Fish farming is the principal form of aquaculture Aquaculture is the farming of freshwater and saltwater organisms including molluscs, crustaceans and aquatic plants. Unlike fishing, aquaculture, also known as aquafarming, implies the cultivation of aquatic populations under controlled conditions. Mariculture refers to aquaculture practiced in marine environments. Particular kinds of aquaculture, while other methods may fall under mariculture Mariculture is a specialized branch of aquaculture involving the cultivation of marine organisms for food and other products in the open ocean, an enclosed section of the ocean, or in tanks, ponds or raceways which are filled with seawater. An example of the latter is the farming of marine fish, including finfish and shellfish e.g.prawns, or. It involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases juvenile fish into the wild for recreational fishing Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival or to supplement a species' natural numbers is generally referred to as a fish hatchery A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish or poultry. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled conditions; alternatively, it may be for economic reasons. The most important fish species raised by fish farms are, in order, salmon Salmon is the common name for several species of fish of the family Salmonidae. Several other fish in the family are called trout; the difference is often attributed to the migratory life of the salmon as compared to the residential behaviour of trout, a distinction that holds true for the Salmo genus. Salmon live in both the Atlantic and Pacific, carp Carp is a common name for various species of an oily freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. Some consider all cyprinid fishes carp, and the family Cyprinidae itself is often known as the carp family. In colloquial use, however, carp usually refers only to several larger cyprinid species such, tilapia Tilapia is the common name for nearly a hundred species of cichlid fish from the tilapiine cichlid tribe. Tilapia inhabit a variety of fresh water habitats including shallow streams, ponds, rivers, lakes, and estuaries. Most tilapia are omnivorous with a preference for soft aquatic vegetation and detritus. Historically they have been of major, catfish Catfish are a very diverse group of bony fish. Named for their prominent barbels, which resemble a cat's whiskers (though not prominent in all members of this order), catfish range in size and behavior from the heaviest, the Mekong giant catfish from Southeast Asia and the longest, the wels catfish of Eurasia, to detritivores (species that eat and cod Cod is the common name for the genus of fish Gadus, belonging to the family Gadidae, and is also used in the common name of a variety of other fishes. Cod is a popular food fish with a mild flavor, low fat content and a dense white flesh that flakes easily. Cod livers are processed to make cod liver oil, an important source of Vitamin A, Vitamin D.

Increasing demands on wild fisheries A fishery is an area with an associated fish or aquatic population which is harvested for its commercial value. Fisheries can be marine or freshwater. They can also be wild or farmed. This article is an overview of the habitats occupied by the worlds' wild fisheries, and the human impacts on those habitats by commercial fishing Commercial fishing is the activity of capturing fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions. Large scale commercial fishing is also known has caused widespread overfishing Ultimately overfishing may lead to resource depletion in cases of subsidised fishing, low biological growth rates and critical low biomass levels . Particularly, overfishing of sharks has led to the upset of entire marine ecosystems. Fish farming offers an alternative solution to the increasing market A market is any one of a variety of different systems, institutions, procedures, social relations and infrastructures whereby persons trade, and goods and services are exchanged, forming part of the economy. It is an arrangement that allows buyers and sellers to exchange things. Markets vary in size, range, geographic scale, location, types and demand for fish A fish is any aquatic vertebrate animal that is typically ectothermic , covered with scales, and equipped with two sets of paired fins and several unpaired fins. Fish are abundant in the sea and in fresh water, with species being known from mountain streams (e.g., char and gudgeon) as well as in the deepest depths of the ocean (e.g., gulpers and and fish protein Proteins are organic compounds made of amino acids arranged in a linear chain polymer and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the genetic code specifies.

Contents

Major categories of fish farms

There are two kinds of aquaculture: extensive aquaculture based on local photosynthetical production and intensive aquaculture, in which the fish are fed with external food supply. The management of these two kinds of aquaculture systems are completely different.

