Fisheries management

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The goal of Fisheries management is to produce sustainable biological, social, and economic benefits from renewable aquatic resources. Fisheries are classified as renewable because the organisms of interest (e.g., fish, shellfish, reptiles, amphibians, and marine mammals) usually produce an annual biological surplus that with judicious management can be harvested without reducing future productivity. [1] Fisheries management employs activities that protect fishery resources so sustainable exploitation is possible, drawing on fisheries science and possibly including the precautionary principle. Modern fisheries management is often referred to as a governmental system of appropriate management rules based on defined objectives and a mix of management means to implement the rules, which are put in place by a system of monitoring control and surveillance. A popular approach is the ecosystem approach to fisheries management. [2] [3] According to the Food and Agriculture Organization of the United Nations (FAO), there are "no clear and generally accepted definitions of fisheries management". [4] However, the working definition used by the FAO and much cited elsewhere is:


The integrated process of information gathering, analysis, planning, consultation, decision-making, allocation of resources and formulation and implementation, with enforcement as necessary, of regulations or rules which govern fisheries activities in order to ensure the continued productivity of the resources and the accomplishment of other fisheries objectives. [4]


Fisheries have been explicitly managed in some places for hundreds of years. [5] More than 80 percent of the world's commercial exploitation of fish and shellfish are harvested from natural occurring populations in the oceans and freshwater areas. [6] For example, the Māori people, New Zealand residents for about 700 years, had prohibitions against taking more than what could be eaten and about giving back the first fish caught as an offering to sea god Tangaroa. [7] Starting in the 18th century attempts were made to regulate fishing in the North Norwegian fishery. This resulted in the enactment of a law in 1816 on the Lofoten fishery, which established in some measure what has come to be known as territorial use rights. [8]

"The fishing banks were divided into areas belonging to the nearest fishing base on land and further subdivided into fields where the boats were allowed to fish. The allocation of the fishing fields was in the hands of local governing committees, usually headed by the owner of the onshore facilities which the fishermen had to rent for accommodation and for drying the fish." [9]

In Europe, Governmental resource protection-based fisheries management is a relatively new idea, first developed for North European fisheries after the first Overfishing Conference held in London in 1936. In 1957 British fisheries researchers Ray Beverton and Sidney Holt published a seminal work on North Sea commercial fisheries dynamics. [10] In the 1960s the work became the theoretical platform for North European management schemes. In North America, both commercial and recreational fisheries have been actively managed for over 150 years. [11] All U.S. states and Canadian provinces have fisheries agencies and their employees implement state, provincial, and federal laws using a broad suite of tools and procedures for both freshwater and marine fisheries. [12] [13]

After some years away from the field of fisheries management, Beverton criticized his earlier work in a paper given at the first World Fisheries Congress in Athens in 1992. "The Dynamics of Exploited Fish Populations" expressed his concerns, including the way his and Sidney Holt's work had been misinterpreted and misused by fishery biologists and managers during the previous 30 years. [14] Nevertheless, the institutional foundation for modern fishery management had been laid.

In 1996, the Marine Stewardship Council was founded to set standards for sustainable fishing. In 2010, the Aquaculture Stewardship Council was created to do the same for aquaculture.

A report by Prince Charles' International Sustainability Unit, the New York-based Environmental Defense Fund and 50in10 published in July 2014 estimated global fisheries were adding $270 billion a year to global GDP, but by full implementation of sustainable fishing, that figure could rise by an extra amount of as much as $50 billion. [15]

Political objectives

According to the FAO, fisheries management should be based explicitly on political objectives, ideally with transparent priorities. [16] Political goals can also be a weak part of fisheries management, since the objectives can conflict with each other. [17] Typical political objectives when exploiting a fish resource are to: [17]

For the most recent several decades, the political goals in fisheries management have been rapidly evolving, primarily driven by (1) a recognition of the response of fish and other target animals to changing climate, (2) new technologies for fishing particularly on the high seas, (3) development of competing policy priorities for aquatic environments leading to a more ecosystem-based approach to fisheries management, and (4) new scientific insights about the processes affecting fish population size and recruitment. [18]

