62 JUNE 2016 • WORLD AQUACULTURE • WWW.WAS.ORG jaws, opercula and gills. Some hatchery operators also feed larvae on the third day. Live mixed zooplanktons (rotifer, copepod, Daphnia and Moina) are fed to larvae; in some cases, larvae are fed Artemia nauplii, tubifex worms and egg custard (Srivastava et al. 2012, Saxena 2014). There is no quantification of feed supplied to rearing tanks, but ad libitum feeding is adopted. Besides these, ICAR-CIFA developed a larval feed (Starter-M) exclusively for magur larvae (Fig. 5). It is fed to one-week-old larvae with a gradual withdrawal of live feeds. It enhances growth (30-40 mg) and survival (>80 percent) of the larvae during 14-15 days of rearing (Fig. 6). Some farmers also lengthen the rearing period to 3-4 weeks to get bigger seed, which are sold easily. Fry to Fingerling Production Fingerling production is carried out with the aim to get a higher price and to get higher production if stocked for grow-out. The release of fry directly into ponds results in lower recovery related to natural mortality or predation. It is recommended to rear fry in small cement tanks of 10-20 m2 for better survival and easy management. These tanks are provided with 2-3 cm of soil and a water level of 25-30 cm. Single superphosphate (100 g) and filtered cow dung (2 kg) are used to provide nourishment for plankton growth and bottom biota development. Tanks are inoculated with plankton to expand their population, 6-7 days before fry stocking. Fry can use live feed until they are habituated to compound feed (30-35 percent protein) during rearing. Inasmuch as the water depth is low, water temperature rises during mid-day. Hence, tanks are provided with floating weeds, such as water hyacinth, for shade or shelters are provided at the tank bottom for fry. The shelters serve as hiding places for a large number of fry, which makes it easier to feed them near or around the shelter. Usually fry are reared at 100-200/m2 . Shooting behavior is found at this stage. Hence it is necessary to sort at regular intervals to reduce the competition for feed among small fry and shooters, which also enhances survival. Formation of filamentous algae occurs in the fingerling tank because of the shallow water depth and high nutrient leaching from uneaten compound feed (Fig. 7). Therefore, it is essential to remove filamentous algae at regular intervals for better growth and survival of fry. Fry usually grow to around 1 g in 40-45 days. Fry are segregated and stocked again at 50-100/m2 for further rearing, until they reached 4-5 g in another 60-70 days. In spite of this, many farmers release fry to small nursery ponds because of a lack of a proper rearing system. Some seed growers also divide a paddy field into small plots to rear fry along with paddy rice for enhanced production (Fig. 8). Best Management Practices • Broodfish of 100-150 g are stocked at 2-3/m2 and fed with 32 percent protein pellet feed at 2-3 percent body weight twice a day. • Injection of 1-1.5 ml synthetic hormone (Ovaprim/Ovatide/ WOVA-FH) is sufficient to induce ovulation. Females are striped after 16-17 h of hormonal injection to obtain good-quality eggs. • Maintenance of water quality through aeration and water replenishment during larval rearing is important to reduce stress in larvae, leading to enhanced growth and survival. • Larvae can be reared at 1000-1500/m2 for 15-20 days in indoor conditions for better growth and survival. Stocking at higher density leads to sudden mortality and reduced growth. • Live feed, such as zooplankton, tubifex and Artemia nauplii should be provided during the initial phase of larval feeding and then gradually weaned to compound feed by gradual withdrawal of live feed. This husbandry practice stimulates fry to accept feed immediately after release into nursery tanks during fingerling production, which ultimately increases growth and survival. • Segregation of shooters and removal of filamentous algae at periodic intervals results in greater growth and survival. Notes S.K. Sahoo*, S. Ferosekhan, S.S. Giri and S.K. Swain, ICARCentral Institute of Freshwater Aquaculture, Kausalyaganga, Bhubaneswar-751 002, Orissa, India. * Corresponding author e-mail: sksahoo100@rediffmail.com References Dhara, K and N.C. Saha. 2013. Controlled breeding of Asian catfish Clarias batrachus using pituitary gland extracts and Ovaprim at different temperatures, latency periods and their early development. Journal of Aquaculture Research & Development 4:186. Goswami, U.C. and N.N. Sarma. 1997. Pituitary dose optimization for induced ovulation, in-vitro fertilization and production of normal fry of Clarias batrachus (Linn.). Asian Fisheries Science 10:163-167. Sahoo, S.K., S.S. Giri and AK. Sahu. 2004. Effect of stocking density on growth and survival of Clarias batrachus (Linn.) larvae and fry during hatchery rearing. Journal of Applied Ichthyology 20:302305. Sahoo, S.K., S.S. Giri and AK. Sahu. 2005. Effect on breeding performance and egg quality of Clarias batrachus (Linn.) at various doses of Ovatide during spawning induction. Asian Fisheries Science 18:77-83. Sahoo, S.K., S.S. Giri and A.K. Sahu. 2005. Induced spawning of Asian catfish, Clarias batrachus (Linn.): effect of various latency periods and SGnRHa and domperidone doses on spawning performance and egg quality. Aquaculture Research 36:1273-1278. Sahoo, S.K., S.S. Giri, S. Chandra and A.K. Sahu. 2007. Spawning performance and egg quality of Asian catfish Clarias batrachus (Linn.) at various doses of human chorionic gonadotropin (HCG) injection and latency periods during spawning induction. Aquaculture 266: 289-292. Sahoo, S.K., S.S. Giri and S. Chandra. 2008. Effects of latency periods and injection doses with carp pituitary extract on spawning performance and egg quality of Asian catfish Clarias batrachus (Linn.). Journal of Applied Aquaculture 20: 295-303. Saxena, S. 2014. Impact of different feeds on growth of catfish Clarias batrachus (Gunther). International Journal of Science and Research 3(8):1875-1878. Sinha, M., B.K. Mahapatra, D. Saha and N.J. Maitra. 2014. Mass scale seed production of magur, Clarias batrachus at farm level through improvised modifications. International Journal of Fisheries and Aquatic Studies 2(2):210-214. Srivastava, P.P., S. Raizada, R. Dayal, S. Chowdhary, W.S. Lakra, A.K. Yadav, P. Sharma and J. Gupta. 2012. Breeding and larval rearing of Asian catfish, Clarias batrachus (Linnaeus, 1758) on live and artificial feed. Journal of Aquaculture Research & Development 3:134.
RkJQdWJsaXNoZXIy MjExNDY=