Harbour porpoises are among the most noise-sensitive cetaceans. Anthropogenic noise from shipping, sonar, and offshore construction causes significant welfare harm and population-level displacement.
Harbour porpoise welfare is chronically compromised by increasing underwater noise levels in UK coastal waters. Noise impacts range from subtle - reduced foraging efficiency, increased stress hormones, habitat displacement - to severe - acoustic trauma causing permanent hearing damage or disorientation leading to stranding. Offshore construction noise represents an acute welfare emergency during pile driving events, despite mitigation measures. The chronic noise floor from shipping creates a background of acoustic disturbance that reduces the quality of porpoise habitat across much of the North Sea and coastal waters. Effective welfare protection requires both event-specific mitigation and broader policy action to reduce chronic shipping noise.