Can habitat restoration be redundant? Response of mobile fishes and crustaceans to oyster reef restoration in marsh tidal creeks

Expectations of ecological and fisheries benefits of habitat restoration are commonly used to justify its high financial cost; however, few empirical studies that rigorously test these expectations exist. Here, we describe the results of a study designed to quantify the effects of restoring oyster reefs in marsh tidal creeks on the mobile macrofauna. We used a before/after control/impact (BACI) design in which fishes and crustaceans within 6 tidal creeks were sampled 7× before and 14× after the addition of live oyster reefs to 3 of the tidal creeks. We detected no significant effects of the addition of oyster reefs on the overall fish or crustacean assemblages within the tidal creeks, and a weak positive effect on the abundance of demersal fishes. These results challenge current predictions that restoration of oyster reefs will result in an increase in mobile fauna. Our findings of no increase in mobile fauna may have resulted from the functional redundancy of a nearby biogenic habitat because reefs were placed in tidal creeks that were surrounded by dense salt marsh. We conclude that a positive correlation between mobile fauna and oyster habitat is not automatic, and that the role of the surrounding landscape is important in predicting the response of transient fish and crustaceans to oyster reef restoration.