Bat Ray, Myliobatis californica
Bat Ray, Myliobatis californica. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, September 2013. Disc Size: 25 cm (10 inches) x 15 cm (5.9 inches). Tail: 42 cm (16.5 inches).
The Bat Ray, Myliobatis californica, is a member of the Eagle Ray or Myliobatidae Family, and is known in Mexico as tecolote. The Bat Ray received its common name from its pectoral fins which resemble bat wings. Globally, there are eleven species in the genus Myliobatis, of which five are found in Mexican waters, one in the Atlantic, three in the Pacific, and one in both the Atlantic and Pacific Oceans.
The Bat Ray has a flat triangularly-shaped body with a distinctive face. They are uniformly olive, dark brown or black dorsally and off-white ventrally with the exception of the undersides of their pectoral fins, which are dark (pictured below) and have no distinguishing marks. Their head is large, bulbous, and protruding with a blunt rounded snout that projects well before the disc. They have large eyes and spiracles on their sides, a mouth on the underside equipped with seven series of flat, pavement-like plates of strong teeth utilized for crushing and grinding prey. They have a single dorsal fin at the base of a slender and whip-like tail that can be as long as or up to three times longer than the body. Their tail has a spine located just behind the body that can have up to three venomous barbed spines used for self-defense. Their pectoral fins are bluntly pointed with concave rear margins. They have smooth skin without denticles.
The Bat Ray is a bottom dweller found in muddy and sandy bottomed bays, rocky bottoms, and kelp forests; they are found in both shallow waters and at depths up to 175 m (575 feet). Their maximum disc width is 1.8 m (5 feet 11 inches) and they can weight up to 108 kg (240 lbs). They are dimorphic with females being to three times larger than males. As of January 1, 2023, the International Game Fish Association world record stood at 82.1 kg (181 lbs) with the fish caught in coastal waters off the Huntington Beach Pier, Huntington Beach, California in June 1978. They are the most abundant and best studied of the Eagle Rays and therefore a significant amount of information is available about their lifestyle and behavioral patterns. They are more active at night traveling as solitary individuals or in large schools of up to 1,000 individuals with other Bat Rays or with species of other Eagle Rays. They are known to migrate to warmer inshore waters in the spring and early summer for breeding and pupping and then to cooler deeper waters during the summer. They generate speed by flapping their pectoral fins like birds. They are known to breach and also to skim along the surface for extended periods of time. They are opportunistic benthic feeders that stir the bottom with their pectoral fins in order to dislodge small crustaceans, small fish, mussels, and worms on which they feed. They crush clams and other mollusks with their teeth, spit out the shells, and consume the fleshy parts. In turn they are preyed upon by large sharks and sea lions, however, man is probably their most important predator. Reproduction occurs annually via aplacental viviparity with internal fertilization followed by an eight to twelve month gestation period with litter sizes of two to twelve pups born live. The pups are born tail first with their pectoral fins folded over their body and their tail spine enclosed in a protective sheath; their disc width averages 30 cm (12 inches) with an average weight of 1.0 kg (2.2 lbs). Larger fish have bigger litter sizes than smaller fish. They are fast growing and reach maturity fairly quickly. They have lifespans of up to twenty-four years.
The Bat Ray is a resident of all In Mexican waters of the Pacific Ocean with the exception that they are absent from along the coast of the mainland south of Mazatlán, Sinaloa. They are more common in the northern portions of the range and exceedingly rare in southern portions.
The Bat Ray is usually confused with the Manta Ray but lacks the arm-like cephalic fins present on either side of the Manta Ray’s head. They can also be confused with the Golden Cownose Ray, Rhinoptera steindachneri (red-brown color; large square head) and the Longnose Eagle Ray, Myliobatis longirostris (red-brown color; narrow pointed head with shovel-like snout; black rear margins of their disc).
From a conservation perspective the Bay Ray is currently considered to be of Least Concern with stable, widely distributed populations. Due to their strength and stamina, they are targeted by sports fishermen who use heavy tackle with shrimp, clams, or crabs as bait. They are a by-catch of demersal shrimp trawls, longlines, and gill nets and are normally discarded with a high mortality rate. There is a small commercial fishery for the Bat Ray in the northern part of Baja where they are consumed for food and also sold commercially on a limited basis. They were believed to be a pest to oyster growers in Northern California in the mid-1950’s and 43,000 Bat Rays were caught by various methods and removed from the environment. It was later discovered that the Bat Rays visited the oyster beds to consume Red Rock Crabs that were preying on the oysters, thus they were actually not guilty of oyster predation. The Bat Ray is used extensively in the aquarium trade with the majority being found in large public aquariums. At present there are no conservation measures in place for the Bat Ray. They are considered harmless to humans. Fossils of Bat Rays have been dated in excess of 1,000,000 years old. This species was believed to be an important food source for the Native Americans of California. Note: Rays of the genus Myliobatis have tails with a venomous spine. Although the Bat Rays are classified as “harmless to humans”, they are potentially dangerous as they can inflict wounds with intense pain and slow recovery. Approximately 1,500 stings from stingrays are reported annually.