Extensive aquaculture

Aqua-Boy, a Norwegian live fish carrier used to service the Marine Harvest fish farms on the West coast of Scotland

Limiting for growth here is the available food supply by natural sources, commonly zooplankton Zooplankton are the heterotrophic type of plankton. Plankton are organisms drifting in the water column of oceans, seas, and bodies of fresh water. The name of zooplankton is derived from the Greek zoon (ζῴον), meaning "animal", and planktos (πλαγκτος), meaning "wanderer" or "drifter". Many zooplankton feeding on pelagic Any water in the sea that is not close to the bottom is in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means open sea algae Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in land plants. For that reason they are or benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos. They generally live in close relationship with the substrate bottom; many such organisms are permanently attached to the bottom animals, such as crustaceans Crustaceans are a very large group of arthropods, comprising almost 52,000 described species , and are usually treated as a subphylum . They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles. The majority of them are aquatic, living in either marine or fresh water environments, but a few groups have and mollusks Molluscs[note 1] are animals belonging to the phylum Mollusca. There are around 93,000 recognized extant species, making it the largest marine phylum with about 23% of all named marine organisms. Representatives of the phylum live in a huge range of habitats including marine, freshwater, and terrestrial environments. Molluscs are a highly diverse. Tilapia Tilapia is the common name for nearly a hundred species of cichlid fish from the tilapiine cichlid tribe. Tilapia inhabit a variety of fresh water habitats including shallow streams, ponds, rivers, lakes, and estuaries. Most tilapia are omnivorous with a preference for soft aquatic vegetation and detritus. Historically they have been of major species filter feed directly on phytoplankton Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words phyton, or "plant", and πλαγκτος , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, they may, which makes higher production possible. The photosynthetical production can be increased by fertilizing Fertilizers are chemical compounds applied to promote plant and fruit growth. Fertilizers are usually applied either through the soil or, by foliar feeding (for uptake through leaves) the pond water with artificial fertilizer mixtures, such as potash Potash has been used since antiquity in the manufacture of glass, soap, and soil fertilizer. Potash is important for agriculture because it improves water retention, yield, nutrient value, taste, colour, texture and disease resistance of food crops. It has wide application to fruit and vegetables, rice, wheat and other grains, sugar, corn,, phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15. The name comes from the Greek: φώς (meaning "light") and φόρος (meaning "bearer"). A multivalent nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate rocks, nitrogen Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674µ. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere and micro-elements. Because most fish are carnivorous A carnivore , meaning 'meat eater' (Latin carne meaning 'flesh' and vorare meaning 'to devour'), is any animal with a diet consisting mainly of meat, whether it comes from animals living (predation) or dead (scavenging), they occupy a higher place in the trophic chain In ecology, trophic dynamics is the system of trophic levels , which describe the position that an organism occupies in a food chain — what an organism eats, and what eats the organism and therefore only a tiny fraction of primary photosynthetic production (typically 1%) will be converted into harvest-able fish. As a result, without additional feeding the fish harvest will not exceed 200 kilograms of fish per hectare A hectare is a unit of area equal to 10,000 square metres (107,639 sq ft), or one square hectometre (100 metres, squared), and commonly used for measuring land area per year, equivalent to 1% of the gross photosynthetic production.

A second point of concern is the risk of algal blooms An algal bloom is a rapid increase in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration of the water resulting from the high density of pigmented cells. When temperatures, nutrient supply and available sunlight are optimal for algal growth, algae multiply their biomass at an exponential rate, eventually leading to an exhaustion of available nutrients and a subsequent die-off. The decaying algal biomass will deplete the oxygen in the pond water because it blocks out the sun and pollutes it with organic An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic. The division between "organic" and " and inorganic Traditionally, inorganic compounds are considered to be of a mineral, not biological, origin. Complementarily, most organic compounds are traditionally viewed as being of biological origin. Over the past century, the precise classification of inorganic vs organic compounds has become less important to scientists, primarily because the majority of solutes (such as ammonium ions), which can (and frequently do) lead to massive loss of fish.

In order to tap all available food sources in the pond, the aquaculturist will choose fish species which occupy different places in the pond ecosystem, e.g., a filter algae feeder such as tilapia Tilapia is the common name for nearly a hundred species of cichlid fish from the tilapiine cichlid tribe. Tilapia inhabit a variety of fresh water habitats including shallow streams, ponds, rivers, lakes, and estuaries. Most tilapia are omnivorous with a preference for soft aquatic vegetation and detritus. Historically they have been of major, a benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos. They generally live in close relationship with the substrate bottom; many such organisms are permanently attached to the bottom feeder such as carp Carp is a common name for various species of an oily freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. Some consider all cyprinid fishes carp, and the family Cyprinidae itself is often known as the carp family. In colloquial use, however, carp usually refers only to several larger cyprinid species such or catfish Catfish are a very diverse group of bony fish. Named for their prominent barbels, which resemble a cat's whiskers (though not prominent in all members of this order), catfish range in size and behavior from the heaviest, the Mekong giant catfish from Southeast Asia and the longest, the wels catfish of Eurasia, to detritivores (species that eat and a zooplankton Zooplankton are the heterotrophic type of plankton. Plankton are organisms drifting in the water column of oceans, seas, and bodies of fresh water. The name of zooplankton is derived from the Greek zoon (ζῴον), meaning "animal", and planktos (πλαγκτος), meaning "wanderer" or "drifter". Many zooplankton feeder (various carps) or submerged weeds feeder such as grass carp The Grass Carp is a herbivorous, freshwater fish species of family Cyprinidae, and the only species of the genus Ctenopharyngodon. It is cultivated in China for food but was introduced in Europe and the United States for aquatic weed control. It is a large cyprind native to Eastern Asia, with a native range from Northern Vietnam to the Amur River.

