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upright=1.3, Salmon_farming_in_the_sea_(mariculture)_at_Loch_Ainort,_Isle_of_Skye.html" ;"title="mariculture.html" ;"title="Salmon farming in the sea (mariculture">Salmon farming in the sea (mariculture) at Loch Ainort, Isle of Skye">mariculture.html" ;"title="Salmon farming in the sea (mariculture">Salmon farming in the sea (mariculture) at Loch Ainort, Isle of Skye, Scotland Fish farming or pisciculture involves commercial animal husbandry, breeding of fish, usually for food, in fish tanks or artificial pen (enclosure), enclosures such as
fish pond A fish pond, or fishpond, is a controlled pond A pond is an area filled with water, either natural or artificial, that is smaller than a lake A lake is an area filled with water, localized in a basin, surrounded by land, apart from an ...

fish pond
s. It is a particular type of
aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the farming of fish Fish are , , -bearing animals that lack with . Included in this definition are the living , s, and and as well as various extinct rel ...
, which is the controlled cultivation and
harvesting Harvesting is the process of gathering a ripe crop from the field (agriculture), fields. Reaping is the cutting of grain or pulse (legume), pulse for harvest, typically using a scythe, sickle, or reaper. On smaller farms with minimal mechan ...

harvesting
of
aquatic animal An aquatic animal is an animal Animals (also called Metazoa) are organisms that form the Animalia. With few exceptions, animals , , are , can , and grow from a hollow sphere of , the , during . Over 1.5 million animal have been — ...
s such as fish,
crustacean Crustaceans (Crustacea ) form a large, diverse arthropod taxon which includes such animals as crabs, lobsters, crayfish, Caridea, shrimp, krill, Dendrobranchiata, prawns, woodlice, barnacles, copepods, amphipoda, amphipods and mantis shrimp. The ...
s,
mollusc Mollusca is the second-largest phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number ...
s and so on, in
natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and ...

natural
or pseudo-natural environment. A facility that releases
juvenile fish#REDIRECT juvenile fish Juvenile fish go through various stages between birth and adulthood. They start as eggs which hatch into larvae A larva (plural larvae ) is a distinct juvenile form many animal Animals (also called Metazoa) ar ...
into the wild for
recreational fishing Recreational fishing, also called sport fishing, is fishing Fishing is the activity of trying to catch fish Fish are , , -bearing animals that lack with . Included in this definition are the living , s, and and as well as various ...
or to supplement a species' natural numbers is generally referred to as a
fish hatchery A fish hatchery is a place for artificial breeding, hatching, and rearing through the early life stages of animals—finfish and shellfish in particular.Crespi V., Coche A. (2008) Food and Agriculture Organization of the United Nations (FAO) Glossa ...

fish hatchery
. Worldwide, the most important fish
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
produced in fish farming are
carp Carp are various species of oily fish, oily freshwater fish from the family Cyprinidae, a very large group of fish native to Europe and Asia. While carp is consumed in many parts of the world, they are generally considered an invasive species in ...

carp
,
catfish Catfish (or catfishes; order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, o ...

catfish
,
salmon Salmon is the common name for several species of ray-finned fish Actinopterygii ( New Latin ('having rays') + Greek ( 'wing, fins')), members of which are known as ray-finned fishes, is a clade A clade (; from grc, , ''klados'', ...

salmon
and
tilapia Tilapia ( ) is the common name Common may refer to: Places * Common, a townland in County Tyrone, Northern Ireland * Boston Common Boston Common (also known as the Common) is a central public park in downtown Boston, Massachusetts. It is s ...

tilapia
. Global demand is increasing for dietary fish protein, which has resulted in widespread
overfishing Overfishing is the removal of a species of fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, an ...
in
wild fisheries A wild fishery is a natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxies, and al ...
, resulting in significant decrease in
fish stocks Fish stocks are population, subpopulations of a particular species of fish, for which intrinsic parameters (growth, recruitment, mortality and fishing mortality) are traditionally regarded as the significant factors determining the Population dyn ...
and even complete depletion in some regions. Fish farming allows establishment of artificial fish
colonies In political science, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the metropole, metropolitan ...
that are provided with sufficient
feeding Eating (also known as consuming) is the ingestion of food, typically to provide a heterotrophic organism with food energy, energy and to allow for :wikt:growth, growth. Animals and other heterotrophs must eat in order to survive — carnivores ...

feeding
, protection from natural
predator Predation is a biological interaction In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical en ...

predator
s and competitive threats, access to
veterinarian A veterinarian (vet), also known as a veterinary surgeon or veterinary physician, is a medical professional who practices veterinary medicine by treating diseases, disorders, managing reproductive health and injuries in non-human animal ...
service, and easier harvesting when needed, while being separate from and thus do not usually impact the
sustainable yield The sustainable yield of natural capital on "natural capital" and "balancing the budget of our resources" File:Fires along the Rio Xingu, Brazil - NASA Earth Observatory.jpg, Fires along the Rio Xingu, Brazil - NASA Earth Observatory. Loss of na ...
s of wild fish populations. While fish farming are practised worldwide,
China China (), officially the People's Republic of China (PRC; ), is a country in East Asia East Asia is the eastern region of Asia Asia () is Earth's largest and most populous continent, located primarily in the Eastern Hemisphere ...

