You Can Call Me Ray

If a large creature is gliding toward you on a dive that kind of resembles a space ship, you are likely having an encounter with one of the most interesting fish you’ll see in Maui waters- a ray! There are three groups of rays in Hawaii- stingrays, spotted eagle rays, and the most common, manta rays. A distant relative to a shark, instead of bones, their vertebra is made of cartilage. They also must constantly swim in a forward motion to pass oxygenated water through their gills.

Rays have also been around for a very long time. Modern day sharks and rays arose during the Jurassic Period, about 200 million to 145.5 million years ago. Here are a few other interesting facts about Hawaii’s rays, and how to distinguish which type you are seeing.

Manta Rays

According to Dr. Robert Rubin from the Pacific Manta Research Group, Manta rays are one of the few species of animals worldwide that seem to have a genuine interest and curiosity about humans. “The Pacific Manta Ray represents this unique combination of great size coupled with a gentle grace and a curious approach to the humans who come to share, if only for a moment its silent world,” said Rubin.

Manta rays can often be seen in near shore waters as well as deeper dive spots. They belong to the Mobula alfredi species and are a circumtropical pelagic fish (distributed around the world in tropical oceans) They are the largest of the Batoids (rays) with a maximum wingtip to wingtip span of 22 feet. The mantas you’ll likely see while diving are around 8 feef long, but can also be spotted up to 14 feet across their body, or disc, width. Females are typically larger than males and are thought to give birth to a single pup at two to three year intervals. The gestation period is known to be one year in length.

Specific manta rays can be identified by researchers who note shape and patterns of spots on their bellies. Mantas can be distinguished from other ray species by their dark blackish top side. Manta rays also have the largest brains among the 32,000 species of fish. The “stinger” on the tail of a manta ray has evolved to not be poisonous.

Manta rays are considered threatened worldwide. As of 2019, it is illegal to capture or kill a Manta ray in Hawaiian waters, with fines up to $10,000.

Spotted Eagle Rays

If you spot a ray breach out of the water, it is likely a spotted eagle ray. Researchers are not sure why this species of ray does this, but there is some evidence some of this activity may be related to birthing. There is a move to distinguish Pacific Ocean species as white spotted eagle rays. Howerever, Hawaiian spotted eagle rays (Aetobatus narinari) have dots ranging from white to yellow and green forming a beautiful pattern within it’s black topside. Like other ray species, the spotted eagle ray also has a white underbelly. Their maximum width is 6 feet from tip to tip. Spotted eagle rays usually grow to about 4-7 feet in length (excluding tail), and their long, slender tail can equal up to four times the length of its body with 2-5 venomous spines at the base.

The spotted eagle ray is usually spotted among rocky and muddy coral reefs or in waters between 6-80 feet in depth. Using their shovel-shaped snout, rays dig out snails, shrimp, crabs, and sea urchins from crevices. Their flat, hard teeth plates crush the shells of their prey, swallow the meat and spit out the shells.

Spotted eagle rays can sometimes be spotted “flying” in small groups, an amazing sight of underwater ballet not to be missed, where rays in groups of 6 or more travel in the same direction at the same speed. Occasionally, one ray will break away and do a series of dives and pelvic thrusts. A spotted eagle ray may leap out of the water along one path, or vertically at a 45 degree angle, cartwheeling across the surface. Some research indicates these rays may be more active during high tides.

Spotted eagle rays are considered potentially dangerous to humans due to the venomous tail spines that can inflict serious wounds, but are also generally wary of approaching divers. Observe from a safe distance.

Stingrays  

Claire Fackler, NOAA National Marine Sanctuaries

Though sightings are rare, two species of stingrays can be found in sandy areas along Hawaii’s coastlines, including Maalaea Bay, Maui. The most common is the broad stingray (Dasyatis lata) also known as the Hawaiian stingray. This species is only found in Hawaii (with unsubstantiated sightings in Taiwan). This ray is drab olive to brown in color on its topside and white underneath. You’ll see them about three feet wide, but can reach a disc width of 5 feet, with a diamond-shaped pectoral fin disc. Their rounded snout protrudes past the disc, and their slim tail extends twice the length of their body.

Calcareous, sharp spines called tubercles cover the wide portion of the tail and one to three venomous spines are located near the top. The spines normally lay flat, but when threatened, the spines are raised at an angle and the flexible tail can be bent toward the head, impaling anything above the animal. The barbs have serrations along both sides and a venom gland at the base which is equipped with a powerful neurotoxin. The spine is made of modified dermal denticles, the same substance a shark’s rough skin is made out of. Once broken off, the spines are believed to grow back in 6-9 months on average.

Stingrays are typically non-aggressive and inactive during the day, hanging out in muddy or sandy shallows with little more than their eyes exposed. At night they will forage along the bottom for crustaceans, worms, and small bony fishes.

Although the venom embedded in the tail spines of stingrays can kill small creatures and cause acute pain to humans, it is extremely rare for the shy fish to kill humans. However, divers should use extreme caution and give stingrays a wide berth.

Cover image: Jules Cricchio, Lahaina Divers