Fishing Bycatch: An Overview

Every year, billions of animals—fish, marine mammals, sea turtles, seabirds—die as unintended victims of commercial fishing. This phenomenon, known as bycatch, is one of the greatest yet least visible threats to ocean life. Unlike targeted species, these animals are often discarded dead or dying, their suffering hidden beneath the waves. Bycatch is not a rare accident; it is a systemic consequence of modern fishing methods, and understanding it is the first step toward change.

The scope of bycatch is staggering: the Food and Agriculture Organization estimates that bycatch accounts for roughly 40 percent of global marine catches, around 38 million tonnes annually. Beyond the sheer volume, bycatch is a leading cause of decline for endangered species like the vaquita and many albatrosses. However, this crisis is not inevitable. Proven gear modifications, international agreements, and consumer choices can drastically reduce bycatch. This guide explores what bycatch is, why it matters, the numbers behind it, and what you can do to help.

What it is

Bycatch is the capture of species that fishermen did not intend to catch and cannot or will not keep. It occurs in almost every fishing operation, from small-scale artisanal boats to large industrial trawlers. Bycatch includes juvenile fish of target species, non-commercial fish, crustaceans, sea turtles, marine mammals, seabirds, and even sharks. In many cases, these animals are thrown back into the sea, dead or dying, because they have no market value or are legally prohibited to keep.

The severity of bycatch varies by gear type. Bottom trawling—dragging a giant net along the seafloor—is particularly indiscriminate, scooping up everything in its path. Longlines, which can extend for tens of kilometres with thousands of baited hooks, snag seabirds and turtles. Gillnets, vertical walls of nearly invisible netting, entangle dolphins, porpoises, and other air-breathing animals that drown after becoming trapped.

Albatross caught on longline hook, illustrating seabird bycatch.

Why it matters

Bycatch matters because it is causing avoidable suffering and pushing already fragile species toward extinction. For animals like sea turtles and marine mammals, entanglement in fishing gear is often a slow, painful death by drowning or severe injury. These animals breathe air, and once caught, they cannot escape; their distress can last for minutes or even hours. The suffering is not accidental in the sense of being unavoidable—it is a direct consequence of industrial fishing practices.

Beyond animal welfare, bycatch destabilizes ecosystems. Removing huge numbers of non-target predators and prey disrupts food webs, with ripple effects throughout the ocean. For example, dramatic declines in sharks—often taken as bycatch—have led to explosions in their prey species, such as rays and smaller fish, which in turn impacts commercial fish stocks.

Moreover, bycatch disproportionately affects species that are slow to reproduce, such as albatrosses, which may live 50 years but lay only one egg every two years. The loss of even a few individuals can doom a population.

The numbers

Bycatch is measured in millions of tonnes and hundreds of thousands of animals, yet precise figures remain uncertain. The Food and Agriculture Organization (FAO) estimates that bycatch accounts for roughly 40 percent of global marine catches, or about 38 million tonnes each year. However, this is a widely cited figure, and some researchers believe actual rates may be higher, particularly in unregulated fisheries.

Scientific studies offer sobering specifics:

• Around 300,000 cetaceans (whales, dolphins, porpoises) die in fishing gear annually.
• Over 700,000 seabirds, including 100,000 albatrosses, are killed per year.
• An estimated 40 percent of all marine turtles caught in fishing operations die as a result.
• In some fisheries, the ratio of bycatch to target catch can be as high as 10 to 1.

The vaquita, a small porpoise endemic to Mexico's Gulf of California, is the world's most endangered marine mammal. Fewer than 10 individuals remain, and its primary threat is bycatch in gillnets. Similarly, several albatross species are classified as endangered or critically endangered, largely due to longline fishing.

What's changing

Efforts to reduce bycatch are underway, from on-the-water gear innovations to international policy agreements. Gear modifications have proven highly effective where applied. Turtle Excluder Devices (TEDs)—trapdoor-like escape hatches in shrimp trawls—can reduce sea turtle bycatch by up to 90 percent. Bycatch Reduction Devices (BRDs) in nets allow small fish to escape. On longlines, setting hooks at night and using weighted lines can cut seabird bycatch by as much as 90 percent.