Despite these limitations significant fish farming industries use these methods. In the Czech Republic The Czech Republic /ˈtʃɛk rɨˈpʌblɪk/ (Czech: Česká republika, pronounced [ˈtʃɛskaː ˈrɛpuˌblɪka] ( listen)), short form Czechia (Czech: Česko [ˈtʃɛskɔ]), is a landlocked country in Central Europe. The country borders Poland to the northeast, Germany to the west and northwest, Austria to the south and Slovakia to the east. The thousands of natural and semi-natural ponds are harvested each year for trout and carp. The large ponds around Trebon were built from around 1650 and are still in use.

Sources

Intensive aquaculture

In these kinds of systems fish production per unit of surface can be increased at will, as long as sufficient oxygen Oxygen (pronounced /ˈɒksɨdʒɨn/, from the Greek roots ὀξύς (acid, literally "sharp," from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly reactive, fresh water and food are provided. Because of the requirement of sufficient fresh water, a massive water purification Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from raw water. The goal is to produce water fit for a specific purpose. Most water is purified for human consumption but water purification may also be designed for a variety of other purposes, including to meet the requirements of medical, system must be integrated in the fish farm. A clever way to achieve this is the combination of hydroponic Hydroponics is a method of growing plants using mineral nutrient solutions, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, or mineral wool horticulture Hortoculture is the industry and science of plant cultivation. Hortoculturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant breeding and genetic engineering, plant biochemistry, and plant physiology. The work particularly involves fruits, berries, nuts, vegetables, flowers, trees, shrubs, and water treatment Water treatment describes those processes used to make water more acceptable for a desired end-use. These can include use as drinking water, industrial processes, medical and many other uses. The goal of all water treatment process is to remove existing contaminants in the water, or reduce the concentration of such contaminants so the water, see below. The exception to this rule are cages which are placed in a river or sea, which supplements the fish crop with sufficient oxygenated water. Some environmentalists Environmentalism is a broad philosophy and social movement regarding concerns for environmental conservation and improvement of the environment. Environmentalism and environmental concerns may be represented with the color green object to this practice.

Expressing eggs from a female rainbow trout

The cost of inputs per unit of fish weight is higher than in extensive farming, especially because of the high cost of fish food Fish food is plant or animal material intended for consumption by pet fish kept in aquariums or ponds. Fish foods normally contain macro nutrients, trace elements and vitamins necessary to keep captive fish in good health. Approximately 80% of fishkeeping hobbyists feed their fish exclusively prepared foods that most commonly are produced in flake,, which must contain a much higher level of protein Proteins are organic compounds made of amino acids arranged in a linear chain polymer and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the genetic code specifies (up to 60%) than, e.g., cattle Cattle, colloquially referred to as cows, are domesticated ungulates, a member of the subfamily Bovinae of the family Bovidae. They are raised as livestock for meat , dairy products (milk), leather and as draft animals (pulling carts, plows and the like). In some countries, such as India, they are honored in religious ceremonies and revered. It is food and a balanced amino acid In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent. In the alpha amino acids, the amino and carboxylate groups are attached to composition as well. However, these higher protein level requirements are a consequence of the higher food conversion efficiency (FCR -- kg of feed per kg of animal produced) of aquatic animals. Fish like salmon have FCR's in the 1.1 kg of feed per kg of salmon range whereas chickens are in the 2.5 kg of feed per kg of chicken range. Fish don't have to stand up or keep warm and this eliminates a lot of carbohydrates and fats in the diet, required to provide this energy. This frequently is offset by the lower land costs and the higher productions which can be obtained due to the high level of input control.

