Research Technical Report

Marine Mammals and Seabirds at the Davidson Seamount, July 2010

Newton, K., P. Pyle, E. Burton, C. King, and A. DeVogelaere (April 2011)

Poster presentation at Sanctuary Currents Symposium, Seaside, CA

ABSTRACT

The Davidson Seamount, located 129 km southwest of Monterey, California, was incorporated into the Monterey Bay National Marine Sanctuary in March 2009 and is the first seamount within the National Marine Sanctuary system. The Sanctuary conducted a ship‐based survey of the waters above and around the Davidson Seamount during July 2010. The three‐day survey onboard the R/V McArthur II was the first dedicated at‐sea survey of the Seamount to record marine mammal and seabird observations. Overall, 8 transect lines were surveyed for a total of 605 km of "on‐effort" observations. Seventeen species of seabirds and 6 marine mammal species were observed. Cook's Petrel (Pterodroma cookii) was the most abundant seabird observed (8.4 birds km‐2), followed by Leach’s Storm‐petrel (Oceanodroma leucorhoa; 5.6 birds km‐2). The seabird assemblage to the NW was distinctly different than that to the SE with the NW region characterized by more pelagic species such as Cook's Petrels and Leach's Storm‐petrel while the SE region was characterized by more coastal species such as shearwaters, phalaropes, gulls, and alcids. Of a total of 200 marine mammal sightings, fin whales (Balaenoptera physalus) were the most commonly encountered marine mammal (51% of sightings), comprising 94% of whales sighted. This survey in combination with aerial surveys along the same transect lines will serve as a baseline for future studies of the Davidson Seamount.