Nutrition of anchovy sprat Clupeonella engrauliformis in conditions of biological invasions

The reduction of desalinated buffer zones in the estuary area and the salinization of the sea, caused by the intensive drop in water levels and increased water management activities, are accompanied by a qualitative and quantitative restructuring of the trophic structure of biocenoses and change the habitat conditions of hydrobionts. In the ecological complex of the Caspian Sea, there is a reduction in the forage organisms of the slightly saline and saline water complexes, and there is a persistent dominance of marine and euryhaline species. The diet of fish is mainly formed by Azov-Black Sea invaders, in particular, by the prawn-like crustacean acartia and the larvae of barnacles. Against the background of the sea regression, observations are continued on the population structure and distribution of the comb jelly Mnemiopsis leidyi, the spontaneous invasion of which in the early 2000s undermined the food base of the Caspian sprats. The high numbers and biomass of Mnemiopsis in the first years after its introduction were a result of the absence of natural enemies. The coincidence of the migration routes of the mnemioopsis and the habitat of the anchovy-like sprat Clupeonella engrauliformis led to severe predation in the early stages of development (eggs and larvae). Based on monitoring observations, an analysis was conducted on the formation of the food base (zooplankton) and the conditions of the anchovy-like sprat’s feeding in the Middle Caspian Sea.