May 28, 2008
Horseshoe Crab Populations Rebounding
Experts are pointing to restrictions in U.S. east coast states on harvesting horseshoe crabs as the cause of the recent surge in the population of endangered migrating shore birds after years of over-fishing.
Horseshoe crabs lay the eggs on the shores of the east coast every spring, and the migratory birds rely on the eggs as a source of food.
Before the restrictions were put in place, commercial fishermen had harvested millions of crabs, which they used for bait while fishing for conch and eel. But ornithologists warned that the red knot was in danger of becoming extinct because of the lack of crab eggs.
In New Jersey, officials set a two-year moratorium on crab harvesting. It was later banned altogether. Meanwhile Delaware only allows the harvest of male crabs.
The population of male crabs on Delaware beaches has now risen to 4.22 per square meter (11 square feet) from 2.50 in 1999, while female numbers have risen to 0.89 from 0.77, said Stewart Michels, a fisheries scientist at the Delaware Division of Fish and Wildlife.
"We are very optimistic that the significant increase is a good sign of things to come," Michels said.
Deleware's crab harvest had dropped to almost 77,000 last year, compared to 487,000 in 1995.
Statistics on the East Coast as a whole, dropped to 817,000 in 2007 from around 3 million in 1995, Michels said.
The number of red knot stopping over on Delaware Bay beaches during their 10,000-mile (16,000-km) migration from south America to Arctic Canada each spring has dropped in recent years to around 15,000, a number that scientists say is below that needed to sustain the species.
Scientists hope that success with saving the red knot will translate into success with other species such as ruddy turnstone and semi-palmated sandpiper, whose numbers have also declined because of the dwindling number of crab eggs.
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Delaware Fish & Wildlife