Influence of some environmental factors on the abundance of three commercially important bivalve species (Family: Veneridae) in the Puttalam Lagoon and Dutch Bay, Sri Lanka.
H M P KITHSIRI, M J S WIJEYARATNE and U S AMARASUNGHE
Water temperature, salinity, seagrass coverage, organic matter content in the soil and soil texture play an important role in the distribution of bivalves. The present study was carried out to determine whether these parameters significantly affect the abundance of three commercially important bivalve species viz Gaffrarium tumidum, Marcia hiantina and Marcia opima in the Puttalam lagoon and Dutch bay. The abundance of these bivalves in the Puttalam lagoon and .Dutch Bay was found to be significantly correlated with salinity (r = -0.57, p< 0.05), seagrass coverage (r = 0.89, p<0.001) organic matter content in the soil (r= 0.91 p<0.001) and soil texture. It was also found that the organic matter content in the sampling sites were highly correlated with the seagrass coverage (r = 0.90, p<0.001). Therefore, it is evident that the seagrass cover significantly affects the abundance of bivalves in the Puttalam lagoon and Dutch bay probably through enhancing the deposition of bivalve larvae inhibiting the borrowing activity of predators and increasing the productivity via increasing the organic matter content in the soil and deposition of sediments. As such it appears that in resource management the conservation of seagrass beds should get high priority and thus the operation of fishing gear that arc harmful to seagrass beds such as push nets and drag nets has to be minimized.