Giant freshwater prawn (Macrobrachium roresnbergii), also commonly called as “Scampi”, is a native of tropical and sub-tropical Indo-West Pacific region, especially South and Southeast Asia. This species alone contributes about 45.30% to the total farm production of freshwater prawns in the world. This is a robust species, relished by people around the world and in some pockets fetches even better price than other shrimps and prawn species.
The global trend of production of farmed freshwater prawn M. Rosenbergii between 2008 and 2017 indicates a positive trend except for the three years during which the production slightly fell below 200,000 tons mark (Fig above). During this period the production has gone up by about 20% while the value by 64%. However, there has been a slump in production in some countries but there has been recovery as well. China is the leading producer with 137,360 tons of annual production followed by Bangladesh and Thailand, though during the middle of the last decade India was the second-largest producer after China with annual production touching as high as 42,820 tonnes in 2005-6. Vietnam has almost doubled its production within the last ten years touching 15,000 tonnes mark during 2017. Most remarkable progress is noted in Indonesia where the annual production of this prawn has increased four times from mere 600 tons in 2010-11 to about 2,200 tons in 2017.
Earlier, Nair & Salin (2012) reported that macrobrachium culture is prevalent in about 53 countries across the world. Freshwater prawn production in India includes from both farming and wild capture of two prawn species, the giant freshwater prawn Macrobrachium rosenbergii and the monsoon river prawn, M. malcolmsonii.
According to Marine Products Export Development Authority (PEDA) of India, during the year 2010-11 this species was cultivated in 113,853 hectares and produced a total of about 18,575 tons. However, has been a sharp fall in both, the area under cultivation as well as production since then. During 2017-18, its cultivation reduced to about 59,099 ha and the production also came down to 57691 tons. Though the overall production of scampi is on the rise globally, there has been signs of slumps and recovery in several countries including Thailand, Vietnam, and Bangladesh. Currently the culture of this species is still prevalent in landlocked northeastern states of India including Tripura, West Bengal, Odisha and to certain extent in AP where seed is available. In Tripura a private hatchery is consistently running since last 20 years and now it has scaled up its operation. In West Bengal an innovative farmer is successfully producing seed through natural spawning in small ponds followed by further rearing the larvae for three to four weeks in nursery ponds to produce juveniles and selling it to local farmers. However, unlike Thailand, Vietnam and other Southeast Asian countries, farmers in India follow low extensive culture with carps and get sizable additional income from this species.
Constraints
Major constraints for the slump of scampi culture in India, as experienced by farmers include stunted growth because of poor seed quality and the broodstock which had been inbred over several generations; pond water quality issues; limiting export market, limited availability of seed and occasional emergence of diseases. However, the most important reason is the introduction of Vannamei shrimp which has replaced this species in several freshwater areas especially adjacent to coastal areas. The improved culture technology involves manual sexing of the prawns at 3 months and restocking only the male prawns into new ponds at low density. The technique gives higher yield and reduces incidence of disease.
Potential for growth
Due to the emergence of diseases in Vannamei shrimp, there is a renewed interest of farmers in scampi farming. On the other hand, there are emerging areas for freshwater prawn farming in the form of reservoirs, floodplains, carp polyculture ponds, rice fields, etc. Due to the good domestic market and commanding relatively higher prices ranging from Rs500 – 1000 / kg this species ensures additional income for aquaculture farmers and fishers and thereby has significant potential towards doubling farmers’ income by the PM. The emergence of low-cost seed production including natural breeding in small managed ponds and further rearing in nurseries till the juvenile stage is expected to be popular among farmers as new avenues. The relatively less intensive farming practice with low stocking densities and lower costs of production makes this species attractive for small and marginal farmers. On the one hand where shrimp aquaculture which follows an intensive and high investment culture methods, freshwater prawn culture follows extensive, low cost, low level of technologies, compatible with freshwater carps thereby making it an effective tool towards contributing to enhancing the income of farmers and rural livelihood development and larger socio-economic impact.
Future course of action
To revive prawn aquaculture and maintain a sustainable level of production, alternative systems are necessary which must balance adequate environmental benefits and economic returns similar to or better than monoculture. Improvement can possibly be made by introducing manual sexing of the prawns at 3 months and restocking only the male prawns into new ponds at low density. Speedy genetic selection program and production of genetically improved broodstock is critical to achieving this goal. Side by side efforts be made to conduct an effective and meaningful training program to build team of skilled technicians and further hand-holding may be carried out to identified hatchery operators, entrepreneurs, innovative farmers, and other stakeholders.
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