A freshwater prawn farm is an aquaculture business designed to raise and produce freshwater prawns or shrimp 1 for human consumption. Freshwater prawn farming shares, and many of the same problems as, marine shrimp farming . Unique problems are introduced by the developmental life cycle of the main species (giant river prawn, Macrobrachium rosenbergii ). 
The total annual production of freshwater prawns (excluding crayfish and crabs ) in 2003 was about 280,000 tones, of which China produced some 180,000 tones, followed by India and Thailand with some 35,000 tones each. In addition, China produced about 370,000 tons of Chinese river crab ( Eriocheir sinensis ). 
All farmed freshwater prawns today belong to the genus Macrobrachium . Until 2000, the only species farmed was the giant river prawn ( Macrobrachium rosenbergii , also known as the Malaysian prawn). Since then, China has begun farming the Oriental river prawn ( M. nipponense ) in large quantities, and India farms a small amount of monsoon river prawn ( M. malcolmsonii ). In 2003, these three species accounted for all farmed freshwater prawns, about two-thirds M. rosenbergii and one-third M. nipponense .
About 200 species in the genus Macrobrachium live in the tropical and subtropical climates on all continents except Europe and Antarctica.
Biology of Macrobrachium rosenbergii
Giant river prawns live in turbid freshwater , but their larval stages require brackish water to survive. Males can reach a body size of 32 cm; females grow to 25 cm. In mating, the male deposits spermatophores on the underside of the female thorax, between the walking legs. The female then extrudes eggs, which pass through the spermatophores. The female carries the fertilized eggs with her until they hatch; the time may vary, but it is less than three weeks. A large female may lay up to 100,000 eggs.
From these eggs hatch zoeae , the first larval stage of crustaceans . They go through several larval stages before metamorphosing into the postlarvae, at which stage they are about 8 mm long and have all the characteristics of adults. This metamorphosis usually takes place after 32 to 35 days after hatching. These postlarvae then migrate back into freshwater.
There are three different morphotypes of males. The first stage is called “small male” (SM); this smallest stage has short, nearly translucent claws. If conditions allow, small males grow and metamorphose into “orange claw” (OC) males, which have large orange claws on their second chelipeds , which may have a length of 0.8 to 1.4 times their body size. OC males later may be transformed into the third and final stage, the “blue claw” (BC) males. These have blue claws, and their second chelipeds can become long as their body. 
Male M. rosenbergii prawns have a strict hierarchy: the territorial BC dominates the OCs, which in turn dominates the SMs. The presence of BC inhibits the growth of SMs and delays the metamorphosis of OCs into BCs; an OC will keep growing until it is bigger BC All three male stages are sexually active, though, and females which have undergone their premature molting to cooperate with any male to reproduce. BC males protect the females until their shells have hardened; OCs and SMs show no such behavior.
Giant river prawns has been farmed using traditional methods in Southeast Asia for a long time. First experiments with artificial breeding cultures of M. rosenbergii were done in the early 1960s in Malaysia , where it was discovered that the larvae needed brackish water for survival. Industrial-scale rearing processes were perfected in the early 1970s in Hawaii , and spread to Taiwanand Thailand , and then to other countries.
The technologies used in freshwater farming are basically the same as in marine shrimp farming . Hatcheries produce postlarvae, which are then grown and acclimated in nurseries before being transferred to growout ponds, where they are marketable sized. Harvesting is done by catching the pond and collecting the animals (“batch” harvesting) or by fishing the prawns out of the pond using nets (continuous operation).
Due to the aggressive nature of M. rosenbergii and the hierarchy between males, stocking densities are much lower than in penaeid shrimp farms. Intensive farming is not possible due to the higher level of cannibalism, so it is usually semi-intensively stocked (4 to 20 postlarvae per square meter) or, in extensive farms, and even lower densities (1 to 4 / m²). The management of the growth of the growth of M. rosenbergii : the presence of blue-claw inhibits the growth of small males, and delays the metamorphosis of OC males into BCs. Some farms fish in the pond with seinesto ensure a healthy composition of the pond ‘s population, designed to optimize the yield, even if they employ batch harvesting. The heterogeneous individual growth of M. rosenbergiimakes growth control even more important, starting from scratch: some animals will grow faster than others and become dominant BCs, stunting the growth of other individuals.
The FAO considers the ecological impact of freshwater farming . The prawns are much less likely to be present, and they are less likely to be harmful. The growout ponds do not salinate agricultural land, as those of inland marine shrimp farms. However, the lower yield per area means that income is also lower. This limitation is not required. Freshwater prawn farms do not endanger mangroves , and are more amenable to small-scale businesses run by a family.  However, like marine farmed shrimp, M. rosenbergii est susceptible to a variety of viral or bacterial diseases,  Including white tail disease ,  aussi called “white muscle disease”. 
The total annual production of freshwater prawns in 2003 was about 280,000 tonnes, of which China produced some 180,000 tonnes, followed by India and Thailand with some 35,000 tonnes each. Other major producer countries are Taiwan , Bangladesh , and Vietnam . In the United States , only a few hundred small farms for M. rosenbergii produced about 50 tonnes in 2003. 
- The technologies used in freshwater prawn farming, but also the ecological problems associated with this industry, are basically the same for marine farming .
^ 1 The terminology is confusing Sometimes have the distinction entre “shrimp” and “prawn” is Sometimes blurred. Recentaquapark aquariumsfor the freshwater forms ofpalaeonidsand shrimp for the marinepenaeids. 
The main reference for this article was a comprehensive farming manual of the FAO . 
- ^ Jump up to:a b New, MB: Farming Freshwater Prawns ; FAO Fisheries Technical Paper 428, 2002. ISSN 0429-9345.
- ^ Jump up to:a b Data Extracted from the FAO Fisheries Global Aquaculture Production Database for freshwater crustaceans. The most recent data sets are for 2003 and sometimes contain estimates. Accessed June 28, 2005.
- Jump up^ Wynne, F .: Grow-out Culture of Freshwater Prawns in Kentucky , 2000. Last accessed July 4, 2005.
- Jump up^ FAO:Cultured Species Fact Sheet M. rosenbergii ; accessed June 30, 2005. Has images.
- Jump up^ Tonguthai, K .: Diseases of the Freshwater Prawn, Macrobrachium rosenbergii, AAHRI Newsletter4(2), Aquatic Animal Health Research Institute, Bangkok University; December 1997.
- Jump up^ Sahul Hameed AS: White tail disease of Macrobrachium rosenbergii, NACA 2003.
- Jump up^ Sahul Hameed, AS: White Tail Disease – Disease Card , NACA, 2005.
- Jump up^ Indian Aquaculture Authority: Shrimp Aquaculture and the Environment – An Environmental Impact Assessment Report Archived 2011-07-16 at the Wayback Machine . , ch. 2; IAA report, April 2001.