By Julia Robins, Virginia Sea Grant Correspondent
The cownose ray has been in the industry cross hairs ever since they’ve been seen gobbling up shellfish crops. As industry considers the range of options for keeping rays off shellfish farms, including developing a commercial fishery, new research about cownose ray biology may help in making those decisions.
“I hope this work provides a better understanding of the cownose ray life history by all involved,” says Bob Fisher about his latest peer-reviewed publication.
Fisher, Virginia Institute of Marine Science Fisheries Specialist and extension staff affiliated with Virginia Sea Grant, studied cownose rays’ age, growth, and reproductive biology—necessary factors to assess before developing a cownose ray fishery.
For more than 30 years, cownose ray in the Chesapeake Bay have received little attention from research and the fishing industry. Recently, with the rise of Virginia’s coastal shellfish industry, that has begun to change. The ray’s greedy appetite for bottom-dwelling prey meant that many growers were losing thousands of their shellfish crop when schools of rays passed by. This caused many in the industry to call for the development of a cownose ray fishery, and the growing interest was one of the factors that led Fisher to conduct new research on the ray.
One of his key findings: Cownose rays don’t reproduce as quickly as other fish, and so developing a cownose ray fishery would be tricky. The rays can live into their late early 20s, but females don’t start having offspring until around seven years old. Even then, they typically only have one per year. Compared to other fish that can lay thousands of eggs at one year old, cownose rays are especially slow to replenish their population.
“The fishing industry has a much better understanding of the rays biological constraints and has embraced the idea for responsible management of this species.” says Fisher, adding that industry has other options for managing rays. Protective reefs, for example, can protect smaller oysters from predation, and the spat-on-shell method can also reduce predation. This method causes oysters to grow together in a cluster, making it harder for the cownose ray to grasp any single oyster in the cluster.
Fisher’s research, “Age, Growth, and Reproductive Biology of Cownose Rays in Chesapeake Bay,” was funded by the National Oceanic and Atmospheric Administration and can be found in the journal, “Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science.”