FRESH WATER PRAWN FARMING
Varun Mishra1, Vimal Sharma2, S.K.Sharma3
1Research Scholar, College of Fisheries, Guru Govind Singh Marg, MPUAT, Udaipur- 313001(India), E mail: email@example.com; m: 91-7737349426
2Dean & Professor, College of Fisheries, Govind Singh Marg, MPUAT, Udaipur- 313001(India), E mail: firstname.lastname@example.org m: 91-9352507901
3Professor, College of Fisheries, Govind Singh Marg, MPUAT, Udaipur- 313001(India), E mail: email@example.com; m: 91-9352519189
Corresponding author: firstname.lastname@example.org
Although India has vast freshwater resources they are not fully exploited except for carps and cat fish culture. Hence there is urgent need to expand our production base. Need to utilize our natural resources productively to ensure the much needed food security. Considering the high export potential, the giant fresh water prawn, Macrobrachiumrosenbergii, the scampi, enjoys immense potential for culture in India.
Although reared in captivity from time immemorial, modern farming of this species originated in the early 1960s when FAO expert Shao-Wen Ling, working in Malaysia, found that fresh water prawn (Macrobrachiumrosenbergii) larvae required brackish conditions for survival.By 1972 the Hawaiian team led by Takuji Fujimura had developed mass rearing techniques for commercial-scale hatchery production of prawn post larvae (PL).This development spawned the first commercial farms in Hawaii. Both Thailand and Taiwan Province of China became pioneers in modern giant river prawn culture.The introduction of brood stock, initially from Hawaii and Thailand, into non-indigenous areas around the world began in the 1970s.
Global production had increased to over 200, 000 tones/yr, with Thailand and China being the major producers.In India Scampiproduction rose from a mere 6000t in 2000 to 40,000t in 2005 and by 2010 fell back to 10,800t as per FAO data.
Main producer countries
On worldwide basis, 49 species of Genus Macrobrachiumare of interest to the fisheries. At least 15 species are suitable for aquaculture. Over 30 species of this genus have been reported from Indian waters. Out of which M. rosenbergii, M. malcomsoniiand M. gangeticumare favoured in aquaculture.
Why culture Scampi?
Compatibility for polyculture.
Hardy and less disease prevalence.
Potential market- good demand for their taste flavor, bigger size.
Fast growth rate 50-60g within 6-7 months.
Diverse culture area- can withstand and grow in brackish water area also (up to 5 ppt).
Attain sexual maturity when 140-150mm long and 30-40g weight.
Seed availability in nature
The breeding takes place in low saline waters, estuaries, which is also needed for larval and post larval development after incubation. Though seed may be available in natural sources to a limited extent, for large scale culture there is a need to ensure regular supply of seed.For ensuring availability of quality seed in predictable quantity freshwater prawn hatcheries should be encouraged, technology for which is already developed. Freshwater prawn hatcheries are coming up in many states.
Healthy seed is light brown in color with presence of mild pigmentation. PL5-PL10 is ideal for transportation and stocking in scampi culture.Temperature of 22-250C is better for transportation of seed to get good survival.
Direct stocking of seed to pond is not preferred because of abnormal size variation and high cannibalism. Seed will be stocked in nursery pond for 30 to 45 days.Indoor nurseries are stocked at 1000-2000 PL/m³, depending on whether substrates are used or not. Outdoor nurseries may be stocked with newly metamorphosed PL or with juveniles from an indoor nursery @ 1 000/m² PL,200/m²small juveniles (0.02 g) or 75/m² of 0.3-0.4 g juveniles, but increased densities are possible if substrates are used.
The aspects to be considered are:
Topography of the area.
The area should be free from pollution and flooding.
Other considerations like approach roads etc. have also to be taken into account.
Proper water and soil quality.
Rectangular ponds are suitable mainly from the harvesting point of view.A convenient width is 30-50 m, whereas length of the pond depends on site, topography and farm layout.Normally a size of 0.5 to 1.5 ha is found suitable. The average depth of the ponds should be 0.9m with a minimum of 0.75m and a maximum of 1.2m. Dike slope may be kept at 2:1. Bund must have a freeboard of at least 60 cm above the highest water level in the pond. Designing and layout of the farms may be done keeping in view the water intake and water outlet facilities. The drainage system should be designed carefully to prevent mixing of outlet water with incoming water.
Varies from 4000 to 50000 nos. of post larvae per ha depending on the type and intensity of the management practices. The culture system may be monoculture or polyculture with carps. In case of polyculture with carps the more pond depth is preferred at 4-5 feet.Stocking density of prawn may vary from 2500-20000 post larvae. The carp fingerlings may be of the order of 2500 - 5000 Nos.
The rate of feeding is determined by stage of growth, water quality, density of stock and other manuring practices. Generally the feeding rate may be 5% of the body weight.The prawns are fed commercial or "farm-made" feeds. Either fed moist or (usually) after sun-drying. Feeds with 5% lipid and 30-35 % protein are common and an FCR of 2:1 or 3:1 is achieved with dry diets.
Mainly 6 to 12 months depending on the type of culture practice. For monoculture 6-8 months and polyculture 8-12 months.Males grow faster and females mature very early even at 3 to 4 months.The average growth may range from 50 to 200 gms depending on the duration, density, water quality, feeding etc.The survival rate may range 50% to 70% depending on the type of management practices.
Diseases and control measures
The major disease problems occur because of poor intake water treatment, husbandry, overcrowding, poor sanitation, inadequate quarantine procedures. The measures to combat these problems are referred to as improved husbandry. Immuno-stimulants and other agents which improve the non specific immunity can be used as disease prophylaxis method.
Basically there are two methods of harvesting:
Culling (cull harvesting)
Time to harvest depends partly on growth rate and marketable size range. Cull-harvesting is used to harvest market-sized animals from the pond at intervals and removes the faster growing prawns. In tropical ponds cull-harvesting usually starts 5-7 months after PL have been stocked. After cull-harvesting commences, totally seine each pond once per month or partially seine it twice per month. After about 8-11 months, drain the pond and sell the whole harvest.
The major drawbacks are following:
Problems associated with repeated harvesting (cull harvesting), disturbing the pond bottom.
Possible infections while performing claw ablation.
Intensive farming of Scampi is never possible due to Cannibalism and HIG as the blue claw males prevent other males in its vicinity from growing bigger.