Cetacean disturbance by high speed ferries: a preliminary assessment [abstract]

L. J. Browning, A.D. Williams and E. Harland (1998). Cetacean disturbance by high speed ferries: a preliminary assessment [abstract]. Bioacoustics, Volume 9 (3): 220 -221

Ferry companies are increasingly utilising high-speed wave-piercing catamarans to provide fast alternatives to conventional services. The number of such ferries operating in the UK has doubled in the last 5 years, but the environmental impacts of this trend, including possible cetacean disturbance arising from noise pollution, have received little attention. In March 1997 a new high-speed ferry service began operating from Poole in Dorset, England, passing through the Durlston Marine Research Area, the site of a long-term bottlenose dolphin monitoring project. Recordings of the ferry were obtained, from portable and seabed mounted fixed hydrophones, in order to assess the potential for disturbance of the study animals. The most significant sound outputs are two sharp peaks around 500Hz. Apart from these, machinery noise also produces a continuous spectrum across the range 100Hz to above 5kHz. The other major noise source is from displaced water, contributing to noise levels in the higher part of the spectrum, particularly above 10kHz. For bottlenose dolphins, the ferry would appear unlikely to cause disturbance on acoustic grounds. In keeping with this, comparison of bottlenose dolphin sightings data before and since the commencement of the ferry service found no discernible change in the timing or frequency of dolphin activity in the study area. However, this was very much a preliminary short-term study and further data are required before firm conclusions can be made.