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'''Overfishing''' occurs when [[fishing]] activities reduce fish stocks below an acceptable level.  This can occur in any body of water from a pond to the oceans.   More precise [[biology|biological]] and [[bioeconomics|bioeconomic]] terms define 'acceptable level'.

''Biological overfishing'' occurs when [[fishing mortality]] has reached a level where the stock biomass has negative marginal growth (slowing down biomass growth), as indicated by the red area in the figure. 
(Fish are being taken out of the water so quickly that the replenishment of stock by breeding slows down.  If the replenishment continues to slow down for long enough, replenishment will go into reverse and the population will decrease.) 

''Economic'' or ''bioeconomic overfishing'' additionally considers the cost of fishing and defines overfishing as a situation of negative marginal growth of [[resource rent]].  (Fish are being taken out of the water so quickly that the growth in the profitability of fishing slows down.  If this continues  for long enough, profitability will decrease.)  

A more dynamic definition of ''economic overfishing'' may also include a relevant discount rate and present value of flow of resource rent over all future catches.

Ultimately overfishing may lead to [[resource depletion]] in cases of subsidised fishing, low biological growth rates and critical low biomass levels (e.g. by [[depensation|critical depensation]] growth properties).

The ability of nature to restore the [[fishery|fisheries]] also depends on whether the [[ecosystem]]s are still in a state to allow fish numbers to build again. Dramatic changes in species composition may establish other equilibrium energy flows that involve other species compositions than had been present before (ecosystem shift). (For example: remove nearly all the trout, the carp take over and make it near impossible for the trout to re-establish a breeding population.)

==Fish production and demand==

A major international scientific study released in November 2006 in the journal ''[[Science (journal)|Science]]'' found that about one-third of all fishing stocks worldwide have collapsed (with a collapse being defined as a decline to less than 10% of their maximum observed abundance), and that if current trends continue all fish stocks worldwide will collapse within fifty years.{{ref|bbc-2006}}

The [[FAO]] State of World Fisheries and Aquaculture 2004 report estimates that in 2003, of the main fish stocks or groups of resources for which assessment information is available, "approximately one-quarter were overexploited, depleted or recovering from depletion (16%, 7% and 1% respectively) and needed rebuilding."{{ref|fao-2004}}

The threat of overfishing is not limited to the target species only. As [[trawlers]] resort to deeper and deeper waters to fill their nets, they have begun to threaten delicate [[pelagic|deep-sea ecosystems]] and the fish that inhabit them, such as the [[coelacanth]].{{ref|guardian}} In the [[May 15]] [[2003]] issue of the journal ''[[Nature (journal)|Nature]]'', it is estimated that 10% of large predatory fish remain compared to levels before commercial fishing.{{ref|journal-nature}} Many fisheries experts, however, consider this claim to be exaggerated] with respect to tuna populations {{ref|journal-nature2}}.

From 1950 (18 million tonnes) to 1969 (56 million tonnes) fishfood production grew by about 5% each year; from 1969 onward production has raised 8% annually.{{ref|fao-2000}} It is expected that this demand will continue to rise, and MariCulture Systems estimated in 2002 that, by 2010, seafood production would have to increase by over 15.5 million tonnes to meet the desire of Earth's growing population.{{ref|sargo}} This is likely to further aggravate the problem of overfishing, unless aquaculture technology expands to meet the needs of human population.

Overfishing has depleted fish populations to the point that large scale commercial fishing, on average around the world, is not economically viable without [[subsidy|government assistance]].  By the 1980s, economists estimated that for every $1 earned fishing, $1.77 had to be spent in catching and marketing the fish.{{ref|platt}} Some species' stocks are so depleted that consumers are often unlikely to get what they think they are purchasing, due to a phenomenon called "species substitutions," where less desirable species are labeled and marketed under the names of more expensive ones.  For example, genetic analysis shows that approximately 70% of fish sold as the highly-prized "[[red snapper (fish)|red snapper]]" (''Lutjanus campechanus'') are other species.{{ref|red-snapper}}

==Mitigation==
With present and forecast levels of the world population it is not possible to solve the overfishing issue; however, there are mitigation measures that can save selected fisheries and forestall the collapse of others.

