Bat ray

Bat ray
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Myliobatiformes
Family: Myliobatidae
Genus: Myliobatis
Species:
M. californica
Binomial name
Myliobatis californica
(T. N. Gill, 1865)
Range map

The bat ray (Myliobatis californica)[2][3][4] 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 and down to the Galápagos Islands.[5] The largest specimens can grow to a wingspan of 1.8 m (5 ft 11 in) and a mass of 91 kg (201 lb).[6] They more typically range from 9.07–13.61 kg (20.0–30.0 lb). The size of the bat ray is dependent on many factors, such as habitat alterations and different oceanographic and environmental conditions.[clarification needed] Some bat rays are solitary, while others form schools numbering in the thousands.[why?][7]

Ecology

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In the bat ray, the females are often bigger in size at sexual maturity than the males.[8] Predators of the bat ray include California sea lion, great white sharks and broadnose sevengill sharks. To keep themselves safe from predators, bat rays camouflage themselves by burying into the sand.[9][dubious – discuss]

Feeding

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Bat rays feed on mollusks like abalone and clams, crustaceans such as crabs, and small fish on the seabed, using their winglike pectoral fins to move sand and expose prey animals.[9] They may also use their snout to dig trenches up to 20 centimetres (7.9 in) deep and 4 metres (13 ft) long to expose buried prey, such as clams.[10] Bat ray teeth are flat and densely packed, often compared to pavement; they form tightly-packed rows that are used for crushing and grinding their often shelled prey, which they shuck out of their shells. As with all elasmobranchs, these teeth fall out and are replaced continuously.[5][6]

Life cycle

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Bat rays mate annually, in the spring or summer; females school together, with the receptive females "protecting" immature or fertilized females. The males determine whether the female is receptive (through chemical signals), after which the pair of rays swim with synchronized wingbeats, with the male swimming under the female. The male then inserts a clasper into the female's cloaca, fertilizing her eggs.[7]

Bat rays have a gestation period of nine to twelve months, being ovoviviparous. Litter sizes range from two to ten — pups are birthed tail first 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.[11] Nursery grounds include Sharks inlet in Morro Bay.[9] Bat rays live up to 23 years.[6]

Relationship with humans

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While the bat ray, like other stingrays, has a venomous spine near the base of their tail, the species is not considered dangerous and uses the spine only when attacked or frightened. Humans can avoid these spines by shuffling their feet when traversing shallow sand.[9]

Currently, the bat ray is fished commercially in Mexico but not the United States. 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.[12]

Commercial oyster 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 preyed on by bat rays) are principally responsible for oyster loss.[9] Bat rays are not considered endangered or threatened.[6]

Bat rays are popular in marine parks, often being featured in touch pools where visitors can stroke and pet the fish.

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References

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  1. ^ van Hees, K.; Pien, C.; Ebert, D.A.; Cailliet, G.M.; Smith, W.D. (2015). "Myliobatis californicus". IUCN Red List of Threatened Species. 2015: e.T39416A80677869. doi:10.2305/IUCN.UK.2015-4.RLTS.T39416A80677869.en. Retrieved 20 November 2021.
  2. ^ 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.
  3. ^ "Myliobatis californica". Integrated Taxonomic Information System. Retrieved 11 March 2006.
  4. ^ Froese, Rainer; Pauly, Daniel (eds.). "Myliobatis californica". FishBase. January 2006 version.
  5. ^ a b Florida Museum of Natural History. Bat Ray Biological Profile. Retrieved 2006-01-16.
  6. ^ a b c d Monterey Bay Aquarium Online Field Guide. Bat Ray. Retrieved 2012-06-14.
  7. ^ a b "Bat Rays ~ MarineBio Conservation Society". 2017-05-18. Retrieved 2022-10-20.
  8. ^ Hernandez-Herrera, A., Galvan-Magana, F., Patricia Ceballos-Vazquez, B., Pelamatti, T., García-Rodríguez, A., Hernández-Herrera, A., Galván-Magaña, F., Ceballos-Vázquez, B., & Tovar-Ávila, J. (2020). Estimation of the size at sexual maturity of the bat ray (Myliobatis californica) in northwestern Mexico through a multi-model inference. Fisheries Research, 231
  9. ^ a b c d e Program, Morro Bay National Estuary (2017-01-27). "Morro Bay Wildlife Spot Light: Bat Rays". Morro Bay National Estuary Program. Retrieved 2022-10-20.
  10. ^ Schmidt, Katie. "Myliobatis californica (Bat ray)". Animal Diversity Web. Retrieved 2022-10-20.
  11. ^ "The Pelagic Shark Research Foundation - Research - Methods". www.pelagic.org. Retrieved 2022-10-20.
  12. ^ 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.
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  • Photos of Bat ray on Sealife Collection
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