Thorny Stingray, Urotrygon rogersi

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, female giving birth.

Thorny Stingray, Urotrygon rogersi, an awesome tail spine.

Thorny Stingray, Urotrygon rogersi. Fish caught from coastal waters off Mazatlán, 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, photograph and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

Thorny Stingray, Urotrygon rogersi. Fish caught from coastal waters off Mazatlán, Sinaloa, October 2020.  Total Length: 81 cm (32 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Thorny Stingray, Urotrygon rogersi. Underwater photograph taken in Zihuantanejo Bay, Guerrero, March 2023. Photograph courtesy of Ron Woheau, Zihuantanejo.

The Thorny Stingray, Urotrygon rogersi, is a member of the American Round Stingray or Urotrygonidae Family, that are also known as the Lined Roundray and Roger’s Roundray and in Mexico as known raya redonda de púas and raya redonda de Rogers. Globally, there are thirteen species in the genus Urotrygon, of which five are found in Mexican waters, all in the Pacific Ocean.

The Thorny Stingray has an angular and somewhat diamond-shaped disc with a straight front margin and feature a slightly projecting pointed snout. As they mature, their disc becomes longer than they are wide and their snouts become more pointed. They are a uniform light brown to yellowish brown color without distinctive markings. Their ventral side is off white. Their head has small eyes and spiracles are on top and their mouths, nostrils, and gill slits are on the ventral side. 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 have a row of approximately 30 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 Stingray is a demersal species that reside over and within coastal sandy and muddy bottoms at depths up to 66 m (215 feet). They are most abundant at depths less than 15 m (50 feet) and move to greater depths during cold-water episodes. They reach a maximum of 51 cm (20 inches) in length, as established by a fish photographed above, 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. Reproduction occurs via internal fertilization with embryos developing via aplacental vivparity with a gestation period of 3 months. Their pups are born alive and resemble miniature adults that are independent at birth. The Thorny Stingray is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Thorny Stingray is found in all Mexican waters of the Pacific with the exception that they are absent from Magdalena Bay, Baja California Sur, northward along the central and northwest coasts of Baja.

The Thorny Stingray is mostly likely 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).

From a conservation perspective, the Thorny Stingray is currently considered to be Near Threatened. They are taken as a bycatch of large-scale and small-scale shrimp trawls and normally discarded. They are subject to intense fishing pressure in some regions with inadequate managed fisheries with their populations believed to be in significant decline.