To achieve the effective conservation of cetacean populations, it is necessary to identify critical breeding and foraging habitats. Acoustic methods provide the opportunity to obtain long-term data on the spatiotemporal distribution of cetaceans. In this study, static acoustic monitoring was used to examine trends in the presence and foraging of bottlenose dolphins and harbour porpoises in Ballyheigue Bay, Brandon Bay and the Maharees, three sites near the Lower River Shannon SAC in Ireland. Brandon Bay was found to be a site of particular importance for both species, with harbour porpoise and bottlenose dolphin presence on 89% and 92% of days monitored respectively. Bottlenose dolphin foraging occurred on 20% of all recorded hours and harbour porpoise foraging occurred on 31% of all recorded hours at Brandon Bay. Diel, tidal cycle, tidal phase and month were all found to be significant drivers of presence in species-specific and site-specific combinations, while foraging was influenced by diel and month. Although bottlenose dolphins and harbour porpoises co-occurred at the study sites, their presence was temporally partitioned. This study highlights the utility of acoustic methods in determining the drivers of cetacean presence and foraging and further acoustic monitoring of Brandon Bay is recommended.
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