A sustainable fishery is one where fish are caught at a rate that keeps their population stable over time. This means fishing practices do not cause the number of fish to drop. Sustainability in fisheries uses both scientific knowledge, like how fish populations grow and change, and practical methods, such as setting limits on how much each fisher can catch. Other methods include stopping harmful or illegal fishing by supporting good laws and policies, creating protected areas where fishing is not allowed, helping fish populations that have been damaged return to health, considering how fishing affects the environment when making economic decisions, teaching people about the importance of sustainable fishing, and creating programs that check if fishing practices are safe.

Main concerns about sustainability include the risk that fishing too much, like catching too many young fish before they can reproduce or catching so many fish that their numbers drop too quickly, will reduce the total amount of fish that can be caught in the future. Another worry is that fish populations may lose their ability to adapt and survive changes in the environment. Ecosystems and the businesses that depend on them might go through cycles of failing and recovering, but each time they recover, they become less productive. Lastly, fishing can disrupt the balance of food chains in the ocean, leading to changes in how different sea creatures depend on each other.

Overview

Global wild fish populations are believed to have reached their highest point and are now starting to decrease. Important habitats, such as estuaries and coral reefs, are in poor condition. Farming fish that eat other fish, like salmon, does not fix the problem because these farmed fish are fed food made from wild fish, such as forage fish. Salmon farming also harms wild salmon populations. Fish that are higher up in the food chain are less effective at converting food energy into their own body energy.

A report from the High-level Political Forum on Sustainable Development in 2021 stated: "Sustainable fisheries made up about 0.1% of global GDP in 2017."

Defining sustainability

There are three main ways to define a sustainable fishery:

• Long-term constant yield refers to the idea that nature, when undisturbed, maintains a stable state that changes little over time. If fishing is done carefully, up to the highest level that nature can support, it allows ecosystems to adjust to a new balance without harming future harvests. However, this idea is not accurate because marine ecosystems naturally change over time, and their populations of fish often vary. These changes affect how much fish can be caught in the short and long term.

• Preserving intergenerational equity means recognizing that natural changes happen and that only practices that harm the genetic makeup of fish, destroy their habitats, or reduce their numbers so much that recovery takes longer than one generation are considered unsustainable. If rebuilding fish populations takes only one generation, overfishing may be economically unwise, but it is not necessarily unsustainable. This definition is widely accepted.

• Maintaining a biological, social, and economic system considers the health of both human and marine ecosystems. A fishery that switches between catching different species may reduce the numbers of some fish, but it can still be sustainable if the overall ecosystem remains healthy. This definition might include fishing practices that lead to the decline or extinction of certain species as sustainable.

Fisheries and aquaculture provide livelihoods for over 500 million people, mostly in developing countries.

Social sustainability can conflict with biodiversity. A fishery is socially sustainable if it continues to provide resources that society can use. Large changes in the types of fish in an ecosystem may be acceptable as long as the supply of useful products remains steady. Humans have used such systems for thousands of years, altering ecosystems and reducing or eliminating many species.

Sustainability is often difficult to describe but can be recognized when it is present.

According to Hilborn, the loss of some species and changes to ecosystems do not necessarily prevent sustainable fishing. For example, barndoor skates in the western Atlantic have been caught accidentally in fishing nets, leading to a sharp decline in their numbers. If these catches continue, the species may go extinct. Even if this happens, other commercially valuable species could still be fished sustainably.

Managing fisheries sustainably requires accepting that the long-term goals of fishing management must align with those of environmental conservation.

The focus of sustainable fishing often centers on fish, but other factors are also important when considering sustainability. Using non-renewable resources, such as diesel fuel for fishing boats, is not fully sustainable. There is even debate about the long-term sustainability of biofuels. Modern fishing nets are typically made from synthetic materials like nylon, and ropes are often made from nylon, polyester, polypropylene, or high-performance fibers such as ultra-high modulus polyethylene (HMPE) or aramid.

Energy and resources are used in processing, refrigeration, packaging, and transportation of fish. Life-cycle assessment methods help evaluate the sustainability of these processes and systems. These are part of the broader discussion about sustainability.

Obstacles

Overfishing can be sustainable. Hilborn explains that overfishing may mean societies are using resources in a way that is not efficient, but it does not always harm the environment or the long-term survival of fish populations.

