The use of New Quay bay by the resident bottlenose dolphins

Project Start - 2004 / Project End - 2004

Collaborators: University of Wales, Bangor, Cardigan Bay Marine Wildlife Centre, West Wales Chartering Company and Sea Watch Foundation

The use of New Quay Bay, within the Cardigan Bay candidate Special Area of Conservation, by the resident bottlenose dolphins (Tursiops truncatus) was investigated by visual and acoustic means.

A land-based visual survey conducted from May 1st to August 7th 2004 and a T-POD acoustical survey conducted from June 14th to August 7th 2004 were used to investigate which natural factors affect the presence of the dolphins and also the possible impact of boat traffic in this area.

A total of 497 hours of visual data and 1077 hours of acoustic data were collected. Comparisons of the two data sets were made to determine any potential differences between the two techniques. Both bottlenose dolphin presence and boat traffic were found to peak in August. Dolphin presence throughout the day varied inversely with boat traffic. Peak use of the bay by dolphins was at midnight, whereas greatest boat traffic was observed at 1pm. The tidal cycle was significantly correlated with bottlenose dolphin presence, indicating greater presence during the ebb phase of the tide as compared to the flood phase.

The reaction of dolphins during boat interactions varied significantly. Most encounters resulted in the dolphin either changing its behaviour or disappearing from view. Fast moving boats such as motorboats and speedboats appeared to cause greatest disturbance to the animals. Visual and acoustic methods revealed broadly similar patterns in most instances. The combined use of both techniques compensated to an extent for the drawbacks inherent to each survey.

Precautionary measures such as codes of conduct for marine vessels may help to reduce disturbance experienced by bottlenose dolphins and other marine wildlife, due to increased boat activity in the area. Further study is necessary to determine any long-term impacts of disturbance caused by boat traffic.