Assessment of Crab By-catch and Species Diversity at Fish Landing Sites in the Gulf of Mannar, Tamil Nadu, India

Abstract

Indian seashores have diverse ecoregions, Tamil Nadu and Puducherry cover nearly 15% of the total coastline of India. The Gulf of Mannar region is one of the most important ecoregions spreading from north Rameswaram to south of Tuticorin, and they are categorized into the four divisions viz. Mandapam group, Keezhakarai group, Vembar group and Tuticorin group. Crabs are a mutual group of crustaceans that belong to the invertebrate animals, and systematic field assessments were conducted to document crab species at the selected fish landing center of the Tuticorin district. Completely sixteen species were noted in the study area, belonging to the seven different families and genera. In the point of family and genus Portunidae family (50 %) and 25 % Charybdis genus is highly occupying the selected studied area center. In the overall study time of all selected areas, grant total of 8774 ±119.23 numbers of crab individuals were recorded, while species-wise wise M. gladiator (1036 ± 6.61) was extremely recorded, which mostly belong to edible (81.25 %) in nature. Simpson, Shannon Weiner evenness, Brillouin, Menhinick, Margalef, and Equitability – J index showed Vellapatti, TF Harbor, and Tharuvaikulam are noted for more diversity (16 species), while the least diversity (3 species) was recorded at Punnaikayal, and some other associated animals are also noted. In focus to month-by-month basis, July was noted highest crab distribution, August had noted highest distribution of crab distribution, and in March, September, January, and February were noted to have high distribution of crab distribution. Results from the current assessment displayed that several decapod species originate from the studied area and consequently, decapod low diversity areas need conservation action to sustain decapod diversity.