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Recently, '''[[copper alloys]]''' have become important netting materials in the '''[[aquaculture]]''' (the farming of [[aquatic animal|aquatic organisms]] including [[fish farming]]) industry. Various other materials, such as [[nylon]], [[polyester]], [[polypropylene]], [[polyethylene]], plastic-coated welded [[wire]], [[rubber]], patented [[rope]] products (Spectra®, Thorn-D®, Dyneema®), and [[galvanized steel]] are also used for netting in aquaculture fish enclosures around the world.<ref>Offshore Aquaculture in the United States: Economic considerations, implications, and opportunities, U.S. Department of Commerce, National Oceanic & Atmospheric Administration, July 2008, page 53</ref><ref name="Braithwaite">Braithwaite, R.A. and McEvoy, L.A. (2005), Marine biofouling on fish farms and its remediation, Advances in Marine Biology, Vol. 47, pp. 216-252)</ref><ref>http://www.sterlingnets.com/fishfarm.html</ref><ref>http://www.industrialnetting.com/aquaculture.htm </ref><ref>Southern Regional Aquaculture Center at http://aquanic.org/publicat/usda_rac/efs/srac/162fs.pdf </ref> All of these materials are selected for a variety of reasons, including design feasibility, [[material strength]], cost, and [[corrosion resistance]].
Recently, [[copper alloys]] have become important netting materials in the [[aquaculture]] (the farming of [[aquatic animal|aquatic organisms]] including [[fish farming]]) industry. Various other materials, such as [[nylon]], [[polyester]], [[polypropylene]], [[polyethylene]], plastic-coated welded [[wire]], [[rubber]], patented [[rope]] products (Spectra®, Thorn-D®, Dyneema®), and [[galvanized steel]] are also used for netting in [[aquaculture]] fish enclosures around the world.<ref>Offshore Aquaculture in the United States: Economic considerations, implications, and opportunities, U.S. Department of Commerce, National Oceanic & Atmospheric Administration, July 2008, p. 53</ref><ref name=Braithwaite>{{cite journal|pmid=15596168}}</ref><ref>{{cite web|url=http://www.sterlingnets.com/fishfarm.html |title=Commercial and research fish farming and aquaculture netting and supplies |publisher=Sterlingnets.com |date= |accessdate=2010-06-16}}</ref><ref>{{cite web|url=http://www.industrialnetting.com/aquaculture.htm |title=Aquaculture Netting by Industrial Netting |publisher=Industrialnetting.com |date= |accessdate=2010-06-16}}</ref><ref>Southern Regional Aquaculture Center at http://aquanic.org/publicat/usda_rac/efs/srac/162fs.pdf </ref> All of these materials are selected for a variety of reasons, including design feasibility, [[material strength]], cost, and [[corrosion resistance]].


What sets copper alloys apart from the other materials is that copper alloys are [[antimicrobial]], that is, they destroy [[bacteria]], [[viruses]], [[fungi]], [[algae]], and other [[microbes]]. ''(For information about the antimicrobial properties of copper and its alloys, see these articles:'' [[Antimicrobial properties of copper]], ''and'' [[Antimicrobial copper alloy touch surfaces]]).
What sets copper alloys apart from the other materials is that copper alloys are [[antimicrobial]], that is, they destroy [[bacteria]], [[viruses]], [[fungi]], [[algae]], and other [[microbes]]. (For information about the antimicrobial properties of copper and its alloys, see [[Antimicrobial properties of copper]] and [[Antimicrobial copper alloy touch surfaces]]).


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]], [[tubeworms]], [[barnacles]], [[mollusks]], and other organisms on man-made marine structures.<ref>Marine Fouling and its Prevention, Wood Hole Oceanographic Institution, 1952, United States Naval Institute, Annapolis, Maryland, USA</ref> By inhibiting microbial growth, copper alloy aquaculture cages avoid the need for costly net changes that are necessary with other materials. The resistance of organism growth on copper alloy nets also provides a cleaner and healthier environment for farmed fish to grow and thrive.
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]], [[tubeworms]], [[barnacles]], [[mollusks]], and other organisms on man-made marine structures.<ref>Marine Fouling and its Prevention, Wood Hole Oceanographic Institution, 1952, United States Naval Institute, Annapolis, Maryland, USA</ref> By inhibiting microbial growth, copper alloy aquaculture cages avoid the need for costly net changes that are necessary with other materials. The resistance of organism growth on copper alloy nets also provides a cleaner and healthier environment for farmed fish to grow and thrive.
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== Importance of aquaculture in feeding people around the world ==
== Importance of aquaculture in feeding people around the world ==
Also see: [[Aquaculture]] and [[Fish farming]]
{{seealso|Aquaculture|Fish farming}}
<br /><br />


Much has been written about the degradation and depletion of natural fish stocks in [[river]]s, [[estuaries]], and the [[ocean]]s.<ref>http://en.wikipedia.org/wiki/Overfishing</ref><ref>Myers, R.A. and Worm, B., (2003), Rapid worldwide depletion of predatory fish communities, Nature, Vol. 423, pp. 280-283, May 15, http://www.nature.com/nature/journal/v423/n6937/abs/nature01610.html</ref><ref>The State of World Fisheries and Aquaculture (SOFIA), Biennial Report, 2005, as summarized in Food and Agriculture Organization of the United Nations, http://www.fao.org/newsroom/en/news/2005/100095/index.html</ref> Because industrial fishing has become extremely efficient, ocean stocks of large fish, such as [[tuna]], [[cod]], and [[halibut]] have declined by 90% in the past 50 years.<ref>The Next Seafood Frontier: The Ocean, April 28, 2009, references article in Nature</ref><ref>http://money.cnn.com/2009/04/27/smallbusiness/farming_the_open_oceans.fsb</ref><ref>Tietenberg, T.H. (2006), Environmental and Natural Resource Economics: A Contemporary Approach, page 28, Pearson/Addison Wesley. ISBN 9780321305046</ref>
Much has been written about the degradation and depletion of natural fish stocks in [[river]]s, [[estuaries]], and the [[ocean]]s (see also [[overfishing]]).<ref>{{cite journal|doi=10.1038/nature01610}}</ref><ref>[http://www.fao.org/newsroom/en/news/2005/100095/index.html The State of World Fisheries and Aquaculture (SOFIA), Biennial Report, 2005], as summarized in Food and Agriculture Organization of the United Nations</ref> Because industrial fishing has become extremely efficient, ocean stocks of large fish, such as [[tuna]], [[cod]], and [[halibut]] have declined by 90% in the past 50 years.<ref>The Next Seafood Frontier: The Ocean, April 28, 2009, references article by Myers in Nature</ref><ref>{{cite web|author=By Alessandra Bianchi |url=http://money.cnn.com/2009/04/27/smallbusiness/farming_the_open_oceans.fsb |title=The next seafood frontier: The open ocean - Apr. 28, 2009 |publisher=Money.cnn.com |date=2009-04-28 |accessdate=2010-06-16}}</ref><ref>Tietenberg, T.H. (2006), Environmental and Natural Resource Economics: A Contemporary Approach, p. 28, Pearson/Addison Wesley. ISBN 0321305043</ref>


[[Aquaculture]], an industry that has emerged only in recent decades, has become one of the fastest growing sectors of the world food economy.<ref name=Braithwaite></ref> Aquaculture already supplies more than half of the world’s demand for fish.<ref>Half Of Fish Consumed Globally Is Now Raised On Farms, Study Finds Science Daily, September 8, 2009</ref> This percentage is predicted to increase dramatically over the next few decades.
[[Aquaculture]], an industry that has emerged only in recent decades, has become one of the fastest growing sectors of the world food economy.<ref name=Braithwaite/> Aquaculture already supplies more than half of the world’s demand for fish.<ref>Half Of Fish Consumed Globally Is Now Raised On Farms, Study Finds Science Daily, September 8, 2009</ref> This percentage is predicted to increase dramatically over the next few decades.


