Quick Facts About Horseshoe Crabs and Red Knots

Horseshoe Crabs at Port Mahon, Delaware Bay, May 2007, by Mike Parr, ABC

Horseshoe Crabs at Port Mahon, Delaware Bay, May 2007, by Mike Parr, ABC

  • The horseshoe crab evolved in the early Jurassic Period, 200 million years ago. It predates the first birds by some 50 million years.
  • The relationship between shorebirds, particularly the Red Knot, and horseshoe crabs in Delaware Bay goes back 10,000 years or more. The birds rely on the abundance of crab eggs to fuel their northerly spring migrations to their Arctic breeding grounds.
  • Horseshoe crabs were once harvested for fertilizer and animal feed. More than 50 million were killed before 1920.
  • The blood of horseshoe crabs contains a chemical used to test the purity of medicines. Thousands of crabs are caught each year to take blood for this purpose. The crabs are returned to the sea unharmed.
  • Since the mid-1980s, horseshoe crabs have been harvested for use as bait in conch and eel pots. Insufficient take restrictions led to huge declines in the Atlantic horseshoe crab population. Fewer crabs meant fewer eggs and a commensurate decline in the populations of the rufa subspecies of the Red Knot.
  • Historically, more than 100,000 Red Knots stopped at Delaware Bay. By 2004, this number had dropped to 13,315.
  • ABC has worked to protect the Red Knot and other shorebirds by protecting the horseshoe crab. Thanks to the efforts of ABC and its partners, stricter regulations on the take of horseshoe crabs have been imposed for the Atlantic States. A no-take sanctuary has been established at the mouth of Delaware Bay, and moratoriums have been set in Delaware and New Jersey, halting all take of horseshoe crabs for two years in those states.
  • ABC has also worked to promote bait bags. Reusable nylon mesh pouches that reduce the amount of crab bait needed in conch pots by up to 50%.
  • ABC and others have sued the federal government to have the rufa Red Knot protected under the Endangered Species Act.