Marine mammal distribution in the Gulf of Alaska from long-term passive acoustic monitoring

The Gulf of Alaska is an important habitat for a diverse array of marine mammals. Conservation of these populations requires understanding how they utilize different habitats. Passive acoustic monitoring can be used to study marine mammal distributions because the unique call types produced by many species are well documented. Between 2011 and 2015, a total of 3793 days of recordings were collected from autonomous acoustic recorders at five locations broadly distributed around the continental shelf, slope, and offshore seamounts in the Gulf of Alaska. The spatial and temporal patterns of seven cetacean species were examined and differences in habitat use and behavior were compared. Inshore habitats featured higher detections of humpback (Megaptera novaeangliae) and gray (Eschrichtius robustus) whales, while blue (Balaenoptera musculus) and sperm (Physeter macrocephalus) whales were more commonly detected offshore. The presence of most species was seasonal, with peak calling in spring and summer for gray and sperm whales, and fall and winter for fin (B. physalus) and humpback whales. Call type distributions within a species differed spatially for fin and killer (Orcinus orca) whales, and seasonally for blue whales. Spatial differences may indicate prey preferences, while seasonal changes are likely related to behavioral shifts from feeding to mating.