Eastern oyster settlement and early survival on alternative substratesalong intertidal marsh, rip rap, and manmade oyster reef

摘要

Restoration efforts with native Eastern oyster, Crassostrea vir-ginica, in Chesapeake Bay have been extensive and have been impeded by substrate and recruitment limitations along with many other detrimental factors. In Lynnhaven Bay, a southern subestu-ary of Chesapeake Bay, the Army Corps of Engineers has partnered with the Virginia Institute of Marine Science, National Oceanic and Atmospheric Administration, and Chesapeake Bay Foundation to implement a comprehensive oyster reef restoration strategy. Surveys within the Lynnhaven Bay system indicate that artificial oyster shell reefs created in the early 1990s are producing poor to marginal oyster densities relative to densities on nearby granite and concrete riprap, and on oyster clusters along marsh-fringed shores. In this field experiment, twelve treatments simulating inter-tidal oyster habitat were placed at three sites within a tidal creek: adjacent to marsh, rip rap and a manmade oyster reef. Treatments consisted of caged and uncaged trays (0.5 m length x 0.5 m width x 0.25 m depth) of large granite, small granite, large limestone marl, small limestone marl, very small concrete/granite, and oyster shells. Granite of both sizes had the highest initial oyster recruitment across all sites. Overall, replicates showed a distinct recruitment/early survival pattern between sites: marsh > rip rap > artificial oyster reef. We therefore propose that granite may be a favorable oyster reef construction material, since it appears to enhance oyster settlement and early post-settlement survival. Additional biological benefits may accrue from granite reefs as community structure develops on the reefs.