Marine mammals including dolphins, porpoises, seals, and whales are caught incidentally in commercial fishing gear every year. The welfare suffering this causes — drowning, entanglement injury, and stress — is significant and often avoidable.
Marine mammal bycatch causes welfare suffering that spans a spectrum from rapid drowning to prolonged entanglement injury. Dolphins caught in purse seine nets and trawls may drown rapidly if unable to reach the surface to breathe; the terror and oxygen deprivation of this process represents acute, severe suffering. Whales that become entangled in trap lines and gillnet buoy ropes may survive the initial entanglement but suffer from restricted movement, infection at rope-cut wounds, reduced feeding ability, and progressive emaciation over weeks or months. Disentanglement teams can rescue some animals, but many entangled whales are never found or die before intervention. Solutions exist and are being deployed: modified gear with weak links that large whales can break, ropeless fishing technologies, acoustic deterrents, and area-time closures during whale aggregations all reduce bycatch rates.