Featured Elasmobranch-Spinetail Mobula
Category : Featured Elasmobranch
Mobula japanica (Müller and Henle 1841)
Family Mobulidae (Manta and Devil Rays)
Identification: Medium to large-sized Devil Ray with sharply pointed ‘wing-like’ pectoral fins. A short, sharp, serrated stinging spine is present behind the dorsal fin followed by a very long, wire-like tail equal to or slightly longer than the disc width. The dorsal surface is bright blue to black with crescent-shaped shoulder bars present on juveniles; ventral surface is white in juveniles, but adults have dark blotches.
Size: Maximum size of 310 cm disc width (DW), but most are less than 250 cm DW. Size at birth is about 70-92 cm DW.
Distribution: Circumglobal in temperate and tropical seas, but its distribution is not completely defined. In the eastern Pacific this mobulid species ranges from central California, especially during warm water summer months, southwards to Peru.
Habitat: Inshore coastal to offshore and possibly oceanic, usually observed near the surface. Movement patterns and migrations are not well understood, but it does exhibit seasonal abundance in some locations such as the Gulf of California.
Biology: Reproductive mode is viviparous, without a yolk sac placenta, with a single pup per litter. The southern Gulf of California is believed to be important for spring and summer mating and feeding grounds for adults. Pupping appears to take place offshore, perhaps near islands or seamounts. This species has been observed in small aggregations, but is not believed to be a schooling species. Males mature around 198-210 cm DW, and females mature around 207 cm. It is a planktivorous filter-feeder mostly on euphausiid shrimp and copepods.
General Interest: The IUCN Red List lists it as near threatened globally and vulnerable throughout Southeast Asia. It is highly susceptible to gillnet and purse seine fishery for tunas in Indonesia, Mexico and the Philippines. When caught as bycatch in fisheries its flesh is used for human consumption, bait or chum, and its gill rakers are dried and exported to Asia for medicinal use. Given its low fecundity rate it likely cannot support current exploitation even though it is not directly fished. Some management is in place, but it is poorly regulated and not necessarily mobulid or species specific. There is a need to develop and implement better management for this species in some regions.
By: Kelsey James
Pacific Shark Research Center, MLML
Conservation Ecology Lab, SDSU