spread out into other parts of the river. After a period of 1-6 years the young salmon migrate downstream to the sea as ‘smolts’. Salmon have a homing instinct that draws them back to spawn in the river of their birth after 1-3 years in the sea. This behaviour has resulted in genetically distinct stock between rivers and even within individual rivers, with some evidence of further genetic distinctiveness in the tributaries of large rivers.

 

Salmon rivers vary considerably in their ecological and hydrological characteristics and in the life-cycle strategies adopted by the salmon within them. There are particularly strong contrasts between southern and northern rivers, and the UK’s varied climate, geology and terrain means that high diversity can be found within some of the large rivers. The cool and wet climate in the north, often with harder, more resistant rocks and steeper slopes, results in salmon rivers that are sparsely vegetated, nutrient-poor and prone to sudden increases in flow (‘spates’) in response to heavy downfalls or sudden snow-melt. As a result, salmon may take several years to reach the smolt stage and migrate to sea. In the south, rivers flow across gentler terrain and softer rocks, in a warmer, drier climate. Here, salmon often grow sufficiently quickly to smolt as yearlings.

 

The species is subject to many pressures in Europe, including pollution, the introduction of non-native salmon stocks, physical barriers to migration, exploitation from netting and angling, physical degradation of spawning and nursery habitat, and increased marine mortality.

European status and distribution

 

The Atlantic salmon Salmo salar is widely distributed within the EU, ranging from Portugal in the south to Sweden and Finland in the north. The UK salmon population comprises a significant proportion of the total European stock. Scottish rivers in particular are a European stronghold for the species.

UK status and distribution Click to view UK distribution of this species

 

The Atlantic salmon Salmo salar is a widespread species in the UK and is found in several hundred rivers, many of which have adult runs in excess of 1000. The latest estimates of the UK spawning population size (ICES 2000) are, however, about 50% down on the ten-year average.

Site selection rationale

 

The UK salmon population is important in a European context, and this has influenced the selection of SACs. Site selection has focused on the identification of rivers holding large salmon populations across the geographical range of the species in the UK. Site selection has also taken into account the considerable variation in the ecological and hydrological characteristics of salmon rivers in the UK, and in the life-cycle strategies adopted by the salmon within them. Spawning and nursery requirements are well-represented in all the selected sites, and the river systems selected include the main tributaries where significant redds occur.

 

It should be noted that salmon is an Annex II species only in freshwaters throughout the EU, and therefore marine and estuarine sites are excluded from selection.

 

While the SAC series makes a contribution to securing favourable conservation status for this Annex II species, wider measures are also necessary to support its conservation in the UK. The UK has extensive legislation intended to protect the species


