Samui Wining & Dining
Life On The Farm
When prawns are farmed, they’re a lot easier to catch.


Life On The FarmPrawn – or is it shrimp? It really all depends on where you are. In some countries larger species are referred to as prawns and smaller species as shrimp. Other places, like the USA, have the differentiation the other way round. Some chefs and cookbooks say the difference is size. Small and medium shrimp are sold as, well, shrimp, while large or jumbo are sold as prawns. But this ‘rule’ doesn’t always hold! The Food and Agriculture Organisation of the United Nations has attempted to clear things up with definitions of its own. According to them, a shrimp is a saltwater crustacean and a prawn is a freshwater crustacean. So let’s leave it at that for now.


Regardless of what they’re called, they adorn just about every menu in most countries. And, nowadays, are farmed and are relatively inexpensive. They’re also particularly versatile and are used in stir-fries, deep-fried, battered, thrown into salads and sandwiches, chopped up and used in dips, tossed into curries or combined with other seafood.


Marine (saltwater) shrimp have been farmed since the 1970s and production has grown steeply to match the global market demands. In 2003, marine shrimp production reached more than 1.6 million tonnes representing nearly 9,000 million US dollars. And about 75% of those were produced in Asia, predominately in Thailand, China and Vietnam with Brazil farming the majority of the rest. Virtually all of these are of the family Penaeidae with just two species Penaeus monodon (giant tiger prawn) and Litopenaeus vannamei (pacific white shrimp) accounting for roughly 80% of all farmed marine shrimp.


However, there’s been concern over the last decade about the environmental impact of such farms. Currently 25 Thai (coastal) provinces are allowed to farm shrimp and prawns, and it’s a particularly lucrative industry. Use of saltwater on farms can degrade the soil and render the land useless. And in the Central Region of Thailand – known as the country’s rice bowl – there was a ban in the late 1990s on saltwater farming. Despite this, it still continued at the expense of rice growing, with around 40,000 rai of land being used for the purpose. (1 rai is 1600 square metres, 2 ½ rai is 1 acre). Part of the problem was that many coastal mangrove swamps had been destroyed through over-farming and people had then moved inland. Now the mangrove swamps there are being damaged and the soil eroded. Environmentalists have pointed to Bangladesh, where water from shrimp farms seeped into paddy fields, eradicating the crops. And they state that during the 1980s and 1990s around 35% of the world’s mangrove forests vanished, with shrimp farming being a major cause. A Thai government survey a few years ago estimated that there were more than 6,000 sea-prawn farms on 40,000 rai in freshwater areas. Most of these were in Nakhon Pathom Province, which is reserved for rice fields.


Freshwater prawns on the other hand had a global production in 2003 of about 280,000 tonnes. China was responsible for some 180,000 tonnes followed by Thailand and India with 35,000 tonnes each. All of the farmed freshwater prawns today belong to the genus Macrobrachium. Until the year 2000, the only species farmed was Macrobrachium rosenbergii (giant river prawn). Since then, China has begun farming the oriental river prawn in large quantities and India farms a small amount of monsoon river prawns.


In all there are around 200 species in the genus Macrobrachium and they occur throughout the tropics and subtropics on all continents except Europe. And while the giant river prawns live in turbid freshwater their larval stages require brackish water to survive. Males can reach a body size of 32 cm and females can grow to 25cm. Typically they will be harvested at around five months but that can depend on the conditions and technology utilised.


Farming of both saltwater and freshwater prawns basically uses the same methods. Hatcheries produce post-larvae which are then grown and acclimated in nurseries before being transferred into grow-out ponds. They are then fed and grown until they reach marketable size. Harvesting is done by either draining the pond and collecting them or by fishing the prawns out of the pond using nets. Due to the aggressive nature of M. rosenbergii and the hierarchy between males, stocking densities are much lower in freshwater than in saltwater farms. Intensive farming is not possible in freshwater due to increased levels of cannibalism.


Freshwater prawn farming is considered by the United Nations to have less of an ecological impact than saltwater farming. Prawns are cultured in the freshwater environment at much lower densities, meaning less concentrated waste products and a lesser danger of the ponds becoming breeding grounds for diseases. Grow-out ponds do not salinate agricultural land nor endanger mangroves. Additionally, freshwater farms are amenable to small-scale businesses run by a family. However, economics, particularly in developing countries, can dictate whether a family or co-operative actually make enough money to survive. And a worker on a shrimp farm can earn more money than on a rice farm.


In general, it has been found that shrimp farming is accepted best and introduced most easily with the greatest benefits for the local communities if the farms are owned by local people and not by large companies. Local owners have a direct interest in maintaining the environment and good relations with neighbours, and it avoids the formation of large-scale land property ownership. This is predominately the case in Thailand.


It’s an on-going debate about the environmental impact of shrimp farming and, indeed, a thousand other issues that affect the planet. What you do about it is up to you. If you continue to enjoy these tasty crustaceans then Samui is the place to be. Many of the prawns served here are actually caught out in the Gulf of Thailand. You’ll see plenty of small fishing boats returning early each morning after a night’s fishing. Shrimp are usually the main catch. Enjoy your time here, savour the local delicacies and if you do have an issue about eating prawns, don’t worry, there are plenty other Thai specialities to delight the tastebuds!


Johnny Paterson


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