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Counting horseshoe crabs

May 24, 2012 — Wearing sneakers and rain boots, University of Delaware freshmen got their feet wet as marine biologists recently while counting horseshoe crabs along the Delaware Bay. The students participated in a monitoring effort to gain firsthand experience in field research with their fellow marine science majors.

After receiving training in April through the Delaware Bay Horseshoe Crab Spawning Survey, two dozen students gathered in the evening at the St. Jones Reserve in Dover and dispersed to nearby beaches with an experienced volunteer leading each group.

Thousands of horseshoe crabs lined the shores at high tide, congregating into clumps and slowly creeping along the sand in search of mates. The females lay small, round green eggs in the sand as males attach themselves to their backs for fertilization.

The students took a one-meter square made of PVC pipe and laid it on the sand at the “crab line” where the animals gathered, counting how many horseshoe crabs of each gender were within the quadrat. They repeated the process every 20 meters until they covered 1,000 meters of shoreline.