Distribution of trout in the Upper Ob basin

Rainbow trout Oncorhynchus mykiss (Walbaum, 1792) and brown trout Salmo trutta Linnaeus, 1758 are popular aquaculture species worldwide. At the same time, it is known that when these species enter natural water bodies, they are able to form self-reproducing populations and cause significant damage to native fauna due to food competition, hybridization with native species, and predation. In the basin of the Upper Ob in the second half of the twentieth century, there was not only a large aquaculture farm specializing in trout but also work was carried out to introduce trout into natural water bodies: lakes in the basins of Lake Teletskoye and the Katun river. It is known about the formation of a self-reproducing population of brook trout in Lake Lebedinoe (in the basin of the Pervaya Koksha River, a second-order tributary of the lower reaches of the Katun River), which still exists. Currently, rainbow trout is a popular object of aquaculture in southern Siberia; it is grown mainly for the purpose of organizing recreational fishing, often in water bodies that are not isolated from the river network. This determines the regular ingress of this species into rivers. Nevertheless, currently no evidence of natural reproduction of trouts in natural water in the Upper Ob basin, except in Lake Lebedinoe. However, given the high risks associated with the potential invasiveness of trouts, it is necessary to recommend a cautious attitude towards the distribution of these species and to provide for an environmental impact assessment of projects related to their cultivation in water bodies of Western Siberia.