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Open Access Publications from the University of California

Pinniped ecology in Santa Monica Bay, California


We investigated pinniped ecology at sea in Santa Monica Bay, California. Animals were studied during 277 boat-based surveys conducted in 1997-2007 documenting that California sea lion Zalophus californianus was the most observed species (89%, n sightings = 1393), followed by harbor seal (Phoca vitulina richardsi: 8%, n sightings = 131), and northern elephant seal (Mirounga angustirostris: 1%, n sightings = 15). Sea lions, and occasionally harbor seals, were found in aggregations with bottlenose dolphins Tursiops truncatis in 29% of the sightings (n bottlenose dolphin sightings = 205), short-beaked common dolphins Delphinus delphis and long-beaked common dolphins D. capensis in 53% of the sightings (n common dolphins = 155). Sea lions and harbor seals were regularly observed in coastal waters (shore) but also in the entire bay, with both species showing a preference for submarine canyons. Northern elephant seals were only seen in offshore waters and mostly in proximity of the canyons. The three species were frequently observed traveling (50%, n = 728), thermoregulating (14%, n = 205), and feeding (3.2%, n = 47) but rarely socializing (.21%, n = 3). This is the first long-term study on at-sea distribution, occurrence, frequency and behavior of pinnipeds in Santa Monica Bay [Acta Zoologica Sinica 54 (1): 1-11, 2008].

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