Giant Freshwater Prawn (Macrobrachium rosenbergii) Farming

How the giant freshwater prawn Macrobrachium rosenbergii is farmed, from its brackish-water larval phase and freshwater grow-out to male morphotypes, carp polyculture and harvest.

Overview

The giant freshwater prawn, Macrobrachium rosenbergii (also called the giant river prawn), is one of the largest freshwater prawns and a major aquaculture species, farmed widely across India, Bangladesh, Southeast Asia and China. It is native to the tropical and subtropical Indo-Pacific, from India through Southeast Asia to northern Australia, and males can exceed 30 cm in length.

Life cycle: a two-phase requirement

A defining feature for farming is that, although juveniles and adults live in fresh water, the larvae require brackish water to develop. FAO describes the use of brackish water at about 12 ppt salinity for larval rearing; larvae metamorphose into postlarvae (which then need fresh water) over roughly 32 to 35 days after hatching. This drives a two-phase production system: a brackish-water hatchery followed by freshwater nursery and grow-out.

Hatchery and larviculture

In the hatchery, berried (egg-carrying) females release larvae into brackish water. Larvae are reared in clear-water or green-water systems and fed live Artemia nauplii together with prepared larval diets until they metamorphose to postlarvae, which are then acclimated to fresh water for nursery and grow-out.

Male morphotypes and heterogeneous growth

Males occur as three distinct morphotypes with a social hierarchy: blue-claw (BC), orange-claw (OC) and small male (SM). Blue-claw males are dominant over orange-claw males, which are dominant over small males, and this social dominance strongly influences individual growth, producing very uneven (heterogeneous) sizes within a population.

Pond grow-out

Grow-out is in freshwater ponds. Because the prawns are territorial and aggressive and grow unevenly, they are often stocked at relatively low density and frequently in polyculture with carps, which use different feeding niches and improve overall pond productivity. FAO provides stocking-density and yield tables for prawns reared in polyculture with carps and tilapias.

Harvest

Two harvest strategies are common. Cull (selective) harvesting removes only market-sized prawns and can be repeated several times so smaller animals keep growing, which suits the uneven growth of this species. Drain harvesting empties the pond for a single complete harvest. The choice depends on market, labor and pond management.