Smoothtail devil ray  (Mobula thurstoni)

Classified as Near Threatened (NT) on the IUCN Red List (1).

Like other rays, the smoothtail devil ray has a distinctive disc-like body with large, triangular pectoral fins that function like ‘wings’, propelling it swiftly through the water column (2) (3) (4). The mouth is located on the underside of the head, while the front of the head is equipped with two distinctive paddle-shaped lobes that channel food towards the mouth. The moderately long tail is flattened towards the base, and lacks the barbed spine exhibited by some ray species. Above, this devil ray is dark blue to black, while the underside is white, becoming silvery towards the tips of the ‘wings’ (2) (5).

The smoothtail devil ray is currently known from scattered locations in the Indian, Pacific, and Atlantic Oceans, but is probably circumglobal in tropical and sub-tropical waters (1) (5).

Occurs along coastlines, to depths of less than 100 metres (1).

In common with many other mobulid species, there is a dearth of information on the natural history of the smoothtail devil ray. Based on studies in the Gulf of California, Mexico, this devil ray appears to have a highly specialised diet, with euphasiid shrimp and, to a slightly lesser extent, mysid shrimp being the main prey items. It is not known to form large schools, a behaviour exhibited by some of its close relatives, but instead is usually observed solitarily or in small groups of two to six (1) (6).

In common with many elasmobranchs, mating, birthing and juvenile life predominately take place in shallow waters. It reproduces ovoviviparously, with each female producing just a single pup per litter, which develops within an egg inside the mother's body but emerges alive after hatching. The gestation period is around 12 months (1) (6).

The smoothtail devil ray is taken as both a target species and as bycatch in fisheries in Mexico, Indonesia and the Philippines, and is almost certainly landed in other countries across its range. The greatest concern is in Southeast Asia, where catches and demand are increasing, owing in particular to a rise in the value of gill-rakers in the Asian medicinal market. Given its low reproductive potential, this species is unlikely to be able to tolerate the current levels of exploitation (1).

It is crucial that additional research is carried out to establish the true impact of target and non-target fisheries on the smoothtail devil ray. Unfortunately, elasmobranch fisheries are generally unmanaged in most regions within this species range. Furthermore, in some areas fishing regulations are poorly enforced, such as in the Philippines where mobulids are still being caught illegally despite a ban put in place in 1998. In the long run, the development and implementation of international management plans may be vital for the survival of the smoothtail devil ray and other mobulids (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about the conservation of rays and sharks, see:

• Save Our Seas Foundation:
  www.saveourseas.com
• IUCN Shark Specialist Group:
  www.iucnssg.org
• Shark Research Institute:
  www.sharks.org
• Shark Trust:
  www.sharktrust.org