Observations were conducted in the east of the Volga River delta and covered both the coastal areas of the eastern watercourses, including the kultuchny zone of the Belinsky Bank, and the river zone itself. During the cruise on the R/V Raskat, ichthyological and ichthyopathological work was carried out, and amateur fishermen were counted in the water area of water bodies and their banks.
Ichthyological observations included determining the species, size and weight, composition of research catches, the degree of filling of the digestive tract of predatory fish species (catfish, pike perch, asp, perch). To assess the concentrations of aquatic bioresources, 8 net sets of net orders with a mesh size of 45 to 80 mm were performed, the length of one order was 75 m, more than 300 specimens of aquatic bioresources were analyzed. The species composition included 10 species of semi-anadromous and river fish, among which the carp dominated, as in the western part of the delta, which was established in the previous research cruise. The catches of asp, white bream and crucian carp were at a relatively high level.
The linear-weight indicators of the caught fish were at the level of the latest average long-term values, which indicates the stability of the main characteristics of commercial stocks. On the positive side, it is noted that high numbers of carp are observed during the annual work, although its size is small.
During the cruise, parasitological studies of aquatic biological resources were carried out, material was collected to assess the quality of aquatic biological resources by microbiological indicators. At present, laboratory studies of the materials are ongoing.
The degree of waterlogging of water bodies and overgrowing of biotopes in summer low water conditions against the background of falling Caspian Sea levels were also assessed. At the present stage, there is an active process of moving the Volga delta islands to the south, as a result - a decrease in the productive zone of the delta front. New islands have appeared, rapid overgrowing has been noted, when communities of soft underwater vegetation are replaced by continuous reed thickets.
The results obtained will form the basis for forecasting the reserves of aquatic biological resources, assessing the state of their populations, and will be used to calculate the TAC and the recommended catch of semi-anadromous and river fish.
Press service of VNIRO