Long-term case histories of ruffe (Gymnocephalus cernuus) introductions to four U.K. lakes containing native vendace (Coregonus albula) or whitefish (C. lavaretus) populations

摘要

The U.K. contains nine lakes which support native vendace (Coregonus albula (L.)) or whitefish (Coregonus lavaretus (L.)) populations, none of which are naturally sympatric with ruffe populations. Nevertheless, four of these lakes received accidental or unconsented introductions of ruffe between 1980 and 2001. This percid was first recorded in the vendace lakes of Bassenthwaite Lake and Derwent Water in 1991 and 2001, respectively, and in the whitefish lakes of Loch Lomond and Llyn Tegid in 1982 and 1980, respectively. Subsequent changes in fish communities and native coregonid population biology have been monitored and investigated to varying degrees in all four lakes using survey gill netting and hydroacoustics. In Bassenthwaite Lake, no vendace have been recorded in routine monitoring since 2000, although this site also suffers from problems of other species introductions, depositions of fine sediments and eutrophication. In contrast, the vendace population of Derwent Water and the whitefish populations of Loch Lomond and Llyn Tegid have persisted. The results of these investigations are synthesised and their general implications for the understanding of the invasion ecology of ruffe in coregonid communities are discussed.