Essential here is aeration of the water, as fish need a sufficient oxygen level for growth. This is achieved by bubbling, cascade flow or aqueous oxygen. Catfish, Clarias ssp. can breathe atmospheric air and can tolerate much higher levels of pollutants than, e.g., trout or salmon, which makes aeration and water purification less necessary and makes Clarias species especially suited for intensive fish production. In some Clarias farms about 10% of the water volume can consist of fish biomass.

Especially when fish densities are high, the risk of infections by parasites like fish lice, fungi (Saprolegnia ssp.), intestinal worms (such as nematodes or trematodes), bacteria (e.g., Yersinia ssp, Pseudomonas ssp.), and protozoa (such as Dinoflagellates) is similar to animal husbandry. These problems are similar to what is found in animal husbandry of all types. However, animal husbandry is a larger and more technologically mature area of human agriculture and better solutions to pathogen problem exist. Intensive aquaculture does have to provide adequate water quality (oxygen, ammonia, nitrite, etc.) levels to minimize stress, which makes the pathogen problem more difficult. This means, intensive aquaculture requires tight monitoring and a high level of expertise of the fish farmer.

Controlling roes manually

Very high intensity recycle aquaculture systems (RAS), where there is complete control over all the production parameters are being used for high value species. By recycling the water, very little water is used per unit of production. However, the process does have high capital and operating costs. The higher cost structures mean than RAS is only economical for high value products like broodstock for egg production, fingerlings for net pen aquaculture operations, sturgeon production, research animals and some special niche markets like live fish.[1] [2]

Raising ornamental cold water fish (goldfish or koi), although theoretically much more profitable due to the higher income per weight of fish produced, has never been successfully carried out until very recently. The increased incidences of dangerous viral diseases of koi Carp, together with the high value of the fish has led to initiatives in closed system koi breeding and growing in a number of countries. Today there are a few commercially successful intensive koi growing facilities in the UK, Germany and Israel.

Some producers have adapted their intensive systems in an effort to provide consumers with fish that do not carry dormant forms of viruses and diseases.

Specific types of fish farms

Within intensive and extensive aquaculture methods there are numerous specific types of fish farms, each has benefits and applications unique to its design.

Integrated recycling systems

One of the largest problems with freshwater aquaculture is that it can use a million gallons of water per acre (about 1 m³ of water per m²) each year. Extended water purification systems allow for the reuse (recycling) of local water.

The largest-scale pure fish farms use a system derived (admittedly much refined) from the New Alchemists in the 1970s. Basically, large plastic fish tanks are placed in a greenhouse. A hydroponic bed is placed near, above or between them. When tilapia are raised in the tanks, they are able to eat algae, which naturally grows in the tanks when the tanks are properly fertilized.

The tank water is slowly circulated to the hydroponic beds where the tilapia waste feeds a commercial plant crops. Carefully cultured microorganisms in the hydroponic bed convert ammonia to nitrates, and the plants are fertilized by the nitrates and phosphates. Other wastes are strained out by the hydroponic media, which doubles as an aerated pebble-bed filter.

This system, properly tuned, produces more edible protein per unit area than any other. A wide variety of plants can grow well in the hydroponic beds. Most growers concentrate on herbs (e.g. parsley and basil), which command premium prices in small quantities all year long. The most common customers are restaurant wholesalers.

Since the system lives in a greenhouse, it adapts to almost all temperate climates, and may also adapt to tropical climates. The main environmental impact is discharge of water that must be salted to maintain the fishes' electrolyte balance. Current growers use a variety of proprietary tricks to keep fish healthy, reducing their expenses for salt and waste water discharge permits. Some veterinary authorities speculate that ultraviolet ozone disinfectant systems (widely used for ornamental fish) may play a prominent part in keeping the Tilapia healthy with recirculated water.

A number of large, well-capitalized ventures in this area have failed. Managing both the biology and markets is complicated.

Reference: Freshwater Aquaculture: A Handbook for Small Scale Fish Culture in North America, by William McLarney

Irrigation ditch or pond systems

These use irrigation ditches or farm ponds to raise fish. The basic requirement is to have a ditch or pond that retains water, possibly with an above-ground irrigation system (many irrigation systems use buried pipes with headers.) Using this method, one can store one's water allotment in ponds or ditches, usually lined with bentonite clay. In small systems the fish are often fed commercial fish food, and their waste products can help fertilize the fields. In larger ponds, the pond grows water plants and algae as fish food. Some of the most successful ponds grow introduced strains of plants, as well as introduced strains of fish.

