In the aquaculture industry, good animal husbandry means keeping fish clean, well-fed, healthy and free of overcrowding.[40]​ One solution to keeping farmed fish healthy is to contain them in anti-fouling copper alloy nets and structures.[41]​.

Researchers have attributed copper's resistance to biofouling, even in temperate waters, to two possible mechanisms: 1) a delayed colonization sequence through the release of antimicrobial copper ions, thus preventing the adhesion of microbial mats to marine surfaces;[42]​ and, 2) separation layers containing corrosive products and spores of juvenile or macrofouling organisms.[43]​.

The most important requirement for optimal biofouling resistance is that copper alloys must be freely exposed or electrically isolated from less noble alloys and cathodic protection. Galvanic coupling to less noble alloys and cathodic protection prevent the release of copper ions from surface films and therefore reduce resistance to biofouling.[44]​.

As temperatures increase and water velocities decrease in marine waters, biofouling rates increase dramatically. However, copper's resistance to biofouling is observed even in temperate waters. Studies in La Herradura Bay, Coquimbo, Chile, where biofouling conditions are extreme, demonstrated that a copper alloy (90% copper, 10% nickel) prevented macrofouling organisms.[43]​.

Copper alloys used in seawater service have low rates of general corrosion, but also have high resistance to many localized forms of corrosion. A technical discussion is available on various types of corrosion, application considerations (e.g. depth of facilities, effect of contaminated waters, sea conditions) and the corrosion characteristics of various copper alloys used in aquaculture networks (i.e. copper-nickel, copper-zinc and copper-silicon[45]​).

Before the late 1700s, hulls were made almost entirely of wood, often white oak. Sacrificial planking was the common mode of hull protection. This technique included wrapping a protective layer of 1/2-inch-thick wood, often pine, around the hull to decrease the risk of damage. This layer was regularly replaced when infested with marine borers.[46] Bioresistant copper coating for ship hulls was developed at the turn of the century. In 1761, the hull of the British Royal Navy frigate HMS Alarm was sheathed entirely in copper to prevent attack by Teredo worms in tropical waters.[47] Copper reduced biological contamination of the hull, allowing ships to move faster than those without copper-clad hulls.

Many complicated factors influence the environmental performance of copper alloys in aquaculture operations. This reference summarizes a technical description of antifouling mechanisms, fish health and welfare, fish losses due to escapes and predator attacks, and reduction of life cycle environmental impacts.[48]​.

Contenido

Se están implementando aleaciones de latón de cobre-zinc en operaciones de acuicultura a escala comercial en Asia, América del Sur y los EE. UU. (Hawái). Actualmente se están llevando a cabo investigaciones exhaustivas, que incluyen demostraciones y ensayos, sobre otras dos aleaciones de cobre: cobre-níquel y cobre-silicio. Cada uno de estos tipos de aleaciones tiene la capacidad inherente de reducir la contaminación biológica, el desperdicio de la pluma, las enfermedades y la necesidad de antibióticos, al tiempo que mantiene la circulación de agua y los requisitos de oxígeno. También se están considerando otros tipos de aleaciones de cobre para investigación y desarrollo en operaciones de acuicultura.

La Universidad de New Hampshire está realizando experimentos bajo los auspicios de la Asociación Internacional del Cobre (ICA)[49]​ para evaluar la respuesta estructural, hidrodinámica y antiincrustante de las mallas de aleación de cobre. Los factores que se determinarán a partir de estos experimentos, como el arrastre, las cargas dinámicas de los corrales, la pérdida de material y el crecimiento biológico, bien documentados para las redes de nailon, pero no completamente comprendidos en el caso de las redes de aleación de cobre y níquel, ayudarán a diseñar recintos para corrales de peces hechos de estas aleaciones. El Instituto de Investigación Pesquera del Mar del Este de China, en Shanghái, China, también está llevando a cabo investigaciones experimentales sobre aleaciones de cobre para ICA.

Copper and zinc alloys

Mitsubishi-Shindoh Co., Ltd. has developed a proprietary copper-zinc brass alloy, called UR30,[50]​ designed specifically for aquaculture operations. The alloy, which is composed of 64% copper, 35.1% zinc, 0.6% tin and 0.3% nickel, resists mechanical abrasion when formed into wires and manufactured into chain links, woven or other types of flexible mesh. Corrosion rates depend on the depth of immersion and seawater conditions. The average corrosion rate reported for the alloy is <5 μm/year based on two- and five-year exposure tests in seawater.[51]​.