== The problem of biofouling in aquaculture ==
== The problem of biofouling in aquaculture ==
[[Biofouling]] is one of the most important problems in aquaculture.<ref>Design Guide: Copper Alloy Mesh in Marine Aquaculture, International Copper Research Association Inc. (INCRA), 1984</ref> Biofouling occurs on non-copper materials in the marine environment, including [[fish cage]] surfaces and [[fish net|nettings]].<ref name=Braithwaite></ref> For example, it was noted that the open area of a mesh immersed for only seven days in a [[Tasmanian]] aquaculture operation decreased by 37% as a result of biofouling.<ref>Hodson, S.L., Lewis, T.E., and Burke, C.M., (1995), In situ quantification of fish-cage fouling by underwater photography and image analysis, Biofouling¸ Vol. 9, pp. 145-151</ref>
[[Biofouling]] is one of the most important problems in aquaculture.<ref>Design Guide: Copper Alloy Mesh in Marine Aquaculture, International Copper Research Association Inc. (INCRA), 1984</ref> Biofouling occurs on non-copper materials in the marine environment, including [[fish cage]] surfaces and [[fish net|nettings]].<ref name=Braithwaite/> For example, it was noted that the open area of a mesh immersed for only seven days in a [[Tasmanian]] aquaculture operation decreased by 37% as a result of biofouling.<ref>{{cite journal|doi=10.1080/08927019509378298}}</ref>


The biofouling process begins when [[algae]] [[spores]], marine [[invertebrate]] [[larvae]], and other organic material adhere to surfaces submerged in marine environments (e.g., fish nets in aquaculture). Bacteria then encourage the attachment of secondary unwanted colonizers.<ref name=Braithwaite></ref><ref>Bakus, G.N. et. al., (1986), Chemical ecology of marine organisms: An overview; J. Chem. Ecol., Vol. 5, pp. 951-987</ref>
The biofouling process begins when [[algae]] [[spores]], marine [[invertebrate]] [[larvae]], and other organic material adhere to surfaces submerged in marine environments (e.g., fish nets in aquaculture). Bacteria then encourage the attachment of secondary unwanted colonizers.<ref name=Braithwaite/><ref>{{cite journal|doi=10.1007/BF01638991}}</ref>


Biofouling has strong negative impacts on aquaculture operations. Water flow, oxygen, and [[nutrients]] are inhibited due to clogged nets in fish pens and cages.<ref>Eckman, J.E., et. al., (2001), Performance of cages as large animal-exclusion devices in the deep sea, Journal of Marine Research, Vol. 59, pp. 79-95</ref><ref>Ahlgren, M.O., (1998), Consumption and assimilation of salmon net pen fouling debris by the red sea cucumber Parastichopus califormicus: Implications for poly-culture, Journal of the World Aquaculture Society, Vol. 29, pp. 133-139</ref> The end result is often diseased fish from infections, such as netpen liver disease,<ref>Andersen, R.J., et. al., (1993), Chemical and biological evidence links microcystins to salmon netpen liver disease, Toxicon, Vol. 31, pp. 1315-1323</ref> [[amoebic gill disease]],<ref>Tan, C.K.F. et. al., (2002), Biofouling as a reservoir of Neoparamoeba pemaquidensis, the causative agent of amoebic gill disease in Atlantic salmon, Aquaculture, Vol. 210, pp. 49-58.</ref> parasites,<ref>Gonzalez, L. (1998), The life cycle of Hysterothylacium aduncum (Nematoda: Anisakidae) in Chilean marine farms, Aquaculture, Vol. 162, pp. 173-186</ref><ref>Huse, I. et. al., (1990), The effect of shading in pen rearing of Atlantic salmon, Aquacultural Engineering, Vol. 9, pp. 235-244</ref> and, in the case of shellfish, poisoning by phytoplankton.<ref>Ross, K.A. et. al., (2002), Fouling in scallop cultivation: Help or hinderance? Journal of Shellfish Research, Vol. 21, pp. 539-547</ref> Other negative impacts include increased fish deaths, decreased fish growth rates, premature fish harvesting, reduced fish product values and profitability, and an adversely impacted environment near fish farms.<ref>Collective Research on Aquaculture Biofouling, http://crabproject.com </ref><ref name=Braithwaite></ref><ref>Folke, C. et al., (1997) Salmon farming in context: Response to Black et al., Journal of Environmental Management, Volume 50, pp. 95-103</ref>
Biofouling has strong negative impacts on aquaculture operations. Water flow, oxygen, and [[nutrients]] are inhibited due to clogged nets in fish pens and cages.<ref>{{cite journal|author=Eckman, J.E., et. al.|year=2001|url=http://www.ingentaconnect.com/content/jmr/jmr/2001/00000059/00000001/art00004 |title=Performance of cages as large animal-exclusion devices in the deep sea|journal=Journal of Marine Research|volume=59|pages=79-95}}</ref><ref>Ahlgren, M.O., (1998), Consumption and assimilation of salmon net pen fouling debris by the red sea cucumber Parastichopus califormicus: Implications for poly-culture, Journal of the World Aquaculture Society, Vol. 29, pp. 133-139</ref> The end result is often diseased fish from infections, such as netpen liver disease,<ref>{{cite journal|pmid=8303725}}</ref> [[amoebic gill disease]],<ref name=tan>{{cite journal|doi=10.1016/S0044-8486(01)00858-4}}</ref> parasites,<ref>{{cite journal|doi=10.1016/S0044-8486(97)00303-7}}</ref><ref>{{cite journal|doi=10.1016/0144-8609(90)90018-U}}</ref> and, in the case of shellfish, poisoning by phytoplankton.<ref>Ross, K.A. et. al., (2002), Fouling in scallop cultivation: Help or hinderance? Journal of Shellfish Research, Vol. 21, pp. 539-547</ref> Other negative impacts include increased fish deaths, decreased fish growth rates, premature fish harvesting, reduced fish product values and profitability, and an adversely impacted environment near fish farms.<ref name=crab/><ref name=Braithwaite/><ref>{{cite journal|author=Folke, C. ''et al.''|year=1997|title=Salmon farming in context: Response to Black et al.|journal=Journal of Environmental Management|url=http://cat.inist.fr/?aModele=afficheN&cpsidt=2711572|volume=50|pages=95-103}}</ref>


Biofouling adds enormous weight to submerged fish netting. Two hundred fold increases in weight have been reported.<ref>Milne, P.H., (1970), Fish Farming: A guide to the design and construction of net enclosures, Marine Research, Vol. 1, pp. 1-31</ref><ref>Beveridge, M., (1996), Cage Aquaculture, The University Press, Cambridge)</ref> This translates, for example, to two thousand pounds of unwanted organisms adhered to what was once a clean 10-pound fish net. In [[South Australia]], biofouling weighing 6.5 [[tonnes]] (approximately 13,000 pounds) was observed on a fish net.<ref>Cronin, E.R, Cheshire, A.C., Clarke, S.M. and Melville, A.J. (1999), An investigation into the composition, [[biomass]], and oxygen budget of the fouling community on a tuna aquaculture farm, Biofouling, Vol. 13, pp. 279-299</ref> This extra burden often results in net breakage and additional maintenance costs.
Biofouling adds enormous weight to submerged fish netting. Two hundred fold increases in weight have been reported.<ref>Milne, P.H., (1970), Fish Farming: A guide to the design and construction of net enclosures, Marine Research, Vol. 1, pp. 1-31 ISBN 0114904634</ref><ref name=Beveridge/> This translates, for example, to two thousand pounds of unwanted organisms adhered to what was once a clean 10-pound fish net. In [[South Australia]], biofouling weighing 6.5 [[tonnes]] (approximately 13,000 pounds) was observed on a fish net.<ref>{{cite journal|doi=10.1080/08927019909378386 }}</ref> This extra burden often results in net breakage and additional maintenance costs.