China
alone provides 62% of the world's farmed fish production. As of 2016, more than 50% of seafood was produced by aquaculture. In the last three decades, aquaculture has been the main driver of the increase in fisheries and aquaculture production, with an average growth of 5.3 percent per year in the period 2000–2018, reaching a record 82.1 million tonnes in 2018. Farming
carnivorous fish Predatory fish are fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. They form a sister group to the tunicates, together forming the Chordate#Taxonomy, olfactor ...
such as
salmon Salmon is the common name for several species of ray-finned fish Actinopterygii ( New Latin ('having rays') + Greek ( 'wing, fins')), members of which are known as ray-finned fishes, is a clade A clade (; from grc, , ''klados'', ...

salmon
, however, does not always reduce pressure on wild fisheries, as such farmed fish are usually fed
fishmeal Fish meal is a commercial product made from whole wild-caught fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfi ...
and
fish oil Fish oil is oil An oil is any nonpolar In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to ...
extracted from wild
forage fish Forage fish, also called prey fish or bait fish, are small pelagic fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food ...

forage fish
. The 2008 global returns for fish farming recorded by the
FAO The Food and Agriculture Organization of the United Nations (FAO)french: Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is a specialized agency ...

FAO
totaled 33.8 million
tonne The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilogram The kilogram (also kilogramme) is the base unit of mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a meas ...
s worth about US$ 60 billion.


Major species


Categories

Aquaculture makes use of local
photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Conversion (Doctor Who audio), "Conversion" (''Doctor Who'' audio), an episode of the audio drama ' ...
production (extensive) or fish that are fed with external food supply (intensive).


Extensive aquaculture


Intensive aquaculture

In these kinds of systems fish production per unit of surface can be increased at will, as long as sufficient
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
, fresh water and food are provided. Because of the requirement of sufficient fresh water, a massive
water purification Water purification means the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for ...
system must be integrated in the fish farm. One way to achieve this is to combine
hydroponic Hydroponics is a type of horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comfort and ornamental purposes. Horticulturists grow flowers, fruits and nuts, vegetables and her ...
horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comfort and ornamental purposes. Horticulturists are agriculturists who grow flowers, fruits and nuts, vegetables and herbs, as well as or ...
and
water treatment Water treatment is any process that improves the quality Quality may refer to: Concepts *Quality (business), the ''non-inferiority'' or ''superiority'' of something *Quality (philosophy), an attribute or a property *Quality (physics), in respo ...

water treatment
, 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
environmentalist An environmentalist is a person who is concerned with and/or advocates for the protection of the environment. An environmentalist can be considered a supporter of the goals of the environmental movement The environmental movement (sometimes ...
s object to this practice. The cost of inputs per unit of fish weight is higher than in extensive farming, especially because of the high cost of
fish feed Manufactured feeds are an important part of modern commercial aquaculture, providing the balanced nutrition needed by farmed fish. The feeds, in the form of granules or pellets, provide the nutrition in a stable and concentrated form, enabling the ...
. It must contain a much higher level of
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
(up to 60%) than
cattle Cattle, taurine cattle, Eurasian cattle, or European cattle (''Bos taurus'' or ''Bos primigenius taurus'') are large domestication, domesticated Cloven hoof, cloven-hooved herbivores. They are a prominent modern member of the subfamily Bovinae ...

cattle
feed and a balanced
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
composition, as well. These higher protein-level requirements are a consequence of the higher feed efficiency of aquatic animals (higher
feed conversion ratioIn animal husbandry, feed conversion ratio (FCR) or feed conversion rate is a ratio or rate (mathematics), rate measuring of the efficiency with which the bodies of livestock convert animal feed into the desired output. For dairy cattle, dairy cows, ...
that is, kg of feed per kg of animal produced). Fish such as salmon have an FCR around 1.1 kg of feed per kg of salmon whereas chickens are in the 2.5 kg of feed per kg of chicken range. Fish do not use energy to keep warm, eliminating some carbohydrates and fats in the diet, required to provide this energy. This may be offset, though, by the lower land costs and the higher production which can be obtained due to the high level of input control.
Aeration Aeration (also called aerification or aeriation) is the Systems engineering process, process by which air is circulated through, mixed with or solvation, dissolved in a liquid. Aeration of liquids Methods Aeration of liquids (usually water) is ach ...

Aeration
of the water is essential, as fish need a sufficient oxygen level for growth. This is achieved by bubbling, cascade flow, or aqueous oxygen. ''
Clarias ''Clarias'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a ...
'' spp. can breathe atmospheric air and can tolerate much higher levels of pollutants than 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 Biomass is plant or animal material used as fuel to produce electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position ...

biomass
. The risk of infections by parasites such as fish lice, fungi ('' Saprolegnia'' spp.), intestinal worms (such as
nematodes The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the valu ...
or
trematodes Trematoda is a class within the phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. ...
), bacteria (e.g., ''
Yersinia ''Yersinia'' is a genus of bacteria in the family Yersiniaceae. ''Yersinia'' species are Gram-negative, coccobacilli bacteria, a few micrometers long and fractions of a micrometer in diameter, and are facultative anaerobes. Some members of ''Yers ...

