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Aquaculture Dictionary This Online Aquaculture Dictionary is provided as a free service by: Over 2,500 aquaculture definitions including 280 tables, 250 pictures and 120 calculations! Please read this important information before using the site: Efforts are made to ensure that all the information contained within AQUATEXT is correct. We can however accept no responsibility for the results of using the information contained within the site, whether that information is used as directed or not. Where sponsors and advertisers appear on the site, it should in no way be interpreted as an endorsement of the company's products us Once you have read the above disclaimer, please click below to enter © PLASTIC PIPE SHOP LTD 2004 to 2014 - All rights reserved.

Integrated aquaculture - aquaculture systems integrated with livestock and/or crop production.

Global harvest of aquatic organisms in million tonnes, 1950–2010, as reported by the FAO Aquaculture is the farming of, and other aquatic organisms. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with, which is the harvesting of. It is less commonly spelled aquiculture ), and is also known as aquafarming. Refers to aquaculture practiced in marine environments and in underwater habitats. According to the, aquaculture 'is understood to mean the farming of aquatic organisms including fish, molluscs, crustaceans and aquatic plants. Farming implies some form of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc.

Farming also implies individual or corporate ownership of the stock being cultivated.' The reported output from global aquaculture operations in 2014 supplied over one half of the fish and shellfish that is directly consumed by humans; however, there are issues about the reliability of the reported figures.

Further, in current aquaculture practice, products from several pounds of wild fish are used to produce one pound of a fish like. Particular kinds of aquaculture include, (such as ), and the cultivation of. Particular methods include and, both of which integrate fish farming and aquatic plant farming. 21st-century practice Harvest stagnation in and of popular marine species, combined with a growing demand for high-quality protein, encouraged aquaculturists to domesticate other marine species. At the outset of modern aquaculture, many were optimistic that a 'Blue Revolution' could take place in aquaculture, just as the of the 20th century had revolutionized agriculture. Although land animals had long been domesticated, most seafood species were still caught from the wild.

Concerned about the impact of growing demand for seafood on the world's oceans, prominent ocean explorer wrote in 1973: 'With earth’s burgeoning human populations to feed, we must turn to the sea with new understanding and new technology.” About 430 (97%) of the species cultured as of 2007 were domesticated during the 20th and 21st centuries, of which an estimated 106 came in the decade to 2007. Given the long-term importance of agriculture, to date, only 0.08% of known land plant species and 0.0002% of known land animal species have been domesticated, compared with 0.17% of known marine plant species and 0.13% of known marine animal species. Domestication typically involves about a decade of scientific research. Domesticating aquatic species involves fewer risks to humans than do land animals, which took a large toll in human lives. Most major human diseases originated in domesticated animals, including diseases such as and, that like most infectious diseases, move to humans from animals.

No human of comparable virulence have yet emerged from marine species. Biological control methods to manage parasites are already being used, such as cleaner fish (e.g. Lumpsuckers and wrasse) to control sea lice populations in salmon farming. Models are being used to help with spatial planning and siting of fish farms in order to minimize impact. The decline in wild fish stocks has increased the demand for farmed fish.

However, finding alternative sources of protein and oil for fish feed is necessary so the aquaculture industry can grow sustainably; otherwise, it represents a great risk for the over-exploitation of forage fish. Another recent issue following the banning in 2008 of organotins by the International Maritime Organization is the need to find environmentally friendly, but still effective, compounds with antifouling effects. Many new natural compounds are discovered every year, but producing them on a large enough scale for commercial purposes is almost impossible. It is highly probable that future developments in this field will rely on microorganisms, but greater funding and further research is needed to overcome the lack of knowledge in this field. Species groups.

Main article: The farming of fish is the most common form of aquaculture. It involves raising fish commercially in tanks, or ocean enclosures, usually for food. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species' natural numbers is generally referred to as a fish. Worldwide, the most important fish species used in fish farming are, in order, and. In the Mediterranean, young are netted at sea and towed slowly towards the shore. They are then interned in pens where they are further grown for the market. In 2009, researchers in Australia managed for the first time to coax to breed in landlocked tanks.

Southern bluefin tuna are also caught in the wild and fattened in grow-out sea cages in southern,. A similar process is used in the salmon-farming section of this industry; juveniles are taken from hatcheries and a variety of methods are used to aid them in their maturation. For example, as stated above, some of the most important fish species in the industry, salmon, can be grown using a cage system.

