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Cownose ray

life science Maturity 5-7 Next article →

The cownose ray, known scientifically as Rhinoptera bonasus, is a distinctive species of fish. It belongs to the order Myliobatiformes, which includes manta rays and eagle rays. These rays are found throughout the western Atlantic and Caribbean. Their range extends from New England down to southern Brazil. They prefer shallow coastal waters and estuarine ecosystems. These environments allow them to tolerate a wide range of salinities.

Cownose Rays
Cownose Rays

The name of this ray comes from Ancient Greek. Rhinoptera combines the words for nose and wing. The specific name, bonasus, means bison in Ancient Greek. This likely refers to the unique shape of their snout. They have a broad head with wide-set eyes. Two distinctive lobes sit on their subrostral fin. This shape resembles the nose of a cow. Their coloring is usually brown on the back. The belly is often white or yellow.

Stachelrochen (352016303)
Stachelrochen (352016303)

Cownose rays are durophagous, which means they eat hard-shelled organisms. They target mollusks and crustaceans like clams and scallops. To eat, they use a process of suction. They open and close their jaws to pull prey in. Their jaws are extremely robust to handle shells. They use dental plates to crush their food. These plates consist of interlocking bars. The hardness of these teeth is comparable to concrete. Their cephalic lobes also help push food toward the mouth.

Rhinoptera bonasus, cownose stingray teeth & mouthparts
Rhinoptera bonasus, cownose stingray teeth & mouthparts

These rays follow a regular migratory pattern. They travel in large schools based on sex and size. They move north in the late spring. They move south in the late fall. Many rays visit the Chesapeake Bay during the summer. This area serves as a site for mating and nurseries. Females and their pups stay in the estuarine waters. Males sometimes leave the bay earlier than females. They may do this to reduce competition for food or shelter.

Reproduction in cownose rays is a slow process. They are an ovoviviparous species. This means embryos grow inside the mother until they hatch. The gestation period lasts between 11 and 12 months. At full term, the offspring are born live. They exit the mother tail first. Rays do not reach maturity until they are 70% of their maximum size. Females reach maturity between 7 and 8 years old. Males reach maturity between 6 and 7 years old.

Stachelrochen (352016303)
Stachelrochen (352016303)

Lifespan and size also differ between the sexes. Males typically reach a width of about 45 inches. Females are larger and reach about 50 inches in width. The oldest recorded female lived to be 21 years old. The oldest recorded male lived to be 18 years old. These specific rays were both observed in the Chesapeake Bay. Because they mature slowly, they are sensitive to changes in their environment.

Cownose Rays
Cownose Rays

Cownose rays face several modern threats. In 2019, the IUCN Red List listed them as vulnerable. This is due to extensive commercial and overfishing. Some people believe the rays destroy oyster beds. This idea has led to campaigns like "Save the Bay, Eat a Ray." However, little evidence supports the idea that they deplete bivalve populations. Some studies show they do not eat many oysters. Other studies suggest they only eat shells of a certain size.

Cownose Rays
Cownose Rays

Humans can interact with these rays in different ways. Beach-goers sometimes mistake them for sharks. This happens when their fins break the water surface. When threatened, a ray can use a barb on its tail. This spine is located near the body. It has teeth on its lateral edges. The spine is coated in a weak venom. The sting causes pain similar to a bee sting. While usually not fatal, a sting to the abdomen can be dangerous.

Stachelrochen (352016303)
Stachelrochen (352016303)
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File:Rhinoptera bonasus, cownose stingray teeth & mouthparts.jpg
Rhinoptera bonasus, cownose stingray...
File:Cownose Rays.jpg
Cownose Rays.jpg
File:Stachelrochen_(352016303).jpg
Stachelrochen_(352016303).jpg
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