To combat [[parasites]] from biofouling, [[pesticides]] such as [[cypermethrin]], azamethiphos, and [[emamectin benzoate]] may be administered, but these have been found to have detrimental environmental effects, for example, in [[lobster]] operations.<ref>Burridge, L.E. et al., (1999), The lethality of Salmosan® (azamethiphos) to American lobster (Homarus americanus) larvae, postlarvae, and adults, Ecotoxicology and Environmental Safety, Vol. 43, pp. 165-169</ref><ref>Burridge, L.E. et al., (2000a), The lethality of the cypermethrin formulation Excis® to larval and post-larval stages of the American lobster (Homarus americanus), Aquaculture, Vol. 182, pp. 37-47</ref><ref>Burridge, L.E. et al., (2000b), The lethality of anti-sea lice formulations Salmosan® (azamethiphos) and Excis® (cypermethrin) to stage IV and adult lobsters (Homarus americanus) during repeated short-term exposures, Aquaculture, Vol. 182, pp. 27-35</ref><ref>Ernst, W. et al. (2001) Dispersion and toxicity of non-target aquatic organisms of pesticides used to treat sea lice on salmon in net pen enclosures, Marine Pollution Bulletin, Vol. 42, pp. 433-444</ref><ref>Waddy, S.L. et al. (2002), Emamectin benzoate induces molting in American lobster Homarus americanus, Canadian Journal of Fisheries and Aquatic Sciences, Vol. 59, pp. 1096-1099</ref>
To combat [[parasites]] from biofouling, [[pesticides]] such as [[cypermethrin]], azamethiphos, and [[emamectin benzoate]] may be administered, but these have been found to have detrimental environmental effects, for example, in [[lobster]] operations.<ref>{{cite journal|doi=10.1006/eesa.1999.1771}}</ref><ref>{{cite journal|doi=10.1016/S0044-8486(99)00252-5}}</ref><ref>{{cite journal|doi=10.1016/S0044-8486(99)00251-3}}</ref><ref>{{cite journal|doi=10.1016/S0025-326X(00)00177-6}}</ref><ref>{{cite journal|doi=10.1139/F02-106|author=Waddy, S.L. et al.|year=2002|title=Emamectin benzoate induces molting in American lobster Homarus americanus|journal=Canadian Journal of Fisheries and Aquatic Sciences|pages=1096-1099|url=http://pubs.nrc-cnrc.gc.ca/rp/rppdf/f02-106.pdf}}</ref>


To treat diseases in fish raised in biofouled nets, fish stocks are administered [[antibiotics]]. The antibiotics can have unwanted long-term health effects on consumers and on coastal environments near aquaculture operations.<ref>The next seafood frontier: The ocean, April 28, 2009, references article in Nature; http://money.cnn.com/2009/04/27/smallbusiness/farming_the_open_oceans.fsb</ref>
To treat diseases in fish raised in biofouled nets, fish stocks are administered [[antibiotics]]. The antibiotics can have unwanted long-term health effects on consumers and on coastal environments near aquaculture operations.<ref>[http://money.cnn.com/2009/04/27/smallbusiness/farming_the_open_oceans.fsb The next seafood frontier: The ocean], April 28, 2009, references article by Myers in Nature; </ref>
To combat biofouling, operators often implement costly maintenance measures, such as frequent net changing, cleaning/removal of unwanted organisms from nets, net repairs, and chemical treatment including antimicrobial coatings on nylon nets.<ref>Hodson, S.L., Lewis, T.E., Burke, C.M (1997) Biofouling on fish-cage netting: Efficacy and problems of in situ cleaning, Aquaculture, Vol. 152, pp. 77-90</ref><ref>Tan, C.K.F., Nowak, B.F., and Hodson, S.L. (2002), Biofouling as a reservoir of Neoparamoeba pemaquidensis, the causative agent of amoebic gill disease in Atlantic salmon, Aquaculture, Vol. 210, pp. 49-58</ref><ref>Li, S. (1994), Fish culture in cages and pens: Freshwater Fish Culture in China: Principles and Practice, pp. 305-346, Elsevier, Amsterdam</ref><ref>Beveridge, M. (1996), Cage Aquaculture, The University Press, Cambridge</ref> The cost of antifouling a single salmon net can be several thousand [[British pounds]].<ref name=Braithwaite></ref> In some sectors of the European aquaculture industry, cleaning biofouled fish and shellfish cages can cost 5-20% of its market value. Heavy fouling can reduce the saleable product in nets by 60-90%.<ref>Collective research on Aquaculture Biofouling, http://crabproject.com</ref>
To combat biofouling, operators often implement costly maintenance measures, such as frequent net changing, cleaning/removal of unwanted organisms from nets, net repairs, and chemical treatment including antimicrobial coatings on nylon nets.<ref>{{cite journal|doi=10.1016/S0044-8486(97)00007-0}}</ref><ref name=tan/><ref>Li, S. (1994), Fish culture in cages and pens: Freshwater Fish Culture in China: Principles and Practice, pp. 305-346, Elsevier, Amsterdam ISBN 0444888829</ref><ref>Beveridge, M. (1996), Cage Aquaculture, The University Press, Cambridge</ref> The cost of antifouling a single salmon net can be several thousand [[British pounds]].<ref name=Braithwaite/> In some sectors of the European aquaculture industry, cleaning biofouled fish and shellfish cages can cost 5-20% of its market value. Heavy fouling can reduce the saleable product in nets by 60-90%.<ref name=crab>[http://crabproject.com Collective research on Aquaculture Biofouling]</ref>


Antifouling paints are often used on nylon nets because the process is more economical than manual cleaning.<ref>Short, J.W. and Thrower, F.P., (1987), Toxicity of tri-n-butylin to Chinook salmon, Oncorhynchus tshawytscha, adapted to seawater, Aquaculture, Vol. 61, pp. 193-200</ref> When nylon nets are coated with antifouling paints, the coatings repel biofouling for a period of time, usually between several weeks to several months. However, the nets eventually succumb to biofouling. Antifouling paints containing [[cuprous oxide]] [[algaecide]]/[[biocide]] are the paint technology used almost exclusively in the fish farming industry today.<ref name=Braithwaite></ref> The treatments usually flake off within a few weeks to six to eight months.<ref name=Braithwaite></ref><ref>Alberto, Jose and Disselkoen, Ochoa (2009), Floating device to clean nets, Patent application 12/455,150, Publication US 2010/0006036 A1, Filing date May 27, http://www.google.com/patents/about?id=AnXLAAAAEBAJ&dq=FLOATING+DEVICE+TO+CLEAN+NETS; and National Chilean Patent Application No. 1565-2008 filed on May 29, 2008</ref>
Antifouling paints are often used on nylon nets because the process is more economical than manual cleaning.<ref>{{cite journal|doi=10.1016/0044-8486(87)90148-7}}</ref> When nylon nets are coated with antifouling paints, the coatings repel biofouling for a period of time, usually between several weeks to several months. However, the nets eventually succumb to biofouling. Antifouling paints containing [[cuprous oxide]] [[algaecide]]/[[biocide]] are the paint technology used almost exclusively in the fish farming industry today. The treatments usually flake off within a few weeks to six to eight months.<ref name=Braithwaite/><ref name=nets>Alberto, Jose and Disselkoen, Ochoa (2009), [http://www.google.com/patents/about?id=AnXLAAAAEBAJ&dq=FLOATING+DEVICE+TO+CLEAN+NETS Floating device to clean nets], Patent application 12/455,150, Publication US 2010/0006036 A1, Filing date May 27; and National Chilean Patent Application No. 1565-2008 filed on May 29, 2008</ref>


