Why Does This Cannibalistic Fish Keep Washing Ashore?

For hundreds of years, a strange species of fish with long fanglike teeth that eats its own kind and spends most of its time at the bottom of the ocean has somehow found its way to the shores of the West Coast.

Scientists aren’t sure why. The latest appearance by a lancetfish, as the species is known, was on a beach in Oregon, state officials said Monday, prompting more speculation about why the deep-sea creature occasionally surfaces on land.

Lancetfish are obscure in part because they have no commercial appeal — meaning that they don’t taste good. The silvery and gelatinous fish have a “scientific name translates to something like scaleless lizard or scaleless dragon,” and they look the part, said Elan Portner, a scientist at the Scripps Institution of Oceanography in San Diego, one place where lancetfish have been found washed ashore.

Lancetfish also “migrate as far north as subarctic areas like Alaska’s Bering Sea to feed,” according to the National Oceanic and Atmospheric Administration.

Dr. Portner, who has been studying lancetfish for a decade, said the fish had been washing ashore “for at least 300 years and likely longer,” and like the Oregon officials, he said that “no one knows why.”

One Twitter user said she had spotted a curious fish in Lincoln City, Ore., at the end of last month, asking for help from “#FishTwitter” and “#DeepSeaTwitter” to identify it. Several users replied to suggest that it was a lancetfish.

Growing to more than six feet long, the species is one of the biggest to roam near the ocean floor, a habitat that is difficult and costly to study. While researchers say the deep sea remains very much a mystery, they are helped by the lancetfish’s ability to swallow its prey nearly whole. “Their stomachs are basically little refrigerators that keep our samples in really good conditions until we can get them into the lab,” Dr. Portner said.

He added, “Several species have been described from individuals found in the stomachs of lancetfish — like new, deep-sea species that no one has seen before.”

Researchers also commonly find smaller lancetfish in the stomachs of the specimens that wash ashore.

“They’re quite cannibalistic,” Dr. Portner said, adding that the species is very abundant, making it more likely that they will eat other lancetfish, though he noted that scientists know very little about the species’ reproduction.

Benjamin Frable, a museum scientist and ichthyologist, or fish expert, at the Scripps Institution of Oceanography, offered some ideas for why lancetfish may wash ashore. They could have been chasing prey in shallower waters and gotten too close to shore. The fish are not very strong, he said, making it difficult for them to move away from the beach.

Oregon State Parks posted photos on social media of a lancetfish that the agency said had been found alive and which was “helped back into the ocean” and “swam off.” While noting that “no one is sure why they are washing ashore,” the park agency asked residents who find the fish to post photos and tag its account and that of NOAA Fisheries West Coast.

Social media users can help solve the mystery of beached lancetfish, Dr. Portner said.

Posting about the sightings “allows us to have more observation of onshore records,” he said, and “maybe having more data will help us start to examine why the fishes are washing up onshore.”