Whether it be hiding underneath a piece of coral, swimming off the edge of the reef, or simply watching one feed during a night dive; stingrays are some of the more fascinating marine animals found in the waters surrounding Koh Tao.
A Cousin Of The Shark
As part of the Elasmobranches family, stingrays are closely related to sharks. Stingrays are a cartilaginous fish that live most of their lives in the lower portion of the water column, on or near the bottom. The reason they are called stingrays is due to the fact that most possess one to two spines on their tails, which have venom in them.
They do not use these spines to hunt for food, but as a last defense against predators.
Stingrays have evolved flattened bodies that allow them to camouflage themselves in their environment. With eyes on the top of their pelvic disk, most stingrays will bury themselves into sand or silt not to ambush prey, but to hide from predators.
The mouth of the stingray is located on the bottom of its body, so it is difficult for it to capture prey through sight. Like sharks though, they use their sense of smell and receptors on their body that allow them to sense electric fields in the water to help them locate their prey.
What To Eat?
So what does a stingray eat? Since most stingrays spend most of their time on the bottom, their diet consists mainly of small mollusks (snails and clams) as well as small crustaceans (shrimp and crabs). Some species of stingrays feed on small fish as well. Some have specialized teeth for crushing the hard shells of their prey, while some have adapted a different approach of sucking mouthparts which act like a vacuum cleaner helping them feed on these small invertebrates.
All Around The World
Ranging from salt to fresh water, stingrays can be found in coastal tropical and subtropical waters all around the globe. Some species like eagle rays live a pelagic lifestyle, up in the water column, while some stingrays have been found to live in the deep ocean. Most live in shallow coastal waters. Around the dive sites of Koh Tao we have four species of stingrays, which are more common, then others.
Blue Spotted Ribbontail Ray
The blue spotted ribbontail ray is the most common and smallest of the 4 stingrays found around Koh Tao. Blue spotted ribbontail rays, can be identified by their oval shaped pectoral disc, and a short, thick tail. They are a yellowish brown or green color with bright, electric blue spots all over their pectoral disc. Another distinctive characteristic is that they have two blue lines running along each side of their tail.
The blue spotted ribbontails are bottom dwelling rays and are found most often in coral reefs or the sand flats surrounding the reef. They can be found fairly frequently at dive sites such as White Rock and Twins, hiding under ledges during the day, and out in the sand flats feeding during the night.
The Kuhl’s ray is commonly confused with the blue spotted ribbontail ray as they both have blue spots present on their pectoral discs. The way to distinguish the two from each other is primarily the body shape. Kuhl’s rays have a shorter snout with a much more angular body then the ribbontail ray. The color of the blue spotted ribbontail ray is also a lot more vivid then the Kuhl’s ray.
Growing larger then the blue spotted ribbontail ray, Kuhl’s rays are usually found deeper then ribbontail rays, mainly in the sand and mudflats surrounding rocky coral reefs. They can be found in the sand off Junkyard, as well as Aow Leuk and Aow Mao.
Another species of ray which is fairly easy to distinguish from the previous two species is the Jenkins Whipray, simply because it does not have any blue spots on its disc. It is a much larger species of ray, known for its diamond shaped disc and whip like tail. It also has a row of large spear like thorns along the midline of its body, which in some markets around the world is one of the reasons this species of stingray is fished.
It has a yellowish brown body, which transitions to gray on the tail past its stinging spine. These large stingrays prefer deeper water with sandy or silty bottoms. They can frequently be found under the catamaran in Tanote Bay or under the sides of HTMS Sattakut, Koh Tao’s wreck dive site.
Spotted Eagle Ray
The last and most rare species of stingrays found in Koh Tao are spotted eagle rays. They are the largest of the rays that can be found and have a distinct rhomboidal body shape that is a deep blue or black color with white spots. They have distinctive snouts that are flattened and shaped like a duckbill. The snouts are used to dig into the sand for their prey.
They are illusive creatures; unlike the other three bottom dwelling species. Spotted eagle rays spend most of their time swimming in the water column, flapping their discs in a wing like motion, hence their name. Swimming near reefs or bays, they are very rare, so if you do get the chance to see one of these magnificent rays in the water, consider yourself lucky.
What do all these species of stingrays have in common, besides all being stingrays? They are all threatened due to overfishing. Some are eaten, some are only fished for their skins, but unfortunately most are just caught as by catch.
Overfishing and the loss of habitat are a threat to these wonderful creatures, and we can help protect them. Cleaning up dive sites, taking care of our reefs and educating others are just small steps in the overall protection of these beautiful creatures.
Author: Will Nittler (PADI DM #372286)