WWW.WA S .ORG • WORLD AQUACULTURE • DECEMBER 2022 65 ( C O N T I N U E D O N P A G E 6 6 ) Egg Incubation, Hatching and Larval Rearing Embryo hatch was completed 22-24 hr after fertilization. Hatchlings moved to the bottom of the tank through the nylon net. Remaining non-fertilized eggs and shells must be removed immediately to avoid fouling the water. After 36 hr, hatchlings could swim freely and gather into darkest corners of the tank. Use water hyacinth/ date palm tree leaves as shelter/hiding place of larvae (Fig. 4). Newly hatched larvae use their yolk-sac to survive. Yolk sacs were absorbed in approximately 3 days. After the mouths open in 2 days, small quantities of feed must be offered in a corner of the tank. We used mixed zooplankton from nearby ponds, squished very small pieces of Tubifex worms or Artemia nauplii (2-3 times per day) as initial feed for larvae up to day 15 (Fig. 5). There is likely to be different sizes of fry from the same batch because of inappropriate feed acceptability, which may be avoided by visual observation. As they take feed, their abdomens become white-gray. After one week of feeding, larvae must be transferred to a larger nursery tank. Plankton was collected from ponds at morning or evening with a plankton net. The collected plankton was filtered through a fine net; 2-3 mL of plankton/L water was sufficient for larvae. Dead zooplankton was removed by siphoning at least once a day. Nursery Pond Preparation and Rearing Generally, a small size pond was suitable as a nursery pond. The pond bottomwas dried completely then lime applied on the dried bottom soil of the pond and left for 2-3 days. After 3 days, 2500 kg/ha cow dung was added to the pond. Then the pond was filled with fresh water and left for 7-9 days for plankton development. When the water color became green, it meant the water was ready for fry culture. The nursery pond was surrounding by a small-mesh net to protect fry from predators, including snakes, frogs, bucks, egrets, cormorants and lizards. After three weeks of rearing, when larvae were 15-20 mm, fry were transferred to a nursery pond for production of fingerlings. Supplementary feed was given two times (day and night) at 20 percent body weight per day. Fry were kept in nursery ponds for up to 40 days, until they reached 5 cm. Now, the seed produced was ready for stocking. Growout and Culture After 40 days fingerlings were transferred into culture pond for grow-out culture. Densities of 25,000-40,000/ha are recommended for of this species for grow-out culture. The larger size (5-10 g) had a good survival and growth rate in culture. Supplementary pelleted feed was used at 3-5 percent body weight twice per day. FIGURE 2. Pabda broodfish: male (left) and female (right). FIGURE 5. A paste of Tubifex worms for feeding pabda. FIGURE 3. Breeding hapa. FIGURE 4. Embryonic development of pabda.
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