Research to assess the distribution and abundance of bottom fish in the lower reaches of the Don River

 

Currently, the Azov-Black Sea Branch of the Russian State Research Center "All-Russian Research Institute of Fisheries and Oceanography" (VNIRO) is the only scientific institution conducting comprehensive, systematic fisheries research in the Sea of ​​Azov basin and the lower reaches of the Don River. This includes the study of all commercially important aquatic bioresources and their habitats. This includes analysis of commercial catches, where branch staff work in fishing brigades, fish censuses at the fish-passing gate of the Kochetovsky hydroelectric complex, systematic sampling to assess the condition of the aquatic environment and key biocenoses in the river, work to assess the distribution and abundance of viable juvenile fish, and scientific support for fish hatcheries.

 

One of the significant expeditionary projects conducted by the branch was the assessment of the distribution and abundance of juvenile demersal fish in the lower reaches of the Don River. Based on the results obtained, it can be called a sturgeon trawl, as sturgeon are the most important bioresource in the Sea of ​​Azov, and it was these juveniles that received special attention during the expedition.

 

Specifically for this survey, branch staff designed and manufactured a new fry trawl (beam trawler), allowing for efficient operation from motorboats. The scientists surveyed the Don River from its mouth to the Kochetovsky hydroelectric complex, conducting trawl counts every 2.5 km. Sterlet and juvenile Russian sturgeon were recorded in the counted catches.

 

Considering the catches of juvenile sturgeon in Taganrog Bay and the Sea of ​​Azov, during marine expeditions by the Azov-Black Sea branch of VNIRO, it can be concluded that their migration after release from the Don Sturgeon Hatchery was quite successful. This means that the scientific scenario for restoring sturgeon populations in the Azov Basin, developed by VNIRO, will continue to be successfully implemented.

 

Anadromous sturgeon spawners have already been observed along the entire unregulated stretch of the Don River, from the delta to the Kochetovsky hydroelectric complex. Sterlet abundance has increased significantly. While 20 years ago, it was rarely encountered in the lower Don, it is now quite common, and the issue of removing the Lower Don sturgeon population from the Russian Red Book is becoming a pressing issue.

 

The expedition also revealed that gobies and whitefin gudgeon formed the bulk of the species diversity of juvenile bottom fish in the lower Don River. Juvenile pike perch, bream, and vimba were also observed.

 

The expedition research conducted by the branch staff was not limited to analyzing the distribution and abundance of juvenile bottom fish. It included a wide range of integrated scientific studies aimed at a comprehensive assessment of the aquatic ecosystem of the lower Don River. Scientists assessed the state of the river's main ecosystem communities: phytoplankton, zooplankton, and zoobenthos. They also studied the content of nutrients, heavy metals, and petroleum products in the water, determined the toxicity of water and soil, and conducted hydrological observations.

 

The results of the expeditionary research will provide a deeper understanding of the current transformations of the lower Don ecosystem and clarify possible measures for its rehabilitation and maintaining fish productivity.

 

 

VNIRO Press Service