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.
Some primary concerns around sustainability are that heavy fishing pressures, such as overexploitation and growth or recruitment overfishing, will result in the loss of significant potential yield; that stock structure will erode to the point where it loses diversity and resilience to environmental fluctuations; that ecosystems and their economic infrastructures will cycle between collapse and recovery; with each cycle less productive than its predecessor; and that changes will occur in the trophic balance (fishing down marine food webs).Hilborn, Ray (2005) "Are Sustainable Fisheries Achievable?" Chapter 15, pp. 247–259, in Norse and Crowder (2005).
Overview
Global wild fisheries are believed to have peaked and begun a decline, with valuable habitats, such as estuaries and coral reefs, in critical condition.Tietenberg, Tom (2006) Environmental and Natural Resource Economics: A Contemporary Approach. Page 28. Pearson/Addison Wesley. Current aquaculture or farming of piscivorous fish, such as salmon, does not solve the problem because farmed piscivores are fed products from wild fish, such as forage fish. Salmon farming also has major negative impacts on wild salmon.Knapp G, Roheim CA and Anderson JL (2007) = The+Great+Salmon+Run&col=&n=4 The Great Salmon Run: Competition Between Wild And Farmed Salmon World Wildlife Fund. Washington Post. Salmon Farming May Doom Wild Populations, Study Says . Fish that occupy the higher trophic levels are less efficient sources of food energy.
A report at the High-level Political Forum on Sustainable Development in 2021 stated that: "Sustainable fisheries accounted for approximately 0.1 per cent of global GDP in 2017".United Nations Economic and Social Council (2021) Progress towards the Sustainable Development Goals Report of the Secretary-General, E/2021/58, High-level political forum on sustainable development.
History In his 1883 inaugural address to the International Fisheries Exhibition in London, Thomas Huxley asserted that overfishing or "permanent exhaustion" was scientifically impossible, and stated that probably "all the great sea fisheries are inexhaustible".Huxley, Thomas (1883)Inaugural Address Fisheries Exhibition, London. In reality, by 1883 marine fisheries were already collapsing. The United States Fish Commission was established 12 years earlier for the purpose of finding why fisheries in New England were declining. At the time of Huxley's address, the Atlantic halibut fishery had already collapsed (and has never recovered).Goode GB and Collins JW (1887) "The fresh-halibut fishery". In: The fisheries and fishery industry of the United States. Section V. History and methods of the fisheries, Vol. I, Part I. Government Printing Office, Washington, DC. p. 3–89.
Traditional management of fisheries Traditionally, fisheries management and the science underpinning it was distorted by its "narrow focus on target populations and the corresponding failure to account for ecosystem effects leading to declines of species abundance and diversity" and by perceiving the fishing industry as "the sole legitimate user, in effect the owner, of marine living resources." Historically, stock assessment scientists usually worked in government laboratories and considered their work to be providing services to the fishing industry. These scientists dismissed conservation issues and distanced themselves from the scientists and the science that raised the issues. This happened even as commercial fish stocks deteriorated, and even though many governments were signatories to binding conservation agreements.Preikshot, Dave and Pauly, Daniel (2005) "Global Fisheries and Marine Conservation: Is Coexistence Possible?" Chapter 11, pp. 185–197, in Norse and Crowder (2005).
Defining sustainability
Three ways of defining a sustainable fishery exist: Long term constant yield is the idea that undisturbed nature establishes a steady state that changes little over time. Properly done, fishing at up to maximum sustainable yield allows nature to adjust to a new steady state, without compromising future harvests. However, this view is naive, because constancy is not an attribute of marine ecosystems, which dooms this approach. Stock abundance fluctuates naturally, changing the potential yield over short and long-term periods. Preserving intergenerational equity acknowledges natural fluctuations and regards as unsustainable only practices which damage the genetic structure, destroy habitat, or deplete stock levels to the point where rebuilding requires more than a single generation. Providing rebuilding takes only one generation, overfishing may be economically foolish, but it is not unsustainable. This definition is widely accepted. Maintaining a biological, social and economic system considers the health of the human ecosystem as well as the marine ecosystem. A fishery which rotates among multiple species can deplete individual stocks and still be sustainable so long as the ecosystem retains its intrinsic integrity. Such a definition might consider as sustainable fishing practices that lead to the reduction and possible extinction of some species.
