DEVIL RAYS
The 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.
© Houssine Kaddachi/Oceana
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?
A school of smoothtail mobulas
© Houssine Kaddachi/Oceana
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.
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.
A devil fish caught by a longline © Oceana
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.
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.
IUCN data for each Mobula species
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
Sources
Fish Base
IUCN Red List of Threatened Species
Florida Museum of Natural History
Shark Savers