REPRODUCTIVE MECHANISMS IN THE GIANT FRESHWATERREPRODUCTIVE MECHANISMS IN THE GIANT FRESHWATER

The giant freshwater prawn, Macrobrachium rosenbergii, is a commercially important species of crustacean cultured extensively throughout Southeast Asia. In Vietnam, where Japan International Research Center for Agricultural Sciences (JIRCAS) is currently implementing a comprehensive project entitled “Evaluation and improvement of farming systems combining agriculture, animal husbandry and fisheries in the Mekong Delta,” M. rosenbergii is considered to be an important target species by the Vietnamese Government, and its aquaculture is being actively promoted. Farmers have traditionally depended on wild sources to obtain seed for aquaculture but are now faced with dwindling resources and a shortage of natural spawners. Development of improved means of artificial seed production for M. rosenbergii in the Mekong Delta is thus essential. JIRCAS is currently implementing basic studies on the reproductive endocrinology of M. rosenbergii as part of the Mekong Delta project. Biochemical and molecular biological research is being conducted both at the project site, Cantho University’s College of Agriculture, in Cantho Province, Vietnam, in collaboration with Vietnam counterparts, and on JIRCAS Tsukuba premises. As part of our on-site studies in Vietnam, we are conductingan assessment of typical feeds utilized in freshwater prawn culture in Vietnam, and evaluating the effects of this feed on reproduction. This research is expected to be relevant in controlling female reproduction in captivity and improving seed production technology.
source:Wei-Jun YangDo Thi Thanh Huong, Masachika Maeda,
Japan International Research Center for Agricultural Sciences

Scope for Fresh Water Prawn Culture

Considering the high export potential, the giant fresh water prawn, Macrobrachium rosenbergii, the scampi, enjoys immense potential for culture in India. About 4 million ha. of impounded freshwater bodies in the various states of India, offer great potential for fresh water prawn culture. Scampi can be cultivated for export through monoculture in existing as well as new ponds or with compatible freshwater fishes in existing ponds. It is exported to EEC countries and USA. Since the world market for scampi is expanding with attractive prices, there is great scope for scampi production and export.

Location

Giant freshwater prawns are native to the fresh and brackish waters across South and Southeast Asia, parts of Oceania, and the Western Pacific Islands.

The main sources of giant freshwater prawns are China, Bangladesh, Taiwan, Indonesia and Thailand. Prawns sold in the U.S. market are primarily from Bangladesh and China.

Diseases

Diseases so far do not appear to be a significant problem in the production of freshwater prawns, but as densities are increased to improve production, disease problems are bound to become more prevalent. One disease you may encounter is "blackspot" or "shell disease," which is caused by bacteria that break down the outer skeleton. Usually it follows physical damage and can be avoided by careful handling. At other times, algae or insect eggs may be present on the shell. This condition is not a disease, but rather an indication of slow growth, and is eliminated when the prawn molts.

Identification of Male and Female

The sexes are separate and the males are larger than females. The body can be divided into cephalothorox and abdomen and there are about 20 appendages of which six pairs are located on the head portion of the cephalothorox eight pairs on the chest portion of the cephalothorax, and the rest on the abdomen. These appendages are used for various purposes such as sensory, touching, cutting and grinding feed, capture of food and handling, waking, swimming and propulsion etc. The Male have a large cephalothorax and narrow abdomen. The second pair of chelate legs of male are long, robust and large. They have a gonopore at the base of the fifth pair of legs and an appendex masculine on the endopod of the second pair of swimming legs.

Culture of Fresh water prawn is Profitable Business

Culture of freshwater prawn is profitable and can be adopted throughout the asia pecific region, even in land-locked states, which are unsuitable for brakishwater shrimp farming. The giant freshwater prawn, known scientifically as Machrobrachium rosenbergi popularly known as scampi is now popularly cultivated in many parts of the region, in almost all the states. From a meagre production and export of about 2200mt during the early ninetie's (1994-95) it has seen a sevenfold increase in 2004-2005 with 15000 tonnes. The cause of successfully culture of freshwater prawn are many, such as better FCR and growth, diease resistance, demand in export market and amenability to cultivate, both in mono culture and in combination with carps. In India the development, hatchery production of larvae and post larval rearing, and grow-out culture have spurred an unprecedented increase in its adoption by farmers, and entrepreneurs.

Fresh water Prawn as an Aquaculture Product

The so-called giant freshwater prawn, Macrobrachium rosenbergii, is widely distributed in the Indo-Pacific region, ranging from Australia to New Guinea to Indus River delta. This species has emerged in the last few years as one of the aquatic animals having a very high potential for aquaculture.

This is based on a number of advantages of this species over many other crustaceans. It adapts to a relatively wide range of temperature from a minimum of 15 to a maximum of 35°C. This species has a relatively short larval life. It is also a fast growing species. Fast growing individuals reach market size in about 7–8 months, and the meat is of high quality in terms of tests and texture.

Food is normally the largest single item in the running expenditure of a prawn hatchery or prawn farm. If prawns are held in artificial confinement where natural food are absent or limited, an external food source should be added. For example, the external food of freshwater prawn larvae that are held in tanks may consist of live food (nauplii of brine shrimp) or artificial food (fish egg, fish flesh, formulated feeds, etc.)

The production of freshwater prawn stocked in pond depends on the ability of the environment to produce natural food. Various factors such as soil and water fertility, water temperature and intensity of solar radiation affect the production level of natural food in the pond. However, for maximum rate of performance, the supplemental feeding programme is supposed to be important. Hence, the knowledge of nutrient requirements, the preparation of suitable feeds from the local available ingredients, feeding techniques, and the cost effectiveness of prepared feeds is of paramount importance to commercial success.