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1 March 2009 Geographic Distribution and Intertidal Population Status for the Olympia Oyster, Ostrea lurida Carpenter 1864, from Alaska to Baja
Maria P. Polson, Danielle C. Zacherl
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Despite the recently renewed interest by ecologists and government agencies to reestablish historical populations of the Olympia oyster, focus has been limited to projects located at the north of this species' range, with little or no attention to southern California and Baja populations. In addition, historical information on the status of natural populations across the range has been mainly qualitative in nature, with no comprehensive information on the current status of natural populations. The focus of this study was to conduct the first large-scale quantitative biogeographic survey of remnant populations of the Olympia oyster and to identify suitable sites in southern California for future restoration projects. We surveyed intertidal populations at 24 historical sites during spring and summer 2005 and summer 2006, established presence/absence and collected data on densities and percent cover. Average maximum densities ranged from 0.0–36.7 ± 12.1 oysters per 0.25 m2. In southern California, intertidal populations were present in all bays and estuaries south of Morro Bay and most showed evidence of regular recruitment. Thus, all southern California sites could present favorable opportunities for restoration projects. At the north end of the range, intertidal populations were more often absent from sites, though there was evidence of subtidal populations. Populations were absent from intertidal sites at the northern endpoint of its distribution in Sitka, Alaska. We speculate that the current northern range limit of this species is located in northern British Columbia. Intertidal populations were also absent at two CA sites, Morro Bay, and Big Lagoon; anecdotal evidence further suggests that subtidal populations were also absent. This study represents the first comprehensive biogeographic survey of intertidal populations of the Olympia oyster, Ostrea lurida, and identifies sites in southern California as suitable locations for future restoration projects.

Maria P. Polson and Danielle C. Zacherl "Geographic Distribution and Intertidal Population Status for the Olympia Oyster, Ostrea lurida Carpenter 1864, from Alaska to Baja," Journal of Shellfish Research 28(1), 69-77, (1 March 2009).
Published: 1 March 2009

Native oyster
Olympia oyster
Ostrea conchaphila
Ostrea lurida
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