THE NUMBER OF UNDERYEARLINGS OF ROACH, BREAM AND PIKE-PERCH IN THE WESTERN PART OF THE NORTHERN CASPIAN SEA IN 2012-2016

Abstract

The article presents the data obtained in the result of scientific research expeditions aiming to determine abundance of roach ( Rutilus caspicus ), bream ( Abramis brama ) and pike-perch ( Sander lucioperca ) in the water area of the Western part of the Northern Caspian Sea in September-October 2012-2016. Roach and bream fingerlings, that are the largest part of anadromous fishes of the Volga-Caspian fishery basin, predominate in catches of minnow trawls. Theirs total share is 85.9-99.6%. Weight density of pike-perch is not so great - 0.2-2.0%. Level of yield of roach, bream, pike-perch fingerlings in the Northern Caspian Sea varies from year to year (roach 4.5-7 mln, bream 4.0-12.9 mln, pike-perch 0.030-0.163 mln specimens) and determined by abiotic and biotic complex of factors, the general of which is the water content of the Volga river in the flood-time period. The number of young fishes increases in the period with high level of flowing, in low flowing times it decreases. The most favorable conditions for fish reproduction were in high-water periods in 2013 and 2016, and least favorable - in extremely law water periods in 2015. The maximum number of bream fingerlings reached in 2013, roach - in 2012 and 2013, bream - in 2016. The minimum number of all three fish species was noted in 2015. By the results of researches of bream breed, years 2012, 2013 and 2016 are considered not so great yielding years; years 2014 and 2015 are low-yield years. The breed of roach and bream from 2012 to 2016 are estimated like low yield years, which was determined not only due to low water level of the Volga river, but because of a decrease of the population number of these fish species and breeding population on breeding grounds.