Ashimori Industry Company, Ltd., has installed approximately 300 flexible pens with UR30 woven chain link mesh in Japan for raising Seriola (i.e., horse mackerel, amberjack), kingfish, hamachi). The company has installed an additional 32 brass pens for raising Atlantic salmon at Van Diemen Aquaculture operations in Tasmania, Australia. In Chile, EcoSea Farming S. A. has installed a total of 62 woven chain link brass mesh pens for raising trout and Atlantic salmon.[51]​ Demonstrations and trials using flexible UR30 woven chain link pens and other forms of mesh and a range of copper alloys are underway in Panama, China, Korea, Turkey and the USA.

To date, in over 10 years of aquaculture experience, chain link mesh made from these brass alloys has not suffered from dezincification, stress corrosion cracking, or erosion corrosion.

Copper-nickel alloys

Copper-nickel alloys were developed specifically for seawater applications more than five decades ago. These alloys are currently being investigated for their potential use in aquaculture.

Copper-nickel alloys for marine applications typically have 90% copper, 10% nickel, and small amounts of manganese and iron to improve corrosion resistance. The seawater corrosion resistance of copper-nickel alloys results in a thin, adherent protective surface film that forms naturally and rapidly on the metal upon exposure to clean seawater.[52]​.

The rate of formation of corrosion protection depends on temperature. For example, at 27°C (i.e. a common inlet temperature in the Middle East), rapid film formation and good corrosion protection can be expected within a few hours. At 16°C, the protection may take 2 to 3 months to mature. But once a good surface film is formed, corrosion rates decrease, typically to 0.02-0.002 mm/year, as protective layers develop over a period of years.[53] These alloys have good resistance to chloride pitting and crevice corrosion and are not susceptible to chloride stress corrosion.

Copper-silicon alloys

Copper-silicon has a long history of use as screws, nuts, bolts, washers, cotter pins, lag screws and staples on wooden sailboats in marine environments. Alloys are often composed of copper, silicon and manganese. The inclusion of silicon strengthens the metal.

As with copper-nickel alloys, the corrosion resistance of copper and silicon is due to protective films that form on the surface over a period of time. General corrosion rates of 0.025–0.050 mm have been observed in still waters. This rate decreases toward the lower end of the range at long-term exposures (e.g., 400 to 600 days). There is generally no pitting with silicon bronzes. There is also good resistance to erosion corrosion up to moderate flow rates. Because copper-silicon is solderable, rigid pens can be constructed from this material. Additionally, because copper-silicon welded mesh is lighter than copper-zinc chain links, aquaculture enclosures made with copper-silicon may be lighter and therefore a potentially less expensive alternative.

Luvata Appleton, LLC, is researching and developing a line of woven and welded copper alloy meshes, including a patent-pending copper-silicon alloy, which is marketed under the trade name Seawire.[54] The company has developed copper-silicon alloy meshes for rearing various marine organisms in test trials that are now in various stages of evaluation. These include cobia farming in Panama, lobsters in the US state of Maine and crabs in the Chesapeake Bay. The company is working with several universities to study its material, including the University of Arizona to study shrimp, the University of New Hampshire to study cod, and Oregon State University to study oysters.

Biofouling is one of the biggest problems in aquaculture.[12]​ Biofouling occurs on non-copper materials in the marine environment, including the surfaces of fish pens and nets.[2]​ For example, the open area of ​​a mesh submerged for just seven days in a Tasmanian aquaculture operation was observed to decrease by 37% as a result of biofouling.[13]​.

The biofouling process begins when algal spores, marine invertebrate larvae, and other organic material adhere to submerged surfaces in marine environments (e.g., fishing nets in aquaculture). The bacteria then encourage the attachment of unwanted secondary colonizers.[2][14]​.

Biological contamination has strong negative impacts on aquaculture operations. Water flow and dissolved oxygen are inhibited due to clogged nets in fish pens.[15]​[16]​ The end result is often sick fish due to infections, such as pen liver disease,[17]​ amoebic gill disease,[18]​ and parasites.[19][20]​ Other negative impacts include increased fish mortality, decreased rates of of fish growth, premature harvesting of fish, reduced value and profitability of fishery products, and an adversely affected environment near fish farms.[2]​[21][22]​.

Biofouling adds enormous weight to submerged fishing nets. Two-hundred-fold weight gains have been reported.[23]​[24]​ This translates, for example, to two thousand pounds of unwanted organisms attached to what was once a clean 10-pound fish net. In South Australia, biofouling weighing 6.5 tonnes (approximately 13,000 lb) was observed in a fishing net.[25] This additional load often results in net breaks and additional maintenance costs.

To combat biofouling parasites in fish aquaculture, treatment protocols such as cypermethrin, azamethiphos and emamectin benzoate can be administered, but these have been found to have detrimental environmental effects, for example in lobster operations.[26]​[27][28][29][30]​.

