Bycatch of dolphins and porpoises in fishing nets causes significant welfare harm to tens of thousands of animals annually, with acoustic deterrents and modified gear offering effective solutions.
Cetacean bycatch welfare involves drowning as the primary welfare harm for entangled animals: dolphins and porpoises that become entangled in fishing nets cannot surface to breathe and drown, experiencing prolonged asphyxiation that may last several minutes. The welfare harm is acute and severe, and occurs at a scale - tens of thousands of animals annually in European waters alone - that makes it one of the largest direct human causes of cetacean welfare harm globally. Acoustic deterrents (pingers) that emit sounds deterring porpoises from approaching nets have been shown to reduce harbour porpoise bycatch by 50-90% in studies across multiple fisheries. Their broader uptake has been limited by cost, maintenance requirements, and compliance monitoring challenges. Modified fishing gear that allows entrapped cetaceans to escape before drowning provides complementary solutions. The challenge of cetacean bycatch management is partly one of visibility: bycatch occurs at sea, often far from observers, and without adequate monitoring the scale of the problem remains underestimated. Mandatory observer coverage and electronic monitoring on fishing vessels would both improve data quality and create accountability that drives bycatch reduction behaviour.