Résumé
Physico-chemical and microbial characteristics of culture water were examined during the induced breeding of Cyprinus carpio in a controlled environmental system. Water temperature, dissolved oxygen, nitrate, phosphate, pH, ammonia nitrogen, total bacterial count, hardness, salinity, carbonate and bicarbonate were estimated before and after spawning and hatching. Average alteration in water pH before and after spawning was 7.91-7.57 and 7.86-7.58 respectively. Total hardness, carbonate and bicarbonate showed insignificant variations. Nitrate, ammonia nitrogen and phosphate contents significantly increased after spawning and hatching p<0.05. The average increase in nitrate was from 2.94 to 8.62 /g l-1 after spawning and 3.10 to 8.49 /g l-1 after hatching. Ammonia nitrogen contents were sharply increased from an average of 0.011 to 1.87 mg l-1 after spawning and 0.013 to 0.56 mg l-1 after hatching. The average phosphates increased from 2.59 to 4.15 /g l-1 after spawning and 2.61 to 4.03 /g l-1after hatching. Dissolved oxygen was sharply depleted even after a continuous aeration. Temperature played a vital role during breeding. No successful breeding was observed at a temperature of 17oC or below and 31oC or above. There is a significant association between temperature, spawning and hatching (p<0.05). By optimizing temperature, the breeding success of this carp was achieved with a statistical significance of p<0.05. Total bacterial count was significantly increased after spawning and hatching. It was related to the amount of discharge and may cause mass mortality of fish embryo and spawn in a closed hatchery system.