Sand tiger sharks, a species whose numbers declined by over 75 percent at the end of the last century and are currently classified as vulnerable by the International Union for Conservation of Nature, are have been discovered to hang around shipwrecks in the waters off the coast of North Carolina.
Scientists from NOAA, the Coastal Studies Institute Duke University, North Carolina Aquariums and the Sand Tiger Shark Consortium are using this knowledge to gather more information on these sharks and their behavior and they're doing so with laser-outfitted robots.
The scientists are using remotely-operated underwater robots that are outfitted with multiple cameras and sensors that record data on water temperature, salinity and pick up signals from any acoustic tags. It also has lasers that shine two bright points on the shark that the researchers can use to reliably measure them, a technique that has also been used on whale sharks. The scientists launch the robot from a boat and use a joystick like controller to move it through the water.
“It gets us our eyes underwater without having to physically touch the sharks or bring them up to the surface,” said marine ecologist Avery B. Paxton, who is leading the study. “We thought that was a really big benefit to this method. It gives us a great picture of what’s going on underwater.”
Sand tiger sharks can grow up to 10 feet in length and are known for their distinct dark spot patterns, which like fingerprints, are unique to each individual shark. They're very docile so the robots are able to easily approach them and gather data.
There is not as much known about sand tiger sharks as other species and like other large sharks, it's believed their numbers are declining. The researchers are hoping to shine a light on this species and find answers to questions that remain about this species like what their numbers are now and what coastal ocean areas they are occupying.
The waters off North Carolina are littered with shipwrecks -- it's often referred to as the Graveyard of the Atlantic -- and shipwrecks attract a variety of marine life including sharks. The project that started in July is using the underwater robot to monitor sand tiger sharks at eight different World War I and World War II era shipwrecks.
Sand tigers migrate from New England in the summer to Florida in the winter and often stop in North Carolina in between, but the numbers that they have spotted at these shipwrecks seem to be out of proportion to the declining population.
“North Carolina is a huge puzzle for us,” Paxton said, adding that there are consistently high numbers of sand tiger sharks found there and that the shipwrecks could be the key. There are often 100 sharks around just one shipwreck.
One of the goals of the study is to see if the sharks are just stopping halfway through their migration or it some sand tigers are making it their year-round home. The data they gather could help them figure out how to better monitor and direct conservation efforts for all species of sharks.