MEPS 560:159-171 (2016)  -  DOI: https://doi.org/10.3354/meps11894

ABSTRACT: Ostrea lurida is the only oyster native to the US west coast. Overharvesting and other factors have led to population declines and the extinction of some populations. Despite restoration efforts, the recovery of O. lurida has been weak, and the causes for limited recovery are poorly understood. To be successful, recovery efforts must consider limitations at each stage of the multi-phase life cycle of O. lurida, including pelagic larvae and sessile juveniles and adults. In the Coos Bay estuary, Oregon, the distribution of adult oysters is relatively well known, but larval dispersal and recruitment patterns are not. Using passive larval traps and recruitment plates, we tested the hypothesis that this population is recruitment-limited through low larval availability and/or variable recruitment success within the estuary. We observed high larval availability, low recruitment, and negligible adult populations at riverine-dominated sites located in the inner bay. In contrast, polyhaline sites located in the middle region of the bay had high larval availability, high recruitment rates, and abundant adult populations. Conversely, marine-dominated sites near the mouth of the estuary had negligible larval availability, no recruitment, and adult populations were almost entirely absent. Our results indicate that a sustained population of O. lurida is likely feasible only in the polyhaline region of the Coos Bay estuary. Restoration and enhancement efforts designed to help recover populations of O. lurida should give serious consideration to early life stage characteristics including larval supplies, dispersal, and recruitment, as well as environmental conditions within the bays and estuaries.

KEY WORDS: Ostrea lurida · Olympia oyster · Larval supply · Recruitment · Null zone · Coos Bay estuary