Yersinia
'' spp., ''
Pseudomonas ''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 validly described species. The members of the genus demonstrate a great deal of Metabolism, metabolic diversity and conse ...

Pseudomonas
'' spp.), and protozoa (such as
dinoflagellates The dinoflagellates ( Greek δῖνος ''dinos'' "whirling" and Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, ...

dinoflagellates
) is similar to that in
animal husbandry Animal husbandry is the branch of agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Ex ...
, especially at high population densities. However, animal husbandry is a larger and more technologically mature area of human agriculture and has developed better solutions to pathogen problems. Intensive aquaculture has to provide adequate water quality (oxygen, ammonia, nitrite, etc.) levels to minimize stress on the fish. This requirement makes control of the pathogen problem more difficult. Intensive aquaculture requires tight monitoring and a high level of expertise of the fish farmer. Very-high-intensity recycle aquaculture systems (RAS), where all the production parameters are controlled, are being used for high-value species. By recycling water, little is used per unit of production. However, the process has high capital and operating costs. The higher cost structures mean that RAS is economical only for high-value products, such as broodstock for egg production, fingerlings for net pen aquaculture operations, sturgeon production, research animals, and some special niche markets such as live fish. Raising ornamental coldwater fish (
goldfish The goldfish (''Carassius auratus'') is a freshwater fish are common freshwater fish throughout temperate Eurasia. Freshwater fish are those that spend some or all of their lives in fresh water, such as river A river is a natural flowi ...

goldfish
or
koi or more specifically , are colored varieties of the Amur carp (''Cyprinus rubrofuscus ''Cyprinus rubrofuscus'', the Amur carp, is a species of cyprinid fish. It is widespread in Eastern Asia East Asia is the east East is one of the ...

koi
), although theoretically much more profitable due to the higher income per weight of fish produced, has been successfully carried out only in the 21st century. 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, a few commercially successful intensive koi-growing facilities are operating 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. In 2016, juvenile Nile tilapia were given a food containing dried '' Schizochytrium'' in place of
fish oil Fish oil is oil An oil is any nonpolar In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to ...
. When compared to a control group raised on regular food, they exhibited higher weight gain and better food-to-growth conversion, plus their flesh was higher in healthy
omega-3 fatty acid Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or ''n''−3 fatty acids, are polyunsaturated fatty acid Polyunsaturated fatty acids (PUFAs) are fatty acids that contain more than one double bond in their backbone. This ...
s.


Fish farms

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


Cage system

Fish cages are placed in lakes, bayous, ponds, rivers, or oceans to contain and protect fish until they can be harvested. The method is also called "off-shore cultivation" when the cages are placed in the sea. 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 in popularity. Given concerns of disease, poaching, poor water quality, etc., generally pond systems are considered simpler to start and easier to manage. Also, the past occurrences of cage-failures leading to escapes, have raised concern regarding the culture of non-native fish species in dam or open-water cages. On August 22, 2017, there was a massive failure of such cages at a commercial fishery in Washington state in
Puget Sound Puget Sound () is a of the , an inlet of the , and part of the . It is located along the northwestern coast of the of . It is a complex system of interconnected marine waterways and basins, with one major and two minor connections to the ope ...
, leading to release of nearly 300,000 Atlantic salmon in non-native waters. This is believed to risk endangering the native Pacific salmon species. Marine Scotland has kept records of caged fish escapes since 1999. The have recoded 357 fish escape incidents with 3,795,206 fish escaping into fresh and salt water. One company, Dawnfresh Farming Limited has been responsible for 40 incident and 152,790 Rainbow Trout escaping in to freshwater lochs. Though the cage-industry has made numerous technological advances in cage construction in recent years, the risk of damage and escape due to storms is always a concern.
Semi-submersible Semi-submersible may refer to a self-propelled vessel, such as: *Heavy-lift ship A heavy-lift ship is a ship, vessel designed to move very large loads that cannot be handled by normal ships. They are of two types: *''Semi-submersible'' ships ...
marine technology is beginning to impact fish farming. In 2018, 1.5 million
salmon Salmon is the common name for several species of ray-finned fish Actinopterygii ( New Latin ('having rays') + Greek ( 'wing, fins')), members of which are known as ray-finned fishes, is a clade A clade (; from grc, , ''klados'', ...

salmon
are in the middle of a year-long trial at Ocean Farm 1 off the coast of
Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official written standard for the Norwegian language Norwegian (Norwegian: ''norsk'') is a Nort ...

Norway
. The semi-submersible project is the world's first deep-sea aquaculture project, and includes -high by -diameter pen made from a series of mesh-wire frames and nets, designed to disperse wastes better than more conventional farms in sheltered coastal waters, and therefore, be able to support higher fish packing density.


