Featured Elasmobranch – Bentfin Devil Ray

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Featured Elasmobranch – Bentfin Devil Ray

April 2009

bentfin_devil_ray1

Bentfin Devil Ray

Mobula thurstoni (Lloyd, 1908)

FAMILY MOBULIDAE (Manta and Devil Rays)

Identification: Like other Mobula species, the bentfin devil ray is recognized by its paired, flat head fins, large, angular pectoral disc, subterminal mouth with teeth in both jaws, and slender, “whip like” tail that has a single dorsal fin at the base and lacks a spine. In particular, the bentfin devil ray is moderate in size with short head fins, and a tail that is shorter than its disc width. Its disc has swept-back tips, which have a prominent double bend to their front. The underside of the disc is white centrally and silver on the pectoral fin tips. Above it is dark blue to black with a white tipped dorsal fin.

Size: Maximum size at least 190 cm, and possibly up to 220 cm, disc width (DW).

Distribution: A circumglobal species found in most all temperate and tropical seas. They are most common off Australia, Brazil, Chile, Costa Rica, Côte d’Ivoire, Ecuador, El Salvador, Eritrea, Guatemala, Honduras, India, Indonesia, Japan, Mexico, Nicaragua, Oman, Philippines, Senegal, South Africa, and Thailand.

Habitat: This mobulid species is found in pelagic, shallow, neritic waters from the nearshore down to about 100 m deep, in open and shallow temperate and tropical seas, often near coral reefs. They are found most commonly near the coast and usually at the surface, either singly or in small groups.

Biology: Viviparous with histotrophy (intrauterine milk) which nourishes the developing embryos. Litter size is usually one after a one to possibly three year gestation period. The neonates are born at about 65—85 cm DW. Males mature between 150—154 cm DW, but there is no information on the size at which females mature. They are filter-feeders, feeding mainly on planktonic crustaceans. Their head fins are used to direct prey into the their wide, “slot like” mouth and they have rows of fringed plates covering their internal gill slits to prevent small prey from escaping through their gill cavities.

General interest: The bentfin devil ray, known as the Mante Vampire in France, can leap several feet out of the water. They are listed by the IUCN as “Near Threatened” globally, but are considered “Vulnerable” throughout Southeast Asia. These rays are harvested and taken incidentally by gill nets, longlines, purse seines and harpoons. There is an increasing demand for their branchial filter plates, which are used in traditional Chinese medicines in Asia. Their skin, meat and cartilage are harvested for consumption. There is insufficient landings data for the bentfin devil ray due, in part, to the fact that they are often grouped with other Mobula species. They are vulnerable due to their low fecundity.

By Noëlle Yochum
Moss Landing Marine Laboratories
8272 Moss Landing Road
Moss Landing, CA 95039
nyochum@mlml.calstate.edu