Raising Prawns’ Beginner Guide
Farmed freshwater prawns belong to the genus Macrobrachium species; having the giant river prawn species (Macrobrachium rosenberii) farmed mostly. In some countries, prawn farming began with oriental river prawn (Macrobrachium nipponense) being farmed in large quantities; and in other places, farming small amount of monsoon river prawn (Macrobrachium malcolmsonii).
More and more fishpond owners have started to raise prawns, particularly the high-priced jumbo tiger prawn (known as sugpo). The reason is obvious: there’s more money in sugpo than other traditionally pond-raised fish.
It is most difficult to raise sugpo even though they are the biggest and expensive prawn; they require low salinity content in water.
It would be more profitable to raise the other type of prawns where the sugpo have difficulty growing there; hence progressive growers have themselves made arrangements to export their produce.
Species Of Prawns
Prawns have a wide range of species but are farmed in 2 ways which is freshwater prawns farming and saltwater prawns farming. The several species are cultured in freshwater and marine water;
- Giant tiger prawn (Penaeus monodon) also known as the Asian tiger shrimp, Back tiger prawn and other name – belonging to the marine crustacean widely reared for food; are aggressive molluscs that can grow to 1 foot (30.5 cm) long weighing 1 pound (454 grams).
- This prawn species is susceptible to diseases and transferring them to other shrimp species; though it can have a devastating effect on harvest period resulting in economic loss and they have a lifespan of 3 years.
- Giant river prawn (Macrobrachium rosenberii) is the most commercially cultured crustaceans in the world and considered to be a good crustacean for making money. This species requires water heating hence most farmers have resorted to using greenhouse nursery ponds which are prepared from one month before juveniles are stocked. They reach 25 – 32 cm (9.8 – 12.6 inches) in length excluding their claws.
- Oriental river prawn
- Monsoon river prawn
- Banana prawn
- Kuruma prawn
The species of prawns’ habitat varies as the freshwater genus Macrobrachium are found in lakes, rivers, swamps, irrigation ditches, canals and ponds. Most species require brackish water in their initial stages of their lifecycle and even though some complete theirs in water that is somehow connected to the sea (directly or indirectly).
Pond site and maintenance
There must be enough soil available for pond construction, whether the ponds are to be excavated or pond banks are to be erected above ground. The site should have a shape which allows you to construct regular-shaped ponds. Freshwater prawn ponds should be constructed on soil which has good water retention characteristics or where suitable materials can be economically brought onto the site to improve water retention.
Small freshwater prawn farms can be successfully maintained by unskilled labour. The amount of labour utilized on freshwater prawn farms varies considerably. One person should be able to take care of normal maintenance, including feeding but excluding harvesting, of a 1-2 ha freshwater prawn farm. Often this type of farm is family owned and operated.
Hatcheries And Grow-Out Ponds
Larval stages of freshwater prawns require brackish water for growth and survival; hatcheries do not have to be located on coastal sites. There, the necessary brackish water can be obtained by mixing locally available freshwater with seawater or brine (and sometimes artificial seawater) which has been transported to the site.
Commercial hatcheries can take 32 – 35 days to produce post larvae using 12 % of brackish water plus a mixture of live brine shrimp and egg custard for food. Hatcheries are either flow-through or use of recirculating aquaculture system; though the males are aggressive and they cannibalise each other and mature males are considerably larger than females.
It is generally recommended that freshwater prawn hatcheries should not be sited where the only source of water is surface water. How To Raise Prawns The water must also be as predator-free as possible, though standards need not be quite so high and this may be achieved by screening or by the use of well water.
In brood stocking, the females are kept in hatcheries until their eggs hatch, after which they are discarded or sold. The individual value of egg carrying females is low, especially because they are usually sent to the market after the eggs have hatched, so there is no need to economize in the number used. Berried females should be carefully selected. The berried females carrying brown to grey eggs are the best ones to bring into the hatchery, as their eggs will hatch within 2 or 3 days.
Freshwater prawns that originate from eggs that hatch early appear to have an advantage in grow-out because they are the first ones to establish themselves as dominant blue claw males.
Larval development – the first stage zoeas are very small in size about 2mm and grow through 11 larval stages, to almost 8 mm at metamorphosis into post larval forms. Individual metamorphosis can be achieved in 16 days but usually takes much longer, depending on environmental conditions.
Feed and feeding – natural food is preferred over supplementary food and due to lack of natural food and to increase the growth and quality of production supplementary food is used.
The feed include agricultural and animal husbandry by-products along with locally available cheap feeds like broken rice, tapioca root, trash fish, vegetable and animal feeds mixed in adequate proportions which is produced in pellet form. Prawns are generally fed once a day as the pellets sink in water quickly and should be intact for at least few hours till they are completely consumed by the prawns.
Water Quality And Quantity
Freshwater is normally used for rearing freshwater prawns from post larvae to market size. Prawns will tolerate partially saline water; draw good quality water from sub-surface layers, usually with freshwater overlying ore saline water. The quality of water depends on the soil materials.
In coastal areas with underlying coral rock, hatcheries can often get good quality seawater, free of pollution or harmful protozoa and bacteria. If sites with borehole seawater are not available, direct access to a sandy beach with mixed sand particle size can be selected and this type of site of a shallow beach filter can be utilized.