To treat diseases in fish raised in biofouled nets, antibiotics are administered to fish populations. Antibiotics can have unwanted long-term health effects on consumers and in coastal environments near aquaculture operations.[31] To combat biofouling, operators often implement costly maintenance measures, such as frequent changing of nets, cleaning/removing unwanted organisms from nets, net repairs, and chemical treatment, including antimicrobial coatings on nets. nylon.[18]​[32]​[33]​ In some sectors of the European aquaculture industry, cleaning biologically contaminated fish and shellfish pens can cost between 5% and 20% of their market value. Heavy fouling can reduce the salable product on networks by 60 to 90%.[21]​.

Antifouling coatings are often used on nylon nets because the process is more economical than manual cleaning.[34]​ When nylon nets are coated with antifouling compounds, the coatings repel biofouling over a period of time, typically several weeks to several months. However, the nets eventually succumb to biological contamination. Antifouling coatings containing cuprous oxide algaecides/biocides "Copper(I) Oxide") are the coatings technology used almost exclusively in the fish farming industry today. Treatments generally peel off in a few weeks to six or eight months.[2][35]​.

The biofouled nets are replaced after several months of service, depending on environmental conditions, in a complicated, expensive and laborious operation that involves divers and specialized personnel. During this process, live fish in the nets must be transferred to clean pens, causing undue stress and suffocation resulting in the loss of some fish.[36] Biofouled nets that can be reused are washed ashore by manual brushing and scrubbing or with a high-pressure water hose. They are then dried and re-impregnated with antifouling coatings.[24][35][37][38]​.

A line of net cleaners is available for in-situ washing where permitted.[39]​ But, even where not permitted by environmental, fisheries, maritime and health authorities, if the lack of dissolved oxygen in submerged pens creates an emergency condition that endangers fish health, divers can be deployed with special in-situ cleaning machinery to remove biofouling from nets.[35]​.

The aquaculture industry is addressing the negative environmental impacts of its operations. As the industry evolves, a cleaner and more sustainable aquaculture industry is expected to emerge, one that increasingly relies on materials with anti-fouling, anti-corrosion and strong structural properties, such as copper alloys.

In the aquaculture industry, good animal husbandry means keeping fish clean, well-fed, healthy and free of overcrowding.[40]​ One solution to keeping farmed fish healthy is to contain them in anti-fouling copper alloy nets and structures.[41]​.

Researchers have attributed copper's resistance to biofouling, even in temperate waters, to two possible mechanisms: 1) a delayed colonization sequence through the release of antimicrobial copper ions, thus preventing the adhesion of microbial mats to marine surfaces;[42]​ and, 2) separation layers containing corrosive products and spores of juvenile or macrofouling organisms.[43]​.

The most important requirement for optimal biofouling resistance is that copper alloys must be freely exposed or electrically isolated from less noble alloys and cathodic protection. Galvanic coupling to less noble alloys and cathodic protection prevent the release of copper ions from surface films and therefore reduce resistance to biofouling.[44]​.

As temperatures increase and water velocities decrease in marine waters, biofouling rates increase dramatically. However, copper's resistance to biofouling is observed even in temperate waters. Studies in La Herradura Bay, Coquimbo, Chile, where biofouling conditions are extreme, demonstrated that a copper alloy (90% copper, 10% nickel) prevented macrofouling organisms.[43]​.

Copper alloys used in seawater service have low rates of general corrosion, but also have high resistance to many localized forms of corrosion. A technical discussion is available on various types of corrosion, application considerations (e.g. depth of facilities, effect of contaminated waters, sea conditions) and the corrosion characteristics of various copper alloys used in aquaculture networks (i.e. copper-nickel, copper-zinc and copper-silicon[45]​).

Before the late 1700s, hulls were made almost entirely of wood, often white oak. Sacrificial planking was the common mode of hull protection. This technique included wrapping a protective layer of 1/2-inch-thick wood, often pine, around the hull to decrease the risk of damage. This layer was regularly replaced when infested with marine borers.[46] Bioresistant copper coating for ship hulls was developed at the turn of the century. In 1761, the hull of the British Royal Navy frigate HMS Alarm was sheathed entirely in copper to prevent attack by Teredo worms in tropical waters.[47] Copper reduced biological contamination of the hull, allowing ships to move faster than those without copper-clad hulls.

Many complicated factors influence the environmental performance of copper alloys in aquaculture operations. This reference summarizes a technical description of antifouling mechanisms, fish health and welfare, fish losses due to escapes and predator attacks, and reduction of life cycle environmental impacts.[48]​.

Contenido

Se están implementando aleaciones de latón de cobre-zinc en operaciones de acuicultura a escala comercial en Asia, América del Sur y los EE. UU. (Hawái). Actualmente se están llevando a cabo investigaciones exhaustivas, que incluyen demostraciones y ensayos, sobre otras dos aleaciones de cobre: cobre-níquel y cobre-silicio. Cada uno de estos tipos de aleaciones tiene la capacidad inherente de reducir la contaminación biológica, el desperdicio de la pluma, las enfermedades y la necesidad de antibióticos, al tiempo que mantiene la circulación de agua y los requisitos de oxígeno. También se están considerando otros tipos de aleaciones de cobre para investigación y desarrollo en operaciones de acuicultura.

