Fishery managers have announced further harvest limits on horseshoe crabs in the Delaware Bay and parts of the Mid-Atlantic Coast to increase protection for shorebird populations.

The Delaware Bay is inhabited by the largest population of American horseshoe crabs. Considered “a living fossil,” the species has barely changed in about 250 million years.

The decision was announced in March by the Atlantic States Marine Fisheries Commission’s Horseshoe Crab Management Board, which stated its intent is to “increase the abundance of horseshoe crab eggs to meet the energetic requirements of migratory shorebirds that stopover in the Delaware Bay.”

The board voted 12-to-3 to restrict the harvest of horseshoe crabs and prohibit commercial harvest and landings from May 1 through June 7—the prime spawning season.

These new restrictions will go into effect in New Jersey, Delaware and Maryland. New Jersey and Delaware have each set a commercial harvest limit of 150,000 crabs—Maryland’s limit is 170,000. New York has also agreed to limit its catch to 150,000 crabs. The board agreed to encourage bait-saving techniques; horseshoe crabs are primarily harvested as bait for the conch fishery.

It’s the latest in a series of actions over the last decade to curb horseshoe crab catches along the coast and in the Chesapeake to protect both the crabs and the birds that eat them.

It reflects the increasing complexity of fisheries management as agencies seek to protect not only individual species, but also those that depend on them—in this case birds. The ASMFC acted based on a recommendation from the U.S. Fish and Wildlife Service that horseshoe crab harvests be reduced around Delaware Bay. Each spring during the high tides of new and full moons the crabs descend on the bay to spawn, coinciding with the migration of shorebirds.

Conservationists welcomed the decision, which comes amid renewed warnings that the horseshoe crab population may be declining along with several species of migratory shorebirds that depend on the crabs for food.

New Jersey officials say the migrating shorebird species most in peril if horseshoe crabs decline is the red knot. Scientists predict the bird could be extinct within six years.

The migratory shorebirds travel more than 18,000 miles each year, often as many as 2,500 miles nonstop from their winter home in Brazil to their summer home in the Arctic. The Delaware Bay is their last stop en route to the Arctic. They eat enough horseshoe crab eggs in the bay to double their weight so that they can survive their long migration.