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Red Knot and Horseshoe Crabs

The Delaware Bay is critical habitat to more than 400 species of birds and migrating shorebirds. In fact, the Delaware Bay “is one of the most important stopover sites in North America for long distance migratory shorebirds.”  Each spring, at least 11 species of birds, including the red knot rufa, stop over on the Delaware Bayshore to feed on the eggs of the horseshoe crab and thereby fuel their annual spring migration.

The red knot rufa, based on its precipitous decline, has been identified as a candidate species for listing under the Federal Endangered Species Act and was proposed on January 18, 2011 for listing as endangered under New Jersey’s Endangered and Nongame Species Conservation Act. In August 2011 the USFWS will begin the listing determination process for the Red Knot.

Available scientific studies clearly indicate a large decline in shorebirds that is directly linked to decreasing shorebird weights and their decreased ability to feed themselves with horseshoe crabs eggs when they arrive along Delaware Bay beaches during their spring migration. Horseshoe crab numbers are at historic lows, resulting in low abundance and availability of horseshoe crab eggs for migratory shorebirds. Additionally, the bio-medical industry that is vitally important to the health and safety of the country also depends upon healthy populations of horseshoe crabs for the irreplaceable substance found only in horseshoe crab blood. As crabs take 7-10 years to mature, we have a long way to go before historic densities of eggs will once again be found on the beaches of the Delaware Bay. We cannot afford actions and decisions that set this trajectory back.

Peak counts of red knots on the Delaware Bay stopover have declined by 70% since 1998. Other shorebirds that rely on horseshoe crab eggs, such as ruddy turnstone, semipalmated sandpiper, sanderling, dunlin and short-billed dowitcher have also declined in number on the Delaware Bay migratory stopover. During the period from 1998 to 2007, all of these species declined by approximately 64%. The ruddy turnstone declined by a severe 82%. In 2010, ruddy turnstone numbers were among the lowest ever recorded, a mere 18,231. The sanderling declined by 61% and the short-billed dowitchers suffered a decline of 74%. These species, together with red knots, make up 99 percent of the shorebird concentration in Delaware Bay. All are dependent upon horseshoe crab eggs for all or most of their diet during the stopover, and all have significantly declined in population.

In 1982, 95,530 red knots were counted on the shores of the Delaware Bay. In 2010, only 14,475 were observed during the same time period.  Regarding horseshoe crabs in the Delaware Bay, the Delaware Trawl Survey shows no significant trend of increase; neither does the Virginia Tech Offshore Trawl Survey. According to the “Status Update for the Red Knot” issued April 2011, juvenile horseshoe crab abundance in 2010 declined and “There is no evidence of a significant increase in the mature horseshoe crab population in the Delaware Bay Spawning Crab Survey, the Delaware 30-foot Trawl Survey or the Virginia Tech Benthic Trawl Survey.

In New Jersey, egg densities have not improved and have remained low in the 2005 to 2010 time frame. Similarly, in Delaware, egg densities also did not improve and to the extent there was a trend in egg density it was “non-significant and negative.” At a minimum, a density of 50,000 eggs/sq. meter over 50% of suitable spawning beaches is needed to allow red knots and other shorebirds to begin to recover. All beaches surveyed from 2005 to 2010 in DE and NJ were below this threshold, except for Mispillion Harbor in DE. As a result the beaches are unable to support recovery of the diminishing shorebird populations or to support a population if it were recovered.

Much of the recreation and culture of the New Jersey Bayshore is linked to the spawning of the horseshoe crabs and the annual arrival of the migratory shorebirds, including the red knot. The arrival, feasting and migration of the shorebirds supports a multi-million dollar ecotourism industry. Birding and outdoor enthusiasts from all over the world flock to the Delaware Bay shore to watch the spectacular feeding frenzy. During their visits, they buy recreation-related goods and services, stay in the region’s hotels, visit parks and patronize restaurants and local shops. According to one report, horseshoe crab-dependent ecotourism generates between approximately $7 million and $10 million of annual spending in Cape May, New Jersey alone, and creates 120 to 180 related jobs, providing an additional $3 million to $4 million in social welfare value.According to a New Jersey Department of Fish and Wildlife report, the economic value of the horseshoe crab and migratory bird phenomenon seasonally for the Delaware Bay shore area is over $11.8 million with over $15 million of economic value generated if other beneficiaries beyond New Jersey are included. Annually, it provides $25 million in benefits to the Delaware Bay shore region and $34 million regionally. Because most of these expenditures occur in the “off-season”, they are particularly valuable to local economies.

The continuing existence of the horseshoe crab and migrating shorebird phenomenon is vital for the related ecotourism industry. Of those surveyed, only 6.6% said that the horseshoe crab and shorebird phenomenon was unimportant to their visitor satisfaction. On average those surveyed said they would be willing to pay as much as $212.45 (in decreased annual household income) annually for a program to protect these resources; and that they would “be willing to tolerate no more than 50.7% decline in Horseshoe Crabs and migratory shorebirds before they would cease visiting the Delaware Bay shore area.”

In response to the dramatic declines, the red knot rufa is a candidate species for listing as endangered under federal law (in 2014 the US F&W Service was taking steps to give the red knot the status of threatened). It is also proposed for listing as endangered in New Jersey. The listing of the red knot will necessarily require increased and ongoing protections of their stopover habitat – the beaches of the Bayshore. It will also necessitate ongoing protection of their primary food source when they land here – the eggs of the horseshoe crabs. Other birds that have been in decline may not yet be federally or state listed, but the ecological and economic effects of their declines have a major impact on the region.

The Delaware Riverkeeper Network has been working hard for almost two decades to protect the horseshoe crabs of the Delaware Bay from over harvesting as well as projects like the Army Corps' Delaware River Deepening project and its associated spoil disposal plans which are also a major threat to the continuation of this historic and vital Delaware River population.

For decades, the Delaware Riverkeeper Network along with our colleagues and folks from around the region, country and world have struggled to protect the horseshoe crabs of Delaware Bay from their continuing decline and to protect the shorebirds dependent upon them from going extinct as a result of that decline. 

In 2010 we had a huge success; New Jersey passed a moratorium on the harvest of horseshoe crabs until such time as the birds dependent upon them could be deemed to have recovered (as opposed to going extinct which is the path they were on). 

The science shows we do not have an increase in the horseshoe crab eggs needed for shorebird recovery. And yet, a New Jersey Legislator, Assemblyman van Drew, wants to lift that moratorium. 

The horseshoe crabs are not only vital for the shorebirds, but they provide an irreplaceable substance necessary for testing vaccinations and medical devices to ensure they are safe for human use (the substance is, in most cases, drawn without killing the crabs and allows their return to the natural environment.). The crabs and birds are also the mainstay of a tens of millions of dollar ecotourism industry vital for sustaining our communities.

Update as of 5.14.2014

The US Fish & Wildlife Service is finally taking steps to list the Red Knot as Threatened under the Endangered Species Act in response to the petition submitted by the Delaware Riverkeeper Network and petitions from others.  Delaware Riverkeeper Network continues to urge for the designation of endangered while we support at least a designation of threatened.  Comments are now open for you to also urge the FWS to list the red knot as Endangered and go above and beyond the "Threatened" designation - you can take action on Delaware Riverkeeper Network's urgent action page until mid June 2014. 

Take a moment, watch our video to learn more about the crabs and the birds and then sign the petition to state your opposition to this cavalier and senseless removal of vital protection.

View a video from May 2014 showing horseshoe crab tagging with the Delaware Riverkeeper Network and efforts for volunteers to take part in citizen science to help the crabs and shorebirds.

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