Editing Mariculture (section)

==Environmental effects==
Mariculture has rapidly expanded over the last two decades due to new technology, improvements in formulated feeds, greater biological understanding of farmed species, increased water quality within closed farm systems, greater demand for [[seafood products]], site expansion and government interest.<ref>{{cite journal|author=DeVoe, M.R. |year=1994|title=Aquaculture and the marine environment: policy and management issues and opportunities in the United States|journal= Bull. Natl. Res. Inst. Aquacult.|volume= Supp. 1|pages=111–123}}</ref><ref>{{Cite journal | doi = 10.1016/S0044-8486(03)00474-5| title = Management of environmental impacts of marine aquaculture in Europe| journal = Aquaculture| volume = 226| issue = 1–4| pages = 139–163| year = 2003| last1 = Read | first1 = P. | last2 = Fernandes | first2 = T. | bibcode = 2003Aquac.226..139R}}</ref><ref>Ross, A. (1997). ''Leaping in the Dark: A Review of the Environmental Impacts of Marine Salmon Farming in Scotland and Proposals for Change''. Scottish Environment Link, Perth, Scotland.</ref> As a consequence, mariculture has been subject to some controversy regarding its social and [[environmental impact]]s.<ref>{{Cite journal | doi = 10.1016/S0044-8486(97)00186-5| title = Regulating the local environmental impact of intensive marine fish farming I. The concept of the MOM system (Modelling-Ongrowing fish farms-Monitoring)| journal = Aquaculture| volume = 158| issue = 1–2| pages = 85–94| year = 1997| last1 = Ervik | first1 = A. | last2 = Hansen | first2 = P. K. | last3 = Aure | first3 = J. | last4 = Stigebrandt | first4 = A. | last5 = Johannessen | first5 = P. | last6 = Jahnsen | first6 = T. | bibcode = 1997Aquac.158...85E}}</ref><ref name=jen>Jennings, S., Kaiser, M.J., Reynolds, J.D. (2001). Marine Fisheries Ecology. Blackwell, Victoria.</ref> Commonly identified environmental impacts from marine farms are:

# Wastes from cage cultures;
# Farm escapees and [[invasive species|invasives]];
# [[Genetic pollution]] and disease and parasite transfer;
# [[Habitat (ecology)|Habitat]] modification.

As with most farming practices, the degree of environmental impact depends on the size of the farm, the cultured species, stock density, type of feed, [[hydrography]] of the site, and [[husbandry]] methods.<ref>{{Cite journal | doi = 10.1016/0025-326X(95)00100-2| title = The environmental impact of marine fish culture: Towards a sustainable future| journal = Marine Pollution Bulletin| volume = 31| issue = 4–12| pages = 159–166| year = 1995| last1 = Wu | first1 = R. S. S. | bibcode = 1995MarPB..31..159W}}</ref> The adjacent diagram connects these causes and effects.

===Wastes from cage cultures===
Mariculture of [[finfish]] can require a significant amount of [[fishmeal]] or other high protein food sources.<ref name=jen /> Originally, a lot of fishmeal went to waste due to inefficient feeding regimes and poor digestibility of formulated feeds which resulted in poor [[feed conversion ratio]]s.<ref name=forrest>Forrest B, Keeley N, Gillespie P, Hopkins G, Knight B, Govier D. (2007). Review of the ecological effects of marine finfish aquaculture: final report. Prepared for Ministry of Fisheries. Cawthron Report No. 1285.</ref>

In cage culture, several different methods are used for feeding farmed fish – from simple hand feeding to sophisticated computer-controlled systems with automated food dispensers coupled with ''in situ'' uptake sensors that detect consumption rates.<ref name=black>{{Cite book| editor = Steele, John H.| editor2 = Thorpe, Steve A.| editor3 = Turekian, Karl K.| publisher = Academic Press| doi = 10.1006/rwos.2001.0487| chapter = Mariculture, Environmental, Economic and Social Impacts of| title = Encyclopedia of Ocean Sciences| pages = 1578–1584| year = 2001| last1 = Black| first1 = K. D.| isbn = 9780122274305| chapter-url-access = registration| chapter-url = https://archive.org/details/encyclopediaofoc0000unse| url = https://archive.org/details/encyclopediaofoc0000unse| url-access = registration}}</ref> In coastal fish farms, overfeeding primarily leads to increased disposition of detritus on the seafloor (potentially smothering seafloor dwelling invertebrates and altering the physical environment), while in hatcheries and land-based farms, excess food goes to waste and can potentially impact the surrounding catchment and local coastal environment.<ref name=jen /> This impact is usually highly local, and depends significantly on the settling velocity of waste feed and the current velocity (which varies both spatially and temporally) and depth.<ref name=jen /><ref name=black />

