American River Diver Spots Parasitic 'Vampire Fish' That Feed Off Sharks

A veteran diver in California has spotted a strange "vampire fish," or lamprey, in a Sacramento river.

On Tuesday, diver Karl Bly spotted two pacific lampreys in the American River, which runs for 30 miles from the Sierra Nevada mountains to where it meets Sacramento River. He wrote on Facebook that this is the second lamprey he has seen in 30 years.

"It looks like some sea creature from the deep," Bly said.

These jawless, parasitic eel-like fish are characterized by their large sucking disk mouth, which features sharp teeth on a tongue that resembles a file. To feed, they attach their disk to other fish, and grate their scales and skin in order to devour their body fluids. Like leeches, they release an enzyme that stops their victim's blood from clotting. This way of feeding often means the fish they feed on will die due to blood loss or because of infection.

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A stock image shows a sea lamprey with its mouth against a tank. A diver found this type of fish in the American River. Getty Images

Peter Tira of the California Department of Fish and Wildlife told CBS Local: "In the ocean, they will attach themselves to a dolphin or shark or whale and suck on that larger host fish to feed off the nutrients." They are not harmful to humans, he said.

Unlike their mouths, their bodies are smooth, and unlike some other fish, they have no scales, and their a skeleton is made of cartilage. Lampreys are born in freshwater, and migrate up rivers from the sea to spawn. Newsweek previously reported on how male lampreys attract females by releasing a smelly aphrodisiac pheromone in their semen.

Pacific lampreys used to be found widely from Mexico along the Pacific Rim to Japan, but due to a decline in population they are found in smaller numbers in California, Oregon, Washington, and Idaho.

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A lamprey is shown sucking tank glass. MIGUEL RIOPA/AFP via Getty Images

Bly runs the American River Lost and Found, where people can report items they have lost in the river so Bly can try to find them. He shared a video of the lamprey on the page.

Bly told CBS Sacramento he has been diving in the area for 40 years. "I've captured [on film] sea lions, river otters, crawdads and lots of crazy things [...] They [lampreys] would be high up there as a rare fish," he said.

Bly told Active NorCal: "I haven't seen a live full grown lamprey in decades in the American River.

"I've had sporadic sightings of babies. None more than 5 inches long and a few years ago I found half of a full grown but dead lamprey. But this is the first full 24-inch lamprey that I've seen since like the 1970s."