Spawning Stock Composition of Horseshoe Crabs Collected from the Coast of Maryland, USA

The Atlantic coast horseshoe crab Limulus polyphemus population is of interest to numerous stakeholders.  Horseshoe crabs play an important role in estuarine ecosystems and human health and serve as a primary bait source for other commercial fisheries.  The U.S. Fish and Wildlife Service began administering a tagging program for horseshoe crabs in 1999, distributing tags and maintaining a tag return database for use by various management and research entities.  As part of the program, 50,026 tagged horseshoe crabs were released off the coast of Ocean City, Maryland between 1999 and 2013 by a cooperating biomedical firm.  Between 2000 and 2013, 1,229 tagged animals have been reported by the public and 394 tags have been resighted during spawning surveys by horseshoe crab researchers.  We summarize the apparent movement patterns and describe the proportions of crabs that subsequently spawned in Delaware Bay as well as in the coastal bays of Maryland, Delaware, and Virginia during subsequent spawning seasons.  Since the Delaware Bay spawning stock of horseshoe crabs is managed separately from the rest of the coastal stocks, this information on composition of offshore aggregations in the mid-Atlantic region is important for informing deliberations on harvest management and quota allocations.