| Blue stingray | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Superorder: | Batoidea |
| Order: | Myliobatiformes |
| Family: | Dasyatidae |
| Genus: | Dasyatis |
| Species: | D. chrysonota |
| Binomial name | |
| Dasyatis chrysonota (A. Smith, 1828) | |
The blue stingray (Dasyatis chrysonota) is a species of whiptail stingray of the family Dasyatidae often found in the coastal waters of southern Africa. [2]
The species' common geographical distribution ranges from St. Lucia on the southern tip of Africa up to Angola [2] and a depth distribution ranging from the surf zone to 110m depth. [3] Although this is the typical geographical distribution, the species has also been found off the Mediterranean coast of Israel and in the Gulf of Gabčs in southern Tunisia. [4] D. chrysonota is easily distinguishable from other stingray species by the appearance of faint blue splotches and lines on its light-brown triangular disc body. [2]
Their disc can reach a maximum width of approximately 75 cm. [2] There are four size classes: small, medium, large, and very large. The ranges of each size class are as follows: small = <30 cm, medium = 30–45 cm, large = 45–60 cm, very large = >60 cm. [5] The size of male and female blue stingray show no distinction from birth until adolescence (approximately 4 years old) in which sexual differences become noticeable. Once this threshold is reached, females exhibit a faster growth rate than males. The minimum age-at-maturity is 5 for males and 7 for females. Age estimates of D. chrysonota are often made based on the vertebral centra which exhibits narrow dark bands and wide translucent bands that create a bunching effect. Seasonal fluctuations in temperature and light are likely significant controlling factors in growth rate and band formation. Months with warm temperatures often show higher growth rates than months with cold temperatures. One opaque and one translucent band is formed annually when the stingray is kept in captivity, [2] which is also true for other closely related species such as Dasyatis dipterura , the diamond stingray. [6]
The species occupies different habitats throughout their lifetime and although they may feed on a wide variety of prey items, the proportions of the different prey could vary among different life stages and corresponding size classes. This could be a result of what is and isn't accessible to a small stingray versus a relatively large stingray that is able to dig deeper into sediment and extract particular types of prey like the bat ray (Myliobatis californica) is able to do. D. chrysonota feed on a wide variety of benthic epifauna and infauna with an opportunistic feeding strategy. Although primary prey type changes between size classes of the stingray and the habitat that it feeds in, the main prey groups are crustaceans, molluscs, polychaetes and hemichordates. Crustaceans and molluscs are the most common prey among other closely related species of stingray. The feeding process includes prey searching, prey detection, and prey capture. Prey is searched for by gliding along the surface of the ocean, and once it is found the stingray lands upon the prey and the prey is drawn into its mouth with use of the jaw. The medium and large size classes of D. chrysonota are important predators in the nearshore sandy beach ecosystem in the surf zone of southern African waters, however the majority of prey for the very large class size is found nearshore and offshore, mostly consisting of Callianassa spp. which does not occur in the surf zone. [5]
Sexual maturity of males is reached at a smaller size and at an earlier age than that of females. The reproductive cycle of the male blue stingray indicates a peak in sperm production from the month of September until December, resulting in a mating season consisting mostly of the austral spring and some of the austral summer. D. chrysonota have a relatively low fecundity which ranges from 1 to 7, with an average of 2–3 embryos per litter. Unlike other related ray species, a strong maternal size to litter size relationship does not exist. This may be related to uterus capacity of this species. Courtship and mating behavior of D. chrysonota is a rare occurrence. The species follows an annual reproductive cycle with birth following a nine-month gestation period. Ovulation appears to start soon after parturition, with ovulation and hence fertilization occurring between January and April. An offshore winter migratory pattern in which the rays are found inshore in the summer and disperse offshore during winter months coincides with their reproductive seasonality. Large ovarian eggs may range from 8–14 mm in diameter. The reproductive success of D. chrysonota is low based on average fecundity and active reproductive life span. [3]
D. chrysonota is a popular target species for recreational and competitive rock and surf anglers as well as recreational ski boat fishers. [7] The species is at risk of over-exploitation as there is currently no proper management strategy in place for the protection of the species. [3]
Stingrays are a group of sea rays, which are cartilaginous fish related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes and consist of eight families: Hexatrygonidae, Plesiobatidae, Urolophidae (stingarees), Urotrygonidae, Dasyatidae, Potamotrygonidae, Gymnuridae and Myliobatidae . There are about 220 known stingray species organized into 29 genera.
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. One of the largest stingrays 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.
The round ribbontail ray or blotched fantail ray, is a species of stingray in the family Dasyatidae, found throughout the nearshore waters of the tropical Indo-Pacific, as well as off islands in the eastern Pacific. It is a bottom-dwelling inhabitant of lagoons, estuaries, and reefs, generally at a depth of 20–60 m (66–197 ft). Reaching 1.8 m (5.9 ft) across, this large ray is characterized by a thick, rounded pectoral fin disc covered by small tubercles on top, and a relatively short tail bearing a deep ventral fin fold. In addition, it has a variable but distinctive light and dark mottled pattern on its upper surface, and a black tail.
