Would a horseshoe crab harvest ban save the red knot? As scientists who have collectively studied red knots, our response is an unequivocal yes. Horseshoe crab eggs are critical to the red knot's ability to complete their spring migration and reproduce in the Canadian Arctic. Without ample numbers of breeding crabs laying eggs on Delaware Bay beaches, red knots will continue to decline.

For years we hoped that the modest reductions of horseshoe crab harvests would lead to increases in egg densities, especially after New Jersey's 2006 moratorium. Unfortunately, those efforts have been undermined by increased harvests in other states and an increasing number of crabs killed during biomedical use. Let us be clear: the most recent surveys of egg density show no substantive improvement in either New Jersey or Delaware from 2005 through 2010. None of the three measures of horseshoe crab numbers (as opposed to eggs) has shown a significant increase over that period.

This January, the main wintering population dropped by another 5,000 birds. While we understand the importance of research, it is now time for action. The most effective action will be to increase the number of spawning horseshoe crabs through a moratorium on lethal harvest of Delaware Bay origin crabs. The U.S. must recognize that it has a moral and legal treaty obligation to protect the red knot. In the absence of stronger conservation actions, the extinction of this shared migratory species is all but certain.

Allan J. Baker, Toronto

Charles D. Duncan, Portland,Maine

Carmen Espoz Larrain, Santiago, Chile

Patricia M. González, San Antonio Oeste, Argentina

Brian A. Harrington, Plymouth, Mass.

Lawrence Niles, Greenwich, N.J.

Jeannine Parvin,Cape May Courthouse, N.J.

The writers are scientists who have studied the red knot for a collective 130 years