Essential Manta Ray Facts

Essential Manta Ray Facts

When asking fellow divers what animals make the top five of their marine encounters bucket list, you can almost guarantee that the manta ray is on there, and with good reason.

These gentle giants are easily one of the most beautiful fish on the planet. They soar and glide through the water like birds, and they are known to interact with divers, putting on acrobatic shows that make a pod of spinner dolphins look pretty ordinary by comparison.

What is a Manta Ray?

Manta rays are the largest rays on the planet, and there are two living species that belong to the genus Manta.

The smaller species is known scientifically as Manta alfredi, or more commonly Reef Manta Ray, while the larger species, Manta birostris, is better known as the Giant Oceanic Manta Ray.

The name ‘Manta’ comes from Spanish and Portuguese, meaning mantle (blanket), which comes from both their blanket like appearance and the blanket shaped trap that has been historically used to catch them.

What is the Difference Between Reef and Oceanic Manta Rays?

Due to their similar appearances, it can be difficult to tell the difference between the two species.

The main difference is the size variation between the two, with the Oceanic Manta reaching a maximum wing span of more than seven metres -averaging at four to five metres, while the Reef Manta grows to a maximum wing span of five metres – averaging three to four metres.

While the size difference makes it easier to distinguish the two apart, it only works for fully grown adult rays, and young rays are often misidentified.

The only sure-fire to tell the difference between the two (unless you are looking at a fully grown Oceanic Manta) is by looking at their colour patterns. The reef manta has a dark dorsal side and the white head marking gradually fade into the black body, while the oceanic manta has a very dark dorsal side and there is no gradual fade between the white head markings and the dark body.

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What do Manta Rays Eat?

Both species of mantra ray are closely related to sharks, yet their feeding habits could not be more different.

Despite their enormous size, manta rays only food source comes in the form of planktonic animals that we can barely see. They find areas of strong current, and swim into it, filtering through the water as it passes by. The water will pass over their gill rakers – cartilaginous structures that protect the gills and filter plankton from the water – and they will expel all the unnecessary water, only keeping what tiny animals are left behind. Because their bodies are so big, they must consume an enormous amount of plankton to survive.

While they have been known to also eat small fish, this tends to be an unfortunate mistake of the fish being in the wrong place at the wrong time, and the manta ray simply absorbs it like it does with the smaller plankton.

Why do Manta Rays Gather?

Ocean currents tend to be predictable, and where there is more current, there is more food.

Plankton tends to gather near the surface, which means that is where the mantas will gather. They have been sighted in groups of more than 50 individuals swimming side by side into the current – allowing the food to come to them.

Just like any other fish, manta rays are susceptible to parasites, and these must be removed to maintain good health. They will frequently visit underwater cleaning stations and stay for extended periods while the cleaner fish will pick away at their parasites. These are the best times for divers to observe them, as they will stay in one area for a while, and wont move too much.

Despite the names ‘oceanic’ and reef’ both species are pelagic, and will migrate more than 1,000km to reach nutrient rich waters and better feeding grounds.

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Where can I Dive with Manta Rays?

Mantas are found throughout all the worlds tropical and subtropical oceans, however they prefer water that is around 20 degrees Celsius. The furthest north they have been found is North Carolina, USA, and the southern most they have been spotted is the North island, New Zealand. Mantas can be found anywhere within their range, however they are most likely to show up in areas of high current.

The Maldives are well known for manta sightings, as is Kona, Hawaii (see image below), however Indonesia is probably the best place in the world to encounter these gentle giants.

The rapid currents that bottleneck through Komodo National Park attracts them in large numbers, and divers can simply drop down to the shallow bottom, hook onto a rock, and watch the show. Komodo is only accessible for a few months a year, however when the conditions in Komodo turn bad, divers can head to Raja Ampat, Papua, where mantas are also known to gather (although not in the same numbers as Komodo).

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Manta Ray Threats

Both the oceanic and reef manta are currently considered vulnerable by the ‘ICUN Red List of Threatened Species’.

Due to their size, only the largest of marine predators can cause them any real problems. Tiger sharks, hammerhead sharks and orca are known to prey on mantas, and smaller sharks and other predatory fish are known to attack them. Most manta rays bear the scars of such attacks, however, very few attacks prove to be fatal.

The main threat to manta rays comes from fishing. In the past, commercial fisheries have targeted manta rays for their meat, and they were once captured in Australia and California for their liver oil and skin. While the flesh is edible, it is not said to be a particularly pleasant meat when compared with other fish. Unfortunately, their gill rakers have recently become a trend in Chinese medicine, and each year thousands of Mantas are killed throughout the Indo-Pacific purely for these gill rakers.

Since 2011, it has become strictly prohibited to fish for manta rays in international waters, however these laws are often ignored. They are frequently caught on lines accidentally as the currents that attract them to food also attract other fish, which the fishermen are following.

Although it is up to individual countries to dictate their own laws on manta ray fishing, most countries have chosen to favour bans, especially in areas where diving and eco-tourism is high. Mexico, the Maldives and the Philippines have all introduced manta fishing bans in areas of high tourism.

How to Help the Manta Population

Just like the spots on a whale shark, every manta ray has its own unique markings that separate it from the rest.

The black spots that appear on the underside of the manta are unique, and by cataloging them, we can track the movements of each manta in the database. If you have a camera, and can get a relatively clear image of the underside, then you are encouraged to upload it to www.mantamatcher.org. Using this data, scientists can track the migration paths of the mantas, and this data could prove vital to future protective measurements.

Who knows. Maybe you will find a new, unregistered manta ray, which you might get the name!

‘Essential Manta Ray Facts’ was written by Mike

Photo credit: Blue Planet Scuba, Big Island Divers, Manta ID Palau