Salmon farming - use of acoustic deterrent devices: report

7. Conclusions and Recommendations

1. The use of ADDs may be justifiable in some situations when there is no satisfactory alternative, as their use appears to be effective in some situations and contexts. However, SAWC recommends the application of the international consensus principles of wildlife control in the management of seals to ensure that this is continually evaluated in each situation.

2. When it has been identified that ADD use is justifiable, the selective or targeted use of these devices is strongly recommended. It would appear that ADDs are initially aversive to naïve seals, but that they may overcome the unpleasant nature of the sound if they have learnt that food (fish) is available. Therefore, use should be reserved for critical periods or as part of a suite of controls that can be used at different times.

3. SAWC recommends that any appropriate measures that can be made to reduce the possibility of harm to cetaceans is implemented as far as possible. Devices that are deployed only when seal attack or presence occurs, during periods such as fish crowding, when seals are likely to attack, are recommended. ADDs should also only be deployed when cetaceans are at a safe distance away. Available technologies should be reviewed at least every five years to determine whether ADD use can be phased out.

4. Alternative strategies to deter seals should also be used wherever possible. These include strategies that the industry is currently using or developing, such as extra-strength netting, double-netting and removal of mortalities. Altering sea-pen design to prevent seals entering pens should also be considered. As above, a review of state-of-the-art technologies should be made at least every five years to determine whether viable alternatives to ADDs are available and ADD use can be phased out.

5. Further research is required. Alternatives to the use of ADDs that do not impact on the welfare of protected species should be explored, as well as the use of technologies that protect fish, deter seals, but do not harm cetaceans.