Marine Mammal Bycatch: Dolphins, Porpoises, and Seals in Fishing Gear

Hundreds of thousands of marine mammals are accidentally caught and killed in fishing gear each year, representing one of the largest sources of human-caused cetacean mortality.

Key Facts

The International Whaling Commission estimates 300,000+ cetaceans die annually as bycatch in fishing gear worldwide
Common porpoises are among the most bycatch-affected species in the North Sea and North Atlantic
Gillnets, longlines, and trawl nets all catch marine mammals, with gillnets posing the greatest risk per unit effort
Acoustic deterrent devices called pingers significantly reduce porpoise bycatch in gillnet fisheries when properly deployed
The vaquita porpoise is critically endangered with fewer than 10 individuals remaining, primarily due to bycatch in totoaba nets
Bycatch mortality is notoriously difficult to monitor because most incidents are not observed by independent inspectors

Welfare Considerations

Marine mammal bycatch causes severe welfare harms: entangled animals may drown immediately, drown slowly over minutes to hours, or become entangled and suffer injury before eventual death. Dolphins and porpoises are highly sentient animals with complex social lives; their deaths also cause suffering to conspecifics. Solutions exist but require political will: mandatory pinger use, improved net designs, stronger observer programs, and area closures in critical habitats. Consumer choice for certified sustainable seafood can drive fishing practice change.

What You Can Do

Choose seafood certified by programs that include marine mammal bycatch reduction standards
Support the Marine Stewardship Council and similar certification bodies that require bycatch monitoring
Advocate for mandatory independent observer coverage on commercial fishing vessels
Campaign for stronger enforcement of bycatch reduction requirements in high-risk fisheries