The Giant Freshwater Prawn (Scampi) Explained

The giant freshwater prawn (Macrobrachium rosenbergii), traded worldwide as “scampi”, is the largest freshwater prawn in the genus Macrobrachium, a long-clawed crustacean native to the rivers, estuaries and backwaters of South and Southeast Asia and now farmed in ponds across India. In Bengal it is known as galda chingri, and its sweet, firm flesh has made it both a festive delicacy and an export commodity.

Unlike the sea-dwelling tiger and whiteleg shrimps, the giant freshwater prawn spends most of its adult life in fresh water but needs brackish water to raise its newly hatched larvae. This unusual two-habitat life cycle shapes everything about how the animal lives in the wild and how farmers grow it in Andhra Pradesh, West Bengal, Kerala, Odisha and other states.

Key Takeaways

• The giant freshwater prawn (Macrobrachium rosenbergii) is the largest species of freshwater prawn in the world, and big males carry very long, blue-tinted second claws.
• Giant freshwater prawn larvae cannot survive in pure fresh water and need brackish water of roughly 9 to 15 parts per thousand salinity during their first weeks.
• Scampi farming in India is concentrated in the delta and coastal districts of Andhra Pradesh and West Bengal, with significant activity in Kerala, Odisha and other states.
• A typical grow-out cycle for the giant freshwater prawn lasts about four to six months, after which the prawns are harvested for local markets and for export.
• Male giant freshwater prawns grow in three distinct forms, called small males, orange claw males and blue claw males, and the dominant blue claw males suppress the growth of others.
• The giant freshwater prawn is distinct from the marine whiteleg and black tiger shrimps that dominate India’s coastal shrimp farms.

What is the giant freshwater prawn?

The giant freshwater prawn is a large decapod crustacean of the family Palaemonidae, scientifically named Macrobrachium rosenbergii, whose genus name means “long arm” because of its extremely long second pair of walking legs. These legs end in strong pincers and are the most striking feature of the animal.

The body is greenish-brown to bluish-grey, with a long, toothed rostrum curving upward from the head like a saw-edged blade. The head and chest are fused into a single section called the cephalothorax, which is covered by a hard shell, while the muscular tail, or abdomen, is the part eaten by people. The prawn has five pairs of walking legs, and the first two pairs carry small claws, while the second pair becomes enormous in adult males.

The common trade word “scampi” is used loosely in international markets, and it can confuse buyers because in Europe it is also applied to a different, marine animal, the Norway lobster. In India and Southeast Asia, however, “scampi” in the aquaculture trade almost always means the giant freshwater prawn. The species is also called the Malaysian prawn, because early hatchery work and commercial farming developed strongly in Malaysia, and it is sometimes confused in market talk with the smaller Macrobrachium malcolmsonii, a river prawn found in Indian rivers such as the Ganga and Godavari.

Where is the giant freshwater prawn found in India?

The giant freshwater prawn is found in the tidal rivers, lakes, canals and backwaters of India’s coastal belt, especially in the eastern deltas and along the west-coast backwater systems. It prefers slow-moving, warm and turbid water with muddy or vegetated bottoms.

In the wild, the species has traditionally been caught in the Ganga-Brahmaputra delta region, the Mahanadi and Chilika system, the Godavari and Krishna deltas and the backwaters of Kerala such as Vembanad Lake. Beyond India, the natural range stretches through Bangladesh, Myanmar, Thailand, Malaysia, Indonesia, the Philippines, Vietnam and northern Australia and Papua New Guinea.

Because adults need access to estuaries to release their larvae, wild stocks depend on open connections between rivers and the sea. Dams, barrages, embankments and polluted stretches can block these migrations, and many scientists consider river fragmentation, along with heavy fishing of egg-bearing females, a pressure on natural populations. The farmed animal, in contrast, is raised from hatchery-produced seed and is available in large quantity in the main producing states.

How does the life cycle of the giant freshwater prawn work?

The giant freshwater prawn has an amphidromous life cycle, meaning that adults live and grow in fresh water but must return to brackish water for the larvae to develop. This is the central biological fact behind both wild fisheries and hatcheries.

From mating to eggs

Mating happens soon after a female moults, because her shell is soft at that time. The male deposits a sperm packet beneath her body, and within hours she lays eggs that are fertilised as they pass out. The female then carries the eggs, which are orange at first and turn grey as they mature, in a brood chamber under her abdomen. A female at this stage is called “berried”. A single mature female can carry tens of thousands of eggs, with the number rising with her size.

