Temporal and spatial patterns of abundance and occurrence of planktonic shrimps in the Songkhla Lagoon System, southern Thailand

Abstract

Temporal and spatial distributions of planktonic shrimps from the hyperbenthos of Thale Sap and Thale Sap Songkhla lakes in the Songkhla Lagoon system, southern Thailand, were investigated using modified Riley push nets with a mesh size of 0.5 mm between June 2017 and June 2018. Three species of Mysida and two species of Dendrobranchiata shrimps were revealed, among which Nanomysis siamensis was dominant, representing more than 90% of the catch throughout the year. The Songkhla Lagoon system experiences extreme changes in temperature, salinity, pH, and water levels due to seasonal monsoons. A significant difference in the planktonic shrimp assemblages between Thale Sap and Thale Sap Songkhla was observed across the sampling months. Significant differences in the assemblage structure were also evident between Thale Sap and Thale Sap Songkhla and among sampling months. Dissimilar assemblage patterns were prominent temporally during the shift from southwest to northeast monsoon seasons and from the intermediate to southwest monsoon. Lake (Thale Sap or Thale Sap Songkhla) was the most important environmental parameter affecting occurrence patterns for N. siamensis, Mesopodopsis tenuipes, and Belzebub hanseni in the Songkhla Lagoon system. Salinity governed the spatial distribution of M. tenuipes and B. hanseni. Nanomysis siamensis was the only species that was regularly present in high abundance in Thale Sap and Thale Sap Songkhla over the entire salinity range. This suggest that N. siamensis is likely a resident species of the Songkhla Lagoon system.