FISHERIES PART-3 скачать в хорошем качестве

FISHERIES PART-3

Story Hatchery Catla Catla, Catla fish breeding efficiency/ Catla, the fastest growing Indian major carp (grows to 1.0-1.5 kg/yr), constitutes an integral component of carp polyculture system in the country. Matures in the second year of its life and breeds only in flowing rivers and streams during monsoon (May to September). Two to three-year class brooders are raised in the earthen pond(s) at a biomass of 1,500-2,000 kg/ha along with other Indian major carps. Brooders are induced by injecting either pituitary extract or commercial hormones, viz. Ovaprim, Ovatide, Gonopro FH etc. In case of pituitary extract, the females are given two doses of injection of 2-3 mg/kg and 4-6 mg/kg at an interval of 6-8 h, whereas males are given single dose of 2-3 mg/kg. However, with commercial hormone, single dose of 0.4-0.5 ml/kg to female and 0.2-0.3 ml/kg to male, is given. In the present practice of induced breeding in circular echo-hatchery, the ratio of female to male is maintained at 1:1. The injected broods are released in breeding pool. Spawning occurs after 6-8 h of injection. In general, 1.0-1.5 lakh eggs/kg female are obtained and fertilization levels remain over 90%. Eggs are shifted to a hatching tank, where they are kept in floating condition with appropriate water circulation. Hatching occurs within 18-22 h at 27-28°C with 80-95% success. The hatchlings are kept in the same hatching tank for another two days without feeding, as their yolk-sac remains up to 72 h. These free-swimming hatchlings, commonly known as spawn, grow to a size of about 5-6 mm when they are shifted to the nursery. The spawn are reared in earthen nursery ponds and concrete tanks at stocking densities of 3-5 million/ha and 8-10 million/ha for 15-20 days during which they grow to an average fry size of 25 mm with survival rates of 30-35% and 50-60%, respectively