POPULATION DYNAMICS AND REPRODUCTIVE BIOLOGY OF CRAYFISH (ASTACUS LEPTODACTYLUS ESCHSCHOLTZ, 1823) IN SHORABIL LAKE (ARDABIL PROVINCE), NORTHWEST OF IRAN

Freshwater crayfish (Astacus leptodactylus Eschscholtz, 1823) is a very valuable macrobentic organism which was introduced Aras reservoir to the Shorabil Kake in the amount of 15000 specimens during the years 2002-2006. This species produce very good population in the Shorabil Lake. We investigate biological, biomass and MSY of the crayfish in the Lake during the years 2006-2007.
Results showed that the mean total lengths and weight of this crayfish for both sexes were 82. 5±32. 4mmand 82. 5±32. 4g, respectively. Maximum total length and weight of the caught crayfish was 196mm and 328g respectively. The sex ratios of male: female crayfish caught with a funnel trap of 10mm mesh size (stretched mesh) were estimated at 1:2. 4 that was significantly difference from 1:1 ratio (X2= 479. 01; P<0. 05). Mean number of ovarian and pleopodal eggs were estimated at 396. 6±36. 5 and 311. 11±22. 92 eggs with 95% confidence limits, respectively.
The time of the first molting of the male stared from beginning of the May at a water temperature of around 14oC and ended in mid-June. The second molting of the male and the first molting of the female is done simultaneously and started in beginning of the October at a water temperature of around 17oC. Reproduction period of this species started from beginning of the December and lasted until the mid-June in Shorabil Lake.