Cownose ray

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For other species of cownose rays, see Rhinoptera.

Cownose ray
Rhinoptera bonasus Brest.jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Myliobatiformes
Family: Myliobatidae
Genus: Rhinoptera
Species: R. bonasus
Binomial name
Rhinoptera bonasus
(Mitchill, 1815)

The cownose ray (Rhinoptera bonasus) is a species of eagle ray found throughout a large part of the western Atlantic and Caribbean, from New England, United States to southern Brazil (East Atlantic populations are now generally considered a separate species, R. marginata). Cownose rays grow rapidly, and male rays often reach about 35 inches (89 cm) in width and weigh 26 pounds (12 kg). Females typically reach 28 inches (71 cm) in width and weigh 36 pounds (16 kg). The cownose ray is classified as a stingray due to the very close relation to both sharks and skates. Stingrays belong to the family myliobatidae, a family that is also home to: bat rays, manta rays, and eagle rays.[1]

Taxonomy[edit]

Rhinoptera bonasus, comes from the Greek derivation of the word parts.

"rhinos"- nose

"pteron"- wing

"bonasos"- bison

Gestation and reproductive behavior[edit]

Cownose rays breed from June through October. A large school of cownose rays gather of varying ages and sexes in shallow waters. A female will swim with the edges of her pectoral fins sticking out of the water, with male cownose rays following her trying to grasp the fins to mate.[2]

The embryo grows within its mother with its wings folded over its body. Initially it is nourished by an egg yolk, although the uterine secretions of the mother nourish it later in its development. The length of gestation is disputed, but it is believed to last between 11 and 12 months and is variable. At full term, the offspring are born live, exiting tail first.

Cownose rays swimming in shallows in the Gulf of Mexico

Lifespan[edit]

Sexual maturity for both males and females is reached around 4 to 5 years of age. In the Gulf of Mexico, females live up to 18 years, and males only live up to 16 years.[3]

Size and appearance[edit]

The cownose ray is 11 to 18 inches (28 to 46 cm) in width at birth. A mature specimen can grow to 45 inches (1.1 m) in width, and weigh 50 pounds (23 kg) or more. There is some controversy over the size that a mature cownose ray can reach. A ray reaching a span of 84 inches (2.1 m) has been recorded.[4] The cownose ray is often mistaken for being a shark by beach-goers. This is due to the tips of the rays fins sticking out of the water, often resembling the dorsal fin of a shark.[1]

A cownose ray is typically brown-backed with a whitish or yellowish belly. Although its coloration is not particularly distinctive, its shape is easily recognizable. It has a broad head with wide-set eyes, and a pair of distinctive lobes on its subrostral fin. It also has a set of dental plates designed for crushing clams and oyster shells. When threatened the cownose ray can use the barb at the base of its tail to defend itself from the threat.[2]

A cownose ray has a spine with a toxin, close to the ray's body. This spine has teeth lining its lateral edges, and is coated with a weak venom that causes symptoms similar to that of a bee sting.[4]

Feeding habits[edit]

The cownose ray feeds upon clams, oysters, hard clams and other invertebrates. It uses two modified fins on its front side to produce suction, which allows it to draw food into its mouth, where it crushes its food with its dental plates. Cownose rays typically swim in groups, which allows them to use their synchronized wing flaps to stir up sediment and expose buried clams and oysters.[citation needed]

The cownose ray prefers to feed either in the early morning hours, or in the late afternoon hours; when the waves are calm and visibility is higher than during the day. The cownose ray has a jaw that reflects its diet of: benthic bivalve mollusks, crustaceans, and polychaetes. Their jaws are extremely robust and have teeth that are comparable to that of cement, allowing them to eat hard shells. (3) The feeding habits of cownose rays is cause for increasing concern, as they are known for destroying oyster beds that are already being destroyed largely by human pollution. The cownose rays destruction of large oyster beds only further puts oyster beds at risk.[5]

Migration[edit]

Cownose stingray teeth and mouthparts. Stingray teeth consist of interlocking bars (dental plates) that crush food.

The cownose ray often migrates from the Gulf of Mexico to Trinidad, Venezuela, and Brazil.[4] The Atlantic migration pattern consists of the cownose rays moving north in late Spring and moving south in late Fall.[citation needed]

Migration may be influenced by water temperature and sun orientation, which explains the seasonal migration pattern. Southern migration may be influenced by solar orientation and Northern migration may be influenced by the change in water temperature.[citation needed]

It is unknown whether their migratory behavior is due to feeding or premigratory mating activity.[2]

The cownose ray is also present in areas such as Maryland and Virginia, and can be seen migrating and schooling, as it is not uncommon for them to swim near the surface, despite feeding mostly on the bottom. These schools can be seen and migration tracked via airplane as it is easy to see the schools from the sky. However, while the migration patterns can tracked, the exact reason for migration is currently unknown.[6]