Biofouled nets are replaced weekly or after several months of service, depending on environmental conditions, in a complicated, costly, and labor-intensive operation that involves divers and specialized personnel. During this process, live fish in nets must be transferred to clean cages, which causes undue stress and [[asphyxiation]] that results in some loss of fish.<ref>Paclibare et al., (1994), Clearing of the kidney-disease bacterium Renibacterium salmoninarum from seawater by the blue mussel Mytilus edulis, and the status of the mussel as a reservoir of the bacterium, Diseases of Aquatic Organisms, Vol. 18, pp. 129-133</ref> Biofouled nets that can be reused are washed on land via manual brushing and scrubbing or high-pressure water hosing. They are then dried and re-impregnated with antifouling liquids.<ref>Enright, C., (1993), Control of fouling in bivalve aquaculture, World Aquaculture¸Vol. 24, pp. 44-46</ref><ref>Beveridge, M. (1996), Cage Aquaculture. The University Press, Cambridge</ref><ref>Lee et al., (1985), Observations on the use of antifouling paint in netcage fish farming in Singapore, Singapore Journal of Primary Industries, Vol. 13, pp. 1-12</ref><ref>Alberto, J. and Disselkoen, O. (2009), Floating device to clean nets, Patent application 12/455,150, Publication US 2010/0006036 A1, Filing date May 27, http://www.google.com/patents/about?id=AnXLAAAAEBAJ&dq=FLOATING+DEVICE+TO+CLEAN+NETS; and Alberto, J. and Disselkoen, O. (2008), National Chilean Patent Application No. 1565-2008 filed on May 29)</ref> A line of net cleaners is available for in-situ washings where permitted.<ref>http://www.akvagroup.com/doc//productsheets_english/04%20akvasmart/EN-Akvamart-Idema-Net-Cleaning-Systems-281118.pdf</ref>
Biofouled nets are replaced weekly or after several months of service, depending on environmental conditions, in a complicated, costly, and labor-intensive operation that involves divers and specialized personnel. During this process, live fish in nets must be transferred to clean cages, which causes undue stress and [[asphyxiation]] that results in some loss of fish.<ref>Paclibare et al., (1994), Clearing of the kidney-disease bacterium Renibacterium salmoninarum from seawater by the blue mussel Mytilus edulis, and the status of the mussel as a reservoir of the bacterium, Diseases of Aquatic Organisms, Vol. 18, pp. 129–133</ref> Biofouled nets that can be reused are washed on land via manual brushing and scrubbing or high-pressure water hosing. They are then dried and re-impregnated with antifouling liquids.<ref>Enright, C., (1993), Control of fouling in bivalve aquaculture, World Aquaculture, Vol. 24, pp. 44–46</ref><ref name=Beveridge>Beveridge, M. (2004), Cage Aquaculture. The University Press, Cambridge ISBN 1405108428</ref><ref>Lee et al., (1985), Observations on the use of antifouling paint in netcage fish farming in Singapore, Singapore Journal of Primary Industries, Vol. 13, pp. 1-12</ref><ref name=nets/> A line of net cleaners is available for in-situ washings where permitted.<ref>[http://www.akvagroup.com/doc//productsheets_english/04%20akvasmart/EN-Akvamart-Idema-Net-Cleaning-Systems-281118.pdf Idema Net Cleaning Systems]</ref>


Should the lack of oxygen in submerged cages create an emergency condition that endangers the health of fish, divers may be deployed with special in situ cleaning machinery to scrub biofouled nets. This measure, which is forbidden by environmental, fisheries, maritime, and sanitary authorities, is nevertheless implemented under extraordinary circumstances. <ref>Alberto, J. and Disselkoen, O. (2009), Floating device to clean nets, Patent application 12/455,150, Publication US 2010/0006036 A1, Filing date May 27, http://www.google.com/patents/about?id=AnXLAAAAEBAJ&dq=FLOATING+DEVICE+TO+CLEAN+NETS; and Alberto, J. and Disselkoen, O. (2008), National Chilean Patent Application No. 1565-2008 filed on May 29</ref>
Should the lack of oxygen in submerged cages create an emergency condition that endangers the health of fish, divers may be deployed with special in situ cleaning machinery to scrub biofouled nets. This measure, which is forbidden by environmental, fisheries, maritime, and sanitary authorities, is nevertheless implemented under extraordinary circumstances.<ref name=nets/>


The aquaculture industry is addressing the negative environmental impacts from its operations (see Aquaculture issues: [[http://en.wikipedia.org/wiki/Aquaculture#Issues]]). As the industry evolves, a cleaner, more [[sustainable]] aquaculture industry is expected to emerge, one that may increasingly rely on materials with anti-fouling, anti-corrosive, and strong structural properties, such as copper alloys.
The aquaculture industry is addressing the negative environmental impacts from its operations (see [[Aquaculture#Issues|aquaculture issues]]). As the industry evolves, a cleaner, more [[sustainable]] aquaculture industry is expected to emerge, one that may increasingly rely on materials with anti-fouling, anti-corrosive, and strong structural properties, such as copper alloys.


== Antifouling properties of copper alloys in the marine environment ==
== Antifouling properties of copper alloys in the marine environment ==
Also see: [[Antimicrobial properties of copper]] and [[Antimicrobial copper alloy touch surfaces]]
{{seealso|Antimicrobial properties of copper|Antimicrobial copper alloy touch surfaces}}
<br /><br />


In the aquaculture industry, sound [[animal husbandry]] translates to keeping fish clean, well fed, healthy, and not overcrowded.<ref>Offshore Aquaculture in the United States: Economic Considerations, Implications, & Opportunities, U.S. Department of Commerce, National Oceanic & Atmospheric Administration, July 2008</ref> One solution to keeping farmed fish healthy is to contain them in antifouling copper alloy nets and structures.<ref>http://www.copper.org/Applications/cuni/txt_references.html#aquaculture</ref>
In the aquaculture industry, sound [[animal husbandry]] translates to keeping fish clean, well fed, healthy, and not overcrowded.<ref>Offshore Aquaculture in the United States: Economic Considerations, Implications, & Opportunities, U.S. Department of Commerce, National Oceanic & Atmospheric Administration, July 2008</ref> One solution to keeping farmed fish healthy is to contain them in antifouling copper alloy nets and structures.<ref>{{cite web|url=http://www.copper.org/Applications/cuni/txt_references.html#aquaculture |title=Copper Nickel : References |publisher=Copper.org |date= |accessdate=2010-06-16}}</ref>


Researchers have attributed copper’s resistance to biofoul, even in temperate waters, to two possible mechanisms: 1) a retarding sequence of colonization through release of antimicrobial copper ions, thereby preventing the attachment of microbial layers to marine surfaces;<ref>Sutherland, I.W., 1983, Microbial exopolysaccarides: Their role in microbial adhesion in aqueous systems, Critical Reviews in Microbiology, Vol. 10, pp.173-201</ref> and, 2) separating layers that contain corrosive products and the spores of juveniles or macro-encrusting organisms.<ref>Edding, Mario E., Flores, Hector, and Miranda, Claudio, (1995), Experimental Usage of Copper-Nickel Alloy Mesh in Mariculture. Part 1: Feasibility of usage in a temperate zone; Part 2: Demonstration of usage in a cold zone; Final report to the International Copper Association Ltd.</ref>
Researchers have attributed copper’s resistance to biofoul, even in temperate waters, to two possible mechanisms: 1) a retarding sequence of colonization through release of antimicrobial copper ions, thereby preventing the attachment of microbial layers to marine surfaces;<ref>Sutherland, I.W., 1983, Microbial exopolysaccarides: Their role in microbial adhesion in aqueous systems, Critical Reviews in Microbiology, Vol. 10, pp.173-201</ref> and, 2) separating layers that contain corrosive products and the spores of juveniles or macro-encrusting organisms.<ref name="autogenerated1995">Edding, Mario E., Flores, Hector, and Miranda, Claudio, (1995), Experimental Usage of Copper-Nickel Alloy Mesh in Mariculture. Part 1: Feasibility of usage in a temperate zone; Part 2: Demonstration of usage in a cold zone; Final report to the International Copper Association Ltd.</ref>


The most important requirement for optimum biofouling resistance is that the copper alloys should be freely exposed or electrically insulated from less noble alloys and from [[cathodic protection]]. [[Galvanic]] coupling to less noble alloys and [[cathodic]] protection prevent copper ion releases from surface films and therefore reduce biofouling resistance.<ref>Powell, Carol and Stillman, Hal (2009), Corrosion behavior of copper alloys used in marine aquaculture, http://www.copper.org/applications/cuni/pdf/marine_aquaculture.pdf</ref>
The most important requirement for optimum biofouling resistance is that the copper alloys should be freely exposed or electrically insulated from less noble alloys and from [[cathodic protection]]. [[Galvanic]] coupling to less noble alloys and [[cathodic]] protection prevent copper ion releases from surface films and therefore reduce biofouling resistance.<ref>Powell, Carol and Stillman, Hal (2009), [http://www.copper.org/applications/cuni/pdf/marine_aquaculture.pdf Corrosion behavior of copper alloys used in marine aquaculture]</ref>


As temperatures increase and water [[velocities]] decrease in marine waters, biofouling rates dramatically rise. However, copper’s resistance to biofouling is observed even in temperate waters. Studies in Herrdura Bay, Chile, where biofouling conditions are extreme, demonstrated that a copper alloy (90% copper, 10% nickel) avoided macro-encrusting organisms.<ref>Edding, Mario E., Flores, Hector, and Miranda, Claudio, (1995), Experimental Usage of Copper-Nickel Alloy Mesh in Mariculture. Part 1: Feasibility of usage in a temperate zone; Part 2: Demonstration of usage in a cold zone; Final report to the International Copper Association Ltd.</ref>
As temperatures increase and water [[velocities]] decrease in marine waters, biofouling rates dramatically rise. However, copper’s resistance to biofouling is observed even in temperate waters. Studies in Herrdura Bay, Chile, where biofouling conditions are extreme, demonstrated that a copper alloy (90% copper, 10% nickel) avoided macro-encrusting organisms.<ref name="autogenerated1995"/>


