Marine shrimp farming is an aquaculture business for the cultivation of marine shrimp or prawns for human consumption. Although traditional shrimp farming has been carried out in Asia for centuries, large-scale commercial shrimp farming began in the 1970s, and production grew steeply, particularly to match the market demands of the United States, Japan and Western Europe. The total global production of farmed shrimp reached more than 1.6 million tonnes in 2003, representing a value of nearly 9 billion U.S. dollars. About 75% of farmed shrimp is produced in Asia, particularly in China and Thailand. The other 25% is produced mainly in Latin America, where Brazil, Ecuador, and Mexico are the largest producers. The largest exporting nation is Thailand.
Shrimp farming has changed from traditional, small-scale businesses in Southeast Asia into a global industry. Technological advances have led to higher densities of shrimp, and broodstock is shipped worldwide. Virtually all farmed shrimp are of the family Penaeidae, and just two species – Penaeus vannamei (Pacific white shrimp) and Penaeus monodon (giant tiger prawn) – account for roughly 80% of all farmed shrimp. These industrial monocultures are very susceptible to diseases, which have caused several regional wipe-outs of farm shrimp populations. Increasing ecological problems, repeated disease outbreaks, and pressure and criticism from both NGOs and consumer countries led to changes in the industry in the late 1990s and generally stronger regulation by governments. In 1999, a program aimed at developing and promoting more sustainable farming practices was initiated, including governmental bodies, industry representatives, and environmental organizations.
History and geography Shrimp has been farmed in Southeast Asia and China for centuries, using traditional low-density methods. In Indonesia, the use of brackish water ponds () can be traced back as far as the 15th century. They used small scale ponds for monoculture or polycultured with other species, such as milkfish, or in rotation with rice, using the rice paddies for shrimp cultures during the dry season when no rice could be grown.Rönnbäck (2001), p. 1. Such cultures often were in coastal areas or on river banks. Mangrove areas were favored because of their abundant natural shrimp.Lewis et al. (2003), p. 5. Wild juvenile shrimp were trapped in ponds and reared on naturally occurring organisms in the water until they reached the desired size for harvesting.
Industrial shrimp farming can be traced to the 1930s, when Japanese agrarians spawned and cultivated Kuruma shrimp (Penaeus japonicus) for the first time. By the 1960s, a small industry had developed in Japan. Commercial shrimp farming began to grow rapidly in the late 1960s and early 1970s.
Shrimp farming was first carried out in Latin America in 1969 in Guaymas, Mexico, by . In Mexico, shrimp farming was practiced for non-commercial purposes at the , at the Scientific and Technical Research Center of the University of Sonora (CICTUS), and in Puerto Peñasco. The practice was implemented commercially in Mexico in 1985.
Worldwide, technological advances led to more intensive forms of farming, and growing market demand led to worldwide proliferation of shrimp farms, concentrated in tropical and subtropical regions. Growing consumer demand in the early 1980s coincided with faltering wild catches, creating a booming industry. Taiwan was an early adopter and a major producer in the 1980s; its production collapsed beginning in 1988 due to poor management practices and disease.ISAN (2000), pp. 9–10. In Thailand, large-scale production expanded rapidly from 1985.Hossain & Lin (2001), p. 4. In South America, Ecuador lead shrimp farming, where it expanded dramatically from 1978.McClennan (2004), p. 43. Brazil had been active in shrimp farming since 1974, but trade boomed there only in the 1990s, making the country a major producer within a few years. Today, there are marine shrimp farms in over fifty countries.
Farming methods When shrimp farming emerged to satisfy demand that had surpassed the wild fisheries' capacity, the subsistence farming methods of old were rapidly replaced by the more productive practices required to serve a global market. Industrial farming at first followed traditional methods, with so-called "extensive" farms, compensating for low density with increased pond sizes; instead of ponds of just a few hectares, ponds of sizes up to were used and huge areas of mangroves were cleared in some areas. Technological advances made more intensive practices possible that increase yield per area, helping reduce pressure to convert more land. Semi-intensive and intensive farms appeared, where the shrimp were reared on artificial feeds and ponds were actively managed. Although many extensive farms remain, new farms typically are of the semi-intensive kind.
Until the mid-1980s, most farms were stocked with young wild animals, called 'postlarvae', typically caught locally. Postlarvae fishing became an important economic sector in many countries. To counteract the depletion of fishing grounds and to ensure a steady supply of young shrimp, the industry started breeding shrimp in hatcheries.
Life cycle
Shrimp mature and breed only in a marine habitat. The females lay 100,000 to 500,000 eggs, which hatch after some 24 hours into tiny nauplii.IAA (2001), chapter 2. These nauplii feed on yolk reserves within their bodies, and then metamorphose into zoeae. Shrimp in this second larval stage feed in the wild on algae, and after a few days, morph again into mysis larvae. The mysis larvae or myses look akin to tiny shrimp, and feed on algae and zooplankton. After another three to four days, they metamorphose a final time into postlarvae: young shrimp that have adult characteristics. The whole process takes about 12 days from hatching. In the wild, postlarvae then migrate into estuaries, which are rich in nutrients and low in salinity. They migrate back into open waters when they mature.