In order to meet the problems of overfishing, a precautionary approach and Harvest Control Rule (HCR) management principles have been introduced in the main fisheries around the world. The Traffic Light colour convention introduces sets of rules based on predefined critical values, which could be adjusted as more information is gained.

The "[[United Nations Convention on the Law of the Sea]]" treaty deals with aspects of '''overfishing''' in articles 61, 62, and 65.{{ref|sea-law}}
*Article 61 requires all coastal states to ensure that the maintenance of living resources in their [[exclusive economic zone]]s is not endangered by over-exploitation. The same article addresses the maintenance or restoration of populations of species above levels at which their reproduction may become seriously threatened.

*Article 62 provides that coastal states: "shall promote the objective of optimum utilization of the living resources in the exclusive economic zone without prejudice to Article 61"
*Article 65 provides generally for the rights of, inter alia, coastal states to prohibit, limit, or regulate the exploitation of marine mammals.

Overfishing can be viewed as a case of the [[tragedy of the commons]]; in that sense, solutions would promote [[property right]]s, such as [[privatization]] and [[fish farming]]. Daniel K. Benjamin, in ''Fisheries are Classic Example of the "Tragedy of the Commons"'', cites research by Grafton, Squires, and Fox to support the idea that privatization can solve the overfishing problem{{ref|tragedy}}:
:''According to recent research on the [[British Columbia]] [[halibut]] fishery, where the commons has been at least partly privatized, substantial ecological and economic benefits have resulted. There is less damage to fish stocks, the fishing is safer, and fewer resources are needed to achieve a given harvest.''

Another possible solution, at least for some areas, is fishing [[quotas]], so fishermen can only legally take a certain amount of fish. A more radical possibility is declaring certain areas of the sea "no-go zones" and make fishing there strictly illegal, so the fish in that area have time to recover and repopulate.

Controlling consumer behaviour and demand is a key in mitigating action. Worldwide a number of initiatives emerged to provide consumers with information regarding the conservation status of the seafood available to them. The [http://overfishing.org/pages/guide_to_good_fish.php Guide to Good Fish Guides] lists a number of these.

==Instances of overfishing==
Examples of the outcomes from overfishing exist in areas such as the [[North Sea]] of [[Europe]] and the [[Grand Banks]] off the east coast of [[North America]]. In these locations, overfishing has not only proved disastrous to fish stocks but also to the fishing communities relying on the harvest. Like other [[Primary sector of industry|extractive industries]] such as forestry and hunting, fishery is susceptible to economic interaction between ownership or stewardship and sustainability, otherwise known as the [[tragedy of the commons]]. 

The [[Peru|Peruvian]] coastal [[Peruvian anchoveta|anchovy]] fisheries crashed in the [[1970s]] after overfishing, following an [[El Niño]] season {{ref|peru}} which largely depleted anchovies from its waters.{{ref|fiscal-1982}}{{ref|library-congress}} Anchovies had previously been a major natural resource in Peru; indeed, 1971 alone yielded 10.2 million metric tons of anchovies. However, in the following year, and the four after that, the Peruvian fleet's catch amounted to only about 4 million tons.{{ref label|peru|7|a}} This was a major loss to Peru's economy.

The collapse of the [[cod]] fishery off [[Newfoundland]], and the 1992 decision by [[Canada]] to impose an indefinite [[moratorium]] on the [[Grand Banks]], is a dramatic example of the consequences of overfishing.  <ref> ch 11-12. Mark Kurlansky (1997). Cod: A Biography of the Fish That Changed the World. New York: Walker. ISBN 0-8027-1326-2. </ref>

The sole (''[[Solea solea]]'') fisheries in the [[Irish Sea]], the west [[English Channel]], and other locations have become overfished to the point of virtual collapse, according to the UK government's official [[Biodiversity Action Plan]]. The United Kingdom has created elements within this plan to attempt to restore this fishery, but [[overpopulation|the expanding human population]] and the expanding demand for fish has reached a point where demand for food threatens the stability of these fisheries, if not the species' survival.

