Every spring, an amazing phenomenon occurs in the Delaware Bay. Thousands of shorebirds known as red knots migrate from Terra del Fuego South America to the shores of Delaware and NJ for one purpose. They are ravenous. On the menu: horseshoe crab eggs. Around the full moon in May, horseshoe crabs make their way to the sandy beaches, bury their eggs, and return to the Bay. Simultaneously, red knots are arriving on the same beach, digging with their long, pointed beaks looking for these eggs. In order to make the second half of their arduous journey, the red knots need to double their weight before they leave the Bay. The extraordinary relationship that exists between these ancient crabs and their feathered friend is one of dependence and resilience.
Horseshoe Crabs
The Delaware Bay region is home to the largest population of the American horseshoe crab. The horseshoe crab belongs to the large group of invertebrates (animals without backbones) called Arthropods . This group also includes lobsters, crabs, insects, spiders, and scorpions.
In the early 1900s, horseshoe crabs were used as fertilizer and poultry food supplements before the advent of artificial fertilizers. Presently, they are used as bait for eels and conks and for medicinal purposes. Horseshoe crab's blue blood is copper-based and is used to test the purity of medicines for the presence of gram-negative bacteria. Certain properties of the shell have also been used to speed blood clotting and to make absorbable sutures.
In the late 1990s, concerns over horseshoe crab numbers made headlines and efforts to regulate the harvest numbers began. In 2000, the Atlantic States Marine Fisheries Commission (ASFMC), who is the regulatory body charged with coordinating conservation and management of Atlantic Coastal state's marine life, implemented a 25% harvest reduction from all coastal states.
As the years passed and the ASFMC began to implement increasingly stringent regulations, the horseshoe crab population began to rebound. Currently, the ASFMC allows a capped harvest of 100,000 male only crabs in Delaware. In 2008, New Jersey placed a moratorium on horseshoe crab harvests until the red knot numbers rebound.
Every year, DNREC hosts volunteer training for horse shoe crab monitoring. Click for more information and to volunteer for the .
Red Knots
In 1980, the Delaware Bay was recognized as the critical stopover location for 6 shorebirds; the rufus population of the red knot, ruddy turnstone, sanderling, semipalmated sandpiper, dunlin, and the short-billed dowitcher . It is estimated that over 1 million shorebirds use the Delaware Bay as a stopover in the spring months.
Arriving from Tierra del Fuego and southern Argentina, 33% to 50% of the red knot population uses Delaware Bay as a staging site for up to 2 weeks. Red Knots rely almost solely on horseshoe crabs which are easily digested and metabolize into fat and protein; useful when traveling to their breeding grounds in the Arctic. During the 1990's, scientists discovered the direct correlation between plummeting of the horseshoe crab numbers and the Red Knot population. In 2000 after almost 15 years of surveying spring migrations of shorebirds, scientists found that weight gains for shorebirds were down 50% . In 2003, the Red Knot numbers were just over 16,000.
As a result of the Red Knot Status Assessment in the fall 2006, the U.S. Fish and Wildlife Service announced the Red Knot warranted threatened status. In April 2007, Canada's Committee on the Status of Endangered Wildlife classified the southern wintering population endangered, and Florida & Brazil populations as threatened. In 2007 and 2008, Delaware, with encouragement from environmental groups, attempted to implement a moratorium on horseshoe crab harvests for 2 years, to allow Red Knot numbers to rebound. However, the moratorium was overturned through litigation and Delaware instead complied with the minimum standard recommended by the ASFMC.
As of 2008, the Red Knot population was down to 14,800, declining from a high of more than 100,000 birds in the 1980s. Without Endangered Species protection, the fate of the Red Knot is uncertain and could face the threat of extinction.
