Cownose Ray
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| Cownose Ray Conservation status: Secure | ||||||||||||||
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| Rhinoptera bonasus Mitchill, 1815 |
The Cownose Ray (Rhinoptera bonasus) is the most common type of ray found in the Chesapeake Bay. The rays grow rapidly and male rays are about 35 inches (900 mm) in width and weigh 26 pounds (12 kg). Females are 28 inches (700 mm) in width and weigh 36 pounds (16 kg). Rays belong to a group of animals which lack a true bone.
Rays are fishlike creatures that are called elasmobranchs. When the ray is small it grows inside its mother, positioned with wings folded over its body. It also gains nutrition from the mother's uterine secretions. It also breaks through what we call a breech birth-tail first. The Cownose ray is 11 to 18 inches (280 to 460 mm) in width at birth. When it gets older it can grow to 45 inches (1.1 m) in width, and weigh 50 pounds (23 kg) or more. It is brown-backed with a whitish belly.
Cownose Rays don't have a particularly distinctive coloration but its shape is recognizable. Its eyes peer out spookily from the sides of the broad head. It also has a set of remarkable teeth plates designed for crushing clams and oyster shells.
One can also be stung by a Cownose Ray. The stinger is on its tail really close to the ray's body, and it doesn't usually inflict damage. The stinger is known as the spine which is pointed and it has teeth lining its lateral edges.
The Cownose Ray feeds upon clams. It is a voracious eater. They also eat oysters, hard clams and other invertebrates. Rays move as a group regardless of time during feeding. When they locate their prey they place it in their jaws and crush it.
Another concern is the apparent increase of Cownose Rays in the bay. Evidence for this increase is lacking because rays are not included in the surveys of any fish management program. A large number of Cownose Rays would result in greater shellfish consumption. Also in an era when pollution, disease and overharvesting have decimated much of the shellfish population, increased predation by rays may pose an additional problem.