Biggest Ocean Sunfish Weighing 5,000 Pounds Correctly Identified After Researchers' Mistake

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A Mola mola sunfish seen at the Monterey Bay Aquarium. This, however, is not the famed 5,000-pound fish. Fred Hsu/Wikimedia Commons

The world's largest bony fish, which weighs in at 5,070 pounds, has finally found its rightful identity after scientists reclassified the specimen, reports Live Science.

Related: Biggest Ocean Sunfish Found in New Zealand is the First Species of Its Kind Discovered in 130 Years

This beast was originally caught in 1996 off the Japanese coast, according to an article on Springer, and was identified as a Mola mola sunfish. However, researchers investigated the classification of several types of sunfish species and found that it should instead be known as a Mola alexandrini. Scientists from Hiroshima University in Japan, University of Tokyo and Murdoch University (located in Australia, Singapore and the United Emirates) collaborated to publish their findings in Ichthyological Research.

As the article in Springer explains, the team sorted through more than a thousand documents from across the globe (there were even reports up to 500 years old). Scientists studied 30 different species using samples from around the world—some had been preserved while others were fresh—as well as images and historical records. After much analyzing, they realized that the largest fish formerly known as Mola mola should now be referred to as Mola alexandrini because of several identifying features: its protruding head, chin bumps and round-shaped rudder. They even offered up a new moniker: "bump-head sunfish."

This reclassification also changes things for the listing of world's heaviest bony fish in The Guinness World Records, which currently names the Mola mola.

The fish in question was measured by a team from Kamogawa SeaWorld in Japan, reported National Geographic in 2003. It was nearly 9 feet long and topped more than 5,000 pounds.

Marine Biologist and National Geographic Explorer Tierney Thys told the publication, "It is not the longest, but it may be the heaviest sunfish that's actually been measured on a reliable scale."

Determining which bony fish is heftiest has a long, curious history, as the magazine reported. In 1908, a Mola mola was hit by an Australian steamship and then deemed heaviest sunfish in The Guinness Book of Animal Records. It weighed roughly 4,927 pounds. But some doubted whether that was accurate.

Marine biologist Julian Pepperell, who wrote a book on marine history, told National Geographic that the weight was probably nothing more than a guess.

"Sizes of large fish are often cited in various levels of literature, but on closer examination or investigation it is often very difficult to verify that a fish was actually measured or weighed," he said. "Often someone at the time will make a guess, or guesstimate, that will enter the lexicon."