Factors influencing the distribution of Mysids (Crustacea: Mysida) in the Negombo lagoon, Sri Lanka

Mysids are minute crustaceans that occur in large numbers in estuarine waters. Their significant role as a main food source for fish populations is becoming apparent. There is currently, limited information on mysids in Sri Lankan estuarine waters. The present study investigated the distribution of mysids in the Negombo Lagoon from June 2012 to May 2013 at 18 randomly selected- sites along the lagoon. Surveys were conducted along the boundary of the lagoon, during day time, using a dip net (opening of 25 × 20 cm²) with 500 μm mesh size. The spatial distribution survey recorded 11 mysid habitats. Mesopodopsis zeylanica, and a potentially new Siriella sp. were identified, M. zeylanica being the most abundant species. Survey of temporal variation in mysid abundance was also carried out at two sites for a six-month period. Mysid species did not show any temporal variation and the distribution and abundance was not affected by any single environmental factor. The spatial distribution of mysids along the lagoon boundary was found to depend mainly on the estuarine boundary conditions. Mangrove vegetation along the estuarine boundary was found to be favorable for mysids while concrete boundaries and accumulation of garbage along boundaries were found to be unsuitable.