If you’ve ever seen images of a fish with a scary, tooth-filled sucker mouth, you’ve seen pictures of a sea lamprey.

These long fish are an invasive species in all of the five Great Lakes, including Lake Erie. Sucking onto the side of fish in the lake, the lamprey destroys as it feeds. There is good news, though— we are able to control their population. To get into the basics of sea lamprey control in the Great Lakes, I spoke to Dr. Marc Gaden, the communications director at the Great Lakes Fishery Commission.  Below, you’ll find the details of a discussion about  topics such as the chemical used to control larval sea lampreys to the feasibility of eradication. 

Q: How did the sea lamprey enter into the Great Lakes?

“Shipping canals. So there are maybe four main ways that invasive species get into the Great Lakes, one is through recreational activities, so maybe taking a boat from one lake to another or bait, you know, fish that’s exotic that happens to be mixed in with your bait. Another way is through canals and waterways, these shipping canals. In the Great Lakes, the mother of all shipping canals was the Welland Canal, which bypassed Niagara Falls. But another canal is the Chicago Area Waterway System, which is a potential conduit for Asian carp. A third way is ballast water, and that’s the water that’s used to stabilize ships as they cross the ocean, or you know, go from one end of Lake Superior to another, and you could have live critters living in that and can hitch a ride, and then then the fourth main way is through aquaculture. So you could have an escapement, for example, from a fish farm, through a flood. So the lamprey came in through shipping canals … there were shipping canals like the Erie Canal that connected the Hudson River to Upstate New York in the 1800s, and that’s how they got into Lake Ontario, and then when the Welland Canal, which was built a long time ago, it was modernized significantly and renovated, almost 100 percent, back in 1919, that’s how the lamprey got into Lake Erie and then the other Great Lakes.”

Q: Are sea lamprey a problem in all of the Great Lakes?

“Huge problem in all the Great Lakes.”

Q: When in the lakes, how do sea lampreys damage the native environment?

“So what lamprey do is they have an interesting life cycle, that actually turned out to be their killing seal. Lamprey— since it’s a cycle, I’ll start anywhere — lamprey spawn once in rivers. Once in their lifetime, after about a year out in the lake, they spawn once and then they die naturally, so it’s like a salmon, they do a spawn and then they die. The lamprey larvae in the river, when they hatch, will drift downstream from a rocky nest to an area that’s sandy and silty, and burrow into the bottom of a river. And the larvae will live for anywhere upwards of four years, sometimes longer, in a river bottom about the size and the shape of an earthworm, and these innocuous larvae will just eat whatever drifts by, so like detritus, rotten leaves, whatever. And then when the conditions are right, the lamprey living in the river bottom will transform or metamorphose from that larvae into the adult, with that grotesque mouth that you probably have seen. They migrate to the open lake, they’ll spend a year preying on fish there, and they’re top predators, so they have a top-down effect, and they do so by grabbing onto the side of the fish, the mouth is a suction cup so it holds on, the teeth anchor the lamprey onto the side of the fish, and then the lamprey has a file-like tongue that will bore a hole through the side of the fish. And that’s how they feed. They’ll kill about 40 pounds of fish moving from fish to fish, and then when the spring rolls around, their digestive systems shut down, they can no longer feed. They have one thing in mind and that’s spawning. And they move back to streams to spawn. And that’s the lamprey life cycle. They do their damage in the open lake, preying upon fish out in the lake.”

Q: What are some ways that we’re trying to reduce the population of sea lamprey that are already here?

