In 1990, the first organized survey of spawning horseshoe crabs in the Delaware Bay began. Now, every May and June during the full and new moon evening high tides, volunteers annually donate their time to count crabs on the beaches of the Delaware Bay in both Delaware and New Jersey. Each lunar date is bracketed with surveys occurring on the day of the peak spawning tide, the prior two days, and the following two days.

In October of 1998, The Atlantic States Marine Fisheries Commission (ASMFC) Horseshoe Crab Management Plan adopted an annual spawning survey to be conducted along the shores of Delaware Bay. Considering that a Delaware Bay volunteer spawning survey had been in existence since 1990, the ASMFC opted to continue this volunteer-based survey with additional statistical guidance from the United States Geological Service (USGS).