Floating Oyster,Crassostrea virginicaGmelin 1791, Aquaculture as Habitat for Fishes and Macroinvertebrates in Delaware Inland Bays: The Comparative Value of Oyster Clusters and Loose Shell

Abstract

The substantial decline of eastern oyster (Crassostrea virginica) stocks along the east coast of the United States has prompted the growth of many types of restoration and enhancement efforts. One of the most recent types is oyster gardening. Oysters grown in floating structures are subsequently planted in bays, where they continue to live, grow, and spawn; filter the water; contribute to the larval pool; and provide habitat. Our study is one of the first evaluations of habitat value provided by floating oyster gardens in a degraded mid-Atlantic estuary. Oyster growth and survival within the floats was monitored in a eutrophic, turbid, periodically hypoxic, soft-bottom coastal lagoon system. We examined the abundance and diversity of fishes and invertebrates with respect to 3 replicated treatments: live oyster clusters, disarticulated oyster shell, and a float with no shells or oysters. We also studied the effects of 2 cleaning frequencies (biweekly and monthly) on species assemblages, and the growth and survival of oysters, and monitored basic water quality parameters. The species assemblages in floats with oyster clusters were very similar to those with loose shell but considerably different than that of empty floats. Cleaning frequency (biweekly and monthly) did not affect the growth or survival of oysters. Location of floats within the canal system, however, was a large determinant of oyster vital rates as well as community structure. Forty-nine species of fishes and invertebrates, and 8 species of macroalgae were collected from floating oyster gardens, including 9 commercial or recreational fishery species, many of which are likely habitat limited in the Inland Bays because of the loss of tidal wetlands, oyster reefs, and seagrass beds. Newly settled juvenile oysters have been found for the first time within the floating oyster gear in the manmade, residential canal systems. Our results will be used to gauge the success of enhancement efforts and to improve our understanding of the effects oyster gardens on the Inland Bays ecosystem.