Regional fisheries management organisations (RFMOs) now mandate TEDs in many tuna and swordfish fisheries, and some countries have banned the most destructive gear in sensitive areas. Electronic monitoring, including cameras and sensors, is improving data collection and transparency. However, enforcement remains weak, and compliance is often voluntary.

Reforms in fishing subsidies also offer leverage. The World Trade Organization (WTO) reached an agreement in 2022 to curb subsidies that contribute to overfishing and bycatch. Meanwhile, consumer pressure for sustainable seafood has led major retailers to adopt certification schemes, though such schemes have been criticised for lax standards.

What you can do

Your choices as a consumer and citizen can influence the fate of millions of marine animals. The most direct way to avoid supporting bycatch is to reduce or eliminate seafood consumption. A plant-based diet sidesteps the problem entirely. If you do eat fish, choose species and sourcing methods with low bycatch risk—look for seafood certified by the MSC (Marine Stewardship Council) or rated green on the Monterey Bay Aquarium Seafood Watch list, though these tools are imperfect.

Support organisations that advocate for stronger fishing regulations and protected marine areas. Asking your representatives to back legislation that mandates bycatch reduction devices and rejects harmful subsidies makes difference. Finally, talk about bycatch with friends and family—the more public awareness, the more pressure on industry and governments to act.

Together, these actions can help shift fishing practices away from indiscriminate extraction toward a model that respects marine life. Bycatch is not an inevitable price of fishing; it is a choice—and we can choose differently.

How bycatch works in practice

Bycatch is not an accidental anomaly but a structural feature of how commercial fishing operates. Nearly every gear type has a blind spot: trawls sweep indiscriminately, longlines offer baited hooks to any hungry mouth, and gillnets create invisible walls that entangle anything passing. The scale is immense—some trawl nets are large enough to swallow a jumbo jet, and longline fleets set billions of hooks each year. This means bycatch is not a rare event but a constant accompaniment to fishing, often exceeding the target catch in volume.

The daily reality for animals caught as bycatch is grim. Fish and invertebrates suffer crush injuries, barotrauma (expansion of gases as they are hauled up), and suffocation. Air-breathing animals—sea turtles, marine mammals, seabirds—face drowning, with death taking minutes to hours. Even when animals are thrown back alive, many have injuries or stress that likely prove fatal; for example, studies suggest that many discarded fish die from predation or shock. This hidden mortality is still poorly quantified, making the true impact even larger than official figures suggest.

Costs and trade-offs

Reducing bycatch involves upfront costs and trade-offs, but these are often lower than the long-term ecological and economic losses. Gear modifications, such as TEDs and BRDs, require investment in new nets and training, and can initially reduce target catch slightly. In some cases, fishers resist changes because they fear lost income or because they want to sell all bycatch (where it is legal). However, these costs are often offset by reduced fuel use, less sorting time, and the conversion of bycatch into marketable catch. For example, one study found that TEDs could reduce bycatch without significant shrimp loss, and over time, fisheries with healthier stocks are more profitable.

The economic trade-offs also extend to subsidies. Many governments currently support unsustainable fishing practices, despite agreeing to the WTO subsidy curbs in 2022. Shifting these subsidies toward gear innovation and fisheries management could accelerate progress, but it requires political will. For consumers, the trade-off is simpler: choosing sustainably sourced seafood or plant-based alternatives may cost a little more, but it directs market pressure toward better practices. Table 1 summarises the key trade-offs.

"Key stat:" According to FAO (2023), reducing bycatch by just 1% could save millions of animals annually, highlighting the potential of even small policy shifts.

Common objections and misconceptions

Skeptics often argue that bycatch is unavoidable, that it is exaggerated, or that regulations are too costly, but evidence shows these objections are flawed. First, bycatch is not unavoidable—proven gear solutions can reduce it dramatically. Second, the scale is not exaggerated: independent studies consistently show significant mortality across species. Third, the cost argument overlooks that bycatch erodes the very resource base fishers depend on. A common misconception is that bycatch is always discarded, but in some fisheries, bycatch is landed and sold, meaning it is not technically bycatch but still unsustainably captured. This undercuts claims that bycatch is only a problem of discards.

