Home » Environment

Bycatch: The Unseen Crisis Threatening Marine Life

Unintended catch in commercial fisheries is leading to drastic consequences for marine biodiversity, ecosystems, and economies worldwide.

By Sneha Tete, Integrated MA, Certified Relationship Coach

Created on Sep 27, 2025

Unintended catch in commercial fisheries is leading to drastic consequences for marine biodiversity, ecosystems, and economies worldwide.

Bycatch: The Invisible Threat Beneath the Surface

Bycatch — the unintended capture of species such as dolphins, turtles, seabirds, and other marine animals during commercial fishing operations — stands as one of the greatest yet often overlooked threats to marine biodiversity today. This silent crisis not only devastates wildlife populations, but also disrupts entire marine ecosystems and undermines economic livelihoods around the globe.

What is Bycatch?

Bycatch refers to all the marine animals and plants inadvertently caught — and often discarded — by fisheries targeting other species. While ‘target species’ are those fish and seafood meant for sale or consumption, bycatch includes everything else swept up in nets or hooked on lines: from small invertebrates to endangered whales, sea turtles, sharks, rays, and seabirds.

Bycatch may be discarded dead or injured back to the ocean, or sometimes kept for low-value uses.
Modern industrial fishing gear, such as trawl nets, longlines, gillnets, and purse seines, are especially prone to high bycatch rates.
Many types of bycatch are either not wanted, illegal to keep, or have no market value.

How Much Bycatch Is Caught Each Year?

Bycatch is a global crisis affecting all oceans and seas. The statistics are alarming:

10.8 million tonnes of bycatch are discarded worldwide every year — about 10% of the global catch .
Longline fishing kills an estimated 300,000 seabirds annually, including many endangered species .
In the U.S. alone, nearly 50,000 sea turtles are unintentionally caught each year, with a high fatality rate among those .
Some fisheries record bycatch rates where up to 90% of what is caught is not the intended target species.

Who Are the Main Victims?

Group	Examples	Roles in Ecosystem	Main Threats
Marine mammals	Dolphins, porpoises, whales, seals	Predators, keystone species, nutrient cyclers	Entanglement and drowning
Sea turtles	Leatherbacks, loggerheads, greens	Maintain healthy seagrass and reefs	Injury, drowning, population collapse
Seabirds	Albatrosses, petrels, shearwaters	Control fish populations, fertilize islands	Longline hooks, collision, drowning
Sharks and rays	Blue sharks, hammerheads, manta rays	Apex predators, regulate food webs	Trapped, finned, thrown overboard
Non-target fish and invertebrates	Juvenile fish, corals, sponges, crustaceans	Nursery role, reef builders, biodiversity	Physical damage, population declines

Why is Bycatch Such a Serious Problem?

Biodiversity Loss: Bycatch drives down populations of rare and endangered species, sometimes to the brink of extinction.
Ecological Imbalances: Disrupts delicate food webs. For example, fewer sharks mean more prey species, leading to cascading effects such as reef degradation.
Slows Recovery of Overfished Stocks: Bycatch can kill young or protected fish, impeding recovery of target populations and threatening future harvests .
Habitat Destruction: Gear like trawls not only catch unwanted species but also damage seafloor habitats crucial for marine life .

Ecological Impact of Bycatch

Marine ecosystems are complex webs, where the removal of any species—especially apex predators or keystone species—creates ripple effects. Consider these consequences:

Sharks keep prey populations balanced. Their decline can lead to an overabundance of mid-level predators, which then reduces smaller fish and damages reef health.
Sea turtles maintain healthy seagrass beds and coral reefs. Fewer turtles can lead to seagrass overgrowth, harming fish nurseries and reef vitality.
Seabirds control fish and squid populations and fertilize ecosystems through their guano. Crash in seabird populations can lead to unchecked prey numbers and nutrient loss on islands.
Bycatch of corals and sponges can destroy critical habitats and slow ecosystem recovery for decades.

Bycatch doesn’t just batter ecosystems — it carries a steep economic and societal cost:

Reduced fishery yields: Killing juvenile or breeding fish through bycatch reduces the reproductive potential of fish stocks, threatening long-term viability for fishing communities .
Early fishery closures: When bycatch quotas for protected species are exceeded, authorities may close fisheries prematurely, hurting income for fishers.
Insurance and regulatory costs: Fishers face financial penalties, new regulations, and increased monitoring costs when bycatch is high.
Loss for tourism: Declines in charismatic megafauna (like turtles and dolphins) and coral reefs reduce ecotourism potential in many coastal regions .
Food security risk: Depleting populations of edible or economically important non-target species can undermine regional food sources.

What Causes Bycatch?