Site accounts

Afon Gwyrfai a Llyn Cwellyn West Wales and The Valleys
The Afon Gwyrfai in north-west Wales is representative of the small montane rivers in this region. It contains a largely unexploited salmon population with a characteristically late run. Environment Agency electrofishing data indicates the presence of healthy juvenile populations downstream of Llyn Cwellyn.
Afon Teifi/ River Teifi West Wales and The Valleys
The Teifi is a medium-sized mesotrophic river system in west Wales. In 1999 the salmon Salmo salar rod catch in the Teifi was the third-largest in Wales, and the system has not experienced the steep decline in stock numbers seen in many other rivers in the area. This is likely to reflect the high quality of the catchment, with a semi-natural channel largely unaffected by poor water quality or artificial barriers to migration. However, in common with many other Welsh rivers, acidification in the upper reaches is a cause for concern. In common with many other rivers in west Wales, grilse are the main stock component. There is a small traditional coracle fishery that exploits the salmon and sea trout Salmo trutta trutta.
Berriedale and Langwell Waters Highlands and Islands
The Berriedale and Langwell Waters on the north-east coast of Scotland support small, but high-quality salmon Salmo salar populations. The rivers have two separate catchments, but share a short length of river just before they meet the sea. Both rivers are oligotrophic, draining the southern edge of the Caithness and Sutherland peatlands, and show only limited ecological variation along their length. Whilst they are comparatively small rivers and support only a small proportion of the Scottish salmon resource, their long history of low management intervention means that they score highly for naturalness. Recent records indicate that the full range of Atlantic salmon life-history types return to the river, with grilse, spring and summer salmon all being caught.
Langavat Highlands and Islands
The Grimersta river and loch system represents a high-quality salmon Salmo salar population in the Western Isles. The system has a high proportion of lacustrine rearing area for salmon, in contrast to their more usual preference for riverine conditions. These unusual habitat conditions are found elsewhere in the Atlantic salmon’s range in Newfoundland and in parts of Iceland. Whilst there is considerable habitat diversity in the Grimersta, its overall productivity is limited by the oligotrophic conditions which are found throughout the system. Although a high proportion of the catchment is accessible to salmon, Grimersta’s comparatively small size in relation to those on the mainland means that it only supports a small proportion of the Scottish salmon population, but it is the best salmon system in the Western Isles.
Little Gruinard River Highlands and Islands
The Little Gruinard River supports a high-quality salmon Salmo salar population in a Scottish west coast spate river fed by a chain of large lochs. It is oligotrophic, with low levels of species diversity and productivity. In contrast to many west Highland systems, the catch of salmon in the Little Gruinard has not shown the same level of decline as has been reported in other areas. It is likely that the enlightened policy of catch and release which operates on the river has been significant in protecting it from the worst effects of the problems affecting many other rivers throughout the region. The stock of adult salmon in the Little Gruinard is dominated by grilse which return to the river having spent one winter at sea, although smaller numbers of adults which have spent two winters at sea also return to the river in the late spring and summer. The catch and release policy is complemented by a range of other management initiatives, including a riparian enhancement scheme, all of which have contributed to the river’s wellbeing.
River Avon Dorset and Somerset, Gloucestershire, Wiltshire and Bristol/Bath area, Hampshire and Isle of Wight
The Avon in southern England represents a south coast chalk river supporting Atlantic salmon Salmo salar. The salmon populations here are typical of a high-quality chalk stream, unaffected by the introduction of genetic stock of non-native origin. The Avon has an excellent mosaic of aquatic habitats, which include extensive areas of gravels essential for spawning and growth of juvenile fry. There has been limited modification of the river course by comparison with many other southern lowland rivers in England.
River Bladnoch South Western Scotland
The River Bladnoch supports a high-quality salmon population in south-west Scotland, which unusually for rivers in this area still supports a spring run of salmon. The river drains a moderate-sized catchment with both upland and lowland areas, and this variety is reflected in the river’s ecological and water quality characteristics. Whilst there are problems in the river’s headwaters arising from acidification, national and local initiatives are both reducing and ameliorating the worst effects of this pollution source.
River Dee North Eastern Scotland
The River Dee supports a high-quality Atlantic salmon Salmo salar population in a river draining a large catchment on the east coast of Scotland. There is a weak nutrient gradient along its length, but it is essentially a nutrient-poor river. The high proportion of the river accessible to salmon has resulted in it supporting the full range of life-history types found in Scotland, with sub-populations of spring, summer salmon and grilse all being present. The headwaters which drain the southern Cairngorm and northern Grampian mountains are particularly important for multi sea-winter spring salmon, but there has been a significant decline in their abundance in recent years. The extensive areas accessible to salmon means the River Dee supports a significant proportion of the Scottish salmon resource. In recent years it has contributed about 4 or 5% of all salmon caught in Scotland.
River Dee and Bala Lake/ Afon Dyfrdwy a Llyn Tegid Cheshire, East Wales, Shropshire and Staffordshire, West Wales and The Valleys
Species occurrence account not yet available.
River Derwent and Bassenthwaite Lake Cumbria
The Derwent represents Atlantic salmon Salmo salar populations in north-west England and is a particularly good example of a large oligotrophic river flowing over base-poor geology, providing a contrast to the more mesotrophic River Eden. Low intensity land-use in the catchment means there is good water quality throughout much of the system. This water quality, coupled with the presence of extensive gravel shoals, makes it a particularly suitable river for breeding and enables it to support a large population.
River Eden Cumbria, North Yorkshire, Northumberland and Tyne and Wear
The Eden represents one of the largest populations of Atlantic salmon Salmo salar in northern England. It is an excellent example of a large river system that flows over varied, base-rich geology. This coupled with its large range in altitude, results in the development of distinct habitat types, supporting diverse plant and invertebrate communities. The high ecological value of the river system and the fact that the salmon are able to use most of the catchment (even above Ullswater, a large natural lake on the main river), mean that the Eden is able to maintain a large population of salmon.
River Faughan and Tributaries Northern Ireland
Species occurrence account not yet available.
River Foyle and Tributaries Northern Ireland
The River Foyle and Tributaries is a large, cross-border river in the north-west of Britain and Ireland. The river is notable for the physical diversity and naturalness of the banks and channels, especially in the upper reaches, and the richness and naturalness of its plant and animal communities.

