Bycatch — the capture and killing of non-target species in commercial fishing — causes the deaths of an estimated 40% of all animals caught globally, representing an enormous and largely invisible welfare harm.
Bycatch welfare harm is multidimensional. Non-target animals caught in nets and longlines experience the stress of capture, physical injury from gear, and drowning for air-breathing species. Marine mammals and sea turtles that must surface to breathe die of asphyxiation within minutes of entanglement if unable to surface. Seabirds caught on longlines drown. Juvenile fish of all species — including target species — are caught and discarded dead before reaching reproductive maturity. The cumulative welfare harm of bycatch across global fisheries is incalculable but enormous. Fisheries management approaches that reduce bycatch through gear modification, time-area closures, and observer programs provide direct welfare benefits alongside conservation benefits.