An ecosystem approach for oyster restoration and management

In addition to supporting a harvest, the eastern oyster (Crassostrea virginica) in Chesapeake Bay provides ecosystem services such as removing seston, enhancing water clarity and creating benthic habitat. Our objective was to create a flexible ecosystem-based decisionmaking tool to support oyster restoration and management. This Oyster Restoration Optimization model (ORO) incorporates predictions from three-dimensional water quality (NPDZ with oyster filtration) and larval transport models; calculates sizeand salinity-dependent growth, mortality, and fecundity of oysters; and incorporates economic costs of restoration efforts. An optimization approach is used to identify the most suitable locations for oyster population restoration that maximize one or more benefits such as reduction in seston, increase in light penetration, spawning stock enhancement, and harvest, subject to cost constraints and other limitations. The iterative solution technique incorporates and estimates uncertainty such as that caused by climate variability. Preliminary results indicate that the restoration of oysters in three sub-systems of the Chesapeake Bay would maximize different suites of benefits due to interactions between salinity gradients, salinity-dependent growth and mortality rates of oysters, the residence time of water in the sub-systems, and the relationship between size of oysters and the number of bushels harvested. The strengths and constraints of the ORO model as applied to ecosystem-based fisheries management are discussed.