The Horseshoe Crab

A Keystone Species

Overview
The Atlantic horseshoe crab (Limulus polyphemus) is a keystone species in the Delaware Bay region, supporting multiple ecosystems and industries important to human health and livelihood. Each spring, the beaches of the Delaware Bay play host to the largest concentration of spawning horseshoe crabs in the world. Over the course of the spawning season, female horseshoe crabs may deposit as many as 100,000 eggs before returning to deeper waters. This event draws the attention of many visitors from across the country and around the world.
Estimated Population of Mature & Newly Mature Horseshoe Crabs in the Delaware Bay Region by Year
The management of horseshoe crabs in the Delaware Bay region is overseen by the Atlantic States Marine Fisheries Commission (ASMFC). Two methods have been used to determine population estimates. The preferred method is a large trawling effort conducted by Virginia Tech's Department of Fish and Wildlife Conservation (VA Tech), which was designed specifically for monitoring the abundance of horseshoe crabs. However, in years where the VA Tech survey was unable to be performed, population estimates have been determined using a composite index (Composite) created from the DNREC Division of Fish & Wildlife's Delaware Bay Trawl Survey and New Jersey Department of Environmental Protection's Delaware Bay and Atlantic Ocean trawl surveys.
Learn more about this data, horseshoe crabs, and related species management from the ASMFC.

Page reviewed 12/3/18