Northern Ireland's Priority Species

Salvelinus alpinus – arctic charr

 
Salvelinus alpinus

Salvelinus alpinus (Linnaeus, 1758)
Family: Salmonidae

Arctic char (also spelt charr) is a salmonid fish that lives mainly in Arctic waters and has the most northerly distribution of all freshwater fish. In the northernmost part of their range char are migratory (anadromous), spawning in rivers and feeding as adults in the sea. Irish Arctic char are glacial relicts of a more southerly distribution during the last Ice age and have their entire life history in freshwater. In the nineteenth century, Arctic char populations in Ireland and elsewhere were classified into numerous species and subspecies, although most of these are likely to be invalid by today’s criteria. However, insufficient genetic information is available so far to allow a revision of the classification and Arctic char is currently referred to as a species complex. It is regarded by many as the tastiest of all of the salmonid fishes and is widely exploited and cultured in Northern Europe.

In brief

  • The only currently known population of Arctic char in Northern Ireland is in Lough Melvin, although it is possible that there are undiscovered populations in small, deep, remote lakes

  • Arctic char were once widespread in Northern Ireland but became extinct in Lough Neagh about 1844 and in Lough Erne in the early twentieth century

  • It is a deep water fish and therefore is rarely seen

  • Arctic char are rare and are classified in the Irish Red Data Book as vulnerable

  • Decline of Arctic char in the past may be linked to the introduction and spread of pike and currently are threatened by other non-native introductions, for example, cyprinids (rudd, roach, etc.) and zebra mussel, together with eutrophication and climatic warming

  • Melvin Arctic char were originally designated as a distinct species (S. grayi) or subspecies (S. a. grayi) but their taxonomy requires further genetic study

  • Irish Arctic char are glacial relicts of a more southerly distribution of a river-sea migratory (anadromous) species during the last Ice Age and spend their entire life history in freshwater.

Species description
Arctic char are a slender trout-like freshwater fish and possess the typical salmonid adipose fin (small fleshy fin) on the dorsal surface in front of the tail. It is the most brightly coloured of European salmonids, especially during the breeding season, when the males in particular have bright red bellies. The back is greenish brown and the sides are silvery, bluish-grey, or light brown, with small red, pink or yellow spots.

Life cycle
Arctic char spend most of the year in deep water (>10 metres) but come into shallow rocky and gravelly areas in November and December to spawn. In some lakes, Arctic char can spawn in the springtime as well as in the autumn, which can lead to two temporally reproductively isolated populations, but this has not been investigated in Lough Melvin. A low water temperature (<8°C) and good oxygenation due to wind or current action is required for successful development of the eggs. Animal plankton is the predominant food, although insect larvae are taken occasionally. The largest char taken by net in Lough Melvin was one of 27cm and 200g. The maximum recorded age for Irish char is nine years, but little extra growth occurs after three years, when maturity starts.

Similar species
There are no similar species in Britain or Ireland although young Arctic char could be confused with brown trout.

How to see this species
Lough Melvin is the only lake in Northern Ireland where Arctic char are currently known to occur, although they are present in many lakes in western Ireland from Donegal to Kerry. Since they live in deep water they are rarely seen and rarely caught by anglers, except in the autumn time in Lough Eske (Donegal). Anglers in Lake Windermere (NW England) have developed specialised deep water ‘plumb-line’ fishing techniques to catch char in that lake. Relevant access permissions should always be sought prior to visiting any sites.

Current status
Char were once widespread in Northern Ireland but became extinct in Lough Neagh about 1844 and in Lough Erne in the early twentieth century. The only currently known Northern Ireland population of Arctic char is in Lough Melvin, where they were abundant in the nineteenth century and were taken by the ‘cart-load’ at spawning time. Recent deep-water netting surveys in the Republic of Ireland have discovered a number of previously unknown populations and it is possible that there are unknown populations in small, deep, remote lakes in Northern Ireland. There is some evidence from netting surveys that char have declined in Lough Melvin in recent years. Over the past 25 years Arctic char have gone from being numerous to extinction in two large lakes (Conn, Corrib) in the Republic of Ireland.

Why is this species a priority in Northern Ireland?

  • This species is rare and is classified in the Irish Red Data Book as vulnerable.

Threats/Causes of decline
Arctic char are the most sensitive of all salmonids to decreased oxygen level and increased temperature and thus eutrophication and climatic warming are major threats. Introduction and spread of non-native species such as pike, roach and rudd are also likely to be detrimental and the recent extinction in Lough Corrib has been linked to the spread of roach. Introduction of the zebra mussel to Lough Melvin would most likely be highly detrimental to the char population due to decline in plankton availability.

Conservation of this species

Current action

  • Lough Melvin is designated as both an ASSI and a SAC

  • Implementation of the Northern Ireland habitat action plan for Mesotrophic Lakes.

Proposed objectives/actions

  • Maintain the existing Arctic char population in Lough Melvin at a viable level

  • Establish an ex situ conservation population of Melvin char in a suitable lake in Northern Ireland

  • Survey remote, deep lakes in Northern Ireland where Arctic char possibly still exists and, if found, maintain viable population.

What you can do
Support the restoration of Northern Ireland lakes to high water quality status. Anglers and other water users can help prevent the spread of zebra mussels to Lough Melvin by ensuring that they follow guidelines for cleaning boats, engines and all other equipment.

Further information

Links
http://www.charr.org/

http://www.ehsni.gov.uk/pubs/publications/mesotrophiclakes_pdf.pdf

http://www.ehsni.gov.uk/area_interest_sitesview?SiteNo=ASSI140

Literature
Ferguson, A. (1986). Lough Melvin – A unique fish community. Occasional Papers in Irish Science and Technology, no 1. Royal Dublin Society.

Igoe, F. and Hammar, J. (2004). The Arctic char Salvelinus alpinus (L.) species complex in Ireland: A secretive and threatened ice age relict. Biology and Environment: Proceedings of the Royal Irish Academy, 104B (3): 73-92. Available online at: http://www.ria.ie/publications/journals.

Whilde, A. (1993). Threatened mammals, birds, amphibians and fish in Ireland. Irish Red Data Book 2: Vertebrates. HMSO, Belfast.

Text written by:
Professor Andrew Ferguson