Introduction to Cultured Macrobrachiumrosenbergii Macrobracium rosenbergii is commonly known as “scampi” or the giantfreshwater prawn and is native to the freshwater habitats of South-SoutheastAsia and Australia (Banu and Christianus, 2016). As the larval stages requiredevelopment in brackishwater, these freshwater environments must be in close proximityto the seas. The giant freshwater prawn is the most commonly cultured of thefreshwater prawns due to its high growth rates with a variety of formulateddiets and resiliency in varying temperatures and salinity (Banu andChristianus, 2016). The largest producers recorded in 2007 include China (51%of global), Thailand, India, Bangladesh and Taiwan, with smaller influences inMalaysia and Brazil (Banu and Christianus, 2016). Economic Significance in BangladeshThe freshwater prawn industry inBangladesh is an extremely important area of their economy producing 11% of theglobal total of giant freshwater prawns in 2007 (Ahamed et. al, 2014). Freshwaterprawn culturing is available to local people on small establishments withminimal skill and can be managed at a reasonable cost.
In Bangladesh, prawnfarming has decreased poverty rates by presenting job oppourtinies for both womenand men in the community providing employment for over 1.5 million people. Atotal of 275 232ha of land has been devoted to prawn farming, contributing to54.32% of the total export income for the fish farmers of Bangladesh (Ahamedet. al, 2014).Production and FeedingProduction of these freshwaterprawns occurs mainly in low lying rice fields (71%), locally refered to asghers, and the remaining occurs in pond culture systems. There are increasinglevels of management in the cultured systems, ranging from extensive, modifiedextensive and semi-intensive. Extensive culture systems use ghers to catch eggscoming in from local tides which are then left to grow without any human aid (Ahamedet.
al, 2014). More extensive systems rely on additional of fertilizers (cowdung, urea, triple super phosphate) to enhance the plankton food source in the gheror pond. These systems tend to have relatively low stocking densities with a productionof 10,000-18,000 post larvae/ha/year (Ahamed et. al, 2014).
Local feeds can bemade from boiled rice, wheat brain, molasses, oil cakes and fish meal, boostingproduction to 18,000-30,000 postlarvae/ha/year (Ahamed et. al, 2014). Dependingon the wealth of the farmer, ideal commercial pelleted feeds containing 5%lipid and 35% protein can be fed in quantities of 10-20% of the body weight ofthe prawns within a pond. Commercial feeds boost production dramatically to ayield of 400kg/ha from 175-200kg/ha which is typically seen with locally madefeeds. Different carp species can also by polycultured in integrated systemswith the prawns (2000-5000 fingerlings/ha) (Ahamed et. al, 2014).MarketingPrawns are often shipped live toconsumers in order to maximize on profit and avoid problems with shelf-life andreduction in sale price that arise when chilled or frozen. Chilling wholeprawns, or prawn tails typically has a shelf life of 3-5 days, while freezingprawns extends the shelf life to 6-12 months (New 2005).
Shipping managementtechniques such as maintaining density of about 600 prawns/L, providing goodaeration and keeping cool transport temperatures, will help minimizemortalities and injuries during transportation. Typical buyers of freshwaterprawns include locals, shops, markets and high quality restaurants (New 2005).Challenges A lack of technology and recent research is one ofthe most detrimental factors inhibiting the potential of these Bangladeshfarms, resulting in other problems such as the high production costs, lack ofavailable post larvae, potential flooding, low quality feed use and overalllack of management knowledge (Ahamed et. al, 2014). As with all prawn farming, diseasesand infections are apparent, and without proper management techniques the riskof disease mortality and spreading are much higher.
Environmental challengesinclude the rate at which wetlands are being turned into ghers (10% expansionevery year) and the collecting of postlarvae from wild stocks, threatening thewild species (Ahamed et. al, 2014).