Application of a Demographic Model for Evaluating Proposed Oyster-Restoration Actions in Chesapeake Bay

ABSTRACT

A demographic model was developed for oyster populations in the Chesapeake Bay, USA, to explore population responses to proposed management actions in support of an Environmental Impact Statement and Environmental Risk Assessment for oyster restoration. The model indicated that high natural mortality due to disease strongly controlled the population of native Eastern oysters. Continuing restoration effort at recent levels was predicted not to increase oyster populations. An enhanced restoration program that included habitat improvement and stocking would likely increase populations, particularly in areas with lower salinity where disease prevalence was lower. However, population numbers would likely reach a plateau much less than the restoration goal a few years after enhanced restoration efforts ended. A harvest moratorium was predicted to have a smaller positive effect than enhanced restoration. A moratorium likely would take much longer than the 10-year restoration period to meet restoration goals given the present high natural mortality rates. The proposed introduction of non-native Suminoe oysters was not modeled because insufficient data existed with which to parameterize the model. These results were used semi-quantitatively in the Ecological Risk Assessment to evaluate population trajectories and speculate about population changes more than 10 years after implementation of a management action.

Key Words:

• oyster
• demographic model
• Chesapeake Bay
• environmental impact statement
• environmental risk assessment

ACKNOWLEDGMENTS

We thank S. Schroeter, H. Townsend, and J. Stottrup for reviewing this article. The work reported on in the articles in this series was funded by the Maryland Department of Natural Resources, via cooperative agreements with the University of Maryland Center for Environmental Studies, and the Potomac River Fisheries Commission. Work on the ERA and the EIS was conducted in collaboration with the Maryland Environmental Service and performed under the direction and leadership of a management team comprised of Mr. Thomas O'Connell, Maryland Department of Natural Resources, Mr. Jack Travelstead, Virginia Marine Resources Commission, Mr. A. C. Carpenter, Potomac River Fisheries Commission, and Mr. Mark Mansfield, Norfolk District, USACE (CENAO). Technical direction was provided by a Project Delivery Team consisting of representatives of: Norfolk District, USACE (CENAO); Virginia Marine Resources Commission; National Oceanographic and Atmospheric Administration (NOAA); Engineering Research and Development Center, USACE (ERDC); Atlantic States Marine Fisheries Commission (ASMFC); Maryland Department of Natural Resources (MD DNR); Potomac River Fisheries Commission; U.S. Environmental Protection Agency (USEPA); and U.S. Fish and Wildlife Service (FWS). The assessment relied on the considerable research on the Asian oyster that was carried out by individuals at various universities and government research laboratories. Many of those researchers provided insights into data interpretation and reviewed various parts of the assessment. The large number of contributors to the overall program are identified in the various appendices of the Final PEIS and their contributions to this effort are too numerous to summarize in a brief acknowledgment.

AUTHOR-DIRECTED PEER REVIEW

This article was prepared under HERA's author-directed peer review process, wherein an article's authors nominate proposed peer reviewers to HERA's Managing Editor for approval or revision. The following persons reviewed and approved the publication of this article:

•	Steve Schroeter, Ecologist, Marine Science Institute, University of California, Santa Barbara, CA, USA
•	Josianne Støttrup, National Institute of Aquatic Resources, Technical University of Denmrk, Charlottenlund, Denmark
•	Howard Townsend, NOAA Chesapeake Bay Office, Oxford, MD, USA