Clam population ecology in relation to environmental characteristics: A comparative assessment of Tuticorin Bay and Pazhayakayal Estuary, south-east coast of India

A study was undertaken to assess the population characteristics of clams and their relationship with physicochemical parameters in two ecosystems of Thoothukudi coast viz. Tuticorin Bay and Pazhayakayal Estuary, from July 2021 to May 2022. The study was based on monthly sampling of clam populations and associated physicochemical parameters at three stations (St. 1, St. 2 and St. 3 ) in each of the two locations. In Tuticorin Bay, the total clam density ranged from 16 (St. 3) to 148 nos. m-2 (at St. 2) with the mean density of 65±3.3 nos. m-2. Among the species, Meretix casta was dominant (33%) followed by Gafrarium pectinatum (24%), Marcia opima (22%), Paphia malabarica (21%), and Meretrix meretrix (<1%). The total clam density of Pazhayakayal Estuary ranged from 72 (St. 2) to 632 nos. m-2 (St. 3) with a mean of 311±38 nos. m-2. Both biomass and density of the clams significantly varied between the stations of Tuticorin Bay (p<0.01), whereas at Pazhayakayal Estuary, both parameters were not significantly different (p>0.05). The study further revealed that in Tuticorin Bay, characterised by fine sandy substrates (ranging from 35.01 to 81.62%) with relatively high organic carbon content (0.110 to 0.751%), supported greater species diversity but lower population density. In contrast, the Pazhayakayal Estuary, characterised by coarse sand (13.29 to 77.65%) and hyposaline conditions, supports a high population density dominated by a single species M. casta. Keywords: Bivalve, Clam density, Physicochemical parameters, Salinity, Soil texture, Species diversity