Harbor porpoises (Phocoena phocoena) are often observed in Oregon’s nearshore marine environment, yet knowledge of their ecosystem use and behavior remains limited. This lack of knowledge is generating concerns for potential impacts on this species from future coastal development.
Passive acoustic monitoring was used to investigate the spatial and temporal variations in the locations and foraging activity of harbor porpoises off the Oregon coast from May through October 2014. Digital monitoring devices (DMONs) were deployed to record acoustic data in two neighboring, but bathymetrically different locations off the Oregon coast. One was a site in close proximity to a rocky reef. The other site was on an open sandy environment. Data were analyzed with respect to two dynamic cyclic variables: diel and tidal phase.
Porpoise presence at the rocky reef site was aligned with the ebb phase of the tidal forcing, while, harbor porpoise presence and foraging at the offshore, sandy bottom site was associated with nighttime foraging. The spatial and temporal patterns identified in this study suggest harbor porpoise habitat use is modulated by specific environmental conditions particular to each site that maximize foraging efficiency.
Authors: Holdman, Amanda K.; Haxel, Joseph H.; Klinck, Holger; Torres, Leigh G.