Bat ray
Encyclopedia
The bat ray, Myliobatis californica, is an eagle ray
Eagle ray
The eagle rays are a group of cartilaginous fishes in the family Myliobatidae, consisting mostly of large species living in the open ocean rather than on the sea bottom....

 found in muddy or sandy sloughs, estuaries and bays, kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....

 beds and rocky-bottomed shoreline in the eastern Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, between the Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

 coast and the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...

. It is also found in the area around the Galápagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...

. The largest specimens can grow to a wingspan of 1.8 m and up and a mass of 91 kg and up. They more typically range from 9.07 kg-13.61 kg. Bat rays are euryhaline
Euryhaline
Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the molly which can live in fresh, brackish, or salt water. The European shore crab is an example of a euryhaline invertebrate that can live in salt and brackish water...

, i.e. they are able to live in environments with a wide range of salinities
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...

.

Diet

Bat rays feed on mollusks, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s 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.

Relation to humans

While the bat ray, like other stingray
Stingray
The stingrays are a group of rays, which are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae , Plesiobatidae , Urolophidae , Urotrygonidae , Dasyatidae , Potamotrygonidae The...

s, 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
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 but not the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. However, it is sometimes fished for sport for its fighting characteristics. Prehistorically, native tribes on the California coast (probably Ohlone
Ohlone
The Ohlone people, also known as the Costanoan, are a Native American people of the central California coast. When Spanish explorers and missionaries arrived in the late 18th century, the Ohlone inhabited the area along the coast from San Francisco Bay through Monterey Bay to the lower Salinas Valley...

), especially in the San Francisco Bay
San Francisco Bay
San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...

 area, fished bat rays in large numbers, presumably for food.

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.

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
Ovoviviparity
Ovoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch...

. 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.

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.
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