This is done by having netted cages, preferably in open water that has a strong flow, and feeding the salmon a special food mixture that aids their growth. This process allows for year-round growth of the fish, thus a higher harvest during the correct seasons. An additional method, known sometimes as sea ranching, has also been used within the industry. Sea ranching involves raising fish in a for a brief time and then releasing them into marine waters for further development, whereupon the fish are recaptured when they have matured. Crustaceans. See also: and Commercial farming began in the 1970s, and production grew steeply thereafter. Global production reached more than 1.6 million tonnes in 2003, worth about 9 billion.

About 75% of farmed shrimp is produced in Asia, in particular in China and Thailand. The other 25% is produced mainly in Latin America, where Brazil is the largest producer. Thailand is the largest exporter. Shrimp farming has changed from its traditional, small-scale form in Southeast Asia into a global industry. Technological advances have led to ever higher densities per unit area, and is shipped worldwide. Virtually all farmed shrimp are (i.e., shrimp of the ), and just two species of shrimp, the and the, account for about 80% of all farmed shrimp. These industrial are very susceptible to disease, which has decimated shrimp populations across entire regions.

Increasing problems, repeated disease outbreaks, and pressure and criticism from both and consumer countries led to changes in the industry in the late 1990s and generally stronger regulations. In 1999, governments, industry representatives, and environmental organizations initiated a program aimed at developing and promoting more practices through the program. Shares many characteristics with, including many problems with, marine shrimp farming. Unique problems are introduced by the developmental lifecycle of the main species, the.

The global annual production of freshwater prawns (excluding and ) in 2003 was about 280,000, of which China produced 180,000 tonnes followed by India and Thailand with 35,000 tonnes each. Additionally, China produced about 370,000 tonnes of. Molluscs.

See also: and Aquacultured shellfish include various, and clam species. These bivalves are filter and/or deposit feeders, which rely on ambient primary production rather than inputs of fish or other feed. As such, shellfish aquaculture is generally perceived as benign or even beneficial. Depending on the species and local conditions, bivalve molluscs are either grown on the beach, on longlines, or suspended from rafts and harvested by hand or by dredging. In May 2017 a Belgian consortium installed the first of two trial mussel farms on a wind farm in the.

Farming began in the late 1950s and early 1960s in Japan and China. Since the mid-1990s, this industry has become increasingly successful. Overfishing and have reduced wild populations to the extent that farmed abalone now supplies most abalone meat. Sustainably farmed molluscs can be certified by Seafood Watch and other organizations, including the (WWF).

WWF initiated the 'Aquaculture Dialogues' in 2004 to develop measurable and performance-based standards for responsibly farmed seafood. In 2009, WWF co-founded the with the Dutch Sustainable Trade Initiative to manage the global standards and certification programs. After trials in 2012, a commercial 'sea ranch' was set up in, Western Australia, to raise abalone.

The ranch is based on an artificial reef made up of 5000 (As of April 2016 ) separate concrete units called abitats (abalone habitats). The 900 kg abitats can host 400 abalone each. The reef is seeded with young abalone from an onshore hatchery. The abalone feed on seaweed that has grown naturally on the abitats, with the ecosystem enrichment of the bay also resulting in growing numbers of dhufish, pink snapper, wrasse, and Samson fish, among other species. Brad Adams, from the company, has emphasised the similarity to wild abalone and the difference from shore-based aquaculture.

'We're not aquaculture, we're ranching, because once they're in the water they look after themselves.' Other groups Other groups include aquatic reptiles, amphibians, and miscellaneous invertebrates, such as and. They are separately graphed at the top right of this section, since they do not contribute enough volume to show clearly on the main graph. Commercially harvested echinoderms include and. In China, sea cucumbers are farmed in artificial ponds as large as 1,000 acres (400 ha). Main aquaculture countries in 2010 In 2012, the total world production of fisheries was 158 million, of which aquaculture contributed 66.6 million tonnes, about 42%.

The growth rate of worldwide aquaculture has been sustained and rapid, averaging about 8% per year for over 30 years, while the take from wild fisheries has been essentially flat for the last decade. The aquaculture market reached $86 billion in 2009. Aquaculture is an especially important economic activity in China. Between 1980 and 1997, the Chinese Bureau of Fisheries reports, aquaculture harvests grew at an annual rate of 16.7%, jumping from 1.9 million tonnes to nearly 23 million tonnes. In 2005, China accounted for 70% of world production.

Aquaculture is also currently one of the fastest-growing areas of food production in the U.S. About 90% of all U.S. Shrimp consumption is farmed and imported. In recent years, salmon aquaculture has become a major export in southern Chile, especially in, Chile's fastest-growing city.

