Can A Billion-Dollar Barricade Keep Carp Out Of The Great Lakes?

FLORA LICHTMAN: Hey, it’s Flora Lichtman. And you’re listening to Science Friday.

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Today on the show, drama with invasive carp and how to keep them in check.

JUANPABLO RAMIREZ-FRANCO: It’s absolutely raining fish. And part of it is that they actually have to be strapped into the boat to make sure that nothing goes wrong because these are big fish. They can be over 2 feet long, weigh upwards of 25 pounds.

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Now it’s time to check in on the state of science–

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FLORA LICHTMAN: –local stories of national significance. Today, we’re turning to the Illinois River for a fishtail gone wrong. Decades ago, non-native carp were brought onto fish farms on the Mississippi River to control algae and parasites. They escaped, thrived, and eventually flooded the Illinois River, outcompeting native species and generally wreaking havoc.

Environmental managers have tried to control the fish without much success. And now, one of the biggest fears is that these carp will find their way into the Great Lakes via Chicago and do damage. There’s a proposed project to stop the fish, but it’s expensive, and not everyone agrees it’s the best solution. Here to tell us more is Juanpablo Ramirez-Franco, environmental reporter at WBEZ and Grist. He’s based in Chicago. Juanpablo, welcome back to the show.

JUANPABLO RAMIREZ-FRANCO: Hey there, Flora, happy to be here.

FLORA LICHTMAN: So you went on a boat with these researchers studying the carp. Set the scene for me. What was it like?

JUANPABLO RAMIREZ-FRANCO: Sure. So we were lucky. It was this sort of breezy, easy, late summer day, and we were on board something called an electrofishing boat. Effectively, it’s this 20 foot long aluminum boat. And the funny part about it is that it has these two long sort of arms at the bow of the ship that when the captain of the ship is ready, he drops them into the water and then he hits the button and this generator pumps electricity into it and sends an electric shock into the water, which will stun most fish. That’s the idea, except for the invasive carp.

Now, when they get shocked they fly out of the water. And I’m not talking a foot, two feet. They’ll fly 10 feet to 12 feet out of the water. And at the bow of the ship, there are these two fish technicians who are there with nets, ready to catch them and wrangle them back in and put them in these live wells so that they can–

FLORA LICHTMAN: Wait, wait. So it’s raining fish, and you have people at the front of the boat with nets, who are just sort of trying to catch them in midair?

JUANPABLO RAMIREZ-FRANCO: It’s absolutely raining fish. And part of it is that they actually have to be strapped into the boat to make sure that nothing goes wrong because these are big fish. They can be over 2 feet long, weigh upwards of 25 pounds. And so they have to be strapped in to make sure that they don’t accidentally fall out while they’re doing this.

FLORA LICHTMAN: Wow, that is a wild image. And what are they trying to catch? Is it one species? Is it multiple species of carp?

JUANPABLO RAMIREZ-FRANCO: Totally. So what they’re actually doing is they want to get a sense of all of the species in a given area. So they’re not just looking for the invasive carp exactly. They’re also checking to see on native fish. How are they doing? Because part of what’s going on with these carp is that they’re eating the very bottom of the food chain, so they’re not leaving a lot of food for these other guys. So when they look at these native fish, if they see that they’re skinnier or not so big, they know something about the kind of impacts the carp is having just on that ecosystem.

FLORA LICHTMAN: And what are they trying to learn from these surveys?

JUANPABLO RAMIREZ-FRANCO: Yeah, so the big idea here is that scientists in Illinois want to where are the carp are and where they’re doing well. And so by knowing the abundance of carp in certain parts of the river, they can know where they should be focusing harvesting efforts. So that’s like the state’s only tool to really get these fish out, which is hiring commercial harvesters– that’s commercial fishermen– to get these fish out. The state will pay fishermen something like $0.20 extra per pound of carp. They also do these just giant commercial harvests. These are these targeted harvesting events over a couple of days.

So at one point, a couple years ago, they took out something like 750,000 carp, just like in a single harvest, which is unreal. But the state has also been taking other steps. So for example, a couple years back, the state tried to rebrand, or they did rebrand, the carp to something called copi to try to get people to want to eat this fish so that there is a sort of market solution to a invasive problem.

FLORA LICHTMAN: And they thought if they just gave it a new name, that people would be like, sure.

JUANPABLO RAMIREZ-FRANCO: Well, in their defense, there’s a lot of cases where this has worked, where people changed the name of– I think it’s Patagonian toothfish to something else.

FLORA LICHTMAN: Yes. Let’s talk about this giant fish blocking infrastructure project that’s been proposed. What is it exactly?

JUANPABLO RAMIREZ-FRANCO: Yeah, so Flora, you’re talking about the Brandon Road Inter-Basin Project. This is a decades-long plan to wedge in this underwater defense system into the river to make sure that the carp stay contained and don’t get any closer to the Great Lakes. And so basically, it’s like this upgrade to a lock and dam already existing, but with some more bells and whistles to make sure the carp don’t even get any funny ideas.

FLORA LICHTMAN: Such as?

JUANPABLO RAMIREZ-FRANCO: Such as a bubble curtain. So this is some continuous jets of bubbles that just are meant to deter the fish, these underwater speakers that make this noise that the fish are supposed to not like. There is an electrical barrier to really shock the fish, just in case, and also a mechanism inside the lock that flushes them and makes sure that they really cannot get through.

FLORA LICHTMAN: So is it approved? Where is it on the road to reality?

JUANPABLO RAMIREZ-FRANCO: So we are very much at the very beginning of all of this. So it got some approval back in 2020. But even then, it’s hit some roadblocks in the way, especially around who’s going to finance it. The state of Illinois and other Great Lakes states have been working with the federal government to figure out, is there a way to shift some of these costs onto the federal government and away from Illinois in particular?

FLORA LICHTMAN: How much would it cost?

JUANPABLO RAMIREZ-FRANCO: In total, it’s something like $1.15 billion, so not a small ticket item.

FLORA LICHTMAN: Wow. And is it controversial in any way? Or do people mainly agree, yes, this is what we should do?

JUANPABLO RAMIREZ-FRANCO: Yeah, so I would say that when you talk to scientists and local officials, something that you’ll hear a lot is that no one wants to find out what happens if they ever make it past Chicago. When you talk to opponents of it, what they’ll say is that there are cheaper ways to do this. They’ll say that maybe you could just close the lock and dam and just no more barge system, and then all of a sudden, you don’t have to worry about the transfer of the invasive carp.

FLORA LICHTMAN: Juanpablo Ramirez Franco is an environmental reporter at WBEZ and Grist, and he’s based in Chicago. Thanks for coming on today.

JUANPABLO RAMIREZ-FRANCO: Thanks so much.

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FLORA LICHTMAN: We have to take a break, but do not go away, because when we come back, we’re diving into the biology of these fish. Are invasive carp the cockroaches of the water?

CORY SUSKI: They grow quickly. They’re very abundant. They can have lots of offspring. And nothing can eat them. So they just become numerous. They just sort of spread. They’re just insidious.

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FLORA LICHTMAN: As we consider the pros and cons of this fish fortress, you might wonder, if these invasive carp are so hardy and so successful in these Midwest waterways, why haven’t they made it to the Great Lakes already? To find out, we called up a scientist who has studied this very question. Dr. Cory Suski is a professor of aquatic resources at University of Illinois. Cory, welcome to Science Friday.

CORY SUSKI: Hi. Thank you for having me.

FLORA LICHTMAN: These fish have been in the Illinois River for decades. Is it surprising they haven’t already made it to the Great Lakes?

CORY SUSKI: Yeah, somewhat because they’ve been doing a really good job of spreading themselves around at a bunch of other locations. But for some reason, in the Illinois River, they’ve stopped moving farther north, closer to Chicago and closer to the Great Lakes.

FLORA LICHTMAN: So why?

CORY SUSKI: There’s a lot of possible answers for that. For example, there’s a really active suppression effort that’s been going on downstream, trying to drive the population down. And as you get closer to Chicago, the habitat changes, meaning it changes from a natural river to an engineered channel. And the banks get really hard and get really armored. And they’re sort of like walls. And so it gets to be a very different river as you get closer to the city. So that could be deterring the fish. And the area that we’ve been looking at is maybe there’s something in the water that they don’t like that is keeping them from moving further north and closer to the Great Lakes.

FLORA LICHTMAN: There’s something in the water around Chicago. Is that the idea?

CORY SUSKI: Yeah, something coming from the city because the water is flowing from north to south. It’s leaving the city down the Chicago area waterway system. And so what we’ve been asking and wondering is, is there something there that’s in the water that they don’t like? Because animals will do that. If there’s something in their environment that they don’t like, they will just swim away. They will just leave. They’ll say, yeah, it’s not really for me. I’m just going to go elsewhere.

