Summer Mass Fish Mortality in the Kaniv Reservoir in 2019 and 2016: Comparative Analysis

Abstract

Anthropogenic impact on the Kaniv Reservoir has led to a deterioration in the quality of life of aquatic organisms due to eutrophication of water by pollution with nutrients. Fish mortality is an indicator of ecological disadvantage of the water body. A quantitative and species-based inventory control of the hydrobionts sleep along the coastline of 1000 m was made. On July 2, 2016 we discovered about 174 dead individuals among which there were 11 species of ray-finned fish and one representative of Malacostraca class (Malacostraca). Under similar conditions, on June 26, 2019 the deaths of 98 individuals were recorded. A comparative analysis of the species structure of hydrobionts and their connection to environmental factors was carried out. The most eliminated group of species were members of the perch family (Percidae). Among dead fish, they accounted for 56%, and in the group of four species, Gymnocephalus cernua (L.) was in the lead with 39%. Due to the concentration on the coastal shoal in the thicket of aquatic vegetation, Gobiidae made 25% of the dead vulnerable members of the group. The main factor in the mass fish mortality in the lower part of the Kaniv Reservoir along the coastline from the natural boundary sight “Rozhena Krynytsia” to the spot “waterway station” in a village of Buchak on July 1-3, 2016 and June 26, 2019 was a detrimental effect of the peak water temperature and its “blooming”, which developed in this chronological period. Changes in the species composition of the most vulnerable fish are due to the peculiarities of the biology identified aquatic organisms and the ecological conditions of the reservoir in these years. Among them are water temperature, mixing of its layers by wind and aeration processes on rainy days.