Marine shrimp farming

 ( Decapods ) 

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 dry animal protein, for example krill. Nutrition and medication (such as ) fed to the brine shrimp nauplii are passed on to the shrimp that eat them.

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 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).

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 ; 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.

Semi-intensive farms do not rely on for water exchange, but use pumps and a planned pond layout. They can therefore be built above the high tide line. Pond sizes range from 2 to 30 ha; the stocking densities range from 10 to 30/square meter (100,000–300,000/ha). At such densities, artificial feeding using industrially prepared shrimp feeds and fertilizing the pond to stimulate the growth of naturally occurring organisms become a necessity. Annual yields range from 500 to 5,000 kg/ha, while production costs are in the range of US$2–6/kg live shrimp. With densities above 15 animals per square meter, aeration is often required to prevent oxygen depletion. Productivity varies depending upon water temperature, thus it is common to have larger sized shrimp in some seasons than in others.

Intensive farms use even smaller ponds () and even higher stocking densities. The ponds are actively managed: they are aerated, there is a high water exchange to remove waste products and maintain water quality, and the shrimp are fed on specially designed diets, typically in the form of formulated pellets. Such farms produce annual yields between 5,000 and 20,000 kg/ha; a few super-intensive farms can produce as much as 100,000 kg/ha. They require an advanced technical infrastructure and highly trained professionals for constant monitoring of water quality and other pond conditions; their production costs are in the range of US$4–8/kg live shrimp.

Estimates on the production characteristics of shrimp farms vary. Most studies agree that about 55–60% of all shrimp farms worldwide are extensive farms, another 25–30% are semi-intensive, and the rest are intensive farms. Regional variation is high, though, and Tacon reports wide discrepancies in the percentages claimed for individual countries by different studies.Tacon (2002), p. 29.

Most captive conditions for shrimp cause inhibitions in females that prevent them from developing mature Ovary. Even in conditions where a given species will develop ovaries and spawn in captivity, use of eyestalk ablation increases total egg production and increases the percentage of females in a given population that will participate in reproduction. Once females have been subjected to eyestalk ablation, complete ovarian development often ensues within as little as 3 to 10 days.

Artificial feeds come in the form of specially formulated, granulated pellets that disintegrate quickly. Up to 70% of such pellets are wasted, as they decay before the shrimp have eaten them. They are fed two to five times daily; the feeding can be done manually either from ashore or from boats, or using mechanized feeders distributed all over a pond. The feed conversion rate (FCR), i.e. the amount of food needed to produce a unit (e.g. one kilogram) of shrimp, is claimed by the industry to be around 1.2–2.0 in modern farms, but this is an optimum value that is not always attained in practice. For a farm to be profitable, a feed conversion rate below 2.5 is necessary; in older farms or under suboptimal pond conditions, the ratio may easily rise to 4:1.Avalle et al. (2003), p. 39. Lower FCRs result in a higher profit for the farm.

• Pacific white shrimp ( Litopenaeus vannamei, also called "whiteleg shrimp") is the main species cultivated in western countries. Native to the Pacific Ocean coast from Mexico to Peru, it grows to a size of 23 cm. L. vannamei accounts for 95% of the production in Latin America. It is easy to breed in captivity, but succumbs to the Taura disease.
• Giant tiger prawn ( P. monodon, also known as "black tiger shrimp") occurs in the wild in the Indian Ocean and in the Pacific Ocean from Japan to Australia. The largest of all the cultivated shrimp, it can grow to a length of 36 cm and is farmed in Asia. Because of its susceptibility to whitespot disease and the difficulty of breeding it in captivity, it is gradually being replaced by L. vannamei since 2001.

Together, these two species account for about 80% of the whole farmed shrimp production.Josueit (2004), p. 8. Other species being bred are:

• Western blue shrimp ( P. stylirostris) was a popular choice for shrimp farming in the western hemisphere, until the IHHN virus wiped out nearly the whole population in the late 1980s. A few stocks survived and became resistant against this virus. When it was discovered that some of these were also resistant against the Taura virus, some farms again bred P. stylirostris from 1997 on.
• Chinese white shrimp ( P. chinensis, also known as the fleshy prawn) occurs along the coast of China and the western coast of Korea and is being farmed in China. It grows to a maximum length of only 18 cm, but tolerates colder water (min. 16 °C). Once a major factor on the world market, it is today used almost exclusively for the Chinese domestic market after a disease wiped out nearly all the stocks in 1993.
• Kuruma shrimp ( P. japonicus) is farmed primarily in Japan and Taiwan, but also in Australia; the only market is in Japan, where live Kuruma shrimp reach prices of the order of US$100 per pound ($220/kg).
• Indian prawn ( P. indicus) is a native of the coasts of the Indian Ocean and is widely bred in India, Iran and the Middle East and along the African shores.
• Banana shrimp ( P. merguiensis) is another cultured species from the coastal waters of the Indian Ocean, from Oman to Indonesia and Australia. It can be grown at high densities.

