fish

ON THE CASTOR FIBER (CASTORIDAE, MAMMALIA) ACTIVITY INFLUENCE ON THE ECOSYSTEM BIODIVERSITY OF SMALL RIVERS IN THE FOREST-STEPPE ZONE

Preliminary data on the Castor fiber activity influence on the ecosystem biodiversity of small rivers in three steppe clusters within the State Nature Reserve “Volga forest-steppe” were obtained. With zooplankton, amphibians and fish as examples, it was shown that after beaver-made ponds had appeared, the abundance of all these groups increased. In old ponds, the fish abundance decreases whilst the amphibian one continues to increase. In drained ponds, the zooplankton and amphibian abundance decreases while the fishes become more numerous, due to the appearance of better flowability.

SPATIAL HETEROGENEITY OF THE ICHTHYOFAUNA OF NORTHERN EURASIA AND ITS BIOGEOGRAPHICAL DIVISION

Biogeographical division of Northern Eurasia (within the former USSR borders) was carried by the results of our cluster analysis of the fish fauna from 597 sites according to the BIODAT database territory division. Our classification obtained on the basis of the Jacquard similarity coefficients includes 2 regions, 12 dominion, 8 provinces, and 11 districts. The offered division considers 67% of the similarity coefficient dispersion of the fauna analyzed, which is by 21% higher than an earlier developed scheme (Berg, 1962) which includes a bigger area of the continent.