Hatchery stock enhancement and conservation of sturgeon, with an emphasis on the Azov Sea populations

The regulation of river flows hampered natural reproduction of sturgeons in the Azov Sea basin. To develop a long-term strategy for stock enhancement, it is necessary to assess the effectiveness of the hatchery stocking programs. As a result of 60% reduction in river flow, the natural propagation of sturgeon in the Kuban River has been absent for the past 25 years. Up to 30 million juveniles of Russian and stellate sturgeon were released annually from five sturgeon hatcheries, the main sources of sturgeon recruitment in the Sea of Azov. The hatchery stocking strategy was aimed solely at the release of a large number of juveniles, utilizing only the most mature broodfish of the spring spawning run for breeding. While the monitoring of age, weight and physiological conditions of the broodstock during the period of hatchery breeding did not reveal significant changes, the spawning run was dramatically shortened ( to 15 days, compared with several months in the previous history of the spawning run) and included only fish with advanced gonadal maturity. The analysis of protein polymorphism suggested significant changes in stock genetic composition of stellate sturgeon related to the hatchery practices and stocking allopatric populations from the Caspian Sea. The traditional methods and technology of the artificial reproduction appear to be ineffective under present ecological conditions. The different, long-term, management strategy should be based on new concepts of stock enhancement and genetic assessment, to preserve the intraspecific diversity of sturgeon. This includes novel hatchery methods for controlled maturation and spawning of different ecotypes, and production and stocking of high-quality juveniles in the year-round timetable. Conservation of the Azov Sea species and their unique spawning ecotypes is currently supported by the Federal Living Gene Bank in the Krasnodar Region, which maintains over 7000 adults of the endangered species and populations. This genetic collection is used for research and restoration of the biodiversity of sturgeon in the Sea of Azov.