Taxonomy and Diversity of Marine Brachyuran Crabs of Cochin Region

Abstract- Brachyuran crabs, one of the diverse group under decapoda has a significant role in aquatic ecosystems as well as in exploited marine fishery. Present study deals with the taxonomy and diversity of brachyuran crab landing of Cochin region. Weekly sampling was carried out for a period of 11 months between August 2015 to June 2016. Two important fishing harbour of Cochin, viz Thoppumbady and Munambam fisheries harbour were selected for study. Higher number of trawlers operating from the Cochin region coupled with better facilities for marketing and discarding of by- catch result in landing of more quantity of trawl catch in the harbour which in turn contribute to increased richness and diversity of brachyuran crab. During the present study 29 species of brachyuran crabs belonging to 17 genera and 9 families were identified, this also included four commercially exploited species such as Portunus sanguinolentus, Portunus pelagicus, Charybdis feriatus, Charybdis lucifera belonging to the family Portunidae. Both juveniles and adult crabs were observed in the landing. Fluctuation in the species composition was observed, higher species diversity was seen during the month of January compared to August. Fewer representation of lesser known varieties of crab could be due to the fact that most of the catch were either discarded at sea, soon after sorting and only larger crab with commercial important alone were brought to the harbour.

The results confirm that the trawl catch of Kerala coast harbours rich diversity of brachyuran crabs. High diversity of the Brachyuran crabs reported from the study area shows that commercially important crab species are abundant in this region. So like shrimp fishery, crab target fishery also can increase the catch through which the contribution of crabs in the crustacean fishery can be maximized.