Abstract

Present study deals with fish diversity and physico-chemical properties of Manakudy estuary. Thirty-eight (38) species of fin and shell fishes of commercial importance were recorded during the study period (February 2010 to January 2011), higher than that of previous observations. Average fish catch in these estuary ranged from 80 to 280 kg/day, comprising mainly Etroplus suratensis (Pearl spot), Arius maculatus (Cat fish), Sillago sihama (Silver whiting), Lates calcarifer (Sea boss), Gerres abbreviatesand Chanos chanos (Milk fish). Various physico-chemical parameters and nutrients such as air temperatures, surface water temperatures, salinity, pH, turbidity, total suspended solids, dissolved oxygen, nitrite, nitrate, ammonia, total nitrogen, inorganic phosphate, total phosphorus and silicate were at the ranges of 23 to 32.5°C, 24 to 31.0°C, 7.5 to 28‰, 7.5 to 8.4, 48 to 327 NTU, 97 to 558 mg/l, 3.29 to 5.44 mg/l, 0.15 to 1.28 μmol/l, 0.61 to 6.42 μmol/l, 0.03 to 0.22 μmol/l, 7.2 to 17.6 μmol/l, 0.31 to 1.13 μmol/l, 0.74 to 4.03 μmol/l and 10.12 to 39.30 μmol/l, respectively, which were suitable for growth of flora and stocking of fish species. During the monsoon and pre-monsoon seasons, higher species diversity of fish was recorded at Manakudy estuary. Salinity appears to be a major factor influencing the abundance and diversity of fin and shell species in the estuary.

Key words: Fish diversity, Manakudy estuary, physico-chemical properties.