Overfishing is the removal of a species offish (i.e.fishing) from abody of water at a rate greater than that the species can replenish itspopulation naturally (i.e. theoverexploitation of thefishery's existingfish stock), resulting in the species becoming increasinglyunderpopulated in that area. Overfishing can occur in water bodies of any sizes, such asponds,wetlands,rivers,lakes oroceans, and can result inresource depletion, reduced biological growth rates and lowbiomass levels. Sustained overfishing can lead tocritical depensation, where the fish population is no longer able to sustain itself. Some forms of overfishing, such as theoverfishing of sharks, has led to the upset of entiremarine ecosystems.[1] Types of overfishing include growth overfishing, recruitment overfishing, and ecosystem overfishing. Overfishing not only causes negative impacts on biodiversity and ecosystem functioning, but also reduces fish production, which subsequently leads to negative social and economic consequences.[2]
The ability of a fishery to recover from overfishing depends on whether its overallcarrying capacity and the variety of ecological conditions are suitable for the recovery. Dramatic changes in species composition can result in anecosystem shift, where other equilibrium energy flows involve species compositions different from those that had been present before the depletion of the original fish stock. For example, oncetrout have been overfished,carp might exploit the change incompetitive equilibria and take over in a way that makes it impossible for the trout to re-establish a breeding population.
Since the growth of globalfishing enterprises after the 1950s, intensive fishing has spread from a few concentrated areas to encompass nearly all fisheries. The scraping of theocean floor inbottom dragging is devastating tocoral,sponges and other slower-growingbenthic species that do not recover quickly, and that provide a habitat for commercial fisheries species. This destruction alters the functioning of the ecosystem and can permanently alter species' composition andbiodiversity.Bycatch, the collateral capture of unintended species in the course of fishing, is typically returned to the ocean only to die from injuries or exposure. Bycatch represents about a quarter of all marine catch. In the case ofshrimp capture, the mass of bycatch is five times larger than that of the shrimp caught.
A report byFAO in 2020 stated that "in 2017, 34 percent of the fish stocks of the world's marine fisheries were classified as overfished".[3]: 54 Mitigation options include: Government regulation, removal ofsubsidies, minimizing fishing impact,aquaculture andconsumer awareness.
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Overfishing has stripped many fisheries around the world of theirstocks. TheUnited NationsFood and Agriculture Organization estimated in a 2018 report that 33.1% of world fish stocks are subject to overfishing.[4] Significant overfishing has been observed in pre-industrial times. In particular, the overfishing of the westernAtlantic Ocean from the earliest days ofEuropean colonisation of the Americas has been well documented.[5]
The fraction of fish stocks that are within biologically sustainable levels has exhibited a decreasing trend, from 90% in 1974 to 66.9% in 2015. In contrast, the percentage of stocks fished at biologically unsustainable levels increased from 10% in 1974 to 33.1% in 2015, with the largest increases in the late-1970s and 1980s.
In 2015, maximally sustainably fished stocks (formerly termed fully fished stocks) accounted for 59.9% and underfished stocks for 7% of the total assessed stocks.[7] While the proportion of underfished stocks decreased continuously from 1974 to 2015, the maximally sustainably fished stocks decreased from 1974 to 1989, and then increased to 59.9% in 2015.[7]
In 2015, among the 16 major statistical areas, theMediterranean andBlack Sea had the highest percentage (62.2%) of unsustainable stocks, closely followed by the SoutheastPacific 61.5% and SouthwestAtlantic 58.8%. In contrast, the Eastern Central Pacific, Northeast Pacific (Area 67), Northwest Pacific (Area 61), Western Central Pacific and Southwest Pacific had the lowest proportion (13 to 17%) of fish stocks at biologically unsustainable levels.[7]
Daniel Pauly, afisheries scientist known for pioneering work on the human impacts on global fisheries, has commented:[8]
It is almost as though we use our military to fight the animals in the ocean. We are gradually winning this war toexterminate them. And to see this destruction happen, for nothing really – for no reason – that is a bit frustrating. Strangely enough, these effects are all reversible, all the animals that have disappeared would reappear, all the animals that were small would grow, all the relationships that you can't see any more would re-establish themselves, and the system would re-emerge.
According to the Secretary General of the 2002World Summit on Sustainable Development, "Overfishing cannot continue, the depletion of fisheries poses a major threat to the food supply of millions of people."[9]
The fishing down the food web is something that occurs when overfishing arises. Once all larger fish are caught, the fisherman will start to fish the smaller individuals, which would lead to more fish needing to be caught to keep up with demand.[10] This decreases fish populations, as well as genetic diversity of the species, making them more susceptible to disease, and less likely to adapt to their stressors and the environment.[11] Additionally, catching smaller fish leads to breeding of smaller offspring, which can be problematic for fish. In many species, the smaller the female, the lessfecund it is, impacting the fish population.[12]
There are three recognized types of biological overfishing: growth overfishing, recruit overfishing, and ecosystem overfishing.
Growth overfishing occurs when fish are harvested at an average size that is smaller than the size that would produce themaximum yield per recruit. Arecruit is an individual that makes it to maturity, or into the limits specified by a fishery, which are usually size or age.[14] This makes the total yield less than it would be if the fish were allowed to grow to an appropriate size. It can be countered by reducing fishing mortality to lower levels and increasing the average size of harvested fish to a size that will allow maximum yield per recruit.[15][16]
Recruitment overfishing happens when the mature adult population (spawningbiomass) is depleted to a level where it no longer has the reproductive capacity to replenish itself—there are not enough adults to produce offspring.[15] Increasing the spawning stock biomass to a target level is the approach taken by managers to restore an overfished population to sustainable levels. This is generally accomplished by placing moratoriums,quotas, andminimum size limits on a fish population.
Ecosystem overfishing occurs when the balance of theecosystem is altered by overfishing. With declines in the abundance of large predatory species, the abundance of smallforage type increases causing a shift in the balance of the ecosystem towards smaller fish species.
Examples of overfishing exist in areas such as theNorth Sea, theGrand Banks of Newfoundland and theEast China Sea.[17][18] In these locations, overfishing has not only proved disastrous to fish stocks, but also to the fishing communities relying on the harvest. Like otherextractive industries such as forestry and hunting, fisheries are susceptible to economic interaction between ownership or stewardship andsustainability, otherwise known as thetragedy of the commons.
Overfishing not only causes negative impacts on biodiversity and ecosystem functioning, but also reduces fish production, which subsequently leads to negative social and economic consequences.[2] According to a 2008 UN report, the world's fishing fleets are losing US$50 billion each year due to depleted stocks and poorfisheries management. The report, produced jointly by theWorld Bank and the UNFood and Agriculture Organization (FAO), asserts that half the world'sfishing fleet could be scrapped with no change in catch. In addition, thebiomass of globalfish stocks have been allowed to run down to the point where it is no longer possible to catch the amount of fish that could be caught.[35]
Increased incidence ofschistosomiasis in Africa has been linked to declines of fish species that eat the snails carrying the disease-causing parasites.[36]
Massive growth ofjellyfish populations threaten fish stocks, as they compete with fish for food, eat fish eggs, and poison or swarm fish, and can survive in oxygen depleted environments where fish cannot; they wreak massive havoc on commercial fisheries. Overfishing eliminates a major jellyfish competitor and predator, exacerbating the jellyfish population explosion.[37] Both climate change and a restructuring of the ecosystem have been found to be major roles in an increase in jellyfish population in the Irish Sea in the 1990s.[38]
According to the 2019Global Assessment Report on Biodiversity and Ecosystem Services published by theIntergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, overfishing is a primary driver of massextinction in the world's oceans.[39] A 2021 study published in the journalNature asserted that the "primary cause" of oceandefaunation is overfishing.[31] Other studies have shown that overfishing has reduced fish and marine mammalbiomass by 60% since the 1800s,[40] and is currently driving over one-third ofsharks andrays to extinction.[41]
The notion of overfishing hinges on what is meant by an "acceptable level" of fishing. More precisebiological andbioeconomic terms define acceptable level as follows:
A model proposed in 2010 for predicting acceptable levels of fishing is the Harvest Control Rule (HCR),[43] which is a set of tools and protocols with which management has some direct control of harvest rates and strategies in relation to predicting stock status, and long-termmaximum sustainable yields. Constant catch and constant fishing mortality are two types of simple harvest control rules.[44]
Fishing capacity can also be defined using an input or output orientation.
