More than 100 sea lamprey cling to a tank at the fish-sorting facility at Milford Dam. As of Monday, more than 5,000 lamprey had been counted at the dam. Credit: Maine Department of Marine Resources

On a list of cuddly or lovable creatures, the sea lamprey likely ranks just about at the bottom for most people. Lamprey are ugly, eel-like beasts that can latch onto their prey with a sucker disk mouth, then use their “rasping tongues” to suck nourishment from their hosts.

In that regard, they’re nearly perfect movie villains, like a cross between a zombie and a starving space alien water snake.

In reality, lamprey are important, and provide all kinds of benefits to river and ocean ecosystems. And (don’t be afraid) the Penobscot River is full of ’em right now.

In a recent fish passage report from the Milford Dam, Jason Valliere, a marine resource scientist for the Maine Department of Marine Resources Division of Sea Run Fisheries and Habitat, included a striking photo of sea lamprey that had been captured at the sorting facility in the Milford Dam’s flume.

Many had their sucker disks firmly attached to the glass of the tank, and dozens of others surrounded them. Valliere said his best estimate on the number of lamprey in the tank was 150.

“We often have hundreds of lamprey in the flume at one time,” Valliere said.

Sea lamprey cling to a tank at the fish-sorting facility at Milford Dam recently. As of Monday, more than 5,000 lamprey had been counted at the dam. Maine Department of Marine Resources Credit: Jason Valliere / Maine Department of Marine Resources

That was just a fraction of the day’s total haul — 2,374 lamprey — and that single June day’s catch accounted for nearly as many lamprey as last year’s seasonal total at Milford, 2,759. As of Monday, Milford’s seasonal count stood at 5,573.

Valliere said the run has slowed drastically, with about 50 lamprey being caught per day over the past several days.

The lamprey also head up into other streams and brooks along their trip to freshwater, including Segeunkedunk Stream in South Brewer. That upstream passage had not been possible until dams on the stream and on the mainstem of the Penobscot were removed.

Back in 2011, before the removal of two mainstem dams during the Penobscot River Restoration Project, we followed researchers as they counted spawning nests and lamprey in the Segeunkedunk.

At the time, University of Maine assistant professor Stephen Coghlan Jr. described lamprey as “charismatic,” and explained that lamprey help improve the habitat by creating their nests. And after the lamprey spawn and die, their decomposing carcasses introduce valuable nutrients into those streams and rivers.

When the lamprey are caught in Milford, they’re allowed to pass the gate and continue their trip upstream to their spawning grounds.

And while DMR workers know thousands have reached Milford, they also say that plenty of lamprey pass through the facility uncounted.

“Many sea lamprey can squeeze past the sorting gates and pass by uncounted so this is a conservative estimate of the population,” Valliere said.

And while the lamprey can make a person cringe, they’re very important for river and stream habitat.

“Adult lamprey transport marine-derived nutrients and minerals into the freshwater ecosystem, which boosts primary productivity in the stream and riparian environment supporting macroinvertebrates and native fish and other wildlife,” Valliere said. “Adult lamprey spawning activities loosen and clean stream substrate which improves water flow for invertebrates and provides refugia and foraging opportunities for small fish such as yearling brook trout and Atlantic salmon.”

And after those nests are built, Valliere said adult brook trout and Atlantic salmon have been known to use those sites for their own spawning activities.

In a 2004 paper, longtime fisheries biologist Fred Kircheis explained that anadromous lamprey, which go to sea and then return, don’t pose the same fisheries problems that have been blamed on landlocked lamprey in the Great Lakes.

“Although adult sea lamprey prey on other fish in the ocean they do not attach to other fish or feed in freshwater and die soon after spawning,” Kircheis wrote.

So, yes, there might be some pretty fearsome critters swimming around in the Penobscot River right now. And the video and photos might be a bit scary.

Rest assured, you have nothing to worry about.

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John Holyoke

John Holyoke has been enjoying himself in Maine's great outdoors since he was a kid. He spent 28 years working for the BDN, including 19 years as the paper's outdoors columnist or outdoors editor. While...