78 DECEMBER • WORLD AQUACULTURE • WWW.WAS.ORG Monoculture Extensive, semi-intensive, or intensive monoculture of freshwater prawns is possible in Bihar. Extensive monoculture of prawns can yield up to 500 kg per hectare annually (Figure 3). Prawns in extensive monoculture are usually stocked as post-larvae or juveniles at rate of 1-4/m2. In an extensive culture system, extra feeding is not offered. In semi-intensive monoculture systems, a supply of a balanced feed and also fertilization of the pond is necessary. Monitoring of the water quality, prawn health, and growth rate are done in conjunction with routine management of ponds. With a productivity of 5001000 kg/ha/yr, semi-intensive pond production involves stocking of post-larvae or juveniles at 4-20/m2. Intensive monoculture of freshwater prawn involves stocking more than 20 post-larvae/m2 in small earthen or concrete ponds (up to 0.2 hectare) with constant aeration and high water exchange (up to 80%), with an annual production of more than 5000 kg/ha. These ponds are expensive to build and maintain, and they demand a high level of management such as the use of a diet with complete nutrients (Figure 4) and regular water quality parameter monitoring. Polyculture Prawns are being cultured in polyculture systems with one or more fish species, such as common carp, Chinese carps, Indian major carps, and tilapia. Polyculture of freshwater prawns with Indian major carps involves raising prawns alongside Catla or Rohu in the same water body. This practice aims to increase overall production and utilize resources more efficiently. Freshwater prawns always have synergistic positive effects in polyculture systems, such as more consistent levels of dissolved oxygen, fewer predators, cycling of fish waste to boost feed efficiency, higher productivity and higher crop value with the addition of a high-value species. Polyculture can be more economically viable than monoculture, providing a diversified income stream. Polyculture can also help maintain a healthy and stable water environment by introducing diverse species that can help with nutrient cycling and waste management.For polyculture, recommended stocking densities can vary, but generally 10,000 to 15,000 post-larvae are stocked along with 5,000 to 6,000 carp fingerlings per hectare. Expected production from polyculture can be around 500 kg/ha of prawns in 6-8 months, along with 4 to 5 tonnes of fish. Prawn harvesting involves different methods depending on the culture system. Seining, draining, and culling are common methods used (Figure 5). The management of a polyculture pond becomes quite complex when the produce is being harvested. It is possible to cull-harvest large fin fish that obstruct prawn culture from polyculture ponds. Therefore, in prawnfinfish polyculture systems, harvesting often occurs in batches. In order to maximize production, it is essential to coordinate fish production of marketable sizes with prawn production. Conclusion Among India’s Eastern states, Bihar is a fast growing state for aquaculture, especially for Indian Major Carps. But prawn farming has huge potential in Bihar. Polyculture of carps and other species has gained popularity in recent decades in Bihar. Higher aquaculture production and value through polyculture of prawns can attract the farmer’s interest. Therefore, it is appropriate to emphasize Macrobrachium rosenbergii for aquaculture in Bihar, and the current outlook for its culture with carps is very optimistic among fish farmers. However, institutional support, seed availability at the local level, capacity building and training, and linkage between farmers and markets at export and domestic level are essential to popularize prawn farming in Bihar. Notes Tarkeshwar Kumar, Vivekanand Bharti*, Kamal Sarma, S.K. Ahirwal and Anup Das, ICAR Research Complex for Eastern Region Patna- 800 014, India. * Corresponding author: bhativivekanand24@gmail.com FIGURE 5. Harvesting in a polyculture system. FIGURE 4. High protein pelleted feed for prawns.
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