Bat Ray, Myliobatis californica
The Bat Ray, Myliobatis californica, whose common Spanish name is tecolote, is a species in the family Myliobatidae, the Eagle Rays, known as águilas marinas in Mexico. The Bat Ray received its common name due to the pectoral fins that 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 oceans.
The Bat Ray has a flat triangularly shaped body with and a distinctive face. They are a uniform olive to dark brown to black in color dorsally and off white ventrally with the exception that the underside of the pectoral fins are dark (as pictured below) with no distinguishing marks. The head is large, bulbous and protruding with a blunt rounded snout that projects well before the disc. It has large eyes and spiracles on the side, a mouth on the underside equipped with seven series of flat, payment-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; the tail has a spine located just behind that body that can have up to three venomous barbed spines that is used for self-defense. The pectoral fins are bluntly pointed with concave rear margins. They have smooth skin without denticles.
The Bat Rays the most abundant and best studied of the Eagle Rays and therefore a significant amount of information is available about their life-styles and behavioral patterns. They are bottom dwellers found in muddy and sandy bottom bays, rocky bottoms, and kelp forests and found in both in shallow waters and to depths up to 575 feet. They reach a maximum of 180 cm (71 inches) in disc width and 108 kg (240 pounds) in weight. Females can be up to three times larger than males. The largest fish caught by a recreational angler in California weighed 82 kg (181 pounds). 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 moving to warmer inshore waters the spring and summer for breeding and pupping and then to cooler deeper waters during the summer. They generate speed by flapping their pectoral fins like a bird. They are known to breach and also to skim along the surface for extended periods of time. The Bat Rays are opportunistic benthic feeders that stir the bottom with their pectoral fins in order to dislodge small crustaceans, small fishes, 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 the most important predator. Reproduction is an annual event 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 live, tail first with their pectoral fins folded over their body and their tail spine enclosed in a protective sheath, with disc widths that average 30 cm (12 inches) and 1 kg (2 pounds). Larger fish have bigger litter sizes than smaller fish. Bat Fish are fast growing reaching maturity fairly quickly. They are found in all Mexican waters of the Pacific with the exception that they are absent from Mazatlán south along the west coast of the mainland. They are more common in the northern portions and exceedingly rare in the southern parts of these ranges. Bat Rays have life spans of up to 24 years.
The Bat Rays are usually confused with the manta rays but lack the arm-like cephalic fins present on either side of the head in mantas. They can be confused with the Longnose Bat-Eagle Ray, Myliobatis longirostris (red-brown in color, narrow pointed head with a shovel-like snout, and the aft edges of the disc are black) and the Golden Cownose Ray, Rhinoptera steindachneri (red-brown in color, large square head).
Bat Rays are used extensively in the aquarium trade with the majority found in large public aquariums. They are also targeted by sports fishermen due to their strength and stamina who use heavy tackle with shrimp, clams, or crabs as bait. They are a bycatch 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 northern parts of Baja where they are consumed for food and also sold on a limited basis commercially. They were believed to be a pest to oyster growers in Northern California in in the mid 1950’s and 43,000 bat rays were caught by various methods and removed from the environment. It turned out that the Bat Rays visited the oyster beds to consume the Red Rock Crabs that were preying on the oysters and are actually not guilty of predation of oysters. At present there are no conservation measures in place for the Bat Ray. They are considered to be harmless to humans.
Fossils of Bat Rays have been dated to be in excess of 1 million years old. This species was believed to be an important food source for Native Americans of California. Caution: Rays of the Genus Myliobatis have tails with a venomous spine. Although the Bat Ray is classified as “Harmless to Humans” these rays are potentially dangerous as they can inflict wounds with intense pain and slow recovery. I refer you to http://www.clubcruceros.org/StingrayInjuries.html for the treatment of Stingray injuries. Approximately 1,500 stings from stingrays are reported annually.