Dynamics of distribution of inconnu in the riverbeds depression of the Irtysh River

The studies were performed by the hydroacoustic method in the section of the lower reaches of the Irtysh River (Western Siberia, Tyumen Region). The density dynamics of a group of fish with a symmetrical swimming bladder (Coregonidae and Esocidae) in the water areas of the riverbeds depression was studied. Among coregonids, inconnu dominates. The share of this group of fish is in the range of 10-11% of the total density of the fish population, and the density is an average of 0.3 thousand individuals ha¹. Fish density has an inverse statistically significant correlation with the water level factor and the inverse correlation with the water temperature. Lower Irtysh is a wintering and feeding section for inconnu individuals; here, inconnu are formed aggregations in river areas called riverbeds depression.