Malacological survey in the Sirikit reservoir, the largest earthfilled dam in Thailand.

Ten species of freshwater molluscs were found in a malacological survey in the Sirikit reservoir in 1985. Among these species, Tricula aperta or Neotricula aperta, intermediate host of human schistosomes, Bithynia (Digoniostoma) siamensis goniomphalos and B. (D.) funiculata, the first intermediate host of Opisthorchis viverrini were not found. It is revealed that most of the habitats in the Sirikit reservoir are not suitable for the survival and colonization of molluscs. Thus few species of edible molluscs in small numbers were found, except for Limnoperna siamensis, which were found in large numbers in the reservoir. Although it is not a medically important species, their attaching in large colonies may reduce the volume of water flowing into the power tunnels and obstruct small pipe lines in the dam area. So it is recommended to further study the life cycle of L. siamensis and to determine suitable molluscicides or biological agents to be used in controlling them.