The State of the Fish Population in the Open Part of the Volga Reservoirs during the Period from the 1980s to the 2010s

The data of fisheries statistics and the results of acoustic trawl surveys conducted from the Ivankovo Reservoir to the Volgograd Reservoir from the 1980s to the 2020s were compared. It is shown that the dynamics of the qualitative and quantitative parameters of commercial and research catches has similar trends. Over the study period, the annual commercial catches of fish and catches of the most commercially valuable species decreased in most reservoirs of the Volga cascade. At the same time, the role of species the proportions of which in commercial catches reached only a few percent in the 1980s has increased. The species diversity of catches has also changed due to these species. The same trends were observed in research catches. The results of the sonar survey indicate a decrease in the ichthyomass in the reservoirs. The exceptions were the Ivankovo and Uglich reservoirs, where industrial fishing was banned in 2014 and 2007, respectively. As a result, in the early 2010s, not only the total catches and ichthyomass of the fish population, but also the proportion of the most commercially valuable species in catches increased in both reservoirs. However, the recent data have shown that by the 2020s, there were common trends with other reservoirs towards a decrease in research catches in these reservoirs. This indicates that the decrease in these parameters in the other Volga reservoirs is due to excessive legal and illegal commercial fishing in the 1990s–2000s.