UTTAR PRADESH JOURNAL OF ZOOLOGY

This study assessed zooplankton abundance, phytoplankton density, and selected water quality parameters in active fishing and non-fishing zones off Kollam, Kerala, India. Monthly sampling was conducted from November 2019 to February 2020 in near-shore, coastal, and open-water areas. Active fishing zones were identified using the Indigenous Traditional Knowledge of local fishermen and acoustic observations from a GPS-coupled fish finder, whereas non-fishing zones were selected from adjacent waters without active fishing operations or visible fish shoals during sampling. Surface seawater samples were analysed for temperature, salinity, pH, dissolved oxygen, ammonia, nitrate, nitrite, phosphate, and silicate, and these variables were examined in relation to phytoplankton and zooplankton abundance. The observed values included temperature ranging from 25.70 to 30.50 °C, salinity from 29.67 to 34.51 ppt, dissolved oxygen from 4.28 to 6.96 mg/l, and silicate from 3.25 to 5.98 mg/l. Zooplankton abundance ranged from 422 to 503 ind. m⁻³, with the maximum value recorded in FZ-1 during November. A total of 53 zooplankton taxa were identified, with copepods forming the dominant group (35 species), followed by decapod larvae, amphipods, isopods, ostracods, chaetognaths, molluscan larvae, tintinnids, appendicularians, fish eggs, and fish larvae. Phytoplankton abundance ranged from 6815 to 10340 cells L⁻¹, with the highest value recorded in FZ-1 during December and the lowest in NFZ-2 during February. Correlation analysis indicated that phytoplankton and zooplankton abundance varied with hydrographic and nutrient conditions, although the strength and direction of associations differed between fishing and non-fishing zones. The findings provide baseline information on plankton dynamics in contrasting fishing habitats off Kollam and may support future monitoring of coastal productivity and ecosystem-based fisheries assessment.