Copper-alloy nets

Recently,
copper alloys Copper is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same nu ...
have become important netting materials in
aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the farming of fish Fish are , , -bearing animals that lack with . Included in this definition are the living , s, and and as well as various extinct rel ...
. Copper alloys are
antimicrobial An antimicrobial is an agent that kills microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All orga ...
, that is, they destroy
bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

bacteria
,
viruses A virus is a wikt:submicroscopic, submicroscopic infectious agent that Viral replication, replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, incl ...
,
fungi A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

fungi
,
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
, and other
microbes A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical process ...
. In the
marine environment Marine habitats are habitat In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environ ...
, the antimicrobial/algaecidal properties of copper alloys prevent
biofouling Biofouling or biological fouling is the accumulation of microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any ...
, which can briefly be described as the undesirable accumulation, adhesion, and growth of microorganisms, plants,
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
, tube worms,
barnacles A barnacle is a type of arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda,Reference sh ...

barnacles
,
mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are recognized. The number of fossil species is es ...
, and other organisms. The resistance of organism growth on copper alloy nets also provides a cleaner and healthier environment for farmed fish to grow and thrive. Traditional netting involves regular and labor-intensive cleaning. In addition to its antifouling benefits, copper netting has strong structural and corrosion-resistant properties in marine environments. Copper-zinc brass alloys are deployed in commercial-scale aquaculture operations in Asia, South America, and the USA (Hawaii). Extensive research, including demonstrations and trials, are being implemented on two other copper alloys: copper-nickel and copper-silicon. Each of these alloy types has an inherent ability to reduce biofouling, cage waste, disease, and the need for antibiotics, while simultaneously maintaining water circulation and oxygen requirements. Other types of copper alloys are also being considered for research and development in aquaculture operations. In
Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern subregion of Asia, consisting of the regions ...

Southeast Asia
, the traditional cage farming platform is called
kelong A kelong (or kellong) is an offshore platform built predominantly with wood, which can be found in waters off Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and fed ...
.


Open net pen system

The open net pens system is a method that takes place in natural waters, such as rivers, lakes, near the coast or offshore. The breeders are rearing the fish in large cages, floating in the water. The fish are living in natural water, but are isolated with a net. So the only barrier separating the fish from the surrounding environment is a net, this allows the water to flow from the ‘natural’ surrounding through the fish farms. The site of the fish farm is crucial for the farm to be a success or not. Before any fish farm is settled, it is highly recommended to be selective with the site location of the farm. The site must be examined on some essential elements. Important conditions on the location are: # A good interchange of water and also a high replacement of bottom water. # On all depths should be a good current condition. This is necessary, because of the organic particles that should be able to be carried away using the stream. # A gravel and sand bottom are qualified for fish farming, although bottoms with silt and mud are not qualified. These should be avoided. # A net should be at least or more above the bottom, so depth is important. Despite these important site conditions, the open net pen method is, or should say was, very popular in Norway and China. This is because of the cost friendliness and efficiency of this method.


Negative external effects

Because of the oceans water flows through and other reasons, open net pen culture is seen as a high-risk method for the environment. The flow allows chemicals, parasites, waste and diseases to spread in the enclosed environment, and this is not in advance for the natural environment. Another negative consequence is the high escaping rate of the cultured fish in these open net pens. These escaped fish pose also a high risk to the surrounding ecosystems.


Irrigation ditch or pond systems

These use
irrigation Irrigation is the agricultural Agriculture is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in seden ...

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, water allotments can be stored 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 control of the water can increase yields substantially, as long as
eutrophication Eutrophication (from Greek ''eutrophos'', "well-nourished") is the process by which an entire body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokm ...

eutrophication
is prevented and oxygen levels stay high. Yields can be low if the fish grow ill from electrolyte stress.


Composite fish culture

The composite fish culture system is a technology developed in India by the
Indian Council of Agricultural Research Indian or Indians refers to people or things related to India India (Hindi: ), officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by population, second-most populous country, ...
in the 1970s. In this system, of both local and imported fish, a combination of five or six fish species is used in a single fish pond. These species are selected so that they do not compete for food among them by having different types of food habitats. As a result, the food available in all the parts of the pond is used. Fish used in this system include
catla Catla (''Labeo catla''), ( bn, কাত্লা, translit=kātlā) also known as the major South Asian carp, is an economically important South Asian freshwater fish in the carp family Cyprinidae Cyprinidae is a Family (biology), family of ...
and
silver carp #REDIRECT Silver carp #REDIRECT Silver carp#REDIRECT Silver carp The silver carp (''Hypophthalmichthys molitrix'') is a species of freshwater cyprinid fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb ...

silver carp
which are surface feeders,
rohu The rohu, rui, or roho labeo (''Labeo rohita'') is a species of fish of the carp family, found in rivers in South Asia South Asia is the southern region of Asia Asia () is 's largest and most populous , located primarily in the ...

rohu
, a column feeder, and
mrigal The mrigal carp (''Cirrhinus cirrhosus''), ( bn, মৃগেল, translit=mrigél) also known as the white carp, is a species of ray-finned fish Actinopterygii ( New Latin ('having rays') + Greek ( 'wing, fins')), members of which are known ...
and
common carp The common carp or European carp (''Cyprinus carpio'') is a widespread freshwater fish Fish are , , -bearing animals that lack with . Included in this definition are the living , s, and and as well as various extinct related groups. Ar ...

common carp
, which are bottom feeders. Other fish also feed on the excreta of the common carp, and this helps contribute to the efficiency of the system which in optimal conditions produces 3000–6000 kg of fish per hectare per year. One problem with such composite fish culture is that many of these fish breed only during monsoon. Even if fish are collected from the wild, they can be mixed with other species, as well. So, a major problem in fish farming is the lack of availability of good-quality stock. To overcome this problem, ways have now been worked out to breed these fish in ponds using hormonal stimulation. This has ensured the supply of pure fish stock in desired quantities.


