Seasonal Variation of Zebra Mussel (Dreissena polymorpha Pallas, 1771) Colonization on Turkish Narrow-Clawed Crayfish (Astacus leptodactylus Eschscholtz, 1823) in Lake Eğirdir, Turkey

In this study, the hosting status of Astacus leptodactylus, which has one of the highest economic value of the inland waters fisheries of Turkey, dependent on zebra mussels (Dreissena polymorpha) was studied. Seasonal and sexual differences of zebra mussel prevalence, density situation on crayfish and some morphometric properties of zebra mussels retrieved from host were determined. Field works were carried out in January, April, July and October of 2015 with 8 fishing operations. 200 fyke net with different mesh sizes were used in sampling process. Sex of the crayfish and if they have mussels on them were determined by organoleptic observation. Mann-Whitney U, Kruskal Wallis and Chi-Square tests were used for evaluating of nonparametric data. A total of 4024 crayfish were caught and D. polymorpha was determined on 624 of them. The annual prevalence was found as 15.51% for both sex groups and it is higher in female (19.81%) than in males (9.82%). The highest mean abundance was found to be 1.93 in the spring season. The mean weights of the mussels were 0.2277 g and the average shell size was 12.3802 mm indicating a strong exponential relationship between weight and shell size.