| Popis: |
An attempt was made to develop broods of Thai Pangas, Pangasianodon hypophthalmus earlier than normal spawning season using Green House (GP) Technique during July, 2015 to June, 2020. The study was conducted in four earthen ponds of 0.08 ha each. For Green House technique, two ponds were covered fully with transparent polyethylene sheet fastened in frame, made of bamboo to receive sunlight for increasing water temperature. The other two ponds were kept open and were treated as open pond (CP) as control. Ponds were treated with lime (CaO) @ 250 kg/ha and then filled up with water up to a depth of 1.5 m. Before stocking, ponds were treated with dolomite @ 20 ppm and fertilizer with urea @ 2.5 ppm and TSP @ 1.00 ppm. After growing sufficient plankton, all four ponds were equally stocked with adult and healthy Pangasianodon hypophthalmus@ 990 nos/ha corresponding to 12kg/dec in October 2015. Size of male fish ranged from 3.0 to 3.5 kg while female was 4.5 to 5.5 kg. The ratio of stocked fishes (female: male) was 2:1. The stocked fishes were fed with commercial pellet feed containing 35% protein, supplemented with vitamin premix. Cod liver oil was added at 1-2 ml/kg of feed to hasty eggs for early maturation. Feeding rate ranged from 10-3% of total body weight twice daily. Fishes were reared for five months to get suitable broods earlier than the normal spawning season. Stocked fishes were checked monthly by examining secondary sexual characters. In the GP ponds, fully matured females were first observed on 6th February 2016, which was two months earlier than the normal spawning season. About 21% female and 60% male Pangas became fully matured during mid-February in GP. A total of 98% female and 100% male of stocked Pangas became fully matured and ready for inducing during mid-March. Augmenting spawning season than the normal will increase culture period of Pangas, which ultimately will help to increase Pangas production. |