===Farm escapees and invasives===
The impact of escapees from aquaculture operations depends on whether or not there are wild [[conspecifics]] or close relatives in the receiving environment, and whether or not the escapee is reproductively capable.<ref name=black /> Several different mitigation/prevention strategies are currently employed, from the development of infertile [[triploid]]s to land-based farms which are completely isolated from any marine environment.<ref name=kat/><ref>{{cite journal|author=Nell, J.A. |year=2002|title=Farming triploid oysters|journal= Aquaculture |volume=210|issue=1–4|pages= 69–88|doi=10.1016/s0044-8486(01)00861-4|bibcode=2002Aquac.210...69N }}</ref><ref>{{cite journal|last=Pfeiffer |first=T. |year=2010|title=Recirculation Technology: the future of aquaculture |journal=Resource, Engineering & Technology for a Sustainable World |volume=17|issue=3|pages= 7–9}}</ref><ref>{{Cite journal | doi = 10.1111/j.1365-2109.2005.01326.x| title = Growth and mortality of sibling triploid and diploid Sydney rock oysters, Saccostrea glomerata (Gould), in the Camden Haven River| journal = Aquaculture Research| volume = 36| issue = 11| pages = 1093–1103| year = 2005| last1 = Troup | first1 = A. J. | last2 = Cairns | first2 = S. C. | last3 = Simpson | first3 = R. D. | doi-access = free}}</ref> Escapees can adversely impact local ecosystems through [[Hybrid (biology)|hybridization]] and loss of genetic diversity in native stocks, increase negative interactions within an ecosystem (such as [[predation]] and [[competition]]), disease transmission and habitat changes (from [[trophic cascade]]s and ecosystem shifts to varying sediment regimes and thus [[turbidity]]).

The accidental introduction of invasive species is also of concern. Aquaculture is one of the main vectors for invasives following accidental releases of farmed stocks into the wild.<ref name=naylor>{{Cite journal | doi = 10.1126/science.1064875| title = ECOLOGY: Aquaculture--A Gateway for Exotic Species| journal = Science| volume = 294| issue = 5547| pages = 1655–1656| year = 2001| last1 = Naylor | first1 = R. L.| pmid=11721035| s2cid = 82810702}}</ref> One example is the Siberian sturgeon (''Acipenser baerii'') which accidentally escaped from a fish farm into the [[Gironde Estuary]] (Southwest France) following a severe storm in December 1999 (5,000 individual fish escaped into the estuary which had never hosted this species before).<ref>{{Cite journal
 | pmid = 18306893
| year = 2008
| last1 = Maury-Brachet
| first1 = R
| title = The 'storm of the century' (December 1999) and the accidental escape of Siberian sturgeons (Acipenser baerii) into the gironde estuary (southwest France). An original approach for metal contamination
| journal = Environmental Science and Pollution Research International
| volume = 15
| issue = 1
| pages = 89–94
| last2 = Rochard
| first2 = E
| last3 = Durrieu
| first3 = G
| last4 = Boudou
| first4 = A
 | doi=10.1065/espr2007.12.469
| bibcode = 2008ESPR...15...89M
| s2cid = 46148803
}}</ref> [[Mollusc]]an farming is another example whereby species can be introduced to new environments by ‘hitchhiking’ on farmed molluscs. Also, farmed molluscs themselves can become dominate predators and/or competitors, as well as potentially spread pathogens and parasites.<ref name=naylor />