Many types of commercial fishing gear are non-selective, snaring anything in their path. The main culprits include:

Trawl nets: Dragged along the seafloor or in midwater, they capture vast numbers of species indiscriminately.
Longlines: Can stretch for tens of miles with thousands of baited hooks, catching anything interested in the bait.
Gillnets: These walls of netting trap fish (and many other creatures) by their gills when they attempt to swim through.
Purse seines: Used to surround schools of fish, but can also encircle dolphins, turtles, or other unintended species.
Fishing in sensitive areas: Targeting regions with high biodiversity or near breeding/nursery grounds increases bycatch risk.

Notable Bycatch Disasters

Tuna fisheries and dolphins: Purse seine tuna fishing in the 1960s and ’70s drove dramatic dolphin population declines in the eastern Pacific.
Albatross bycatch: The use of longlines in southern oceans led to plummeting numbers of large seabirds — some species remain at risk of extinction.
North Atlantic right whales: Entanglement in fishing gear is now the leading cause of death for this endangered species, stalling population recovery .
Sea turtles and shrimp trawls: Before regulations like Turtle Excluder Devices (TEDs), tens of thousands of turtles were killed annually in U.S. shrimp fisheries.

The Hidden Toll: Cryptic and Unreported Bycatch

Much bycatch goes undetected and unreported.

Many fisheries lack effective monitoring; observer coverage is often below 5% globally.
Animals that die after escaping or are injured but not recovered are rarely tallied — this is referred to as ‘cryptic mortality’ .
Some species, such as whales, may die from entanglements but their bodies are never found.
Poor data quality and lack of resources hamper efforts to calculate the full extent of bycatch damage .

What is Being Done to Reduce Bycatch?

Mitigating bycatch requires both regulatory action and practical innovation:

Legislation: Key laws in the U.S. include the Magnuson-Stevens Fishery Conservation and Management Act, the Endangered Species Act, and the Marine Mammal Protection Act .
Fisheries closures: Temporarily halting fishing in hotspots or when bycatch limits are exceeded.
Spectator programs and electronic monitoring: Fisheries observers or cameras track what is actually caught — critical for reliable data .
Gear modifications and technological innovation:
- Turtle Excluder Devices (TEDs): Allow turtles to escape trawl nets.
- Bycatch reduction devices (BRDs): Net attachments that let smaller or non-target species escape.
- Acoustic pingers and luminous lines: Reduce whale and turtle entanglements and keep seabirds away from baited hooks.
- Circle hooks, net lights, and strategic baiting: Reduce bycatch for many species.
- Time-area closures: Restrict fishing during periods or in areas of high bycatch risk.
Selectivity and sustainability certification: Catching only what is needed through careful planning, and certifying fisheries that minimize bycatch (e.g. through the Marine Stewardship Council).
International agreements and partnerships: Collaborative efforts among governments, NGOs, and industry seek to standardize best practices worldwide.

Challenges to Further Reducing Bycatch

Insufficient monitoring and enforcement: Lack of oversight allows high bycatch rates to persist, especially in international waters.
Data limitations: Many ocean regions and fisheries lack up-to-date bycatch statistics, hindering targeted solutions .
Economic incentives: Some bycatch is used as fishmeal or sold when prices or quotas are tight, resisting true selectivity.
Technical barriers: Not all gear can be easily modified without economic cost or impracticality for fishers.
Complex food webs: Full ecological effects of bycatch remain difficult to quantify, making ecosystem-based management challenging.

How Consumers and Communities Can Help

Choose sustainable seafood: Look for products certified by recognized bodies emphasizing bycatch reduction.
Support transparency and traceability: Demand labeling and sourcing information for seafood products.
Advocate for policy change: Support stricter regulations, bycatch limits, and enforcement.
Promote awareness: Share knowledge about bycatch with others to drive demand for change.

Frequently Asked Questions (FAQs) on Bycatch

Q: What is the difference between bycatch and discards?

A: ‘Bycatch’ refers to all non-target species caught during fishing; ‘discards’ are those portions of the catch (including bycatch) that are thrown back to the sea, often dead or dying.

Q: Why is bycatch such a pressing issue today?

A: Declines in wild fish stocks, increases in industrial fishing, and growing demand for marine resources have heightened pressure on non-target species, pushing some to the edge of extinction.

Q: Can bycatch be completely eliminated?

A: Some level of bycatch may always occur, but advances in gear design, strict regulations, and improved fisheries management can dramatically reduce it.

Q: Are there success stories in bycatch reduction?

A: Yes. Introduction of Turtle Excluder Devices and bird-scaring lines in some fisheries have reduced sea turtle and seabird bycatch by more than 80% in certain regions.

Q: What can individuals do to help stop bycatch?

A: Consumers can buy sustainable seafood, support organizations working for ocean conservation, and advocate for science-based policy changes.

References

Author

Sneha TeteBeauty & Lifestyle Writer

Sneha is a relationships and lifestyle writer with a strong foundation in applied linguistics and certified training in relationship coaching. She brings over five years of writing experience to thebridalbox, crafting thoughtful, research-driven content that empowers readers to build healthier relationships, boost emotional well-being, and embrace holistic living.

Read full bio of Sneha Tete