Glossary · Environment

Bycatch

The unintended capture of non-target species during commercial fishing, often discarded dead or dying.

Definition

What 'Bycatch' means

Bycatch includes fish, marine mammals, sea turtles, seabirds, and invertebrates caught incidentally in nets, longlines, or trawls. It can account for up to 40% of global catch, causing significant ecological harm and waste. Mitigation measures include turtle excluder devices and circle hooks.

All glossary terms

In depth

The longer answer

Bycatch refers to any marine animal caught unintentionally during commercial fishing operations targeting a specific species. A fisherman aiming for tuna may haul in dolphins, sea turtles, sharks, or undersized fish that are then discarded, often dead or dying. Consumers encounter bycatch indirectly through seafood labels like "dolphin-safe" or certifications such as Marine Stewardship Council (MSC), which aim to reduce these accidental captures.

In practice, bycatch occurs because fishing gear—especially trawl nets, longlines, and gillnets—is not perfectly selective. Trawl nets dragged along the seafloor scoop up everything in their path, including corals and non-target fish. Longlines baited with hooks catch seabirds and sea turtles that dive for the bait. Global estimates suggest bycatch accounts for roughly 40 percent of the world's total marine catch, with millions of tons discarded annually.

For consumers, choosing seafood with credible eco-labels can help reduce demand for fisheries with high bycatch rates. However, labels vary in rigor, and some fisheries still kill significant numbers of non-target species despite certification. The most effective way to avoid contributing to bycatch is to avoid seafood altogether, as all fishing methods cause some unintended mortality. Plant-based alternatives offer a direct solution.

At a glance

Quick facts

Quick facts — Bycatch
Detail	What to know
Global scale	~40% of total marine catch
Main gear types	Trawl nets, longlines, gillnets
Common victims	Dolphins, sea turtles, sharks, seabirds
Certification example	Marine Stewardship Council (MSC)

In practice

What this means for you

Look for MSC or Friend of the Sea labels, but know they reduce—not eliminate—bycatch. No label guarantees zero unintended deaths.
Avoid fish caught with bottom trawls or driftnets, which have the highest bycatch rates. Check seafood guides from reputable NGOs.
When dining out, ask your server if the restaurant sources seafood from fisheries with bycatch mitigation measures like turtle excluder devices.
Consider that plant-based seafood alternatives, such as those made from algae or legumes, involve zero bycatch and no marine ecosystem disruption.

FAQ

Common questions

Is bycatch always thrown back dead?

Most bycatch is discarded dead or dying because the stress of capture, decompression, and handling is fatal. Some animals are released alive but often suffer injuries that reduce their survival chances. Regulations in some regions require returning certain species, but mortality rates remain high.

Does "dolphin-safe" tuna mean no bycatch?

No. "Dolphin-safe" means no dolphins were intentionally netted, but tuna fishing still catches other animals like sharks, sea turtles, and seabirds. The label addresses only one species group, not all bycatch. Other fishing methods also cause bycatch of many marine creatures.

Can bycatch be reduced to zero?

Not with current fishing methods. Even the most selective gear catches some non-target species. Bycatch reduction devices help but don't eliminate the problem. The only way to guarantee zero bycatch is to avoid consuming seafood entirely and choose plant-based alternatives instead.