FLORA LICHTMAN: Well, what have you found?

CORY SUSKI: There’s a bunch of different pieces that have all come together. So first of all, there’s been a bunch of work looking at water quality and doing water quality monitoring in that part of the river. And there’s a lot of different chemicals and different compounds in the water that come through the Chicago area waterway system. Some of them you’d expect, and some of them– there’s just runoff from parking lots. So we know, as you get closer to the city, the water is very different than it is if you were to go farther downstream. And interestingly, the composition of the water changes right around the leading edge of carp. So there’s that correlational relationship between water quality and carp distribution that seems to fit together. But that’s correlational.

FLORA LICHTMAN: And you did a study on this. How did you actually do this work?

CORY SUSKI: So we did a couple of different things. So basically, we’re interested in, is there something there that the carp don’t like that cause them to not swim closer to Chicago? So to test that, we were not able to move carp closer to Chicago. That’s actually a good thing.

FLORA LICHTMAN: Because you don’t want them to escape.

CORY SUSKI: Right. Exactly. We’re not going to run that risk. But what we’re able to do–

FLORA LICHTMAN: Create the problem that you’re trying to avoid.

CORY SUSKI: Exactly, and then say, look, I told you. So what we were able to do, though, is move water. So we went to the Chicago area waterway system, and we grabbed water from a little bit farther upstream than carp are currently located. And we moved it to a fish hatchery in La Crosse, Wisconsin, at the USGS fish hatchery there, where they grow baby carp. And we were able to place baby carp from the hatchery into water that would essentially represent a range expansion and would be from an area where they are not currently found.

FLORA LICHTMAN: You’re simulating, basically, the carp going to this part of Chicago waterways that they don’t typically go.

CORY SUSKI: Correct, where we’ve never, basically, never really seen a carp before. What if we just put them in that water and try and see what happens?

FLORA LICHTMAN: What happens?

CORY SUSKI: So two things happen when you put them in the water. First of all, their metabolic rates go up, so they start burning more energy. And we’re thinking that this is because they’re processing some pollutant and processing some toxin that they weren’t exposed to downstream. And so again, it’s a higher energetic load and a higher energetic cost when they’re in that water closer to Chicago. And then the other thing that we saw was that they actually stop moving. And they more or less freeze when you just put them in the water.

So that’s a response from animals. When something is wrong in their environment, they have two choices. You can freeze, or you can flee. And so if you flee, you just get out of there because you’re like, oh, this is terrible. I’m leaving. Or you freeze, and you hunker down, and you kind of ride it out, and you hope it kind of goes away. And so what we saw then with the carp is if you take them and move them into water closer to the Great Lakes, where we normally don’t find them, they burn more energy, but they move less, and they actually stop moving.

FLORA LICHTMAN: Yeah that’s perplexing. Did you get any clues on which pollutant is the Carp-tonite?

CORY SUSKI: No because there’s a lot of things– like I said, there’s a lot of things in the water. And it could be to do with, or it could be to do with just what’s there, what’s not there. It’s kind of a– yeah, there’s a lot. There’s a lot to pick through. Another study that we did then was we took– similar kind of thing. We moved the water down to Havana, Illinois, toward the population core. And we looked at stress levels and the genes in their olfactory nerves.

And what we see is that if you take those fish and put them in water that would be closer to Chicago, they have increased molecular indices of stress in their olfactory nerves. So there’s something in their olfactory system. The analogy would be that there’s just something there, kind of a tingling and something unpleasant from an olfactory perspective that they don’t like.

FLORA LICHTMAN: Do native fish have this problem? Are other fish blocked by this, whatever’s in the water, around Chicago?

CORY SUSKI: Interestingly, no, because for a number of different reasons, in the study where we took fish to the fish hatchery in Wisconsin, we ran a similar series of tests with some native fish with a minnow super popular all across the Midwest and super popular in the Chicago area waterway. And they really didn’t show the same response.

FLORA LICHTMAN: Are they just tougher city fishes?

CORY SUSKI: I don’t know if it’s toughness or if there’s just something maybe less sensitive or less sensitive olfactory systems or something. We’re not really sure. The other thing is that we do know that the water quality in the Chicago area has been improving over the past few decades. Fish communities are growing. They’re getting more healthy. They’re becoming more diverse. So there’s a lot of good things happening. And so the point is, whatever’s going on in the city water, the native fish community seem to be fine with it. And they seem to be trending in a really good direction.

