Vendace and powan: the coregonids
Vendace and Powan comprise a group known as the 'Coregonids'. Two species of coregonid are located within mainland Britain - Coregonus albula (vendace) and Coregonus lavaretus (known as powan in Scotland, schelly in England and gwyniad in Wales). Another species Coregonus autumnalis (known as pollan) is restricted to Irish waters.
Vendace - the rarest freshwater fish in Britain
Vendace, has a more restricted distribution than powan and until recently they currently found in only two lakes within mainland Britain. Both of these lakes, Bassenthwaite and Derwentwater are located within the English Lake District. In 2008 surveys concluded that the Bassenthwaite population was extinct.
Populations of this species used to occur in two locations in Scotland, Mill Loch and Castle Loch, but these are now also considered to be extinct. In the mid-1990's, fish from Bassenthwaite and Derwentwater were translocated to two waterbodies in the Scottish Borders, Loch Skeen and Daer Reservoir. These waterbodies were carefully selected from a number of other locations on the basis of their bathymetry, water chemistry, availability of spawning substrate and the presence of other fish species. The success of this attempt to re-establish vendace in Scotland and to safeguard the two existing English populations has recently been assessed. The vendace which were introduced into Loch Skeen from Bassenthwaite have become established there. The introduction of fish from Derwentwater to Daer Reservoir may not, unfortunately, have succeeded.
Powan - an ice-age relict
Powan are more widespread within the British Isles than vendace, but natural populations of this species are still restricted to just seven locations. In Scotland, natural powan distribution is restricted to Loch Eck and Loch Lomond. However, fish from Loch Lomond were transplanted to two other locations Loch Sloy and the Carron Valley Reservoir and have become established there. In Wales the distribution of powan is restricted to just one lake, Llyn Tegid. Attempts have been made to establish refuge populations of powan from Llyn Tegid. The English Lake District appears to be the stronghold for powan within the British Isles and this species is found in Ullswater, Haweswater, Red Tarn and Brotherswater. A translocation of powan from Haweswater to Small Water in 1997 has recently resulted in the establishment of a new breeding population there.
Vendace and powan habitat requirements
Both vendace and powan are commonly associated with deep, cool, well oxygenated lochs. In keeping with their environmental requirements, the distribution of these populations within the British Isles is polarised towards cool, mesotrophic and oligotrophic lakes in upland areas.
Challenges for vendace and powan
Recent attempts to translocate the most vulnerable populations has laid testimony to the fact that both species now face considerable challenges if they are to survive. They are highly susceptible to declines in water quality, increased siltation and de-oxygenation. Drawdown regimes for hydroelectricity of potable water also problematic if the species is present in reservoirs. The introduction of alien species, such as Ruffe, can also lead to population declines, or even loss.
Vendace and powan conservation status
Both vendace and powan are protected under Schedule 5 of the Wildlife & Countryside Act 1981 (as amended) and are listed on Appendix III of the Bern Convention; Annex Va of the EC Habitats & Species Directive and Schedule 3 of The Conservation (Natural Habitats, etc) Regulations 1994. Vendace also included in the Species Action Framework and appear in the UK Biodiversity Action Plan Priority Species list.
Last updated on Thursday 26th November 2015 at 15:31 PM. Click here to comment on this page