Habitat, diet and food assimilation of Arctic charr under the winter ice in two subarctic lakes

摘要: The Arctic charr Salvelinus alpinus populations of the subarctic lakes Takvatn and Fjellfrosvatn, north Norway, concentrated in littoral zones (0–15 m) during entire winter (December to May) despite very low temperatures (0·2 0·7° C). High prey availability, predation competition comparatively better light under snow ice shallow compared with deep water are probable reasons. At break June, all moved profundal zone for a brief period, probably response sudden increase resource peak chironomid pupae. In summer, found pelagic, lakes. These therefore perform regular habitat shifts between winter, at whole lake summer autumn. fish fed continuously cold poor light. Amphipods larvae dominated diet. Catch per unit effort, numbers stomachs food intake rates varied cycle but were lowest after solstice. assimilation energy was about equal standard metabolism higher Fjellfrosvatn. increased both spring May. choice, diet indicate that is well adapted extreme conditions