A report titled The State of the World Fisheries and Aquaculture released in May 2014 maintained fisheries and aquaculture support the livelihoods of some 60 million people in Asia and Africa. National laws, regulations, and management Laws governing aquaculture practices vary greatly by country and are often not closely regulated or easily traceable.

In the United States, land-based and nearshore aquaculture is regulated at the and state levels; however, no national laws govern in U.S. In June 2011, the Department of Commerce and released national aquaculture policies to address this issue and 'to meet the growing demand for healthy seafood, to create jobs in coastal communities, and restore vital ecosystems.' In 2011, Congresswoman introduced the National Sustainable Offshore Aquaculture Act of 2011 'to establish a regulatory system and research program for sustainable offshore aquaculture in the United States exclusive economic zone'; however, the bill was not enacted into law. Over-reporting China overwhelmingly dominates the world in reported aquaculture output, reporting a total output which is double that of the rest of the world put together. However, there are some historical issues with the accuracy of China's returns. In 2001, the fisheries scientists Reg Watson and expressed concerns in a letter to Nature, that China was over reporting its catch from wild fisheries in the 1990s.

They said that made it appear that the global catch since 1988 was increasing annually by 300,000 tonnes, whereas it was really shrinking annually by 350,000 tonnes. Watson and Pauly suggested this may be have been related to Chinese policies where state entities that monitored the economy were also tasked with increasing output. Also, until more recently, the promotion of Chinese officials was based on production increases from their own areas. China disputed this claim.

The official quoted Yang Jian, director general of the Agriculture Ministry's Bureau of Fisheries, as saying that China's figures were 'basically correct'. However, the accepted there were issues with the reliability of China's statistical returns, and for a period treated data from China, including the aquaculture data, apart from the rest of the world.

Main article: refers to the cultivation of marine organisms in, usually in sheltered coastal or offshore waters. The farming of marine fish is an example of mariculture, and so also is the farming of marine crustaceans (such as ), molluscs (such as ), and seaweed. Atlantic salmon and mollusk farms is for example promiment in the U.S. Mariculture may consist of raising the organisms on or in artificial enclosures such as in floating netted enclosures for salmon and on racks for oysters.

In the case of enclosed salmon, they are fed by the operators; oysters on racks filter feed on naturally available food. Abalone have been farmed on an artificial reef consuming seaweed which grows naturally on the reef units. Integrated. Main article: (IMTA) is a practice in which the byproducts (wastes) from one species are recycled to become inputs (, ) for another.

Fed aquaculture (for example, ) is combined with inorganic extractive and organic extractive (for example, ) aquaculture to create balanced systems for environmental sustainability (biomitigation), economic stability (product diversification and risk reduction) and social acceptability (better management practices). 'Multi-trophic' refers to the incorporation of species from different or levels in the same system. This is one potential distinction from the age-old practice of aquatic, which could simply be the co-culture of different fish species from the same trophic level. In this case, these organisms may all share the same biological and chemical processes, with few benefits, which could potentially lead to significant shifts in the.

Some traditional polyculture systems may, in fact, incorporate a greater diversity of species, occupying several, as extensive cultures (low intensity, low management) within the same pond. The term 'integrated' refers to the more intensive cultivation of the different species in proximity of each other, connected by nutrient and energy transfer through water. Ideally, the biological and chemical processes in an IMTA system should balance. This is achieved through the appropriate selection and proportions of different species providing different ecosystem functions. The co-cultured species are typically more than just; they are harvestable crops of commercial value.

A working IMTA system can result in greater total production based on mutual benefits to the co-cultured species and improved, even if the production of individual species is lower than in a monoculture over a short term period. Sometimes the term 'integrated aquaculture' is used to describe the integration of monocultures through water transfer. For all intents and purposes, however, the terms 'IMTA' and 'integrated aquaculture' differ only in their degree of descriptiveness., fractionated aquaculture, integrated agriculture-aquaculture systems, integrated peri-urban-aquaculture systems, and integrated fisheries-aquaculture systems are other variations of the IMTA concept. Netting materials Various materials, including, plastic-coated welded, patented products (Spectra, Thorn-D, Dyneema), and are used for netting in aquaculture fish enclosures around the world. All of these materials are selected for a variety of reasons, including design feasibility, cost, and.

