Nature's unlovely lovers enjoy moonlight trysts


Continuity: During the full moon in late May or early June, horseshoe crabs -- little changed in their 300 million to 500 million years on Earth -- take part in a majestic spawning ritual.

May 31, 2002|By Tom Horton | Tom Horton,SUN STAFF

ON SUNDAY, as travelers by the hundreds of thousands thronged Maryland and Delaware resorts, a few dozen waited on less-popular beaches to travel back in time hundreds of millions of years.

It happened shortly after dawn, as the moon set on the Miles River near St. Michaels; late that afternoon on the Potomac in Virginia; and on Delaware Bay, two hours after the full moon rose.

It was the annual emergence of Limulus, the horseshoe crab, crawling up to spawn on sandy beaches, peaking around high tide on the full moon in late May or early June.

Chesapeake Indians called the horseshoe seekanauk, and used its spiky tail to tip lances. It is more closely related to spiders than to true crabs, and less related to anything of this earth than to an epoch 300 million to 500 million years ago, when its order, the Xiphosura, or sword-tailed animals, arose.

The slow-moving, helmet-shaped creatures, which range the Atlantic Coast, are remarkably little changed from fossil ancestors that began crawling onto beaches 150 million years before dinosaurs appeared.

Theirs is a ritual as old as the appearance of grass and trees on the earth, predating the formation of continents. To witness them emerging at night on a lonesome beach -- sand, sea and moonlight the only other elements in the scene -- is as close as you'll get to a primordial time.

Phone calls from correspondents on the Miles and the Potomac said the crabs were coming up by the hundreds there, which meant Delaware Bay, the epicenter of horseshoe spawning, would be a sight to behold.

I met Bill Hall at the south end of Bowers Beach just before high tide, about 10:30 p.m. Hall, a marine education specialist with the University of Delaware, is among those who warned in recent years that the horseshoe crab was in deep trouble.

Each spring and summer, he and other volunteers conduct a census of 24 spawning beaches on the bay's Delaware and New Jersey shores. In 1990, the crab counters estimated up to 1.4 million horseshoes during peak spawning time.

In recent years, the counters estimated as few as 200,000. The problem began when commercial fishing vessels began to target horseshoe crabs along the mid-Atlantic coast a decade or so ago.

The crabs, especially egg-laden females, were sawn into pieces and sold as bait to eel, crab and conch fishermen. Commercial landings doubled in the 1990s, then doubled again.

Only recently have alarms by people like Hall finally been heeded. The federal government has closed crabbing in 1,500 square miles of ocean from Maryland to New Jersey, and coastal states have embraced stricter limits on crab harvests.

Even so, Hall says, it will take at least 20 years for the horseshoe population to recover. It takes a decade or more for females to become mature, and then many more years of spawning to bring the species back.

The beach Sunday night lies before us, a crescent of sand bathed in moonlight, stretching a mile or more. The gently lapping surf seems paved with cobblestones, the dark, mounded shapes of thousands of horseshoe crabs coming ashore.

Hall walks quickly, stopping twice every 20 meters to place a grid of PVC pipe, one meter square, in the surf, counting the male and female crabs within it. He will do 100 grids.

Compared with previous years, his counts are low, six to 18 crabs to a grid. Still, only two grids of a hundred, covering more than a half mile of beach, have no spawning crabs.

The males, he says, have been patrolling just offshore since last month, awaiting the females, each bearing up to 90,000 eggs. As the females crawl ashore, the smaller males clasp onto the rear of their shells.

We watch a big female bulldoze a depression into the wet sand, depositing her eggs. She drags the male into position and fans her gills, sucking water and sperm onto the eggs. Covering them with sand, male still in tow, she disappears back into the bay.

The real pressure to save the crabs came from bird-watching groups such as the National Audubon Society. Huge migrations of shorebirds arrive here each spring, dependent on pecking crab eggs from the beaches to fuel the rest of their northward trip.

More pressure came from an industry that collects blood from the crabs without killing them. (Copper-based, the blood is royal blue, unlike the iron-based blood of most creatures.) The blood is processed into a substance, worth $15,000 a liter, used to detect bacterial contamination in drugs before they can be marketed.

Soon a synthetic substitute for this will be on the market, Hall says.

I wonder, without the spectacular bird migrations to prod us, would we ever protect the drab old horseshoe crab just for itself? Or would we, for the sake of eel bait, go on threatening one of nature's oldest rituals under the moon?

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