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Volume

113

Issue

1

First Page

1

Last Page

13

Abstract

Range and movement data from boat-based photo-identification surveys of Pacific coast common bottlenose dolphins (Tursiops truncatus), carried out over a 6-yr period from 1996 to 2001, were collated and analyzed. Primary data sources were from surveys carried out in four Southern California Bight study areas: Ensenada (12 surveys), San Diego (95 surveys), Santa Monica Bay (170 surveys) and Santa Barbara (61 surveys). Additional data from surveys in Monterey Bay between 1990 and 1993 (84 surveys) were also included in some analyses. Photographic matches between the San Diego, Santa Monica Bay and Santa Barbara study areas ranged from a low of 42% to a high of 67% and averaged 53%. In addition, 32 of the 58 individuals (55%) identified in Monterey Bay also occurred in one or more of the four Southern California Bight study areas. Back-and-forth inter-study area movements recorded between 1996 and 2001, were exhibited by 157 of the 246 (52%) individuals sighted in two or more study areas. Minimum travel distances ranged from 104 to 965 km, with one individual documented to have traveled from Ensenada to Monterey Bay. The most rapid travel speed was 94.5 km/day. These results reinforce earlier characterizations of coastal bottlenose dolphins being highly mobile and capable of rapid travel along the Baja California and the southern and central California Pacific coastline. It is hypothesized that these extensive movements are related to fluctuations in local, regional and perhaps Pacific-wide oceanic conditions that affect prey productivity and availability; combined with unique foraging strategies that have developed to meet these environmental fluctuations.

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