overview of fish species introductions to the English Lake District, UK, an area of outstanding conservation and fisheries importance

Fisheries management has a considerable capacity to precipitate legal and illegal introductions of fish species to new geographical areas. Consequently, there are many examples of such introductions and their subsequent short-term effects on native fish. However, longer-term impacts which may be expected to be more substantial have been less frequently studied in detail. For this overview, long-term datasets up to a number of decades in duration have been assembled from published and unpublished sources on the native lake fish communities of the English Lake District in north-west England, UK. These communities are dominated by simple salmonid-percid assemblages and contain England's only vendace (Coregonus albula), whitefish (Coregonus lavaretus) and Arctic charr (Salvelinus alpinus) populations, all of which are protected under nature conservation legislation. In addition, they have historically supported commercial or semi-commercial fisheries for perch (Perca fluviatilis), whitefish and Arctic charr, the latter of which still persist on two major lakes. In recent years, fisheries activities have resulted in the region experiencing a number of illegal fish introductions including the cyprinids roach (Rutilus rutilus) and dace (Leuciscus leuciscus) and the percid ruffe (Gymnocephalus cernuus). Although these introductions have benefited some local recreational fisheries, several instances of cultural eutrophication and a more widespread increase in lake temperature are likely to benefit these introduced species and disadvantage native salmonids and percids. The resulting changes in fish community compositions and the performances of local fisheries are described and discussed.