Bat ray

Bat ray
Bat ray off the Channel Islands, California
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Order:	Myliobatiformes
Family:	Myliobatidae
Genus:	Myliobatis
Species:	M. californica
Binomial name
Myliobatis californica (Gill, 1865)
Range map

The bat ray, Myliobatis californica,^[1][2][3] is an eagle ray found in muddy or sandy sloughs, estuaries and bays, kelp beds and rocky-bottomed shoreline in the eastern Pacific Ocean, between the Oregon coast and the Gulf of California. It is also found in the area around the Galápagos Islands.^[4] The largest specimens can grow to a wingspan of 1.8 m and up and a mass of 91 kg and up.^[5] They more typically range from 9.07 kg-13.61 kg. Bat rays are euryhaline, i.e. they are able to live in environments with a wide range of salinities.

Diet

Bat rays feed on mollusks, crustaceans and small fish on the seabed, using their winglike pectoral fins to move sand and expose prey animals. They may also dig trenches up to 20 cm deep to expose buried prey, such as clams. Bat ray teeth are flat and pavementlike, forming tightly-packed rows that are used for crushing and grinding prey—the crushed shells are ejected and the flesh consumed. As with all elasmobranchs, these teeth fall out and are replaced continuously.^[4][5]

Relation to humans

While the bat ray, like other stingrays, has a venomous spine in its tail (near the base), it is not considered dangerous and uses the spine only when attacked or frightened.

Currently, the bat ray is fished commercially in Mexico but not the United States. However, it is sometimes fished for sport for its fighting characteristics. Prehistorically, native tribes on the California coast (probably Ohlone), especially in the San Francisco Bay area, fished bat rays in large numbers, presumably for food.^[6]

Commercial growers have long believed bat rays (which inhabit the same estuarine areas favored for the industry) prey on oysters, and trapped them in large numbers. In fact, crabs (which are prey of bat rays) are principally responsible for oyster loss. Bat rays are not considered endangered or threatened.^[5]

Bat Rays are popular in marine parks, and visitors are often allowed to touch or stroke the ray, usually on the wing.

Life cycle

Bat ray reproduction is ovoviviparous. They mate annually, in the spring or summer, and have a gestation period of nine to twelve months. Litter sizes range from two to ten — pups emerge with their pectoral fins wrapped around the body, and the venomous spine is flexible and covered in a sheath which sloughs off within hours of birth. Bat rays live up to 23 years.^[5][7]

Bat rays copulate while swimming with synchronized wingbeats—the male under the female. The male inserts a clasper into the female's cloaca, channeling semen into the orifice to fertilize her eggs.^[7]

Gallery

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  Bat ray adopting a feeding posture.

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  Bat ray in kelp forest, San Clemente Island.

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  Bat ray off Pt. Lobos.

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  Bat ray at the Monterey Bay Aquarium.

References

1. ^ Gill, T.N. (1865). "Note on the family of myliobatoids, and on a new species of Aetobatis". Ann. Lyc. Nat. Hist. N. Y. 8, 135–138.
2. ^ "Myliobatis californica". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=160981. Retrieved 11 March 2006. 
3. ^ Froese, Rainer, and Daniel Pauly, eds. (2006). "Myliobatis californica" in FishBase. January 2006 version.
4. ^ ^{a b} Florida Museum of Natural History. Bat Ray Biological Profile. Retrieved 2006-01-16.
5. ^ ^{a b c d} Monterey Bay Aquarium Online Field Guide. Bat Ray. Retrieved 2006-01-16.
6. ^ Gobalet, Kenneth W., Peter D. Schulz, Thomas A. Wake and Nelson Siefkin (2004). "Archaeological perspectives on native American fisheries of California, with emphasis on steelhead and salmon". Transactions of the American Fisheries Society 133 (4), 801–833.
7. ^ ^{a b} MarineBio.org. Bat Ray. Retrieved 2006-01-16