Fish distribution in the small mountain lakes in the Kosju river basin (the Pre-Polar Urals)

The ichthyofauna and the fish community of mountain lakes in the basin of the Kosju River headwaters (the second-order tributary of the Pechora River) were initially surveyed. Extremely high river falls and flow rates, the climate pattern of the western slopes of the Pre-Polar Urals and the small size of the majority of the lakes determine severe and extreme fish habitat conditions. Ichthyological materials were collected using generally accepted methods of ichthyological research. Fish was caught using standard stake gill nets (10-60 mm mesh size) and spinning rods. In total, seven fish species were detected in the local ichthyofauna, which belong to five families: Arctic char, pike, common and lake minnow, roach, burbot and perch. Specific extremely rough fish habitat conditions in the lakes belonging to the basin of the Kosju River headwaters at an elevation of 300-600 meters above sea level had a major impact both on a poor composition of the ichthyofauna and the composition of the fish community. With few exceptions, the lakes are inhabited with one or two fish species, and one of them absolutely dominates in numbers. The majority of the fish species inhabiting the lakes presented in this paper are characterized by an extremely low value of the relative density index; roach and perch demonstrate maximum values. In some of the lakes stunted aggregations of Arctic char, roach and burbot were detected.