Degree-hours to spawning response, fertilization rate and hatching of Labeo rohita and Cirrhinus mrigala through induced breeding under hatchery environment.

Major carp is a group of fish species commonly cultured in Indian Subcontinent. Fish is the major source of protein, omega-3 fatty acids, vitamins and minerals. With the robust increase in human population, the demand of food is also increasing. To overcome the food, demand many food sectors are working in line to cope with the protein requirements management of brood stock and successful breeding is also very important. Estimation of degree-hours for the spawning response, hatching of brood stock and their fertilization rate, hatching rate of fish eggs is one of the major aspects of hatchery management. Degree-hours is a standard unit that is used to measure the heat requirement for spawning and hatching while data is scarce for many species. The current study was designed to investigate the degree-hours to spawning and hatching for major carps i.e., Rohu (Labeo rohita) and Mrigala (Cirrhinus mrigala) during May to August 2022 at Punjab Fish Seed Hatchery, Rawal Town Islamabad, Pakistan. Two triplets (one male and two females) of each species were selected for induced breeding. Ovaprim was administrated at the rate of 0.5ml/kg for female and 0.2ml/kg for male to stimulate ovulation and spermitation respectively. Both species showed ovulation rate (100%). Spawning was occurred after 9.35±0.4299 hours in Rohu and in Mrigala 10.18±0.4393 hours at average water temperature of 26.3±0.575. Degree-hours to spawning in Rohu and Mrigala were calculated as 248.6±9.35 and 264.6±5.625 respectively. Higher fertilization rate (87.23±2.029%) and hatching rate (84.88±1.7747%) were observed in Mrigala (Cirrhinus mrigala) as compared to Rohu (Labeo rohita) i.e. (85.75±1.856%) and (81.75±1.525%) respectively. Hatching activity proceeded rapidly in Rohu and completed in 741.025±14.532 degree-hours while, in Mrigala it occurred in 778.43±9.1972 degree-hours. This was a first documented report on effect of degree-hours on induced breeding of indigenous carps of Pakistan i.e., Rohu and Mrigala under controlled hatchery environment.