Overfishing is usually described as catching so many fish that the number of fish caught becomes smaller than it would be if fishing were reduced. For example, Pacific salmon are often managed by determining how many spawning salmon, called "escapement," are needed each year to allow the greatest number of fish to be caught later. The best number of spawning fish to reach this goal is called the "optimum escapement." If the number of spawning fish is only half of this best number, fishing at this level might seem like overfishing. However, this level of fishing can still be sustainable, meaning it could continue without reducing the fish population too much. Many different numbers of spawning fish can be used without risking the fish population disappearing or losing its structure.

On the other hand, overfishing can lead to serious problems, such as a sharp drop in fish numbers or the collapse of a fishery. Hilborn notes that continuing to fish heavily when fish numbers are already decreasing, and when the fishery fails, is often the result of poor management or decision-making.

Today, more than 70% of fish species are either being fished to their full potential, overfished, already depleted, or recovering from being depleted. If overfishing continues, scientists predict that all fish species currently fished for commercial purposes may disappear by 2048.

A method called the Hubbert curve has been used to study the whaling industry and to track the price of caviar, which depends on sturgeon numbers. Another example is North Sea cod. Comparing fishing to the extraction of minerals shows that human activity is causing many natural resources to follow a similar pattern of use and decline.

Most of the world's continental shelves and large areas of underwater slopes, ridges, and seamounts have been repeatedly disturbed by heavy fishing tools like bottom trawls and dredges. For 50 years, governments and organizations, such as the Asian Development Bank, have supported the development of large fishing fleets. These fishing methods destroy the variety of life on the ocean floor and change the communities living there.

Since 1950, 90% of 25 species of large predator fish have disappeared.

Sources:
• "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.

Rising ocean temperatures and increased ocean acidification are changing marine ecosystems. Climate change is altering where fish live and how many fish are born and survive. This makes it harder to catch fish in a way that is sustainable, harms resources needed for farming fish, and affects communities that rely on fishing. It also weakens the ocean's ability to absorb carbon dioxide. Rising sea levels threaten coastal fishing communities, while changes in rainfall and water use affect inland fish and farming. As oceans warm, fish are moving toward cooler northern waters, which can cause overcrowding in those areas.

A recent study found that all parts of the ocean have been affected by human activity, and 41% of the ocean has been damaged by pollution, overfishing, and other harmful actions. Pollution is hard to fix because it comes from many different sources that are part of the systems we depend on for daily life.

The United Nations Environment Programme (UNEP) studied how problems like climate change, pollution, invasive species, and overuse of resources affect the ocean. The report found that at least 75% of the world's most important fishing areas may be harmed by these issues.

Large predator fish can have high levels of mercury, a harmful chemical that can harm a baby's development, memory, and mental focus, and cause shaking.

Lakes depend on water flowing into them from their surrounding area. In some places, heavy use of water for farming has reduced this flow, causing lakes to shrink. A famous example is the Aral Sea, once one of the world's largest lakes, which is now only about one-tenth of its original size.

Remediation

Fisheries management uses science to help people catch fish in a way that keeps fish populations healthy. Modern fisheries management includes rules that are based on clear goals and uses different methods to manage fish. These rules are watched over by systems that monitor and check fishing activities.

• Ideas and rules: Economist Paul Romer believes that sustainable growth happens when the right ideas (like new technology) are used with the right rules, not just by telling fishers what to do. Many ideas already exist for catching fish, but problems often happen because rules are not followed correctly.

• Fishing subsidies: Governments give money to help fishing, which affects fisheries worldwide. These subsidies let European and Asian fishing fleets travel to faraway places, like West Africa. Many experts say these subsidies should stop, and instead, rules should be changed to help struggling fisheries recover.

• Economics: Conservationists also focus on changing how fisheries are managed by improving how fish are sold. For example, some groups set limits on how much fish can be caught, like the Northwest Atlantic Fisheries Organization does. Other rules help protect fish populations.

• Using by-catch: By-catch is fish that are caught accidentally. Using these fish for other purposes, like making protein products or fish oil, can help reduce waste and protect the environment.

• Payment for Ecosystem Services: Environmental economist Essam Y Mohammed says giving people money for protecting the environment can help create sustainable fisheries. This can also encourage people to protect nature where they might not otherwise do so.

• Sustainable certification: Programs like those run by the Marine Stewardship Council help people choose seafood that is caught in a sustainable way. These programs teach consumers about where their seafood comes from.

• Ecosystem-based fisheries: See next section.

Rebuilding ecosystems, not just focusing on sustainability, should be the main goal of fishery management. Sustainability can be misleading because catching fish can change ecosystems over time, making them simpler and favoring smaller fish that survive better in disturbed areas.

