World Aquaculture Magazine -December 2021

WWW.WA S .ORG • WORLD AQUACULTURE • DECEMBER 2021 67 RackCulture System The main operating principle of rack culture is zero water discharge and it is thus maintained as a recirculation system (Marian et al . 1989). The main components of a rack culture system are culture troughs (45 cm × 30 cm × 15 cm), a sedimentation tank (60 cm × 45 cm × 45 cm), a collection tank (75 cm × 60 cm × 60 cm), a water storage tank or overhead tank (75 cm × 60 cm × 60 cm), a filtration unit, denitrification unit (PVC tubes packed with different layers of gravel (diameter = 0.5 cm) or charcoal pieces, pieces of calcareous shells, and sand) and aeration units. The overhead tank is positioned at 3 m height and the inlet pipe is connected to the collection tank and outlet to culture troughs. Water flows from troughs to the sedimentation tank at 86 L/d, which allows the dispersed particles to settle. In the filtration unit, particles are filtered through two filters with coarse (<5000 µm) and fine (> 100 µm) sand particles packed between perforated cement plates. Filtered water then passes to the denitrification unit. Filtered water in the collection tank can be delivered to the overhead tank by a pump, which is activated by a water level sensor. Important Conditions The culture set up should be kept in a place where favorable conditions can be maintained. The following points should be addressed in tubifex culture: • A minimum dissolved oxygen concentration of 3 mg/L should be maintained. • Place the set up in the shaded area and direct sunlight to avoid, as tubifex are photophobic. • Continuous water flow of 250 mL/min should be maintained. • Ensure that inoculum is free from pathogens and contaminants before stocking to support biosecurity in the culture system. • Depuration and disinfection are done using KMnO 4. Harvesting Harvesting is done at intervals based on tubifex biomass. It can be done in the early morning or late evening when the worms come to the surface. The best method of harvesting is segmentation of media into different parts and filtering and washing through a nylon mesh net to remove the media. Water should flow continuously to allow evacuation of mud from the gut. After proper depuration, worms can be given as a fresh feed to fish or further processed by freezing. Conclusion Tubifex is an important live food for food and ornamental fish and is a preferred source for larvae and broodfish. The main advantage of growing tubifex as a live food is the high nutritious value, especially protein content (63 percent). Tubifex worms have a high market value and the preference is for live worms over frozen forms. Tubifex worms also have value as an export product due to strong international market demand. The culture of tubifex is more preferable than wild harvesting to minimize the risk of disease outbreak or transmission. Production cost can be low as worms are grown on decaying organic matter in the form of agricultural byproducts. The production of tubifex in a small system for the minimum duration can minimize costs. Tubifex culture in recirculation systems is recommended for sustainable production. Notes Thejaswini * , Upasana Sahoo, Shamna N, Babitha Rani. A.M., Central Institute of Fisheries Education, Off Yari Road, Panch Marg, Versova, Andheri (W), Mumbai-400061 * Corresponding author: thejaswini.aqcma811@cife.edu.in References Ahamed, M.T. and M.F.A. Mollah. 1992. Effects of various levels of wheat bran and mustard oil cake in the culture media on tubificid production. Aquaculture 107:107-113. Anwar, H, H. Mahmud and M.F.A. Mollah. 2011. Effects of soybean meal and mustard oil cake on the production of fish live food tubificid worms in Bangladesh. World Journal of Fish and Marine Sciences 3:183-189. Chanu, T.I, S. Surnar, A. Sharma and A. Muralidhar. 2018. Effect of different culture media on mass production of fish live food tubifex. Aquaculture Times 4:25-29. de Valk, S, A.F. Khadem, C.M. Foreman, J.B. van Lier and M.K. de Kreuk. 2017. Physical and biochemical changes in sludge upon Tubifex tubifex predation. Environmental Technology 38:1524-1538. Hasan, M., M.I.M. Haque, N. Akter, M.S. Rahman and A.S. Eti. 2019. Effects of wetting media cattle blood, rice gruel and water on the yield and amino acid composition of tubificid worms. Journal of the Asiatic Society of Bangladesh, Science 45:229- 239. Herawati, V.E, R.A. Nugroho, J. Hutabarat and O. Karnaradjasa. 2016. Profile of amino acids, fatty acids, proximate composition and growth performance of Tubifex tubifex culture with different animal wastes and probiotic bacteria. Aquaculture, Aquarium, Conservation & Legislation 9:614-622. Kaster, J.L. and J.H. Bushnell. 1981. Cyst formation by Tubifex tubifex (Tubificidae). Transactions of the American Microscopical Society 100:34-41. Marian, M.P. and T.J. Pandian. 1984. Culture and harvesting techniques for Tubifex tubifex . Aquaculture 42:303-315. Marian, M.P, S. Chandran and T.J. Pandian. 1989. A rack culture system for Tubifex tubifex . Aquacultural Engineering 8:329-337. Tubifex is an important live food for food and ornamental fish and is a preferred source for larvae and broodfish. The main advantage of growing tubifex as a live food is the high nutritious value, especially protein content (63 percent). Tubifex worms have a high market value and the preference is for live worms over frozen forms.