EXPLORING RESTORATION METHODS FOR THE OLYMPIA OYSTER OSTREA LURIDA CARPENTER, 1864: EFFECTS OF SHELL BED THICKNESS AND SHELL DEPLOYMENT METHODS ON SHELL COVER, OYSTER RECRUITMENT, AND OYSTER DENSITY

Oysters provide habitat, sediment stabilization, and improved water quality, and are important foundation species in many estuarine ecosystems. Worldwide oyster population declines have been dramatic and efforts to restore declining populations and the services they provide are ongoing. Several commonly used oyster restoration techniques were examined to determine which would be the most successful for restoring the Olympia oyster Ostrea lurida in Newport Bay, CA. Replicate (n = 5) 232 m shell beds were constructed of two initial shell planting thicknesses (bed thicknesses of 4 versus 12 cm) and two methods of deployment (bagged versus loose shell). Shell cover, oyster spatfall (settlement), oyster recruitment, and adult oyster densities were analyzed over 2 y; 12-cm-thick oyster beds maintained higher shell cover, experienced less sedimentation, and received greater numbers of oyster recruits than 4-cm-thick beds. There was no significant effect of shell deployment method on shell cover, recruitment, or adult density; however, spatfall was greater on loose shell beds compared with bagged shell beds in the final year of the study. Overall, augmenting mudflat habitat with oyster shell significantly increased adult O. lurida oyster density compared with unmanipulated plots and increased oyster density relative to the average density of oysters measured elsewhere in Newport Bay. Collectively, the data suggest that building thicker shell beds might increase the longevity of a constructed shell bed, and therefore, this approach is recommended for future restoration activities in southern California. This study highlights the advantages of augmenting habitat in a manner that provides vertical relief from sedimentation.