Harbor porpoises are the most commonly bycaught cetacean in European waters, dying in gillnets set for fish, and preventing this mortality requires acoustic deterrents and gear modifications that reduce accidental capture.
Harbor porpoise gillnet bycatch welfare involves individual animals drowning over periods of minutes to hours in an inescapable net. This is one of the most clearly preventable forms of wildlife welfare harm because effective deterrent technology exists and is required by regulation. The gap between regulatory requirement and actual welfare outcome reflects enforcement inadequacy rather than technological limitation. Acoustic pingers that emit sounds within porpoise hearing range reliably reduce bycatch in fisheries where they are consistently used correctly. The welfare case for improving pinger compliance monitoring is therefore strong: each gillnet set with functioning pingers prevents a welfare event that would otherwise occur with high probability in porpoise habitat. Consumer seafood choices that favor pinger-verified fisheries create market incentives for compliance.