Sea lamprey are—gross. They’re a primitive fish with a long, slimy, boneless body. They don’t have jaws, but their round mouths are full of sharp, pointy teeth that help them hook on to other fish. Their tongue has little teeth on it too, and since sea lamprey can’t bite down, they flick their sharp tongues in a circular motion to gain traction and scrape a hole on other fishes’ bodies. It’s like something from a science fiction movie.

"A sea lamprey is a parasitic fish that attaches to fish in Lake Champlain and causes their death, either through direct parasitism or it leaves an infection in the fish which they succumb to and die from," explains U.S. Fish and Wildlife Service fish biologist Bradley Young.  He’s a surprisingly cheerful guy, given that his job is trying to murder hordes of nasty little sea monsters. Sea lamprey, he says, aren’t just an annoyance. 

Left to their own devices, lamprey can suck dry whole fish populations.

Scientists bring buckets of lampricide to the treatment boat. Photo: Sarah Harris

Sea lamprey haven’t historically been a major concern in the Saranac River. But when officials tested the river and its delta this summer, they found that it was home to a growing population.

The pesticide's name is niclosamide. It controls worm and snail populations. In some countries, niclosamide is used to treat ring worm in humans. Photo: Sarah Harris

"It’s in granular form that we’re spreading here out on the delta, in the non-moving waters. It’s a specific pesticide it’s actually designed for control of snails but it works for sea lamprey and has very little impact on any of the other fish in the area, the fish can swim out of the chemical block and are typically unaffected," Smith said. 

The boat pulls away from the dock and motors out to the middle of the delta.

We’re met by another U.S. Fish and Wildlife boat delivering big plastic drums filled with lampricide. The chemical’s made up of tiny, bright yellow round balls. It’s poured over a grate, pumped through a series of pipes, then sprayed off of the back of the boat. 

Sprayer booms on the treatment boat apply the lampricide in the Saranac River delta leading into Lake Champlain. Photo: Sarah Harris

We drive back and forth across the treatment area. Steve Smith uses a computer and a special navigation system to map where the lampricide has been applied. The boat appears as a red circle, the treatment field a big purple rectangle. 

Sea lamprey aren’t actually an invasive species. New studies suggest that they may be native to Lake Champlain, the Finger Lakes, even Lake Ontario, a leftover from the last ice age.

"There’s some genetic evidence that says that that’s the case, sea lamprey has always been here. But there’s a lack of historical evidence that they were around prior to the Champlain canal being built," Steve Smith said. 

It’s unclear if sea lamprey have lived in the lake for eons and recently experienced a population boom, or if they were introduced in the past century. The same debate is raging among scientists on Lake Ontario – and no one knows. But native or not, Biologist Bradley Young says sea lampreys pose a big threat to ecosystems and economies on Lake Champlain and Lake Ontario.   

"Well the fishery of Lake Champlain has been valued at over $200 million. And without that the economy—it could be a substantial difference to the lake Champlain tourist economy. We’ve had economic studies done that value the cost of the program vs. the benefit is a 3.8 to one ratio. So for every one dollar we spend on sea lamprey control, the Champlain Valley gets 3.8 dollars back in revenue," Young said. 

By early afternoon, the lampricide has taken effect. Seagulls skim the delta, snatching up dead lampreys that have floated to the surface. Some of them have washed up on shore. They look like little dead worms, and you can see the hoods where their teeth and mouths would’ve developed. It’s kind of creepy – but at least these lamprey won’t be feasting on fish anytime soon.

The Fish and Wildlife Service, will continue continue to apply lampricide to Lake Champlain tributaries over the course of the fall. The treatment area will include Mill Brook, Mount Hope Brook, and the Great Chazy River in New York and the Winooski and Missisquoi rivers in Vermont.