Integrated recycling systems

One of the largest problems with freshwater pisciculture is that it can use a million gallons of water per acre (about 1 m3 of water per m2) each year. Extended
water purification Water purification means the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for ...
systems allow for the reuse (
recycling Recycling is the process of converting waste Waste (or wastes) are unwanted or unusable materials. Waste is any substance which is discarded after primary use, or is worthless, defective and of no use. A by-product A by-product or ...

recycling
) of local water. The largest-scale pure fish farms use a system derived (admittedly much refined) from the
New Alchemy Institute The New Alchemy Institute was a research center that did pioneering investigation into organic agriculture, aquaculture and bioshelter design between 1969 and 1991. It was founded by John Todd (Canadian biologist), John Todd, Nancy Jack Todd, and W ...
in the 1970s. Basically, large plastic fish tanks are placed in a greenhouse. A
hydroponic Hydroponics is a type of horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comfort and ornamental purposes. Horticulturists grow flowers, fruits and nuts, vegetables and her ...
bed is placed near, above or between them. When tilapia are raised in the tanks, they are able to eat algae, which naturally grow in the tanks when the tanks are properly fertilized. The tank water is slowly circulated to the hydroponic beds, where the tilapia waste feeds commercial plant crops. Carefully cultured microorganisms in the hydroponic bed convert
ammonia Ammonia is a chemical compound, compound of nitrogen and hydrogen with the chemical formula, formula NH3. A Binary compounds of hydrogen, stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct ch ...

ammonia
to
nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalently bonded A covalent bond is a chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the format ...

nitrate
s, and the plants are fertilized by the nitrates and
phosphate In chemistry, a phosphate is an anion, salt (chemistry), salt, functional group or ester derived from a phosphoric acids and phosphates, phosphoric acid. It most commonly means orthophosphate, a derivative of phosphoric acid, orthophosphoric a ...

phosphate
s. Other wastes are strained out by the hydroponic media, which double 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
herb In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is app ...

herb
s (e.g.
parsley Parsley, or garden parsley (''Petroselinum ''Petroselinum'' (parsley) is a genus of two species of flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land p ...

parsley
and
basil Basil (, also ; ''Ocimum basilicum''), also called great basil, is a culinary herb of the Family (biology), family Lamiaceae (mints). Basil is native to tropical regions from central Africa to Southeast Asia. It is a Hardiness (plants), ten ...

basil
), which command premium prices in small quantities all year long. The most common customers are
restaurant A restaurant is a business Business is the activity of making one's living or making money by producing or buying and selling products (such as goods and services). Simply put, it is "any activity or enterprise entered into for profit." ...

restaurant
wholesalers. Since the system lives in a
greenhouse A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of transparent material, such as glass, in which plant Plants are predominantly photosynthetic Photo ...

greenhouse
, it adapts to almost all temperate climates, and may also adapt to
tropical climate Tropical climate is one of the five major climate groups in the Köppen climate classification The Köppen climate classification is one of the most widely used climate classification Climate classification is a way of categorizing the worl ...
s. The main environmental impact is discharge of water that must be salted to maintain the fishes'
electrolyte An electrolyte is a medium containing ions that is electrically conducting Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how strongly it resist ...

electrolyte
balance. Current growers use a variety of proprietary tricks to keep fish healthy, reducing their expenses for salt and wastewater 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. One future development is the combination of integrated recycling systems with urban farming as tried in Sweden by the Greenfish Initiative.


Classic fry farming

This is also called a "flow through system" Trout and other sport fish are often raised from eggs to 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 The European eel (''Anguilla anguilla'') is a species of eel, a snake-like, fish migration, catadromous fish. They are normally around and rarely reach more than , but can reach a length of up to in exceptional cases. Eels have been important ...

Anguilla anguilla
'') aquaculturalists procure a limited supply of glass eels, juvenile stages of the European eel which swim north from the
Sargasso Sea The Sargasso Sea () is a region of the Atlantic Ocean bounded by four ocean current, currents forming an ocean gyre. Unlike all other regions called seas, it has no land boundaries. It is distinguished from other parts of the Atlantic Ocean ...
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 The IJsselmeer (, also , , ; fy, Iselmar, nds-nl, Iesselmeer), also known as Lake IJssel in English, is a closed off inland in the central bordering the of , and . It covers an area of with an average depth of . The river flows into the ...

IJsselmeer
, Netherlands. Although European eel larvae can survive for several weeks, the full life cycle has not yet been achieved in captivity.


