One of the less common stingrays within its range, the sharpsnout stingray is found in nearshore, brackish waters along the northeastern coast of South America, from Venezuela and Trinidad and Tobago to northern Brazil; many occur in the estuarine area affected by the freshwater discharge of the Amazon River. It favors muddy habitats deep, with low visibility. However, Uyeno et al. gave a depth of for this species. The sharpsnout stingray conducts annual movements that are affected by salinity, entering coastal bays such as Marajó Bay during the rainy season and shifting to offshore waters during the rainy season.
Description
The pectoral fin disc of the sharpsnout stingray is about as wide as long, with strongly concave leading margins and rounded corners. The snout is long and projecting, measuring 39-54% as long as the disc is wide. The eyes are minute and followed by much larger spiracles. There is a flap of skin between the nares, with a finely fringed posterior margin. The line of the mouth is slightly indentedat the center. The upper and lower jaws both contain 56-68 tooth rows; the teeth are blunt and arranged with a quincunx pattern. A transverse row of 5 papillae are present on the floor of the mouth. The pelvic fins are distinctive, being over twice as long as wide with a gently sinuous trailing margin, and tapering to an acute tip that sometimes extends past the disc. The whip-like tail measures over twice the length of the disc and bears 1-2 serrated spines on top. Posterior to the spines are a subtle dorsal keel and a ventral fin fold about half as long as the disc. A band of small tubercles runs along the dorsal midline from behind the eyes to the base of the tail, with larger tubercles in a central row and on each "shoulder". More conical tubercles are scattered over the upper surface of the tail past the spines. The coloration is a uniform brown above, and white below darkening towards the disc margin. This species typically attains a disc width of, but individuals up to across have been recorded.
Biology and ecology
The sharpsnout stingray feeds on small burrowing invertebrates such as worms, crustaceans, and molluscs, excavating them from the substrate and grinding them apart with its pavement-like teeth. Like other stingrays, this species is aplacental viviparous, with females giving birth to 1-3 young every year. Similarly to the Colares stingray, the annual movements of this ray may relate to reproduction as most females found near the coast are newly impregnated. Younger individuals have proportionately longer tails than adults.
Human interactions
The sharp, venomous tail spines of the sharpsnout stingray are potentially hazardous to humans. This species is caught by hook-and-line or in nets; it is used for food by subsistence fishers, but is not favored because its flesh is a dark reddish color. Sharpsnout stingrays also form part of the bycatch of artisanal and commercial fisheries targeting large catfish in the Amazon estuary, while increasing interest in using stingrays for minced fish products may intensify fishing pressure on this species in the future. Because of these threats and the slow reproductive rate of this ray, the International Union for Conservation of Nature has assessed it as Near Threatened.
