The sexual maturity of female sultan fish, Leptobarbus hoevenii was studied by determining fecundity and gonadosomatic index (GSI). It was found that the size at sexual maturity of female sultan fish was with 40.85±3.80 cm in total length and 783.00±217.46 g in body weight. Fecundity was 76,414.69±36,586.61 ova/fish and gonadosomatic index (GSI) was 8.14±3.92%. Newly hatched larvae of sultan fish were produced by the natural method using chemical injection (Suprefact and Motilium) for induced spawning. The injection was done by using Suprefact 20 µg/kg and Motilium 5 mg/kg. For male and female brooders, the injection was done once. The hatching period and hatching rate experiments were carried out in a 15-liter glass aquarium (water volume 12 liters) containing 1,000 eggs. It was found that the eggs were semi-buoyant egg and rounded. The diameter of eggs is ranging around 400-1,900 mm. The average hatching period was 12 hr 12 mins and hatching rate was 82.6% at the water temperature of 27-29.5 °C.
The newly hatched larvae were 162.35±9.9 mm in total length with yolk sac of 77 μm3 in volume. The yolk sacs were completely absorbed within 106 hr after hatching. All the larvae opened their mouth at about 36 hr after hatching (176.95±8.1 mm TL) with mouth measuring 182.36 μm in height.
Feeding experiments were carried out in the 15-liter glass aquarium with 10 liters of water containing 600 larvae aged 2.5 days post-hatching and feed them by Moina. At 2-hourly intervals, 20 larvae were collected randomly from the aquarium, At 62 hr after hatching, the mouth size was measured to be 412.27 μm. The onset of feeding showed 0.05 individual Moina/ larvae.
A starvation experiment was studied in the 15-liter aquarium with 12 liters of water by three replications. In each replication of without feeding has 300 newly hatched larvae and observed every 2 hours. Totally larvae died within 112 hr. after hatching at water temperature ranging between 27.0 and 29.5 °C. Comparison the total length with feeding and without feeding was studied in the 15-liter round aquariums with 12-liter with water. In each experiment has 1,000 newly hatched larvae. To know the variation of growth rate twenty larvae of both trials observed total length every day for 5 days at water temperature ranging between 27.0 to 29.5 °C was found that, which mean of total length of feeding fish and without feeding were 0.224 and 0.214 cm, respectively. There is a difference between feeding and without feeding approximately 4.75 % in total length.
KEYWORDS: Propagation, Yolk absorption; Start of feeding, Starvation; Sultan Fish,
Leptobarbus hoevenii (Bleeker, 1851)