Abstract
The article presents new data on biology and ecology of invasive ichthyofauna of the Middle Irtysh basin on the territory of Pavlodar region. Using the literature data, the species composition of alien species inhabiting the upper, middle and lower reaches of the Irtysh River is summarized. In the Middle Irtysh basin, 15 invasive fish species belonging to 5 families and 13 genera are currently registered. The largest number of species belong to the carp family (9 species or 60%), salmonids include 3 species or 20%, other families are represented by one species. Only three species have acclimatized and entered the fishery in the Middle Irtysh basin: bream, carp (carp) and pikeperch. The share in commercial catches is from 15.7 to 27.7% for bream, from 0.2 to 1.5% for carp and from 0.8 to 1.3% for pikeperch. The largest number of caught bream individuals was registered in backwaters, carp in channels and lakes, pikeperch in Irtysh channels. The data on growth rate of these three fish species with the results of regression analysis are given. Data on the results of introduction of 11 more fish species are briefly summarized. It is concluded that spontaneous introductions sometimes lead to complete reorganization of biocenosis as a result of introduction of predator or food competitor, transfer of dangerous parasites or diseases. Most often, after a small “acclimatization effect” a water body not ready for the press of an introduced species becomes impoverished and becomes unattractive for fishermen and unpromising for commercial fish farming. Given that the problem of alien fish species is a serious environmental problem, its solution requires a comprehensive approach including scientific research, monitoring, management and educational programs.