Harbour porpoises are among Europe's most common cetaceans, yet face serious welfare threats from fisheries bycatch, underwater noise, and prey depletion. Individual welfare harms aggregate across hundreds of thousands of animals.
Harbour porpoise welfare is dominated by bycatch and acoustic stress. Net entanglement causes drowning — a rapid but panic-inducing death as the animal struggles against the net and loses consciousness from hypoxia. Pingers attached to gillnets emit acoustic signals that alert porpoises to net presence — effectiveness is high when properly maintained, but battery failure and degradation reduce field performance. Mandatory pinger requirements in EU member states have improved compliance but enforcement remains inconsistent. Seismic surveys for offshore energy development and pile-driving for wind turbine installation generate acoustic pulses that cause behavioural avoidance, temporary hearing threshold shifts, and in severe cases physical injury at close range. Buffer zones and acoustic monitoring around construction sites reduce, but do not eliminate, welfare impacts. Prey depletion from overfishing reduces food security for porpoises — healthy fish stocks are a prerequisite for porpoise welfare in coastal ecosystems.