“So lamprey control is actually a huge success story in the Great Lakes. So out of 180-some non-native species, on a basin-wide level, we have the ability to control two on a large scale. Number one is the alewife … that’s controlled by stocking predators like trout and salmon and lake trout, but the second is the lamprey. We can control the lamprey because in a way we got lucky. Back in the 1950s, shortly after the commission was formed, the commission went into high gear because the commission was told, ‘You will find a way to control lampreys and then you will carry it out.’ So they immediately focused on the larval phase. When they’re living in stream beds, because the ability to get lamprey when they’re out in the lake would be impossible. You can’t net them, you can’t commercially fish them, you can’t put bait out because they’re going after fish, not like a net or something. They’re not going to suck onto a piece of dead fish. So that’s not how you’re going to catch them. They focused on the larval phase and the idea was to kill the larvae before they have a chance to metamorphose into that lethal adult. And so they tested about 7,000 different chemicals up at a facility near Roger City Michigan, and they finally discovered one that was lethal to larval lamprey and not harmful to fish. Or wildlife or aquatic organisms in any meaningful degree. That was the holy grail and they discovered it. And the lampricide is called TFM, and it’s applied to streams where lamprey are found on a four year rotation, because remember they don’t metamorphose until they’ve been there for about four years, and it kills the lamprey larvae and doesn’t harm the fish in the stream.”

Q: Is there any concern with the use of lampricide harming native species of lamprey?

“So native lamprey are an issue. Some of them are even threatened, or you know, on the ropes, they’re not listed as an endangered species but the lamprey control folks are acutely aware of the effect of lampricide on native lamprey, and they are very sensitive to protecting any native species. So whereas the lampricide would not be harmful to a native trout or a native salmon or even a non-native trout or salmon, the lampricide would be harmful to the native lamprey. There’s a couple of things that we do to mitigate. Number one is we got a bit lucky in that the native lamprey and the sea lamprey, although there is some habitat overlap, it’s not one for one. And we also got lucky that the native lamprey are often far upstream of where the sea lamprey would be. So you don’t treat — if there’s a hotbed of native lamprey, you wouldn’t treat that section of the stream with the lampricide. And number two is that you can then take protocols that way where you just wouldn’t treat those sections of the stream. Number three, though, if there are areas where the native lamprey are abundant and not threatened, you would sacrifice those because of the need to get rid of the sea lamprey. But that’s pretty— it doesn’t happen all that often. But there is some— the mortality of native lamprey in our lamprey treatments.”

Q: Does the fishery commission advocate for any preventative measures to keep sea lamprey out? Or is mostly just controlling them once they get in?

“The lamprey have made the Great Lakes home, and in fact they don’t migrate out to the ocean, i.e. out of the Great Lakes basin in any way that would be meaningful, they essentially treat the Great Lakes as the ocean, and so trying to keep them out of the Great Lakes— that ship sailed in the 1920s. And there’s nothing we can do about that. The Great Lakes Fishery Commission is interested in keeping out invasive species, and so we’re very active in work on the Asian carp, we’ve been active in trying to get the U.S. and Canada to enact ballast water regulations, we keep an eye on aquaculture, and we certainly support measures that folks do like mainly state level and Sea Grant to address bait transfers or recreational activities.”

Q: Have you seen a reduction in the population of sea lamprey? Can they ever be eradicated?

“Eradication is not seen as possible largely because the lamprey are all over the place and they’ve made the Great Lakes home. And we have calculated what it would cost to go after that last mating pair if you will, and it becomes, from an economic perspective, in the — probably the hundreds of millions. I mean, to just go after that last mating pair, that’s per lamprey, you know, per pair of lamprey, but that’s academic. The problem with invasive species is they make the lakes their home and then you’re stuck with them. Right? So the issue is what do we do? Well we treat to where, treat in the streams to where it’s cost effective, and where it’s no longer economically feasible to go after that next lamprey, so as you’d expect, if you remember economics, you know a curve where if the y axis is number of lamprey and the x axis is money, you draw the line on where it’s just not worth it to kill that next lamprey. And that tends to be in the neighborhood of about 30 million dollars a year to do lamprey control. And then what you’re getting is the difference in percentage is like 95 percent reduction to a 95.1 percent reduction for that extra million dollars and it’s like that’s just not worth it. To get to 99 percent reduction, you’re spending hundreds of millions of dollars and it’s just not worth it … we have reduced lamprey populations by about 90 to 95 percent in most of the Great Lakes. From the fishery perspective, we’ve gone from losing about 105 million pounds of fish every year to lamprey — this would be the 1940s and ‘50s before we started control — 105 million pounds we used to lose. We lose around 12 million pounds to lamprey today.”