Social sustainability Fisheries and aquaculture are, directly or indirectly, a source of livelihood for over 500 million people, mostly in developing countries.Fisheries and Aquaculture in our Changing Climate Policy brief of the FAO for the UNFCCC COP-15 in Copenhagen, December 2009.
Social sustainability can conflict with biodiversity. A fishery is socially sustainable if the fishery ecosystem maintains the ability to deliver products the society can use. Major species shifts within the ecosystem could be acceptable as long as the flow of such products continues. Humans have been operating such regimes for thousands of years, transforming many ecosystems, depleting or driving to extinction many species.Johannes R (1981) Words of the lagoon: Fishing and Marine Lore in the Palau District of Micronesia, University of California Press.
According to Hilborn, the "loss of some species, and indeed transformation of the ecosystem is not incompatible with sustainable harvests." For example, in recent years, barndoor skates have been caught as bycatch in the western Atlantic. Their numbers have severely declined and they will probably go extinct if these catch rates continue. Even if the barndoor skate goes extinct, changing the ecosystem, there could still be sustainable fishing of other commercial species.
Environmental sustainability The focus of sustainable fishing is often on the fish. Other factors are sometimes included in the broader question of sustainability. The use of non-renewable resources is not fully sustainable. This might include diesel fuel for the fishing ships and boats: there is even a debate about the long term sustainability of biofuels. Modern fishing nets are usually made of artificial polyamides like nylon. Synthetic braided ropes are generally made from nylon, polyester, polypropylene or high performance fibers such as ultra high modulus polyethylene (HMPE) and aramid.
Energy and resources are employed in fish processing, refrigeration, packaging, logistics, etc. The methodologies of life-cycle assessment are useful to evaluate the sustainability of components and systems. These are part of the broad question of sustainability.
Obstacles
Overfishing
Overfishing is traditionally defined as harvesting so many fish that the yield is less than it would be if fishing were reduced. For example, Pacific salmon are usually managed by trying to determine how many spawning salmon, called the "escapement", are needed each generation to produce the maximum harvestable surplus. The optimum escapement is that needed to reach that surplus. If the escapement is half the optimum, then normal fishing looks like overfishing. But this is still sustainable fishing, which could continue indefinitely at its reduced stock numbers and yield. There is a wide range of escapement sizes that present no threat that the stock might collapse or that the stock structure might erode. According to Hilborn, overfishing can be "a misallocation of societies' resources", but it does not necessarily threaten conservation or sustainability".
On the other hand, overfishing can precede severe stock depletion and fishery collapse. Hilborn points out that continuing to exert fishing pressure while production decreases, stock collapses and the fishery fails, is largely "the product of institutional failure". Today over 70% of fish species are either fully exploited, overexploited, depleted, or recovering from depletion. If overfishing does not decrease, it is predicted that stocks of all species currently commercially fished for will collapse by 2048.
A Hubbert linearization (Hubbert curve) has been applied to the whaling industry, as well as charting the price of caviar, which depends on sturgeon stocks. Another example is North Sea cod. Comparing fisheries and mineral extraction tells us that human pressure on the environment is causing a wide range of resources to go through a Hubbert depletion cycle.
Habitat modification
Nearly all the world's continental shelves, and large areas of continental slopes, underwater ridges, and seamounts, have had heavy bottom trawls and dredges repeatedly dragged over their surfaces. For fifty years, governments and organizations, such as the Asian Development Bank, have encouraged the fishing industry to develop trawler fleets. Repeated bottom trawling and dredging literally flattens diversity in the benthic habitat, radically changing the associated communities.Watling, Les (2005) "The global destruction of bottom habitats by mobile fishing gear" Chapter 12, pp. 198–210, in Norse and Crowder (2005).
Habitat loss also extends to coastal vegetation. Mangrove forests act as breeding and nursery grounds that support larger numbers of fish, crustaceans and shellfish, which many small-scale fisheries depend on for food and income. More than four million people fish in mangroves worldwide, and the forests are an important source of food security in many countries. Since the 2000s, however, these forests have shrunk by about 0.5 percent a year, and that loss reduces the habitat the fisheries rely on. Since 1950 up until 2009, 90 percent of 25 species of big predator fish have gone.How we are emptying our seas, The Sunday Times, May 10, 2009.Pauly, Daniel (2004) Reconciling Fisheries with Conservation: the Challenge of Managing Aquatic Ecosystems Fourth World Fisheries Congress, Vancouver, 2004.
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