DIVERSITY OF BRACHYURAN CRABS IN AYIRAMTHENGU MANGROVE; A PART OF KAYAMKULAM BACKWATER, KERALA, INDIA

Mangroves in the estuarine ecosystem play important roles in biodiversity maintenance, energy flow and provide a home and feeding ground for a wide range of species. Brachyuran crabs are ecologically important and considered as inevitable part mangrove ecosystem. Here we investigates the present status of brachyuran crab diversity and seasonal variation in their distribution and abundance in the Ayiramthengu mangrove; a part Kayamkulam backwater during February 2017- January 2018. In total 1364 individuals were encountered, comprising 13 species of brachyuran crabs belonging to 4 family and 8 genera. 5 species of Portunid crab belonging to 4 genera, 5 species of Grapsid crab, 1 species of Sesarmid crab and 2 species of Ocypodi crabs were identified up to species level. The species diversity was high during monsoon (43%) followed by post monsoon (35%) and pre monsoon (22%). Salinity may be the reason for the difference in the diversity of crabs in various seasons. The calculated values of various diversity indices included Shannon–Wiener diversity (H’) ranged from 1.922 to 2.355, Margalef’s species richness (d) ranged from 1.048 to 1.886, Dominance Index (D) ranged from 0.1038 to 0.1497. Conservation strategies are required for the protection of Ayiramthengu region in general.