Overfishing 101: Everything You Need to Know

Quick Key Facts

1. Overfishing is the removal of fish from their aquatic habitat at a rate faster than they can reproduce. This diminishes their populations and has cascading effects down the food chain, greatly impacting the trophic structures of ecosystems. 
2. Wild-capture fisheries harvested 96.4 million tons of fish in 2018. No other industry in the world removes so many wild animals from their habitat. 
3. Large-scale commercial fishing often entails harmful, exploitative practices — like bottom-trawling and blast fishing — that cause damage to coral reefs and other marine habitats.
4. Non-target marine species — including sea lions, sharks, turtles, and seabirds — are often mistakenly caught as “bycatch” in trawling nets or longlines, and are severely injured or killed in the process. 
5. The fishing industry provides income for 10-12% of the global population, and fish are an important source of protein for 3 billion people. A decline in fish stocks could result in economic instability and a hunger crisis for these communities. 
6. Government subsidies for commercial fishing have long incentivized the fishing of overexploited fish stocks. 

What Is Overfishing?

Overfishing occurs when fish are caught faster than their populations can reproduce and replenish themselves, and it’s among the greatest threats to our oceans. According to the Food and Agriculture Organization of the United Nations, one-third of assessed fisheries worldwide are pushed beyond their biological limits, which has severe environmental and social consequences. 

While overfishing can occur in any aqueous habitat — oceans, lakes, ponds, rivers, and wetlands alike — it is especially associated with commercial fishing in marine waters, whereby massive numbers of fish are caught at once. Some trawl nets used in ocean fishing are so big, they can hold up to 13 jumbo jets. Today, nearly 90% of marine fish stocks (a stock being defined as a group of the same species that lives in the same geographic area) globally are either overfished or exploited. 

The History of Overfishing 

Fishing itself has happened throughout recorded history, but deep-sea, commercial fishing didn’t arise until the 15th century, and became more commercial in the 19th century with the arrival of steamboats. Around that time, humans began destroying whale populations as they fished them in huge numbers for their blubber to make oil. 

In the 1950s, this type of intensive fishing ceased to be an industry that characterized only a few areas, but extended to the vast majority of fisheries. The 1970s brought the first major signs of overfishing and became clearer in the 1990s when populations of open sea fish started falling dramatically, and Atlantic cod, herring, and California sardines were fished almost to extinction. Canada’s Grand Banks cod fishery collapsed in 1992, leading to massive layoffs in coastal communities and exposing the immediate threat of overfishing. 

Overfishing vs. Illegal and Destructive Fishing 

The term “overfishing” refers specifically to fishing beyond sustainable levels, although illegal and destructive fishing often play a role in population depletion. 

Illegal Fishing 

It’s important to note that overfishing is not the same as illegal fishing. Overfishing is often not illegal, and occurs when there are inadequate catch limits, a lack of standards set by governments, or other management issues. Illegal fishing, on the other hand, entails fishing without a license, with illegal gear, in closed areas, over a set quota, or of prohibited species. It’s often called IUU fishing (Illegal, Unreported and Unregulated), and breaks either regional or international laws. Illegal fishing operations are estimated to be worth about $10-23.5 billion annually, according to the Marine Stewardship Council, although much of this activity goes unreported. Total catches in West Africa, for example, are purported to be about 40% more than what is reported. Illegal operations often do not adhere to sustainability standards, and thus cause damage to fish populations and marine ecosystems. 

Destructive Fishing 

Destructive fishing is also a separate kind of harmful fishing. The term refers to practices that are harmful to fish populations and their habitats based on certain highly destructive methods, like the use of cyanide or explosives. Blast fishing, for one, uses explosives to stun the fish and raise them to the surface of the water, destroying entire sections of coral reefs and other ecosystems in the process. Cyanide fishing — which is practiced widely in Southeast Asia — uses the chemical to stun coral reef fish in order for fishers to capture them alive (although one-third to one-half of fish caught by this method usually die), but corals are seriously damaged in the process of extracting the stunned fish, and by the cyanide itself. 

Causes of Overfishing

The causes of overfishing are manyfold and complex, with multiple factors compounding and contributing to the problem. 

Better Technology 

Fishing is no longer the imprecise, uncertain practice that it once was. Technological advances — like satellite navigation, echo-sounders, and acoustic cameras — have made it easier for fishers to locate fish and capture them with great precision. Huge, commercial fishing vessels also have refrigeration systems on board, which makes it possible for boats to stay out at sea for longer and catch greater volumes of fish at once. 

