Prime Hook National Wildlife Refuge

Site Description

  • State: Delaware
  • County: Sussex
  • Ownership: Federal


  • Unit 2: 1555 acres
  • Unit 3: 3501 acres
  • Unit 4: 145 acres

Ecology and Management

Prime Hook National Wildlife Refuge has three coastal impoundments totaling 4,200 acres of freshwater wetland habitat that undergoing a managed transition to salt marsh habitats. Due to Prime Hook’s strategic location on the Delaware Bay, the refuge has national conservation significance as a designated RAMSAR Wetland of International Significance Site (1999), American Bird Conservancy-Important Bird Area (2000), and a Western Hemisphere Shorebird Reserve Network site (1986).

Breaches to Unit II impoundment.

After experiencing numerous breaches to the dunes which separate Units I & II in 2006, 2008, and 2009 the last of which resulted in the loss of over 1,000 acres of marsh, refuge staff began to explore options to allow the freshwater impoundments to transition to salt marsh. As this process was going on Hurricane Sandy caused two more breaches in Unit II. Based on extensive hydrodynamic modelling as well as public outreach Prime Hook NWR decided to move forward with a two-phase restoration of all impoundments to the original salt marsh habitats. The first phase was recently completed with a large-scale nourishment of the dune systems to protect the impoundments in the short term. The second phase is ongoing and includes the creation of tidal channels to improve circulation throughout the refuge and allow the impoundments to begin their ecological transition.


As the repeated breaches have shown the impoundments are highly vulnerable to extreme storms and sea-level rise. The transition to salt marsh will result in habitats that are more resilient to these impacts of climate change. Additionally, the improved water circulation that will be achieved through the restoration efforts will decrease flooding in communities and the marsh vegetation will buffer the effects of future storm surge.

Human Value

Prime Hook NWR receives approximately 85,000 visitors every year, most of whom come to observe wildlife. The refuge also hosts a number tours, lectures, festivals and other educational and community events throughout the year. Prime Hook NWR has partnered with the University of Delaware on a monitoring program and also host education trips for K-12 students as well as having staff visit local schools.

Literature Resources

Below is a list of articles describing research occurring at or near the impoundments:
  • AFSBSPT [Atlantic Flyway Shorebird Business Strategy Planning Team]. Hurricane Sandy Rapid Assessment – Final Report. Manomet, MA: Manomet Center for Conservation Sciences; 2013.
  • ALS [American Litoral Society]. Assessing the impacts of Hurricane Sandy on coastal habitats. Highlands, New Jersey: American Littoral Society; 2012.
  • Anderson, J. T. 2006. Evaluating competing models for predicting seed mass of Walter’s millet. Wildlife Society Bulletin 34:156-158.
  • Breese, G., K. Kalasz, J. Lyons, C. Boal, J. Clark, M. DiBona, R. Hossler, B. Jones, B. Meadows, M. Stroeh, B. Wilson, and M. Runge. Structured decision making for coastal managed wetlands in Delaware. Shepherdstown, West Virginia: United States Fish and Wildlife Service, National Conservation Training Center; 2010.
  • Chamberlain, E. B. A survey of the marshes of Delaware. Dover, Delaware: The State of Delaware, Board of Game and Fish Commissioners; 1951.
  • Chan, S., and S. Shulte. A Plan for Monitoring Shorebirds During the Non-breeding Season in Bird Monitoring Region Delaware – BCR 30. Manomet, Massachusetts: Manomet Center for Conservation Sciences; 2003.
  • Conroy, M. J., G. R. Costanzo, and D. B. Stotts. 1989. Winter survival of female American black ducks on the Atlantic coast. The Journal of Wildlife Management 53:99-109.
  • Coppola, A. Prime Hook National Wildlife Refuge Comprehensive Conservation Plan. Hadley, Massachusetts: U.S. Department of the Interior, Fish and Wildlife Service; 2013.
  • DDNREC [Delaware Department of Natural Resources and Environmental Control]. Prime Hook NWR – Wetland management challenges – background information. Dover, Delaware: Delaware Department of Natural Resources and Environmental Control; 2012.
  • Erwin, R. M., D. K. Dawson, D. B. Stotts, L. S. McAllister, and P. H. Geissler. 1991. Open marsh water management in the mid-Atlantic region: aerial surveys of waterbird use. Wetlands 11:209-228.
  • Giroux, J., G. Gauthier, G. Costanzo, and A. Reed. 1998. Impact of geese on natural habitats. Pages 32-57 In Batt, B. D. J., editor. The Greater Snow Goose: report of the Arctic Goose Habitat Working Group, US Fish and Wildlife Service and Canadian Wildlife Service, Washington, DC and Ontario, Canada.
  • Green, A., J. Lyons, M. Runge, W. Kendall, H. Laskowski, S. Lor, and S. Guiteras. Timing of impoundment drawdowns and impact on waterbird, invertebrate, and vegetation communities within managed wetlands, Study manual – Final version field season 2007. Laurel, Maryland: USGS Patuxent Wildlife Research Center; 2007.
  • Green, A. W., W. L. Kendall, H. P. Laskowski, J. E. Lyons, L. Socheata, and M. C. Runge. Draft version of the USFWS R3/R5 Regional Impoundment Study. Washington, D. C.: U. S. Fish and Wildlife Service; 2008.
  • Hossler, R., K. Bennett, and A. Kane. Coastal Impoundment Decision Making. A presentation given at Connect, Collaborate, and Conserve in an Era of Changing Landscapes: An Interactive Training on State Wildlife Action Plans, June 4-6, 2013. Washington, D.C.: Association of Fish & Wildlife Agencies.
  • IWMM [Integrated Waterbird Management and Monitoring Project]. Project Update – October 2010. http://iwmmprogram.ning.com/: Integrated Waterbird Management and Monitoring Project; 2010.
  • Kane, A. Practical guidance for coastal climate-smart conservation projects in the Northeast: Case examples for coastal impoundments and living shorelines. Montpelier, Vermont: National Wildlife Federation; 2011.
  • Murray, M., and J. Montgomery. 2012. Marsh impoundments create questions on future responses by state officials. Delaware Online October 23, 2012:1.
  • Neckles, H. A., J. E. Lyons, G. R. Guntenspergen, W. G. Shriver, and S. C. Adamowicz. 2015. Use of Structured Decision Making to Identify Monitoring Variables and Management Priorities for Salt Marsh Ecosystems. Estuaries and Coasts 38:1215-1232.
  • Sherfy, M. H., and R. L. Kirkpatrick. 2003. Invertebrate response to snow goose herbivory on moist-soil vegetation. Wetlands 23:236-249.
  • Sherfy, M. H., R. L. Kirkpatrick, and K. D. Richkus. 2000. Benthos core sampling and chironomid vertical distribution: implications for assessing shorebird food availability. Wildlife Society Bulletin 28:124-130.
  • Stevens, H., and A. Trembanis. 2012. Stabilizing the Forgotten Shore: Case Study from the Delaware Bay. Pages 267-281 In Cooper, J. A. G., and O. H. Pilkey, editors. Pitfalls of Shoreline Stabilization, Springer, New York.
  • Stroeh, M. Wetland management along a changing coast: a manager’s dilemma. A presentation given at the Delaware Wetlands Conference. Dover, Delaware: Delaware Department of Natural Resources and Environmental Control; 2012.
  • Wilson, B., D. Siok, C. Pinkerton, K. Smith, and B. Scarborough. Evaluating the Evolution of Natural Tidal and Managed Wetlands in Delaware. A presentation given at DE Wetlands Conference. Dover, Delaware: Delaware National Estuarine Research Reserve; 2012.