ON METHODS OF ASSESSMENT OF THE RECEPTION CAPACITY AND COMMERCIAL FISHERY RETURN FOR ARTIFICIAL REPRODUCTION OF WHITE FISH (COREGONUS LAVARETUS L.) IN THE CURONIAN LAGOON
The article presents an original method for calculating the reception capacity of the Curonian Lagoon for artificial reproduction of whitefish. The technique is based on calculation of the number of sustainable population by means of modified W. Ricker model (1980). The model uses standard biological parameters: growth rate in accordance with the Bertalanffy equation, and the U-shaped curve of natural mortality approximated by a third degree polynomial. Polynomial coefficients were calculated based on two boundary conditions: the population natural mortality rate, estimated by F.I. Baranova (1918) methods (M = 2,578 1/year) and the minimum value of natural mortality at the age of maturity, in accordance with the method of L.A. Zykov (1986). A compensatory mortality rate at age 0+ was selected so as to achieve a stable state of population when the initial number N0 is equal to population fecundity. Then the initial number was chosen with the aim to achieve the catch equal to 20 tons which was observed in the years 1950-70. The result was determined by the receiving capacity of the reservoir and the coefficient of commercial return from the release of juveniles at different stages. The proposed approach is universal and does not require complex and highly inaccurate trophological research, but objectively take into account the biological parameters of the study population and its functioning in a particular ecosystem.