Population dynamics of freshwater crayfish (Astacus leptodactylus) in Aras reservoir, Iran

Abstract

Aras dam is one of the important water reservoirs in Iran with a total area of nearly15000 ha. Population dynamics including length and weight composition, fecundity, sex ratio, molting time, and reproduction and capture times of freshwater crayfish (Astacus leptodactylus) of Aras reservoir was investigated during 2012-2013. The results revealed that the mean total length and weight of captured crayfish were 106.26 ± 12.89mm and 38.79 ± 15.54g, respectively. The largest crayfish had 171mm length and 216g weight. Mean number of ovarian and pleopodal eggs were 286 ± 82 and 246.31± 80.4, respectively (P≤ 0.05). In this study, male to female ratio was obtained as 1.21: 1. The male molting at 16 o C was started from late April and ended in late May, when the water temperature reached 18 o C. The second molting of males and the first molting of females occurred simultaneously at 18 o C water temperature in September. Matting of Astacus leptodactylus was started from November and continued until May. Harvesting period was from May to late November. The results showed that the number of eggs were variable (from 200 to 400 eggs) and depended on spawner size, environmental condition and available food. Besides, crayfish with higher lengths and weights had increased fecundity with a direct positive correlation. A ban on fishing during the reproduction season, use of appropriate nets and proper management should be performed to preserve the stocks of this species.