The article is devoted to the study of biological characteristics of the north Caspian roach of the Daghestan coast of the Caspian Sea. Discussed are size and weight, fatness, passing the stage of gonad maturity, the absolute individual fecundity and feeding habits. The degree of occurrence of organisms in the food lumps with identification of dominant groups is determined.

A high variyety of vegetation and a predominance of small cell forms are typical of the current structure of the phytoplankton of the seacoastal shallow waters of the Russian coastline of the Caspian Sea. The replacement of the dominating complex and the size groups of the phytoplankton has occurred. The phytoplankton community is represented by six categories: Cyanophyta, Bacillariaphyta, Dinophita, Euglenophyta, Chlorophyta, and the small flagellates. The basis of the taxonomic variety consists of the Diatoms algae. The composition of species of the phytoplankton of the sea coastal shallow waters of the Russian water area of the Middle Caspian is in a dynamic state and depends on the direction of the change of water regime.

The latitudinal variability of the linear and allometric growth of didacna has been revealed. The tendencies of increase in the increments and the elongation coefficient with approach to the optimal conditions in temperature and soil have been found, herewith the convexity coefficient decreases. The life span of didacna is inversely proportional to the growth rate.

The article presents the results of studies of feeding characteristics of such cyprinid fish species as the roach Rutilus rutilus caspius (Jakowlev, 1870) and the bream Abramis brama (Linnaeus, 1758) in various parts of the Daghestan coast of the Caspian Sea. The material was sampled along the entire Daghestan coast of the Caspian Sea, from the Kizlyar Bay to the mouth of the Samur river, in different biological seasons in the period of 2017–2018.

Anthropogenic transformation of the Caspian Sea biocenoses results in the loss of their uniqueness and decrease of their biodiversity. In recent years the main role in the formation of biomass has played the autoacclimatizant mollusks Abra ovata , Mytilaster lineatus and Cerastoderma glaucum which dominate the biocenoses of the Caspian sea and are the main food components of valuable commercial benthivorous fishes. In 2018 live specimens of Corbicula fluminalis (O. F. Muller, 1774), a new species of bivalve mollusks for the Russian sector of the Caspian sea and the entire European part of Russia, were first discovered on the Daghestan coast.