By Kevin Majoros
Situated on the bank of the Rhode River near the mouth of the Chesapeake Bay is the sprawling 2650-acre campus of the Smithsonian Environmental Research Center.
The Smithsonian Environmental Research Center (SERC) provides science-based knowledge to meet environmental challenges of the 21st century. SERC leads research on coastal ecosystems to inform real-world decisions for wise policies, best business practices and a sustainable planet.
Among SERC’s many programs and projects is the Movement of Life Initiative which develops the science, technology, analytical tools, and models to conserve and manage movement as a critical process for maintaining biodiversity and healthy ecosystems.
Their focus in this initiative is on coastal fish and invertebrates and their connection with freshwater and the open water.
The Misunderstood Cownose Ray
Every summer, large numbers of cownose rays enter the Chesapeake Bay area and its estuaries using the brackish waters as a nursery ground.
They are native to the Chesapeake Bay area and their main diet consists of soft-shell clams and razor clams. As clam populations declined in the area due to overharvesting and disease, cownose rays began snacking on oyster beds.
They were labeled as villains by the oyster industry and growers went as far as launching a campaign against them – “Eat a Ray, Save the Bay”.
One thing that was lacking in all of the debates was scientific research on the species. The idea of overharvesting cownose rays through unregulated fisheries would leave their population susceptible to declining populations without knowing what role they play in the coastal food web.
Through their Movement of Life Initiative, SERC began tracking cownose rays in 2014 with the hope of gathering movement ecology data to increase knowledge on how harvesting can impact the species.
“The crux of the decision to begin the research was to generate data to help inform management decisions, which paid off a few years later when Maryland Department of Natural Resources began developing a fishery management plan for rays,” says Matt Ogburn, principal investigator, and senior scientist at SERC. “Knowing their movement and scale of impact will provide managers of fisheries knowledge on managing the species without having a major effect on the population.”
Keira Heggie and Kim Richie are tagging the coenose ray. ©Smithsonian Environmental Research Center 
Marine Ecology Ray Tagging ©Smithsonian Environmental Research Center
Tracking Cownose Rays Using Acoustic Telemetry
Cownose rays (Rhinoptera bonasus) can live up to 30 years and are slow to mature – six to seven years. They can grow to be as large as one meter across and can weigh up to 22 kilograms.
They have plate-like teeth that are used to crush the hard shells of bivalves and females only give birth to one pup a year each summer with a maximum of 15 pups throughout the ray’s lifetime.
SERC began tagging adults in 2014 with a quick look sample of 25 rays. They have continued in two year cycles and are currently analyzing data from 125 rays.
After giving birth in the waters near the Chesapeake Bay, a female ray will mate again while still in the same waters.
“We already knew that cownose rays were using the Chesapeake Bay as nursery grounds in the summer, but we didn’t know where they went when they left in the fall,” Ogburn says. “Even though they are widely distributed in the summer from Long Island down to Virginia, they surprisingly all go to the same place in the winter off the coast of Cape Canaveral.”
One other discovery is that some of the rays are actually returning to the same spot in the same river when they migrate back north. Understanding these migration patterns links spatially separated ecosystems and is critical in decisions regarding conservation and management.
Gaining Insight on Migratory Species
Among the other species being researched in the Movement of Life Initiative are bull sharks, horseshoe crabs, juvenile striped bass, and Atlantic sturgeon.
The use of tracking techniques on migratory species sheds light on what resources they are using in their travels and what they are doing to alter populations.
“There is still a lot of research needed on the impact of the cownose ray,” says Ogburn. “There is a study suggesting that their digging in sediment increases bivalve diversity.”
The data SERC is collecting on movement ecology is especially important for cownose rays because their slow reproductive rate would not be able to sustain overfishing. Finding that balance between conservation and harvest is a key to biodiverse marine ecosystems.
“We think that rays play an important role in the Chesapeake Bay even though we don’t know the extent. It doesn’t make sense to alter their presence without knowing their impact,” Ogburn says. “It is amazing to think of their annual migration and that these species are incredibly cosmopolitan.”
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This piece was prepared online by Panuruji Kenta, Publisher, SEVENSEAS Media