Temperature habitats for freshwater fishes in a warming climate

The effects of global warming on the six freshwater fish species, whitefish (Coregonus lavaretus (L.)), brown trout (Salmo trutta L.), bream (Abramis brama (L.)), roach (Rutilus rutilus (L.)), perch (Perca fluviatilis L.), and pikeperch (Stizostedion lucioperca (L.)), were studied on the basis of temperature scenarios made by the weather generator and the PROBE model. Two theoretical indices were used to evaluate the effects of warming on the fish species: temperature sum of growth habitat and the number of days when water temperature was above the lowest stress level. The results showed that cool- and warmwater species will benefit from warming in the whole of Finland while the habitats of coldwater species will shrink primarily in southern Finland. For all the selected species the growing season will start earlier, but for the coldwater species (whitefish and brown trout) epilimnic temperatures will rise above stress levels during the summer. This may cause population collapses of these species in the shallow lakes of southern Finland. The range of bream and pikeperch may shift northward to cover the whole of Finland by 2060.