Relationships Between Sandpipers and Horseshoe Crab in Delaware Bay: A Synthesis

Recent and dramatic declines have been documented in several shore-bird Populations that stage in Delaware Bay during spring migration. As a result, considerable attention has been given to issues such as the reliance of sandpipers on Delaware Bay American horseshoe crab (Limulus polyphemus) eggs for refueling and how to best manage the horseshoe crab fishery to insure adequate resources for migratory shorebirds. In this chapter, we synthesize over 25 years of shorebird research and monitoring data in Delaware Bay to support the premise that horseshoe crab eggs are an essential element for migrating sandpipers during northbound passage through the bay. We then discuss long- and short-term trends in American horseshoe crab populations resulting from changes in demand and harvest regulations, and how this has affected shorebird population viability. Regulatory actions have led to recent increases in some demographic elements of the Delaware Bay crab population, but such changes have not yet translated into increased crab egg availability or population recovery indices in shorebirds. Because reduced availability of horseshoe crab eggs has severe consequences for migratory sandpipers at the individual and population levels, current conservation strategies that include harvest reductions on American horseshoe crabs in the Delaware Bay region must persist into the foreseeable future to insure the recovery of horseshoe crab populations and the long-term health of migratory sandpipers in Delaware Bay.