Overfishing of Sharks May Lead to Scallop Losses

Overfishing of sharks may be causing the depletion of scallop populations.

A new study has found that aggressive fishing of large sharks in the Northwest Atlantic may be causing the decimation of the bay scallop fishery along the U.S. Eastern seaboard. Hammerheads, duskies, and other sharks have been over-harvested for their meat and fins, allowing their prey, in particular the cownose ray, to thrive and deplete the scallop population, the research suggests. The study combined the population trends of sharks, skates, and rays over the last 35 years with experiments on the effects cownose rays can have on scallops.

“This is an example of how overfishing is self-defeating,” notes Worldwatch Institute senior researcher Brian Halweil, author of Catch of the Day: Choosing Seafood for Healthier Oceans. “Not only does it eliminate the renewable resource of the fish population, but it also ripples through the marine food chain and eliminates other sources of seafood.”

Cownose rays ravish scallop beds during their annual southward migration, Pete Peterson, a marine biologist at the University of North Carolina and one of the study’s authors, explained in a New York Times interview. They do so before the scallops reproduce, creating an unsustainable cycle. Dr. Peterson also noted that the cownose ray is just one of a dozen midlevel species whose populations are rising as shark populations decline. “There’s another 11 out there doing who knows what,” he said.

According to Steve Murawski, director of scientific programs and chief science adviser at the National Marine Fisheries Service, the study shows correlation between declining shark and scallop populations, but not causation. Habitat loss and pollution are possible alternate causes of the effects discussed in the study, according to Dr. Murawski.

This story was produced by Eye on Earth, a joint project of the Worldwatch Institute and the blue moon fund. View the complete archive of Eye on Earth stories, or contact Staff Writer Alana Herro at aherro [AT] worldwatch [DOT] org with your questions, comments, and story ideas.