Main article: Recently, copper alloys have become important netting materials in aquaculture because they are antimicrobial (i.e., they destroy, and other ) and they therefore prevent (i.e., the undesirable accumulation, adhesion, and growth of microorganisms, plants, algae, tubeworms, barnacles, mollusks, and other organisms). By inhibiting microbial growth, copper alloy aquaculture cages avoid costly net changes that are necessary with other materials. The resistance of organism growth on copper alloy nets also provides a cleaner and healthier environment for farmed fish to grow and thrive. See also: If performed without consideration for potential local environmental impacts, aquaculture in inland waters can result in more environmental damaging than, though with less waste produced on a per kg on a global scale. Local concerns with aquaculture in inland waters may include waste handling, side-effects of, competition between farmed and wild animals, and the potential introduction of, or foreign pathogens, particularly if unprocessed fish are used to feed more marketable fish. If non-local live feeds are used, aquaculture may introduce plant of animal. Improvements in methods resulting from advances in research and the availability of commercial feeds has reduced some of these concerns since their greater prevalence in the 1990s and 2000s.

Fish waste is organic and composed of nutrients necessary in all components of aquatic food webs. In-ocean aquaculture often produces much higher than normal fish waste concentrations.

The waste collects on the ocean bottom, damaging or eliminating bottom-dwelling life. Waste can also decrease levels in the, putting further pressure on wild animals. An alternative model to food being added to the ecosystem, is the installation of artificial reef structures to increase the habitat niches available, without the need to add any more than ambient feed and nutrient. This has been used in the 'ranching' of abalone in Western Australia. Fish oils. Further information: Tilapia from aquaculture has been shown to contain more fat and a much higher ratio of omega-6 to omega-3 oils.

Impacts on wild fish Some carnivorous and omnivorous farmed fish species are fed wild. Although carnivorous farmed fish represented only 13 percent of aquaculture production by weight in 2000, they represented 34 percent of aquaculture production by value.

Farming of carnivorous species like salmon and shrimp leads to a high demand for forage fish to match the nutrition they get in the wild. Fish do not actually produce omega-3 fatty acids, but instead accumulate them from either consuming that produce these fatty acids, as is the case with forage fish like and, or, as is the case with fatty, like salmon, by eating that have accumulated from microalgae. To satisfy this requirement, more than 50 percent of the world production is fed to farmed salmon. Farmed salmon consume more than they generate as a final product, although the efficiency of production is improving. To produce one pound of farmed salmon, products from several pounds of wild fish are fed to them - this can be described as the 'fish-in-fish-out' (FIFO) ratio. In 1995, salmon had a FIFO ratio of 7.5 (meaning 7.5 pounds of wild fish feed were required to produce 1 pound of salmon); by 2006 the ratio had fallen to 4.9.

Additionally, a growing share of fish oil and fishmeal come from residues (byproducts of fish processing), rather than dedicated whole fish. In 2012, 34 percent of fish oil and 28 percent of fishmeal came from residues. However, fishmeal and oil from residues instead of whole fish have a different composition with more ash and less protein, which may limit its potential use for aquaculture. As the salmon farming industry expands, it requires more wild forage fish for feed, at a time when seventy five percent of the worlds monitored fisheries are already near to or have exceeded their.

The industrial scale extraction of wild forage fish for salmon farming then impacts the survivability of the wild predator fish who rely on them for food. An important step in reducing the impact of aquaculture on wild fish is shifting carnivorous species to plant-based feeds. Salmon feeds, for example, have gone from containing only fishmeal and oil to containing 40 percent plant protein.

The USDA has also experimented with using grain-based feeds for farmed. When properly formulated (and often mixed with fishmeal or oil), plant-based feeds can provide proper nutrition and similar growth rates in carnivorous farmed fish. Another impact aquaculture production can have on wild fish is the risk of fish escaping from coastal pens, where they can interbreed with their wild counterparts, diluting wild genetic stocks. Escaped fish can become, out-competing native species.

Coastal ecosystems Aquaculture is becoming a significant threat to. About 20 percent of mangrove forests have been destroyed since 1980, partly due to. An –benefit analysis of the of shrimp aquaculture built on mangrove ecosystems found that the costs were much higher than the external benefits.

Over four decades, 269,000 hectares (660,000 acres) of Indonesian mangroves have been converted to shrimp farms. Most of these farms are abandoned within a decade because of the build-up and loss. Pollution from sea cage aquaculture are typically sited in pristine coastal ecosystems which they then pollute. A farm with 200,000 salmon discharges more fecal waste than a city of 60,000 people. This waste is discharged directly into the surrounding aquatic environment, untreated, often containing antibiotics and.' There is also an accumulation of on the (seafloor) near the salmon farms, particularly and.

