A study on variations in physico-chemical and microbial factors of water during induced breeding of catla catla in a closed hatchery system

Abstract

In the present study, we examined the variations in physico-chemical and microbial factors during the induced breeding of Catla catla in a controlled environmental system. The physico-chemical parameters such as water temperature, pH, dissolved oxygen, ammonia nitrogen, nitrate and phosphate were estimated before and after spawning and hatching. An average variation in water pH before and after spawning and hatching was 7.9 – 7.57 and 7.9 – 7.63 respectively. Dissolved oxygen was depleted from an average of 4.38mg L^-1 to1.74 mgL^-1 after spawning and 4.44mgL^-1 to 2.11mg L^-1 after hatching. Ammonia nitrogen, nitrate and phosphate contents signifi- cantly increased after spawning and hatching (p< 0.05). Total bacterial count was significantly (at p< 0.05) in- creased after spawning and hatching. The mean value of the bacterial count in the water of breeding pool was 33.5x10² colonies ml^-1, which rose to 988.8x10² colonies ml^-1 after spawning of the fish. The mean value of the bacterial count in the water of hatching unit was 41.6x10² colonies ml^-1, after hatching number of bacterial colo- nies rose to a mean level of 889.0, 10² colonies ml^-1. It was related to the amount of discharge and may cause mass mortality of fish embryo and spawn in a closed hatchery system.