International objectives

Fisheries objectives need to be expressed in concrete management rules. In most countries fisheries management rules should be based on the internationally agreed, though non-binding, Code of Conduct for Responsible Fisheries, [19] agreed at a meeting of the U.N.'s Food and Agriculture Organization FAO session in 1995. The precautionary approach it prescribes is typically implemented in concrete management rules as minimum spawning biomass, maximum fishing mortality rates, etc. In 2005 the UBC Fisheries Centre at the University of British Columbia comprehensively reviewed the performance of the world's major fishing nations against the Code. [20]

International agreements are required in order to regulate fisheries in international waters. The desire for agreement on this and other maritime issues led to three conferences on the Law of the Sea, and ultimately to the treaty known as the United Nations Convention on the Law of the Sea (UNCLOS). Concepts such as exclusive economic zones (EEZ, extending 200 nautical miles (370 km) from a nation's coasts) allocate certain sovereign rights and responsibilities for resource management to individual countries.

Other situations need additional intergovernmental coordination. For example, in the Mediterranean Sea and other relatively narrow bodies of water, EEZ of 200 nautical miles (370 km) are irrelevant. International waters beyond 12-nautical-mile (22 km) from shore require explicit agreements.

Straddling fish stocks, which migrate through more than one EEZ also present challenges. Here sovereign responsibility must be agreed with neighbouring coastal states and fishing entities. Usually this is done through the medium of a regional organisation set up for the purpose of coordinating the management of that stock.

UNCLOS does not prescribe precisely how fisheries confined only to international waters should be managed. Several new fisheries (such as high seas bottom trawling fisheries) are not (yet) subject to international agreement across their entire range. In November 2004 the UN General Assembly issued a resolution on Fisheries that prepared for further development of international fisheries management law.

Management mechanisms

Many countries have set up Ministries/Government Departments, named "Ministry of Fisheries" or similar, controlling aspects of fisheries within their exclusive economic zones. Four categories of management means have been devised, regulating either input/investment, or output, and operating either directly or indirectly:

IndirectVessel licensingCatching techniques
DirectLimited entry Catch quota and technical regulation

Technical means may include:

Catch quotas

Systems that use individual transferable quotas (ITQ), also called individual fishing quota limit the total catch and allocate shares of that quota among the fishers who work that fishery. Fishers can buy/sell/trade shares as they choose.

A large scale study in 2008 provided strong evidence that ITQ's can help to prevent fishery collapse and even restore fisheries that appear to be in decline. [22] [23] [24] [25] Other studies have shown negative socio-economic consequences of ITQs, especially on small-sclale fisheries. [26] These consequences include concentration of quota in that hands of few fishers; increased number of inactive fishers leasing their quotas to others (a phenomenon known as armchair fishermen); and detrimental effects on coastal communities. [27]

Precautionary principle

A Fishery Manager's Guidebook issued in 2002 by the FAO advises that a set of working principles should be applied to "highlight the underlying key issues" of fisheries management." [16] :130 [28] There are 8 principles that should be considered as a whole in order to best manage a fishery. The first principle focuses on the finite nature of fish stocks and how potential yields must be estimated based on the biological constraints of the population.

In a paper published in 2007, Shertzer and Prager suggested that there can be significant benefits to stock biomass and fishery yield if management is stricter and more prompt. [29] This is supported by recent work on the management of North Sea fisheries in accordance with ranges of acceptable fishing, where fishing at the top of the "acceptable" ranges is many times more risky than fishing near the bottom, but delivers only 20% more yield. [30]

Fisheries law

Fisheries law is an emerging and specialized area of law which includes the study and analysis of different fisheries management approaches, including seafood safety regulations and aquaculture regulations. Despite its importance, this area is rarely taught at law schools around the world, which leaves a vacuum of advocacy and research.

Fisheries legislation on a national level differs greatly between countries [16] :130 [28] Fisheries may also me managed on an international level. One the first laws enacted was the "United Nations Convention on the Law of the Sea of 10 December 1982 (LOS Convention)", which entered into force in 1994. [16] :130 [28] This law set the foundation for all international agreements related to oceans that followed.

