Seasonal variation of zooplankton and pelagic fish catch in the fishing grounds off Tiruchendur coast, Gulf of Mannar, India

The present study on zooplankton species diversity, abundance and water quality parameters with special emphasis on pelagic fish catches in three fishing grounds off Tiruchendur coast was conducted from January 2009 to December 2010. As zooplankton are playing important roles in transfer of energy to the pelagic food webs, an attempt was made to understand the role of zooplankton on pelagic fish catch in the potential fishing grounds. Stations 1–3 are located about 3.7 km, 14.1 km and 17.3 km from the Tiruchendur coast respectively. Sea surface temperature (SST) in three stations varied from 25.0 to 31.7 °C and minimum and maximum SST recorded unifromly in monsoon and summer seasons. Dissolved oxygen and salinity varied from 4.15 to 6.2 mg/l and from 33 to 36.3 PSU respectively. Total of 49 species of zooplankton have been documented during the study. Zooplankton diversity was significantly differed from seasons to seasons. Calanoid and larvae of crustacean's crabs were dominant group in three stations and significantly contributing to the pelagic fishery. High and low population density recorded during summer months and monsoon season respectively. The statistical analyses showed that, physical parameters significantly (positive) correlated with zooplankton abundance; however, chemical parameters exhibited significant negative correlation with zooplankton density in stations 1 and 2. Among the pelagic fishes, Sardinella longiceps and Scomberomorus commerson are the dominant species in the study. The high rate of zooplankton population density and maximum pelagic fish catch were inconsistent due to lacking period between spawning and fish catch.