Golden Cownose Ray, Rhinoptera steindachneri
Golden Cownose Ray, Rhinoptera steindachneri. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, April 2008. Disc width: 57 cm (23 inches). Disc length: 27 cm (11 inches). Tail: 39 cm (16 inches). Spines: 4.0 cm (1.6 inches) and 2.5 cm (1.0 inch).
Golden Cownose Ray, Rhinoptera steindachneri. Fish provided by the commercial fishermen of Bahía Kino, Sonora, March 2015. Disc width: 51 cm (20 inches). Disc length: 33 cm (13 inches). Tail: 37 cm (15 inches). Photograph courtesy of Maria Johnson, Prescott College Kino Bay Center, Kino Bay, Sonora.
Golden Cownose Ray, Rhinoptera steindachneri. Fish caught in coastal waters north of Puerto Los Cabos, Baja California Sur, November 2002. Disc width: 71 cm (2 feet 4 inches). Weight: 6.8 kg (15 lbs). Caught out of a school of about fifty individuals which were clearly visible and initially appeared as square stepping stones on the bottom.
Golden Cownose Ray, Rhinoptera steindachneri. Underwater photographs taken in Zihuantanejo Bay, Guerrero, March 2018 and January 2023. Photographs courtesy of Ron Woheau, Zihuantanejo.
The Golden Cownose Ray, Rhinoptera steindachneri, is a member of the Cownose Ray or Rhinopteridae Family, and is known in Mexico as gavilán dorado. Globally, there are ten species in the genus Rhinoptera, of which three are found in Mexican waters, two in the Atlantic and one in the Pacific Ocean.
The Golden Cownose Rays has a body that has a diamond-shaped disc that is 1.7 to 1.8 times wider than they are deep. They are golden yellowish-brown dorsally and off-white ventrally with black on the tips of their wings. Their head is distinctly protruding with an overhanging snout that is deeply notched in the front. They have “wings” attached to the front and sides of their head. They have large spiracles directly behind, and approximately equal in size to, their eye cavity. Their mouth has 6 to 9 plate-like teeth on the top and bottom that are specialized for crushing and grinding hard-bodied prey. They have a small single dorsal fin at the base of their slender whip-like tail. Their tail is 1.2 to 1.6 times longer than the disc length and contains one or two long venomous spines inserted close to the tail base with injecting barbs used for self-defense. Their pectoral fins are long and pointed with curved tips and concave rear margins. They have no caudal fin. Their skin is smooth and lacks denticles and thorns.
The Golden Cownose Ray is an inshore species found in bays and coastal lagoons over sandy bottoms near rock structures and coral reefs at depths up to 66 m (215 feet). The Golden Cownose Ray has a maximum disc width of 1.07 m (3 feet 6 inches), disc length of 75 cm (30 inches), and total length of 1.70 m (5 feet 5 inches). They are highly migratory and travel in large schools with synchronous movements resembling birds in flight. They migrate to the northern portions of the Sea of Cortez in the spring and return south in the fall. They primarily consume mollusks and crustaceans. Reproduction occurs via aplacental viviparity with internal fertilization. Embryos are initially fed on yolk then receive additional nourishment from the mother by indirect adsorption of uterine fluid enriched with mucus, fat, and protein. Each female produces just one pup per year that is born live as a miniature adult having a disc width of just over 1 m (3 feet 4 inches). Gestation requires one year. The Golden Cownose Ray 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 Golden Cownose Rays is a resident of all Mexican waters of the Pacific Ocean.
The Golden Cownose Ray is most likely confused with the Bat Ray, Myliobatis californica (black coloration; raised head; blunt pectoral fins with pointed tips). It is also very similar to the Cownose Ray, Rhinoptera bonasus, an Atlantic Ocean species.
From a conservation perspective the Golden Cownose Ray is currently considered to be Near Threatened and their long-term viability is of concern. Although not well assessed their populations are believed to be in decline, being adversely affected by a variety of factors including inshore habitat destruction to accommodate shrimp farming, schooling behavior, intense fishing pressure with large nets, long reproduction times with small litter sizes, and poorly documented and unregulated fishery. The Golden Cownose Ray is frequently caught by artisanal fishermen, commercial fishermen of the greater Magdalena Bay, Baja California Sur, and northern Sea of Cortez areas in gill nets and longlines, and as a by-catch of shrimp trawlers. They are sold and used primarily in fish tacos. Note: Rays of the genus Rhinoptera have a venomous spine on their tail. The Golden Cownose Rays are potentially dangerous as they can inflict wounds with intense pain and slow recovery. Please refer to http://www.emedicinehealth.com/stingray_injury/article_em.htm for the treatment of stingray injuries. Approximately 1,500 stings from stingrays are reported annually.