Climate change

In the past, changing climate has affected inland and offshore fisheries and such changes are likely to continue. [31] From a fisheries perspective, the specific driving factors of climate change include rising water temperature, alterations in the hydrologic cycle, changes in nutrient fluxes, and relocation of spawning and nursery habitat. Further, changes in such factors would affect resources at all levels of biological organization, including the genetic, organism, population, and ecosystem levels. [32] Understanding how these factors affect fisheries at a more nuanced level stand as challenges that fish biologists, across multiple fields, still need to face. [33]

Population dynamics

Population dynamics describes the growth and decline of a given fishery stock over time, as controlled by birth, death and migration. It is the basis for understanding changing fishery patterns and issues such as habitat destruction, predation and optimal harvesting rates. The population dynamics of fisheries has been traditionally used by fisheries scientists to determine sustainable yields. [34] [35]

The basic accounting relation for population dynamics is the BIDE model: [36]

N1 = N0 + BD + IE

where N1 is the number of individuals at time 1, N0 is the number of individuals at time 0, B is the number of individuals born, D the number that died, I the number that immigrated, and E the number that emigrated between time 0 and time 1. While immigration and emigration can be present in wild fisheries, they are usually not measured.

Care is needed when applying population dynamics to real world fisheries. In the past, over-simplistic modelling, such as ignoring the size, age and reproductive status of the fish, focusing solely on a single species, ignoring bycatch and physical damage to the ecosystem, has accelerated the collapse of key stocks. [37] [38]

Ecosystem based fisheries

We propose that rebuilding ecosystems, and not sustainability per se, should be the goal of fishery management. Sustainability is a deceptive goal because human harvesting of fish leads to a progressive simplification of ecosystems in favour of smaller, high turnover, lower trophic level fish species that are adapted to withstand disturbance and habitat degradation.

According to marine ecologist Chris Frid, the fishing industry points to pollution and global warming as the causes of unprecedentedly low fish stocks in recent years, writing, "Everybody would like to see the rebuilding of fish stocks and this can only be achieved if we understand all of the influences, human and natural, on fish dynamics." Overfishing has also had an effect. Frid adds, “Fish communities can be altered in a number of ways, for example they can decrease if particular sized individuals of a species are targeted, as this affects predator and prey dynamics. Fishing, however, is not the sole perpetrator of changes to marine life - pollution is another example [...] No one factor operates in isolation and components of the ecosystem respond differently to each individual factor." [40]

In contrast to the traditional approach of focusing on a single species, the ecosystem-based approach is organized in terms of ecosystem services. Ecosystem-based fishery concepts have been implemented in some regions. [41] In 2007 a group of scientists offered the following "ten commandments": [42]

* Keep a perspective that is holistic, risk-averse and adaptive.

Elderly maternal fish

Old, fat, female rockfish are the best producers. Sebastes mystinus 2.jpg
Old, fat, female rockfish are the best producers.

Traditional management practices aim to reduce the number of old, slow-growing fish, leaving more room and resources for younger, faster-growing fish. Most marine fish produce huge numbers of eggs. The assumption was that younger spawners would produce plenty of viable larvae. [43]

However, 2005 research on rockfish shows that large, elderly females are far more important than younger fish in maintaining productive fisheries. The larvae produced by these older maternal fish grow faster, survive starvation better, and are much more likely to survive than the offspring of younger fish. Failure to account for the role of older fish may help explain recent collapses of some major US West Coast fisheries. Recovery of some stocks is expected to take decades. One way to prevent such collapses is to establish marine reserves, where fishing is not allowed and fish populations age naturally. [43]

Data quality

According to fisheries scientist Milo Adkison, the primary limitation in fisheries management decisions is the absence of quality data. Fisheries management decisions are often based on population models, but the models need quality data to be effective. He asserts that scientists and fishery managers would be better served with simpler models and improved data. [44]

The most reliable source for summary statistics is the FAO Fisheries Department. [45]


Ecopath, with Ecosim (EwE), is an ecosystem modelling software suite. It was initially a NOAA initiative led by Jeffrey Polovina, later primarily developed at the UBC Fisheries Centre of the University of British Columbia. In 2007, it was named as one of the ten biggest scientific breakthroughs in NOAA's 200-year history. The citation states that Ecopath "revolutionized scientists’ ability worldwide to understand complex marine ecosystems". Behind this lies two decades of development work by Villy Christensen, Carl Walters, Daniel Pauly, and other fisheries scientists. As of 2010 there are 6000 registered users in 155 countries. Ecopath is widely used in fisheries management as a tool for modelling and visualising the complex relationships that exist in real world marine ecosystems.

