Cownose ray

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Cownose ray
Rhinoptera bonasus Brest.jpg
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Myliobatiformes
Family: Rhinopteridae
Genus: Rhinoptera
Species:
R. bonasus
Binomial name
Rhinoptera bonasus
(Mitchill, 1815)

The cownose ray (Rhinoptera bonasus) is a species of Batoidea found throughout a large part of the western Atlantic and Caribbean, from New England, United States to southern Brazil (the East Atlantic populations are now generally considered a separate species, the Lusitanian cownose ray (R. marginata)). Male rays often reach about 2 and 1/2 feet in width. Females typically reach about 3 feet in width. However, there have been reports of rays up to 7 feet in width. Sizes change depending on the geographical range. Females will usually grow larger than males, allowing for larger offspring. These rays also belong to the order Myliobatiformes, a group that is shared by bat rays, manta rays, and eagle rays. [2]

Contents

In 2019, the species was listed as vulnerable on the IUCN Red List. [1]

Taxonomy

The genus name Rhinoptera is named for the Ancient Greek words for nose (rhinos) and wing (pteron). The species name bonasus comes from the Ancient Greek for bison (bonasos).

Description

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. [3] 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. [2]

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. [4]

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. [3]

Behavior

Diet and feeding

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 with a hardness comparable to that of cement, allowing them to eat hard shells. 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]

Predation

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, hammerhead sharks, and humans who like to fish for them. [6] [7]

Reproduction and lifespan

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. [8]

Cownose rays breed from April 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. [4]

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.

Migration

Cownose rays swimming in shallows in the Gulf of Mexico Cownose Rays.jpg
Cownose rays swimming in shallows in the Gulf of Mexico

The cownose ray often migrates from the Gulf of Mexico to Trinidad, Venezuela, and Brazil. [3] 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. [4]

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. [9]

The cownose ray has recently been spotted in the inland waters of the mid Atlantic island of Bermuda. [10]

Cownose stingray teeth and mouthparts. Stingray teeth consist of interlocking bars (dental plates) that crush food. Rhinoptera bonasus, cownose stingray teeth & mouthparts.jpg
Cownose stingray teeth and mouthparts. Stingray teeth consist of interlocking bars (dental plates) that crush food.

Habitat

Cownose rays appear naturally in the Eastern and 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 social creatures and migrate extremely long distances, often traveling in schools. [1]

Conservation status

The cownose ray is currently listed as vulnerable by the IUCN Red List due to extensive overfishing in the Caribbean. It is less threatened in the Gulf of Mexico and along the Atlantic coast of North America, but the species overall has still experienced steep population declines of 30–49% in only 43 years. Cownose ray killing contests have been banned in the state of Maryland. [1]

Relationship to humans

Risk to humans

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. [11] 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]

Fishing

One solution to the cownose rays' destruction of oyster beds, as well as their overpopulation in certain areas, is to open the ray up for commercial fishing. However, since the means to fish them are 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. It is, however, often caught by hobby fishermen. [5] In the Caribbean and along the Venezuelan coast, the ray is heavily overfished leading to declines of up to 49% of the population in the last 43 years. [1]

Aquariums

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 often 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 touch tanks featuring cownose rays (alone or with other fish):

USA

Canada

Related Research Articles

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Leafy seadragon Species of fish

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Newport Aquarium

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Short-tail stingray Species of cartilaginous fish

The short-tail stingray or smooth stingray is a common species of stingray in the family Dasyatidae. It occurs off southern Africa, typically offshore at a depth of 180–480 m (590–1,570 ft), and off southern Australia and New Zealand, from the intertidal zone to a depth of 156 m (512 ft). It is mostly bottom-dwelling in nature and can be found across a range of habitats from estuaries to reefs, but also frequently will swim into open water. The largest stingray in the world, this heavy-bodied species can grow upwards of 2.1 m (6.9 ft) across and 350 kg (770 lb) in weight. Its plain-colored, diamond-shaped pectoral fin disc is characterized by a lack of dermal denticles even in adults, and white pores beside the head on either side. The body can have colors as well as dark grey or black with rows of white spots along each wing. Its tail is usually shorter than the disc and thick at the base. It is armed with large tubercles and a midline row of large thorns in front of the stinging spine which has the dorsal and ventral fin folds behind.

