Research on water quality of ponds for Siniperca chuatsi and bait fish in hot season

In hot and rainy seasons, we investigated the disease incidence, drug use and water quality of 6 ponds for Siniperca chuatsi and bait fish in the breeding base in Qingyuan, Guangdong province. The results suggest that hemorrhage of S.chuatsi easily relapses by adding antibacterial drugs, but not by adding both antibacterial drugs and drugs which enhance immunity and reduce stress behaviors. During the incubation period, the concentration of ammonia nitrogen is always higher than 1.0 mg.L-1, and that of nitrite nitrogen is higher than 0.18 mg.L-1; N/P ratio is relatively high sometimes, and the concentration of nitrate nitrogen in 6 survey ponds gradually decrease along with culturing time. Thus, high concentration of ammonia nitrogen and nitrite nitrogen indicates bacterial diseases of S.chuatsi may occur soon. To solve this, plants such as duckweed may be grown to absorb the excess ammonia nitrogen; aerator may be applied to maintain high dissolved oxygen to reduce the concentration of nitrite nitrogen; drugs may be added to reduce stress behaviors of animals. To avoid high N/P ratio, appropriate addition of phosphate may regulate the water quality.