Hydrological conditions of phytophilic fish reproduction in the Lower Don River under the influence of climate change and flow regulation

Despite the significant role that the Lower Don plays in Russia’s fishing industry, the region’s fisheries remain in a depressed state. It is well understood that the Tsimlyansk reservoir impacts the region’s fisheries, but the potential influence of climate change and associated reductions in snowmelt water flow remains under debate. The present study provides the first investigation of the effects of reservoir management and reduction in snowmelt water flow due to global warming on fish spawning independently. Using estimates of water discharge in the lower reaches of the Don, in the absence of the Tsimlyansk reservoir, the results showed that climate-related factors, although still significant, had a smaller effect on water discharge, compared with reservoir management regimes. Hydrological characteristics affecting fish reproduction (i.e., water discharge, water level, area and duration of floodplain inundation, and fingerling abundance) are decreasing under the reservoir influence by a factor of 1.5–3.2, while the declines associated with climate change are a factor of 1.4–2.1. Artificial fish reproduction and improvements in management of the Tsimlyansk reservoir could lead to restoration of fish stocks in the Lower Don.