World Aquaculture March 2019

58 MARCH 2019 • WORLD AQUACULTURE • WWW.WA S.ORG a bioactive combination of fermented rice bran and fermented soybeans – called Aquamimicry fermented soybeans (AFSY) – that stimulates the production of natural foods, especially zooplankton, to support production of vegetarian or pellet-free shrimps (Romano and Kumar 2017). In Brazil, one of the major bottlenecks for the expansion of M. rosenbergii farming is the lack of a specific feed. Farmers generally use feed for marine shrimp or tilapia to rear freshwater prawns, causing low productivity and profit reduction. On the other hand, natural forage organisms generally are rich in protein (about 50-60 percent) with high biological value and amino acid profiles very close to those required by prawns (Hepher 1989, Tidwell et al. 1997). Consequently, a system based on natural foods that allows good prawn growth might be an alternative to systems based on manufactured feeds in regions where feed is not available or do not meet nutritional requirements of prawns. Testing the Pellet-free System Aiming to verify this supposition, we carried out a preliminary trial with freshwater prawns grown without commercial feed. The test was carried out from September 2017 to March 2018 in a 40-m 2 earthen pond located at the Aquaculture Center of Pirassununga, Fisheries Institute, São Paulo, Brazil (Fig. 1) stocked with 30-d G lobal production of freshwater prawns in 2016 was 506,644 t, increasing 11 percent in three years, and corresponding to a value of US$ 4,276 million (FAO 2018), indicating that this is a growing and highly valuable industry around the world. The current Macrobrachium rosenbergii species production model is based on providing feed with medium to high protein levels, representing an important proportion of operating costs, being inversely proportional to the technification level of the system. These percentages vary from 5 percent in the USA to 52 percent in Malaysia and is 41 percent in Brazil (Rhodes 2000). Furthermore, feed provided is only partially ingested by prawns, thus increasing nitrogen and phosphorus levels in the effluent water. On the other hand, natural feed that spontaneously grows on the bottom and walls of ponds is recognized as an important source of nutrients that play important roles in the growth and health of cultivated prawns. Despite this, only recently the role of natural feed has been studied with the goal of reducing costs of manufactured feeds. Fertilization increases the availability of natural foods (Tidwell et al. 1997, Correa et al. 2003) and artificial substrate can further increase natural food production in ponds, thereby improving prawn growth and production (Tidwell et al. 2001, Uddin et al. 2009). A new method to rear marine shrimps uses Pellet-free Prawns: An Organic Approach to Produce Macrobrachium rosenbergii Helcio Luis Almeida Marques, Marcello Villar Boock, Márcia Santos Nunes Galvão, Carolina Perico Graciano and Rodrigo Hozana Ferreira FIGURE 1. A 40-m 2 pond with an earthen bottom where the trial was carried out. FIGURE 2. Periphyton growing on a piece of substrate. In Brazil, one of the major bottlenecks for the expansion of M. rosenbergii farming is the lack of a specific feed. Farmers generally use feed for marine shrimp or tilapia to rear freshwater prawns, causing low productivity and profit reduction. On the other hand, natural forage organisms generally are rich in protein (about 50-60 percent) with high biological value and amino acid profiles very close to those required by prawns. Consequently, a system based on natural foods that allows good prawn growth might be an alternative to systems based on manufactured feeds in regions where feed is not available or do not meet nutritional requirements of prawns.