МНОГОЛЕТНЯЯ ДИНАМИКА УЛОВОВ, ЧИСЛЕННОСТИ И БИОМАССЫ ПОПУЛЯЦИИ СУДАКА (SANDERLUCIOPERCA L.) БЕЛОГО ОЗЕРА

Abstract

Until the end of the 20th century fish community in Beloye Lake had been mainly presented by smelt and zander, which resulted in the high volumes of the species catches, yearly variations changed synchronously. Dynamics of zander and smelt fishing in Lake Beloye in the period from 1940 to 2017 has been described. Since 1970s the volumes of their catch and the share in total catches have become gradually decreasing. The average catch made by the research trawl during 1 hour is taken as the main indicator of long-term fluctuations of abundance and biomass of zander population in Beloye Lake within 1970-2017. The main reason for the long-term decline of abundance of smelt and zander populations is the global warming. Smelt biomass rapidly declines in hot years, which results in a sharp decrease of the zander feed supply. The 6-7-year periods of massive reduction of abundance, biomass and catches of zander and smelt in Beloye Lake were recorded in the 1970s and 2000s. Against a background of a sharp decrease of smelt abundance, in 2001-2003 in Beloye Lake there were registered the most numerous zander generations, which caused a strong population imbalance. Thus, the abundance of small-sized fish increased in the 2000s and the commercial biomass of the population decreased rapidly, which led to a significant reduction of zander catches. Generally, against the outlined trend of climate warming, there grows the risk to lose the commercial status of reservation of the commercial status of smelt and zander populations in Beloye Lake in the future.