Chesapeake Bay Program - Cownose Ray

<body> <p>Often, when the cry "shark!" is heard on the Chesapeake Bay, the instigator of the panic is the cownose ray (<i>Rhinoptera bonasus</i>). As the ray swims (flies) through the water, its wing tips breaking the surface, the resemblance to the dorsal fins of the shark is remarkable. The excited observer may be a bit shamefaced when the "shark" is discovered to be the passive cownose ray.</p> <p>Not that the cownose ray is an animal that should be taken lightly. In 1608, John Smith learned about the ray's might in a near fatal encounter. As Smith stood spearing fish with his sword in the shallows of the Bay off the mouth of the Rappahannock, he stabbed a ray which pierced him in the wrist with its toxin-laden spine. Although there was no blood or apparent wound, his arm and shoulder swelled and he was in terrible pain. Convinced that he was about to die, his crew prepared a grave.  Whether his body overcame the trauma or the salve applied by the ship's doctor remedied his condition, John Smith felt well enough to eat the same ray for supper that night. The story has been incorporated into Bay lore - the spot where Smith was stung is still known as Stingray Point.</p> <p>Described as a flattened shark, all rays belong to a group of animals which lack true bone; their skeletons are composed of cartilage. These fishlike creatures are called elasmobranchs and include the rays, sharks and skates. All are characterized by the lack of a swim bladder which helps true fish float. Since the bodies of most elasmobranchs are more dense than sea water, and since they lack a swim-bladder they have a tendency to sink. This condition limits some species to life at the bottom while others evolved mechanisms to counteract the gravity-induced disability.</p> <p>Another characteristic of many elasmobranchs, including the rays, is most unusual for fishlike creatures, they are able to give birth to live young. The ray pup grows inside its mother positioned with wings folded over its body, gaining nutrition from the mother's uterine secretions. It emerges in what humans would consider a breech birth-tail first. In this position, there is no damage to the female.</p> <p>At birth, the cownose ray is about 11 to 18 inches in width. When mature, it attains a 45 inch width, may weigh 50 pounds or more, and is brown-backed with a whitish belly. This species does not have particularly distinctive coloration but its shape is readily recognizable. Aside from the broad wings and long tail characteristic of rays, the cownose has a notch in its head which creates a double-headed appearance; from the top it looks somewhat like a cow muzzle. Eyes peer out eerily from the side of the broad head. Hidden within this strange head is a set of equally remarkable teeth plates designed for crushing clam and oyster shells.</p> <p>Being stung by a cownose ray, though potentially fatal, is uncommon. Unlike some other ray species, the cownose rarely rests on the bottom where a swimmer might step on its stinger. This stinger (spine) is situated on the tail close to the ray's body, so merely flicking the tail does not usually inflict damage. With pointed, recurved teeth lining its lateral edges, the spine processes toxins and mucous in its ventral grooves. Spongy venom glands which produce the toxin are situated along the underside of the spine. In the rare instance that a person is stung by a ray of any sort, the wound should be cleaned and immersed in extremely hot water which seems to deactivate the toxin.</p> <p>The cownose ray is a migratory animal, arriving in the Bay in May and staying until late September or October. It ranges from Massachusetts to the middle part of Brazil. Migrations to the north in the summer and south in the winter are routine, often with large groups of the animals veering into the Chesapeake for the summer. Once in the Bay, the rays move northward in schools of five to more than 200 individuals searching for good feeding grounds. They arrive in the Eastern Shore portions of the Upper Bay by early June. Cownose ray pups are born in mid June; refertilization of the mother usually takes place within 10 days of birth.</p> <p>The cownose ray is a voracious feeder, preferring to feast on the soft clam, <i>Mya arenaria</i>. Rays will also prey on oysters, hard clams and other invertebrates. During feeding, these animals move as a group regardless of time. The rays seem to be cavorting but actually are using rapid wing movements to churn the bottom sediment to uncover hidden clams and oysters. Once they have located a victim, they clasp it in their powerful jaws and crush the shell in search of the meat inside.</p> <p>In the mid-1970s, some scientists expressed concern that the cownose ray was responsible for extensive damage to the eelgrass beds of the Bay. Others disputed this finding, contending that the decline of seagrass beds throughout the Bay resulted from the cumulative effect of pollutants, disease, and sediments entering the system. </p> <p>Another concern is the apparent increase of cownose rays in the Bay. Substantive evidence for this increase is lacking, because rays are not included in the surveys of any fish management program - a larger number of cownose rays would result in greater shellfish consumption. In an era when pollution, disease and overharvesting have decimated much of the shellfish population, increased predation by rays may pose an additional problem. <ul> <li>Read more about this topic in the <a href="http://www.bayjournal.com/98-11/COWNOSE.HTM" target="_top">Bay Journal</a>.</li> </ul> <p>One method of controlling the ray population is to promote both commercial and recreational cownose ray fisheries, however this may not be feasible. Not the most exciting of game fish, a large cownose does put up a lengthy fight and, once landed, provides about five pounds of meat. Until the government discovered the fraud, ray wings were often punched into small plugs to mimic scallops. Under this guise, the public willingly consumed the ray. Perhaps, as consumers become more experimental with the foods they eat, introduction of cownose ray meat as a commercial product under its own distinctive name may prove economically and environmentally advantageous. </p> <div align="center"> <center> <table border="1" cellpadding="0" cellspacing="0" width="100%"> <tr> <td bgcolor="#C6C68C"><strong>Other Sites of Interest:</strong> <ul> <li><a href="http://www.aqua.org/animals/species/prrays.html" target="_top">More about rays</a> - National Aquarium in Baltimore</li> </ul> </td> </tr> </table> </center> </div> <hr noshade> <p align="center"><font face="Times New Roman" size="2">To bookmark this page, please use this URL: <a href="cownose_ray.htm" target="_top">http://www.chesapeakebay.net/cownose_ray.htm</a> </font></p> <p align="center"><font size="2">For more information, contact the Chesapeake Bay Program Office, 410 Severn Avenue, Suite 109, Annapolis, MD 21403 /  Tel: (800) YOUR-BAY /   Fax: (410) 267-5777. </font></p> <p align="center"><font size="2"><a href="javascript:print()"><img src="images/print.gif" width="34" height="38" border="0" alt="Print Current Page" align="right"></a><a href="http://www.chesapeakebay.net/directions.htm" target="_top">Directions to the Bay Program Office</a><a href="http://www.chesapeakebay.net/cims" target="_top"><img src="images/cims1.gif" height="19" width="51" border="0" align="left"></a></font></p> <p align="center"><font size="2">Last modified: 09/18/00</font> </body>