DEVIL RAYSThe Devil Ray

Devil ray is the common name for nine species of rays that are part of the genus Mobula. Devil rays, also known as mobula rays, are fish and are closely related to sharks, skates, and other rays which are collectively known as elasmobranchs because they have skeletons made of cartilage instead of bone

Mobula rays can range in size from 17 feet from wingtip to wingtip, like the devil fish, to less than four feet wide, like the pygmy devil ray. Their mouths are located underneath their heads, and they use “cephalic fins” on either side of the head to help funnel in food and water. These fins gave rise to their common name because of the resemblance to devil horns. Although related to sting rays, only the Spinetail Mobula has a stinger.

Colors can vary from black to brown depending on the species, but all devil rays are dark on the top of their bodies and light below. Like sharks, mobula ray skin is covered by dermal denticals which gives it a rough feel similar to sandpaper.

Biology

Where are devil rays found?

The different species of devil rays are found in temperate and tropical waters throughout the world, in both coastal and oceanic environments. Mobula rays live in the open ocean, swimming continuously through the water column instead of resting on the sea floor like other rays. Sometimes, these rays will even jump into the air and soar for a few yards, likely to escape predators or remove parasites. Although mostly solitary, some species have been known to form schools.

What do devil rays eat?

Like whale sharks, these rays are filter feeders that primarily eat microscopic plankton and krill, with the occasional small fish. As devil rays swim, they take in water with the help of their cephalic fins. The water passes through the comb-like gill rakers (tiny projections on the gills), which filter out food while the water exits through the gills.

How long do devil rays live?

Little is known about the life span of devil rays or at what age they can reproduce. Devil rays give birth to live pups that develop from an egg inside the mother. Only one pup is born per litter, and gestation periods may be over a year long.

Threats

Fishing is the main threat to devil rays around the world. Fisheries exist in several countries, mainly located in the Indian and Pacific Oceans. Devil rays are targeted by fishers because their parts are highly valued in international trade. Their cartilage is used as filler in shark fin soup, and some Chinese believe that devil ray gill rakers are believed to treat a variety of ailments including cancer.

A school of smoothtail mobulas© Houssine Kaddachi/Oceana

© Houssine Kaddachi/Oceana

IUCN data for each Mobula species

A devil fish caught by a longline © Oceana

Because of their value, an estimated 94,000 mobula rays are caught each year, with Sri Lanka and India combined landing more than 79,000 individual rays. These numbers are a conservative estimate because catch levels are often underreported and there is a lack of fishing regulations.

Devil rays are also incidentally caught in fisheries targeting other species. Gillnets, purse seines, longlines, and trawls can all catch mobula rays unintentionally. The low reproductive rate and schooling behavior of devil rays makes them especially vulnerable to overfishing. Other threats to devil rays include boat strikes, habitat loss, climate change, and pollution.

Conservation

The International Union for Conservation of Nature (IUCN) lists devil ray species as endangered, vulnerable, near threatened, or data deficient. Current populations are unknown for all species, and population trends are known for only two mobula rays.

In Europe, the Bern Convention and the Barcelona Convention have listed the Devil Fish as a species requiring protection, yet only a few countries including Croatia and Malta have taken steps to protect this species. Other countries around the world including Ecuador, Honduras, Indonesia, Mexico, and New Zealand have enacted policies to help protect devil rays, but they are not always enforced. No devil ray species are protected by the Convention on International Trade in Endangered Species (CITES) or the U.S. Endangered Species Act.

Species Known Range Extinction Risk Population Size Population Trend

M. eregoodootenkee Indo-West Pacific Near Threatened Unknown Unknown

M. hypostoma Western Atlantic Data Deficient Unknown Unknown

M. japanica Probably circumglobal Near Threatened Unknown Unknown

M. kuhlii Indo-West Pacific Data Deficient Unknown Decreasing

M. mobular Mediterranean Sea Endangered Unknown Decreasing

M. munkiana Eastern Pacific Near Threatened Unknown Unknown

M. rochebrunei Southern Atlantic Vulnerable Unknown Unknown

M. tarapacana Probably circumglobal Data Deficient Unknown Unknown

M. thurstoni Probably circumglobal Near Threatened Unknown Unknown

The following table shows the conservation status of all nine species, as well as the unknowns that need to be addressed to protect these rays.

Sources

Fish Base

Florida Museum of Natural History

IUCN Red List of Threatened Species

Shark Savers