UC San Diego

Another Deep-Sea Fish, This One Cannibalistic, Washes Up on San Diego Beach

Scientists at the Scripps Institution of Oceanography are studying what Lancetfish eat to learn more about their daily lives

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San Diego has a reputation for serving great seafood, but lately we’ve been in the news because of the sea life washing up on our shores.

Last week a Pacific footballfish, an ultra-rare, deep-sea anglerfish that cameoed in "Finding Nemo," washed up on Black’s Beach. On Tuesday, beachgoers near the Scripps Institution of Oceanography (SIO) north of La Jolla Shores discovered a 4-foot live lancetfish that had beached itself.

The hermaphroditic lancetfish are nowhere near as rare as Pacific footballfish, according to researchers with Scripps, but they’re perhaps just as interesting. Here’s what we learned about the species, and some of the many mysteries Lancetfish researchers are trying to solve.

Do They Taste Good?

Sorry to disappoint, but lancetfish tacos will never be the menu item that earns your favorite nouveau chic restaurant a Michelin star. It probably couldn’t cut it as the featured ingredient in a can of Friskies.

The National Oceanic and Atmospheric Administration (NOAA) tried to work with chefs on a campaign of sorts that would boost awareness about the cuisine opportunities for lancetfish. The campaign never really got off the ground (or should we say seafloor) because our slim, shiny friends just don’t taste good to humans.

They do, however, taste good to other lancetfish.

The creature was a Pacific footballfish, a type of deep-sea anglerfish made famous in 'Finding Nemo' that has a little bioluminescent light on top of its head that acts as a lure

Are Lancetfish Really Cannibals?

It’s true, according to Dr. Elan Portner, a post-doctoral fellow at SIO’s Choy Lab. Portner and a team of scientists under UC San Diego assistant professor Dr. Anela Choy have been studying the stomach contents of lancetfish.

What they found was that lancetfish appear to enjoy the taste of their own species. It might be a maturity thing, though, similar to some humans and green vegetables. Choy’s team found lancetfish gravitate to their own once they reach about 3 feet long.

Why they wait is a mystery, as are many other aspects of the lancetfish’s life.

Hermaphroditic Fish? Explain That, Please

That’s another doozy. Lancetfish are what’s known as simultaneous hermaphrodites, meaning they possess both female and male reproductive organs that produce viable gametes at the same time. Sequential hermaphrodites undergo a “switch.”

Scientists don’t know if lancetfish can reproduce by themselves or if they rely on one or multiple partners, according to Portner. It’s also not clear if they are solitary or travel in schools, so holiday time for these cannibals is either incredibly awkward or downright lonely.

More About Lancetfish

The lancetfish that came ashore in La Jolla Wednesday is the 17th discovered by or turned into the SIO since 1947. The last was in 1996 in Oceanside, according to SIO’s Marine Vertebrate Collection manager, Ben Frable.

SIO 21-37, the catalog name for the newest addition to Frable’s collection, was found at La Jolla Shores alive. The delicate fish didn’t survive its short stay on land -- or attacks by seagulls -- but Frable says SIO 21-37 will be preserved to help researchers, possibly for hundreds of years. He said his collection’s oldest specimen is a rockfish preserved since 1881.

Frable thinks SIO 21-37 may have gotten lost chasing prey or chased off course running from a predator.

Portner didn’t have a theory for how the lancetfish ended up on the beach. Although they feed between the surface of the ocean and about 6,000 feet deep, they’re rarely spotted inside the surf break, according to Portner. Lancetfish are commonly caught by line fishermen searching for swordfish or tuna as deep as 800 -900 feet.

Researchers know very little about the species, but it’s not because they’re rare. Lancetfish are found in all of the world’s oceans and are abundant in the high seas, which Portner called the largest habitat on earth. They’re just not easily observed.

For now, the Choy Lab’s team hopes studying what the lancetfish eats will help peel back the layers of its fascinating life.

Besides juveniles of their own species, lancetfish love to eat hatchet fish, crustaceans, squid, octopus, amphipods and, sadly, plastic. Portner says around 30% of lancetfish studied tend to have some type of marine debris in their stomachs, including shards of plastic and sometimes even whole bottles.

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