Under European legislation, developers of Marine Renewable Energy installations are required to undertake an Environmental Impact Assessment to consider the potential impact of development. Two years of baseline data on the seasonal occurrence and distribution of sensitive marine species was conducted at the WESTWAVE wave energy test site, Co. Clare, Ireland. Monthly strip transect aerial surveys were conducted for seabirds and marine mammals, while monitoring for cetacean species was also undertaken using static Passive Acoustic Monitoring (PAM). A total of 6519 seabirds were recorded across 1644 sighting events. Seabird ‘hotspots’ were concentrated coastally in summer, reflecting the distribution of seabird colonies and limited foraging range during the breeding season. Only 31 sightings of marine mammals were recorded during aerial surveys. However, PAM detected regular occurrences of dolphins throughout the year, while harbour porpoise were detected infrequently in the area. Results suggest that construction and decommissioning of MRE installations can be timed to minimize impact on sensitive marine species occurring in the area.