===Genetic pollution, disease, and parasite transfer===
One of the primary concerns with mariculture is the potential for [[disease]] and [[parasite]] transfer. Farmed stocks are often [[selectively bred]] to increase disease and parasite resistance, as well as improving growth rates and quality of products.<ref name=jen /> As a consequence, the [[genetic diversity]] within reared stocks decreases with every generation – meaning they can potentially reduce the genetic diversity within wild populations if they escape into those wild populations.<ref name=forrest /> Such [[genetic pollution]] from escaped aquaculture stock can reduce the wild population's ability to adjust to the changing natural environment. Species grown by mariculture can also harbour diseases and parasites (e.g., lice) which can be introduced to wild populations upon their escape. An example of this is the parasitic [[Sea louse|sea lice]] on wild and farmed Atlantic salmon in Canada.<ref>{{Cite journal | doi = 10.1038/451023a| pmid = 18172486| title = Aquaculture: The price of lice| journal = Nature| volume = 451| issue = 7174| pages = 23–24| year = 2008| last1 = Rosenberg | first1 = A. A. | bibcode = 2008Natur.451...23R| s2cid = 32766703| doi-access = free}}</ref> Also, non-indigenous species which are farmed may have resistance to, or carry, particular diseases (which they picked up in their native habitats) which could be spread through wild populations if they escape into those wild populations. Such ‘new’ diseases would be devastating for those wild populations because they would have no immunity to them.<ref>{{Cite web|title=Wilderness Connect|url=https://wilderness.net/learn-about-wilderness/threats/invasive.php|access-date=2020-11-12|website=wilderness.net|language=en}}</ref>

===Habitat modification===
With the exception of [[benthic]] habitats directly beneath marine farms, most mariculture causes minimal destruction to habitats. However, the destruction of [[mangrove]] forests from the farming of shrimps is of concern.<ref name=jen /><ref name=black /> Globally, shrimp farming activity is a small contributor to the destruction of [[mangrove]] forests; however, locally it can be devastating.<ref name=jen /><ref name=black /> [[Mangrove]] forests provide rich matrices which support a great deal of [[biodiversity]] – predominately juvenile fish and crustaceans.<ref name=black /><ref name=kaiser>Kaiser, M.J., Attrill, M.J., Jennings, S., Thomas, D.N., Barnes, D.K.A., Brierley, A.S., Polunin, N.V.C., Raffaelli, D.G., Williams, P.J.le B. (2005). Marine Ecology: Processes, Systems and Impacts. Oxford University Press, New York.</ref> Furthermore, they act as buffering systems whereby they reduce coastal erosion, and improve water quality for in situ animals by processing material and ‘filtering’ sediments.<ref name=black /><ref name=kaiser /><ref>Trujillo, A.P., Thurman, H.V. (2008) Essentials of Oceanography Ninth Edition. Pearson Prentice Hall. New Jersey.</ref>

===Others===
In addition, [[nitrogen]] and [[phosphorus]] compounds from food and waste may lead to blooms of [[phytoplankton]], whose subsequent degradation can drastically reduce [[oxygen]] levels. If the [[algae]] are toxic, [[fish]] are killed and [[shellfish]] contaminated.<ref name=kat/><ref name="multiples"/><ref>{{cite web|publisher=
UNEP, World Fisheries Trust|year=2002|url=http://www.cbd.int/doc/meetings/mar/temctre-01/official/temctre-01-02-en.pdf |title=THE EFFECTS OF MARICULTURE ON BIODIVERSITY}}</ref> These algal blooms are sometimes referred to as harmful algal blooms, which are caused by a high influx of nutrients, such as nitrogen and phosphorus, into the water due to run-off from land based human operations.<ref>{{Cite web|last=US EPA|first=OW|date=2013-06-03|title=Harmful Algal Blooms|url=https://www.epa.gov/nutrientpollution/harmful-algal-blooms|access-date=2020-11-12|website=US EPA|language=en}}</ref>

Over the course of rearing various species, the sediment on bottom of the specific body of water becomes highly metallic with influx of copper, zinc and lead that is being introduced to the area. This influx of these heavy metals is likely due to the buildup of fish waste, uneaten fish feed, and the paint that comes off the boats and floats that are used in the mariculture operations.<ref>{{Cite journal|last1=Liang|first1=Peng|last2=Wu|first2=Sheng-Chun|last3=Zhang|first3=Jin|last4=Cao|first4=Yucheng|last5=Yu|first5=Shen|last6=Wong|first6=Ming-Hung|date=2016-04-01|title=The effects of mariculture on heavy metal distribution in sediments and cultured fish around the Pearl River Delta region, south China|url=http://www.sciencedirect.com/science/article/pii/S0045653515303052|journal=Chemosphere|language=en|volume=148|pages=171–177|doi=10.1016/j.chemosphere.2015.10.110|pmid=26807936|bibcode=2016Chmsp.148..171L|issn=0045-6535}}</ref>