Diamond Stingray

The diamond stingray attains a disc width of 1 m (3.3 ft) or possibly 1.2 m (3.9 ft); females grow larger than males. Its pectoral fin disc is rhomboid in shape, slightly wider than long, with angular outer corners and subtly convex margins. The snout is blunt-angled and non-projecting. The eyes are fairly large and immediately followed by the spiracles (paired respiratory openings). The mouth is strongly curved, containing 21–37 upper tooth rows and 23–44 lower tooth rows; the teeth are small and blunt, and arranged into flattened surfaces. Three or five papillae (nipple-like structures) are found in a row across the floor of the mouth.

The diamond stingray is found in the eastern Pacific Ocean from southern California to northern Chile, as well as around the Galápagos and Hawaiian Islands; it is very abundant around Baja California and in the Gulf of California. At the northern and southern extremes of its range, it is generally only present during periods of suitably warm water brought about by El Niño. There is a record of this ray from off British Columbia, which is unconfirmed and would be highly anomalous as it is known to be a tropical and warm-temperate species.

The diamond stingray is most active at night, spending much of the day buried in sand with only its eyes protruding. When foraging for food, it may be solitary but more commonly forms groups numbering up to the hundreds. There is strong segregation by sex and age. This species feeds on crustaceans, molluscs, and other invertebrates, as well as small bony fishes; its powerful jaws and molar-like teeth allow it to crush hard-shelled prey. It mainly targets burrowing organisms, but may also take prey exposed on the bottom. There is a record of a female 69 cm (27 in) across, that had gorged herself on at least 30 small crabs. In the Bahía Magdalena lagoon complex, Baja California Sur, its most important source of food are pea crabs, followed by the razor clam Solyema valvulus, and then polychaete worms.

At least one fatality off southern California has resulted from the long, venomous tail spine of the diamond stingray. However, it is not aggressive and will usually flee given the opportunity. This ray is not found off the United States in sufficient numbers to be economically important. Elsewhere in its range, it is caught in substantial numbers for human consumption, both intentionally and as bycatch; the pectoral fins or "wings" are sold fresh or filleted and salted. The International Union for Conservation of Nature (IUCN) notes that the diamond stingray's low reproductive productivity renders it susceptible to population depletion, and assesses it as Vulnerable overall.