Containment
St Andrews
The deployment of conventional high-power acoustic deterrent work on the principle of inducing pain in the auditory system of target animals. The ADDs, sometimes also labelled acoustic harassment devices (AHDs), emit sound at very high source levels and duty cycles. But the long-term success of these devices is generally limited and habituation - in contexts where food motivation is involved
Conventional devices have also been highlighted as a conservation concern as they cause long-term habitat exclusion in non-target species. Furthermore, many ADDs have some potential to induce hearing damage in habituated animals due to the high duty cycle of emission and extremely high source level.
An alternative to these deterrence methods can be found by har
The acoustic startle response is mediated through an evolutionary neurons. Grey seals tested in captivity and in the wild have been shown to exhibit directed escape responses to repeated startle eliciting stimuli.
The majority of seals which were exposed to startling sound pulses in a simulated foraging experiment showed an increase in responsiveness over time (sensitisation).This involved an interruption of foraging behaviour and the animals learnt to avoid the sound exposure location while otherwise exhibiting normal behaviour.
- animal is exposed to exceeds the auditory threshold by a certain amount (startle threshold). Hence, avoidance responses can be caused within
There is also a chance to control the strength of the avoidance response by changing how much a signal exceeds the startle threshold. More importantly, it is possible to exploit differences in species’ hearing abilities to design stimuli that elicit startle in one species but not in another.
hearing sensitivity in the target species is higher than in non-target spe dolphins. There is currently no commercially available device which uses
The method has been tested using isolated designed to deter seals but not affect harbour study showed that the number of harbour seals - duced while harbour porpoise distribution was unaffected by sound exposure.
In consecutive studies, the effect of the device on predation on salmon farms was investigated. months of the deployment period and compar-
isons to the pre-deployment period as well as two control sites demon
The timing of predation events throughout the one-year test period -
Genuswave has developed a prototype deterrent device based on this with a more sustainable alternative to current acoustic devices: the duty cycle is roughly one order of magnitude lower than in current com risk of hearing damage; and adverse effects on non-target species can be mitigated by choosing a frequency band where hearing in the target
Further advantages include the opportunity to deploy separate but synchronised units in order to create larger deterrence zones or acoustic barriers without the need for operating individual units at potentially
- or porpoise can be deterred by using a higher frequency sound pulse
The device contains a micro-controller and various communication ports which allow it to be used in conjunction with existing marine
The Genuswave commercial version is due to be deployed on three
“The animal can then be guided around the through repeatedly inducing small scale avoidance responses”