Technical efficiency of each vessel of the fleet is assumed necessary to attain this maximum catch. The degree ofcapacity utilization results from the comparison of the actual level of output (input) and the capacity output (input) of a vessel or a fleet.[clarification needed]
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 color convention introduces sets of rules based on predefined critical values, which can be adjusted as more information is gained.
TheUnited Nations Convention on the Law of the Sea (UNCLOS) treaty deals with aspects of overfishing in articles 61, 62, and 65.[47]
According to some observers, overfishing can be viewed as an example of thetragedy of the commons; appropriate solutions would therefore promoteproperty rights through, for instance,privatization andfish farming. Daniel K. Benjamin, inFisheries 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: According to recent research on theBritish Columbiahalibut 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."[48]
Another possible solution, at least for some areas, isquotas, restricting fishers to a specific quantity 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 have time to recover and repopulate.
In order to maximise resources some countries, e.g.,Bangladesh and Thailand, have improved the availability of family planning services. The resulting smaller populations have a decreased environmental footprint and reduced food needs.[49]
Controlling consumer behavior and demand is critical 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 "Guide to Good Fish Guides" lists a number of these.[50]
Many regulatory measures are available for controlling overfishing. These measures includefishing quotas,bag limits, licensing,closed seasons, size limits and the creation ofmarine reserves and othermarine protected areas.
A model of the interaction between fish and fishers showed that when an area is closed to fishers, but there are no catch regulations such asindividual transferable quotas, fish catches are temporarily increased but overall fishbiomass is reduced, resulting in the opposite outcome from the one desired for fisheries.[51] Thus, a displacement of the fleet from one locality to another will generally have little effect if the same quota is taken. As a result,management measures such as temporary closures or establishing amarine protected area of fishing areas are ineffective when not combined with individual fishing quotas. An inherent problem with quotas is that fish populations vary from year to year. A study has found that fish populations rise dramatically after stormy years due to more nutrients reaching the surface and therefore greater primary production.[52] To fish sustainably, quotas need to be changed each year to account for fish population.
Individual transferable quotas (ITQs) are fishery rationalization instruments defined under theMagnuson-Stevens Fishery Conservation and Management Act as limited access permits to harvest quantities of fish.Fisheries scientists decide the optimal amount of fish (total allowable catch) to be harvested in a certain fishery. The decision considers carrying capacity, regeneration rates and future values. Under ITQs, members of afishery are granted rights to a percentage of the total allowable catch that can be harvested each year. These quotas can be fished, bought, sold, or leased allowing for the least-cost vessels to be used. ITQs are used inNew Zealand,Australia,Iceland,Canada, and theUnited States.
In 2008, a large-scale study of fisheries that used ITQs compared to ones that did not provide strong evidence that ITQs can help to prevent collapses and restore fisheries that appear to be in decline.[53][54][55][56]
China bans fishing in theSouth China Sea for a period each year.[57]
Several countries are now effectively managing their fisheries. Examples includeIceland andNew Zealand.[58] TheUnited States has turned many of its fisheries around from being in a highly depleted state.[59]
Because government provided financial subsidies can make it economically viable to fish beyond biologically sustainable levels, several scientists have called for an end tofishery subsidies paid to deep-sea fisheries.
