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4,400-pound sunfish caught off North Africa literally tips the scales

a giant sunfish being hoisted over the deck of a boat with a crane
The massive ocean sunfish weighed more than 4,400 pounds, scientists estimate. (Image credit: Reuters / Seville University)

Fishers recently hauled up a surprising catch off the coast of North Africa: a colossal ocean sunfish weighing an incredible 4,400 pounds (2,000 kilograms).

At least that's how heavy marine biologists estimated the mammoth fish to be, based on its girth and the dimensions of sunfish that had previously been captured and weighed. "We tried to put it on the 1,000-kilogram (2,200 pounds) scale, but it was too heavy," marine biologist Enrique Ostale told Reuters. "It would've broken it." 

Fishers in Ceuta, a Spanish territory bordering Morocco, discovered the animal tangled in their nets in early October. They immediately called in Ostale, head of Seville University's Marine Biology Lab in Ceuta, to examine the massive sunfish. After first isolating the creature in an underwater pen attached to the boat, the team briefly hauled the fish into the air, using a crane. 

Related: In photos: The world's largest bony fish

Like other ocean sunfish, all of which belong to the genus Mola, the creature resembled an oblong pancake with huge, googly eyes stuck to its sides. Two massive, winglike fins extended from the top and bottom of the fish; in the ocean, sunfish wave these fins to and fro to propel their hefty bodies through the water.

Once the sunfish had been hoisted on deck, the team measured the animal and determined it to be 10.5 feet (3.2 meters) long and 9.5 feet (2.9 m) wide; for scale, a king-size bed is only 6.6 feet (2.03 m) long by 6.3 feet (1.9 m) wide. After measuring the sunfish and taking photos and DNA samples, the crew released the animal back into the sea, where it soon disappeared into the watery depths. 

"When we arrived there, the feeling was astonishment," Ostale said in a video interview with Reuters. "We couldn't believe our luck because we'd read books and articles about the dimensions that a sunfish can have, but we didn't know we'd [ever] be able to watch it and touch it ourselves."

Based on grooves marking the fish's sides and its stumpy clavus — a rudder-like structure on the back of the fish — Ostale and his colleagues identified the animal as a species called Mola alexandrini, also known as a bump-head sunfish because of the distinctive lump on its noggin. 

Although adult sunfish rank as the largest bony fish on the planet, scientists recently found M. alexandrini babies that measured just a few millimeters in length, Live Science previously reported. The tiny larvae look nothing like their adult counterparts, but over time, they grow to be 600 times their original size and morph into that familiar winged-pancake shape. 

The M. alexandrini captured in Ceuta set a record as the largest sunfish ever caught in the region, in terms of its dimensions, Reuters reported. But in general, the sunfish species can grow even larger and heavier. To date, the heaviest M. alexandrini specimen weighed a whopping 5,070 pounds (2,300 kg), making it the heftiest sunfish specimen ever weighed, Live Science previously reported.

Originally published on Live Science.

Nicoletta Lanese

Nicoletta Lanese is a staff writer for Live Science covering health and medicine, along with an assortment of biology, animal, environment and climate stories. She holds degrees in neuroscience and dance from the University of Florida and a graduate certificate in science communication from the University of California, Santa Cruz. Her work has appeared in The Scientist Magazine, Science News, The San Jose Mercury News and Mongabay, among other outlets.