In 2016, mass fish kill events impacted salmon farmers along Chile's coast and the wider ecology. Increases in aquaculture production and its associated effluent were considered to be possible contributing factors to fish and molluscan mortality. Sea cage aquaculture is responsible for nutrient enrichment of the waters in which they are established. This results from fish wastes and uneaten feed inputs. Elements of most concern are nitrogen and phosphorus which can promote algal growth, including harmful algal blooms which can be toxic to fish. Flushing times, current speeds, distance from the shore and water depth are important considerations when locating sea cages in order to minimize the impacts of nutrient enrichment on coastal ecosystems.

The extent of the effects of pollution from sea-cage aquaculture varies depending on where the cages are located, which species are kept, how densely cages are stocked and what the fish are fed. Important species-specific variables include the species' food conversion ratio (FCR) and nitrogen retention.

Studies prior to 2001 determined that the amount of nitrogen introduced as feed which is lost to the water column and seafloor as waste varies from 52 to 95%. Genetic modification A type of salmon called the AquAdvantage salmon has been for faster growth, although it has not been approved for commercial use, due to controversy. The altered salmon incorporates a growth hormone from a that allows it to reach full size in 16–28 months, instead of the normal 36 months for Atlantic salmon, and while consuming 25 percent less feed. Food and Drug Administration reviewed the AquAdvantage salmon in a draft environmental assessment and determined that it 'would not have a significant impact (FONSI) on the U.S. Ecological benefits While some forms of aquaculture can be devastating to ecosystems, such as shrimp farming in mangroves, other forms can be very beneficial.

Shellfish aquaculture adds substantial filter feeding capacity to an environment which can significantly improve water quality. A single oyster can filter 15 gallons of water a day, removing microscopic algal cells. By removing these cells, shellfish are removing nitrogen and other nutrients from the system and either retaining it or releasing it as waste which sinks to the bottom. By harvesting these shellfish the nitrogen they retained is completely removed from the system.

Raising and harvesting kelp and other macroalgae directly remove nutrients such as nitrogen and phosphorus. Repackaging these nutrients can relieve eutrophic, or nutrient-rich, conditions known for their low dissolved oxygen which can decimate species diversity and abundance of marine life.

Removing algal cells from the water also increase light penetration, allowing plants such as eelgrass to reestablish themselves and further increase oxygen levels. Aquaculture in an area can provide for crucial ecological functions for the inhabitants. Shellfish beds or cages can provide habitat structure.

This structure can be used as shelter by invertebrates, small fish or crustaceans to potentially increase their abundance and maintain biodiversity. Increased shelter raises stocks of prey fish and small crustaceans by increasing recruitment opportunities in turn providing more prey for higher trophic levels. One study estimated that 10 square meters of oyster reef could enhance an ecosystem's biomass by 2.57 kg The shellfish acting as herbivores will also be preyed on. This moves energy directly from primary producers to higher trophic levels potentially skipping out on multiple energetically-costly trophic jumps which would increase biomass in the ecosystem. Animal welfare. See also: and As with the farming of terrestrial animals, social attitudes influence the need for humane practices and regulations in farmed marine animals. Under the guidelines advised by the good animal welfare means both fitness and a sense of well being in the animal's physical and mental state.

This can be defined by the:. Freedom from hunger & thirst. Freedom from discomfort. Freedom from pain, disease, or injury. Freedom to express normal behaviour.

Freedom from fear and distress However, the controversial issue in aquaculture is whether fish and farmed marine invertebrates are actually, or have the perception and awareness to experience suffering. Although no evidence of this has been found in marine invertebrates, recent studies conclude that fish do have the necessary receptors to sense noxious stimuli and so are likely to experience states of pain, fear and stress. Consequently, welfare in aquaculture is directed at vertebrates; finfish in particular. Common welfare concerns Welfare in aquaculture can be impacted by a number of issues such as stocking densities, behavioural interactions, and. A major problem in determining the cause of impaired welfare is that these issues are often all interrelated and influence each other at different times. Optimal stocking density is often defined by the of the stocked environment and the amount of individual space needed by the fish, which is very species specific. Although behavioural interactions such as may mean that high stocking densities are beneficial to some species, in many cultured species high stocking densities may be of concern.

