Abstract
Restoration efforts with native eastern oyster, Crassostrea virginica, in Chesapeake Bay and elsewhere have been limited by shell availability, necessitating the use of alternative structures as subtidal reefs, yet these have rarely been evaluated quantitatively. We quantified population structure, density, abundance and biomass of eastern oyster and hooked mussel, Ischadium recurvum, on a concrete modular reef (75 m2 surface area over 5 m2 of river bottom) deployed subtidally at 7 m depth in the Rappahannock River, Virginia during October, 2000. After nearly 5 y (May 2005), we took 120 stratified random samples over the reef. The reef was heavily colonized by 28-168 oysters and 14-2177 mussels m-2 surface area. These densities translate to 1085 oysters and 8617 mussels m-2 river bottom, which are the highest recorded for artificial oyster reefs. Size structure of oysters reflected four year classes, with over half of oysters more than 1 y old and of reproductive age. Oyster biomass (1663 g dry mass m-2 river bottom) and condition index were equally high, whereas parasite prevalence and intensity were low. Oyster density correlated positively in a sigmoid fashion with mussel density up to high densities, then declined. This modular reef is one of the most successful artificial reefs for eastern oyster and hooked mussel restoration, and details features that are conducive for successful settlement, growth and survival in subtidal habitats.
Highlights
Native oyster reefs have been functionally extirpated worldwide [1, 2]
Oyster density was significantly higher on the top Face, at 159.1 individuals m-2 surface area, than on all other faces (Fig 5; Tukey HSD test, p < 0.0001), which did not differ significantly from each other (Tukey HSD test, p > 0.70) and whose average densities were below 60 individuals
The key findings of our study, which we believe is one of the most thorough evaluations of subtidal artificial oyster reefs [16, 17], relate to reef features that are most conducive for successful settlement, growth and survival of the eastern oyster and hooked mussel in subtidal habitats
Summary
Native oyster reefs have been functionally extirpated worldwide [1, 2]. In North America the native eastern oyster (Crassostrea virginica) along the Atlantic and Gulf of Mexico coasts and Olympia oyster (Ostrea lurida) along the Pacific coast have declined by 88% in biomass and by 64% in reef area over the past 200 y [2]. Successful performance of a subtidal artificial reef for eastern oyster and hooked mussel in Chesapeake Bay of Marine Science, College of William & Mary. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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