Fauna of Scotland - Fish, Sea and River Life

Fish, Sea and River Life

Of the 42 species of fish found in Scottish fresh waters, only half have arrived by natural colonisation. Native species include Allis Shad, Brown Trout, European Eel and River Lamprey. Scottish rivers support one of the largest Atlantic Salmon resources in Europe, with nearly 400 rivers supporting genetically distinct populations. Five fish species are considered ‘late arrivals’ to Scotland, having colonised by natural means prior to 1790. They are the Northern Pike, Roach, Stone Loach, European perch, and Minnow. Rarer native species include the endemic Salvelinus killinensis and the Powan, the latter found in only two locations and under threat from introduced Ruffe and the Arctic Charr. The latter may have been the first fish species to re-enter fresh waters when the last ice age ended, and about 200 populations exist.

The Freshwater Pearl Mussel was once abundant enough to support commercial activities, and Scotland is the remaining European stronghold with about half the global number present. There are populations in more than 50 rivers, mainly in the Highlands, although illegal harvesting has seriously affected their survival.

Scotland's seas, which constitute an area greater than that of the seas around the rest of the UK, are among the most biologically productive in the world. They are home to a third of the world's whale and dolphin species, most of the UK's maerl, (a collective term for several species of calcified red seaweed, and an important marine habitat), Horsemussel (Modiolus modiolus) and seagrass beds, and distinctive species like the Tall Sea Pen, Funiculina quadrangularis. It is estimated that the total number of Scottish marine species exceeds 40,000. This includes 250 species of fish, the most numerous inshore variety being Saithe, and deeper water creatures such as the Dogfish, Porbeagle and Blue Shark, European Eel, Sea Bass, Atlantic Halibut and various rays. There are four species of sea turtle, the Leatherback, Loggerhead, Kemp's Ridley and Green Turtle. Scottish waters contain around 2,500 crustacean species and 700 molluscs and in 2012 a bed of 100 million Flame Shells was found during a survey of Loch Alsh.

The Darwin Mounds, an important area of cold water coral reefs discovered in 1988, are about 1,000 metres (3,300 ft) deep in the Atlantic Ocean, about 185 kilometres (115 mi) north-west of Cape Wrath in the north-east corner of the Rockall trough. The area covers approximately 100 square kilometres (39 sq mi) and contains hundreds of mounds of about 100 metres (330 ft) in diameter and 5 metres (16 ft) in height, many having a teardrop shaped ‘tail’ orientated south-west of the mound. This feature may be unique globally. The tops of the mounds have living stands of Lophelia corals and support significant populations of the single-celled Syringammina fragilissima. Fish have been observed in the vicinity but not at higher densities than the background environment. Damage from trawler fishing was visible over about a half of the eastern Darwin Mounds surveyed during summer 2000, and the UK government is taking steps to protect the area. In 2003 the European Commission provided emergency protection and banned damaging fishing activity in the locality.

Further action on a much wider scale may be required. According to a recent report "Scotland's marine life could be almost wiped out within 50 years unless tough action is taken to manage the way humans use the seas". Fears were expressed by a consortium of environmental organisations that commercial fish stocks, including Atlantic Cod are suffering from over-fishing, that fish farming, especially for salmon is damaging the aquatic environment, a reduction in coastal marsh habitats is affecting marine bird life, litter in densely populated estuaries such as the Firth of Clyde is affecting all forms of marine life and that the growth in off-shore tourism was deleterious to populations of, for example, Basking Shark. A call was made for a 'Scottish Marine Bill' to co-ordinate and manage human activity at sea and to provide more protected areas such as marine national parks. The Marine (Scotland) Act 2010 was subsequently passed by the Scottish Parliament.

Calyptraea chinensis (L.) is a gastropod that has invaded the shores of Scotland and by 1998 had reached nearly as far north as Oban. One living specimen was found at Clachan Sound, and earlier records showed findings of gastropod shells.