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Episode 43: Angels of the Deep, The Manta Ray

There are two species of Manta Ray. The Giant Manta Ray (Manta birostris) is the larger of the two. The Reef Manta Ray (Manta alfredi) is the other.  The large ocean-going creatures are found all around the world in temperate oceans. They have been seen as far north as parts of Japan in the Pacific and New Jersey off the coast of the United States. They have been found as far south as northern New Zealand and off the coasts off Ecuador.

Manta Ray Description

The rays are of the class Myliobatiformes which have 223 species, 50 of which are threatened with extinction. These fish also belong to the subclass Elasmobranchii, which consists of sharks, rays, skates, and sawfish. These animals are cartilaginous fish, have no swim bladders, a ridged dorsal fin, and small placoid scales (rough against the grain).

The first cartilaginous fish is thought to have existed almost 395 million years ago during the Devonian Period. The first rays are estimated to have existed over 170 million years ago during the Jurassic Period. The Manta Ray evolved over 5 million years ago.

Both species of Manta Rays are found throughout the world in warmer, temperate oceans in water as cold as 19 °C (66 °F) and as warm as 30 °C (86 °F). The Giant Manta Ray is migratory and has been documented traveling from the Yucatan Peninsula out into the Gulf of Mexico, and from Mozambique to South Africa. Generally, these populations are fragmented and do not travel in between oceans.

Manta Ray Facts

The Giant Manta Ray can be as wide along their pectoral fins as much as 29 feet (9 meters). The Reef Manta Ray is smaller at 18 feet (5.5 meters) across. The most unique anatomic feature is the cephalic lobes which help propel water into their mouths.

These fish feed on zooplankton and other small fish. They have been documented to go as deep as 600 feet (170 meters) and are thought to be able to dive as deep as 1000 meters (3300 feet). In one study from Australia, 70% of stomach contents of Manta Rays came from organisms that live in the Mesopelagic zone (between 200 and 1000 meters).

Manta Rays are incredibly intelligent. Their brains are large for their size and have even been observed to have higher order intelligence such as self-recognition. One interesting aspect is their feeding behavior of swimming in a circle socializing and feeding. Here is a video of this behavior by National Geographic:

Manta Ray ‘Brunch’: Like Us, They’re Social Eaters

 Manta Ray Conservation

Both species of Manta Rays are classified as vulnerable to extinction. In the Indio-Pacific populations have decreased by as much as 95%. The major source of their decline is accidental catching in fishing by-catch (entanglement of gill nets) to overfishing. Manta Rays are now being sold in Asia for ‘Chinese Herbal Medicine’ to cure multiple ailments to include cancer.

To help our oceans it is recommended to use ‘coral’ friendly sunscreen. Hawaii recently passed a law banning sunscreens with oxybenzone and octinoxate, which is believed to contribute to coral bleaching.

List of coral friendly sunscreen

Organizations to Support

Manta Trust

Project Manta


Cover image by Henrik Winther Andersen (CC 2.0)

July 10, 2018
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