Managing predators at fish farm sea cages creates welfare challenges for both farmed fish and wild predators, requiring approaches that balance production security with wildlife protection.
Predator management at fish farms involves a three-way welfare consideration: the farmed fish, the predatory mammals, and the wider acoustic environment. Non-lethal seal deterrents including ADDs create chronic noise pollution that affects harbour porpoise foraging and communication. Porpoises exposed to ADD frequencies show avoidance behaviour and have been found dead near farms, though causation is difficult to establish. The welfare of seals and other wild predators is directly affected by management approaches - acoustic harassment causes distress, and lethal control causes death. Farmed fish welfare is affected when predators breach nets and injure or kill fish while causing panic and crowding stress in others. Integrated predator management combining secure net integrity, deterrents used minimally, and habitat management represents the current best practice.