== Corrosion behavior of copper alloys used in marine aquaculture ==
== Corrosion behavior of copper alloys used in marine aquaculture ==
Copper alloys used in sea water service have low general [[corrosion]] rates but also have a
Copper alloys used in sea water service have low general [[corrosion]] rates but also have a
high resistance to many localized forms of corrosion. For a technical discussion regarding various types of corrosion, application considerations (e.g., depth of installations, effect of polluted waters, sea conditions), and the corrosion characteristics of several copper alloys used in aquaculture netting (i.e., copper-nickel, copper-zinc, and copper-silicon click here: http://www.copper.org/applications/cuni/pdf/marine_aquaculture.pdf
high resistance to many localized forms of corrosion. For a technical discussion regarding various types of corrosion, application considerations (e.g., depth of installations, effect of polluted waters, sea conditions), and the corrosion characteristics of several copper alloys used in aquaculture netting (i.e., copper-nickel, copper-zinc, and copper-silicon<ref>[http://www.copper.org/applications/cuni/pdf/marine_aquaculture.pdf Corrosion Behaviour of Copper Alloys used in Marine Aquaculture]</ref>).


== Environmental performance of copper alloy mesh in marine fish farming ==
== Environmental performance of copper alloy mesh in marine fish farming ==
Many complicated factors influence the environmental performance of copper alloys in aquaculture operations. A technical description of antibiofouling mechanisms, fish health and welfare, fish losses due to escapes and predator attacks, and reduced [[life cycle]] [[environmental impacts]] are summarized here: http://www.ecosea.cl/pdfs/Environmental_Performance_of_Copper_Alloys_in_Aquaculture_v5.pdf
Many complicated factors influence the environmental performance of copper alloys in aquaculture operations. A technical description of antibiofouling mechanisms, fish health and welfare, fish losses due to escapes and predator attacks, and reduced [[life cycle]] [[environmental impacts]] is summarized in this reference.<ref>[http://www.ecosea.cl/pdfs/Environmental_Performance_of_Copper_Alloys_in_Aquaculture_v5.pdf Environmental Performance of Copper Alloy Mesh in Marine Fish Farming: The Case for Using Solid Copper Alloy Mesh]</ref>


== Types of copper alloys used in aquaculture ==
== Types of copper alloys used in aquaculture ==
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Copper-zinc [[brass]] alloys are being deployed today in commercial-scale aquaculture operations in Asia and South America. Extensive research, including demonstrations and trials, are currently 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.
Copper-zinc [[brass]] alloys are being deployed today in commercial-scale aquaculture operations in Asia and South America. Extensive research, including demonstrations and trials, are currently 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.


The University of New Hampshire is in the midst of conducting experiments under the auspices of the International Copper Association (ICA)<ref>http://www.copperinfo.com </ref> to evaluate the structural, [[hydrodynamic]], and antifouling response of copper alloy nets. Factors to be determined from these experiments, such as drag, cage dynamic loads, material loss, and biological growth – well documented for nylon netting but not fully understood for copper-nickel alloy nets – will help to design fish cage enclosures made from these alloys. The East China Sea Fisheries Research Institute, in Shanghai, China, is also conducting experimental investigations on copper alloys for ICA.
The University of New Hampshire is in the midst of conducting experiments under the auspices of the International Copper Association (ICA)<ref>{{cite web|url=http://www.copperinfo.com |title=Welcome to CopperInfo - Your Worldwide Copper Information Source |publisher=Copperinfo.com |date= |accessdate=2010-06-16}}</ref> to evaluate the structural, [[hydrodynamic]], and antifouling response of copper alloy nets. Factors to be determined from these experiments, such as drag, cage dynamic loads, material loss, and biological growth – well documented for nylon netting but not fully understood for copper-nickel alloy nets – will help to design fish cage enclosures made from these alloys. The East China Sea Fisheries Research Institute, in Shanghai, China, is also conducting experimental investigations on copper alloys for ICA.


=== Copper-zinc alloys ===
=== Copper-zinc alloys ===
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The Mitsubishi-Shindoh Co., Ltd., has developed a proprietary copper-zinc brass alloy, UR30™, specifically designed 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 fabricated into chain link, woven, or other types of flexible mesh. Corrosion rates depend on the depth of submersion and seawater conditions. The average reported corrosion rate reported for the alloy is <5 μm/yr based on 2- and 5-year exposure trials in seawater.<ref name=ecosea>[http://www.ecosea.cl/ EcoSea Farming S.A.]</ref>


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The Ashimori Industry Company, Ltd.,<ref>{{cite web|url=http://www.ashimori.co.jp/english/index.html |title=Ashimori Industry Co.,Ltd |publisher=Ashimori.co.jp |date= |accessdate=2010-06-16}}</ref> has installed approximately 300 flexible cages with woven chain link UR30™ meshes in Japan to raise [[Seriola]] (i.e., [[yellowtail]], [[amberjack]], [[kingfish]], [[hamachi]]). The company has installed another twenty-eight UR30™ cages to raise [[Atlantic salmon]] at the Van Diemen Aquaculture operations in [[Tasmania]], Australia. In [[Chile]], EcoSea Farming S.A. expects to have installed a total of approximately forty woven chain link UR30™ mesh cages by the end of 2010 to raise [[trout]] and Atlantic salmon;<ref name=ecosea/> and in [[Panama]] and the USA, demonstrations and trials are underway using flexible cages with woven chain link UR30™.
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The Mitsubishi-Shindoh Co., Ltd., has developed a proprietary copper-zinc brass alloy, UR30™, specifically designed 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 fabricated into chain link, woven, or other types of flexible mesh. Corrosion rates depend on the depth of submersion and seawater conditions. The average reported corrosion rate reported for the alloy is <5μm/yr based on 2- and 5-year exposure trials in seawater.<ref>EcoSea Farming S.A., http://www.ecosea.cl</ref>

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The Ashimori Industry Company, Ltd.,<ref>http://www.ashimori.co.jp/english/index.html</ref> has installed approximately 300 flexible cages with woven chain link UR30™ meshes in Japan to raise [[Seriola]] (i.e., [[yellowtail]], [[amberjack]], [[kingfish]], [[hamachi]]). The company has installed another twenty-eight UR30™ cages to raise [[Atlantic salmon]] at the Van Diemen Aquaculture operations in [[Tasmania]], Australia. In [[Chile]], EcoSea Farming S.A. expects to have installed a total of approximately forty woven chain link UR30™ mesh cages by the end of 2010 to raise [[trout]] and Atlantic salmon.<ref>EcoSea Farming S.A., http://www.ecosea.cl</ref> And in [[Panama]] and the USA, demonstrations and trials are underway using flexible cages with woven chain link UR30™.


To date, in over 10 years of aquaculture experience, chain link mesh fabricated by UR30™ alloys have not suffered from [[dezincification]], [[stress corrosion cracking]], or [[erosion corrosion]].
To date, in over 10 years of aquaculture experience, chain link mesh fabricated by UR30™ alloys have not suffered from [[dezincification]], [[stress corrosion cracking]], or [[erosion corrosion]].


