Common name(s)
Bat Ray, California Bat Ray.
Identification
A large eagle ray with a kite-shaped disc (less than 2x wider than long) and large protruding head with a short, fleshy, broadly rounded rostral lobe that joins pectoral fins below eyes. Spiracles large, positioned laterally, barely visible from above. Nasal curtain short and wide with a long fringe along posterior margin, without deep central notch.
Pectoral fins have straight anterior margins, mildly concave posterior margins, and rounded apices. Pectoral fins originate below eye. Disc entirely smooth, lacking denticles or thorns. Pelvic fins large, extending beyond disc margin. One small dorsal fin with a broadly rounded apex and a short free rear tip, positioned midway between tail base and caudal sting. Tail broad based and long, tapering abruptly to caudal sting then filamentous to tip. Tail length more than 2x disc width when intact. One caudal sting usually present.
Colour
Dorsum brownish grey, olive grey, or blackish, without markings. Ventrum white with dusky or dark pectoral apices.
Size
Maximum disc width 180cm. Disc width at birth 20-31cm.
Habitat
Tropical to warm temperate seas. Shallow sandy or muddy bays, rocky reefs, estuaries, and kelp forests. Intertidal to at least 108m but usually in shallow water.
Distribution
Eastern Pacific. Oregon to southern Baja and throughout the Sea of Cortez. Possibly also to the Galapagos Islands.
Conservation Status
LEAST CONCERN
The bat ray is caught in artisanal multi-species elasmobranch fisheries in México, is obtained as bycatch in demersal trawls, longlines, and gillnets in the United States and México, is caught in recreational fisheries in the United States, and was historically targeted in the United States. There are no reliable population estimates, however this species has been recorded in artisanal elasmobranch fishery surveys in the Gulf of Mexico and in species-specific landings in California. In artisanal elasmobranch fisheries, this species was relatively common in catches along the mainland coast of Mexico (Sorona), and much less common in catches from the Baja peninsula. Commercial bycatch landings of this species have generally increased from 2001-2014, and recreational fishing surveys suggested that population abundance increased from the 1950s to the 1990s, which has been reinforced by recent fisheries-independent surveys from 2013 to 2014. Additionally, fisheries in California that historically targeted this species as a nuisance, ceased in 1994.
Given the fast growth and early maturity of this species, as well as patterns that suggest an increase in abundance in Californian waters, and commonality in catches along the mainland coast of Mexico, this species is considered to be Least Concern. However, it is unknown if the rarity of this species in the Baja peninsula suggest natural low abundance or is a result of overfishing, so overall population trend remains unknown. Improved recording and monitoring of landings in Mexican artisanal and industrial fisheries are needed.
Citation
Van Hees, K., Pien, C., Ebert, D.A., Cailliet, G.M. & Smith, W.D. 2015. Myliobatis californicus. The IUCN Red List of Threatened Species 2015: e.T39416A80677869. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T39416A80677869.en. Downloaded on 06 March 2021.
Reproduction
Matrotrophic viviparity. 2-12 pups per litter. Gestation 9-12 months.
Diet
The bat ray consumes a wide variety of invertebrates including abalone, clams, gastropods, shrimps, polychaete worms, and even sea cucumbers. Plus some small bony fishes. Gorges on market squid (Doryteuthis opalescens) during the mass spawning events in California.
Behavior
Often solitary but forms large mating aggregations in shallow bays during the summer. Excavates large, deep holes in the substrate to retrieve prey.
Reaction to divers
Usually shy around scuba divers unless preoccupied with feeding.
Diving logistics
California Bat Rays are often encountered while diving in the kelp forests around Catalina Island. Dive companies in Avalon can arrange charters to the best sites but there is no guarantee that bat rays will show up.
Shore divers in Southern California regularly see bat rays along the shoreline just outside the surf. Try to get up to date advice from locals on the specifics of where and when to plan a dive. Beach divers at La Jolla Shores sometimes see bat rays in the presence of Leopard Sharks during the summer and fall.
If you manage to time your visit to coincide with the market squid run you are almost guaranteed to see bat rays and numerous other elasmobranchs. The squid run is hard to predict but usually occurs in December.
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Similar species
Longnose Eagle Ray Distinguished by much longer rostral lobe that is somewhat pointed. Sympatric in southern Baja.