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Structured Decision MakingApplied to Red Knot Conservation
Northeast Region, October 30, 2009
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Red Knot (Calidris canutus) at Delaware Bay
Red Knot (Calidris canutus) at Delaware Bay - Photo Credit: n/a
Horeshoe crabs (Limulus polyphemus) spawning at Delaware Bay
Horeshoe crabs (Limulus polyphemus) spawning at Delaware Bay - Photo Credit: n/a

  Delaware Bay hosts the largest spawning population of horseshoe crabs in the world and the second largest population of migrating shorebirds in North America. Delaware Bay is designated within the Western Hemisphere Shorebird Reserve Network as having the highest reserve status. In addition to providing the principal food source for migratory birds in Delaware Bay, research indicates horseshoe crabs may comprise the main diet of juvenile loggerhead turtles.

The Delaware Bay is a critical migratory stopover for Western Hemispheric populations of migratory shorebirds, including red knot (Calidris canutus rufa), ruddy turnstone (Arenaria interpres), sanderling (Calidris alba), and semipalmated sandpiper (Calidris pusilla). These migrants depend on the eggs of spawning horseshoe crabs for a major portion of their diets (50 to 90 percent) each spring before migrating from the Delaware Bay beaches to Artic nesting grounds.

Migratory shorebirds on the Delaware Bay beaches declined in the late 1990s and early 200s. Since 2003 the population has been stable based on winter surveys in South America and Aerial Peak Counts in Delaware Bay. The local threats that have been identified include reduced food availability, human disturbance, predation, loss of sandy beaches and suitable roost sites, and risk of oil and hazardous materials spills. The high harvest of horseshoe crabs leading up until the late 1990s has reduced the crab population and may have led to declines in migratory shorebirds including red knot, sanderling, semipalmated sandpiper, and ruddy turnstone.

The issue of meeting the energetic requirements of migratory Shorebirds has driven the controversy over management of horseshoe crab (Limulus polyphemus) populations in the mid-Atlantic region and particularly in Delaware Bay. The ASMFC Horsehoe Crab Fishery Management Plan has multiple goals: 1) sustaining horseshoe crab population levels, 2) providing critical food resources for other species (migratory shorebirds in particular), 3) allowing harvest for bait, and 4) providing continued use for LAL production, which is required for testing the safety of medical supplies World-wide. Even more problematic is the fact that the migratory shorebird populations are dependent on horseshoe crab eggs that are surplus to the needs of the horseshoe crab population.

Recognizing the need for a more integrated approach, the Atlantic States Marine Fisheries Commission has requested technical assistance from the U.S. Fish & Wildlife Service (Service) to provide expertise in shorebird biology and management to their Horseshoe Crab Fishery Management Process. The Service chairs the Shorebird Technical Committee.

In October 2007 the first Joint Meeting of the Horseshoe Crab & Shorebird Technical Committees took place at the National Conservation Training Center. An ARM working Group was formed and in spring 2008 a post doc was hired by USGS to develop the models and decision support structure to complete a Structured Decision Making (adaptive management or SHC) framework for making management decisions on horseshoe crab harvest.  This work was completed and presented to the Joint Technical Committees in fall 2009.  There was lively discussion about a number of issues and the Joint Committee provided a number of recommendations to the ARM workgroup to incorporate into the report. The Report was accepted with changes for peer review, as part of the ASMFC's Formal Stock Assessment Process.

The final report for peer review was completed 16 Oct 2009.  It is currently undergoing peer review.  After the peer review has been completed, recommendations will be evaluated and incorporated as appropriate.  A final report will be presented to the ASMFC Horseshoe Crab Fishery Management Board in early 2010, for use in identifying the best harvest regulations.  Future monitoring will be used to evaluate the modeling and allow learning over time.


Contact Info: Jennifer Lapis, (413) 253-8303, jennifer_lapis@fws.gov
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