Habitat[edit]

Cownose rays appear naturally in the Eastern Atlantic Ocean, the Western Atlantic Ocean. Within the Eastern Atlantic Ocean, the cownose ray can often be found in Mauritania, Senegal, and Guinea. In the Western Atlantic Ocean they are located from Southern New England to Northern Florida in the United States, as well as throughout the Gulf of Mexico, Trinidad, Venezuela, and Brazil.[citation needed]

They live in brackish and marine habitats and can be found at depth up to 72 feet (22 m). They are gregarious and migrate extremely long distances, often traveling in schools.[citation needed]

Risk to Humans[edit]

Stingrays, including the cownose ray, can pose a low to moderate risk to humans. Rays will lash their tails when threatened, posing a risk of being whipped. If threatened, the cownose ray can also use their barb as a weapon to sting the aggressor. A sting from a cownose ray can cause a very painful wound that requires medical attention once stung. While the sting is not usually fatal, it can be fatal if  stung in the abdomen.[7] There is also a risk associated with eating meat from the sea animal that has not been prepared correctly. Shigella may be acquired from eating meat from a cownose ray that has been contaminated with the bacteria. This bacteria causes shigellosis, and can result in dysentery. Symptoms can include diarrhea, pain, fever, and possible dehydration.[5]

Predators[edit]

The cownose ray sits fairly high up on the food chain, and as a result only has a few natural predators. These predators include; cobia, bull sharks, and sandbar sharks, as well as of course; humans.[8]

Commercial Fishing[edit]

One solution to the cownose rays destruction of oyster beds as well as overpopulation in certain areas, is to open the ray up for commercial fishing. However, since the mean to fish them is difficult and expensive to obtain, and the meat of the rays has very little demand, this solution would most likely prove to be too expensive and yield too little of a profit for it to be a viable venture for any commercial fishermen, however, is often caught by hobby fishermen.[5]

Aquariums[edit]

Cownose rays can be seen in many public aquaria worldwide and are often featured in special 'touch tanks' where visitors can reach into a wide but shallow pool containing the fish which have had their barbs pinched or taken off (they eventually regrow, similar to human nails), making them safe enough to touch. The following aquariums and zoos are known to have a touch tanks featuring cownose rays (alone or with other fish):

USA

Canada

Dallas, TX Children's Aquarium at Fair Park

References[edit]

  1. ^ a b "Cownose Ray Facts". Saint Louis Zoo. Retrieved September 25, 2018.
  2. ^ a b c Kittle, Kimberly. "University of Florida". Rhinoptera bonasus. Florida museum of Natural History.
  3. ^ Puglisi, Melany P. (August 1, 2008). "Smithsonian Marine Station at Fort Pierce". Rhinopera bonasus.
  4. ^ a b c Ball, Michael (July 16, 2012). "Commercial Fishery Species Guide" (PDF). NOAA Fisheries Service Apex Predator Program. NOAA.
  5. ^ a b c "Rhinoptera bonasus". Florida Museum. Retrieved September 25, 2018.
  6. ^ "Age and growth, movements and distribution of the cownose ray, Rhinoptera bonasus, in Chesapeake Bay". Springer Link. Retrieved September 24, 2018.
  7. ^ "Stingray". Encyclopaedia Britannica. Retrieved September 25, 2018.
  8. ^ "Cownose Ray". Chesapeake Bay Program.
  9. ^ "Adventure Aquarium - Camden, NJ". www.adventureaquarium.com. Retrieved 23 August 2018.
  10. ^ "Stingray Touch - Arizona-Sonora Desert Museum".
  11. ^ "Cownose Ray - Atlantic City Aquarium".
  12. ^ "SeaTrek Helmet Diving at OdySea Aquarium". Retrieved 23 August 2018.
  13. ^ http://www.omahazoo.com/family/animal-presentations/default.aspx
  14. ^ writer, Carol Bicak / World-Herald staff. "You can touch a stingray at new exhibit at Omaha's Henry Doorly Zoo & Aquarium". Retrieved 23 August 2018.
  15. ^ "Petting Zoo - Rooster Cogburn Ostrich Ranch".
  16. ^ "The San Antonio Aquarium". Retrieved 2018-04-07.
  17. ^ "Texas State Aquarium". Retrieved 2017-08-16.
  18. ^ "Cownose Sting Ray". Retrieved 2011-01-09.
  19. ^ "Quebec Aquarium". Quebec Aquarium. Retrieved 1 August 2017.
  20. ^ "Ray Bay - Ripley's Aquarium of Canada". Ripley's Aquarium of Canada. Retrieved 1 August 2017.
  21. ^ "Vancouver Aquarium - Discover Rays". www.vanaqua.org.