An ancient Greenland shark, a monster renowned for living far away in the freezing Arctic, was one of the last things biologists anticipated to find in the warm Caribbean Sea.
However, when briefly trapping and tagging tiger sharks off the coast of Belize, researchers grabbed a Greenland shark (or possibly a Greenland-shark hybrid), a species that has lived in the deep oceans for centuries.
“We suddenly spotted a really slow-moving, lethargic creature beneath the surface of the water,” said Devanshi Kasana, a biologist and Ph.D. student at Florida International University’s Predator Ecology and Conservation lab. The discovery was recently published in the journal Marine Biology. At first, the researchers suspected it was a sixgill shark, a powerful and interesting deep-sea predator. They did, however, photograph the rarely seen animal and confirmed that it was a Greenland shark.
“It seemed like something from prehistoric times,” Kasana continued.
Greenland sharks are, in fact, members of a shark family that dates back approximately 100 million years, when dinosaurs ruled the earth. Sharks spend most of their lives in the dark, hundreds of feet underwater, where they grow, move, and age slowly. Moving slowly to conserve energy is a key adaptation in deep water, where nutrients are scarce. Greenland sharks are evidently well-adapted to these depths: they survive for at least two and a half centuries, and possibly much longer. They are the world’s longest-living vertebrates.
What does a Greenland shark have to do with the Caribbean?
The discovery of a Greenland shark near a coral reef off the coast of Belize was certainly unexpected. But that is not unthinkable.
This little-known species is believed to thrive in the deep seas surrounding the Arctic. Biologists believe they could live in other deep ocean places as well. The Caribbean is included. The biologists returned the next day to find their line had drifted a couple of miles away from the coral reef, into water 2,000 feet deep, after setting it in Belize’s protected Glover’s Reef Atoll while monitoring and researching tiger sharks.
When they retrieved their scientific capture, they noticed the odd shark. “It seemed very, very old,” said Hector Daniel Martinez, a coauthor of the report and one of the researchers who observed the shark. “It was in waist-high water.”
“It appeared to be very old.”
The slope off the neighboring reef drops to a depth of 9,500 feet. It’s a bitterly cold, dark world, perfect for a Greenland shark.
The deep waters are notoriously underexplored and poorly understood. The finding of this Arctic shark shows that just because we haven’t seen something doesn’t mean it doesn’t exist. In 2020, Alan Leonardi, head of the National Oceanic and Atmospheric Administration’s Office of Ocean Exploration and Research, told Mashable, “We know so little about the deep ocean that pretty much anyone can find something new if they were doing anything unique down there.”
It was difficult to locate a Greenland shark in Belize. Diverse scholars, local fishers, and the Belize government all worked together to create a marine protected area. It allowed scientists to witness something scientifically unprecedented. Demian Chapman, one of the study’s coauthors and director of Sharks and Rays Conservation Research at Mote Marine Laboratory and Aquarium, told Mashable, “This discovery is made feasible by scientists working together.”
“It was pretty near to coral,” Chapman observed. “You usually think of them as being near ice.”
A big concern is whether this specific Greenland shark came to the Caribbean from Arctic waters, or if it spent most of its life in (deep) tropical waters. It’s a mystery. But there’s a fair likelihood that there are more of them down there, in the murky waters where we can’t see them.
“I doubt it’s the only one,” Chapman remarked.