VARIATIONS IN ABIOTIC AND MICROBIAL PARAMETERS DURING BREEDING OF CIRRHINUS MRIGALA IN A CLOSED HATCHERY SYSTEMDevendra Mohan, Devendra Choudhary, Ramkishor and Archana Gaur
Some of the abiotic and microbial characteristics of culture water were examined during the breeding of Cirrhinus mrigala in a closed hatchery system. Water temperature, dissolved oxygen, nitrate, pH, hardness, salinity, free CO2, bicarbonate and total bacterial count were estimated during spawning and hatching of Cirrhinus mrigala. Temperature and dissolved oxygen were found as vital limiting factors for fish spawning and hatching. With in the optimum thermal range the spawning and hatching time is inversely proportional to decreasing temperature. Higher level of dissolved oxygen is essential for a successful breeding, while lower dissolved oxygen leads to defective larval and increased mortality of embryo and hatchling. Dissolved oxygen was found sharply decreased from 4.90 mg/L to 2.39 mg/L after spawning and 4.67 mg/L to 2.96 mg/L after hatching. An insignificant decrease in pH was recorded while hardness showed insignificant increase. Average nitrate contents were found increased from 2.53 μg/L to 7.71 μg/L after spawning and 2.64 u/gl to 5.41 μg/L after hatching, similarly Phosphate contents were increased from an average of 2.39 μg/L to 3.86 μg/L after spawning and 2.55 μg/L to 3.32 μg/L after hatching. Insignificant variations in Bicarbonate and free Co2 were recorded. Bacterial count sharply increases after spawning and hatching and may be a cause of mass mortality of embryo and spawn in a closed hatchery system. By regulating some of these factors the breeding success in closed hatchery system may be increased.
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