Investigation of the factors that influence on the distribution of mollusc, Faunus sp. (Mollusca: Gastropoda: Thiaridae) along the Lunuwila Ela, Galle

Factors that affect on the distribution of mollusc, Faunus species along the Lunuwila Ela, Galle was determined using ten environmental parameters. Four sites including 16 replicates were used and data were collected for six months. Among ten environmental parameters investigated, six of them are significantly different among sites. According to the results of regression analysis, none of the physiochemical parameters is responsible for the distribution of this species along this stream. However, it indicates, contents of the substrate make a favorable contribution on their distribution pattern which highest abundance of Faunas species recorded from the substrate with fine sand, silt and clay.