Human factors

Managing fisheries is about managing people and businesses, and not about managing fish. Fish populations are managed by regulating the actions of people. [46] If fisheries management is to be successful, then associated human factors, such as the reactions of fishermen, are of key importance, and need to be understood. [47]

Management regulations must also consider the implications for stakeholders. Commercial fishermen rely on catches to provide for their families just as farmers rely on crops. Commercial fishing can be a traditional trade passed down from generation to generation. Most commercial fishing is based in towns built around the fishing industry; regulation changes can impact an entire town's economy. Cuts in harvest quotas can have adverse effects on the ability of fishermen to compete with the tourism industry. [48]

Effective management of fisheries includes involving all stakeholders in the fishery. To do this successfully, stakeholders need to feel empowered enough to make meaningful contributions to the management process. [49]

Empowerment has a wide application but in this context it refers to a tool that gives people within the fishing communities an opportunity to shape their own future in order to cope with the impacts from large-scale commercial fishing, competition of resources, and other threats that impact fishing communities. [50]

However, there are limits to empowerment in the fisheries management process. Empowerment maintains an involvement on the part of the state in fisheries management and no matter how empowered the other stakeholders are, the success of fisheries isn't possible without the legislative powers, financial resources, educational support, and research the government provides. [50]

This concept is not accepted by all, as some communities and individuals argue that the state should withdraw completely and let the local communities handle their own fishery management based on cultural traditions and established practices. [50] Additionally, others have argued that co-management only empowers the wealthy and powerful which in turn solidifies and validates the already existing inequalities of fisheries management. [50]

Empowerment working as a function of co-management, carried out correctly, will not only enable but it will authorize individuals and communities to make meaningful contributions to fisheries management. It is a mechanism that works in a loop, where an individual gains empowerment and encouragement from being a part of the group and the collective action is only successful because of its empowered individuals. [49] In order to effectively and successfully use empowerment as co-management, it is imperative that study programs, guidelines, reading materials, manuals, and checklists are developed and incorporated into all fisheries management.


The biomass of certain global fish stocks have been allowed to run down. The biomass of many species have now diminished to the point where it is no longer possible to sustainably catch the amount of fish that could be caught. According to a 2008 UN report, titled The Sunken Billions: The Economic Justification for Fisheries Reform , the world's fishing fleets incur a "$US 50 billion annual economic loss" through depleted stocks and poor fisheries management. The report, produced jointly by the World Bank and the UN Food and Agriculture Organization (FAO), asserts that half the world's fishing fleet could be scrapped with no change in catch.

"By improving governance of marine fisheries, society could capture a substantial part of this $50 billion annual economic loss. Through comprehensive reform, the fisheries sector could become a basis for economic growth and the creation of alternative livelihoods in many countries. At the same time, a nation’s natural capital in the form of fish stocks could be greatly increased and the negative impacts of the fisheries on the marine environment reduced." [51]

The most prominent failure of fisheries management in recent times has perhaps been the events that lead to the collapse of the northern cod fisheries. More recently, the International Consortium of Investigative Journalists produced a series of journalistic investigations called Looting the seas . These detail investigations into the black market for bluefin tuna, the subsidies propping up the Spanish fishing industry, and the overfishing of the Chilean jack mackerel. [52]

See also


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  3. 1 2 FAO (1997) Fisheries Management Section 1.2, Technical Guidelines for Responsible Fisheries. FAO, Rome. ISBN   92-5-103962-3
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  5. Meredith P (2009) Te hī ika – Māori fishing - Traditional practices Te Ara - the Encyclopedia of New Zealand. Updated 2 March 2009. Retrieved 22 February 2011.
  6. Christy FT (1983) Territorial Use Rights in Fisheries: Definitions and Conditions FAO Fisheries, Technical Paper No. 227, Rome. ISBN   978-92-5-101269-7.
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  10. Hubert, Wayne A. (2010). Inland Fisheries Management in North America. Bethesda, MD: American Fisheries Society. ISBN   978-1-934874-16-5.
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  28. Thorpe, Robert B.; Jennings, Simon; Dolder, Paul J.; Zhou, Shijie (September 2017). "Risks and benefits of catching pretty good yield in multispecies mixed fisheries". ICES Journal of Marine Science. 74 (8): 2097–2106. doi:10.1093/icesjms/fsx062.
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  31. Jacobs, A.; Doran, C.; Murray, D. S.; Duffill Telsnig, J.; Laskowski, K. L.; Jones, N. A. R.; Auer, S. K.; Praebel, K. (March 2018). "On the challenges and opportunities facing fish biology: a discussion of five key knowledge gaps" (PDF). Journal of Fish Biology. 92 (3): 690–698. doi:10.1111/jfb.13545. PMID   29537088.
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Related Research Articles

Fishery entity engaged in raising or harvesting fish which is determined by some authority to be a fishery

Generally a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, "...a fishery is an activity leading to harvesting of fish. It may involve capture of wild fish or raising of fish through aquaculture." It is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats, purpose of the activities or a combination of the foregoing features". The definition often includes a combination of fish and fishers in a region, the latter fishing for similar species with similar gear types. Some government and private organizations, especially those focusing on recreational fishing include in their definitions not only the fishers, but the fish and habitats upon which the fish depend.

