A Greenland shark, one of Earth’s longest-living animals, was captured near Belize: NPR

Researchers tagging tiger sharks off the southern coast of Belize couldn’t believe their eyes when they recently brought in a different species of fish. It turned out to be a Greenland shark, which is typically found in the Arctic and can live for more than 500 years.

The team of scientists thought the shark was dead when they finally pulled it to the surface. Unlike the tiger sharks they were looking for, this shark had black, worn skin and pale blue eyes. Devanshi Kasana, a Ph.D. candidate at the Florida International University Predator Ecology and Conservation lab, said the shark looked “very, very old.”

“It was just really surprising and confusing,” she said. “As soon as it entered our field of view, we saw a black figure that got bigger and bigger. When it came to the surface, none of the crew members with all their combined fishing experience had seen anything like it.”

Kasana and colleagues published an article about the catch in the magazine marine biology in July.

Kasana said the discovery is especially exciting because it suggests that these sharks, which were thought to be primarily found in the Arctic, may also be found in the tropics.

Greenland sharks can probably live more than 500 years

Scientists have more questions than answers when it comes to the Greenland shark. According to the National Oceanic and Atmospheric Administration, these sharks are the world’s longest-living vertebrates, possibly more than 500 years old. And that’s just an estimate, because there’s no definitive way to determine their age.

The reason they get so old may have something to do with their speed of life, which is slow — very, very slow. Greenland sharks grow about a third of an inch per year and can reach over 20 feet in length. And researchers believe that the sharks don’t become sexually mature until after the first 100 years of life.

According to Kasana, some scientists have theorized that the Greenland shark can be found all over the world, as long as you know where to look. They like cold water, which is why they can be found in the Arctic. However, they have also been discovered as far south as off the coast of Georgia, thousands of feet below the ocean surface.

The theory is that the closer the sharks are to the equator, the deeper researchers have to go to find them. And they go deep, more than 7,000 feet down, according to NOAA.

The catch was unexpected

Kasana said their catch was strictly accidental. On April 22, she and her team worked with members of the Belizean shark fishing community and the Belize Fisheries Department to set out lines along Glovers Reef, about 30 miles (48 kilometers) offshore. The reef’s waters can be as shallow as 25 feet, but steep drop-offs can reach more than 2,000 feet.

“It slopes suddenly and the depth goes very deep very quickly,” Kasana said. “We think the line was dragged from a much shallower depth to the drop-off, which is why we finally caught this individual.”

A report of the encounter published on July 15 claims it was the first Greenland shark discovered in the western Caribbean. Knowing how rare the experience was, Kasana said her team discussed buying a lottery ticket if they ever came across one again.

“If we caught one more person, it would be pure luck. We don’t set our lines in a way that targets Greenland sharks,” Kasana said.

When they brought in the shark, it looked extremely old, she explained. And while they briefly considered tagging it, they didn’t want to incidentally hurt or kill the shark in the name of science. Instead, Kasana and her team measured the shark, took notes, took a photo, and sent it in.