PECULIARITIES OF STONE MOROKO (PSEUDORASBORA PARVA) DISTRIBUTION IN THE DNEPRODZERZHINSK RESERVOIR

Purpose. Study of distribution of invasive stone moroko (Pseudorasbora parva) in the Dneprodzerzhinsk reservoir depending on the biotope. Methodology. Fish were captured in the littoral zone using beach seine. Bottom substrate type and vegetation density were recorded at each sampling site. Following indices were calculated: relative fish abundance in the catch, frequency of occurrence, CPUE. ANOVA was used for finding difference among CPUE values on different substrates and vegetation densities. T-test was used for pairwise comparisons of CPUE values on different substrates and vegetation densities. Selectivity or avoidance of substrate type or vegetation density was assessed with the aid of Ivlev’s selectivity index. Association between stone moroko abundance and other fish species was tested using linear regression. Findings. Stone moroko composed 2,3 % (2011 y.) and 7,3 % (2012 y.) of catches, average frequency of occurrence ― 54,0%, mean CPUE ― 29.3 fish/100 m2. The highest abundance of stone moroko was observed on sand+shells (71,5 fish/ m2) followed by sand (42,9 fish/100 m2) and clay (3,2 fish/m2), while the lowest abundance was on stones (1,1 fish/100 m2). As for macrophytes, the highest abundance was observed on sites with medium vegetation density (52.5 fish/100 m2), while the least abundance on sites without vegetation (8,2 fish/100 m2). Stone moroko preferred sand and shells and avoided stones. It also preferred medium vegetation density and avoided dense vegetation and sites without vegetation. Originality. Selectivity of stone moroko towards bottom substrate and vegetation density in the Dneprodzerzhinsk reservoir was investigated for the first time. Practical value. Stone moroko can compete with juveniles of valuable commercial fishes and on the other hand it can play important role in diets of piscivorous fishes. Taking into account general trend for increasing vegetated areas of the Dnieper reservoirs, abundance of this species will increase further.