Effects of Oyster Restoration Techniques On Olympia Oyster (Ostrea lurida) Density, Mussel Density, And Shell Loss In Newport Bay, CA

Oysters are important bivalves in estuarine ecosystems because they provide habitat for other animals, stabilize sediments, and may improve water quality. We examined which of several restoration techniques would be most effective for restoring the Olympia oyster, Ostrea lurida, in Newport Bay, CA by constructing replicate (n=5) 2m X 2m shell beds of 4 treatment types of two thicknesses (4cm versus 12cm) and two levels of consolidation (bagged versus loose shell). We hypothesized that thick oyster beds would show the greatest increase in oyster density, and would lose less shell % cover; but level of consolidation would not have any effect. We analyzed shell loss and densities of oysters and mussels that colonized the beds after 1 year by removing all shell in a 25cm X 25cm area of each oyster bed, sorting out all live bivalves, and identifying each to species. There was no significant difference in the density of Ostrea lurida adults among treatments, but there was a dramatic increase in density relative to control plots. Ostrea lurida settler and non-native Musculista senhousia densities were greatest on thick, bagged plots; Mytilus galloprovincialis density was greatest, and shell loss was less, on 12 cm thick plots. Thick, loose shell plots appear to maximize oyster success while minimizing shell loss and non-native success.