Issues


Feeding

The issue of feeds in fish farming has been a controversial one. Many cultured fishes (tilapia, carp, catfish, many others) can be raised on a strictly herbivore diet. Top-level carnivores (most
salmonidae Salmonidae is a Family (biology), family of ray-finned fish, the only living family currently placed in the Order (biology), order Salmoniformes . It includes salmon (both ocean-going and lake-locked), trout, Salvelinus, chars, freshwater whitef ...
species in particular) on the other hand, depend on fish feed, of which a large portion is usually derived from wild-caught fish (
anchovies An anchovy is a small, common forage fish Forage fish, also called prey fish or bait fish, are small pelagic fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical oce ...

anchovies
,
menhaden Menhaden, also known as mossbunker and bunker, are forage fish of the genera ''Brevoortia'' and ''Ethmidium'', two genera of marine fish in the family Clupeidae. ''Menhaden'' is a blend of ''poghaden'' (''pogy'' for short) and an Eastern Algon ...
, 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. Research is underway to try to change this, such that even salmon and other carnivores could be successfully fed with vegetable products. The F3 Challenge (Fish-Free Feed Challenge), as explained by a report from ''
Wired ''Wired'' (stylized as ''WIRED'') is a monthly American magazine, published in print and online magazine, online editions, that focuses on how emerging technologies affect culture, the economy, and politics. Owned by Condé Nast, it is headquar ...
'' in February 2017, "is a race to sell 100,000 metric tons of fish food, without the fish. Earlier this month, start-ups from places like Pakistan, China, and Belgium joined their American competition at the Google headquarters in Mountain View, California, showing off feed made from
seaweed Seaweed, or macroalgae, refers to thousands of species of , , . The term includes some types of ' (red), ' (brown) and ' (green) macroalgae. Seaweed species such as s provide essential nursery habitat for fisheries and other marine species an ...

seaweed
extracts,
yeast Yeasts are eukaryotic Eukaryotes () are organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...

yeast
, and
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
grown in
bioreactor A bioreactor refers to any manufactured device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which a chemical process In a scientific Science () is a systematic enterprise that Scientific ...
s." Not only do the feeds for carnivorous fish, like certain salmon species, remain controversial due to the containment of wild caught fish like anchovies, but they are not helping the health of the fish, as is the case in Norway. Between 2003 and 2007, Aldrin et al., examined three infectious diseases in Norwegian salmon fish farms—heart and skeletal muscle inflammation, pancreas disease, and infectious salmon anemia. In 2014, Martinez-Rubio et al., conducted a study in which cardiomyopathy syndrome (CMS), a severe cardiac disease in Atlantic salmon (''Salmo salar''), was investigated pertaining the effects of functional feeds with reduced lipid content and increased eicosapentaenoic acid levels in controlling CMS in salmon after infection with Piscine Myocarditis Virus (PMCV). Functional feeds are defined as high-quality feeds that beyond purposes of nutrition, they are formulated with health promoting features that could be beneficial in supporting disease resistance, such as CMS. In choosing a clinical nutrition approach using functional feeds could, potentially move away from chemotherapeutic and antibiotic treatments, which could lower the costs of disease treatment and management in fish farms. In this investigation three fishmeal-based diets were served—one made of 31% lipid and the other two made of 18% lipid (one contained fishmeal and the other krill meal. Results demonstrated a significant difference in the immune and inflammatory responses and pathology in heart tissue as the fish were infected with PMCV. Fish fed with functional feeds with low lipid content demonstrated milder and delayed inflammatory response and therefore, less severe heart lesions at earlier and later stages after have PMCV infection.


Stocking density

Secondly, farmed fish are kept in concentrations never seen in the wild (e.g. 50,000 fish in a area.). 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 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
feed conversion ratioIn animal husbandry, feed conversion ratio (FCR) or feed conversion rate is a ratio or rate (mathematics), rate measuring of the efficiency with which the bodies of livestock convert animal feed into the desired output. For dairy cattle, dairy cows, ...
(kg dry feed/kg of fish produced), which results 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.


Parasites & disease

Sea lice, particularly ''Lepeophtheirus salmonis'' and various ''Caligus'' species, including ''C. clemensi'' and ''C. rogercresseyi'', can cause deadly infestations of both farm-grown and wild salmon. Sea lice are
ectoparasite Parasitism is a symbiotic relationship between species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often def ...
s which feed on mucus, blood, and skin, and migrate and latch onto the skin of wild salmon during free-swimming, planktonic ''nauplii'' and ''copepodid'' larval stages, which can persist for several days. Large numbers of highly populated, open-net salmon farms can create exceptionally large concentrations of sea lice; when exposed in river estuaries containing large numbers of open-net farms, many young wild salmon are infected, and do not survive as a result. Adult salmon may survive otherwise critical numbers of sea lice, but small, thin-skinned juvenile salmon migrating to sea are highly vulnerable. On the Pacific coast of Canada, the louse-induced mortality of pink salmon in some regions is commonly over 80%. In Scotland, official figures show that more than nine million fish were lost to disease, parasites, botched treatment attempts and other problems on fish farms between 2016 and 2019. One of the treatments for parasite infestations involved bathing fish in hydrogen peroxide, which can harm or kill farmed fish if they are in a weak condition or if the chemical concentration is too strong. A 2008 meta-analysis of available data shows that salmon farming reduces the survival of associated wild salmon populations. This relationship has been shown to hold for Atlantic, steelhead, pink, chum, and coho salmon. The decrease in survival or abundance often exceeds 50%. Diseases and parasites are the most commonly cited reasons for such decreases. Some species of sea lice have been noted to target farmed coho and Atlantic salmon. 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 Broughton Archipelago is a group of islands located at the eastern end of Queen Charlotte Strait in Mount Waddington Regional District, British Columbia ( en, Splendour without diminishment) , image_map = British Columbia in Canad ...
. There, juvenile wild salmon must "run a gauntlet" of large fish farms located off-shore near river outlets before making their way to sea. The farms allegedly cause such severe sea lice infestations that one study predicted in 2007 a 99% collapse in the wild salmon population by 2011. 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. 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 up to 30%. Additionally, other common drugs used in salmonid fish farms in North America and Europe include anesthetic, chemotherapeutic, and anthelmintic agents. 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 Antimicrobial resistance (AMR or AR) occurs when microbe A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is some ...

antibiotic resistance
in human diseases. At some facilities, the use of antibiotic drugs in aquaculture has decreased considerably due to vaccinations and other techniques. However, most fish-farming operations still use antibiotics, many of which escape into the surrounding environment. The lice and pathogen problems of the 1990s facilitated the development of current treatment methods for sea lice and pathogens, which 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.