Additional information about UR30™ can be found at the following Websites: chemical composition of UR30™<ref>http://www.mitsubishi-shindoh.com/en/urchem.htm</ref>; physical properties of UR30™<ref>www.mitsubishi-shindoh.com/en/urphys.htm</ref>; diameters available for UR30™<ref>http://www.mitsubishi-shindoh.com/en/ursize.htm</ref>; corrosion resistance of UR30™<ref>http://www.mitsubishi-shindoh.com/en/urcorr.htm</ref>; and mechanical properties of UR30™<ref>http://www.mitsubishi-shindoh.com/en/urmech.htm</ref>.
Additional information about UR30™ can be found at the following Websites: chemical composition of UR30™<ref>{{cite web|author=Saburo Kito |url=http://www.mitsubishi-shindoh.com/en/urchem.htm |title=UR_Chemicals |publisher=Mitsubishi-shindoh.com |date= |accessdate=2010-06-16}}</ref>; physical properties of UR30™<ref>{{cite web|author=Saburo Kito |url=http://www.mitsubishi-shindoh.com/en/urphys.htm |title=UR_Physicals |publisher=Mitsubishi-shindoh.com |date= |accessdate=2010-06-16}}</ref>; diameters available for UR30™<ref>{{cite web|author=Saburo Kito |url=http://www.mitsubishi-shindoh.com/en/ursize.htm |title=UR_Sizes |publisher=Mitsubishi-shindoh.com |date= |accessdate=2010-06-16}}</ref>; corrosion resistance of UR30™<ref>{{cite web|author=Saburo Kito |url=http://www.mitsubishi-shindoh.com/en/urcorr.htm |title=UR_Corrosion |publisher=Mitsubishi-shindoh.com |date= |accessdate=2010-06-16}}</ref>; and mechanical properties of UR30™<ref>{{cite web|author=Saburo Kito |url=http://www.mitsubishi-shindoh.com/en/urmech.htm |title=UR_Mechanicals |publisher=Mitsubishi-shindoh.com |date= |accessdate=2010-06-16}}</ref>.


Alternative copper-zinc alloys for aquaculture are being developed by other companies but have not yet been deployed in commercial operations.
Alternative copper-zinc alloys for aquaculture are being developed by other companies but have not yet been deployed in commercial operations.
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Copper-nickel alloys were developed specifically for seawater applications over five decades ago. Today, these alloys are being investigated for their potential use in aquaculture.
Copper-nickel alloys were developed specifically for seawater applications over five decades ago. Today, these alloys are being investigated for their potential use in aquaculture.


Copper-nickel alloys for marine applications are usually comprised of 90% copper, 10% nickel, plus small amounts of manganese and iron to enhance corrosion resistance. The seawater corrosion resistance of copper-nickel alloys results in a thin, adherent, protective surface film which forms naturally and quickly on the metal upon exposure to clean seawater.<ref>http://www.copper.org/applications/cuni/txt_swater_corrosion_resistance.html#abstract</ref>
Copper-nickel alloys for marine applications are usually comprised of 90% copper, 10% nickel, plus small amounts of manganese and iron to enhance corrosion resistance. The seawater corrosion resistance of copper-nickel alloys results in a thin, adherent, protective surface film which forms naturally and quickly on the metal upon exposure to clean seawater.<ref>{{cite web|url=http://www.copper.org/applications/cuni/txt_swater_corrosion_resistance.html#abstract |title=Copper Nickels : Seawater Corrosion Resistance and Antifouling |publisher=Copper.org |date=2005-12-15 |accessdate=2010-06-16}}</ref>


The rate of corrosion protective formation is temperature dependent. 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, it could take 2-3 months for the protection to mature. But once a good surface film forms, corrosion rates decrease, normally to 0.02-0.002 mm/yr, as protective layers develop over a period of years.<ref>The Application of Copper-Nickel Alloys in Marine Systems, CDA Inc. Seminar-Technical Report 7044-1919, 1996 at http://csaweb115v.csa.com/ids70/results.php?id=1&SID=mi0erc43ibk0300etiqetiu7m5</ref> These alloys have good resistance to chloride [[pitting]] and [[crevice corrosion]] and are not susceptible to chloride stress corrosion.
The rate of corrosion protective formation is temperature dependent. 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, it could take 2-3 months for the protection to mature. But once a good surface film forms, corrosion rates decrease, normally to 0.02-0.002 mm/yr, as protective layers develop over a period of years.<ref>[http://csaweb115v.csa.com/ids70/results.php?id=1&SID=mi0erc43ibk0300etiqetiu7m5 The Application of Copper-Nickel Alloys in Marine Systems], CDA Inc. Seminar-Technical Report 7044-1919, 1996</ref> These alloys have good resistance to chloride [[pitting]] and [[crevice corrosion]] and are not susceptible to chloride stress corrosion.

A wealth of additional information about corrosion performance, mechanical properties,
fabrication, and biofouling properties of copper-nickel alloys can be found at: http://www.copper.org/Applications/cuni/txt_references.html#aquaculture and http://www.coppernickel.org.


=== Copper-silicon alloys ===
=== Copper-silicon alloys ===
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As with the copper-nickel alloys, corrosion resistance of copper-silicon is due to protective films that form on the surface over a period of time. General corrosion rates of 0.025-0.050mm have been observed in quiet waters. This rate decreases towards the lower end of the range over long-term exposures (e.g., 400-600 days). There is generally no pitting with the silicon-bronzes and, if pitting does occur, the pits are small. Also there is good resistance to erosion corrosion up to moderate flow rates. Because copper-silicon is weldable, rigid cages can be constructed with this material. Also, because welded copper-silicon mesh is lighter than copper-zinc chain link, aquaculture enclosures made with copper-silicon may be lighter in weight and therefore a potentially less expensive alternative.
As with the copper-nickel alloys, corrosion resistance of copper-silicon is due to protective films that form on the surface over a period of time. General corrosion rates of 0.025-0.050mm have been observed in quiet waters. This rate decreases towards the lower end of the range over long-term exposures (e.g., 400-600 days). There is generally no pitting with the silicon-bronzes and, if pitting does occur, the pits are small. Also there is good resistance to erosion corrosion up to moderate flow rates. Because copper-silicon is weldable, rigid cages can be constructed with this material. Also, because welded copper-silicon mesh is lighter than copper-zinc chain link, aquaculture enclosures made with copper-silicon may be lighter in weight and therefore a potentially less expensive alternative.


Luvata Appleton, LLC, is researching and developing a line of copper-silicon alloy woven meshes and welded meshes under the patent-pending trade name Seawire.™<ref>www.luvata.com; Seawire™ is a trademark of Luvata Appleton, LLC. The company intends to market a wide range of alloys in addition to copper-silicon under this trademark</ref>. Copper-silicon alloy meshes have been developed by the firm to raise various marine organisms in test trials that are now in various stages of evaluation. These include raising cobia in Panama, lobsters in Maine, and crabs in the Chesapeake Bay. The company is working with various 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. Results will be provided when the studies are concluded.
Luvata Appleton, LLC, is researching and developing a line of copper-silicon alloy woven meshes and welded meshes under the patent-pending trade name Seawire.™<ref>www.luvata.com; Seawire™ is a trademark of Luvata Appleton, LLC. The company intends to market a wide range of alloys in addition to copper-silicon under this trademark</ref>. Copper-silicon alloy meshes have been developed by the firm to raise various marine organisms in test trials that are now in various stages of evaluation. These include raising cobia in Panama, lobsters in Maine, and crabs in the Chesapeake Bay. The company is working with various 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. Results will be provided when the studies are concluded.

⚫
== References ==
⚫
{{reflist|colwidth=30em}}


== Further reading ==
== Further reading ==
Design Guide: Copper Alloy Mesh in Marine Aquaculture, 1984, International Copper
*Design Guide: Copper Alloy Mesh in Marine Aquaculture, 1984, International Copper Research Association (INCRA) 704/5.
⚫
*Metal Corrosion in Boats, Nigel Warren and Adlard Coles, Nautical, 1998.
Research Association (INCRA) 704/5.
⚫
*Galvanic Corrosion: A Practical Guide for Engineers, R. Francis, 2001, NACE Press.
⚫
*Marine Corrosion Causes and Prevention, F. LaQue, John Wiley and Sons, 1975.
⚫
*The Selection of Materials for Seawater cooling Systems: A Practical Guide for Engineers, R. Francis, 2006, NACE Press.
⚫
*Guidelines for the Use of Copper Alloys in Seawater, A. Tuthill. 1987. CDA/ Nickel Institute Publication.
⚫
*The Brasses: Properties and Applications, CDA UK Publication 117.
⚫
*Copper in the Ocean Environment, Neal Blossom, American Chemet Corporation.
⚫
*ICA Project 438: Experimental usage of copper nickel alloy mesh in aquaculture, Mario E. Edding, Hector Flores, Claudio Miranda, Universidad Catholica del Norte, July 1995


==External links==
⚫
Metal Corrosion in Boats, Nigel Warren and Adlard Coles, Nautical, 1998.
⚫
*M.S. Parvizi, A. Aladjem and J. E. Castle. [http://csaweb115v.csa.com/ids70/results.php?id=1&SID=9unjh9jj1i0je26b9h59uulgd1 "Behaviour of 90-10 Cupronickel in Sea Water,"] International Material Reviews 1988, Vol. 33, No. 4., ISSN 0950-6608,

⚫
*Efird and Anderson. [http://csaweb116v.csa.com/ids70/results.php?id=1&SID=mankk19p5d04in7b57tnk4cic4 "Sea Water Corrosion of 90-10 and 70-30 Cu-Ni C 14 Year Exposures."] Materials Performance, November 1975, ISSN 0094-1492,
⚫
Galvanic Corrosion: A Practical Guide for Engineers, R. Francis, 2001, NACE Press.
*[http://www.coppernickel.org Information on Cu-Ni alloys]

*[http://www.mitsubishi-shindoh.com/en/urphys.htm Information on UR 30<sup>TM</sup>]
⚫
Marine Corrosion Causes and Prevention, F. LaQue, John Wiley and Sons, 1975.
* [http://www.copper.org/Applications/cuni/txt_references.html#aquaculture Corrosion in aquaculture]

⚫
The Selection of Materials for Seawater cooling Systems: A Practical Guide for
Engineers, R. Francis, 2006, NACE Press.