Marine ecologist Chris Frid says the fishing industry often points to pollution and climate change as causes of falling fish numbers. Frid argues that overfishing also changes how ecosystems work.

Traditional fishery science focuses on one species at a time. In contrast, ecosystem-based approaches look at the whole environment. Some regions have already used this method. In 2007, scientists shared guidelines for ecosystem-based fisheries science to help clarify its goals.

Marine conservation strategies use both science, like population biology, and practical methods, such as creating protected areas. These areas, called Marine Protected Areas (MPAs) or Voluntary Marine Conservation Areas, are set up by each country. They often limit fishing and other threats to protect ecosystems.

Marine life is not spread evenly across the ocean. Many valuable ecosystems are in shallow coastal waters near the continental shelf, where sunlight and nutrients support life. In the 1970s, the U.S. expanded its control over ocean areas from 12 miles to 200 miles from its coast. Other countries followed, creating exclusive economic zones (EEZs). This change means most productive ocean areas are now under national control, allowing countries to create laws to protect them.

Marine ecologist Daniel Pauly says protected areas are important tools for conservation. Organizations like the Pew Charitable Trusts support efforts to create MPAs and protect the ocean.

Fish farming, or aquaculture, helps provide fish without overfishing the ocean. When done properly, it is environmentally friendly. Fish are raised in enclosed spaces, like underwater cages, and sold for food. Common farmed fish include salmon, cod, and halibut. Farmers control the environment, feed, and waste to protect the ocean and human health. However, feeding fish with animal waste is not sustainable.

International laws like the 1966 Convention on Fishing and Conservation of Living Resources help protect the ocean. In the U.S., laws like the Marine Mammal Protection Act and the Magnuson-Stevens Fishery Conservation and Management Act support marine conservation.

At a 2004 meeting, Daniel Pauly asked how fisheries science and conservation can work together. He said the answer is to respect both goals: keeping fishing as a viable job and protecting ecosystems.

A new idea is relationship farming, where farms help restore food chains in their area. This method can clean water and air, support local wildlife, and produce more food. One example is a type of farming that uses natural processes to improve the environment.

Data issues

A major problem in managing ocean resources is not having enough good information. According to fisheries scientist Milo Adkison (2007), the biggest challenge in making decisions about fish populations is the lack of accurate data. Fish management plans often use models to predict fish numbers, but these models only work well if the data used is reliable. Scientists and managers would benefit more from using simpler models and collecting better data.

Estimates show that illegal fishing causes losses worth between $10 billion and $23 billion each year. This equals between 11 and 26 million metric tons of fish.

Incidental catch refers to fish or other sea life caught unintentionally during fishing activities.

The term "shifting baselines" describes how changes in an ecosystem are measured against earlier baselines, which may themselves have already changed from the original state. This idea was first introduced by fisheries scientist Daniel Pauly in his paper "Anecdotes and the shifting baseline syndrome of fisheries." Pauly created the term to explain how scientists sometimes use incorrect starting points when studying fish populations. For example, they might compare current fish numbers to what was observed at the beginning of their careers, rather than to the original, untouched population levels. This can lead to missing the true long-term decline of fish species. Areas that once had large numbers of a certain species may have experienced a slow decrease over time, but scientists might use the population levels from decades ago as the standard for comparison. This makes it harder to notice major changes in ecosystems or species over time. When each generation assumes what was "normal" in the past, it becomes harder to recognize how much things have changed.

History

In the end, we will protect only what we care about; we will care only about what we learn; and we will learn only what is taught to us.

In 1883, Thomas Huxley spoke during an event in London about fishing. He claimed that overfishing could not cause fish populations to disappear forever, and he believed that large ocean fish populations were endless. However, by 1883, many ocean fish populations were already declining. The United States Fish Commission was created in 1871 to study why fish numbers in New England were dropping. By the time of Huxley’s speech, the Atlantic halibut fishery had already failed and has not recovered since.

Fisheries management and the science behind it were influenced by a limited focus on specific fish species and a lack of attention to how fishing affected entire ecosystems. This approach led to fewer fish and less variety of species. Historically, the fishing industry was seen as the only group with the right to use ocean resources. Scientists who studied fish populations often worked in government labs and focused on helping the fishing industry. These scientists ignored conservation concerns and avoided working with scientists who raised environmental issues. This occurred even as fish numbers declined and many governments had signed agreements to protect ocean life.