La Universidad de New Hampshire está realizando experimentos bajo los auspicios de la Asociación Internacional del Cobre (ICA)[49]​ para evaluar la respuesta estructural, hidrodinámica y antiincrustante de las mallas de aleación de cobre. Los factores que se determinarán a partir de estos experimentos, como el arrastre, las cargas dinámicas de los corrales, la pérdida de material y el crecimiento biológico, bien documentados para las redes de nailon, pero no completamente comprendidos en el caso de las redes de aleación de cobre y níquel, ayudarán a diseñar recintos para corrales de peces hechos de estas aleaciones. El Instituto de Investigación Pesquera del Mar del Este de China, en Shanghái, China, también está llevando a cabo investigaciones experimentales sobre aleaciones de cobre para ICA.

Copper and zinc alloys

Mitsubishi-Shindoh Co., Ltd. has developed a proprietary copper-zinc brass alloy, called UR30,[50]​ designed specifically for aquaculture operations. The alloy, which is composed of 64% copper, 35.1% zinc, 0.6% tin and 0.3% nickel, resists mechanical abrasion when formed into wires and manufactured into chain links, woven or other types of flexible mesh. Corrosion rates depend on the depth of immersion and seawater conditions. The average corrosion rate reported for the alloy is <5 μm/year based on two- and five-year exposure tests in seawater.[51]​.

Ashimori Industry Company, Ltd., has installed approximately 300 flexible pens with UR30 woven chain link mesh in Japan for raising Seriola (i.e., horse mackerel, amberjack), kingfish, hamachi). The company has installed an additional 32 brass pens for raising Atlantic salmon at Van Diemen Aquaculture operations in Tasmania, Australia. In Chile, EcoSea Farming S. A. has installed a total of 62 woven chain link brass mesh pens for raising trout and Atlantic salmon.[51]​ Demonstrations and trials using flexible UR30 woven chain link pens and other forms of mesh and a range of copper alloys are underway in Panama, China, Korea, Turkey and the USA.

To date, in over 10 years of aquaculture experience, chain link mesh made from these brass alloys has not suffered from dezincification, stress corrosion cracking, or erosion corrosion.

Copper-nickel alloys

Copper-nickel alloys were developed specifically for seawater applications more than five decades ago. These alloys are currently being investigated for their potential use in aquaculture.

Copper-nickel alloys for marine applications typically have 90% copper, 10% nickel, and small amounts of manganese and iron to improve corrosion resistance. The seawater corrosion resistance of copper-nickel alloys results in a thin, adherent protective surface film that forms naturally and rapidly on the metal upon exposure to clean seawater.[52]​.

The rate of formation of corrosion protection depends on temperature. For example, at 27°C (i.e. a common inlet temperature in the Middle East), rapid film formation and good corrosion protection can be expected within a few hours. At 16°C, the protection may take 2 to 3 months to mature. But once a good surface film is formed, corrosion rates decrease, typically to 0.02-0.002 mm/year, as protective layers develop over a period of years.[53] These alloys have good resistance to chloride pitting and crevice corrosion and are not susceptible to chloride stress corrosion.

Copper-silicon alloys

Copper-silicon has a long history of use as screws, nuts, bolts, washers, cotter pins, lag screws and staples on wooden sailboats in marine environments. Alloys are often composed of copper, silicon and manganese. The inclusion of silicon strengthens the metal.

As with copper-nickel alloys, the corrosion resistance of copper and silicon is due to protective films that form on the surface over a period of time. General corrosion rates of 0.025–0.050 mm have been observed in still waters. This rate decreases toward the lower end of the range at long-term exposures (e.g., 400 to 600 days). There is generally no pitting with silicon bronzes. There is also good resistance to erosion corrosion up to moderate flow rates. Because copper-silicon is solderable, rigid pens can be constructed from this material. Additionally, because copper-silicon welded mesh is lighter than copper-zinc chain links, aquaculture enclosures made with copper-silicon may be lighter and therefore a potentially less expensive alternative.

Luvata Appleton, LLC, is researching and developing a line of woven and welded copper alloy meshes, including a patent-pending copper-silicon alloy, which is marketed under the trade name Seawire.[54] The company has developed copper-silicon alloy meshes for rearing various marine organisms in test trials that are now in various stages of evaluation. These include cobia farming in Panama, lobsters in the US state of Maine and crabs in the Chesapeake Bay. The company is working with several universities to study its material, including the University of Arizona to study shrimp, the University of New Hampshire to study cod, and Oregon State University to study oysters.