CHESTERTOWN — A workshop last month on cownose rays provided experts with new information about the species that is commonly thought to be invasive to the Chesapeake Bay.
The workshop — “Cownose Rays in the Chesapeake Bay: What Do We Know?” — was held Oct. 22, at the National Aquarium in Baltimore.
Its agenda included scientists, experts and representatives from different institutions in the country, talking on subjects like the rays’ diet, migration patterns and whether the species actually is a detriment to the Bay.
Matthew Ogburn, a marine ecologist at the Smithsonian Environmental Research Center in Edgewater, spoke at the workshop. Ogburn’s work currently involves surgically implanting acoustic tags into rays and tracking their movements throughout the Bay.
“It was really productive and interesting. There was a lot of new research that’s been gathered over the past decade on how we can move forward with the rays in the Bay,” Ogburn said in a telephone interview Tuesday, Oct. 27.
He said one topic discussed was the cownose rays’ dietary habits.
In a June interview, Robert Fisher, fishery specialist at the Virginia Institute of Marine Science, said the rays are usually blamed by watermen and industrial fisheries for reducing the crab and oyster population in the Bay.
Fisher also was a speaker at the Oct. 22 workshop.
“The main findings presented were that oysters are not the main part of the cownose ray’s diet,” Ogburn said Oct. 27 “Though they have been known to eat them, their main food sources are clams and small crustaceans.”
However, Ogburn said cownose rays will eat oysters in aquacultures if they come across them. He said fishermen and fishery workers can use preventive measures, like placing netting over the oysters, to deter the rays.
He said the workshop revealed that although there is no solid figure on the ray population, it has one of the slowest birth rates among marine species. A female ray typically will give birth to one offspring per year.
“There have been harvesting efforts on the cownose ray, but the population does not support a large haul,” Ogburn said. “If we catch too many, the population could take a long time coming back.”
He said the rays’ migration pattern shows that they spend the spring and part of the summer season in the Bay, to mate and feed. While the females stay in the Bay to give birth, the males can travel as far as Cape Cod, Mass., before the schools move to the waters near Cape Canaveral, Fla.
“We’re just starting to gather information, but we’re learning more and more that the cownose ray lives on the East Coast,” Ogburn said. “We also don’t know if it’s the same school that keeps coming back, or if it’s a different group each time.”
However, he said the cownose ray is in no way invasive, and that records show they’ve been in the Bay for millennia.
“They’ve been here and belong here,” Ogburn said.
He said though the cownose ray can have a negative effect on the Bay, that impact is no greater than any other predator. He also said the workshop showed a study done in the San Francisco Bay, where the rays were helpful in keeping the oyster population in aquacultures stable by feeding on the crabs.
“What was presented at the workshop seemed to support that the rays are not destroying the Bay, but are influencing the ecosystem and quite possibly making positive changes,” Ogburn said.
In a follow-up interview Wednesday, Oct. 28, Ogburn said that the results of the workshop would be complied into a report by the National Oceanic and Atmospheric Administration’s Chesapeake Bay office and released to the public by the end of the year.
“The purpose of the workshop wasn’t to make any managerial decisions, but to bring scientists together and share new information with everyone who attended,” Ogburn said.
He said the report should appear on the Chesapeake Bay Program’s website and will summarize new findings, as well as give fishery managers a direction to take when it comes to decisions about cownose rays.