The Atlantic cownose ray (Rhinoptera bonasus) is a species of stingray that is found in the Gulf of Mexico, as well as along the eastern coasts of North and South America. Cownose rays have a vulnerable life history and a very slow population growth rate due to the fact that they have a long gestation period (around twelve months!) and produce only one pup per year. Historically, cownose rays were implicated in the decline of commercial scallop and oyster fisheries on the East coast, though little evidence supports this. The result was a large, unregulated culling effort in which mature animals (including pregnant females) were targeted through derbies and other fishing efforts during their reproductive months. Since an official stock assessment has never been conducted for the species, the effects of this fishery on the cownose ray population were immeasurable.
Movement studies have been conducted for cownose rays along the East coast using acoustic tracking, showing that cownose rays undergo long seasonal migrations between Chesapeake Bay and south Florida. However, very little is known about their movement behavior in the Gulf of Mexico. Our lab has been conducting shark surveys in Apalachicola Bay, Florida for several years, in which we have captured both adult and newborn cownose rays in the summer months. With a recent collapse of the oyster fishery and a 5-year closure on wild oyster harvest in the bay, a cownose ray movement study is both timely and immediately informative.
For this project, adult cownose rays and pups will be tracked using acoustic telemetry in Apalachicola Bay, Florida to 1) learn more about their general movement ecology in the Gulf of Mexico, 2) describe seasonal patterns of habitat use within the bay for different life stages, and 3) compare cownose ray habitat use and previous cownose ray bit force studies to quantify the true interaction potential between rays with oysters they are actually capable of eating.
Why this Matters
As a species with one of the slowest population growth rates of any fish, it is crucial that we learn enough information about the ecology of the animals in case there is a need for a formal stock assessment to be completed. An important piece of the knowledge gap about cownose rays includes their movement and habitat use behavior in the Gulf of Mexico. As claimed implications in commercial bivalve fisheries led to large culling efforts on the East coast, it is critical that we define their true interaction potential with oysters in Apalachicola Bay in case the same solution is suggested for this system. Part of this study involves conducting genetic analysis of all sampled rays, to confirm they are actually Atlantic cownose rays (Rhinoptera bonasus), rather than the morphologically identical Brazilian cownose ray (Rhinoptera brasiliensis) that was recently confirmed to have an overlapping geographic range. Defining whether these two species are overlapping in the area may also lead to important implications for the management and conservation of cownose ray species.
- Florida State University Coastal and Marine Laboratory
- Florida State University, Department of Biological Science
- Gavin Naylor, Florida Museum of Natural History
- Save Our Seas Foundation
- Guy Harvey Ocean Foundation
- Women Divers Hall of Fame
- American Elasmobranch Society
- FSU Coastal and Marine Laboratory Board of Trustees
- FACT Project Codes:
- ABCOWN (tags)
- APBAY (array)
- FACT Project Codes: