This 6,000-Pound Sunfish Is the Largest Bony Fish on Record

Last December, scientists in Portugal got word that fishermen and boaters had spotted an enormous dead sunfish floating in the central North Atlantic. Researchers initially had doubts about the fish’s reported size, but when they finally reached the carcass near Faial Island in the Azores archipelago, they almost couldn’t believe their eyes.

Now, after weighing, measuring and analyzing the bump-head sunfish (Mola alexandrini), scientists believe it’s the heaviest bony fish ever discovered. Weighing in at roughly 6,050 pounds—the size of a large SUV—the fish was 882 pounds heavier than the reigning bony fish world record-holder, a 5,070-pound sunfish discovered off the coast of Japan in 1996.

Scientists shared more details about the giant sunfish found in the Azores last year in a new paper published last week in the Journal of Fish Biology.

Bony fish is an umbrella term used to describe the 29,000 species of aquatic wildlife with skeletons made at least partially from bone, rather than cartilage. These diverse swimmers range from teeny-tiny pygmy goby to sunfish and every size in between. More than 90 percent of all fish are bony fish; the category excludes rays, sharks and other marine wildlife with cartilaginous skeletons.

Sunfish have huge, hulking round bodies, dorsal and anal fins, and a unique rounded rudder called a clavus formed when their back fin naturally folds into itself, per National Geographic. Droves of parasites feed on their rough, gray skin. Sunfish are awkward swimmers, and they can’t fully close their mouths, which are tiny compared to their massive bodies. Sunfish prefer to munch on jellyfish, but they also eat algae, zooplankton and small fish.

When massive sunfish swim or float near the ocean’s surface, people often mistake them for sharks. But though they can be quite curious, sunfish are largely harmless.

Scientists first recognized bump-head sunfish as a distinct species in 2018. They are related to ocean sunfish (Mola mola) but can be twice as heavy.

Scientists in the Azores pulled the massive sunfish to shore, then raised it off the ground using a forklift. Once they had the fish airborne, they were able to weigh it using a special scale that typically weighs cargo loads, suspended by a crane. They also measured the carcass and collected samples for DNA testing.

Though scientists weren’t able to determine whether the humongous creature was male or female, they calculated that it stretched 10.67 feet long, 11.78 feet tall and 2.82 feet at the widest point in the middle of its body. Researchers suspect the fish was at least 20 years old, but they were not able to pinpoint its exact age.

“It must have been a king of open ocean,” says study lead author José Nuno Gomes-Pereira, a researcher with the Atlantic Naturalist Association, to CNN’s Hafsa Khalil.

(UK subtitles) The heaviest fish in the world a giant sunfish of 2744 kg from the Azores

Watch on

After finishing the examination, the scientists buried the fish in the Natural Park of Faial Island. While it’s not clear why the animal died, scientists discovered a wound containing red paint typically used on boats. It’s possible a collision with a vessel may have contributed to the sunfish’s death, but the strike may have occurred after it had already died.

The gargantuan fish is proof that the world’s oceans are still robust enough to support such a behemoth. But with climate change and other human activities, that may not always be the case.

“It’s pretty rare to find big fish these days due to overfishing and habitat degradation,” says Kory Evans, a fish ecologist at Rice University who was not involved in the study, to the New York Times’ Annie Roth.

Sarah Kuta | READ MORE

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.