Aug 19, 2021 I Paul Seaburn

Rare Shapeshifting Werewolf Fish Seen Off the Coast of California

If you’re a fisherperson, the worst thing that can happen on a fishing trip is not catching anything. If you’re not a fisherperson, the worst thing that can happen when someone takes you fishing is catching a scary-looking fish, like a shark or a muskellunge. If you’re either one fishing off the coast of California, here’s a new fish to add to your ‘worst’ list – marine biologists just spotted an extremely rare shapeshifting werewolf fish near Monterey Bay. A what?

“A whalefish was spotted last week with ROV Doc Ricketts! This whalefish (order Cetomimiformes) was encountered by @beroe's team on their R/V Western Flyer expedition 2,013 meters deep offshore of Monterey Bay.”


“We've only encountered this obscure group of fishes 18 times in 34 years of deep-sea exploration with our ROVs.”

The Monterey Bay Aquarium Research Institute posted that exciting (for them) news on Twitter announcing the rare sighting of a whalefishes – a small, deep-sea member of the ray-finned fish family, which includes the more well-known tuna, swordfish, salmon, cod, lanternfish, fangtooth, anglerfish and others. (Full tweet and photos here.) The fangtooth and anglerfish are pretty scary-looking, but at least they stay in one shape. Not so with the aptly nicknamed ‘werewolf’ fish.

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How do they howl underwater?

According to Live Science, whalefish have only been known since 1895 when they were discovered by two Smithsonian Institution scientists. Besides being rare, they’re hard to identify because they change shapes completely three times in their life cycle, causing each to e mistakenly identified as entirely different species. Larvae are called tapetails because of their long, streamer-like tails. When they reach adulthood, males get an entirely different look that scientist aptly call “bignoses” – noses balloon, jawbones shrink and their intestines, esophagus and stomachs all shrivel and disappear, to be replaced by their sexual organs and a gigantic liver. This shapeshifting turns the males into ugly sex machines. (Ladies, please keep your comments about all males to yourselves.)

Females gratefully shift into something completely different – they look like miniature baleen whales and are far larger than the males. As can be seen in the photos and videos posted by Monterey Bay Aquarium Research Institute, the females get a brilliant orange color (see it here) which, at the depths they normally live at, makes them completely invisible. That depth ranges from 4,920 to 6,560 feet (1.5 to 2 km), and sometimes as deep as 11,500 feet (3.5 km) or more.

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A female whalefish

This shapeshifting makes the whalefish (Cetomimiformes) unique among vertebrates, although they’re so rare that other rare deep sea species could be discovered … although researchers would have the same challenge of determining if they’re one species or many.

If you’re out fishing off the coast of Monterey Bay, catching a shapeshifting whalefish might be scary because of their looks but not their size – males are just 3.5 cm (1.3 inches) while females average 35 cm (13.7 inches). They don’t bite, although those horny sperm-delivering males may try to mate with anything about a foot long, so keep them away from other fish … or your feet.

Paul Seaburn

Paul Seaburn is the editor at Mysterious Universe and its most prolific writer. He’s written for TV shows such as "The Tonight Show", "Politically Incorrect" and an award-winning children’s program. He's been published in “The New York Times" and "Huffington Post” and has co-authored numerous collections of trivia, puzzles and humor. His “What in the World!” podcast is a fun look at the latest weird and paranormal news, strange sports stories and odd trivia. Paul likes to add a bit of humor to each MU post he crafts. After all, the mysterious doesn't always have to be serious.

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