Another objection is that sustainable seafood labels solve the problem. While MSC and similar certifications have improved some fisheries, they are not perfect. Critics note that certification can be costly for small fisheries, and standards may not cover all bycatch impacts. Therefore, relying solely on labels is insufficient; stronger regulations are needed. A final misconception is that bycatch only affects charismatic animals like turtles and dolphins, but it also kills billions of fish and invertebrates, which are essential to ocean ecosystems.

Regional and international angle

Bycatch is a global problem, but its severity and solutions vary sharply by region and by the type of fishery. In tropical developing countries, small-scale fisheries often have high bycatch of sea turtles and mammals due to lack of technology and enforcement. In temperate industrial fisheries, bottom trawling in the North Atlantic and North Pacific causes large discards. The Mediterranean Sea has one of the highest bycatch rates for marine mammals, while the Gulf of California is home to the vaquita, whose near-extinction is driven by gillnets. In the Southern Ocean, longline fisheries for toothfish pose a severe threat to albatrosses.

International efforts include regional fisheries management organisations (RFMOs), which set rules for high seas fisheries, but their effectiveness varies. The Food and Agriculture Organization (FAO) has developed international guidelines for reducing bycatch, and the Convention on Migratory Species helps protect species that cross borders. In 2022, the WTO's agreement on harmful subsidies marked a milestone, though it has yet to be fully implemented. Region-specific solutions are critical; for example, in the Gulf of California, compensating fishers to switch to sustainable gear has shown promise.

What the science tells us

Scientific research reveals that bycatch is not only a conservation issue but also a driver of ecosystem change, with effects that reverberate through food webs. Studies on trophic cascades show that removing top predators like sharks can alter entire communities. Long-term monitoring in the North Pacific has documented declines in seabird populations linked to bycatch. Furthermore, research indicates that bycatch of juvenile fish undermines future recruitment of commercial species, meaning that bycatch today reduces catches tomorrow. The science also highlights that some species are especially vulnerable: slow-reproducing animals like albatrosses and turtles can take decades to recover.

Advances in technology are improving our understanding. Electronic monitoring, from cameras to sensors, offers real-time data, and some fisheries now use smart nets with escape panels triggered by light or sound. Genetic analysis can identify bycatch species from tissue samples, aiding stock assessments. This growing body of evidence supports the call for precautionary approaches, such as marine protected areas and dynamic closures based on real-time bycatch alerts.

The road ahead

A future with drastically reduced bycatch is achievable, but it requires a combination of political will, industry investment, and consumer pressure. The most promising paths include scaling up gear innovation, implementing strong bycatch quotas with harsh penalties, and expanding large marine protected areas. Technology, such as satellite tracking of nets and automated monitoring, can make enforcement cheaper and more effective. Moreover, international cooperation is vital because many fish and migratory species cross national boundaries; the 2023 UN High Seas Treaty offers a new opportunity to protect biodiversity, though it remains to be ratified.

Realistic progress will be gradual. We may not see a world without bycatch overnight, but we can see a steady decline. For example, a 2022 FAO report noted that some fisheries have reduced bycatch by over 50% in a decade through consistent management. Every effort counts, and as public awareness grows, the pressure on industry increases. We can choose to be part of the solution, not the problem.

Trade-offs in bycatch reduction

Reducing bycatch involves genuine trade-offs between wildlife protection, fishing profitability, and food supply that must be weighed honestly. Measures like Turtle Excluder Devices (TEDs) can cost fishermen time and money to install and maintain, and some gear modifications initially reduce target catch before efficiencies improve. For small-scale fishers in developing nations, these costs can be prohibitive without external support or subsidies.

Another trade-off is nutritional and economic: bycatch species are often consumed locally, especially in poorer coastal communities where "trash fish" provides protein. Banning or discouraging bycatch outright can remove a food source for people who rely on it. Effective policy must therefore pair bycatch reduction with alternative livelihood programs or access to other protein sources.

