The Nature Conservancy - Jurassic Beach

Crabs count: Data gathered by volunteers help to manage the crab population, which was threatened by overfishing for bait and biomedical use.

Go Deeper

Sidebar: Delaware's Dinosaur
The American horseshoe crab is an ancient species whose closest relative—the trilobite—died out more than 250 million years ago.

Delaware Bayshores
More than a million migratory shorebirds depend on the horseshoe crabs converging on Delaware beaches each year.

Upper Management

The horseshoe harvest was largely unregulated until 1999. Since that time, federal and state catch limits and protected areas have been established, including a 1,500-square-mile horseshoe-crab reserve at the mouth of the Delaware Bay, where no commercial fishing of horseshoes is permitted. In 2006, New Jersey and Delaware announced a two-year moratorium on horseshoe harvesting. Because of these efforts, the harvest declined by 70 percent between 1998 and 2006.

But efforts to restore the crab and regulate its catch have been complicated by a lack of solid population data. Without a crystal-clear picture of the threats to the crab, industry groups have been able to overturn or water down harvest limits. Last year, watermen won a lawsuit overturning Delaware’s moratorium on horseshoe harvests, arguing that harvesting 100,000 male crabs in the state’s waters would not undermine conservation efforts.

“The question is, how do you manage the harvest?” says Hall, who is sympathetic to the challenges of the fishing community. He explains that it takes the relatively long-lived horseshoes 9 to 12 years to reach maturity and start spawning. “Any time you have something that takes 10 years to mature sexually, you have to look ahead 10 years to what you’re harvesting,” he says. This makes the horseshoe crab especially difficult to manage, since it can take years to see if conservation efforts are working—and even longer to gauge the ripple effects on species that depend on the crab.

Even if the crab harvests are set right, it’s not clear whether the horseshoes can quickly recover their numbers, warns U.S. Geological Survey horseshoe researcher Dave Smith. “We’re not sure there’s enough food for the horseshoes to bring them back to their peak levels,” he says, pointing out a decline in marine worms and mollusks that the crabs depend on for food.

That’s where the volunteer effort to count the crabs comes in. The participation of thousands of people like Bob Brozek who have collected data in the past decade is beginning to fill in gaps about how to manage the crab sustainably. “And as long as we have data that is reliable and applicable, then management is going to be successful,” says Hall. The latest census and other studies find that the crab population is no longer dropping and has, in fact, stabilized. “Several surveys indicate that the population may be increasing,” says Smith. “But it’s too early to be definite.”

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