Larval stages in brackish water

When the eggs hatch, the tiny larvae swim upside down and tail first, feeding on plankton and, in hatcheries, on newly hatched brine shrimp and prepared feed. They pass through about eleven larval stages, moulting repeatedly, and the whole larval phase takes roughly one to two months depending on temperature and feeding. During this period they need brackish water, which is why hatcheries use mixed sea and fresh water.

Post-larvae and juveniles

After the final larval moult, the animal becomes a post-larva that looks like a miniature adult. It stops being a plankton drifter, settles to the bottom, and swims toward fresh water. In nature it moves up the rivers; in aquaculture it is sold as “seed” to nursery operators and farmers. The prawn then grows rapidly through repeated moults, shedding its shell and expanding while the new shell is still soft.

What do giant freshwater prawns eat?

Giant freshwater prawns are omnivorous bottom feeders that eat a mixed diet of small animals, plant material and decaying organic matter. In rivers and lakes they pick through mud and weed for insect larvae, worms, small snails, algae, seeds and detritus.

They locate food mainly with the sensitive antennae and the chemical sensors on their mouthparts rather than by sight. Their feeding is most active at dusk and during the night, and they hide among weed, roots or debris during the day. The prawns are also cannibalistic, especially right after moulting when an individual’s shell is soft, so crowding and shortage of hiding places lead to losses in both wild and farmed conditions.

In ponds, farmers give them formulated pellet feed rich in protein, usually supplemented by natural food that grows in a well-managed pond. The feed is scattered or placed on trays, and the amount is adjusted to prawn size and water temperature.

Why do male giant freshwater prawns look so different from each other?

Male giant freshwater prawns develop into three recognisable forms because a social hierarchy controls growth, with dominant males suppressing the development of smaller ones. This pattern is called heterogeneous individual growth and is a defining challenge for farmers.

• Small males: These are the youngest and least developed males, with short, translucent claws, and they are mostly interested in avoiding fights.
• Orange claw males: These are the intermediate form with bright orange, hairier claws, and they can turn into dominant males if the space opens up.
• Blue claw males: These are the largest and most aggressive, with very long blue claws, and they hold territory and mate with females.

Blue claw males grow slowly in body weight because they spend energy on claws and defence, and their presence slows the growth of those around them. Because of this, farmers who want uniform market-sized animals often grade the stock and harvest the larger animals first, and some producers separate males and females or remove blue claw males to reduce the stunting of neighbours. Females tend to grow more slowly than males, so a mixed harvest is usually graded by size.

How is the giant freshwater prawn farmed in India?

The giant freshwater prawn is farmed in India mainly in earthen freshwater ponds, stocked with hatchery-produced post-larvae or with juveniles that have first been raised in a nursery. The pond phase lasts about four to six months before harvest.

Hatcheries and nurseries

The production chain begins in hatcheries, where berried females are held until their eggs hatch and the larvae are raised in brackish water through all larval stages. Post-larvae are then sold to nurseries, which grow them for a few weeks in small, intensively managed ponds or tanks until they become juveniles that are hardy enough for grow-out ponds. Using nursery-reared juveniles generally improves survival and shortens the time in the main pond.

Grow-out ponds

Grow-out ponds are usually rectangular and about one to a few hectares in area, with water depth around one metre or slightly more. Farmers prepare the pond by drying it, liming it to adjust soil acidity, and filling it with clean water before stocking. Because the prawns live on the bottom, farmers often add artificial shelters such as netting, bamboo or pipes to increase surface area and reduce fights.

Water quality and health

The prawns do best in warm, well-oxygenated, slightly alkaline water. Farmers monitor dissolved oxygen, pH, ammonia and temperature, and they use paddle-wheel aerators in intensive ponds. Cold winters in northern India limit the growing season because growth slows sharply in cool water. Disease management relies on clean water, good feed practice and avoiding overstocking, since stressed animals are more prone to infection.

Harvest

Harvest is usually done by repeated partial harvests using nets, which remove the large animals first, followed by a final draining of the pond. Live or fresh-chilled prawns are sold in local markets, while others are headed, graded, frozen and packed for export.

Which Indian states farm scampi and who regulates it?

Scampi farming in India is led by Andhra Pradesh and West Bengal, with additional production in Kerala, Odisha and several other states. The industry grew from the 1990s as hatchery technology spread and export demand rose.

Several public institutions support the sector. The Central Institute of Freshwater Aquaculture (CIFA) in Bhubaneswar, part of the Indian Council of Agricultural Research (ICAR), has worked on freshwater prawn breeding and farming practices. The Marine Products Export Development Authority (MPEDA), set up under a law of 1972, promotes seafood exports, including cultured freshwater prawns, and helps with quality standards and market access. State fisheries departments and agricultural universities provide training and seed supply.

