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If it's high tide and a full moon, horseshoe crabs are looking for love

Horseshoe Crabs FWC.png
Diane Flowers, St. Marks Lighthouse
/
FWC Fish and Wildlife Research Institute
Horseshoe crab patrols that find and document the state's crab population are expanding into Miami-Dade County and looking for volunteers.

When the moon is right and the tide is high, beaches up and down Florida become a favorite haunt for a certain prehistoric arthropod looking for love.

Horseshoe crabs congregate along the beaches every spring and fall. Since 2015, Florida wildlife officials and the University of Florida's Sea Grant program have been organizing volunteer patrols to help count and tag them. The patrols have helped document hotspots in Brevard County. Their work leads to better understanding behavior and recording the variables that might determine beaches critical for having babies.

Those patrols are now expanding into Miami-Dade County for the first time and in search of volunteers.

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“The frequency and the abundance of the crabs differ in terms of location,” said Ana Zangroniz, the Miami-Dade extension agent for the University of Florida’s Sea Grant program. “You wouldn't think of Miami-Dade as having a ton. But with every person that I've contacted about the upcoming training event, they said, 'Oh, that's so neat because I've seen horseshoe crabs here.' ”

The event Saturday at Crandon Park’s North Beach will be an introductory session to sign up volunteers and introduce them to techniques for identifying and tagging the crabs.

Volunteers need to be at least 16 and available for daytime patrols during high tides.

Zangroniz promises the crabs will delight.

“These are really nifty creatures,” she said. “Their spiky tail — their telson — is just their little lever that they use to right themselves if they get flipped over. They're so interesting. These predate dinosaurs.”

In places like Delaware where they come ashore in the hundreds of thousands, they provide critical food for migrating shorebirds who need to fuel up.

Pharmaceutical companies also rely on their bright blue blood to ensure that injectable drugs and vaccines, like the COVID-19 shots, are safe. The copper-based blood clots when it encounters bacteria that can contaminate drugs.

“The three B’s that my colleagues have identified are birds, bait and biomedical,” Zangroniz said. “That helps you remember the food for the shorebirds, bait in different fisheries and then, of course, that blue blood.”

By having patrols count the crabs in locations around Key Biscayne and Matheson Hammock Park, Zangroniz said scientists can build on information from other patrols and better understand what role Miami-Dade shorelines play in their behavior. That information can lead to decisions on how to better protect breeding grounds.

“We're hoping to get beyond those anecdotal reports and start really counting and documenting. And it can't be done with just a handful of people,” she said. “We need to build a mini army.”

For more information, email Zangroniz at azangroniz@ufl.edu or call (305) 421-4017. Saturday’s meeting begins at 9 a.m. at Crandon Park North Beach in Key Biscayne.