Assessing cetacean occurrence using SoundTraps in offshore areas from the West coast of Kerry, Ireland

Blanca Ferriz

Irish waters are used by a wide range of cetacean species all under strict protection within the EEZ. Static Acoustic Monitoring techniques have become routine as it is an effective and un-intrusive tool for assessing presence and habitat use by cetaceans in these waters. In this study, acoustic recordings from SoundTraps deployed at two offshore areas off Co. Kerry during the Summer and Autumn were analysed to identify presence and occurrence of odontocetes as well as assessing the presence of anthropogenic noise such as that from vessels. A high presence and occurrence of both cetaceans and vessel noise was found across the sampling period. Vocalisation rates significantly varied across diel cycle and between locations and peak frequency varied across diel cycle. Dolphins shifted whistle frequencies and duration when vessel noise was detected. Odontocete communication may be important at certain times of the day within these areas and a possible impact exists in these waters from anthropogenic noise. Highly similar mean parameters were found between locations, suggesting the same species of dolphin occurs at both sites. These parameters were very similar to previous descriptions reported for short-beaked common dolphins and bottlenose dolphins but were different to those reported in bottlenose dolphins from an in-shore resident population in Ireland, suggesting the detections off Co. Kerry are of Common dolphins or coastal bottlenose dolphin populations are not the resident dolphins from the nearby SAC.