1 post in this topic

cownoseray-1.jpg

Description: The Cownose ray is a cartilaginous fish and the most common ray found in the Chesapeake Bay. The Cownose ray is light to dark brown in color and sometimes with a hint of yellow. The ventral surface is white or creamy white with brownish pectoral outer corners or tips. Its eyes peek out from the sides of its broad head giving it a cow-like appearance. Some rays have marks that appear as obscure dark lines or bands that begin at the center of the disc and radiate outward. The Cownose ray has a set of remarkable teeth plates that are made for crushing clams and oyster shells. The Cownose ray has nine series of teeth in each jaw.

The disc is 1.7 times as broad as it is long. The main portions of the pectorals arise from the sides of the head, close behind and below the eyes. The outer corners of the pectorals are pointed and become concave toward their posterior margins. The dorsal fin originates approximately opposite the rear ends of the bases of the pelvic fins and is rounded above.

The tail, round to oval in cross-section, is moderately stout near the anterior spine, and tapers toward the rear to a lash-like tip. The length of the tail is about twice as long as the body and is measured from the center of the cloaca to the front of the head, but small specimens can be three times as long.

There are one or two tail spines (commonly known as stingers). The first spine (posterior spine) is located directly behind the base of the dorsal fin. If present, the second spine (anterior spine) has a free portion that is about half as long as the anterior margin of the pelvic fin. The anterior spine varies in length from very short (tip hardly emerges from skin) to as long as the posterior spine. The spines contain marginal teeth with broad bases and sharp tips that curve rearward at a 45º angle. The number of teeth ranges from 22 to 45. The sharp spine processes toxins and mucous into its ventral grooves, which is produced from spongy venom glands located along the underside of the spine. It doesn't inflict serious damage, but can produce a nasty infection if not properly cleaned and cared for. The stinger is located close to the ray's body. The skin of the Cownose ray is smooth at all ages.

Similar Fish: Bat rays, manta rays, stingrays, spotted eagle rays; Family: Myliobatidae

Where Found: The Cownose ray is found along continental shelves in warm water and the tropical waters of the western Atlantic from southern New England to southern Brazil. This includes the coastal waters of the Gulf of Mexico and parts of the Caribbean. These rays have been known to be especially abundant in the Chesapeake Bay during the summer. The Cownose rays make mass school migrations determined by water temperature (below 22 degrees C). Cownose rays can be found at depths of 72 feet.

Size: When mature the male disc width is 75 to 85 cm. The female disc width is 65-90 cm

World Record: The maximum size that this species ordinarily grows is debated but an unsexed/male disc width of 84 inches has been recorded.

Tactics to catch: Commercial netting. Recreational anglers aren't interested in this potentially dangerous fish because of the painful results of being struck by the barbed stinger.. It was reported that sailors have been known to dig a grave for the man who writhed in pain, as they were sure it was a death sentence.

Climate (water temperature range): Between 15 and 29 C.

Spawning habits: The mature females normally give birth to only one pup that is approximately 14 inches. The gestation time is 11 to 12 months if only one pup is born and 5-6 months if there are actually two lives births a year. It is not sure if the cownose ray gives birth once or twice in the span of a year.

The breeding period is considered to be June through October. A large school of cownose rays of varying ages and sexes was spotted in the shallows of Delaware Bay by biologists from the NMFS Apex Predators Program in July of 2000. A female cownose ray was seen swimming with the edges of her pectoral fins sticking out of the water. There were as many as 6 male cownose rays were trying to grasp the pectoral fins to mate. Occasionally, there would be major splashing as the males tried jumping out of the water to grasp the pectoral fins with their mouths. It is thought that the female's having the pectoral fins out of the water might be mate avoidance behavior (not that you can blame them as often there are sharp teeth marks left on the pectoral fins).

Development is ovoviviparous (producing eggs that develop within the maternal body and hatch within). The embryos lose the shell capsule in early August. It has been observed that by the third quarter term, the embryos are upright in the uterus with the rostrum facing forward, pectoral fins folded dorsally, and the tail with the heavily sheathed spine is bent forward along the dorsal side of the disc. Initially, nutrition is provided to the embryos is from the yolk, which gradually shrinks between August and October. After October, histotroph (a viscid yellowish secretion from the uterus), provides the remaining nutrition. It is assumed that the embryos receive this through their mouth, spiracles, and gill slits.

Table food? The cownose ray is a tasty, low-fat, alternative to red meat and has no fishy taste at all. Its cartilages may also have medicinal properties. Try marinating wing-cut fillets in olive oil, wine vinegar, oregano and lime juice, then grilling them or maybe you will want to try barbecued ray wings.

Consumption Concerns: Shigella may be acquired from eating cownose ray meat that has been contaminated with this bacteria. This bacteria causes shigellosis that results in dysentery, which include the symptoms of diarrhea, pain, fever, and possible dehydration.

Feeding habits: The cownose ray has been known to use a very specific mechanism to obtain deep-burrowing prey. They locate food on the bottom substrate (benthos) through mechano- or electroreceptive detection. Once they suspect prey is there, they employ a combination of stirring motions of the pectorals while sucking/venting both water and sediment out through the gills and away from the area to create a central steep-sided cavity depression. The continued movement of the pectoral fins aids in dispersing the sediments released from the gills and increases the depth of the depression. Eventually, the food is seized and drawn into the mouth. Common prey items include nekton, zoobenthos, finfish, benthos crustaceans, mollusks, bony fish, crabs, lobsters, bivalves, and gastropods.

Remarks: The Cownose rays are known for their long migrations in large schools. They are strong swimmers, able to cover long distances. In the Atlantic Ocean, their migration is northward in the late spring and southward in the late fall. The population in the Gulf of Mexico migrates in schools of as many as 10,000 rays, clockwise from western Florida to the Yucatan in Mexico. Even in large groups the Cownose ray is shy and not threatening. This ray is often mistaken for a shark because when it “flies” near the surface its wingtips break the surface and resemble a shark’s dorsal fin.

References:

Florida Museum of Natural History: Kimberly Kittle

finbase.org

JSTOR by Estuarine Research Federation

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now