A trial of acoustic harassment device efficacy on free-ranging bottlenose dolphins in Sardinia, Italy

Acoustic harassment devices (AHDs) have been deployed to reduce the interaction between different marine mammals and fisheries in many areas. Despite field studies on some marine mammal species, there is a lack of information about their effectiveness on common bottlenose dolphins. The controlled exposure experiment described here is the first practical attempt to assess the influence of an AHD on the behaviour of free-ranging common bottlenose dolphins in association with a marine fin-fish farm. A total of 90.7 h were spent in direct observation of 55 groups of bottlenose dolphins along the north-eastern coast of Sardinia (Italy). Activation of the AHD did not have a significant and immediate effect on bottlenose dolphins’ presence, distance from the AHD, group size or time spent in the fish farm area. The AHD alone did not effectively deter bottlenose dolphins, particularly when other motivating factors, such as food, were present. Thus, prior to further employment of AHDs, additional research in their effects on the marine environment is essential for coastal conservation and aquaculture management.