Fisheries scientistDaniel Pauly and economistUssif Rashid Sumaila have examined subsidies paid tobottom trawl fleets around the world. They found that US$152 million per year are paid to deep-sea fisheries. Without these subsidies, global deep-sea fisheries would operate at a loss of US$50 million a year. A great deal of the subsidies paid to deep-sea trawlers is to subsidize the large amount of fuel required to travel beyond the 200 mile limit and drag weighted nets.[27]
"There is surely a better way for governments to spend money than by paying subsidies to a fleet that burns 1.1 billion litres of fuel annually to maintain paltry catches of old growth fish from highly vulnerable stocks, while destroying their habitat in the process" –Pauly.[27]
"Eliminating global subsidies would render these fleets economically unviable and would relieve tremendous pressure on over-fishing and vulnerable deep-sea ecosystems" –Sumaila.[27]
Over 30 billion euros in publicsubsidies are directed tofisheries annually.[60][61]
Fishing techniques may be altered to minimize bycatch and reduce impacts on marine habitats. These techniques include using varied gear types depending on target species and habitat type. For example, a net with larger holes will allow undersized fish to avoid capture. Aturtle excluder device (TED) allows sea turtles and other megafauna to escape from shrimp trawls. Avoiding fishing in spawning grounds may allow fish stocks to rebuild by giving adults a chance to reproduce.
Aquaculture involves the farming of fish in captivity. This approach effectively privatizes fish stocks and creates incentives for farmers to conserve their stocks. It also reduces environmental impact. However, farmingcarnivorous fish, such assalmon, does not always reduce pressure on wild fisheries, since carnivorous farmed fish are usually fedfishmeal andfish oil extracted from wildforage fish. The various species of Pacific salmon and Atlantic salmon are relatively easy to raise in captivity and such aquacultural operations have existed for more than 150 years. Large scale releases of salmon raised in captivity to supplement wild salmon runs will usually increase fishing pressure on the much less abundant wild salmon runs.
Aquaculture played a minor role in the harvesting of marine organisms until the 1970s. Growth in aquaculture increased rapidly in the 1990s when the rate of wild capture plateaued. Aquaculture now provides approximately half of all harvested aquatic organisms. Aquaculture production rates continue to grow while wild harvest remains steady.
Fish farming can enclose the entirebreeding cycle of the fish, with fish being bred in captivity. Some fish prove difficult to breed in captivity and can be caught in the wild as juveniles and brought into captivity to increase their weight. With scientific progress, more species are being made to breed in captivity. This was the case withsouthern bluefin tuna, which were first bred in captivity in 2009.[62]
As global citizens become more aware of overfishing and the ecological destruction of the oceans, movements have sprung up to encourage abstinence[63]—not eating any seafood—or eating only "sustainable seafood".
Sustainable seafood is a movement that has gained momentum as more people become aware of overfishing andenvironmentally destructive fishing methods. Sustainable seafood is seafood from either fished or farmed sources that can maintain or increase production in the future without jeopardizing theecosystems from which it was acquired. In general, slow-growing fish that reproduce late in life, such as orange roughy, are vulnerable to overfishing. Seafood species that grow quickly and breed young, such as anchovies andsardines, are much more resistant to overfishing. Several organizations, including theMarine Stewardship Council (MSC), andFriend of the Sea, certify seafood fisheries as sustainable.[citation needed]
The Marine Stewardship Council has developed an environmental standard for sustainable and well-managed fisheries. Environmentally responsible fisheries management and practices are rewarded with the use of its blue productecolabel. Consumers concerned about overfishing and its consequences are increasingly able to choose seafood products that have been independently assessed against the MSC's environmental standard. This enables consumers to play a part in reversing the decline of fish stocks. As of February 2012, over 100 fisheries around the world have been independently assessed and certified as meeting the MSC standard. Theirwhere-to-buy page lists the currently available certified seafood. As of February 2012, over 13,000 MSC-labelled products are available in 74 countries around the world.Fish & Kids[usurped] is an MSC project to teach schoolchildren about marine environmental issues, including overfishing.
