Age structure and sex ratio of Anodonta woodiana

ABSTRACT: Age structure, sex ratio and shell mass of a recently introduced bivalve Anodonta woodiana (Lea) were analysed in three sampling sites at its only locality in Poland – the cooling system of two power plants near Konin (C Poland). The youngest population is that in the lake Licheñskie, the oldest individual (6+) was found in the population inhabiting the warmest canal. In the material examined, the most numerous individ-uals were those aged three years (43%), followed by four years (33%) and five years old (12%) individuals. The shell mass (Sm) was positively correlated with the individual age, the highest shell mass increment being observed in specimens aged 2+, 3+ and 4+. No dependence was found between the Sm parameter and sex. The shell mass varied widely (V %> 30). The highest Sm values were found in individuals from the initial cool-ing reservoir, the lowest in those from the lake Licheñskie, the respective water temperatures during the sum-mer stagnation being 33 and 30°C. Except for the population from the lake Licheñskie, the sex ratio was 1:1