The article is focused on the current state of biodiversity in the aquatic environment of the Utrish Nature Reserve. Implementation of the multi-level monitoring program for fish and crustacean fauna, conducted in the waters of the Utrish Nature Reserve during the period 2016-2018, using classical methods of biological analysis, as well as visual underwater fish counting, allowed us to assess the overall state of biodiversity in this area as sufficiently stable. The population status of the model indicator species, the European black scorpionfish