Crowding can constrain normal swimming behaviour, as well as increase aggressive and competitive behaviours such as cannibalism, feed competition, territoriality and dominance/subordination hierarchies. This potentially increases the risk of tissue damage due to abrasion from fish-to-fish contact or fish-to-cage contact. Fish can suffer reductions in food intake and. In addition, high stocking densities can result in water flow being insufficient, creating inadequate oxygen supply and waste product removal. Is essential for fish respiration and concentrations below critical levels can induce stress and even lead to.

Ammonia, a nitrogen excretion product, is highly toxic to fish at accumulated levels, particularly when oxygen concentrations are low. Many of these interactions and effects cause stress in the fish, which can be a major factor in facilitating fish disease. For many parasites, infestation depends on the host's degree of mobility, the density of the host population and vulnerability of the host's defence system. Sea lice are the primary parasitic problem for finfish in aquaculture, high numbers causing widespread skin erosion and haemorrhaging, gill congestion, and increased mucus production. There are also a number of prominent viral and bacterial that can have severe effects on internal organs and nervous systems. Improving welfare The key to improving welfare of marine cultured organisms is to reduce stress to a minimum, as prolonged or repeated stress can cause a range of adverse effects. Attempts to minimise stress can occur throughout the culture process.

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During grow out it is important to keep stocking densities at appropriate levels specific to each species, as well as separating size classes and grading to reduce aggressive behavioural interactions. Keeping nets and cages clean can assist positive water flow to reduce the risk of water degradation. Not surprisingly disease and parasitism can have a major effect on fish welfare and it is important for farmers not only to manage infected stock but also to apply disease prevention measures. However, prevention methods, such as vaccination, can also induce stress because of the extra handling and injection. Other methods include adding antibiotics to feed, adding chemicals into water for treatment baths and biological control, such as using to remove lice from farmed salmon. Many steps are involved in transport, including capture, food deprivation to reduce faecal contamination of transport water, transfer to transport vehicle via nets or pumps, plus transport and transfer to the delivery location. During transport water needs to be maintained to a high quality, with regulated temperature, sufficient oxygen and minimal waste products.

In some cases may be used in small doses to calm fish before transport. Aquaculture is sometimes part of an environmental rehabilitation program or as an aid in conserving endangered species. Prospects Global are in decline, with valuable habitat such as in critical condition.

The aquaculture or of fish, like, does not help the problem because they need to eat products from other fish, such as and. Studies have shown that has major on wild salmon, as well as the that need to be caught to feed them. Fish that are higher on the are less efficient sources of food energy. Apart from fish and shrimp, some aquaculture undertakings, such as seaweed and filter-feeding bivalve mollusks like, and, are relatively benign and even environmentally restorative.

Filter-feeders filter pollutants as well as nutrients from the water, improving water quality. Extract nutrients such as inorganic nitrogen and directly from the water, and filter-feeding can extract nutrients as they feed on particulates, such as and. Some profitable aquaculture cooperatives promote sustainable practices.

New methods lessen the risk of biological and chemical through minimizing fish stress, fallowing netpens, and applying. Are being used more and more to reduce use for disease control. Onshore recirculating aquaculture systems, facilities using techniques, and properly sited facilities (for example, offshore areas with strong currents) are examples of ways to manage negative environmental effects. (RAS) recycle water by circulating it through filters to remove fish waste and food and then recirculating it back into the tanks.

This saves water and the waste gathered can be used in or, in some cases, could even be treated and used on land. While RAS was developed with freshwater fish in mind, scientist associated with the have found a way to rear saltwater fish using RAS in low-salinity waters. Although saltwater fish are raised in off-shore cages or caught with nets in water that typically has a salinity of 35 (ppt), scientists were able to produce healthy pompano, a saltwater fish, in tanks with a salinity of only 5 ppt. Commercializing low-salinity RAS are predicted to have positive environmental and economical effects. Unwanted nutrients from the fish food would not be added to the ocean and the risk of transmitting diseases between wild and farm-raised fish would greatly be reduced. The price of expensive saltwater fish, such as the pompano and combia used in the experiments, would be reduced.

However, before any of this can be done researchers must study every aspect of the fish's lifecycle, including the amount of ammonia and nitrate the fish will tolerate in the water, what to feed the fish during each stage of its lifecycle, the that will produce the healthiest fish, etc. Some 16 countries now use for aquaculture, including China, and the United States. In California, for example, 15 fish farms produce tilapia, bass, and catfish with warm water from underground.

This warmer water enables fish to grow all year round and mature more quickly. Collectively these California farms produce 4.5 million kilograms of fish each year.

See also.