In population ecology and economics, maximum sustainable yield (MSY) is theoretically, the largest yield that can be taken from a species' stock over an indefinite period. Fundamental to the notion of sustainable harvest, the concept of MSY aims to maintain the population size at the point of maximum growth rate by harvesting the individuals that would normally be added to the population, allowing the population to continue to be productive indefinitely. Under the assumption of logistic growth, resource limitation does not constrain individuals' reproductive rates when populations are small, but because there are few individuals, the overall yield is small. At intermediate population densities, also represented by half the carrying capacity, individuals are able to breed to their maximum rate. At this point, called the maximum sustainable yield, there is a surplus of individuals that can be harvested because growth of the population is at its maximum point due to the large number of reproducing individuals. Above this point, density dependent factors increasingly limit breeding until the population reaches carrying capacity. At this point, there are no surplus individuals to be harvested and yield drops to zero. The maximum sustainable yield is usually higher than the optimum sustainable yield and maximum economic yield.

Overfishing the act whereby fish stocks are depleted to unacceptable levels, regardless of water body size

Overfishing is the removal of a species of fish from a body of water at a rate that the species cannot replenish, resulting in those species becoming underpopulated in that area. In a Food and Agriculture Organization of the United Nations 2018 report, the FAO estimates that one-third of world fish stocks were overfished by 2015. Over 30 billion euros in public subsidies are directed to fisheries annually.

Sustainable fishery fishing practices intended not to cause the fish population to decline over time

A conventional idea of a sustainable fishery is that it is one that is harvested at a sustainable rate, where the fish population does not decline over time because of fishing practices. Sustainability in fisheries combines theoretical disciplines, such as the population dynamics of fisheries, with practical strategies, such as avoiding overfishing through techniques such as individual fishing quotas, curtailing destructive and illegal fishing practices by lobbying for appropriate law and policy, setting up protected areas, restoring collapsed fisheries, incorporating all externalities involved in harvesting marine ecosystems into fishery economics, educating stakeholders and the wider public, and developing independent certification programs.

Fisheries science The academic discipline of managing and understanding fisheries

Fisheries science is the academic discipline of managing and understanding fisheries. It is a multidisciplinary science, which draws on the disciplines of limnology, oceanography, freshwater biology, marine biology, meteorology, conservation, ecology, population dynamics, economics, statistics, decision analysis, management, and many others in an attempt to provide an integrated picture of fisheries. In some cases new disciplines have emerged, as in the case of bioeconomics and fisheries law. Because fisheries science is such an all-encompassing field, fisheries scientists often use methods from a broad array of academic disciplines. Over the most recent several decades, there has been declines in fish stocks (populations) in many regions along with increasing concern about the impact of intensive fishing on marine and freshwater biodiversity.

Fish stock

Fish stocks are subpopulations of a particular species of fish, for which intrinsic parameters are traditionally regarded as the significant factors determining the stock's population dynamics, while extrinsic factors are traditionally ignored.

Unsustainable fishing methods

Unsustainable fishing methods refers to the utilization of the various fishing methods in order to capture or harvest fish, at a rate which sees the declining of fish populations over time. These methods are observed to facilitate the destructive fishing practices that destroy ecosystems within the ocean, and is used as a tool for over-fishing which results in the depletion of fish populations at a rate that cannot be sustained.

Individual fishing quotas (IFQs) also known as "individual transferable quotas" (ITQs) are one kind of catch share, a means by which many governments regulate fishing. The regulator sets a species-specific total allowable catch (TAC), typically by weight and for a given time period. A dedicated portion of the TAC, called quota shares, is then allocated to individuals. Quotas can typically be bought, sold and leased, a feature called transferability. As of 2008, 148 major fisheries around the world had adopted some variant of this approach, along with approximately 100 smaller fisheries in individual countries. Approximately 10% of the marine harvest was managed by ITQs as of 2008. The first countries to adopt individual fishing quotas were the Netherlands, Iceland and Canada in the late 1970s, and the most recent is the United States Scallop General Category IFQ Program in 2010. The first country to adopt individual transferable quotas as a national policy was New Zealand in 1986.

