Malacostracans · Decapoda · Palaemonidae

Giant River Prawn

Macrobrachium rosenbergii

Least Concern

The species is abundant and widely distributed; it faces no significant short-term risk. See full glossary

The giant freshwater prawn, also known as the Malaysian prawn or the blue prawn, is a prawn of the family Palaemonidae in the order Decapoda that lives in tropical Asia in the Indomalayan realm, from the Indian subcontinent to northern Australia and New Guinea. It is also found in several countries of Latin America and Africa through aquaculture. It feeds on parasites and dead tissue. Farming it can have a negative impact on waterways. It can grow to more than 30 cm. It is the largest farmed prawn in the world. It lives in fresh water, but in its larval stage it requires brackish water. It often lives in very turbid water.

Size

20 cm – 32 cm

Lifespan

3 years

Diet

Omnivore

Combines animal and plant food depending on availability.

Activity

Nocturnal

Active mainly at night.

Social structure

Colony

Lives in large concentrations, often for breeding reasons.

Sighting difficulty

Easy

FreshwaterOmnivore Nocturnal Colonial Freshwater Crustacean

32countries 12parks

Fun facts

The males form three castes of different appearance and behaviour: the dominant blue-clawed males, the orange-clawed males and the small transparent ones, and an individual can change caste over its life.
Its larvae die in pure fresh water: they need salinity to complete their metamorphosis, something that held back its farming for decades until it was discovered in the 1960s.
Its males come in three distinct morphotypes that coexist in the same population, and they are not age stages but alternative strategies.
The blue-claw male is the dominant one: huge, territorial, with extremely long chelae, he defends a territory and monopolises freshly moulted females.
The orange-claw male is a contender in transition, and the small-claw male practises sneaking: he slips in and fertilises females while the dominant male is off guard.
A male can change morphotype over the course of his life, and the presence of a dominant male holds back the development of the others.
It is the most farmed freshwater prawn in the world, with major production in South-east Asia and Latin America.
Its larvae do not survive in fresh water: they need brackish water, a requirement that means its farming demands hatcheries with controlled salinity.
Its chelae can exceed the length of the entire body.

Life cycle & biology

Skeleton type: Invertebrate - chitin exoskeleton (crustacean)
Habitat & environment: Tropical rivers, lagoons and estuaries, with larvae that need brackish water

Sources consulted: https://es.wikipedia.org/wiki/Macrobrachium_rosenbergii