Thorny Stingray, Urotrygon rogersi
The Thorny Stingray, Urotrygon rogersi, whose common Spanish name is raya redonda de púas, is a member of the American Round Stingray or Urotrygonidae Family, known collectively as raya redondas Americanas in Mexico. Globally, there are thirteen species in the genus Urotrygon, five of which are found in Mexican waters, all in the Pacific.
These fish have angular and somewhat diamond-shaped discs with straight front margins and feature a slightly projecting pointed snout. As they mature, their discs become longer than they are deep and their snouts become more pointed. They are a uniform light brown to yellowish brown color without distinctive markings. Their undersides are off white. Their small eyes and spiracles are on top of their heads and their mouths, nostrils, and gill slits are on their ventral sides. Their slender tails are longer than half their total body length and their narrow pointed caudal fins have a rounded end. They are covered with small denticles, which are found on the snout, along the margin of the disc, behind the scapular region at the mid-line of the disc, and in longitudinal rows on top of the body. They also feature a row of approximately thirty thorns that run from the nape along the middle of the back and on top of the tail to the stinger. Their large venomous spine is found mid-tail.
The Thorny Stingrays reside over and within coastal sandy and muddy bottoms at depths up to 215 feet. They are most abundant at depths less than 50 feet and move to greater depths during cold-water episodes. They reach a maximum length of 51 cm (20 inches), as established by a fish in my possession, with a maximum disc width of 33 cm (13 inches). They seek food by stirring bottom sediment with their pectoral fins to dislodge small crustaceans, small fish, mussels, and worms on which they feed. Their pups are born alive and are miniature adults that are independent at birth. They are a rare and poorly studied species and as such very limited information is available about their behavioral patterns.
In Mexican waters the Thorny Stingrays are found in all waters of the Pacific with the exception that they are absent from Magdalena Bay northward along the central and northwest coasts of Baja.
The Thorny Stingray can be confused with the Blotched Stingray, Urotrygon chilensis (dark gray to black spots on the back, tail longer than disc length), the Panamic Stingray, Urotrygon aspidura (no thorns on the back; 6 large thorns on the tail), and the Spiny Stingray, Urotrygon munda (18 to 32 recurved spines along the mid-back that extend from mid-disc to the tail spine).
The Thorny Stingray is a rare species seldom seen by humans. From a fishing perspective, they are only retained by subsistence fishermen and typically considered a “catch and release.”
Thorny Stingray, Urotrygon rogersi, stillborn fetus. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, June 2012. Total Length: 16 cm (6.3 inches). Disc: 9.3 cm (3.7 inches) x 8.0 cm (3.1 inches). Tail: 8.5 cm (3.3 inches).
Thorny Stingray, Urotrygon rogersi, female. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, June 2012. Total Length: 51 cm (20 inches). Disc: 33 cm (13 inches) x 29 cm (11 inches). Tail: 26 cm (10 inches).
Thorny Stingray, Urotrygon rogersi. Fish caught from coastal waters off Mazatlan, Sinaloa, October 2017. Total Length: 46 cm (18 inches). Disc: 25 cm (10 inches) x 23 cm (9.2 inches). Tail: 14 cm (5.3 inches).Catch, photo and identification courtesy of Josh Leisen (lifelistfishing.com), Gaylord, MI.