Shark experts are puzzled by the discovery that swarms of basking sharks apparently hang out along the coast of the northeastern United States. For a study released March 29, NOAA Northeast Fisheries Science Center looked at decades of aerial photographs originally meant to track endangered whales, but instead discovered a wealth of information on the basking shark.
They used that data in conjunction with observations from earth-orbiting satellites and oceanographic databases. In total, researchers found 10 large groups of basking sharks between 1980 and 2013 spanning the distance from Nova Scotia, Canada, to Long Island, New York.
The species is normally solitary, so scientists are scrambling for explanations for the swarms along the US Atlantic coast. In total, researchers uncovered about 10,000 documented sightings, in which 99 percent of the shark groups were made up of seven or fewer sharks.
Some shark groups were much bigger though, like the group of 1,398 hanging out within just an 11.5 mile radius off of southern New England, in November 2013.
"That data was hiding away," says Leah Crowe, who led the study.
Basking sharks are the second biggest fish in the world, next to whale sharks. The basking shark is a slow-moving filter feeder, meaning they eat plankton from the ocean's surface. Crowe thinks that's what they were doing in 2013, as opposed to mating, because of the presence of several young sharks. However, these sharks spend about 90 percent of their time deep underwater, making sightings of the beasts goldmines of information for researchers.
The study suggests that when the sharks gather, it reduces the drag from their gaping mouths during feeding. That way they can draft off one another to conserve energy.
The US government categorized basking sharks as a "species of concern" in 2010 after a decrease in the species' population due to hunting.