Habitat use of toothed whales in a marine protected area based on point process models

Abstract

Toothed whales (Odontocetes) are highly mobile animals that play key trophic roles in ecosystems and whose habitats often overlap with areas of human activity. To mitigate detrimental effects of this overlap, it is critical to understand their habitat use patterns. The Stellwagen Bank National Marine Sanctuary in the western Gulf of Maine is a hypothesized foraging area for toothed whale species and an area of high human use, but odontocete habitat use there is poorly understood. While a large whale watch community provides a robust, long-term, opportunistic sighting data set, those data are not standardized. To overcome this limitation, we used point process models to analyze 10 yr of opportunistic sighting data. We identified spatial distribution patterns and environmental predictors for the 2 most common odontocete species in the sanctuary, Atlantic white-sided dolphins Lagenorhynchus acutus and harbor porpoise Phocoena phocoena. Habitat use differed among months, and depth, slope, substrate, and salinity were the most important and consistent predictors for both species. Models identified both persistent and shifting hotspots within the sanctuary. While presence was strongly associated with several covariates, environmental predictors did not fully explain shifting hotspots. This work highlights the importance of long-term opportunistic data collection and provides new knowledge on habitat use to inform assessment and management of potential human impacts on odontocetes in a federal marine protected area.