Blue Zoo: Manta Ray
Manta rays are perhaps the most spectacular of all the ray species. They live in warm tropical and sub-tropical waters around the world. Like all sharks and rays, a manta’s skeleton is made of cartilage (instead of bone).
Photo by Nicoboxethai, via Flickr, Creative Commons License
Although all manta rays were previously classified together, mantas are now divided into two species: reef manta rays (Manta alfredi) and giant manta rays (Manta birostris). As you can probably guess, the reef manta rays spend time in shallower water in coral reef habitats. Reef mantas are quite large, reaching 18 feet (5.5 meters) across and weighing up to 1.4 tonnes, however, giant mantas are even bigger. Giant mantas inhabit the open ocean and can reach incredible wingspans, usually around 23 feet (7 meters) but some have even been recorded at 30 feet (9.1 meters) across! It’s also believed that giant manta rays have a wider range and are more migratory than reef mantas.
Photo by NOAA's National Ocean Services, via Flickr, Creative Commons License
Despite their amazing size, they are very graceful and agile swimmers that seem to dance an underwater ballet while they feed. Their food consists of tiny particles such as plankton and they lack the stinging barb that some of their ray cousins have, rendering them harmless to humans.
Both the reef and giant manta species are filter feeders. They can often be found gathered in groups, forming magnificent feeding congregations where the plankton is plentiful. Research suggests that the mantas follow patterns in currents, weather, seasons, and the lunar cycle.
Photo by Mattk1979 via Flickr, Creative Commons License
They swim through the water with their mouths wide open to catch small particles for food. The water flows out through their gills, which have comb-like appendages that catch food. These combs are commonly referred to as “gill rakers.”
Currently, both the reef manta and giant manta are classified as “vulnerable” because they are severely overfished despite the fact that manta meat is not generally considered good to eat. Mantas are commonly hunted for their gill rakers, which are commonly used in eastern medicine. However, there’s no evidence that they have any real medical benefit – and now the trade in gill rakers is causing manta populations to decline. Mantas are sometimes also caught accidentally as bycatch in other fisheries.
Photo by SteveD., via Flickr, Creative Commons License
Because manta rays mature and reproduce slowly, it is difficult for them to recover from such exploitation, so it is important to increase conservation of the species. Currently, they are protected in Hawaii, the Maldives, and West Australia, among others. There is also an increasing market for dive tourism – although this must be managed properly to insure crowding and touching do not affect the mantas.
Witness these incredible creatures on the giant screen in our new film Journey to the South Pacific, a co-production with IMAX® Entertainment. The film will be released exclusively in select IMAX® theatres starting Nov. 27, 2013.
Photo by Michele Hall