Scientific publications

The food spectra and trophic positions of the main fish species were studied in the subarctic lakes Imandra, Kuetsjarvi and Krivoe. Two methods were used: stomach contents analysis and stable isotope analysis. The analysis of stable carbon isotopes (δ13C) showed that vendace (Coregonus albula) primarily consumed pelagic organisms (δ13C values from –27 to –25 ‰), while European perch (Perca fluviatilis), European whitefish (Coregonus lavaretus, large sparsely rakered form), ruffe (Gymnocephalus cernua) and others were more dependent on benthic and littoral sources (their δ13C was near –24 ‰). The highest average nitrogen values (δ15N) were found in burbot from lakes of the Murmansk Region (about 14 ‰), as well as in smelt and ruffe (14–16 ‰) in Lake Imandra. In terms of their food preferences, perch and whitefish in all reservoirs were generalists. In addition, their trophic positions in Lake Imandra were similar. The similarity of their diets (measured by the Morisita-Horn index) was 42–49 % in coinhabitant populations, interpreted as moderate similarity, indicating the use of the same resources, but with competition for food not yet critical for these species. Aquatic and aerial insects (primarily Trichoptera) were the most common components in the diet of both species. However, the possible future range expansion by perch due to climate warming may escalate competition with whitefish, entailing a decline in whitefish numbers in the northern regions.