Several other species of Penaeus play only a very minor role in shrimp farming. Some other kinds of shrimp also can be farmed, e.g. the "Akiami paste shrimp" or Metapenaeus spp. Their total production from aquaculture is of the order of only about 25,000 tonnes per year, small in comparison to that of the .

Yellowhead disease, called Hua leung in Thai language, affects P. monodon throughout Southeast Asia.Gulf States Marine Fisheries Commission: Non-Native Species Summaries: Yellowhead Virus (YHV), 2003. URL last accessed June 23, 2005. Data temporarily withdrawn pending review. Archived link with the data. It had been reported first in Thailand in 1990. The disease is highly contagious and leads to mass mortality within 2 to 4 days. The cephalothorax of an infected shrimp turns yellow after a period of unusually high feeding activity ending abruptly, and the then moribund shrimp congregate near the surface of their pond before dying. In OIE (2009).

Early Mortality Syndrome disease has been linked to a strain of a bacterium called Vibrio parahaemolyticus which affects the Giant Tiger Prawn and the Whiteleg Shrimp, both shrimp that are commonly farmed around the world. The strains are not harmful to humans, but are economically devastating for shrimp farmers. The spread of the bacteria is more prevalent in warmer and saltier ocean waters.

Whitespot syndrome is a disease caused by a family of related viruses. First reported in 1993 from Japanese P. japonicus cultures, In OIE (2009). it spread throughout Asia and then to the Americas. It has a wide host range and is highly lethal, leading to mortality rates of 100% within days. Symptoms include white spots on the carapace and a red hepatopancreas. Infected shrimp become lethargic before they die.Gulf States Marine Fisheries Commission: Non-Native Species Summaries: White Spot Syndrome Baculovirus Complex (WSBV), 2003. URL last accessed June 23, 2005. Data temporarily withdrawn pending review. Archived link with the data.

Taura syndrome was first reported from shrimp farms on the Taura river in Ecuador in 1992. The host of the virus causing the disease is P. vannamei, one of the two most commonly farmed shrimp. The disease spread rapidly, mainly through the shipping of infected animals and broodstock. Originally confined to farms in the Americas, it has also been propagated to Asian shrimp farms with the introduction of L. vannamei there. Birds are thought to be a route of infection between farms within one region. In OIE (2009).

Infectious hypodermal and hematopoietic necrosis (IHHN) is a disease that causes mass mortality among P. stylirostris (as high as 90%) and severe deformations in L. vannamei. It occurs in Pacific farmed and wild shrimp, but not in wild shrimp on the Atlantic Ocean coast of the Americas. In OIE (2009).

There are also a number of infections that are lethal to shrimp. The most common is vibriosis, caused by bacteria of the Vibrio species. The shrimp become weak and disoriented, and may have dark wounds on the cuticle. The mortality rate can exceed 70%. Another bacterial disease is necrotising hepatopancreatitis (NHP); symptoms include a soft exoskeleton and fouling. Most such bacterial infections are strongly correlated to stressful conditions, such as overcrowded ponds, high temperatures, and poor water quality, factors that positively influence the growth of bacteria. Treatment is done using . In Van Wyk et al. (1999). Importing countries have repeatedly placed import bans on shrimp containing various antibiotics. One such antibiotic is chloramphenicol, which has been banned in the European Union since 1994, but continues to pose problems.B. Rosenberry: The Rise and Fall of Chloramphenicol, ShrimpNews, May 2005. Archived URL last accessed February 15, 2007.

With their high mortality rates, diseases represent a very real danger to shrimp farmers, who may lose their income for the whole year if their ponds are infected. Since most diseases cannot yet be treated effectively, the industry's efforts are focused on preventing disease outbreak in the first place. Active water quality management helps avoid poor pond conditions favorable to the spread of diseases, and instead of using larvae from wild catches, specific pathogen free raised in captivity in isolated environments and certified not to carry diseases are used increasingly.Ceatech USA, Inc.: The Rationale to use SPF broodstock. Retrieved August 23, 2005. To avoid introducing diseases into such disease-free populations on a farm, there is also a trend to create more controlled environments in the ponds of semi-intensive farms, such as by lining them with plastic to avoid soil contact, and by minimizing water exchange in the ponds.McClennan (2004), p. 50.

