Assessment of reproduction volumes ensuring the formation of beluga reserves in accordance with the Caspian Sea fodder productivity

Abstract

Based on a model describing changes in the number and biomass of fish generations during the life cycle with natural mortality depending on the age of fish, quantitative characteristics of the conditional population of the Caspian Beluga, which is formed with an annual replenishment of 1.0 million copies, are calculated. young of the year. Calculations of the number, biomass, annual production and P/B — coefficients were also performed for conditional populations of Volga-Caspian fish included in the Beluga food spectrum. Studies have shown that the number and biomass of generations formed from fingerlings and conditional populations of the studied species depends on the growth rate of their young in the first year of life, as well as on the size and body weight at which 50 % of the individuals of the generations Mature. Among the studied fish species, Beluga is the most productive. The lowest generation productivity and high natural mortality are observed in populations of short-cycle, early-maturing fish-Caspian keels, gobies, aterines, etc. The number of generations of the studied species changes during their life according to decreasing curves, the biomass-according to single-vertex parabolic curves with a maximum occurring at the age of 50 % of puberty. The highest annual output and P/B coefficients are observed in individuals of younger age. Individual and group feed ratios of fish increase with age. Using a physiological method, individual and population nutritional needs of a conditional Beluga population with a 20 % catch of spawning stock were calculated. Based on the obtained data on the absolute age structure of the conditional Beluga population, individual annual food needs and products of the consumed feed base, the volumes of artificial and natural reproduction are calculated, which ensure the formation of reserves and obtaining catches in accordance with its annual food needs and the products of the used feed base.