Response of travelling bottlenose dolphins ( Tursiops aduncus) to experimental approaches by a powerboat in Jervis Bay, New South Wales, Australia

• Published in: Biological conservation 2006-02, Vol.127 (4), p.363-372
• Main Authors: Lemon, Michelle, Lynch, Tim P., Cato, Douglas H., Harcourt, Robert G.
• Format: Article
• Language: English
• Subjects: Acoustics; Animal, plant and microbial ecology; Applied ecology; Behaviour; Biological and medical sciences; Bottlenose dolphin; Cetacea; Conservation; Conservation, protection and management of environment and wildlife; Disturbance; Fundamental and applied biological sciences. Psychology; General aspects; Marine; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Tursiops aduncus
• ISSN: 0006-3207; 1873-2917
• DOI: 10.1016/j.biocon.2005.08.016

Powerboats are potentially a significant source of disturbance to coastal cetaceans. Information is scarce, however, on the nature of interactions between powerboats and dolphins, particularly when both surface and acoustic behaviour are combined. The surface behaviour and acoustic response of travelling dolphins to approaches by a powerboat were assessed by a series of experimental trials between November 2001 and November 2003 in Jervis Bay, New South Wales, Australia. Dolphin behaviour was monitored continuously from an independent research boat before, during and after a powerboat approached ( n = 12). Treatments were interspersed with control observations ( n = 12). Changes in surface behaviour indicated differences between the treatment and control periods ( z = 2.24, p = 0.025), with dolphins tending to alter their surface behaviour when exposed to the powerboat approach. Analysis also revealed a change in the direction of travel by dolphin groups when approached ( z = 3.22, p = 0.001). Changes in surface behaviour occurred at vessel approach distances outside the minimum approach distance of 30 m for recreational and commercial vessels, as proposed by the New South Wales National Parks and Wildlife Service. In contrast, there were no changes in dolphin whistle rates ( F 3,12 = 0.74, p = 0.54) or the duration of echolocation click bouts ( F 3,12 = 0.76, p = 0.59) when approached. These findings indicate that powerboats do affect the surface behaviour and direction of travelling inshore bottlenose dolphins in Jervis Bay; however it appears that this impact is not reflected in their acoustic behaviour.