Natural productivity of fish ponds in relation to physico-chemical parameters at Chilya hatcher Thatta, Sindh, Pakistan

Abstract

The analysis of physico-chemical and biological parameters of two fish ponds; brooder rearing pond (Pond-1) and fry stocking pond (Pond-II), at Chilya fish hatchery were carried out during January December 2006. Ranges of temperature of water 14-35.2°C, 14.5-34.7°C; dissolved oxygen 7.69- 12.71 mg/1, 7.82-12.3 mg/l; pH 7.2-7.9, 7.87-8.4; total alkalinity 75-142 mg/l, 106-181 mg/l; total hardness 83-120, 102-189 mg/l; total dissolved solids (TDS), 270-348, 226-3920 mg/l; total nitrogen 0.15-0.47, 0.528-1.47 mg/l and orthophosphate 0.12-0.372, 0.74-1.21 mg/l respectively were recorded at the ponds. Algal flora in Pond-I consisted of 7 species of Cyanophyta, 11 species of Chlorophyta while in Pond-II 12 species of Cyanophyta, 13 species of Chlorophyta and 2 species of Bacillariophyta were found, 7 species of aquatic plants, Hydrilla verticillata, Najaz minor, Potamogeton pectinatus, Nymphia sp. Typha domingensis and Phragmites vallatorn were also recorded from pond-II. Among zooplankton the brooder pond had the population of rotifers (5 species) and micro crustaceans (3 species). In fry pond, 4 species of rotifers and 7 species of micro crustaceans were present. The results revealed that the water quality variables of Chilya fish hatchery were suitable for fish culture. No known source of pollution enters the ponds. On the northern side there is an outlet channel of Keenjhar lake which supplies water to fish ponds. Rich algal flora and zooplanktons were observed in Pond-II (fry pond). This may be due to the artificial feeding and availability of macrophytes which maintain the water temperature, light penetration, nitrates, phosphates and total dissolved solids (TDS).