Control of water quality is crucial. Fertilizing, clarifying and pH control of the water can increase yields substantially, as long as eutrophication is prevented and oxygen levels stay high.Yields can be low if the fish grow ill from electrolyte stress.

Cage system

Giant gourami is often raised in cages in central Thailand

Fish cages are placed in open water resources to contain and protect fish until they can be harvested. They can be constructed of a wide variety of components. Fish are stocked in cages, artificially fed, and harvested when they reach market size. A few advantages of fish farming with cages are that many types of waters can be used (rivers, lakes, filled quarries, etc.), many types of fish can be raised, and fish farming can co-exist with sport fishing and other water uses. Cage farming of fishes in open seas is also gaining popularity. Concerns of disease, poaching, poor water quality, etc., lead some to believe that in general, pond systems are easier to manage and simpler to start. Also, past occurrences of cage-failures leading to escapes, have raised concern regarding the culture of non-native fish species in open-water cages. Even though the cage-industry has made numerous technological advances in cage construction in recent years, the concern for escapes remains valid.

Classic fry farming

Trout and other sport fish are often raised from eggs to fry or fingerlings and then trucked to streams and released. Normally, the fry are raised in long, shallow concrete tanks, fed with fresh stream water. The fry receive commercial fish food in pellets. While not as efficient as the New Alchemists' method, it is also far simpler, and has been used for many years to stock streams with sport fish. European eel (Anguilla anguilla) aquaculturalists procure a limited supply of glass eels, juvenile stages of the European eel which swim north from the Sargasso Sea breeding grounds, for their farms. The European eel is threatened with extinction because of the excessive catch of glass eels by Spanish fishermen and overfishing of adult eels in, e.g., the Dutch IJsselmeer, Netherlands. As per 2005, no one has managed to breed the European eel in captivity.

Criticisms

The issue of feeds in fish farming has been a controversial one. Many cultured fishes (tilapia, carp, catfish, many others) require no meat or fish products in their diets. Top-level carnivores (most salmon species) depend on fish feed of which a portion is usually derived from wild caught fish (anchovies, menhaden, etc.). Vegetable-derived proteins have successfully replaced fish meal in feeds for carnivorous fishes, but vegetable-derived oils have not successfully been incorporated into the diets of carnivores.

Secondly, farmed fish are kept in concentrations never seen in the wild (e.g. 50,000 fish in a 2-acre (8,100 m2) area.[3]) with each fish occupying less room than the average bathtub. This can cause several forms of pollution. Packed tightly, fish rub against each other and the sides of their cages, damaging their fins and tails and becoming sickened with various diseases and infections.[4]

However, fish tend also to be animals that aggregate into large schools at high density. Most successful aquaculture species are schooling species, which do not have social problems at high density. Aquaculturists tend to feel that operating a rearing system above its design capacity or above the social density limit of the fish will result in decreased growth rate and increased FCR (food conversion ratio - kg dry feed/kg of fish produced), which will result in increased cost and risk of health problems along with a decrease in profits. Stressing the animals is not desirable, but the concept of and measurement of stress must be viewed from the perspective of the animal using the scientific method.[5]

Some species of sea lice have been noted to target farmed coho and Atlantic salmon.[6] Such parasites have been shown to have an effect on nearby wild fish. One place that has garnered international media attention is British Columbia's Broughton Archipelago. There, juvenile wild salmon must "run a gauntlet" of large fish farms located off-shore near river outlets before making their way to sea. It is alleged that the farms cause such severe sea lice infestations that one study predicted a 99% collapse in the wild salmon population in another four years.[7] This claim, however, has been criticized by numerous scientists who question the correlation between increased fish farming and increases in sea lice infestation among wild salmon.[8]

Because of parasite problems, some aquaculture operators frequently use strong antibiotic drugs to keep the fish alive (but many fish still die prematurely at rates of up to 30 percent[9]). In some cases, these drugs have entered the environment. Additionally, the residual presence of these drugs in human food products has become controversial. Use of antibiotics in food production is thought to increase the prevalence of antibiotic resistance in human diseases.[10] The use of antibiotic drugs in aquaculture has decreased considerably in the last decade. Vaccinations and other techniques have virtually eliminated the need for antibiotics.[11]

The lice and pathogen problems of the 1990s facilitated the development of current treatment methods for sea lice and pathogens. These developments reduced the stress from parasite/pathogen problems. However, being in an ocean environment, the transfer of disease organisms from the wild fish to the aquaculture fish is an ever-present risk factor.[12].

