Abstract

CRABS DIVERSITY AND DISTRIBUTION OF MANAKUDY MANGROVES, KANYAKUMARI DISTRICT, TAMILNADU SOUTHWEST COAST OF INDIA IN RELATION TO ENVIRONMENTAL VARIABLES

V. Ramamurthy* and R. L. Abhinand

Abstract

The macro benthic faunal composition in the mangrove forest is diverse. Fish are the most dominant species in many mangrove forests which constitute about 80% of the macro faunal biomass. Fish appear as the most important group of mangrove epifauna. Their distribution seems influenced by some biotic and abiotic parameters. To verify the interactions between crab populations and relevant environmental physico-chemical parameters of the water and soil. Among the different ecosystems of mangrove crab diversity, density and richness were the highest dominance index at Manakudy mangrove community. The similarities among the crabs at different water parameters were determined using correlation coefficient. The diversity of crabs the total number of 16 species belonging to 12 families have been identified at the study area. The presence of species like Portunus pelagicus, Macrophythalmus dilates, Scylla serrata and Sesarma plicatum is an indicator of the productive well being of mangrove ecosystem especially with Portunus pelagicus which occurs only in mangrove waters. The species density was high during monsoon and post monsoon periods and low during summer and pre monsoon periods. Seasonal variation of environmental variables was observed, with high Air temperature, water temperature, salinity and Biological oxygen demand from summer season, whereas high Dissolved oxygen, nutrients like nitrate and nitrite from monsoon season. Crabs species richness (13), density (0.6±0.2) and diversity (0.08±0.02) were recorded higher during monsoon season. In general high fish species diversity was recorded during post monsoon season. Water temperature and salinity were best influencing the fish assemblage of mangroves. The study depicted Manakudy mangrove habitat was endowed with diverse crabs which were significantly influenced by environmental variables. Thus it is recommended that the habitat to be utilized with proper planning for better conservation and sustainable fishery potential. This baseline ecological study of crab mangroves is important for monitoring, management and conservation of mangrove ecosystems.

Keywords: Diversity, density, richness of Crabs, water analysis, Manakudy mangrove.