As if plucked from Jurassic waters, basking sharks – the second-largest sharks in the world – languidly move through today’s oceans, their mouths agape as they sift through tons of seawater to catch prey. It's little wonder such an underwater oddity has piqued the curiosity of scientists at the Woods Hole Oceanographic Institution (WHOI).
The team’s REMUS SharkCam has captured footage of the sharks off the West Coast of Scotland for the first time. Initially developed to track white sharks, the scientists turned the autonomous underwater vehicle (AUV) on basking sharks in the hopes of learning more about these iconic creatures.
"Every time we deploy REMUS SharkCam, we learn something new about the species we are studying," said Amy Kukulya, WHOI research engineer and SharkCam principal investigator, in a statement. "We're able to remove the ocean’s opaque layer and dive into places never before possible with this ground-breaking technology answering questions about key species and revealing new ones."
The project is taking place in a proposed marine protected area (MPA) under discussion by the Scottish Government. The region has seen large numbers of basking sharks congregate, possibly even breeding in these waters, although such an event has never been seen before on film. The team hope the wide-angle, high-definition footage from the robotic vehicle will help "strengthen the case" for protection boundaries in this area of the sea.
The SharkCam, which looks like a yellow torpedo, is programmed to follow a transponder beacon on the shark's fin, following at a safe distance behind. As it does, it simultaneously collects data such as ocean temperature, salinity, and depth from the seafloor. The project is funded by the WHOI, WWF, Sky Ocean Rescue, SNH, and the University of Exeter.
Basking sharks (Cetorhinus maximus) are labeled by the IUCN Red List as vulnerable to extinction due to overfishing. Their fins are sold for shark fin soup in Asia, with a fresh pair fetching high prices at markets. The liver is also believed to be an aphrodisiac in Japan.
"These giant fish are spectacular and watching them feed gracefully at the sea surface is such a special and memorable experience," said Dr Suzanne Henderson, marine policy and advice officer at SNH. "This year’s collaboration has allowed us to use a combination of camera technologies and given us a glimpse of basking sharks’ underwater behavior – a real first and very exciting. The footage has already made us reassess their behavior, with the sharks appearing to spend much more time swimming just above the seabed than we previously thought."
The behemoth sharks can grow as long as 12 meters (40 feet) and weigh over 5 tons. They often enjoy basking in the warm waters of the surface, their large mouths open in search of food, scooping up zooplankton as sustenance for their tremendous bodies.
"This year saw the culmination of a decade of work at Exeter to support the conservation of this species," said Dr Matthew Witt of the University of Exeter. "In collaboration with SNH, we have deployed state of the art equipment over several years to learn of the behaviours of these elusive animals."
Below is a video of the white sharks captured by the REMUS SharkCam.
Disclosure: Kristy Hamilton is a WHOI Ocean Science Journalism Fellow