Acoustic Deterrent Devices (ADDs) have often been used around fish farms to scare away predators such as seals. The ADDs work by producing loud noises designed to scare away any predators. However, often animals can become habituated to these ADD noises as the desire to eat outweights the annoyance of the ADD noise. Also, the ADDs can have an impact on non-target species.

Thomas Gotz and Vincent Janik from SMRU have just published a paper on a new approach to this, where they use sounds that specifically target seals. These sounds trigger the seals autonomous startle reflex. They tested these startle sounds at a marine salmon farm over a year and monitored the seals responses and the levels of predation during this time. Their results showed that seal predation was significantly reduced by the deterrent system – with no seal predation in 10 of the 12.5 test months when the device was active. This was a 91% reduction in seal predation levels. They were also able to show that harbour porpoise and otter distribution around the fish farms were not affected by the deterrent system sounds.

Their paper can be read here.

The data from this new study has also fed into a project that SMRU Consulting have recently been working on: The use of Acoustic Deterrents for the mitigation of injury to marine mammals during pile driving for offshore wind farm construction. This work involved a review of the evidence for marine mammal responses to various ADDs, an identification of the knowledge gaps and an assessment on how to progress with field trials to obtain sufficient data to determine if ADDs could be used for marine mammal mitigation during piling activities. This work follows on from our previous project on the use of deterrent devices.

Our own Dr Carol Sparling will be presenting an overview of this work TODAY at the Scottish Renewables Offshore Wind Conference in Glasgow. Her talk is entitled “Using Acoustic Deterrent Devices as mitigation for auditory injury to marine mammals as a result of pile driving noise” and will be presented in Parallel Session 4B: Offshore Wind – working with the environment.