Biological characteristics of whitefish (Coregonus lavaretus L.) in Lake Vishtynetskoye (Kaliningrad region) in the modern period

The work is devoted to changes in the biological parameters of the freshwater form of whitefish under conditions of changing fishing intensity. During the historical period in Lake Vishtynetskoye maximum catches reached 4.5 tons in the beginning of 2000, the catch ranged from 0.1 to 2.0 tons (average 0.6 tons), this is a period of low TAC development (fluctuations from 100 to 10%, average 50%). In the period 2017-2022, catches amount to 0.6-1.0 tons (average 0.96 tons), a period of high TAC development (fluctuations from 50 to 100%, average development 75%). The material for the work was data obtained during the study of commercial catches (in the period 2000-2006) and data obtained from the results of control catches (2017-2022). In total, more than 3,000 networks were performed. The data on the size-species structure of the ichthyocenosis, the distribution of fish by depth and the size structure of whitefish are provided. Whitefish is an important component of the ichthyocenosis, accounting for up to 20% of the catch; maximum catches occur at depths of 15-25 meters. In control catches whitefish is found with a length from 15 to 53 cm. It is shown that in the compared periods there was a change in the average body length, it decreased by 0.6 cm, with an increase in average weight by almost 50 g. There was also an increase in the average age of whitefish, from 4.5 years to 5 years. The detected changes in the biological parameters of whitefish indicate a stable state of the population and the absence of a negative impact on it from fishing in the modern period, which indicates the correct determination of the TAC value.