Static Acoustic Monitoring of Harbour (Phoca vitulina) and Grey Seals (Halichoerus grypus) in the Malin Sea: A Revolutionary Approach in Pinniped Conservation

Harbour and grey seals rely on acoustic signals to mate, socialise and defend their territory. Previous studies have focused on their behaviour, movements and communication from the coast, leaving a knowledge gap in the offshore environments, and therefore being unable to determine the proper use they give to those areas and the risks they face around them. Acoustic data collected with a SoundTrap were analysed to assess the detectability of both species in the Malin Sea. Vocalisations were classified based on aural and visual features, as well as using non-parametric classification trees. Differences in the vocalisation rate of grey seals per diel, season and tidal state were also assessed through Generalised Linear Mixed Models, obtaining significant results, and finding similarities in the vocalisations of grey seals with the Scottish and Irish populations. A small sample of adult and pup harbour seals was detected, and differences in call type and number of detections per type were found across the seasons. These results show the importance of the area for both species, and lay the foundations for future studies, which will help to implement proper conservation measures such as Marine Protected Areas.