Because the giant freshwater prawn is raised in fresh water, it falls outside the Coastal Aquaculture Authority, which regulates brackish-water shrimp farming along the coast. The details of licensing and land-use rules differ by state, and farmers are required to follow local water, land and environmental regulations.

Why does the giant freshwater prawn matter economically?

The giant freshwater prawn matters economically because it turns freshwater ponds into a high-value crop, supporting rural livelihoods, hatcheries, feed mills, processors and exporters. It gives farmers an option beyond carp, which generally sell at lower prices per kilogram.

Much of India’s scampi is processed and exported to markets such as the European Union, the United States, Japan and the Middle East, where it is sold whole, headless or peeled and frozen. Domestically, it is prized in Bengali cooking, where galda chingri is made into malaikari, a rich coconut milk curry, and in coastal Kerala and Andhra preparations with spices and tamarind.

The industry is also linked to employment in post-harvest work, particularly women employed in peeling and packing units. At the same time, income depends on global prices, export rules and disease control, so profits can swing from year to year.

Is farming giant freshwater prawns good for the environment?

Farming giant freshwater prawns can be reasonably low-impact when done in well-managed freshwater ponds, but it carries environmental risks if effluent, feed and land use are not managed. The honest answer is that the effect depends on scale and practice.

• Water use: Ponds need fresh water for filling and topping up, which matters in areas with groundwater stress.
• Effluent: Uneaten feed and waste can enrich discharge water with nutrients, so settling and reuse are encouraged.
• Escapes: The species is native to Indian waters, which reduces ecological risk, but hatchery stock should still be managed to protect wild genetic diversity.
• Salinity: Brackish-water hatcheries must dispose of saline water without harming nearby farmland or freshwater sources.
• Chemicals: Responsible farms limit antibiotics and unapproved chemicals, which importing countries also screen for.

Some researchers suggest that integrating prawns with rice fields, a system known as rice-prawn farming, can reduce pressure on fresh water and add income, as seen in parts of Kerala and West Bengal.

How can you recognise and cook giant freshwater prawns?

You can recognise a giant freshwater prawn by its large size, long toothed rostrum, greenish-brown shell and very long, spiny second legs, and cooks usually prize the head for its rich fat. When cooked, the shell turns orange-red, and the flesh becomes white and firm.

Prawns should be bought alive or very fresh, with a clean smell, firm texture and intact shell, because they spoil quickly after death. Many kitchens remove the vein along the back and cook the prawns briefly, since overcooking makes the flesh rubbery. Popular preparations include coconut curries, mustard-based gravies in Bengal, shallow-fried masala preparations, grills and simple boiled or steamed dishes. As with all shellfish, people with shellfish allergy should avoid it.

Bottom Line

The giant freshwater prawn is a distinctive Indian-region crustacean whose brackish-water larvae and freshwater adults make it one of the most interesting animals in Indian aquaculture. Properly managed, scampi farming offers rural income and exports, while wild stocks still need open, unpolluted rivers to breed.

Frequently Asked Questions

What is the scientific name of the giant freshwater prawn?

The scientific name of the giant freshwater prawn is Macrobrachium rosenbergii. It belongs to the family Palaemonidae, and is also called the Malaysian prawn or scampi in trade.

Is scampi the same as the giant freshwater prawn?

In Indian and Asian aquaculture trade, yes, scampi means the giant freshwater prawn. In Europe the word can also refer to the Norway lobster, a different marine animal, so buyers should check the species name.

How long does it take to grow a giant freshwater prawn?

A giant freshwater prawn usually takes about four to six months to reach market size in a pond. Growth depends on water temperature, feed, stocking density and the mix of males and females.

Why do giant freshwater prawns need brackish water?

Giant freshwater prawns need brackish water because their larvae cannot develop properly in pure fresh water. The larvae pass through about eleven stages in water of moderate salinity before turning into post-larvae that move to fresh water.

Which Indian states produce the most scampi?

Andhra Pradesh and West Bengal are the leading scampi-producing states in India. Kerala, Odisha and some other states also farm the giant freshwater prawn, though on a smaller scale.

Is the giant freshwater prawn the same as tiger shrimp?

No, the giant freshwater prawn is a different animal from the black tiger shrimp. The tiger shrimp (Penaeus monodon) is a marine species grown in coastal brackish ponds, while the giant freshwater prawn is a freshwater species with long claws.

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