By Toni Rose Tablante, Habitat Restoration Technician
The American Littoral Society has wrapped up another horseshoe crab season on the Delaware Bay and it was an eventful one. Let’s recap!
But first, some background: the Delaware Bay is home to the largest population of spawning Atlantic horseshoe crabs, (Limulus polyphemus). The horseshoe crabs come ashore to spawn and lay eggs during the months of May and June, with peak spawning occurring during new and full moon events at high tide.
A female horseshoe crab can lay up to 4,000 eggs at a time, and up to 80,000 eggs per season. Horseshoe crabs are keystone species, playing a very important ecological role. Migratory shorebirds, like the threatened Red Knot, (Calidris canutus), use the Delaware Bay as a stopover during their migrations from the tip of South America to the Canadian Arctic. They rely heavily on the easily digested fats and nutrients found in horseshoe crab eggs to regain weight and fuel their continuing migration.
The Littoral Society continues to fight for the protection of horseshoe crabs, while working to restore spawning habitats.
Our annual monitoring effort includes collecting data for use in assessing movement and behavior in horseshoe crabs, along with gauging our habitat restoration success and supporting the U.S. Fish and Wildlife Service’s Cooperative Tagging Program.
We gathered on Cooks Beach in Cape May County, NJ and Thompsons Beach in Cumberland County, NJ, home to some of our restoration sites along the Bay.
The start of the season was a bit slow due to cooler water temperatures and freshwater mixing from storms that came in at the end of April. We had to wait for high tide to recede a couple of nights, but once it did, the crabs were up!
Some nights were illuminated by the full moon and some left dark with nothing but stars in the sky. Some nights were buggy, and some nights we had a great breeze. Some nights we had to wade through water due to coastal flooding, and others left the marsh dry. All of this added to the fun adventure of these events which allowed us to encounter the horseshoe crabs in their true habitats.
Many groups came to contribute to our tagging efforts this season including the AmeriCorps Watershed Ambassadors, Woodstown High School, Adventure Aquarium staff, and various Scout troops. A special thanks to all our volunteers near and far, including those from Alaska and California!
With the help of our 284 Delaware Bay volunteers, we were able to tag a total of 2,600 horseshoe crabs this season!
The Fun Didn't Stop There
Mixed in with our horseshoe crab tagging nights were also days and nights spent monitoring a restoration project at Money Island in Downe Township, Cumberland County, NJ. The beach restoration project completed last year included sand placement, plantings, and five stone breakwaters.
This was our second year surveying horseshoe crabs and monitoring the structures for any impinged horseshoe crabs and beach usage. So far, the breakwaters do not appear to pose a problem for horseshoe crabs.
At night, we implemented a tagging, quadrat, and resight survey. We deployed 500 tags in total for this survey over the course of two moon cycles – one around the full moon in May and one around the full moon in June. We counted crabs using a 1-m2 quadrat placed randomly to gauge beach usage in front of the breakwaters vs. past the breakwaters.
I still have to analyze this data, but anecdotally it seems the horseshoe crabs were favoring the beach in front of the breakwaters. We also recorded a good amount of previously tagged crabs!
Several of our nights were met with really high tides, where the only road leading to Money Island would flood. With the help of our Delaware Bay Restoration Corps interns, we rescued several horseshoe crabs that had found themselves on the main road!
Diamondback terrapin (Malaclemys terrapin) activity was high at Money Island as well. We encountered multiple females laying eggs on the beach and rescued those that were on the road.
Saving the Best for Last
Let’s talk about our exciting new partnership and project!
In May, we embarked on our partnership with the Cape May Point Science Center, in anticipation of their grand opening. Through this partnership, we teamed up with Cellular Tracking Technologies to take our horseshoe crab research to the next level.
We added cellular tracking devices to our horseshoe crab tagging program! This has been made possible thanks to our gracious donors, Rob and Wendy Wilson.
Our main goal is to track the behavior and movement patterns of female horseshoe crabs, especially before spawning. To gather this data, tags which transmit radio telemetry data are affixed to the horseshoe crab’s shell. Whenever the crabs come ashore, their location is tracked and recorded.
To start this pilot study, only 25 horseshoe crabs were tagged. Preliminary data has shown that the crabs tend to come ashore just after high tide events and that they can move to different beaches for spawning. One tagged crab moved 500 meters south from Reeds to Cooks Beach from one night to the next!
Stay tuned for more exciting updates as we uncover more data from our radio-tagged horseshoe crabs.
So, this concludes another horseshoe crab season for me as #ToniRoseExplorestheBayshore. I felt more confident navigating May through June, having a previous season of experience under my belt. As always, I had a blast engaging with our volunteers while teaching them about one of my favorite creatures! I’m also looking forward to continue learning about horseshoe crabs, through our monitoring efforts and new radio tagging project.
If you would like to hear more about our work, please check out the following links, which feature my co-workers, Quinn Whitesall McHerron, Habitat Restoration Coordinator; Shane Godshall, Habitat Restoration Project Manager; and Tim Dillingham, Executive Director.
If you enjoyed tagging and would like to continue to support the work we do in the Delaware Bay region, please consider a donation to the American Littoral Society or becoming a member.
If you are interested in tagging in 2024, or have any other questions please contact Quinn at email@example.com or Toni Rose at firstname.lastname@example.org.