Population Growth and Demand

Quite simply, there are more people in the world, and so a greater demand for fish. Marine fish provide about 15% of all animal protein consumed by humans, but as populations grow, so does the number of fish needed to satisfy demand. The average increase of global fish consumption has actually outpaced population growth, meaning people are also consuming more fish on average. Between 1990 and 2018, consumption of seafood rose 122%, and as it’s grown, the level of sustainable fish stocks has dropped by about a third from 1970s levels.

Government Subsidies and Incentives

Governmental support is cited as a reason why overfishing continues. Currently, annual subsidies to marine fisheries globally are around $35 billion — that’s about 30% of the first sale value of all caught fish. This financial support (sometimes in the form of lower taxes) that’s given to the fishing industry offsets the costs of doing business, incentivizes the catching of fish beyond sustainable levels, and encourages companies to continue fishing in overexploited areas where they would otherwise be unsuccessful. Subsidies are also an issue of equity in the sector — they are usually given to huge industrial fisheries and not smaller ones run by local people in places like coastal west Africa and the south Pacific, so the locals are forced to compete with these larger, subsidized companies. 

Poor Management of Fisheries 

Fisheries can be managed by governments either locally, regionally, nationally, or internationally, but are sometimes managed poorly with few barriers in place to prevent overfishing. Proper management will consider research on the state of fish stocks and how to sustain their populations, and usually institute catch quotas and other requirements for fisheries. But many fisheries are governed poorly and allow for too much fishing, or have inadequate reporting, monitoring, or enforcement systems that enable exploitation of the stocks.  

Lack of Protection for Oceans 

Oceans cover 70% of the Earth’s surface, but less than 8% (roughly the size of North America) of the ocean is protected. Marine Protected Areas have limits on human activity, but it’s a broad term that could mean many things; some have restricted visitation, allow for sustainable use by indigenous populations, and or even allow for commercial fishing. In fact, 80% of protected ocean areas still allow fishing within their borders. To properly restore biodiversity, a 2021 study suggests that 30% of oceans needs to be protected.

Environmental Impacts of Overfishing

Overfishing poses a huge threat to marine environments, from declining fish populations, to habitat destruction, to ocean pollution, and even the acceleration of climate change.  

Declining Fish Populations 

When fishery stocks fall below biologically sustainable levels, populations suffer and are at risk of becoming either endangered or extinct. Among the most overfished species are Southern and Atlantic bluefin tuna, European eel, cod, swordfish, groupers, and sturgeons. Currently, only 3% of Pacific bluefin tuna remain based on the population’s historic levels. Overall, marine species have decreased nearly 40% in the past 40 years. 

When their populations shrink, fish have to adapt differently. They might change in size, reproduce differently, or mature on a different timeline. When fish are captured when they are too small — a phenomenon called “growth“ overfishing — they never make it to maturity and thus don’t reproduce as much, so the overall yield and population of the fish shrinks. “Recruitment“ overfishing occurs when the adult population is so depleted that there aren’t enough fish to produce offspring. Deep sea fish like orange roughy, for example, grow very slowly given the lack of resources on the ocean floor, often taking decades to reach breeding maturity — so when they are caught, it takes a very long time for their populations to replenish. 

Destruction of Ecosystems 

Overfishing not only threatens the species themselves, but also the ecosystems they live in — particularly already-threatened coral reefs. It has been found to be the most serious threat to coral reefs, and it’s predicted that 90% of global coral reefs will be dead by 2050 due to commercial fishing. Besides blast- and cyanide-fishing practices, reefs are also impacted by trawling (sometimes called “bottom dragging”), a fishing tactic of dragging large nets along the ocean floor to catch fish. When algae-eating species are overfished, algae can also propagate unchecked and eventually smother the coral it grows on.

Bycatch

Bycatch is closely tied to overfishing, and constitutes one of its largest environmental impacts. Because commercial fishing hauls in huge numbers of fish at once, unwanted fish and animals are often caught in the process and are then merely discarded. Unwanted (or “non-target” species) are swept up when trawling for large quantities of fish using indiscriminate, non-selective gear that captures all wildlife in its path, including other species of fish, sea lions, dolphins, turtles, sharks, and even sea birds. Bycatch is sometimes returned to the ocean, but the animals often die or are injured so severely that they cannot reproduce. 

