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Horseshoe crabs are landing - and the spawn is bringing it on

A horseshoe crab is seen on the beach at South Bowers Beach, Delaware, in this May 17 photo. A census of crab populations has been conducted for 17 ye...
Bill Hall with the University of Delaware Sea Grant Program is seen lifting a male horseshoe crab in this May 17 photo.

A horseshoe crab is seen on the beach at South Bowers Beach, Delaware, in this May 17 photo. A census of crab populations has been conducted for 17 ye...

Bill Hall with the University of Delaware Sea Grant Program is seen lifting a male horseshoe crab in this May 17 photo.

There are the Limulus polyphemus and the people who love them, this for reasons hardly obvious, for they are an ugly lot. Only their name is beautiful.
But love is blind and the horseshoe crab, the common name for the limulus, is not: it has 10 eyes, the better to see down in the deep murk of the Delaware Bay, and to poke above the surface when the tide is high, the moon full, and the beach bright with its light.
At such incandescent moments during the year, but especially in the late spring, they advance upon the bay's many beaches like an invading army, bobbing landward under their green, helmetlike shells.
It's spawning time and before it is all over each female crab, up to 250,000 on a peak night, will have deposited as many as 20,000 eggs in the sand, with the males following behind, fertilizing them.
It is a tender mating ceremony on a beach, which coincidentally has something of a reputation as a lovers' lane or "party beach" for young people in these rural parts.
For the horseshoe, which is not actually a crab, rather a member of the arachnid clan that includes spiders and scorpions, this is a gambit to assure the perpetuation of
a creature that has crawled up through the depths of Earth's narrative. Its ancestors were here before there were dinosaurs, flying insects, flowers, and, of course, humans.
The limulus is found in Maine, Mexico's Yucatan Peninsula, Japan, and the Delaware Bay, which supports the world's largest population.
The specimens awaited the night of May 17 have been around only 35 million to 40 million years, newcomers. They arrived on schedule, but far fewer than expected by the man who counts them.
Bill Hall, a professor at the College of Marine Studies, University of Delaware, was disappointed.
Instead of a great rush to the shore, he counted only 50 males and four females.
"I guess the ladies didn't show up tonight," he said, oddly apologetic to the volunteers who came to help in the count, maybe expecting a massive invasion. These were early samples of the population that reveals itself on beaches on the Delaware and New Jersey sides of the bay.
The counts go on for 12 nights, timed to coincide with the phases of the new and full moons.
Dr. Hall, in khaki waders and head lamp, dropped a meter square made of PVC pipe onto the water's edge, then counted the crabs within it.
He moved 10 meters down the beach, did it again and again, up to 100 times. The same procedure was unfolding on 25 beaches of the bay.
The numbers collected will be tabulated by New Jersey's fish and wildlife service, then sent to state and federal agencies to set fishing quotas for 2009.
The crabs are sought by commercial fishermen for bait to fish for eel and conch, and by pharmaceutical companies for their blue blood, used to test intravenous drugs for bacteria.
The animal can be drained of a third of its blood without harm; those who take it are obliged to return the crab to the waters it was taken from.
In the early 20th century, 4 million crabs were taken annually to grind up as fertilizer, said Hall. And in 1998 alone, 2.7 million crabs were harvested.
By the mid-1990s the overall population had "crashed to about half a million," he said, and the animal seemed headed for extinction, certain to drag other species along with it, especially the birds that live around and visit the Delaware Bay.
Eventually maritime authorities responded.
A crab sanctuary was established off the Delaware Bay, extending 30 miles out to sea, and running south from Atlantic City, New Jersey, to Ocean City, and Midwest Coastal states imposed sharp cutbacks in the harvesting of crabs.


Updated : 2021-07-29 13:12 GMT+08:00