WASHINGTON -- Overfishing of powerful sharks, a top predator in the ocean, might endanger bay scallops, a gourmet delicacy.
With fewer sharks to devour them, skates and rays have increased sharply along the East Coast, and they are gobbling up shellfish, particularly bay scallops, researchers report in today's issue of the journal Science.
Ecologists have known that reducing key species on land can affect an entire ecosystem, but this study provides hard data for the same thing in the ocean, said lead author Charles H. Peterson of the Institute of Marine Sciences at the University of North Carolina.
Coauthor Ransom A. Myers of Dalhousie University in Halifax, Nova Scotia, and Peterson were studying different ends of the food chain, Peterson said in a telephone interview.
"Myers was working on great sharks, and I was working on cownose rays and their impact on bay scallops and other shellfish. We realized that separately we had interesting science, but together we had an absolute revelation," he said.
Now, scallop numbers are very reduced, he said. "The rays, as they come through, eat all that are in any dense patch and have eaten so many there does not appear to be enough to create spawning stock."
Scallops are an easy target because they do not burrow into the sand, Peterson said. Millions of rays from Chesapeake Bay migrate through the area, he said. "What are they going to feed on to fuel their migration?"
In some areas they enter sea grass beds and dig up clams, but that is an important nursery habitat for shrimp, blue crabs, and fish, Peterson said, "so there is a high concern that we may now be cascading to habitat destruction."
Steve Murawski, director of scientific programs at the National Marine Fisheries Service, was not so sure. He said the links between the large sharks, medium-size rays, and bay scallops were "tenuous."
"Scientists will now debate the specific numbers and correlations in this paper, and sadly, Dr. Myers will not be around for that debate," said Robert E. Hueter, director of shark research at Mote Marine Laboratory in Sarasota, Fla. Myers, 54, died Tuesday in Halifax.
For more information, visit the journal Science's website, www.sciencemag.org.