The population of North American red knots has been in the midst of a sharp decline for a decade, falling from over 100,000 in the 1980s to 17,000 last year. This year, the numbers have fallen even further. Aerial surveys around the Delaware Bay have counted only 12,000 red knots.
Increased harvesting of horseshoe crabs has been blamed for this species's rapid decline. Before a sudden boom in the horseshoe crab market, watermen took only about 100,000 crabs per year; at the height of crab harvesting in the mid 1990s, about 2.5 million crabs were taken. Horseshoe crabs are used as bait for conch fishing.
Red knots depend upon a plentiful supply of horseshoe crab eggs when they arrive at the Delaware Bay in the midst of their long migration from the southern tip of South America to their breeding grounds in the Arctic Circle. Their migration is timed to coincide with the spawning of horseshoe crabs, when millions of horseshoe crabs come ashore on the beaches to mate and lay their eggs.