Distributions of harbor seals (Phoca vitulina) relative to tidal currents during summer at Yellow Island, Washington

Abstract

Harbor seals (Phoca vitulina) are fish predators that are commonly found in coastal waters of the Pacific Northwest. They are frequently seen swimming or hauled out during lower tides on rocks in the San Juan Islands during the summer months. I studied associations of swimming seals with tidal currents of different speeds. To do this, I observed a group of seals off the west coast of Yellow Island in the northern San Juan Channel at various intervals during a two-week period in August 2011. Near one particular haul out site, seals appeared to prefer slower currents during low tide when differences in adjacent current speeds were greater than during higher tides. Seals swam near this site more than near any other overall. Seals swam more during late afternoon hours, and mother seals and their pups were associated mainly with slower currents near shoreline.