Abstract

Caspiastacus pachypus, a brightly coloured representative of the Astacidae, inhabits the Caspian Sea, the River Don and the Dnieper-Bug Lagoon of the Azov-Black Sea Basin. It prefers a stone-covered bottom at depths of 5-50 m and water with a salinity of 12-14 ppt, a temperature of 8-21°C and an oxygen content of more than 6.1 mg/l (85% of saturation). Animal food prevails in the crayfish’s diet amounting to 92% and 86% of the total food consumed in the sea and the Don. The highest coefficient of filling of the stomach (2.77%) has been observed in the sea. The biotopes of C. pachypus are confined to areas with a high benthic biomass (500-1000 g/m² in the sea and 200 g/m² in the Don). The crayfish mature in the third year of life. The population consists of 8 or 9 age-groups. The 7.1-9 cm long crayfish are predominant in the sea (54.12%). In the Don they represent only 28%; there the 2+ year old juveniles (33%) are more abundant. C. pachypus is not large (with a length of 9.6 cm and a weight of 32.4 g), however, the weight of the claws amounts to 47% and 54% of the total biomass of females and males, respectively. In the sea a higher abundance of the crayfish was observed every 3rd year increasing to 14 million specimens compared to 1.5 million in non-productive years.

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