There is also a tension between short-term enforcement and long-term sustainability. Strict quotas or gear bans may reduce bycatch quickly but can drive fishing activity into unregulated areas or push operators to hide bycatch. A phased approach with monitoring, training, and financial incentives often yields more durable results than abrupt prohibitions, though it comes with the cost of slower progress.

✅ Key trade-off: Fishing efficiency vs. ecological integrity—every net that catches more target fish also catches more non-target life, and no gear is perfectly selective. The challenge is finding the balance that preserves both livelihoods and marine ecosystems.

⚠️ Important nuance: Bycatch reduction is not universally beneficial; some measures, such as shifting from gillnets to longlines, may reduce dolphin deaths but increase seabird mortality. A holistic approach is needed, not a single-solution fix.

Common objections and responses

Objection: "Bycatch is a minor problem compared to habitat destruction or climate change." Response: Bycatch is a direct and immediate cause of mortality for hundreds of thousands of marine animals annually, and it is one of the most tractable problems to solve. Unlike climate change, which requires global coordination, bycatch can be reduced with targeted gear changes and enforcement, yielding visible results within years.

Objection: "Fishermen deliberately catch bycatch, so regulation won't help." Response: Most fishermen do not want bycatch—it wastes fuel, damages gear, and lowers catch quality. The issue is systemic, not malicious. When provided with workable alternatives like TEDs or hook-shielding devices, many fisheries have adopted them voluntarily, especially when paired with economic incentives or market access requirements.

Objection: "Certification schemes like MSC are just greenwashing." Response: There is legitimate criticism of certification standards—some allow high bycatch rates or fail to enforce compliance. However, these schemes have also driven measurable improvements in several fisheries, such as the Alaskan pollock fleet reducing seabird bycatch. The response is not to dismiss certification but to demand stronger standards and independent audits.

Objection: "Reducing bycatch will kill the fishing industry and raise food prices." Response: While some operations may face short-term costs, many fisheries have found that bycatch reduction improves long-term profitability by preserving target stocks and reducing wasted effort. In the US Pacific groundfish fishery, bycatch limits forced innovation that ultimately increased selectivity and stabilised catches, benefiting both fish and fishers.

Objection: "Bycatch is just nature's way—animals die all the time." Response: Natural mortality is a normal ecological process, but bycatch is anthropogenic and often targets species with low reproductive rates, pushing populations toward extinction. Unlike a predator-prey cycle, bycatch removes animals without any ecological benefit, creating imbalances that harm entire ecosystems, including the prey species fishermen depend on.

The regional angle for English-speaking readers

Bycatch affects English-speaking countries differently, from the North Atlantic to the Pacific, and policy varies by region. In the United States, the Magnuson-Stevens Act requires bycatch minimisation to the extent practicable, but enforcement is uneven across fisheries. The West Coast groundfish trawl fishery has been a success story: after implementing catch shares and hard bycatch quotas, it reduced rockfish bycatch by 80 percent between 2011 and 2015, according to NOAA. In contrast, the Gulf of Mexico shrimp trawl fishery still struggles with turtle bycatch, despite TEDs being mandatory since 1987.

In the United Kingdom and Europe, the Common Fisheries Policy (CFP) introduced a landing obligation in 2015 that requires fishermen to land all catches, which was designed to reduce discards. However, this policy has been criticised for creating a market for unwanted fish and failing to reduce mortality. In Scotland, the langoustine trawl fishery has adopted innovative separator trawls to reduce cod bycatch, with some trials showing a 70 percent reduction, according to Marine Scotland.

In Canada, the Pacific groundfish fishery implemented 100 percent at-sea observer coverage in 2006, which dramatically improved data and enabled bycatch quotas. This led to a 90 percent reduction in catch of threatened rockfish species, as reported by Fisheries and Oceans Canada. However, Atlantic Canada still faces high bycatch of porbeagle sharks and Atlantic cod, a species once dominant and now struggling to recover.

In Australia and New Zealand, seabird bycatch in longline fisheries has been a priority. Australia's Southern and Eastern Scalefish and Shark Fishery adopted underwater setting chutes and night-setting, reducing albatross deaths from over 5,000 per year in the 1990s to near zero in recent years, according to the Australian Fisheries Management Authority. New Zealand has also mandated seabird mitigation measures, though bycatch of New Zealand sea lions in trawl fisheries remains a contentious issue.