Billions of fish and hundreds of thousands of sea turtles and cetaceans are lost every year as bycatch, according to the World Wildlife Fund. Six out of seven species of sea turtles are either threatened or endangered as a direct result of fishing — they often get caught when fishers trawl for shrimp or prawns on the ocean floor, where turtles like to forage. Sharks are very susceptible, too, and about 50 million are killed every year as bycatch by unregulated fisheries. More than one-third of all sharks, rays, and chimaeras are now at risk for extinction due to overfishing alone. 

A fishing practice called “longlining” — whereby a line is sent out with hundreds or sometimes thousands of baited hooks — results in a lot of bycatch. Longlining is usually employed to catch tuna, swordfish, and halibut, but other fish go after the hooks, too. Sea birds also get caught in the lines when they dive under the water to fish. 

Disruption of Food Chains

The removal of fished species and the death of bycatch can seriously impact marine trophic structures. Fish are a part of complex marine food chains, serving as food sources for larger fish and feeding on smaller fish or vegetation. Sharks, for example, are large predators that regulate smaller species below them, so when large numbers are lost as bycatch, smaller fish populations might grow too large. If there are unnaturally high numbers of fish, they might feed too heavily on vegetation that’s needed by other species, further impacting the ecosystem and causing a ripple effect through the food chain. 

Plastic Pollution From Ghost Gear 

When fishers engage in huge fishing operations, they leave a lot of trash in their wake. Up to one million tons of fishing gear is abandoned in oceans every year, smothering animals, corals, and other marine habitats. This “ghost gear” makes up 10% of all ocean plastic pollution, but constitutes the majority of large plastic items. In terms of weight, 86% of plastic in the Great Pacific Garbage Patch is fishing nets. Like other ocean plastics, this gear breaks down slowly over time, releasing microplastics into the ocean as it degrades.  

Climate Change

Our oceans are carbon sinks, meaning they absorb carbon dioxide released into the atmosphere, effectively mitigating climate change. In all, the ocean absorbs 25% of our CO2 emissions and 90% of heat generated by humans.  Fishing activity removes sequestered  “blue carbon” from the ocean and releases it into the atmosphere.

Carbon is sequestered in the bodies of phytoplankton, which convert CO2 into sugars, but disrupting marine habitats and food webs impacts their activity. Carbon stored in the sediment of the seafloor is also released when bottom trawling disturbs its surface.

Social Impacts of Overfishing

Besides the environmental impacts of overfishing, exploiting our oceans also impacts economies that depend on fishing for income, and communities that rely on fish as a source of protein. 

Fishing as Livelihood

The fishing industry is currently valued at $362 billion, and supplies income for 10-12% of the world population, from both large- and small-scale fishing operations. 60 million people globally work either directly or indirectly in the fishing industry, but if fish stocks are overexploited and can no longer be profitably harvested, many of these jobs could disappear. Coral reef areas are also tourism hubs for activities like snorkeling and boating. If these ecosystems are destroyed by trawling and destructive fishing, local communities that depend on tourism will also suffer. 

Food Security 

Sustaining fish populations is also a matter of food security. Globally, 3 billion people depend on seafood as a protein source, especially in the Maldives, Japan, Iceland, Cambodia, and western coastal communities in Africa, all of which could face a food crisis if fish stocks drop so low that they cannot replenish themselves. Because of poorly managed fisheries, the Marine Stewardship Council estimates that 72 million more people every year are missing out on getting enough protein. 

What About Farmed Fish?

Fish farming (also called aquaculture) raises fish in captivity for consumption. The Southern bluefin tuna was first bred in captivity in 2009, and now about half of the fish eaten in the U.S. are farmed. Aquaculture is often touted as a solution to wild-caught fish, but it comes with its own set of issues. Carnivorous fish — like tuna and salmon — need to eat smaller fish in order to grow. So while these fish themselves are grown in farms, their prey are still being fished — often unsustainably — in order to feed them, merely displacing the problem. There are nutritional drawbacks to farmed fish as well. Wild fish get omega-3s (a fatty acid that is a main benefit of eating fish) from eating aquatic plants, which they don’t get in fish farms when fed a diet of corn and soy. A growing body of research suggests that, contrary to prior assumptions, fish do feel pain and stress, which are heightened when living in confined conditions. 

Solutions to Overfishing

There are, however, solutions to overfishing — both on the personal and the legislative level. 

