Seasonal variation in the abundance and species diversity of penaeid shrimps from the coastal area of Sonmiani Bay Lagoon, Balochistan, Pakistan

Shrimp communities of the coastal habitat of the Sonmiani Lagoon were shown to be dominated by family Penaeidae. Seasonal variation in the relative abundance and species diversity of penaeid shrimps was derived from sampling of 2554 individuals representing twelve species of three genera. The results showed that species of the genus Penaeus dominated over those of the other two genera of penaeid shrimps i.e. Metapenaeus and Parapenaeopsis. The most abundant species of penaeid shrimps were Penaeus indicus (67.50 %), Metapenaeus affinis (13.31 %), Penaeus merguiensis (12.02 %), Metapenaeus brevicornis (4.26 %) and Metapenaeus stebbingi (1.60 %), respectively. Relative abundance varied seasonally within the species and between the seasons. Highest species richness in the lagoon was observed in the period of SW monsoon and the lowest in pre-monsoon season, whereas Diversity (H') was found to be highest in post-monsoon, and appeared to be influenced by the equitability (J) of distribution of individuals among the species. Temperature, salinity and pH influenced both the abundance and the diversity of shrimp fauna in the lagoon