The import prices for shrimp fluctuate wildly. In 2003, the import price per kilogram shrimp in the United States was US$8.80, slightly higher than in Japan at US$8.00. The average import price in the EU was only about US$5.00/kg; this much lower value is explained by the fact that the EU imports more coldwater shrimp (from catches) that are much smaller than the farmed warm water species, and thus attain lower prices. In addition, Mediterranean Europe prefers head-on shrimp, which weigh approximately 30% more, but have a lower unit price.Josueit (2004), p. 16.

About 75% of the world production of farmed shrimp comes from Asian countries; the two leading nations being China and Thailand, closely followed by Vietnam, Indonesia, and India. The other 25% are produced in the western hemisphere, where Latin American countries (Brazil, Ecuador, Mexico) dominate.FIGIS; FAO databases, accessed January 13, 2012. In terms of export, Thailand is by far the leading nation, with a market share of more than 30%, followed by China, Indonesia, and India, accounting each for about 10%. Other major export nations are Vietnam, Bangladesh, and Ecuador.FoodMarket: Shrimp Production; data from GlobeFish, 2001. Retrieved June 23, 2005. Thailand exports nearly all of its production, while China uses most of its shrimp in the domestic market. The only other major export nation that has a strong domestic market for farmed shrimp is Mexico.McClennan (2004), p. 70.

In the 1980s and through much of the 1990s, shrimp farming promised high profits. The investments required for extensive farms were low, especially in regions with low land prices and wages. For many tropical countries, especially those with poorer economies, shrimp farming was an attractive business, offering jobs and incomes for poor coastal populations and has, due to the high market prices of shrimp, provided many developing countries with non-negligible foreign currency earnings. Many shrimp farms were funded initially by the World Bank or substantially subsidized by local governments.Lewis et al. (2003)

In the late 1990s, the economic situation changed. Governments and farmers alike were under increasing pressure from NGOs and the consumer countries, who criticized the practices of the trade. International trade conflicts erupted, such as import bans by consumer countries on shrimp containing antibiotics, the United States' shrimp import ban against Thailand in 2004 as a measure against Thai shrimp fishers not using turtle excluder devices in their nets, or the "anti-dumping" case initiated by U.S. shrimp fishers in 2002 against shrimp farmers worldwide,B. Rosenberry: USA Shrimp Fishermen Dump Their Case on the World's Shrimp Farmers, ShrimpNews, January 2005. Archived URL last accessed February 15, 2007. which resulted two years later in the U.S. imposing antidumping of the order of about 10% against many producer countries (except China, which received a 112% duty).U.S. Department of Commerce: Amended Final Determinations and Issuance of Antidumping Duty Orders, January 26, 2005. Retrieved February 23, 2010. Diseases caused significant economic losses. In Ecuador, where shrimp farming was a major export sector (the other two are and oil), the whitespot outbreak of 1999 caused an estimated 130,000 workers to lose their jobs.McClennan (2004), p. 44. Furthermore, shrimp prices dropped sharply in 2000.B. Rosenberry: Annual Reports on World Shrimp Farming; Comments on shrimp prices in the on-line excerpts 2000–2004. Retrieved August 18, 2005. All of these factors contributed to the slowly growing acceptance by farmers that improved farming practices were needed, and resulted in tighter government regulation of the business, both of which internalized some of the that were ignored during the boom years.McClennan (2004), p. 19.

Typically, workers on a shrimp farm can get better wages than with other employment. A global estimate from one study is that a shrimp farm worker can earn 1.5–3 times as much as in other jobs;World Bank et al. (2002), p. 45. a study from India arrived at a salary increase of about 1.6, and a report from Mexico states the lowest paid job at shrimp farms was paid in 1996 at 1.22 times the average worker salary in the country.Lewis et al. (2003), p. 1.

NGOs have frequently criticized that most of the profits went to large conglomerates instead of to the local population. While this may be true in certain regions, such as Ecuador, where most shrimp farms are owned by large companies, it does not apply in all cases. For instance in Thailand, most farms are owned by small local entrepreneurs, although there is a trend to vertically integrate the industries related to shrimp farming from feed producers to food processors and trade companies. A 1994 study reported a farmer in Thailand could increase their income by a factor of ten by switching from growing rice to farming shrimp.Barraclough & Finger-Stich (1996), p. 17. An Indian study from 2003 arrives at similar figures for shrimp farming in the East Godavari district in Andhra Pradesh.Kumaran et al. (2003)

Whether the local population benefits from shrimp farming is also dependent on the availability of sufficiently trained people.Barraclough & Finger-Stich (1996), p. 15. Extensive farms tend to offer mainly seasonal jobs during harvest that do not require much training. In Ecuador, many of these positions are known to have been filled by migrant workers.McClennan (2004), p. 55. More intensive farms have a need for year-round labor in more sophisticated jobs.