Contemporary approaches for small-scale oyster reef restoration to address substrate versus recruitment limitation: a review and comments relevant for the Olympia oyster, Ostrea lurida Carpenter 1864.

摘要

Reefs and beds formed by oysters such as the Eastern oyster, Crassostrea virginica and the Olympia oyster, Ostrea lurida Carpenter 1864 were dominant features in many estuaries throughout their native ranges. Many of these estuaries no longer have healthy, productive reefs because of impacts from destructive fishing, sediment accumulation, pollution, and parasites. Once valued primarily as a fishery resource, increasing attention is being focused today on the array of other ecosystem services that oysters and the reefs they form provide in United States coastal bays and estuaries. Since the early 1990s efforts to restore subtidal and intertidal oyster reefs have increased significantly, with particular interest in small-scale community-based projects initiated most often by nongovernmental organizations (NGOs). To date, such projects have been undertaken in at least 15 US states, for both species of dominant native oysters along the United States coast. Community-based restoration practitioners have used a broad range of nonmutually exclusive approaches, including: (1) oyster gardening of hatchery-produced oysters; (2) deployment of juvenile to adult shellfish ("broodstock") within designated areas for stock enhancement; and (3) substrate enhancement using natural or recycled man-made materials loose or in "bags" designed to enhance local settlement success. Many of these approaches are inspired by fishery-enhancement efforts of the past, though are implemented with different outcomes in mind (ecological services vs. fishery outcomes). This paper was originally presented at the first West Coast Restoration Workshop in 2006 in San Rafael, California and is intended to summarize potential approaches for small-scale restoration projects, including some emerging methods, and highlight the logistical benefits and limitations of these approaches. Because the majority of the past efforts have been with C. viriginica, we use those examples initially to highlight efforts with the intent of enlightening current west coast United States efforts with Ostrea lurida. We also discuss site-specific characteristics including "recruitment bottlenecks" and "substrate limitation" as criteria for identifying the most appropriate approaches to use for small-scale restoration projects. Many of the included "lessons-learned" from the smaller-scale restoration projects being implemented today can be used to inform not only large-scale estuary wide efforts to restore C. virginica, but also the relatively nascent efforts directed at restoring the United States west coast's native Olympia oyster, Ostrea lurida.