Manta ray  (Manta birostris)

The manta ray is classified as Near Threatened (NT) on the IUCN Red List (1).

The graceful manta ray (Manta birostris) is a stunning member of the devil ray family, if only for its sheer size. These large rays have a distinctive body shape with triangular pectoral ‘wings’ and paddle-like lobes extending in front of their mouths (2). They are generally dark on the upper surface, ranging from black to greyish-blue and brown, with pale undersides; individuals have a unique pattern of blotches and scars that can be used to identify them (2). The large, cavernous mouth is situated at the front of the body and contains 18 rows of teeth on the lower jaw (3).

Manta rays are found throughout the world’s oceans, in tropical waters between 35° North and 35° South (3). Previously, a number of different species were recognised, but the manta ray is now considered to be just one species: Manta birostris (2).

Inhabits nearshore waters, often near to coral reefs; manta rays are seen near to the surface of the water or in the middle of the water column (2).

Manta rays are generally solitary, although loose aggregations of individuals may occur where there are abundant food sources or during the breeding season. When ready to mate, a male manta ray will bite his mate’s pectoral fin to position himself belly-belly for copulation (3). The developing eggs remain inside the female’s body for possibly as long as 12 months and hatch internally so that she gives birth to live young (2). The average litter size is two pups, and there is often a two year gap between births (2).

These rays feed on planktonic organisms by filtering volumes of water through their mouths. Individuals have been observed swimming in slow vertical loops whilst feeding, possibly in an effort to concentrate prey items (2). The fleshy projections on either side of the mouth are also used to funnel prey; when not feeding, these lobes are either furled or closed in front of the mouth (2). Manta rays are often host to remoras (Remorina spp.), which attach to the underside of the larger fish and consume particles of food that fall from the mouth (2). Exceptionally graceful swimmers, manta rays appear to fly through the water on their large wings. Individuals have also been observed to jump (or ‘breach’) clear out of the water, possibly in a form of communication or play (3).

Manta rays were traditionally harvested for their oil-rich livers and for their skins, which were used as an abrasive (3); these practices centred on eastern Australia and the Gulf of California (2). The small litter size and yearly intervals between births means that populations are particularly vulnerable to exploitation and in the 1990s fisheries in the Philippines and Mexico decimated local populations (2). These ocean dwellers are also at risk from accidental catch by the fishing industry although the extent of this pressure is unknown (2).

Tourism industries have sprung up in areas regularly visited by this graceful giant, which may help to preserve numbers. These practices carry their own risks however; manta rays may be distressed by close contact and can develop lesions on their skin if touched (2). Regulation of this industry will be important in allowing people to safely observe these awe-inspiring fish in the wild.

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

For more information on the manta ray:

• Manta Pacific Research Foundation:
  www.mantapacific.org
• IUCN Shark Specialist Group:
  www.flmnh.ufl.edu/fish/Organizations/SSG/SSG.htm
• BBC Wildlife Finder:
  http://www.bbc.co.uk/nature/species/Manta_ray

For further information on the conservation of sharks and rays:

• Save Our Seas Foundation:
  http://www.saveourseas.com/