Fishes of Rivers of the Forest-Steppe Zone of the Dnieper Basin: Long-Term Changes of the Species Composition and Abundance

Abstract

The paper deals with analysis of changes of the species composition and relative abundance of 63 species of fishes and Cyclostomata of the upper section of the Middle Dnieper and its 12 tributaries. The analysis covered period from the native ichthyocenoses state (1931-1972) to the crisis period (2001-2021). Over the considered period 7 aboriginal species have become extinct, at the same time 18 invasive species have settled. Over the last 50 years portion of the invasive species in the rivers on average increased from 10.1 to 30.2%, and their portion in the catches from 2.1 to 25.3%. Average species number per river increased by 7.9, decreased by 7.3, whereas constant component amounted to 19.8. The species diversity was also redistributed, it increased within the same river, but decreased between the rivers owing to universalization of the species composition (by 4.9% in terms of the Jaccard coefficient). The large-scale changes mean that deformation of ichthyofauna of the upper section of the Middle Dnieper basin exceeds the average-European level. At this, the general tendency consists in replacement of the autochthonous species by the allochthonous, whereas the rheophilic benthos-eating long-mature fishes with the prolong migration paths are the first to extinct. The critical group comprises eight commercial species, four of them (Acipenser gueldaenstaedtii, A. stellatus, Huso huso, Rutilus frisii) are extinct in the region, and populations of four more (Acipenser ruthenus, Chondrostoma nasus, Leuciscus idus, Vimba vimba) reduced tens and hundreds of times. These species need special protection, and V. vimba - inclusion to the Red Data Book of Ukraine.