Biological Aspects of Mud Crab in South-West Region in Bangladesh

Abstract

The present study was conducted to obtain an idea on the taxonomy and other biological aspects like gonadosomatic index, alimentosomatic index, condition factor, food and feeding habit of mud crab during December 2013 to March 2014. Total 60 live specimens were assayed during the study period. Of them, 30 specimens were collected from sundarban mangrove forest and 30 from gher.The body of mud crab was dorso-ventally flattened, broader than long. The body was composed of 3 parts (head, thorax, and abdomen). Cephalo-thorax was covered by a calcareous exoskeletal structure known as carapace. Male was larger than female. The shell colour varied from a blackish or reddish brown to light black.The taxonomical study showed that body weight, carapace Length, carapace Width, gonad weight, gut weight in sundarban mangrove forest ranged from 63 - 126.2g, 5.1 - 6.3 cm, 7.1- 8.6 cm, 1.6 - 2.6 g, 0.5 -1.4 g respectively. Body weight, carapace length, carapace width, gonad weight, gut weight in gher ranged from 42.10-124.50g, 4.20-6.30 cm, 6.10-8.80 cm, 1.70-2.30 g and 0.50-1.40 g. The gonadosomatic index of Mud crab specimens ranged from 2.31 to 4.22.Mean alimentosomatic Index of all samples was found 1.11± 0.24 and ranged from 0.73 to 2.22. The condition factor of Mud crab specimens ranged from 34.19 to 66.96.Relationships between different variables were found to be linear. Present investigation also showed the food and feeding habit of mud crab both in wild and sundarban mangrove forest. The blue green algae, unicellular and filamentous algae, diatoms, rotifer, copepods, decayed organic matter etc. were the main food items of mud crab. It indicated that the species is omnivorous in its feeding habits. The mean values alimentosomatic indices indicated feeding intensity in mud crab during the investigation period.The mud crab is a common and valuable species of Bangladesh.Very little detail work has been reported on the taxonomy and other biological aspects of this species. Detailed investigations on important aspects like taxonomy, biological characters and food and feeding habit in order to evaluate their utility in aquaculture are very meager.This study thus can be treated as an attempt for contribution of some information to this direction.