Pinniped Abundance and Distribution and the Effects of Tidal Phase and Bathymetry in the San Juan Channel during Fall 2012
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In the San Juan Archipelago two species of pinnipeds are abundant: Phoca vitulina, the harbor seal, and Eumetopias jubatus, the Steller sea lion. This study focused on the pelagic environment where pinnipeds are believed to be feeding. The strip transect method was used on both large and fine scales to determine the effects of tides and bathymetry on pinniped abundance and distribution. Populations have been stable for the past eight years for both species in the channel. Harbor seals were found throughout the channel, but distributional patterns changed on coarse scales. Steller sea lions were concentrated in the southern part of the channel in close proximity to their haul out site. Fine spatial and temporal transects showed little correlation between harbor seals and tidal phase or bathymetry. Steller sea lions were present in the water during faster currents, especially with floods. They also showed a relationship with the bathymetric effect. This study will allow for further research on the relationship of pinnipeds and tides.