Environmental impact of fishing

The environmental impact of fishing includes issues such as the availability of fish, overfishing, fisheries, and fisheries management; as well as the impact of industrial fishing on other elements of the environment, such as by-catch. These issues are part of marine conservation, and are addressed in fisheries science programs. According to a 2019 FAO report, global production of fish, crustaceans, molluscs and other aquatic animals has continued to grow and reached 172.6 million tonnes in 2017, with an increase of 4.1 percent compared with 2016. There is a growing gap between the supply of fish and demand, due in part to world population growth.

Discards Wikimedia disambiguation page

Discards are the portion of a catch of fish which is not retained on board during commercial fishing operations and is returned, often dead or dying, to the sea. The practice of discarding is driven by economic and political factors; fish which are discarded are often unmarketable species, individuals which are below minimum landing sizes and catches of species which fishermen are not allowed to land, for instance due to quota restrictions. Discards form part of the bycatch of a fishing operation, although bycatch includes marketable species caught unintentionally. Discarding can be highly variable in time and space as a consequence of changing economic, sociological, environmental and biological factors.

The sustainable yield of natural capital is the ecological yield that can be extracted without reducing the base of capital itself, i.e. the surplus required to maintain ecosystem services at the same or increasing level over time. This yield usually varies over time with the needs of the ecosystem to maintain itself, e.g. a forest that has recently suffered a blight or flooding or fire will require more of its own ecological yield to sustain and re-establish a mature forest. While doing so, the sustainable yield may be much less.

Population dynamics of fisheries

A fishery is an area with an associated fish or aquatic population which is harvested for its commercial or recreational value. Fisheries can be wild or farmed. Population dynamics describes the ways in which a given population grows and shrinks over time, as controlled by birth, death, and migration. It is the basis for understanding changing fishery patterns and issues such as habitat destruction, predation and optimal harvesting rates. The population dynamics of fisheries is used by fisheries scientists to determine sustainable yields.

This is a glossary of terms used in fisheries, fisheries management and fisheries science.

Ray Hilborn Canadian marine biologist and fisheries scientist

Ray Hilborn is a marine biologist and fisheries scientist, known for his work on conservation and natural resource management in the context of fisheries. He is currently professor of aquatic and fishery science at the University of Washington. He focuses on conservation, natural resource management, fisheries stock assessment and risk analysis, and advises several international fisheries commissions and agencies.

Catch share is a fishery management system that allocates a secure privilege to harvest a specific area or percentage of a fishery's total catch to individuals, communities, or associations. Examples of catch shares are individual transferable quota (ITQs), individual fishing quota (IFQs), territorial use rights for fishing (TURFs), limited access privileges (LAPs), sectors, and dedicated access privileges (DAPs).

Overexploitation Depleting a renewable resource

Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource. The term applies to natural resources such as: wild medicinal plants, grazing pastures, game animals, fish stocks, forests, and water aquifers.

Fisheries and climate change

The full relationship between fisheries and climate change is difficult to explore due to the context of each fishery and the many pathways that climate change affects. However, there is strong global evidence for these effects. Rising ocean temperatures and ocean acidification are radically altering marine aquatic ecosystems, while freshwater ecosystems are being impacted by changes in water temperature, water flow, and fish habitat loss. Climate change is modifying fish distribution and the productivity of marine and freshwater species.

Fishing down the food web

Fishing down the food web is the process whereby fisheries in a given ecosystem, "having depleted the large predatory fish on top of the food web, turn to increasingly smaller species, finally ending up with previously spurned small fish and invertebrates".

Sidney J. Holt was a British biologist who was a founder of fisheries science. He was best known for the book On the Dynamics of Exploited Fish Populations which he published with Ray Beverton in 1957. The book is a cornerstone of modern fisheries science and remains much used today. Holt served with the FAO in 1953 and with other UN agencies for another 25 years. After his retirement in 1979, Holt remained active in work related to the International Whaling Commission and conservation of whales in general, also publishing his views about whaling and fisheries management in academic journals.

The following outline is provided as an overview of and topical guide to fisheries: