The influence of the level regime of the Ivankovo reservoir (Middle Volga) on the state of stocks and fishing of fish living in it

The article analyzes the dynamics of the water level and water content of the Ivankovo reservoir for the period from 1951 to 2022 and their impact on commercial fish stocks. It has been established that the reservoir is characterized by high interannual variability of water content and significant fluctuations in water level, especially during the spawning period. A decrease in stocks of most fish species was revealed in the early 2000s, with subsequent stabilization and partial recovery to date. There was a negative correlation between the water level response and fish stocks in the period from 1999 to 2007, which changed to a positive correlation after the closure of the fishery in 2007. It is assumed that the decrease in the maximum water level utilization in recent years, associated with a change in the reservoir regulation regime, contributes to the restoration of the number of some fish species. In general, the water level regulation regime in the Ivankovo reservoir has a significant impact on the state of its ecosystem and requires further study to develop optimal measures for the conservation and rational use of fish resources.