Bentofauna of coastal waters of the Tyuleniy island of the Caspian Sea

The article presents an assessment of the state of the bentofauna of the coastal waters of the Tyuleniy island on the basis of monitoring studies conducted in 2015-2016 years. According to the results of studies, high species diversity and quantitative development of the bottom fauna were noted. Studies have shown that Mollusca of Bivalvia class, especially Dreissena polymorpha polymorpha Pallas, 1771, play a determining role in the total biomass, which is more than 75 % of the total biomass of Molluscs, and Crustacea of Amphipoda group dominated in abundance, especially Corophium robustum Sars, 1895 which frequency of occurrence was relatively high (72 % of the total number of crustacean species). As for Annelida and Insecta larvae, they played a minor role in the formation of biomass and the number of benthic fauna. In the seasonal dynamics of total biomass and the number of benthic invertebrates there is a certain pattern: from spring to summer the quantitative indicators increase, and by autumn they decrease slightly. This is undoubtedly due to the fact that the reproduction and development of almost all forms of benthos begins in early spring, and the growth of this generation gives high biomass by august. At the same time, autumn surveys of the biomass of benthic organisms showed that in the waters of the sea around the island of Tyuleniy, the food base is not completely eaten by benthic fish. Overall, in this region the degree of security of feeding types of benthic invertebrates helps to increase the potential of population growth bentonic fish.