Marine Mammal Bycatch: Dolphins, Seals, and Welfare

Marine mammals caught as bycatch in fishing gear experience drowning, entanglement injuries, and stress - with species including harbor porpoises, common dolphins, and monk seals facing significant bycatch mortality.

Key Facts

An estimated 300,000 cetaceans and tens of thousands of pinnipeds die as bycatch annually in global fisheries
Harbor porpoise bycatch in bottom-set gillnets is a primary driver of population concerns in the North Sea and Baltic
Mediterranean monk seals are among the world's most endangered marine mammals; gillnet bycatch is a major mortality cause
Common dolphins are caught in large numbers in French and Spanish Bay of Biscay fishing operations
Acoustic deterrent devices (pingers) significantly reduce cetacean bycatch in gillnets when properly deployed and maintained
Observer programs that monitor bycatch rates are essential for evidence-based management but coverage is often inadequate
The Marine Mammal Protection Act (MMPA) requires US fisheries to reduce bycatch to sustainable levels, with mixed enforcement success

Welfare Considerations

Marine mammals caught in fishing gear experience acute welfare harm: entanglement causes physical injury from the gear, and drowning follows when animals cannot surface to breathe. The time to drowning - which can range from minutes to hours depending on the species and gear type - represents a period of severe oxygen deprivation and panic. Entangled seals and sea lions may struggle against gear for extended periods before death or liberation, sustaining lacerations and exhaustion. Welfare-positive fisheries management combines pinger use, seasonal closures during peak marine mammal abundance, and observer programs that accurately quantify bycatch mortality rather than allowing industry self-reporting.

What You Can Do

Choose seafood from fisheries certified under standards with marine mammal bycatch monitoring requirements
Support organizations working on gillnet reform including Oceana and the Ocean Conservation Society
Advocate for expanded observer coverage in fisheries with documented marine mammal bycatch
Report entangled marine mammals to NOAA hotlines (1-888-256-9840) if you observe them
Support pinger technology research and mandates in high-bycatch fisheries