TheMonterey Bay Aquarium'sSeafood Watch Program, although not an official certifying body like the MSC, also provides guidance on the sustainability of certain fish species.[64] Some seafood restaurants have begun to offer more sustainable seafood options. TheSeafood Choices Alliance[65] is an organization whose members include chefs that serve sustainable seafood at their establishments. In the US, theSustainable Fisheries Act defines sustainable practices through national standards. Although there is no official certifying body like the MSC, theNational Oceanic and Atmospheric Administration has createdFishWatch to help guide concerned consumers to sustainable seafood choices.[66]
In September 2016, a partnership of Google andOceana andSkytruth introducedGlobal Fishing Watch, a website designed to assist citizens of the globe in monitoring fishing activities.[67][68][69]
The United Nations has included sustainable fishing and ending subsidies that contribute to overfishing as key targets for 2030 as part of theirSustainable Development Goal 14 called "Life Below Water".[70]
In open-access resources like fish stocks, in the absence of a system likeindividual transferable quotas, the impossibility of excluding others provokes the fishermen who want to increase catch to do so effectively by taking someone else' share, intensifying competition. Thistragedy of the commons provokes a capitalization process that leads them to increase their costs until they are equal to their revenue, dissipating their rent completely.[71] Causes of the fishing problem can be found in the property rights regime of fishing resources. Overexploitation and rent dissipation of fishermen arise in open-accessfisheries as was shown in Gordon.[72][73]
Thefishing industry has a strong financial incentive to oppose some measures aimed at improving the sustainability of fish stocks.[5] Recreational fisherman also have an interest in maintaining access to fish stocks. This leads to extensivelobbying that can block or weaken government policies intended to prevent overfishing.
There is always disagreement between fishermen and government scientists... Imagine an overfished area of the sea in the shape of a hockey field with nets at either end. The few fish left therein would gather around the goals because fishlike structured habitats. Scientists would survey the entire field, make lots of unsuccessful hauls, and conclude that it contains few fish. The fishermen would make a beeline to the goals, catch the fish around them, and say the scientists do not know what they are talking about. The subjective impression the fishermen get is always that there's lots of fish - because they only go to places that still have them... fisheries scientists survey and compare entire areas, not only the productive fishing spots. –Fisheries scientistDaniel Pauly[74]
Fish are highly transitory and many species will freely move through different jurisdictions. The conservation efforts of one country can then be exploited by another.[75] Tragedy of the commons can result inperverse incentives to increasefisheries subsidy.[71]
While governments can create regulations to control people's behaviors this can be undermined byillegal fishing activity. Estimates of the size of the illegal catch range from 11 to 26 million tonnes, which represents 14-33% of the world's reported catch.[76] Illegal fishing can take many forms. In some developing countries, large numbers of poor people are dependent on fishing. It can prove difficult to regulate this kind of overfishing, especially for weak governments. Even in regulated environments, illegal fishing may occur. While industrial fishing is often effectively controlled, smaller scale and recreational fishermen can often break regulations such asbag limits and seasonal closures. Fisherman can also easily fish illegally by doing things such as underreporting the amount of fish they caught or reporting that they caught one type of fish while actually catching another.[77] There is also a large problem with the surveillance of illegal fishing activity.[78] In 2001, the UNFood and Agriculture Organization (FAO), passed the International Plan of Action to Prevent, Deter and EliminateIllegal, Unreported and Unregulated Fishing (IPOA-IUU). This is an agreement with the intention to stopport states from allowing boats to dock that participated in illegal, unreported or unregulated fishing. It also gives details for port states on effective measures of inspecting and reporting illegal fishing.[79] Some illegal fishing takes place on an industrial scale.[80]
In waters that are the subject ofterritorial disputes, countries may actively encourage overfishing. A notable example is thecod wars where Britain used its navy to protect its trawlers fishing inIceland's exclusive economic zone.[81]
Outside of countries'exclusive economic zones, fishing is difficult to control. Large oceangoing fishing boats are free to exploit fish stocks at will.[82]China is claimed to operate the largest fishing fleet ininternational waters.[80]
This article incorporates text from afree content work. Licensed under CC BY 4.0 (license statement/permission). Text taken fromThe State of World Fisheries and Aquaculture 2024, FAO.
This article incorporates text from afree content work. Licensed under CC BY-SA 3.0 IGO (license statement/permission). Text taken fromIn brief, The State of World Fisheries and Aquaculture, 2018, FAO, FAO.
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