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Horseshoe crabs are crawling on restored Fowler Beach — and that's good for threatened birds

In 2012, Hurricane Sandy blew through Fowler Beach at Prime Hook National Wildlife Refuge, tearing it apart.

 

By October 2016, most of a federal restoration project restoring 4,000 acres of the refuge was complete — repairing 25 miles of tidal channels and the damaged shoreline - making them more resilient to future storms. 

 

One of the benefits of a restored beach? A treasure-trove of horseshoe crabs as far as the eye can see.

 

 

It’s evening during the summer solstice — the longest day of the year – when Laura Mitchell, Dan Stotts and their two boys Ian and Travis are walking along Fowler Beach in Sussex County. They’re counting the horseshoe crabs on a 1,000 meter stretch of restored sand.

 

They walk 20 meters. Then they lay a white square called a “quadrat” down on the sand. They record how many horseshoe crabs are in or near the perimeter. Then, they repeat, until they hit 1,000 meters.

 

“Two females, 17 males!" Laura calls out to Dan, who records the number on a data sheet.

 

Laura and Dan counted 131 crabs as part of their sample. That number will help scientists estimate whole populations and track changes in the species’ numbers over time.

 

Here at Fowler Beach, that data is more than just numbers on a ledger, Laura said.

 

“This is something that’s important for the Delaware Bay, it’s important for the estuary, it’s important for the shorebirds, and we want to show that we’ve had a drastic increase in the populations,” Laura said.

 

Dan said if they’re lucky enough, they’ll see some shorebirds, like red knots, that feed on horseshoe crab eggs. He points out a small oystercatcher as it darts across the sand and listens to the sounds of dozens of gulls.

 

Laura and Dan both work for the U.S. Fish & Wildlife Service. The federal agency received $38 million in funding to restore 4,000 acres of the refuge to withstand storm damage.

 

“This. Was. Not. Here a year ago. None of this was here!” Laura said. “This is material that came from an offshore dredge area that they calculated very carefully and had enough material to basically recreate this beach. So we’re walking on something that was under Delaware Bay a year ago.”

 

Restoration crews finished repairing the back barrier of the beach and the dune in 2015, infusing the new beach with 1.4 million cubic yards of coarse sand. The tidal channels were finished in June 2016.

 

Al Rizzo led the restoration project for U.S. Fish and Wildlife. He said research from Delaware’s Department of Natural Resources and Environmental Control pointed to horseshoe crabs spawning better on coarse grains.

 

Before the restoration, the refuge had fine sand which is more erodible, as seen in when Hurricane Sandy and subsequent storms hit.

 

“When the beach was gone and actually blown out, it actually created flood shawls, so we didn’t have a contiguous beach anymore, we had little remnants of the beach. The crabs would get sucked into the impoundments in the incoming tide and get trapped,” Rizzo said.

 

Rizzo said after the damage was done, they weren’t seeing the number of horseshoe crabs they historically had seen. 

 

 

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Credit Katie Peikes / Delaware Public Media
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Delaware Public Media
Horseshoe crabs are spawning at Fowler Beach

 

According to numbers from the U.S. Fish & Wildlife, Fowler Beach recorded an average of .78 female crabs per meter squared per night. In 2014, staff recorded .17 female crabs per meter squared per night. In 2015, no spawning surveys were done due to access issues on the beach.

 

There isn’t much of a comparison they can make yet because the spawning surveys are now being done on a new stretch of beach. Fish & Wildlife Supervisory Wildlife Biologist Susan Guiteras said the surveys before 2017 were done on Fowler Beach in the area just north of the restoration.

 

"Based on the limited surveys done in the two years since the beach was restored, horseshoe crab numbers on Fowler Beach appear to be recovering to levels at or above the numbers seen in the area in recent years, prior to restoration,” Guiteras wrote in an email. “It will take more time and analysis to be certain that this is in response to the restoration. But, biologists on staff have been surprised and excited to see horseshoe crabs in such high numbers this quickly.”

 

She later added, “These numbers are very encouraging but time is gonna tell whether it’s a trend and going back up.”

 

Now, with Fowler Beach restored, plenty of horseshoe crabs are spawning and there are plenty of eggs. That increases the possibility that red knots will show up here. The shorebird has been considered threatened under the Endangered Species Act.

 

“We hope to see red knots, but ruddy turnstones, sanderlings, other shorebird utilize the eggs,” Rizzo said. “But one ancillary benefit we’re starting to see is — now that we have piping plovers that are threatened on the the federal threatened list, gulls are actually feeding on the horseshoe crabs that get stranded so it kind of lures them away from the actual predation of the chicks.”

 

So the returning horseshoe crabs have a key role to play, a role Travis and Ian Stotts described on the drive home from the spawning survey.

 

“The horseshoe crabs are part of the ecosystem, and without that part of the ecosystem, it all collapses,” Travis Stotts said. “And also, the horseshoe crabs have been around here for a long time — 300 million years, and if they weren’t here, then more problems than you would expect would probably show up.”

 

“It’s like a domino effect. One creature goes out, the creatures that depend upon it go out,” Ian Stotts said.

 

With a restored Fowler Beach in place, it appears that the ecosystem can again count on the creature that outlived the dinosaurs to do its part.