==References==
<div class="references-small">
<references/>

# {{note|bbc-2006}} "[http://news.bbc.co.uk/2/hi/science/nature/6108414.stm 'Only 50 years left' for sea fish]", BBC News. 2 November 2006.
# {{note|fao-2004}} "[http://www.fao.org/documents/show_cdr.asp?url_file=/DOCREP/007/y5600e/y5600e05.htm@ The Status of the Fishing Fleet]," ''The State of World Fisheries and Aquaculture: 2004.''
# {{note|guardian}} "[http://observer.guardian.co.uk/world/story/0,16937,1681745,00.html Dinosaur fish pushed to the brink by deep-sea trawlers]", The Observer Newspaper, 2006.
# {{note|journal-nature}} "[http://www.nature.com/nature/journal/v423/n6937/abs/nature01610.html Rapid Worldwide Depletion of Predatory Fish Communities]," Nature. 2003.
#{{note|journal-nature2}} "[http://www.nature.com/nature/journal/v434/n7037/full/nature03582.html Decline of Pacific tuna populations exaggerated]," Nature 434:E1-E2, 28 April 2005.
# {{note|fao-2000}} "[http://www.fao.org/documents/show_cdr.asp?url_file=/DOCREP/003/X8002E/x8002e04.htm World Review of Fisheries and Aquaculture]," ''The State of World Fisheries and Aquaculture: 2000.''
# {{note|sea-law}} [http://www.un.org/Depts/los/convention_agreements/texts/unclos/part5.htm Text of the United Nations Convention on the Law of the Sea: Part V]
# {{note|sargo}} [http://www.sargo.net/aquaculture.htm Aquaculture], MariCulture Systems. 2004.
# {{note|tragedy}} Benjamin, Daniel K (2001). "[http://web.archive.org/web/20050219192447/http://perc.org/publications/percreports/march2001/tangents.php  Fisheries are Classic Example of the Tragedy of the Commons,]" PERC Reports, 19(1).
#{{note|peru}} "[http://www.american.edu/TED/anchovy.htm Peruvian Anchovy Case: Anchovy Depletion and Trade]," Trade and Environment Database, 1999.
#{{note|fiscal-1982}} "Foreign Assistance Legislation for Fiscal Year 1982," Committee on Foreign Affairs, 1981.
#{{note|library-congress}} "[http://countrystudies.us/peru/55.htm Peru - Fishing]," Federal Research Division of the U.S. Library of Congress.
#{{note|ng-2007}} "[http://news.nationalgeographic.com/news/2007/03/070329-sharks-shellfish.html Shark Declines Threaten Shellfish Stocks, Study Says]", National Geographic News. 29 March 2007.
#{{note|red-snapper}} "[http://www.sciencedaily.com/releases/2004/07/040715081351.htm Scientists Find 75 Percent Of Red Snapper Sold In Stores Is Really Some Other Species], Sciencedaily.com.  2004.
#{{note|platt}} Platt McGinn A (1998). "Promoting Sustainable Fisheries," State of the World, pp.59-78.
</div>

==Further reading==
*Clover, Charles. 2004. ''The End of the Line: How overfishing is changing the world and what we eat''. Ebury Press, London. ISBN 0-09-189780-7
*Kurlansky, Mark. (1997). Cod: A Biography of the Fish That Changed the World. New York: Walker. ISBN 0-8027-1326-2. 
*Loder, Natasha.  2005. [http://www.conbio.org/cip/article63poi.cfm Point of No Return]. ''Conservation in Practice'' 6(3):28-34.  On overfishing as an evolutionary force and the "Darwinian debt" for future generations.

==references==
Adapted from the Wikipedia article, "Overfishing" http://en.wikipedia.org/wiki/Overfishing, used under the GNU Free Documentation License.

[[Category:Ecology]]
[[Category:Commercial fishing]]
[[Category:Fisheries science]]