The bluespotted ribbontail ray is a species of stingray in the family Dasyatidae. Found from the intertidal zone to a depth of 30 m (100 ft), this species is common throughout the tropical Indian and western Pacific Oceans in nearshore, coral reef-associated habitats. It is a fairly small ray, not exceeding 35 cm (14 in) in width, with a mostly smooth, oval pectoral fin disc, large protruding eyes, and a relatively short and thick tail with a deep fin fold underneath. It can be easily identified by its striking color pattern of many electric blue spots on a yellowish background, with a pair of blue stripes on the tail.
The Atlantic stingray is a species of stingray in the family Dasyatidae, common along the Atlantic coast of North America from Chesapeake Bay to Mexico, including brackish and freshwater habitats. It may be distinguished from other stingrays in the area by its relatively elongated snout. This species is of little commercial importance, other than for sale in the aquarium industry.
Kuhl's maskray, also known as the blue-spotted stingray, blue-spotted maskray, or Kuhl's stingray, is a species of stingray of the family Dasyatidae. It was recently changed from Dasyatis kuhlii in 2008 after morphological and molecular analyses showed that it is part of a distinct genus, Neotrygon. The body is rhomboidal and colored green with blue spots. Maximum disk width is estimated 46.5 cm (18.3 in). It is popular in aquaria, but usually not distinguished from the blue-spotted ribbontail ray. The ribbontail has a rounded body, is a brighter green with brighter blue and more vivid spots, but Kuhl's maskray is larger. The stingray's lifespan is estimated at 13 years for females and 10 years for males. The blue-spotted stingray preys on many fish and small mollusks. It is also generally found from Indonesia to Japan, and most of Australia. Kuhl's maskray also is targeted by many parasites, such as tapeworms, flatworms, and flukes.
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.
The red stingray is a species of stingray in the family Dasyatidae, found in the northwestern Pacific Ocean off Japan, Korea, and China, and possibly elsewhere. It primarily inhabits shallow, sandy habitats close to shore, and has been known to enter brackish water. The red stingray has a diamond-shaped pectoral fin disc and gains its common name from its bright orange-red underside; there may also be patches of orange at various spots on its upper surface. Most individuals are no more than 1 m (3.3 ft) long.
The plain maskray or brown stingray, is a species of stingray in the family Dasyatidae. It is found in shallow, soft-bottomed habitats off northern Australia. Reaching 24 cm (9.4 in) in width, this species has a diamond-shaped, grayish green pectoral fin disc. Its short, whip-like tail has alternating black and white bands with fin folds above and below. There are short rows of thorns on the back and the base of the tail, but otherwise the skin is smooth. While this species possesses the dark mask-like pattern across its eyes common to its genus, it is not ornately patterned like other maskrays.
The Colares stingray, Fontitrygon colarensis, is a species of stingray in the family Dasyatidae, native to the shallow brackish waters of the Amazon River estuary in northern Brazil. This species inhabits inshore bays during the dry season and moves away from the coast in the rainy season. It is characterized by a rhomboid pectoral fin disk, elongated snout, and a dark band on the lower lip. A fairly large species, males and females attain disk widths of 63 cm (25 in) and 91 cm (36 in) respectively. Females give birth to 1–4 young, possibly annually. Colares stingrays are both targeted and caught as bycatch by Brazilian artisanal and commercial fisheries; these pressures coupled with its small range and slow reproductive rate has led the International Union for Conservation of Nature (IUCN) to list this species as critically endangered.
The diamond stingray is a species of stingray in the family Dasyatidae. It is found in the coastal waters of the eastern Pacific Ocean from southern California to northern Chile, and around the Galápagos and Hawaiian Islands. This bottom-dweller generally inhabits sandy or muddy flats near rocky reefs and kelp forests, to a depth of 30 m (98 ft), though off Hawaii it may range considerably deeper. As its common name suggests, this species has an angular, diamond-shaped pectoral fin disc that is plain brown or gray above, with rows of tubercles along the midline and on the "shoulders". The long, whip-like tail has both dorsal and ventral fin folds, which distinguish this ray from the closely similar longtail stingray. It typically grows to 1 m (3.3 ft) across.
The estuary stingray, also called the estuary stingaree or brown stingray, is a species of stingray in the family Dasyatidae. Endemic to eastern Australia, it typically inhabits shallow, mangrove-lined tidal rivers, estuaries, and bays in southern Queensland and New South Wales. This yellow-brown to olive ray grows to at least 93 cm (37 in) across. It has a diamond-shaped pectoral fin disc and a mostly smooth, whip-like tail bearing both dorsal and ventral fin folds. It can additionally be identified by its long, narrow nostrils and the row of thorns along the midline of its back.
