Abstract:
Ecological and fishery surveys in Sirikit Reservoir were conducted during dry and wet season in 1985. The annual ranges of water quality parameters were : temperature 30.0 30.5 ̊C, Secchi disc transparency 60 146.3 cm., pH 6.75 7.35, D.O. 7.43 7.80 mg/1, CO2 3.04 4.50 mg/1, Alkalinity 67.0 76.0 mg/1, Hardness 66.0 67.5 mg/1, Phosphate-P 0.43 0.49 mg/1, Ammonia-N 0.0125 mg/1, Nitrite-N 0.010 0.0125, Nitrate-N 2.22 2.28 mg/1 and Conductivity 200 217.5 µS/cm. There were 5 groups of phytoplankton and 3 groups of zooplankton found in this survey. Seasonal changes of the plankton populations showed the density at 533.71 x 103 cell/m3. In dry season and 1,512.95 x 103 cell/m3. In wet season. There were 2 genus of freshwater zoobenthos, which were : Limnoperna siamensis and Chironomus sp. with the average density of 53 No./m2. Aquatic macrophytes, Eichornia crassipes, was observed in this survey. There were 32 species of freshwater fish and one species of prawn found in this survey. The fish standing crop estimated by spot poisoning were 12.83 kg/rai in dry season and 13.89 kg/rai in wet season. There were 4 groups of fish populations which composed of carps at 12.83-19.93%, catfishes 13.15-36.90%, murrels 0-1.85% and miscellaneous species 50.27-65.08% . The forage to carnivorous species (F/C) ratio ranged between 1.04 : 1- 1.41 : 1