THE EFFECT OF STOCKING RATE ON WATER QUALITY, SOIL CHEMISTRY AND FISH PRODUCTION

Monoculture system was carried out in common carp ponds treat­ed with chemical fertilizers (urea-superphosphate) plus supplemental feed (1796 protein). Effect of three stocking rates 2100, 4200 and 6300 fish/feddan were tested on water quality, soil chemistry and fish production from 12 April to 4th November 1992, in 9 earthen ponds lo­cated in the experimental unit at Cental Laboratory for Aquaculture. At the highest stocking rate (630❑ fish/ feddan), organic matter accumulated reduced concentration of dissolved oxygen, increased chemical oxygen demand (COD) and concentration of ammonia-nitrogen. Slight differences in pH and orthophosphate-phosphorus in pond soil were realized in all treatments. Fish production increased and average in­dividual fish weight decreased with increasing stocking density.