Evidence base for application of Acoustic Deterrent Devices (ADDs) as marine mammal mitigation (Version 4)
Subsea noise produced by anthropogenic activities in coastal and offshore waters has the potential to cause injury or death to marine mammals. To reduce this risk, mitigation solutions have included the deployment of acoustic devices in proximity to the noiseproducing activity, to deter animals from potential injury zones. There is also the potential to use acoustic devices for collision risk mitigation.
Acoustic devices have been applied across various marine industries. The range of applications for these devices, i.e. different industries, intended purpose, or different target species, has led to a wide variety of available technologies on the market. Whilst most emit medium to high frequency sounds, the acoustic characteristics of each device differ in terms of the sound levels produced, frequency range, temporal pattern/duty cycle and harmonics. In addition, there are also differences in the method of deployment and operating functions.
Extensive reviews of devices are available; however, a single report, collating and summarising the evidence around their effectiveness was considered useful and enable the information to be processed readily by Statutory Nature Conservation Bodies (SNCBs) when advising regulators on the use of acoustic devices to deter marine mammals from areas where there is a risk of injury or death. The report reviews evidence on the effectiveness of acoustic devices at deterring a range of marine mammal species. A coarse assessment of the risk of injury from all ADDs is also undertaken with a general conclusion that the risk of injury is likely to be low for all devices, although this is context dependent. The report also provides a summary of the key relevant legislation and regulations pertaining to the protection of marine mammals in the UK.
Note: This report is a ‘live’ document, and the intent is for it to be updated periodically in line with additional information on the acoustic deterrents described herein, and on the basis of new technologies that become available.