Estimated enhancement of fish production resulting from restoring oyster reef habitat: quantitative valuation

We reviewed studies providing quantitative measurements of abundance of fishes and large mobile crustaceans on oyster reefs and on nearby sedimentary habitat in the southeast United States. For each species, we compared density by size (age) class on oyster reefs and sedimentary bottom as a means of estimating the degree to which restoration of oyster reef on sedimentary bottom could augment abundances. By applying published information on growth rates of each species and a combination of empirical data and published information on age-specific survivorship, we calculated the per-unit-area enhancement of production of fishes and large mobile crustaceans expected from the addition of oyster reef habitat. For this calculation, we gave the reef habitat full credit for the expected lifetime production of species whose recruitment was judged to be limited by the area of oyster reefs based on nearly exclusive association of recruits to reefs. For species that were only modestly enhanced in abundance by oyster reefs, we gave the reef credit for the fraction of production that is derived from consumption of reef-associated prey, using a combination of gut content data and natural history information. This combination of analyses and calculations revealed that 10 m² of restored oyster reef in the southeast United States is expected to yield an additional 2.6 kg yr–1of production of fish and large mobile crustaceans for the functional lifetime of the reef. Because the reef is biogenic and self-sustaining, the lifetime of a reef protected from bottom-disturbing fishing gear is limited by intense storms or sedimentation. A reef lasting 20 to 30 yr would be expected to augment fish and large mobile crustacean production by a cumulative amount of 38 to 50 kg 10 m–2, discounted to present-day value. This set of calculations assumes that oyster reef habitat now limits production of reef-associated fish and crustaceans in the southeast United States. This assumption seems reasonable based on the tight associations of so many fishes with reef-dependent prey, and the depletion of reef habitat over the past century.