Spawning Horseshoe Crabs, Adam’s Point, May 2023 (Photo: Bettina Sietz)

Horseshoe crab spawning season is upon us and Great Bay staff and volunteers are excited to get back in the field with one of our favorite species! To protect and preserve our horseshoe crab populations, daily spawning surveys are conducted throughout May and June to count all the horseshoe crabs that come to the water’s edge to breed at high tide. Unlike populations elsewhere, Great Bay’s horseshoe crabs do not face pressure from commercial fishing operations. This means that they act as a ‘control group’ that can be referenced when comparing to other populations, like those in Massachusetts, that experience active fishing. This way, scientists can determine what stressors, like over-harvesting or climate change, could be having an impact on horseshoe crabs in New England and beyond. For more information on horseshoe crab ecology, check out Horseshoe Crab 101

Spawning surveys are crucial to the management of horseshoe crab populations. To prepare for these surveys, Great Bay staff and partners set up transects at the six monitoring sites around Great Bay. With the help of Drs. Chris Chabot (Plymouth State University) and Win Watson (University of New Hampshire), we hosted an educational lecture and volunteer training for everyone interested in helping us monitor our horseshoe crab populations this season! With over 80 people attending the educational lecture and 50 people joining us for volunteer training, it was a truly remarkable turnout. We could not do this without our volunteers, thank you to all who showed up in support of Great Bay’s horseshoe crabs! If you missed the event or want to enjoy it again, a recording of the lecture can be found on our YouTube page.

We’re looking forward to another successful horseshoe crab monitoring season and can’t wait to share our results with the community! For more information on how to become a volunteer, please contact Great Bay’s volunteer coordinator Melissa Brogle at

Tessa Corsetti, Great Bay NERR Biologist