The article considers studying the physiological and biochemical parameters of the common sprat (Clupeonella delicatula caspia Svetovidov) taken in the western part of the Middle Caspian Sea at different periods of the annual cycle. There were studied the species in the pre-spawning state, at the beginning of spawning, at the feeding stage and at the pre-wintering stage. In fish muscle tissue the content of water-soluble protein and total lipids was determined. In the pre-spawning period, in male common sprat was recorded a positive correlation (p < 0.05) between the weight of fishes, fishing length and content of total lipids in muscles (r = +0.5206) and (r = +0.5039), respectively. In females no statistically significant dependence of the size-weight parameters and lipid content in muscles were recorded, which is probably due to the fact that lipids in their bodies were spent for energy needs, and to a greater extent than in males - for the generative function. In a comparative aspect, in the muscles of males and females no significant differences in the content of total lipids and water-soluble protein in the pre-spawning period were found. At the stage of the beginning of spawning, a decrease in total lipids and water-soluble protein was noted in the muscle tissue of the studied fishes, which is associated with an increase in energy consumption for sweeping out sexual products. During the feeding period the common sprat was characterized by an intensive accumulation of lipid reserves; the content of total lipids and water-soluble protein in the muscles increased with increasing length of individuals. In the pre-winter period stabilization of muscle lipid and increase in protein reserves were recorded, which is necessary for fish to ensure a normal existence in the subsequent stages of the annual cycle.

The fishing and biological characteristics of the common sprat (Clupeonella cultriventris caspia Svetovidov, 1941), caught along the coast of the Caspian Sea in the area of Makhachkala, the Republic of Dagestan, were obtained. Examination of the fish showed that the individuals were in a spawning state. In the muscles, the content of the main reserve and energy substances of the body — total lipids and water-soluble protein — was studied. A significant (p < 0.05) positive correlation was registered in females and males between fish weight and fishing length: (r = +0.87) and (r = +0.85), respectively. The physiological state of the common sprat in terms of the content of total lipids and water-soluble protein in the muscle tissue is satisfactory. The tendency of the highest content of total lipids in the muscles of females compared to males was registered, since individuals need a larger energy reserve to ensure oogenesis than for spermatogenesis. This is due to the use of muscle lipids to build the gonads and supply with the necessary nutrients for the embryo, and later the larva. In a comparative aspect, there were no significant differences in the content of water-soluble protein in the muscles of males and females during the spawning period. Analysis of the coastal fishery for common sprat with fixed seines in the period 2011–2021 showed that its catch on the Dagestan coast of the Caspian Sea increased from 302.7 tons in 2012 to 1815.0 tons in 2021, which was in direct proportion to the number of fixed seines. In this regard, the most actual task is the development of fishing reserves of this species, which will contribute to the development of the fish extraction and fish processing industry of the Republic of Dagestan.