 

The river has the largest population of Atlantic salmon Salmo salar in Northern Ireland, with around 15% of the estimated spawning numbers. The majority of the salmon returning are grilse (single wintering salmon), with a smaller but important number of spring salmon (multi-wintering salmon) also occurring. Research has indicated that individual sub-catchments within the system support genetically distinct salmon populations.

River Naver Highlands and Islands
The River Naver and its major tributary, the Mallart, flow from a large peatland catchment northwards to its mouth on the north coast of Scotland. The site supports a high-quality salmon Salmo salar population and, along with the Rivers Borgie and Thurso, is representative of the northerly part of the species’ range in the UK. The northern location of the River Naver and the cooler ambient water temperature results in the Atlantic salmon producing a higher proportion of slower-growing parr which smolt at an older age. These fish often return as multi sea-winter salmon (which have spent more than one year at sea). The full range of Atlantic salmon life-history types return to the system, with grilse, spring and summer salmon all being present. The site also scores highly for being relatively free from flow modifications, allowing unhindered migration.
River Roe and Tributaries Northern Ireland
Species occurrence account not yet available.
River South Esk Eastern Scotland
The South Esk supports a large, high-quality salmon Salmo salar population in a river draining a moderate-sized catchment on the east coast of Scotland. It has a strong nutrient gradient along its length, rising in the nutrient-poor Grampians and flowing for half of its length through the rich agricultural lands of Strathmore. The high proportion of the South Esk which is accessible to salmon and the range of ecological conditions in the river allows it to support the full range of life-history types found in Scotland, with sub-populations of spring, summer salmon and grilse all being present.
River Spey Eastern Scotland, Highlands and Islands
The Spey supports one of the largest Atlantic salmon Salmo salar populations in Scotland, with little evidence of modification by non-native stocks. Adults spawn throughout virtually the whole length of the river, and good quality nursery habitat is found in abundance in the main river and numerous tributaries. Salmon in the Spey system are little affected by artificial barriers to migration, and the waters in the catchment are largely unpolluted (the river is oligotrophic throughout its length). For a system of its size, the Spey is also relatively free from flow modifications such as abstractions, diversions and impoundments. The salmon population includes fish of all ages including migrating smolts and returning adults, possibly reflecting genetic differences within the Spey stock.
River Tay Eastern Scotland, Highlands and Islands
The River Tay supports a high-quality Atlantic salmon Salmo salar population, with rod catch returns showing that the Tay is consistently one of the top three salmon rivers in Scotland. In 1999 the catch was 7230 fish, over 10% of the Scottish total. The Tay drains a very large catchment, and has the greatest flow of all UK rivers. There is considerable ecological variety in the Tay catchment, resulting in the Tay supporting the full range of salmon life-history types found in Scotland, with adult salmon entering the River Tay throughout the year to spawn in different parts of the catchment.

