Samir Malla and S. Banik
Abstract
The endangered catfish, Ompok bimaculatus (Bloch, 1794) was the subject of captive breeding programme in Tripura, India from 2011 to 2013 in order to re-establish the wild population and develop breeders for stock management. Approximately, 110 nos. of wild O. bimaculatus were collected from natural habitats (initial mean weight 16±3.50 g) and were reared in pond carp poly culture system. Intramuscular injection of Ovaprim was administered 40 days before spawning as preparatory dose (male 0.3 mL/kg; female 0.5 mL/kg) for gonadal maturation. Induced spawning under captivity was carried out by administering intramuscular injection in 4 different doses (0.3, 0.4, 0.5 and 0.6 mL/kg body weight) of Ovaprim during June to July. In the four experimental sets, distinct spawning behavior was noticed with different hormonal doses whereas in control set, no spawning activity was observed. The most suitable and economical dose of Ovaprim was estimated to be 0.5 mL/kg body weight for male and 0.6 mL/kg body weight for female and the latency period for spawning was 7-8 hrs at water temperature of 28.5±1.5ºC. The fecundity ranged from 151-257 eggs/g body weight of fish and the fertilization rate was 75.3-92.8%. The eggs hatched out in 24±1.5 hrs and the hatching rate was 55-78.6%. The mean egg diameter was 0.98 ±0.22 mm and the yolk-sac was completely absorbed in 3 days. The newly hatched larvae measured 5.64±0.38 mm in length and 0.009±0.0008 g in weight in 3 days. The survival rate of hatchlings varied from 45.8 to 66.5%. Feeding of larvae with live tubifex worms along with zooplanktons showed best result in terms of survival rate, health condition and growth performance. Natural mortality and cannibalisms were also lower on these foods and the optimum frequency of feeding was 4 times/day. These findings show a farmer friendly and low cost technology (Benefit-Cost Ratio=2.46) for captive breeding in and around O. bimaculatus inhabiting areas of Tripura.