Supply chain In shrimp farming, this life cycle occurs under controlled conditions. The reasons to do so include more intensive farming, improved size control resulting in more uniformly sized shrimp, and better predator control, but also the ability to accelerate growth and maturation by controlling the climate (especially in farms in the temperate zones, using greenhouses). There are three different stages: Hatcheries breed shrimp and produce nauplii or even postlarvae, which they sell to farms. Large shrimp farms maintain their own hatcheries and sell nauplii or postlarvae to smaller farms in the region. Nurseries grow postlarvae and accustom them to the marine conditions in the grow-out ponds. In the grow-out ponds the shrimp are grown from juveniles to marketable size, which takes between three and six months.
Most farms produce one to two harvests a year; in tropical climates, even three are possible. Because of the need for salt water, shrimp farms are located on or near a coast. Inland shrimp farms have also been tried in some regions, but the need to ship salt water and competition for land with agricultural users led to problems. Thailand banned inland shrimp farms in 1999.
Hatcheries
Small-scale hatcheries are very common throughout Southeast Asia. Often run as family businesses and using a low-technology approach, they use small tanks (less than ten tons) and often low animal densities. They are susceptible to disease, but due to their small size, they can typically restart production quickly after disinfection. The survival rate is anywhere between zero and 90%, depending on a wide range of factors, including disease, the weather, and the experience of the operator.
Greenwater hatcheries are medium-sized hatcheries using large tanks with low animal densities. To feed the shrimp larvae, an algal bloom is induced in the tanks. The survival rate is about 40%.
Galveston hatcheries (named after Galveston, Texas, where they were developed) are large-scale, industrial hatcheries using a closed and tightly controlled environment. They breed the shrimp at high densities in large (15–30 t) tanks. Survival rates vary between 0% and 80%, but typically achieve 50%.
In hatcheries, the developing shrimp are fed on a diet of algae and later also brine shrimp nauplii, sometimes (especially in industrial hatcheries) augmented by artificial diets. The diet of later stages also includes fresh or freeze-dried animal protein, for example krill. Nutrition and medication (such as antibiotics) fed to the brine shrimp nauplii are passed on to the shrimp that eat them.
Nurseries
Many farms have nurseries where the postlarval shrimp are grown into juveniles for another three weeks in separate ponds, tanks, or so-called raceways. A raceway is a rectangular, long, shallow tank through which water flows continuously. In Van Wyk et al. (1999).
In a typical nursery, there are 150 to 200 animals per square metre. They are fed on a high-protein diet for at most three weeks before they are moved to the grow-out ponds. At that time, they weigh between one and two grams. The water salinity is adjusted gradually to that of the grow-out ponds.
Farmers refer to postlarvae as "PLs", with the number of days suffixed (i.e., PL-1, PL-2, etc.). They are ready to be transferred to the grow-out ponds after their gills have branched, which occurs around PL-13 to PL-17 (about 25 days after hatching). Nursing is not absolutely necessary, but is favoured by many farms because it makes for better food utilization, improves the size uniformity, helps use the infrastructure better, and can be done in a controlled environment to increase the harvest. The main disadvantage of nurseries is that some of the postlarval shrimp die upon the transfer to the grow-out pond.
Some farms do not use a nursery, but stock the postlarvae directly in the grow-out ponds after having acclimated them to the appropriate temperature and salinity levels in an acclimation tank. Over the course of a few days, the water in these tanks is changed gradually to match that of the grow-out ponds. The animal density should not exceed 500/litre for young postlarvae and 50/liter for larger ones, such as PL-15. In Van Wyk et al. (1999).
Grow-out In the grow-out phase, the shrimp are grown to maturity. The postlarvae are transferred to ponds where they are fed until they reach marketable size, which takes about another three to six months. Harvesting the shrimp is done by fishing them from the ponds using nets or by draining the ponds. Pond sizes and the level of technical infrastructure vary.
Extensive shrimp farms using traditional low-density methods are invariably located on a coast and often in mangrove areas. The ponds range from just a few to more than 100 hectares; shrimp are stocked at low densities (2–3 animals per square metre, or 25,000/ha). The tides provide for some water exchange, and the shrimp feed on naturally occurring organisms. In some areas, farmers even grow wild shrimp by just opening the gates and impounding wild larvae. Prevalent in poorer or less developed countries where land prices are low, extensive farms produce annual yields from 50 to 500 kg/ha of shrimp (head-on weight). They have low production costs (US$1–3/kg live shrimp), are not very labor-intensive, and do not require advanced technical skills.Tacon (2002), p. 28.