The sharpsnout stingray or wingfin stingray is a species of stingray in the family Dasyatidae, found from off Venezuela to northern Brazil. It inhabits shallow, brackish water, shifting towards the coast in the dry season and away from it in the rainy season. Typically measuring 70 cm (28 in) across, this dark brown ray is easily identifiable by its long, projecting snout and elongated, acutely pointed pelvic fins. Its diet consists of bottom-dwelling invertebrates. Reproduction is aplacental viviparous, with females bearing one to three pups annually. Naturally uncommon and slow-reproducing, the sharpnose stingray is under pressure by both artisanal and commercial fisheries, leading the International Union for Conservation of Nature (IUCN) to assess it as critically endangered.
The longnose stingray is a species of stingray in the family Dasyatidae, native to the western Atlantic Ocean from the southern Gulf of Mexico to Brazil. Found in coastal waters no deeper than 36 m (118 ft), this demersal species favors muddy or sandy habitats. The longnose stingray is characterized by its angular, rhomboid pectoral fin disc, moderately projecting snout, and whip-like tail with a dorsal keel and ventral fin fold. It typically grows to 1.25 m (4.1 ft) across and is brownish above and light-colored below.
The Brazilian large-eyed stingray, Hypanus marianae, is a species of stingray in the family Dasyatidae. Endemic to northeastern Brazil, adults of this species inhabit shallow coral and sandstone reefs while the young are also found near beaches and in estuaries. This stingray measures up to 40 cm (16 in) across and can be identified by its large eyes, equally long fin folds above and below the tail, and distinctive coloration consisting of various dark brown markings on a yellowish-brown background above, and two pairs of dark brown blotches on a white background below. Reproduction is aplacental viviparous, with females giving birth to one young at a time, twice a year, and using sandbanks as nursery areas. The Brazilian large-eyed stingray is collected by artisanal fisheries and for the ornamental fish trade.
The pale-edged stingray or sharpnose stingray is a species of stingray in the family Dasyatidae, found in the Indian and Pacific Oceans from India to the western Malay Archipelago and southern Japan. This bottom-dwelling ray is most commonly found over sandy areas shallower than 100 m (330 ft), as well as in estuaries. Measuring up to 29 cm (11 in) across, the pale-edged stingray has a diamond-shaped pectoral fin disc, a long projecting snout, small eyes, and a whip-like tail with both dorsal and ventral fin folds. It is chocolate brown above and white below.
The Broad stingray, also known as the Brown stingray or Hawaiian stingray, is a species of stingray in the family Dasyatidae. The predominant species of stingray in the inshore waters of the Hawaiian Islands, this benthic fish typically inhabits sandy or muddy flats at depths greater than 15 m (49 ft). Usually growing to 1 m (3 ft) across, the broad stingray has a wide, diamond-shaped pectoral fin disc with a protruding snout tip and a long tail with a ventral fin fold. At night, this species actively forages for bottom-dwelling invertebrates and bony fishes, often near the boundaries of reefs. Reproduction is aplacental viviparous. As substantial threats to its population exist in many areas of its wide distribution, IUCN has listed this species as Vulnerable.
The common stingray is a species of stingray in the family Dasyatidae, found in the northeastern Atlantic Ocean and the Mediterranean and Black Seas. It typically inhabits sandy or muddy habitats in coastal waters shallower than 60 m (200 ft), often burying itself in sediment. Usually measuring 45 cm (18 in) across, the common stingray has a diamond-shaped pectoral fin disc slightly wider than long, and a whip-like tail with upper and lower fin folds. It can be identified by its plain coloration and mostly smooth skin, except for a row of tubercles along the midline of the back in the largest individuals.
The roughtail stingray is a species of stingray in the family Dasyatidae, with separate populations in coastal waters of the northwestern and southwestern Atlantic Ocean. This bottom-dwelling species typically inhabits sandy or muddy areas with patches of invertebrate cover, at a depth of 15–50 m (49–164 ft). It is seasonally migratory, overwintering in offshore waters and moving into coastal habitats for summer. The largest whip-tail stingray in the Atlantic, the roughtail stingray grows up to 2.6 m (8.5 ft) across and 360 kg (800 lb) in weight. It is plain in color, with an angular, diamond-shaped pectoral fin disc and a long, whip-like tail bearing a subtle fin fold underneath. The many thorns on its back and tail serve to distinguish it from other stingrays that share its range.
The daisy stingray, Fontitrygon margarita, is a little-known species of stingray in the family Dasyatidae, found in shallow waters along the coast of West Africa. This species typically grows to 60 cm (24 in) across and has a rounded pectoral fin disc and a wide band of dermal denticles over its back. It is characterized by a greatly enlarged, nacreous denticle in the middle of its back called a "pearl spine"; this feature is shared with the similar but much smaller pearl stingray, which has often been confused with this species. The daisy stingray feeds mainly on crustaceans and exhibits aplacental viviparity, with litters of 1–4 young. Heavily pressured by fisheries and possibly habitat degradation, this once-common species is declining and has been assessed as Vulnerable by the International Union for Conservation of Nature (IUCN).
