Population dynamics and reproductive biology of crayfish (Astacus leptodactylus Eschscholtz, 1823) in Shorabil Lake (Ardabil Province), northwest of Iran

Freshwater crayfish (Astacus leptodaciylus 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 sexeswere 82.5±32.4mm and 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 ratio ( X2 = 479.01 ; P<0.05 ). Mean number of ovarian and pleopodal eggs were estimated at 396.6136.5 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 14°C 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 I 7°C. Reproduction period of this species started from beginning of the December and lasted until the mid-June in Shorabil Lake