📉 Statistical note: The regional disparity in bycatch rates is stark—developing nations often lack monitoring, so true figures are unknown, while wealthy nations like the US and Australia have better data but still face compliance gaps.

Comparison: gear types and their bycatch impact

Different fishing gears impose dramatically different levels and types of bycatch, with trawls being the most indiscriminate and hook-and-line among the most selective. The table below summarises key characteristics for the main gear types, based on FAO and scientific literature.

🌱 Key insight: The table shows that gear selectivity varies by two orders of magnitude. Switching from bottom trawls to more selective gears is not always possible economically, but hybrid approaches—such as converting bottom trawls to midwater or adding BRDs—can cut bycatch significantly without abandoning the fishery.

A practical checklist for reducing your bycatch footprint

This checklist gives you concrete, evidence-based actions you can take today to reduce bycatch, from personal diet to civic engagement. Not every item applies to every person, but each step contributes to the broader shift toward selective fishing.

• ✅ Go plant-based or pescatarian with intention: If you eliminate seafood, you avoid bycatch entirely. If you eat fish, choose species from low-bycatch fisheries, such as pole-and-line tuna or farmed shellfish (though farmed feed can have its own bycatch footprint).
• ✅ Use Seafood Watch or similar tools: Check the Monterey Bay Aquarium Seafood Watch list before buying. Opt for "Best Choice" or "Good Alternative" ratings, and avoid "Avoid" species, which often have high bycatch.
• ✅ Avoid shrimp from unregulated trawl fisheries: Shrimp is a major bycatch driver; look for certifications or ask your supplier about TED and BRD use. If unsure, choose other protein.
• ✅ Support organisations that push for regulatory reform: Donate to or volunteer with groups like Oceana, the Marine Conservation Society, or BirdLife International, which campaign for bycatch limits and gear changes.
• ✅ Contact your elected representatives: Email or call local MPs, senators, or congress people. Ask them to support legislation mandating bycatch reduction devices, observer coverage, and bans on destructive gear in protected areas.
• ✅ Ask your supermarket or restaurant about sourcing: Retailers respond to consumer queries. If you ask, "Does your seafood come from fisheries with bycatch mitigation?" they may change suppliers.
• ✅ Educate yourself and others: Read fisheries management plans, watch documentaries like "Seaspiracy" (with a critical eye), and share this page with friends. Public pressure matters.
• ✅ Participate in citizen science or CSOs: Report bycatch sightings or data to local fisheries agencies, especially if you fish recreationally. Some programmes allow anglers to submit bycatch logs.

Bottom line: Individual action alone won't solve bycatch, but it creates the political and market pressure needed for systemic change. Combine personal choices with advocacy for maximum impact.

Dolphin entangled in gillnet underwater, showing marine mammal bycatch.

What you can do next: from awareness to advocacy

The transition from reading to acting involves a few strategic steps that amplify your individual impact. First, identify your personal connection to the ocean—whether through food, recreation, or simply awe—and let that motivate your engagement. Then, set a realistic goal: commit to one dietary change, one advocacy action, or one donation this month. This avoids overwhelm while building momentum.

Next, engage with your community. Host a small gathering to discuss bycatch, invite a local marine biologist to speak, or post informative content on social media. Collective awareness grows through conversation, and policymakers listen to groups, not just individuals. If you fish recreationally, practice and promote catch-and-release methods that minimise harm, such as using circle hooks.

Finally, stay informed. Bycatch policies evolve—the WTO agreement on fisheries subsidies is being implemented, and new gear innovations emerge regularly. Follow organisations like FAO, NOAA, or the Marine Conservation Society for updates. Revisit this page periodically, and share it with others, because an informed public is the most reliable force for ocean recovery.

"Key stat:" Every tonne of bycatch avoided translates to roughly 200 fewer animals killed, based on FAO average body-weight estimates for mixed bycatch species. Your choices matter at the scale of individual lives.

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