Effects of ATOC Sounds on the Harbor Seal, Phoca Vitulina Richardsi, in Monterey Bay
MOSS LANDING MARINE LABS CA
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The purpose of this study was to determine any effects of ATOC signals low frequency sounds on the diving behavior and heart rate of harbor seals near Point Sur, California. Harbor seals n149 92 males, 57 females were captured in Elkhorn Slough, California between June 1994 and November 1996. To determine diving and foraging behavior, time-depth-recorders TDRs and radio tags were placed on 33 harbor seals and 19 also outfitted with heart rate monitors. Radio-tagged harbor seals occasionally moved from Elkhorn Slongh to haul-out sites at Ano Nucvo, Monterey, Point Lobos. Yankee Point, and Point Sur, all returned to the slough. Harbor seals fed on the oceanic shelf, along the shelf break of the Monterey Submarine Canyon, and off Sunset State Beach. Twenty-eightTDRs were recovered n16,403 dives, more dives were recorded at night mean574 dives than daytime mean337 dives. There was no difference in the duration or depth of dives between daytime and nighttime. Harbor seal dives sometimes exceeded 500 m depth and 30 min duration. Because of variable heart rates and the behavior of seals we were unable to determine if there was any effect of the ATOC-like sounds projected toward harbor seals underwater. Based on transmission loss, depth of dive, and distance harbor seal occur from shore, we concluded there is negligible chance that harbor seals would be affected by the ATOC sound source on Pioneer Seamount.