Remove Incentives and Subsidies 

Subsidies make it possible for companies to keep fishing in overfished waters, even when these ventures become less profitable as fish populations decline. It’s widely understood that ending subsidies would be effective at preventing overfishing, as 54% of high-seas fishing grounds wouldn’t be profitable in their absence. The World Trade Organization made moves in 2022 to curb subsidies by securing the Fisheries Agreement, under which countries are working to ban subsidies to IUU fishing and overfished stocks. 

Better Management Systems  

Better management of fisheries could reduce overfishing, as could enforcement of rules, including catch limits/quotas, whereby only a predetermined amount of fish can be caught every year; catch-share programs, which distribute harvest allowances to companies or individuals, who can then either use or sell them; and gear restrictions that only allow for species-specific nets or other devices that prevent bycatch, like turtle excluder devices (TED) that allow megafauna and turtles to escape shrimp nets. 

Small-scale fisheries in Japan and Chile have found success in using rights-based management. Under this system, exclusive ownership is given to a person, company, or municipality (like a village or community), which removes the tragedy-of-the-commons mentality and gives the owner an incentive to avoid overfishing the waters. 

Better Fishing Methods 

Technological advances have contributed to overfishing, but they might also offer a solution. The Global Environment Facility (GEF) and the FAO instituted a program in 2018 that promoted fish aggregating devices (FAD), which are essentially floating devices that lure fish rather than catch them with large nets. So far, the program has seen a successful reduction of bycatch in Pakistani fisheries. SafetyNet Technologies has also developed a method of using LED lighting on gear that changes color and intensity to evoke behavioral responses from fish, allowing them to target specific species. These are among the many technological innovations being explored to reduce bycatch and other harmful effects of commercial fishing. 

Legislation and Governmental Intervention 

Even with new technological solutions, legislation is needed to implement management strategies and ensure compliance. Legislation around overfishing in the United States has seen success in helping fish species rebound. The Magnuson-Stevens Act — which provided for the management of marine fisheries in U.S. waters — passed in 1976 and is credited with helping Atlantic sea scallop and haddock populations rebuild, but hasn’t been updated or reauthorized since 2006. The Seafood Import Monitoring Program (SIMP) managed by NOAA is a federal traceability standard, whereby importers have to report data about where fish were harvested for over a thousand different species. Before SIMP was implemented, almost a third of all wild-caught seafood imports to the U.S. were from illegal fishing operations. However, some environmental groups have argued that the program needs to be more stringent.

Protected Oceans 

While some Pacific island nations have historically protected their oceans, the U.S. and European countries didn’t manage coastal fisheries until the 20th century. Only 8% of the ocean is currently classified as Marine Protected Areas (MPAs), which are protected along a spectrum: minimally, lightly, and highly/fully protected, which prohibits any kind of extractive activity (including drilling, mining, and fishing, aside from subsistence and recreational fishing under some circumstances). Science has shown that even under the best management by fisheries, an ocean ecosystem doesn’t receive all of the benefits of a fully protected MPA. Creating more MPAs would give species the chance to replenish within their borders. Ultimately, fisheries would benefit from these protections, too, as fish populations rebound within MPAs, and then often go back to fishing areas — a phenomenon referred to in the industry as “spillover” — and can be caught once again. 

Buy Sustainable Fish 

On the personal level, choosing sustainably caught fish creates an impact. The U.S. is a top importer of seafood (Americans consumed around 6.3 billion pounds of seafood in 2019, 90% of which was imported), so our choices can have a large influence on global practices around fisheries. Here’s how to choose sustainable fish for yourself and your household:

1. Eat locally sourced fish when possible, or join a community-supported fishery (CSF), which is similar to a CSA.
2. Use seafood guides to choose the best seafood, like the Environmental Defense Fund’s Seafood Selector or the Seafood Watch app from the Monterey Bay Aquarium, which shares recommended species. 
3. Look for labels on fish packaging from vetted third-party organizations, which award their certifications to fisheries that meet their standards. Some of the best are the Marine Stewardship Council, BAP (Best Aquaculture Practices), and the Aquaculture Stewardship Council.

Takeaway

Huge demand for fish and inadequate management of fisheries has allowed overfishing to continue. If unchecked, this decline in fish populations will have devastating impacts on the environment, food security, and the many economies that depend on the fishing industry. However, the many legislative and technological solutions to overfishing are in our hands.