⚫
Guidelines for the Use of Copper Alloys in Seawater, A.Tuthill. 1987. CDA/ Nickel
Institute Publication.

⚫
The Brasses: Properties and Applications, CDA UK Publication 117.

⚫
Copper in the Ocean Environment, Neal Blossom, American Chemet Corporation.

⚫
ICA Project 438: Experimental usage of copper nickel alloy mesh in aquaculture, Mario E. Edding, Hector Flores, Claudio Miranda, Universidad Catholica del Norte, July 1995

⚫
M.S. Parvizi, A. Aladjem and J. E. Castle. "Behaviour of 90-10 Cupronickel in Sea Water," International Material Reviews 1988, Vol. 33, No. 4., ISSN 0950-6608, http://csaweb115v.csa.com/ids70/results.php?id=1&SID=9unjh9jj1i0je26b9h59uulgd1

⚫
Efird and Anderson. "Sea Water Corrosion of 90-10 and 70-30 Cu-Ni C 14 Year Exposures." Materials Performance, November 1975, ISSN 0094-1492, http://csaweb116v.csa.com/ids70/results.php?id=1&SID=mankk19p5d04in7b57tnk4cic4

For information on Cu-Ni alloys, go to: http://www.coppernickel.org.

For information on UR 30<sup>TM</sup>, go to: http://www.mitsubishi-shindoh.com/en/urphys.htm

⚫
== References ==
⚫
{{reflist}}


[[Category:Copper]]
[[Category:Copper]]
[[Category:Aquaculture]]
[[Category:Aquaculture]]
[[Category:Aquaculture engineering]]
[[Category:Aquaculture engineering]]
[[Category:Fish farming]]
[[Category:Fish farming]]

Revision as of 00:14, 17 June 2010

Recently, copper alloys have become important netting materials in the aquaculture (the farming of aquatic organisms including fish farming) industry. Various other materials, such as nylon, polyester, polypropylene, polyethylene, plastic-coated welded wire, rubber, patented rope products (Spectra®, Thorn-D®, Dyneema®), and galvanized steel are also used for netting in aquaculture fish enclosures around the world.[1][2][3][4][5] All of these materials are selected for a variety of reasons, including design feasibility, material strength, cost, and corrosion resistance.

What sets copper alloys apart from the other materials is that copper alloys are antimicrobial, that is, they destroy bacteria, viruses, fungi, algae, and other microbes. (For information about the antimicrobial properties of copper and its alloys, see Antimicrobial properties of copper and Antimicrobial copper alloy touch surfaces).

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, tubeworms, barnacles, mollusks, and other organisms on man-made marine structures.[6] By inhibiting microbial growth, copper alloy aquaculture cages avoid the need for costly net changes that are necessary with other materials. The resistance of organism growth on copper alloy nets also provides a cleaner and healthier environment for farmed fish to grow and thrive.

In addition to their antifouling benefits, copper alloys have strong structural and corrosion-resistant properties in marine environments.

It is the combination of all of these properties – antifouling, high strength, and corrosion resistance – that has made copper alloys a desirable material for such marine applications as condenser tubing, water intake screens, ship hulls, offshore structure, and sheathing. In the past 25 years or so, the benefits of copper alloys have caught the attention of the marine aquaculture industry. The industry is now actively deploying copper alloy netting and structural materials in commercial large-scale fish farming operations around the world.


Importance of aquaculture in feeding people around the world

See also: Aquaculture and Fish farming

Much has been written about the degradation and depletion of natural fish stocks in rivers, estuaries, and the oceans (see also overfishing).[7][8] Because industrial fishing has become extremely efficient, ocean stocks of large fish, such as tuna, cod, and halibut have declined by 90% in the past 50 years.[9][10][11]

Aquaculture, an industry that has emerged only in recent decades, has become one of the fastest growing sectors of the world food economy.[2] Aquaculture already supplies more than half of the world’s demand for fish.[12] This percentage is predicted to increase dramatically over the next few decades.

The problem of biofouling in aquaculture

Biofouling is one of the most important problems in aquaculture.[13] Biofouling occurs on non-copper materials in the marine environment, including fish cage surfaces and nettings.[2] For example, it was noted that the open area of a mesh immersed for only seven days in a Tasmanian aquaculture operation decreased by 37% as a result of biofouling.[14]

The biofouling process begins when algae spores, marine invertebrate larvae, and other organic material adhere to surfaces submerged in marine environments (e.g., fish nets in aquaculture). Bacteria then encourage the attachment of secondary unwanted colonizers.[2][15]

Biofouling has strong negative impacts on aquaculture operations. Water flow, oxygen, and nutrients are inhibited due to clogged nets in fish pens and cages.[16][17] The end result is often diseased fish from infections, such as netpen liver disease,[18] amoebic gill disease,[19] parasites,[20][21] and, in the case of shellfish, poisoning by phytoplankton.[22] Other negative impacts include increased fish deaths, decreased fish growth rates, premature fish harvesting, reduced fish product values and profitability, and an adversely impacted environment near fish farms.[23][2][24]

Biofouling adds enormous weight to submerged fish netting. Two hundred fold increases in weight have been reported.[25][26] This translates, for example, to two thousand pounds of unwanted organisms adhered to what was once a clean 10-pound fish net. In South Australia, biofouling weighing 6.5 tonnes (approximately 13,000 pounds) was observed on a fish net.[27] This extra burden often results in net breakage and additional maintenance costs.

To combat parasites from biofouling, pesticides such as cypermethrin, azamethiphos, and emamectin benzoate may be administered, but these have been found to have detrimental environmental effects, for example, in lobster operations.[28][29][30][31][32]

To treat diseases in fish raised in biofouled nets, fish stocks are administered antibiotics. The antibiotics can have unwanted long-term health effects on consumers and on coastal environments near aquaculture operations.[33] To combat biofouling, operators often implement costly maintenance measures, such as frequent net changing, cleaning/removal of unwanted organisms from nets, net repairs, and chemical treatment including antimicrobial coatings on nylon nets.[34][19][35][36] The cost of antifouling a single salmon net can be several thousand British pounds.[2] In some sectors of the European aquaculture industry, cleaning biofouled fish and shellfish cages can cost 5-20% of its market value. Heavy fouling can reduce the saleable product in nets by 60-90%.[23]

Antifouling paints are often used on nylon nets because the process is more economical than manual cleaning.[37] When nylon nets are coated with antifouling paints, the coatings repel biofouling for a period of time, usually between several weeks to several months. However, the nets eventually succumb to biofouling. Antifouling paints containing cuprous oxide algaecide/biocide are the paint technology used almost exclusively in the fish farming industry today. The treatments usually flake off within a few weeks to six to eight months.[2][38]

Biofouled nets are replaced weekly or after several months of service, depending on environmental conditions, in a complicated, costly, and labor-intensive operation that involves divers and specialized personnel. During this process, live fish in nets must be transferred to clean cages, which causes undue stress and asphyxiation that results in some loss of fish.[39] Biofouled nets that can be reused are washed on land via manual brushing and scrubbing or high-pressure water hosing. They are then dried and re-impregnated with antifouling liquids.[40][26][41][38] A line of net cleaners is available for in-situ washings where permitted.[42]

Should the lack of oxygen in submerged cages create an emergency condition that endangers the health of fish, divers may be deployed with special in situ cleaning machinery to scrub biofouled nets. This measure, which is forbidden by environmental, fisheries, maritime, and sanitary authorities, is nevertheless implemented under extraordinary circumstances.[38]

The aquaculture industry is addressing the negative environmental impacts from its operations (see aquaculture issues). As the industry evolves, a cleaner, more sustainable aquaculture industry is expected to emerge, one that may increasingly rely on materials with anti-fouling, anti-corrosive, and strong structural properties, such as copper alloys.

