These eel-like fish look like horror movie monsters — and they’re back in SLO Creek

Any day now, eel-like parasites with sucker mouths will wiggle up San Luis Obispo Creek and build underwater nests in the creek bed to spawn.

Don’t worry, they won’t attack. They will, however, be food for other wildlife and improve the health and water quality of the creek, where the Regional Water Quality Board said elevated levels of fecal coliform is a problem.

These ancient, jaw-less fish, which look like something out of a bad horror movie, are called Pacific lampreys.

This is the third year in a row that the lampreys are in San Luis Obispo. That’s after they suddenly vanished for nearly a decade, leaving scientists bewildered.

Now that they’ve returned, San Luis Obispo Creek is a hotspot for those studying the mysterious fish.

City biologists are working with Cal Poly, the California Department of Fish and Wildlife and the U.S. Fish and Wildlife Service to understand how lampreys return and how that could be a model to return lampreys to streams up and down the West Coast.

That’s important because the fish are beneficial to the ecology of streams and to Native American groups who eat them.

What are Pacific lampreys?

You may be familiar with lampreys, known by some as “vampires of the sea,” thanks to their starring role in the made-for-TV movie “Blood Lake: Attack of the Killer Lampreys.” But these blood-suckers don’t usually suck on humans. They generally don’t attack humans unless they are starved.

adult lamprey.JPG
After feeding on fish for two or three years in the ocean, Pacific lampreys return to freshwater streams to spawn. This lamprey is shown building a nest, called a redd, in small gravel of the San Luis Obispo Creek. Donald Baldwin Courtesy of California Department of Fish and Wildlife

Pacific lampreys can grow up to two feet long. As adults, they feed by attaching to larger fish with their sucker mouths, filled with three large teeth and rings of smaller teeth. In turn, the lampreys are eaten by bald eagles, river otters and bears.

But when lampreys are young, they are filter feeders that clean stream water and look like garden-variety worms.

After five to seven years, the lampreys go through a drastic transformation. They grow eyes and teeth, and turn silver.

That’s when they travel from fresh water to the Pacific Ocean. After two or three years, the lampreys return to fresh water between December and March to prepare to spawn.

Hundreds of lamprey larvae are feeding in the bottom of the creek that runs past downtown Mission Plaza right now.

Pacific lamprey larva are abundant in the San Luis Obispo Creek, where the filter feeders improve water quality. Joe Johnston

“Many people don’t know they exist because they spend a lot of time under the substrate, buried. But they move at night,” said Damon Goodman, a biologist who studies lampreys with U.S. Fish and Wildlife. “They’re playing this function in our stream without most people noticing what’s going on.”

The disappearing three-tooth lamprey

When the lampreys went missing from San Luis Obispo Creek in the early 2000s, “It was kind of a shock,” Goodman said. “Despite that all other fish communities were healthy and happy, lampreys were gone.”

He huddled with other scientists, including city biologist Freddy Otte, and formed a working group to try to figure out what happened. Was it climate change and warming waters, or something else?

Through his research, he learned that the biggest threat to lampreys are barriers to passage, such as dams, tide gates and culverts.

Damon Goodman, a fish biologist with U.S. Fish and Wildlife Service, studies where Pacific lampreys live, including in San Luis Obispo Creek in downtown San Luis Obispo. Joe Johnston

Unlike salmon, who return to freshwater to spawn by jumping over waterfalls or other barriers, lampreys crawl. They use their mouths to suction onto a surface, then wiggle their bodies — similar to doing “the worm” on the dance floor — thrusting their bodies upward.

Lampreys can climb up waterfalls, but they can’t negotiate a right angle.

As it turns out, a 2004 adjustment to a weir at the mouth of San Luis Obispo Creek that was meant to improve steelhead passage likely prevented lamprey passage.

Goodman and his team found a quick $300 fix in 2013: a piece of metal bent over the side of the weir to provide lampreys with a climbing surface. By 2016, “Lo and behold, (the lampreys) returned,” Goodman said.

That simple ramp, nicknamed the LampRamp, was cheap and effective — and it could prove useful in the effort to return lamprey to other streams. “With small tweaks, we can make a big change for lampreys,” Goodman said.

Upstream side of the LampRamp.JPG
Three years after federal biologists installed this LampRamp near the mouth of San Luis Obispo Creek in 2013, Pacific lampreys returned to the waterway. They built nests with rocks and spawned in their second year back. Now, hundreds of young larvae are acting like water filters as they feed in the sediment. Courtesy of City of San Luis Obispo

While lampreys once lived in streams from Baja to Alaska, the number of streams they live in has declined since European settlement across the West. San Luis Obispo Creek is now the farthest south they live, Goodman said.

Lampreys are also known to travel inland in the Salinas River and into tributaries, including Paso Robles Creek and in the Nacimiento River on Camp Roberts.

When lampreys returned to San Luis Obispo Creek, it was “the first time they’ve recolonized a stream system anywhere,” Goodman said. “We’re hoping San Luis Obispo acts as a catalyst to recolonize drainages even farther south.”

“It’s kind of a big deal because it sets our expectations in other spots, where lampreys are trucked around barriers,” he said. “This suggests if you give them a way to recolonize, they’ll do it on their own.”

Pacific lampreys currently occupy about half of their historical habitat in California and San Luis Obispo Creek is the southern most population. Their historic range, shown in red, at one time stretched from Alaska south to northern Baja.

Tracking lamprey in San Luis Obispo Creek

Research of lampreys is far behind that of more charismatic fish such as salmon and steelhead, Goodman said. He’s working to answer basic questions about this slithery species.

“We know so little about them,” Goodman said, noting that when he started his research, “we didn’t even know where they were in California.”

Soon, researchers will know more.

The city plans to build a box with a camera in clear tubing adjacent to the metal ramp, according to Otte. As lampreys move through using their sucker mouths, the motion will trigger a picture, with a date and time stamp.

While lamprey are ancient fish, this is the first time the city is engaged in any kind of monitoring of them.

City biologists, with the help of the California Conservation Corps’ Watershed Stewards Program, are monitoring adult lamprey returns as well as where they build their nests, called redds. They’re doing surveys for redds, steelhead and lamprey right now, Otte said.

“It’s exciting to really quantify what that ecological benefit is,” he said.

The city is also partnering with Cal Poly to study the ecological niche that lampreys fill in the stream system, including whether they are beneficial in reducing pathogens in the creek.

“Just because you look at the creek and you don’t see any fish, doesn’t mean it’s not a thriving ecosystem,” Otte said. “The creek is an amazing place.”

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Monica Vaughan reports on health, Cal Poly, San Luis Obispo County, oil and wildlife at The Tribune. She previously covered crime and justice in the Sacramento Valley, is a graduate of the University of Oregon journalism school and is a sixth-generation Californian. Have an idea for a story? Email: