Editing Fish farming (section)

== 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 ===
[[File:Giant.gourami.arp.jpg|thumb|right|[[Giant gourami]] is often raised in cages in central Thailand.]]

Fish cages are placed in lakes, bayous, ponds, rivers, or oceans to contain and protect fish until they can be harvested.<ref name="scielo.br"/> The method is also called "off-shore cultivation"<ref>{{cite web|url=http://www.sourcewatch.org/index.php?title=Offshore_fish_farming_legislation|title=Offshore fish farming legislation|access-date=30 January 2016|url-status=dead|archive-url=https://web.archive.org/web/20160204173237/http://www.sourcewatch.org/index.php?title=Offshore_fish_farming_legislation|archive-date=4 February 2016}}</ref> 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.<ref name="scielo.br"/>

[[File:Sustainable fish farming 010.jpg|thumb|left|Fish cages in [[Lake Victoria]], [[Uganda]]]]
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]], leading to release of nearly 300,000 Atlantic salmon in non-native waters. This is believed to risk endangering the native Pacific salmon species.<ref>{{Cite web |date=2017-08-22 |title=Please go fishing, Washington state says after farmed Atlantic salmon escape broken net |url=https://www.seattletimes.com/seattle-news/environment/oops-after-accidental-release-of-atlantic-salmon-fisherman-being-told-catch-as-many-as-you-want/ |access-date=2022-08-02 |website=The Seattle Times |language=en-US}}</ref>

Marine Scotland has kept records of caged fish escapes since 1999. They have recorded 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 incidents and the escape of 152,790 rainbow trout into freshwater lochs.<ref>{{Cite web |title=Scotland's Aquaculture {{!}} Fish Escapes |url=http://aquaculture.scotland.gov.uk/data/fish_escapes.aspx |access-date=2021-12-21 |website=aquaculture.scotland.gov.uk}}</ref>

[[File:2019-03-16 01 Aquaculture in Chile.jpg|thumb|Fish cages in [[Castro, Chile]]]]
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.<ref name="scielo.br">{{cite journal|title=Growing, losing or introducing? Cage aquaculture as a vector for the introduction of non-native fish in Furnas Reservoir, Minas Gerais, Brazil|first1=Valter Monteiro de|last1=Azevedo-Santos|first2=Odila|last2=Rigolin-Sá|first3=Fernando Mayer|last3=Pelicice|volume=9|issue=4|pages=915–919|doi=10.1590/S1679-62252011000400024|journal=Neotropical Ichthyology|year=2011|doi-access=free}}</ref>

[[Semi-submersible]] marine technology is beginning to impact fish farming. In 2018, 1.5 million [[salmon]] are in the middle of a year-long trial at Ocean Farm 1 off the coast of [[Norway]]. The semi-submersible {{USD|300 million}} project is the world's first deep-sea aquaculture project, and includes {{convert|200|ft|m|adj=on|order=flip|sp=us}}-high by {{convert|300|ft|m|adj=on|order=flip|sp=us}}-diameter pen made from a series of mesh-wire frames and nets. It is designed to disperse wastes better than more conventional farms in sheltered coastal waters, therefore supporting higher fish packing density.<ref>{{Cite news |date=2018-07-30 |title=The $300 Million Plan to Farm Salmon in the Middle of the Ocean |language=en |work=Bloomberg.com |url=https://www.bloomberg.com/news/articles/2018-07-30/this-300-million-deepwater-platform-houses-1-5-million-salmon |access-date=31 July 2018}}</ref>

In [[Maritime Southeast Asia]], traditional fish cages built around an offshore wooden platform are generally called [[kelong]]. They are usually used to temporarily keep caught fish until sold or cooked, but some are used for fish farming.<ref>{{Cite web |date=2014-12-18 |title=Death of the (Fish) Salesmen: The Last Kelongs in Southeast Asia |url=https://modernfarmer.com/2014/12/death-fish-salesmen-last-kelongs-southeast-asia/ |access-date=2022-07-11 |website=Modern Farmer |language=en-US}}</ref> 

====Copper-alloy nets====
{{Main|Copper alloys in aquaculture}}

Recently, [[copper alloys]] have become important netting materials in [[aquaculture]]. Copper alloys are [[antimicrobial]], that is, they destroy [[bacteria]], [[viruses]], [[fungi]], [[algae]], and other [[microbes]]. In the [[marine environment]], the antimicrobial/algaecidal properties of copper alloys prevent [[biofouling]], which can briefly be described as the undesirable accumulation, adhesion, and growth of microorganisms, plants, [[algae]], [[Tube worm (body plan)|tube worms]], [[barnacles]], [[mollusks]], and other organisms.<ref>{{Cite web|url=https://www.manoramaonline.com/karshakasree/farm-management/2017/04/26/fish-cage-farming-by-manoj.html|title=ഓരുവെള്ളത്തിലെ രുചിയേറും വരുമാനം|website=ManoramaOnline|language=ml}}</ref>

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.<ref>{{Cite journal |last1=dos Santos |first1=Ana Paula |last2=Hage Seta |first2=Jéssica Helena |last3=Kuhnen |first3=Vanessa Villanova |last4=Sanches |first4=Eduardo Gomes |date=2020-11-01 |title=Antifouling alternatives for aquaculture in tropical waters of the Atlantic Ocean |journal=Aquaculture Reports |language=en |volume=18 |pages=100477 |doi=10.1016/j.aqrep.2020.100477 |s2cid=224842700 |issn=2352-5134|doi-access=free |bibcode=2020AqRep..1800477D }}</ref>

Copper-zinc brass alloys are deployed in commercial-scale aquaculture operations in Asia, South America, and 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.<ref>{{Cite web |title=Aquaculture – Copper Development Association Africa |url=https://www.copper.co.za/projects/aquaculture/ |access-date=2022-07-11 |language=en-US}}</ref>

===Fish pens===
{{See also|Aquaculture in the Philippines#Fish pens and cages}}
[[File:8232Bantay Insik Bulaoen West Sison, Pangasinan 24.jpg|thumb|alt=Square stick and net enclosures in a shallow river bed|Small fish pens in the [[Bued River]] in [[Pangasinan]], [[Philippines]]]]
[[File:Morning view, Laguna de Bay, from Hotel Vivere - panoramio.jpg|thumb|Patchwork of very large fish pens in [[Laguna de Bay]], [[Philippines]]]]
In the [[Philippines]], traditional enclosures used to farm fish directly on shallow bodies of water are called '''fish pens'''. They differ from fish cages in that fish pens are not floating and do not have an artificial bottom. Instead, the seabed, riverbed, or the lakebed provides the floor of the enclosure. They are usually much larger than fish cages and come in various shapes like circles, squares, or rectangles. The fences that enclose the fish pen area are made from bamboo or wooden poles, netting, and ropes. The poles are sunk into the substrate at depths of {{convert|15|to|30|cm|ft}}. Fish pens often have a hut [[Stilt house|raised on stilts]] nearby that function as a warehouse and accommodations for caretakers that may be necessary to guard against [[poachers]].<ref name="SEAFDEC">{{cite book |title=International Workshop on Pen and Cage Culture of Fish |date=February 1979 |publisher=Aquaculture Department, Southeast Asian Fisheries Development Center; International Development Research Centre |url=https://repository.seafdec.org.ph/handle/10862/1511}}</ref>

Fish pens commonly cover large areas of bodies of water (both freshwater and marine) in the Philippines, similar to farm plots. Licenses are required to operate fish pens, and operators are usually granted a limited area for fish farming.<ref name="Pullin"/> 

Different pen sizes are required for different species of fish.<ref name="FAOAquaculture"/> Freshwater fish pens are traditionally used to farm [[milkfish]] (''[[Chanos chanos]]'') using wild-caught [[Fingerling (fish)|fingerling]]s, with much higher survival and harvesting yields than conventional fish pond farming. They can also be used to farm other food fish like the Nile tilapia (''[[Oreochromis niloticus]]''), but in general, fish cages are preferred for smaller fish species instead.<ref name="SEAFDEC"/><ref name="Pullin">{{cite journal |last1=Pullin |first1=R.S.V. |title=Fish pens of Laguna de Bay, Philippines |journal=ICLARM Newsletter |date=1981 |volume=4 |issue=4 |pages=11–13 |url=https://worldfishcenter.org/publication/fish-pens-laguna-de-bay-philippines}}</ref> Marine fish pens are commonly used to farm wild-caught juvenile [[grouper]]s.<ref name="FAOAquaculture">{{cite book |title=Rural Aquaculture in the Philippines |url=https://www.fao.org/3/x6943e/x6943e06.htm |author=Wilfredo G. Yap |year=1999 |publisher=FAO |chapter=Overview of Philippine Aquaculture |chapter-url=https://www.fao.org/4/x6943e/x6943e06.htm}}</ref>

Due to their open-water nature and their typically large areas, supplemental feeding is typically not required for fish pens (unlike in fish cages and fish ponds), though some operators may provide additional feed for fingerlings like bread crumbs, [[fish meal]], [[egg yolk]], or plant leaves.<ref name="SEAFDEC"/>

Fish pens are cheap and generate high profit margins, but they are more vulnerable to [[typhoon]]s, [[flood]]s, [[water pollution]] (including [[algal bloom]]s and oxygen depletion), and fry shortage.<ref name="Delmendo">{{cite book |last1=Delmendo |first1=Medina N. |last2=Delmendo |first2=B.H. |title=Small-Scale Aquaculture Operations in the ASEAN Countries |date=1987 |publisher=ASEAN/UNDP/FAO Regional Small-Scale Coastal Fisheries Development Project |location=Manila |url=https://www.fao.org/4/ag159e/AG159E00.htm#TOC}}</ref><ref name="SEAFDEC"/>

=== 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 rear the fish in large cages floating in the water.<ref>{{Cite web|title=Salmon Aquaculture • Georgia Strait Alliance|url=https://georgiastrait.org/issues/other-issues/salmon-aquaculture/|access-date=2021-12-24|website=Georgia Strait Alliance|language=en}}</ref> The fish are living in natural water but are isolated with a net. Because 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:<ref>{{Cite report |last1=Braaten |first1=Bjørn |last2=Aure |first2=Jan |last3=Ervik |first3=Arne |last4=Boge |first4=Erik |date=1983 |title=Pollution problems in Norwegian fish farming |url=https://imr.brage.unit.no/imr-xmlui/handle/11250/103766}}</ref>

# A good interchange of water and also a high replacement of bottom water.
# At all depths should be a good current condition. This is necessary because the organic particles should be able to be carried away using the current.
# 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 {{convert|10|m|ft|0}} or more above the bottom, so depth is important.

Despite these important site conditions, the open net pen method was very popular in Norway and China. This is because of the cost friendliness and efficiency of this method.<ref>Upton, H. F., & Buck, E. H. (2010). Open Ocean Culture. Congressional Research Service. Published. https://nationalaglawcenter.org/wp-content/uploads/assets/crs/RL32694.pdf</ref>

==== Negative external effects ====
Because of the ocean's water flow and other reasons, open net pen culture is seen as a high-risk method for the environment.<ref>{{Cite web |title=Aquaculture Methods |url=https://www.seachoice.org/info-centre/aquaculture/aquaculture-methods/ |access-date=2022-08-02 |website=SeaChoice |language=en-CA}}</ref> The flow allows chemicals, parasites, waste and diseases to spread in the enclosed environment, and this is not beneficial for the natural environment. Another negative consequence is the high escape rate of the cultured fish from these open net pens. These escaped fish also pose a high risk to the surrounding ecosystems.

The amount of organic waste produced by fish farms is also alarming. A salmon farm in [[Scotland]], for instance, is estimated to produce as much organic waste as equivalent to a town of people between 10,000 and 20,000 people each year.<ref>{{Cite web |title=Facts {{!}} Seaspiracy Website |url=https://www.seaspiracy.org/facts |access-date=2022-03-12 |website=SEASPIRACY |language=en}}</ref>

Today 50% of the world's seafood is farm-raised.<ref>{{Cite web |title=50% of our seafood is farm raised |url=https://www.carolinacoastonline.com/news_times/opinions/letters_to_editor/article_efe859be-ba70-11e2-b124-001a4bcf887a.html |access-date=2022-07-11 |website=Carolina Coast Online |date=11 May 2013 |language=en}}</ref>

=== Irrigation ditch or pond systems ===
[[File:Community fish-farming ponds in the rural town of Masi Manimba, DRC (7609946524).jpg|alt=A row of square artificial ponds, with trees on either side|thumb|These fish-farming ponds were created as a [[cooperative]] project in a rural village in the [[Democratic Republic of Congo|Congo]].]]

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).<ref>{{Cite web |title=Factors to Consider in Selecting a Farm Irrigation System {{!}} UGA Cooperative Extension |url=https://extension.uga.edu/publications/detail.html?number=B882&title=Factors%20to%20Consider%20in%20Selecting%20a%20Farm%20Irrigation%20System |access-date=2022-07-11 |website=extension.uga.edu}}</ref>

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.<ref>{{Cite web |date=2021-06-19 |title=Fish Farming In Nigeria - Fish Species In Nigeria {{!}} Agri Farming |url=https://www.agrifarming.in/fish-farming-in-nigeria-fish-species-in-nigeria |access-date=2022-07-11 |website=www.agrifarming.in |language=en-US}}</ref>

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.<ref>{{Cite journal |last1=Magnoni |first1=Leonardo J. |last2=Novais |first2=Sara C. |last3=Eding |first3=Ep |last4=Leguen |first4=Isabelle |last5=Lemos |first5=Marco F. L. |last6=Ozório |first6=Rodrigo O. A. |last7=Geurden |first7=Inge |last8=Prunet |first8=Patrick |last9=Schrama |first9=Johan W. |date=2019-04-24 |title=Acute Stress and an Electrolyte- Imbalanced Diet, but Not Chronic Hypoxia, Increase Oxidative Stress and Hamper Innate Immune Status in a Rainbow Trout (Oncorhynchus mykiss) Isogenic Line |journal=Frontiers in Physiology |volume=10 |pages=453 |doi=10.3389/fphys.2019.00453 |issn=1664-042X |pmc=6491711 |pmid=31068834|doi-access=free }}</ref>

==== Composite fish culture ====
The composite fish culture system is a technology developed in India by the [[Indian Council of Agricultural Research]] 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.<ref>{{cite web|url=http://www.fao.org/docrep/field/003/AC229E/AC229E07.htm|title=Lecture Notes on Composite Fish Culture and its Extension in India|access-date=30 January 2016}}</ref><ref>{{cite web|url=http://harfish.gov.in/technology.htm|archive-url=https://web.archive.org/web/20170309061425/http://harfish.gov.in/technology.htm|url-status=dead|archive-date=2017-03-09|title=Ornamental Fish Breeding|publisher=Fisheries Department Haryana, Chandigarh, India}}</ref> As a result, the food available in all the parts of the pond is used. Fish used in this system include [[catla]] and [[silver carp]] (surface feeders), [[rohu]] (a column feeder), and [[mrigal]] and [[common carp]] (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&nbsp;kg of fish per hectare per year.<ref>{{Cite web |title=INTEGRATED LIVESTOCK-FISH PRODUCTION SYSTEMS |url=https://www.fao.org/3/ac155e/AC155E09.htm |access-date=2022-07-11 |website=www.fao.org}}</ref>

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. Thus, 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.<ref>{{Cite web |title=SEED PRODUCTION |url=https://www.fao.org/3/ac182e/AC182E01.htm |access-date=2022-07-11 |website=www.fao.org}}</ref>

=== Integrated recycling systems ===
{{Main|Aquaponics}}
[[File:Unifish fish farm.JPG|thumb|Aerators in a fish farm ([[Ararat plain]], [[Armenia]])]]
One of the largest problems with freshwater pisciculture is that it can use a million gallons of water per acre (about 1 m<sup>3</sup> of water per m<sup>2</sup>) 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 Alchemy Institute]] 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 grow in the tanks when the tanks are properly fertilized.<ref>{{Cite web |title=Tank culture of tilapia |url=https://thefishsite.com/articles/tank-culture-of-tilapia |access-date=2022-07-11 |website=thefishsite.com |date=November 2005 |language=en}}</ref>

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]] to [[nitrate]]s, and the plants are fertilized by the nitrates and [[phosphate]]s.Other wastes are strained out by the hydroponic media, which double as an aerated pebble-bed filter.<ref>{{Cite web |title=Aquaculture |url=https://www.environmentalleverage.com/Aquaculture.htm |access-date=2022-07-11 |website=www.environmentalleverage.com}}</ref>

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]]s (e.g. [[parsley]] and [[basil]]), which command premium prices in small quantities all year long. The most common customers are [[restaurant]] wholesalers.<ref>{{Cite web |last1=Pap |first1=Dawn |last2=rea |date=2019-05-22 |title=What are the Different Types of Restaurant Suppliers? |url=https://upserve.com/restaurant-insider/what-are-the-different-types-of-restaurant-suppliers/ |access-date=2022-07-11 |website=Restaurant Insider |language=en-US}}</ref>

Since the system lives in a [[greenhouse]], it adapts to almost all temperate climates, and may also adapt to [[tropical climate]]s.
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 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.{{Citation needed|date=February 2021}}

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 recirculation technology|Greenfish Initiative]].<ref>Berggren, Alexandra (2007) [http://www.stockholmresilience.org/download/18.aeea46911a31274279800082877/Berggren+NGG+07+Thesis.pdf Aquaculture in Sweden towards a sustainable future?"] Master's Thesis, Stockholm University</ref><ref>McLarney, William ''Freshwater Aquaculture: A Handbook for Small Scale Fish Culture in North America''</ref>

=== Classic fry farming ===
This is also called a "flow through system".<ref>{{cite web|url=http://dnr.wi.gov/org/caer/cea/assistance/aquaculture/info.htm |title=Aquaculture |access-date=30 January 2016 |url-status=dead |archive-url=https://web.archive.org/web/20120106204931/http://dnr.wi.gov/org/caer/cea/assistance/aquaculture/info.htm |archive-date=January 6, 2012 }}</ref> Trout and other sport fish are often raised from eggs to [[Spawn (biology)#Fry|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]]. Although European eel larvae can survive for several weeks, the full life cycle has not yet been achieved in captivity.<ref>{{Cite journal |last1=Jéhannet |first1=Pauline |last2=Palstra |first2=Arjan P. |last3=Heinsbroek |first3=Leon T. N. |last4=Kruijt |first4=Leo |last5=Dirks |first5=Ron P. |last6=Swinkels |first6=William |last7=Komen |first7=Hans |date=2021-06-08 |title=What Goes Wrong during Early Development of Artificially Reproduced European Eel Anguilla anguilla? Clues from the Larval Transcriptome and Gene Expression Patterns |journal=Animals |volume=11 |issue=6 |pages=1710 |doi=10.3390/ani11061710 |issn=2076-2615 |pmc=8227761 |pmid=34201077|doi-access=free }}</ref>