Ecosystem impacts

The large number of fish kept long-term in a single location contributes to
habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat Ibex in an alpine habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are pr ...
of the nearby areas. The high concentrations of fish produce a significant amount of condensed faeces, often contaminated with drugs, which again affects local waterways. Aquaculture not only impacts the fish on the farm, but it also influences other species, which in return are attracted to or repelled by the farms. Mobile fauna, such as crustaceans, fish, birds, and marine mammals, interact with the process of aquaculture, but the long-term or ecological effects as a result of these interactions is still unknown. Some of these fauna may be attracted or demonstrate repulsion. The attraction/repulsion mechanism has various direct and indirect effects on wild organisms at individual and population levels. The interactions that wild organisms have with aquaculture may have implications on the management of fisheries species and the ecosystem in relation to how the fish farms are structured and organized.


Siting

If aquaculture farms are placed in an areas with strong current, pollutants can be flushed out of the area fairly quickly. This help manage the pollution problem and also aids in overall fish growth. Concern remains that resultant bacterial growth fertilised by fish faeces strips the water of oxygen, reducing or killing off the local marine life. Once an area has been so contaminated, fish farms are typically moved to new, uncontaminated areas. This practice has angered nearby fishermen. Other potential problems faced by aquaculturists include the obtaining of various permits and water-use rights, profitability, concerns about
invasive species An invasive species is an introduced organism that becomes overpopulated and negatively alters its new environment. Although their spread can have beneficial aspects, invasive species adversely affect the invaded habitat Ibex in an ...
and
genetic engineering Genetic engineering, also called genetic modification or genetic manipulation, is the direct manipulation of an organism's gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_in ...
depending on what species are involved, and interaction with the
United Nations Convention on the Law of the Sea The United Nations Convention on the Law of the Sea (UNCLOS), also called the Law of the Sea Convention or the Law of the Sea Treaty, is an international agreement A treaty is a formal legally binding written agreement between actors in intern ...

United Nations Convention on the Law of the Sea
.


Genetic modification

In regards to genetically modified, farmed salmon, concern has been raised over their proven reproductive advantage and how it could potentially decimate local fish populations, if released into the wild. Biologist Rick Howard did a controlled laboratory study where wild fish and GMO fish were allowed to breed. In 1989, the AquaBounty Technologies developed the Aqua Advantage salmon. The concerns and critiques of cultivating this GMO fish in aquaculture are that the fish will escape and interact with other fish ultimately leading to the reproduction with other fishes. However, the FDA, has determined that while net pens would not be the most appropriate to prevent escapes, that raising the salmon in Panama waters would result effective in the prevention of escape because the water conditions there would fail to support long-term survival of the salmon in the case that they escaped. Another method of preventing Aqua Advantage fish from impacting the ecosystems in the case they escape suggested by the FDA was to create sterile triploid females. This way concerns on reproducing with other fishes would be out of the question. The GMO fish crowded out the wild fish in spawning beds, but the offspring were less likely to survive. The colorant used to make pen-raised salmon appear rosy like the wild fish has been linked with retinal problems in humans.


Labeling

In 2005, Alaska passed legislation requiring that any genetically altered fish sold in the state be labeled. In 2006, a ''
Consumer Reports Consumer Reports (CR), formerly Consumers Union (CU), is an American nonprofit consumer organization Consumer organizations are advocacy Advocacy is an activity by an individual or group that aims to influence decisions within political, ...
'' investigation revealed that farm-raised salmon is frequently sold as wild. In 2008, the US
National Organic Standards Board The National Organic Standards Board is an advisory board that makes recommendations to the United States Secretary of Agriculture The United States secretary of agriculture is the head of the United States Department of Agriculture The United ...
allowed farmed fish to be labeled as organic provided less than 25% of their feed came from wild fish. This decision was criticized by the advocacy group Food & Water Watch as "bending the rules" about organic labeling. In the European Union, fish labeling as to species, method of production and origin has been required since 2002. Concerns continue over the labeling of salmon as farmed or wild-caught, as well as about the humane treatment of farmed fish. The Marine Stewardship Council has established an Eco label to distinguish between farmed and wild-caught salmon, while the RSPCA has established the Freedom Food label to indicate humane treatment of farmed salmon, as well as other food products.


