Effect of Different Doses of Pituitary Gland (PG) Hormone on Induced Breeding of Bheda/Meni (Nandus nandus) Fish

An experiment on induced breeding of Bheda/Meni fish (Nandus nandus) was carried out to determine the optimum dose of pituitary gland hormone during December 2018 to June 2019 at Floodplain Sub-station of Bangladesh Fisheries Research Institute (BFRI), Santahar, Bogura. In this experiment, PG was used as inducing agent for both male and female fish. For induced breeding, PG was administered at the rate of 1, 2 and 3 mg/kg body weight to male brood fish, and correspondingly 2, 4 and 6 mg/kg body weight to female brood fish that were considered as the treatments namely, T1, T2 and T3, respectively. Fifty pairs of male and female fish were collected from the Raktadaha beel from where forty-five pairs were selected for induced breeding and the average body weight of the male and female were 43.0±2.5 gm and 55.2±3.0 gm in T1, 45.1±2.9 gm and 56.0±2.8 gm in T2, and 40.3±2.4 gm and 52.6±3.2 gm in T3. The male-female ratio was maintained as 1:1 in the breeding hapa. It was observed that female and male brood fishes ejected eggs and milt, respectively at the contemporary times. Ovulation occurs naturally after 8-10 hours of injection. The fecundity of fish (body weight 45 to 60 gram each) varied from 7,232-27,546. The fertilized eggs were hatched within 16-20 hours. The hatchlings were reared in rearing tank up to 5 days. The fertilization rate of Nandus nandus were 76±4 %, 93±5 % and 57±3 %, in T1, T2, and T3, respectively and the hatching rate were 72±3 %, 86±2 % and 61±4 % in T1,T2 and T3, respectively. Both the fertilization and hatching rates were significantly higher (p<0.05) in T2 treatment than T1 treatment followed by T3 treatment. The mean values of water temperature (°C) were 29.5±1.15, 30.0±2.03 and 30.8±1.76°C, pH was 7.4 ±0.46, 7.8±0.53 and 7.3±0.49 and dissolved oxygen (mg/L) were 5.5±0.61, 5.3±0.24 and 5.8±0.56 in brooder tanks, breeding hapa and larval hapa, respectively during the experiment and did not vary (P>0.05) among them and were suitable for induced spawning of Nandus nandus. Based on the findings of the present experiment, it was revealed that T2 showed the best outcome in terms of fertilization rate (93±5%) and hatching rate (86±2%) among the three treatments under optimum water quality parameters where PG hormone were used at the rate of 2 and 4 mg/kg body weight for male and female fish, respectively. Therefore, the present findings could be used in induced breeding of N. nandus for the development of hatchery propagation. Further trials on rearing or culture of this endangered fish under different stocking densities or feedings might be conducted at on-station and on-farm levels in Bangladesh as well as elsewhere of this region to save the fish from extinction or for its conservation and rehabilitation.