پويايي جمعيت و هم آوري توليد مثل شاه ميگوي آب شيرين (Astacus leptodactylus) در درياچه شورابيل (استان اردبيل)

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 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 1:1 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 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 17°C. Reproduction period of this species started from beginning of the December and lasted until the mid-June in Shorabil Lake.