River Thurso Highlands and Islands
The River Thurso drains a moderately large peatland catchment in Caithness and flows north through a short section of agricultural land before entering the Pentland Firth at the town of Thurso. The river supports a higher proportion of multi sea-winter salmon Salmo salar than is found in many rivers further south in the species’ range. This is aided by the northerly location of the river and the cooler ambient water temperature, resulting in slower-growing juveniles which smolt at an older age, and tend to return as older multi sea-winter salmon. In addition to these multi sea-winter fish, grilse also return to the River Thurso, meaning that the river supports the full range of salmon life-history types.
River Tweed Eastern Scotland, Northumberland and Tyne and Wear
The River Tweed supports a very large, high-quality salmon Salmo salar population in a river which drains a large catchment on the east coast of the UK, with sub-catchments in both Scotland and England. The Tweed is the best example in Britain of a large river showing a strong nutrient gradient along its length, with oligotrophic conditions in its headwaters, and nutrient-rich lowland conditions just before it enters the sea at Berwick. The high proportion of the River Tweed accessible to salmon, and the variety of habitat conditions in the river, has resulted in the Scottish section of the river supporting the full range of salmon life-history types, with sub-populations of spring, summer salmon and grilse all being present. The extensive system supports a significant proportion of the Scottish salmon resource. In recent years, the salmon catch in the River Tweed is the highest in Scotland, with up to 15% of all salmon caught. Considerable work has been done by the Scottish Environment Protection Agency (and previously the Tweed River Purification Board) and the River Tweed Foundation in tackling pollution and easing the passage of salmon past artificial barriers in the river. This has reversed many of the river’s historical problems with water quality and access for salmon.
River Usk/ Afon Wysg East Wales, West Wales and The Valleys
The river Usk is a river famous for its salmon Salmo salar, with a high proportion (c. 3040%) of multi sea winter fish recorded in the rod catch. In 1999 the Usk had highest estimated egg deposition of any British river south of Cumbria, and was one of the few rivers in England and Wales to exceed its spawning target for salmon. The Usk has a mixed catchment with a largely unmodified river channel, no significant obstructions to salmon migration, good quality spawning gravels and a diversity of habitats providing excellent habitat for salmon parr. The most important tributaries for salmon spawning are included within the site boundary.
River Wye/ Afon Gwy East Wales, Gloucestershire, Wiltshire and Bristol/Bath area, Herefordshire, Worcestershire and Warwickshire, West Wales and The Valleys
Historically, the Wye is the most famous and productive river in Wales for Atlantic salmon Salmo salar, with high-quality spawning grounds and juvenile habitat in both the main channel and tributaries; water quality in the system is generally favourable. It is also one of the most diverse river systems in the UK, with a transition from hard geology, high gradients, rapid flow fluctuations and low nutrient-content in its upper reaches, to a more nutrient-rich river with lower gradient, more stable flow and softer geology in the lowlands. The effect of river engineering work on migration and spawning has been limited, although there is a localised influence from the Elan Valley reservoirs, through inundation of spawning and nursery habitat and fluctuations in flow and water levels in the upper Wye. The most important tributaries for spawning are included in the SAC. Although in the past non-native salmon may have been released to the system, the impact of this is likely to have been minimal. The Wye salmon population is particularly notable for the very high proportion (around 75%) of multi sea winter (MSW) fish, a stock component which has declined sharply in recent years throughout the UK. This pattern has also occurred in the Wye, with a consequent marked decline in the population since the 1980s. However, the Wye salmon population is still of considerable importance in UK terms.

SACs where this Annex II species is a qualifying feature, but not a primary reason for site selection

Afon Eden - Cors Goch Trawsfynydd West Wales and The Valleys
Dartmoor Devon
Endrick Water Eastern Scotland, South Western Scotland
Lough Melvin Northern Ireland
North Harris Highlands and Islands
Owenkillew River Northern Ireland
River Borgie Highlands and Islands
River Camel Cornwall and Isles of Scilly
River Ehen Cumbria
River Itchen Hampshire and Isle of Wight
River Moriston Highlands and Islands
River Oykel Highlands and Islands
River Teith Eastern Scotland
 

Many designated sites are on private land: the listing of a site in these pages does not imply any right of public access.