June 19, 2008

Will there be a cownose ray on your dinner plate anytime soon?


Charles Peterson links the collapse of North Carolina’s bay scallop fishery to an increase in the cownose ray population.

To test the theory that cownose rays can devour scallop populations, Peterson, a researcher at the University of North Carolina Institute of Marine Science, built fences around some scallop beds close to the rays’ late-summer migratory routes in the state’s estuaries.  

He found that scallops outside the fences nearly disappeared, while those inside survived at a sustainable level.      

Now Peterson is looking at the impact of rays’ feeding behavior on oyster restoration efforts in the state.

“We’re not ready to call in the troops yet, but the cownose can be a real pest,” Peterson said.

Cownose rays possess all the right equipment to hunt down prey like scallops, oysters, clams, and blue crabs.  

With wingspans that can reach up to 7 feet, rays glide over the sea floor, stirring up sand and exposing shellfish.  Sensors under their distinctive snouts alert them to the presence of prey.

And, they have powerful dental plates for crushing shells.   

“And when they can’t find scallops easily, they go in like bulldozers and tear up seagrass beds and habitat,” Peterson said.  

He said surveys show that the number of cownose rays is surging all along the eastern seaboard.  A report he co-authored last year said the population could stand at over 40 million.  

That report linked the booming ray population to the decline in the number of large sharks, like sandbars and hammerheads, since the 1970s.

But not all scientists agree that cownose rays have surged in abundance, citing the lack of targeted population surveys, or that sharks eat a considerable number of rays.  

“The cownose ray situation is far from clear,” Virginia Institute of Marine Science shark researcher John Musick told a reporter for the Bay Journal last year.

Still, the state of Virginia would like to develop a commercial market for cownose ray, and some restaurants there now offer what they call “Chesapeake Ray.”

Trish Murphey, biologist with the North Carolina Division of Marine Fisheries (DMF), tasted cownose ray at a Virginia Sea Grant conference.

Murphey said the texture was “pleasant, not chewy,” and the flavor was very mild.

“All of the samples I tried were either marinated or served with a sauce, probably because the taste was so mild,” she said.

NC DMF director Louis Daniel said a commercial cownose market could give watermen a new income source and could benefit shellfish populations.

But he cautioned a fishery for the under-utilized species should be limited.

“We’d need to start slowly and get a handle on the population size and then decide how far down we would want to fish it,” he said.

Daniel said the fishery would have to be carefully managed due to the biological characteristics of rays. They are slow-growing, live-bearers that usually birth just one pup per litter.

“And, right now we don’t have enough information to really know the complete role of cownose rays in the ecosystem,” he said.

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