Sicklefin devil ray

How do you identify a sicklefin devil ray?

The mobula ray of the Azores is Mobula tarapacana, the sicklefin devil ray, also called the Chilean devil ray. The disc measures 2 to 2.50 meters across in adult males and 2.70 to 2.80 meters in females, up to 3.70 meters for the largest, and the weight reaches 350 kilos. The back is olive green to brown, the belly white to pale gray. The wingtips curve sharply backward, like a sickle, and the dorsal fin is plain, with no white tip. The tail is short and stiff, shorter than the width of the disc. Two rolled cephalic fins frame a terminal mouth. You tell it from the much larger oceanic manta ray by its size and its scythe-shaped wings, and from Mobula mobular by the lack of a dark band on the head and of a long tail with a spine.

How does the sicklefin devil ray live?

It is an offshore ray, pelagic and sometimes coastal, found in the tropical, subtropical and temperate waters of all three oceans. It filters plankton, small crustaceans and small fish through its gill plates. It is one of the deepest divers in the ocean. Tags have recorded descents to 1,896 meters, in successive steps of one to one and a half hours, and dives to 1,000 meters lasting eleven hours. A network of blood vessels, the retia mirabilia, warms its brain in cold water, and it spends at least an hour near the surface before and after each descent. Reproduction is slow: a single pup per litter, born with a disc of 1.05 to 1.40 meters, and a generation length of nearly thirteen years.

Where and when can you see sicklefin devil rays in the Azores?

Solitary the rest of the year, it gathers in summer on the seamounts of the archipelago to feed, get cleaned and court: at Princess Alice Bank, 45 nautical miles from Faial, and at Ambrósio, north of Santa Maria, from late June to mid-October, with a peak in August and September. Groups range from three to fifty rays and more. At Ambrósio, twelve to seventeen rays are the norm and forty to fifty regularly show up, spiraling up along the buoy line every fifteen to twenty minutes. It also passes over the Dollabarat and the shoals of the Faial-Pico channel. You can see it diving or snorkeling, since it comes right up to the surface.

Is the sicklefin devil ray endangered?

Fished for its gill plates, sold in Asia for traditional medicine, and caught in nets and on longlines, Mobula tarapacana has lost 50 to 79% of its numbers over three generations. The IUCN now lists it as Critically Endangered, after listing it as Endangered in 2019. It has been on CITES Appendix II since 2016 and on the Convention on Migratory Species since 2014. In the Azores, the Manta Catalog Azores project identifies each ray by the spots on its belly, from divers' photos, to understand where, when and why the rays gather on the seamounts.