New case study: protecting salmon without harming marine wildlife

Improving understanding of low-frequency acoustic seal deterrents

Seal attacks on salmon farms cause stress and injuries to fish, and even escapes through damaged nets. To prevent this, farms have used Acoustic Deterrent Devices (ADDs), which emit sound to keep seals away. Concerns arose that these sounds might disturb other marine species, such as harbour porpoises, which rely on sound for communication and hunting. This led to stricter regulations requiring proof that deterrents do not harm protected species.

This project tested Ace Aquatec’s low-frequency Acoustic Startle Response device (A-ASR), designed to deter seals while avoiding the sensitive hearing range of porpoises. The project partners were Ace Aquatec, University of St Andrews and Scottish Sea Farms. The total project value was £132K.

Researchers measured the device’s sound characteristics and monitored porpoise activity around a salmon farm in Orkney. Porpoises were consistently detected whether the device was active or not. While detection rates dipped slightly during operation, the change was not statistically significant, confirming no negative impact.

The project provided evidence that low-frequency deterrents are safe for non-target species, paving the way for European Protected Species (EPS) licences and wider adoption of environmentally responsible seal management. This approach could reduce fish losses, improve welfare, and support sustainable aquaculture.

The full title of this project is 'Low-frequency deterrent impact on non-target species'.

Read the full case study