The very large number of fish kept long-term in a single location contributes to habitat destruction of the nearby areas. The high concentrations of fish produce a significant amount of condensed faeces, often contaminated with drugs, which again affect local waterways. However, these effects are very local to the actual fish farm site and are minimal to non-measurable in high current sites.

Other potential problems faced by aquaculturists are the obtaining of various permits and water-use rights, profitability, concerns about invasive species and genetic engineering depending on what species are involved, and interaction with the United Nations Convention on the Law of the Sea.

Environmentally friendly methods

This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. (February 2007)
Example of self made recirculation Aquaculture system

An alternative to open ocean cage aquaculture, one in which the risk of environmental damage is substantially eliminated is through the use of a recirculating aquaculture system (RAS). A RAS is a series of culture tanks and filters where water is continuously recycled. To prevent the deterioration of water quality, the water is treated mechanically through the removal of particulate matter and biologically through the conversion of harmful accumulated chemicals into nontoxic ones.

Other treatments such as UV sterilization, ozonation, and oxygen injection are also utilized to maintain optimal water quality. Through this system, many of the environmental drawbacks of aquaculture are minimized including escaped fish, water usage, and the introduction of harmful pollutants. The practices also increase efficiency of feed utilisation and growth by providing optimal water quality parameters (Timmons et al., 2002; Piedrahita, 2003).

One of the drawbacks to recirculating aquaculture systems is water exchange. However, the rate of water exchange can be reduced through aquaponics, such as the incorporation of hydroponically grown plants (Corpron and Armstrong, 1983) and denitrification (Klas et al., 2006). Both methods reduce the amount of nitrate in the water, and can potentially eliminate the need for water exchanges, closing the aquaculture system from the environment. The amount of interaction between the aquaculture system and the environment can be measured through the cumulative feed burden (CFB kg/M3), which measures the amount of feed that goes into the RAS relative to the amount of water and waste discharged.

Because of its high capital and operating costs, RAS has generally been restricted to practices such as broodstock maturation, larval rearing, fingerling production, research animal production, SPF (specific pathogen free) animal production, and caviar and ornamental fish production. Although the use of RAS for other species is considered by many aquaculturalists to be impractical, there has been some limited successful implementation of this with high value product such as barramundi, sturgeon and live tilapia in the US.

Photo gallery

Houseboat rafts with cages under for rearing fish. Near My Tho, Mekong delta, Vietnam.

Transport boats moored at fish processing plant. My Tho, Mekong delta, Vietnam.

Workers removing fish from hold of transport boat. My Tho, Mekong delta, Vietnam.

Fish reared in cages. My Tho, Mekong delta, Vietnam.

See also

References

  1. ^ Weaver, D E (2006) Design and operations of fine media fluidized bed biofilters for meeting oligotrophic water requirements Aquacultural Engineering 34(3): 303-310.
  2. ^ Avnimelech Y, M Kochva, et al. (1994) Development of controlled intensive aquaculture systems with a limited water exchange and adjusted carbon to nitrogen ratio. Israeli Journal of Aquaculture Bamidgeh 46(3): 119-131.
  3. ^ “Fuss Over Farming Fish”, Alaska Science Forum, June 27, 1990
  4. ^ This also causes stress.“Facts about Fish and Fish Farming”, Advocates for Animals.
  5. ^ Journal of Fish Biology 68 (2): 332-372 February 2006
  6. ^ University of Maine, Department of Animal, Veterinary and Aquaculture Sciences, "Sea Lice Information".
  7. ^ Fish Farms Drive Wild Salmon Populations Toward Extinction
  8. ^ Northwest Fish Experts Debunk Controversial Sea Lice Study
  9. ^ Lymbery, P. CIWF Trust report, "In Too Deep - The Welfare of Intensively Farmed Fish" (2002)
  10. ^ Facts About Antibiotic Resistance
  11. ^ UNH Aquaculture website
  12. ^ Bulletin of the European Association of Fish Pathologists 22 (2): 117-125 2002

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'Fish Farm' Blogs
Fish drowning in stupid: GMOs and retroviruses collide! : erv
scienceblogs.com
Fish drowning in stupid: GMOs and retroviruses collide! : erv

ERV

hu, 25 Jun 2009 18:00:43 GM

This should not occur without the pre-market approval from CVM, for those . fish. that have an added gene-based animal drug. Unless youre breaking into research facilities to 'buy' your '. farm. raised' . fish. , this anti-GMO rant has no ...

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Thu Jun 25 16:44:39 2009
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