Abstract

The fish complex of the tributaries of the Upper Tom’ river (Nizhnyaya Tykhta and Talda), were studied. The surveyed rivers flow through the territory of the western part of the Kuznetsk Alatau (Tardanovsky Uplands). Against the background of a high level of oxygen in both rivers, in terms of the volume of easily oxidized organic matter, the N. Tykhta River is more polluted than the Talda River. Four species inhabit in the Talda River and 7 species were registered in Nizhnyaya Tykhta. Watercourses are characterized by low levels of species richness and abundance of fish. An uneven distribution of fish in both rivers was revealed, which is associated with differences in the biotopic confinement of different species. Microbiotopes characteristic of different species act as refugia. The complex of alien includes crucian Carassius auratus, bleak Alburnus alburnus and verkhovka Leucaspius delineatus) and minnow Gobio gobio, dace Leuciscus leuciscus, siberian loach Cobitis melanoleuca, perch Perca fluviatilis and pike Esox lucius are representatives of native fauna. Despite the proximity of the rivers, the level of similarity of species composition is low, less than 30% (Jaccard index is 27.30). Species diversity according to the Shannon-Weaver index is 1.50 for the Nizhnyaya Tykhta River and 1.09 for the Talda River. The presence of alien species in the ichthyofauna of a more polluted river testifies to their higher adaptability to changing environment (shallowing, decrease in runoff, increase in the concentration of organic matter) compared to the populations of native species.

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