Antifouling properties of copper alloys in the marine environment

See also: Antimicrobial properties of copper and Antimicrobial copper alloy touch surfaces

In the aquaculture industry, sound animal husbandry translates to keeping fish clean, well fed, healthy, and not overcrowded.[43] One solution to keeping farmed fish healthy is to contain them in antifouling copper alloy nets and structures.[44]

Researchers have attributed copper’s resistance to biofoul, even in temperate waters, to two possible mechanisms: 1) a retarding sequence of colonization through release of antimicrobial copper ions, thereby preventing the attachment of microbial layers to marine surfaces;[45] and, 2) separating layers that contain corrosive products and the spores of juveniles or macro-encrusting organisms.[46]

The most important requirement for optimum biofouling resistance is that the copper alloys should be freely exposed or electrically insulated from less noble alloys and from cathodic protection. Galvanic coupling to less noble alloys and cathodic protection prevent copper ion releases from surface films and therefore reduce biofouling resistance.[47]

As temperatures increase and water velocities decrease in marine waters, biofouling rates dramatically rise. However, copper’s resistance to biofouling is observed even in temperate waters. Studies in Herrdura Bay, Chile, where biofouling conditions are extreme, demonstrated that a copper alloy (90% copper, 10% nickel) avoided macro-encrusting organisms.[46]

Corrosion behavior of copper alloys used in marine aquaculture

Copper alloys used in sea water service have low general corrosion rates but also have a high resistance to many localized forms of corrosion. For a technical discussion regarding various types of corrosion, application considerations (e.g., depth of installations, effect of polluted waters, sea conditions), and the corrosion characteristics of several copper alloys used in aquaculture netting (i.e., copper-nickel, copper-zinc, and copper-silicon[48]).

Environmental performance of copper alloy mesh in marine fish farming

Many complicated factors influence the environmental performance of copper alloys in aquaculture operations. A technical description of antibiofouling mechanisms, fish health and welfare, fish losses due to escapes and predator attacks, and reduced life cycle environmental impacts is summarized in this reference.[49]

Types of copper alloys used in aquaculture

Copper-zinc brass alloys are being deployed today in commercial-scale aquaculture operations in Asia and South America. Extensive research, including demonstrations and trials, are currently 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.

The University of New Hampshire is in the midst of conducting experiments under the auspices of the International Copper Association (ICA)[50] to evaluate the structural, hydrodynamic, and antifouling response of copper alloy nets. Factors to be determined from these experiments, such as drag, cage dynamic loads, material loss, and biological growth – well documented for nylon netting but not fully understood for copper-nickel alloy nets – will help to design fish cage enclosures made from these alloys. The East China Sea Fisheries Research Institute, in Shanghai, China, is also conducting experimental investigations on copper alloys for ICA.

Copper-zinc alloys

The Mitsubishi-Shindoh Co., Ltd., has developed a proprietary copper-zinc brass alloy, UR30™, specifically designed 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 fabricated into chain link, woven, or other types of flexible mesh. Corrosion rates depend on the depth of submersion and seawater conditions. The average reported corrosion rate reported for the alloy is <5 μm/yr based on 2- and 5-year exposure trials in seawater.[51]

The Ashimori Industry Company, Ltd.,[52] has installed approximately 300 flexible cages with woven chain link UR30™ meshes in Japan to raise Seriola (i.e., yellowtail, amberjack, kingfish, hamachi). The company has installed another twenty-eight UR30™ cages to raise Atlantic salmon at the Van Diemen Aquaculture operations in Tasmania, Australia. In Chile, EcoSea Farming S.A. expects to have installed a total of approximately forty woven chain link UR30™ mesh cages by the end of 2010 to raise trout and Atlantic salmon;[51] and in Panama and the USA, demonstrations and trials are underway using flexible cages with woven chain link UR30™.

To date, in over 10 years of aquaculture experience, chain link mesh fabricated by UR30™ alloys have not suffered from dezincification, stress corrosion cracking, or erosion corrosion.

Additional information about UR30™ can be found at the following Websites: chemical composition of UR30™[53]; physical properties of UR30™[54]; diameters available for UR30™[55]; corrosion resistance of UR30™[56]; and mechanical properties of UR30™[57].

Alternative copper-zinc alloys for aquaculture are being developed by other companies but have not yet been deployed in commercial operations.

Copper-nickel alloys

Copper-nickel alloys were developed specifically for seawater applications over five decades ago. Today, these alloys are being investigated for their potential use in aquaculture.

Copper-nickel alloys for marine applications are usually comprised of 90% copper, 10% nickel, plus small amounts of manganese and iron to enhance corrosion resistance. The seawater corrosion resistance of copper-nickel alloys results in a thin, adherent, protective surface film which forms naturally and quickly on the metal upon exposure to clean seawater.[58]

The rate of corrosion protective formation is temperature dependent. 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, it could take 2-3 months for the protection to mature. But once a good surface film forms, corrosion rates decrease, normally to 0.02-0.002 mm/yr, as protective layers develop over a period of years.[59] 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, pins, lag bolts, and staples in wooden sailing vessels in marine environments. The alloys are often composed of 96% copper, 3% silicon, and 1% manganese. The inclusion of silicon strengthens the metal.

As with the copper-nickel alloys, corrosion resistance of copper-silicon is due to protective films that form on the surface over a period of time. General corrosion rates of 0.025-0.050mm have been observed in quiet waters. This rate decreases towards the lower end of the range over long-term exposures (e.g., 400-600 days). There is generally no pitting with the silicon-bronzes and, if pitting does occur, the pits are small. Also there is good resistance to erosion corrosion up to moderate flow rates. Because copper-silicon is weldable, rigid cages can be constructed with this material. Also, because welded copper-silicon mesh is lighter than copper-zinc chain link, aquaculture enclosures made with copper-silicon may be lighter in weight and therefore a potentially less expensive alternative.

Luvata Appleton, LLC, is researching and developing a line of copper-silicon alloy woven meshes and welded meshes under the patent-pending trade name Seawire.™[60]. Copper-silicon alloy meshes have been developed by the firm to raise various marine organisms in test trials that are now in various stages of evaluation. These include raising cobia in Panama, lobsters in Maine, and crabs in the Chesapeake Bay. The company is working with various 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. Results will be provided when the studies are concluded.

References

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  12. ^ Half Of Fish Consumed Globally Is Now Raised On Farms, Study Finds Science Daily, September 8, 2009
  13. ^ Design Guide: Copper Alloy Mesh in Marine Aquaculture, International Copper Research Association Inc. (INCRA), 1984
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  60. ^ www.luvata.com; Seawire™ is a trademark of Luvata Appleton, LLC. The company intends to market a wide range of alloys in addition to copper-silicon under this trademark

Further reading

  • Design Guide: Copper Alloy Mesh in Marine Aquaculture, 1984, International Copper Research Association (INCRA) 704/5.
  • Metal Corrosion in Boats, Nigel Warren and Adlard Coles, Nautical, 1998.
  • Galvanic Corrosion: A Practical Guide for Engineers, R. Francis, 2001, NACE Press.
  • Marine Corrosion Causes and Prevention, F. LaQue, John Wiley and Sons, 1975.
  • The Selection of Materials for Seawater cooling Systems: A Practical Guide for Engineers, R. Francis, 2006, NACE Press.
  • Guidelines for the Use of Copper Alloys in Seawater, A. Tuthill. 1987. CDA/ Nickel Institute Publication.
  • The Brasses: Properties and Applications, CDA UK Publication 117.
  • Copper in the Ocean Environment, Neal Blossom, American Chemet Corporation.
  • ICA Project 438: Experimental usage of copper nickel alloy mesh in aquaculture, Mario E. Edding, Hector Flores, Claudio Miranda, Universidad Catholica del Norte, July 1995

External links

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