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Virginia Institute of Marine Science

Winter Dredge Survey

The Bay-wide Blue Crab Winter Dredge Survey is an annual cooperative effort between the Virginia Institute of Marine Science (VIMS) and the Fisheries Service of the Maryland Department of Natural Resources (DNR).

The survey, in operation since 1990, allows researchers to

  • Accurately gauge the total population of blue crabs in Chesapeake Bay
  • Identify year-to-year trends in blue crab abundance
  • Characterize the size and sex of individual crabs
  • Estimate over-wintering mortality
  • Understand seasonal migration patterns, and
  • Assess the effects of the crab harvest

The winter dredge survey is the most comprehensive and statistically sound of the blue-crab surveys conducted in the Bay. The Virginia Marine Resources Commission, the  Potomac River Fisheries Commission, and other resource management agencies rely on its findings, along with data on annual fishery removals, to guide their on-going management of Chesapeake Bay’s blue crab stock.

Survey results show that there was a persistent and substantial decline in the spawning stock, recruitment, larval abundance, and female size of blue crabs in Chesapeake Bay between 1992 and 2007. However, management actions initiated in 2008—including a blue crab spawning sanctuary and harvest restrictions—helped the Bay’s blue crab population rebound toward a healthy, sustainable level. In recent years, the stock has again experienced declines. The reasons for these declines are being investigated.