Indoor fish farming

Other treatments such as ultraviolet sterilization, ozonation, and oxygen injection are also used 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 pollutants. The practices also increased feed-use efficiency growth by providing optimum water quality. One of the drawbacks to recirculating aquaculture systems is the need for periodic water exchanges. However, the rate of water exchange can be reduced through aquaponics, such as the incorporation of hydroponically grown plants and denitrification. 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. The environmental impact of larger indoor fish farming system will be linked to the local infrastructure, and water supply. Areas which are more drought-prone, indoor fish farms might flow out wastewater for watering agricultural farms, reducing the water affliction. From 2011, a team from the University of Waterloo led by Tahbit Chowdhury and Gordon Graff examined vertical RAS aquaculture designs aimed at producing protein-rich fish species. However, 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, specific pathogen-free animal production, and caviar and ornamental fish production. As such, research and design work by Chowdhury and Graff remains difficult to implement. Although the use of RAS for other species is considered by many aquaculturalists to be currently impractical, some limited successful implementation of RAS has occurred with high-value product such as barramundi, sturgeon, and live tilapia in the US, eels and
catfish Catfish (or catfishes; order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, o ...

catfish
in the Netherlands, trout in Denmark and
salmon Salmon is the common name for several species of ray-finned fish Actinopterygii ( New Latin ('having rays') + Greek ( 'wing, fins')), members of which are known as ray-finned fishes, is a clade A clade (; from grc, , ''klados'', ...

salmon
is planned in Scotland and Canada.


Slaughter methods

Tanks saturated with carbon dioxide have been used to make fish unconscious. Their gills are then cut with a knife so that the fish bleed out before they are further processed. This is no longer considered a humane method of slaughter. Methods that induce much less physiological stress are electrical or percussive stunning and this has led to the phasing out of the carbon dioxide slaughter method in Europe.Victoria Braithwaite (2010). ''Do fish feel pain?'' Oxford University Press, p. 180


Inhumane methods

According to T. Håstein of the National Veterinary Institute (Oslo, Norway), "Different methods for slaughter of fish are in place and it is no doubt that many of them may be considered as appalling from an animal welfare point of view." A 2004 report by the EFSA Scientific Panel on Animal Health and Welfare explained: "Many existing commercial killing methods expose fish to substantial suffering over a prolonged period of time. For some species, existing methods, whilst capable of killing fish humanely, are not doing so because operators don't have the knowledge to evaluate them." Following are some less humane ways of killing fish. * Air asphyxiation amounts to suffocation in the open air. The process can take upwards of 15 minutes to induce death, although unconsciousness typically sets in sooner. * Ice baths or chilling of farmed fish on ice or submerged in near-freezing water is used to dampen muscle movements by the fish and to delay the onset of post-death decay. However, it does not necessarily reduce sensibility to pain; indeed, the chilling process has been shown to elevate cortisol. In addition, reduced body temperature extends the time before fish lose consciousness. * Hypercapnia, CO narcosis * Exsanguination without stunning is a process in which fish are taken up from water, held still, and cut so as to cause bleeding. According to references in Yue, this can leave fish writhing for an average of four minutes, and some catfish still responded to noxious stimuli after more than 15 minutes. * Immersion in salt followed by gutting or other processing such as smoking is applied to eel.


More humane methods

Proper stunning renders the fish unconscious immediately and for a sufficient period of time such that the fish is killed in the slaughter process (e.g. through exsanguination) without regaining consciousness. * Percussive stunning involves rendering the fish unconscious with a blow on the head. * Electric stunning can be humane when a proper current is made to flow through the fish brain for a sufficient period of time. Electric stunning can be applied after the fish has been taken out of the water (dry stunning) or while the fish is still in the water. The latter generally requires a much higher current and may lead to operator safety issues. An advantage could be that in-water stunning allows fish to be rendered unconscious without stressful handling or displacement. However, improper stunning may not induce insensibility long enough to prevent the fish from enduring exsanguination while conscious. Whether the optimal stunning parameters that researchers have determined in studies are used by the industry in practice is unknown.


Gallery

File:2019-03-16 01 Aquaculture in Chile.jpg, Fish farming in the fjords of southern Chile File:Fish-farms-vietnam.jpg, Houseboat rafts with cages under for rearing fish near Mỹ Tho, Vietnam File:Fish-farming-vietnam.jpg, Transport boats moored at fish processing plant, Mỹ Tho File:Zapotec fish farm in Ixtlan Oaxaca.png, Communal Zapotec peoples, Zapotec fish farm in Ixtlán de Juárez, Mexico File:Fish farm Skardu.jpg, Fish farming traditionally takes place in purpose-built tanks in the Skardu region in northern Pakistan. File:Complexo_de_Piscicultura_do_Acre.jpg, Pisciculture Complex, outside Rio Branco, Acre, Rio Branco, Brazil


See also

*Aquaculture of catfish *Aquaculture of salmonids *Kelong *Rice-fish system *Aquaculture


References


Further reading

* * * * * * Jhingran VG (1987
''Introduction to Aquaculture''
Nigerian Institute for Oceanography and Marine Research, FAO, Rome. * *


External links


NOAA Aquaculture Website

FAO Fisheries Department
and it

on fisheries and aquaculture
Coastal Alliance for Aquaculture Reform
Coalition of environmental groups, scientists and First Nations opposed to current salmon farming practices
Ethical concerns about the conditions on fish farms

The Pure Salmon Campaign website

Tropical Fish Farming in Florida

Nature's Subsidies to Shrimp and Salmon Farming
{{DEFAULTSORT:Fish Farming Aquaculture