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Weekend full moon brought thousands of horseshoe crabs to Delaware beaches

Courtesy of Oana Turton
Delaware Center for the Inland Bays volunteers conduct a horseshoe crab spawning survey Friday night at Tower Road

Last weekend’s full moon brought hundreds to thousands of spawning horseshoe crabs to some Delaware beaches. 


The Delaware Center for the Inland Bays reported there were more than 1,700 horseshoe crabs seen spawning Friday night at Tower Road, just south of Dewey Beach.



Environmental Scientist Andrew McGowan said volunteers reported about 1,400 males and 300 females spawning there. 


“This was a good sign and that actually happened across most of the beaches on Friday so it was great to see that,” McGowan said.


Typically, McGowan said, environmentalists and beach-goers will see males in much higher numbers than females.


“The more males there are around a female, the better chance that all her eggs are gonna be fertilized, so you want to see more males than females in a spawning population,” McGowan said.


McGowan said horseshoe crab counts had been lower before Friday because of a rainy, colder spring, but he’s hopeful the count will be even higher during the next full moon in the end of June.


McGowan said tracking horseshoe crabs is important because they’re a food source for many migrating shorebirds, like red knots, that are listed as threatened on the Endangered Species Act. 


Last year, the Center for the Inland Bays counted more than 14,000 horseshoe crabs from Tower Road to Coastal Kayak May through June.


The Center for the Inland Bays has had volunteers conduct horseshoe crab surveys since 2008 to make sure this important food source for endangered migratory birds like red knots was not declining to dangerously low levels.