FLORA LICHTMAN: If the carp don’t like the water in Chicago, is that a reason not to build this barrier?

CORY SUSKI: No, I don’t think– I think we want to keep building the barrier. I think it’s a little bit tenuous, because again, there’s a lot of good work. The water quality is improving. And I think that what we’re trying to highlight with some of this work is that if something changes with the water, we could see carp start to move all of a sudden, where it’s kind of almost like where it’s really fortunate they haven’t moved, and they’ve been kind of stable, and that’s kind of working in our favor, and that’s bought us some time. But we don’t really know what’s going on. And that could change. And then suddenly, we’re going to find that carp are now farther north. They’re a little bit closer to the Great Lakes. And we don’t want to be caught off guard by that.

FLORA LICHTMAN: This is so dystopian, but are people like, well, this is a good reason not to clean up the water around Chicago?

CORY SUSKI: Yeah, this is not a call to continue polluting or to promote pollution. But having said that, if we can figure out the compound and what it is, maybe there’s a way to take advantage of it or recreate it or something. Again, until we figure out what the silver bullet is there, it’s a little bit tough to make predictions about what we could do.

FLORA LICHTMAN: What makes them so hardy, generally speaking? Should I be thinking of them as the cockroaches of the river, like indestructible omnivores that have a lot of babies, or what’s their secret sauce?

CORY SUSKI: Yeah, so I don’t if it’s that they’re indestructible. I think a lot of it just has to do with numbers. Where and why and how they spawn and have reproductive events, it’s still– we have broad general cues. They spawn in the spring. And they spawn when the river levels go up or whatever. But it’s tough to make predictions. They don’t spawn every spring. And they don’t spawn every time the river levels go up.

But when they do go up, there can be huge spawning events. And they can have lots and lots of offspring. So they can repopulate things really, really quickly. They grow pretty fast. And then they do reach a large size that makes them invulnerable to other predators. So a one-year-old carp is very big, compared to a one-year-old bass or a bluegill or something like that. And so they just escaped that. Nothing can eat them. So they grow quickly. They’re very abundant. They can have lots of offspring, so they just become numerous. They just sort of spread. They’re just insidious, as opposed to just being like cockroaches that are just really, really tough.

FLORA LICHTMAN: Where do you take your research next?

CORY SUSKI: So we would like to try and find out what it is in the water, at least get it close. There’s a cool example from the West Coast of coho salmon that were dying. And a group was asking similar questions. And you can fractionate the water. You can say, well, let’s take out the organic compounds. Let’s take out this type of compound. And you can strip down the water and repeat those tests with water of different fractions.

And you might not be able to identify the specific chemical. But you can at least get a class of chemicals, or maybe it’s a compound that’s coming from petroleum products, or maybe it’s a compound that’s doing this. You can identify that. And the group that’s on the West Coast, they had coho salmon that were dying in rivers. And they manage to fractionate the water and separate it all out. And they traced it back to a compound that comes from car tires. So you can find that needle in the haystack.

FLORA LICHTMAN: Good luck.

CORY SUSKI: Thank you.

FLORA LICHTMAN: Dr. Cory Suski is a professor of aquatic resources at the University of Illinois. Cory, thanks for taking us through this whole kettle of fish today.

CORY SUSKI: Thanks for inviting me.

FLORA LICHTMAN: Before we climb off this fish ladder, a few weeks ago, we did a story about lab-grown salmon. In that story, we blithely dropped an idiom. We said the amount of lab grown salmon produced is a drop in the bucket compared to how much salmon is consumed. Now, listen, we know y’all are nerds. Why else would you be here with us? But we may have to bestow the close listener crown on James from Ithaca, Washington, who did some actual math on whether lab salmon really is a drop in the bucket or not. Here’s James.

JAMES: At best, less than 10 tons of meat is produced in the lab, so we’ll just say 10 tons. Approximately 3.8 million tons of salmon are harvested each year. That is a ratio of 380,000 to 1. There are 591.5 drops in an ounce, multiplied by 128 ounces per gallon, and 5 gallons in many standard buckets. This comes to 378,541 drops in a bucket. So lab production is pretty exactly a drop in the bucket.

FLORA LICHTMAN: Thank you, James. We loved your message. And if you want to leave us a voicemail to fact check our metaphors or about anything else, the number is 877-4SCIFRI. We love hearing from you.

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Today’s episode was produced by Kathleen Davis. I’m Flora Lichtman. Thanks for listening.

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