Diergaarde Blijdorp

Diergaarde Blijdorp, officially Rotterdam Zoo, is a zoo located in the northwestern part of Rotterdam. It is one of the oldest zoos in the Netherlands, and has been operated by the Stichting Koninklijke Rotterdamse Diergaarde. Divided into several zoogeographic regions, the 26-hectare (64.25-acre) Blijdorp Zoo boasts well over 180 species. It also has a shop, multiple cafes, and an information centre.

Bluespotted ribbontail ray Species of cartilaginous fish

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Giant freshwater stingray Species of cartilaginous fish

The giant freshwater stingray is a species of stingray in the family Dasyatidae. It is found in large rivers and estuaries in Southeast Asia and Borneo, though historically it may have been more widely distributed in South and Southeast Asia. One of the largest freshwater fish and the largest stingray in the world, this species grows upwards of 1.9 m (6.2 ft) across and may reach 600 kg (1,300 lb) in weight. It has a relatively thin, oval pectoral fin disc that is widest anteriorly, and a sharply pointed snout with a protruding tip. Its tail is thin and whip-like, and lacks fin folds. This species is uniformly grayish brown above and white below; the underside of the pectoral and pelvic fins bear distinctive wide, dark bands on their posterior margins.

Pelagic stingray Species of cartilaginous fish

The pelagic stingray is a species of stingray in the family Dasyatidae, and the sole member of its genus. It is characterized by the wedge-like shape of its pectoral fin disc, which is much wider than long, as well as by the pointed teeth in both sexes, whip-like tail with extremely long tail spine, and uniform violet to blue-green coloration. It generally reaches 59 cm (23 in) in width. The pelagic stingray has a worldwide distribution in waters warmer than 19 °C (66 °F), and migrates seasonally to spend the summer closer to the continental shelf and at higher latitudes. The only stingray that almost exclusively inhabits the open ocean, this species is typically found in surface waters down to a depth of 100 m (330 ft). As a consequence of its midwater habits, its swimming style has evolved to feature more of a flapping motion of the pectoral fins, as opposed to the disc margin undulations used by other, bottom-dwelling stingrays.

Brazilian cownose ray Species of fish

The Brazilian cownose ray, also commonly called the Ticon cownose ray, is a species of fish in the family Rhinopteridae. Its range extends along the coast from the southern tip of Brazil to western Florida. Its natural habitats are shallow seas, estuarine waters, and intertidal flats.

<i>Rhinoptera</i> Genus of cartilaginous fishes

Rhinoptera is a genus of ray commonly known as the cownose rays. This genus is the only member of the family Rhinopteridae.

Golden cownose ray Species of ray

The golden cownose ray or Pacific cownose ray is a species of eagle ray, family Myliobatidae. It is found in the East Pacific along the coast of Colombia, Costa Rica, Ecuador, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, and Peru. Its natural habitats are open seas, shallow seas, subtidal aquatic beds, estuarine waters, intertidal marshes, and coastal saline lagoons. They are often in schools, and sometimes associated with the spotted eagle ray.

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Yellow stingray Species of stingray in the family Urotrygonidae

The yellow stingray is a species of stingray in the family Urotrygonidae, found in the tropical western Atlantic Ocean from North Carolina to Trinidad. This bottom-dwelling species inhabits sandy, muddy, or seagrass bottoms in shallow inshore waters, commonly near coral reefs. Reaching no more than 36 cm (14 in) across, the yellow stingray has a round pectoral fin disc and a short tail with a well-developed caudal fin. It has a highly variable but distinctive dorsal color pattern consisting of either light-on-dark or dark-on-light reticulations forming spots and blotches, and can rapidly change the tonality of this coloration to improve its camouflage.

Batoidea Superorder of cartilaginous fishes, commonly known as rays

Batoidea is a superorder of cartilaginous fishes, commonly known as rays. They and their close relatives, the sharks, comprise the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flattened bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their ventral surfaces.

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Ripleys Aquarium of Canada Public aquarium in Toronto, Ontario

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Euzetia occultum is a species of flatworm which parasitizes the gills of the Australian cownose ray and is the type species for its genus. It can be distinguished from Euzetia lamothei based on its overall size and reproductive morphology.

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