Cownose rays tend to get a bad reputation because of what they are eating—or what people think they are eating

Learn about cownose rays, a species that migrates naturally to the Chesapeake Bay every summer to mate and raise their young.

Cownose rays are highly specialized to eat bivalves like softshell clams, macoma clams and razor clams. But if other prey are unavailable, they occasionally snack on oysters and hard clams, a fact that has concerned watermen and the shellfish industry.

According to a report released by the Chesapeake Bay Program’s Sustainable Fisheries Goal Implementation Team, while oysters and hard clams are not a significant part of a ray’s diet, if they do choose to chow down on these bivalves, intense feeding in one localized area can occur. This feeds the fear that cownose rays will impact oyster restoration and aquaculture operations. However, because of the rays’ jaw size and the force it takes to crush large bivalves, feeding on oyster clusters found in sanctuaries or aquaculture operations can be very difficult for them. The most recent study on the diet of cownose rays shows small, soft shell clams and crustaceans make up most of what they eat.

Another popular misconception of the cownose ray is that it is an invasive species. In fact, they are native to the eastern seaboard of the United States and have been observed in the Chesapeake Bay for centuries.

  • Produced by Will Parson
  • Additional footage by Smithsonian Environmental Research Center and Virginia Institute of Marine Science
  • Music/Audio: "Cloud Line" by Blue Dot Sessions via FreeMusicArchive.org
  • Special thanks to Robert Aguilar, Smithsonian Environmental Research Center and Virginia Institute of Marine Science

Comments (2)

Chesapeake Bay Program
December 05, 2019

Cownose rays play an important role in the coastal food web – they eat shellfish like soft-shell and razor clams, but also oysters and hard clams. Their predators include cobia, bull sharks and sandbar sharks. Despite being mistaken for an invasive species, cownose rays actually reproduce quite slowly, meaning their population grows fairly slowly. Check out our field guide entry on the cownose ray for more information - https://www.chesapeakebay.net/discover/field-guide/entry/cownose_ray

Ava Smith
November 24, 2019

What is the cownose rays niche in the Chesapeake bay ecosystem?

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