Invasive carp can cause serious damage to ecosystems. They threaten native wildlife — including the Clear Lake hitch, a culturally significant fish for the tribes who have lived along the lake and its tributaries for thousands of years. Carp also kick up sediment, unlocking nutrients from the lake bottom that fuel harmful blooms of algae. In spring of 2023, a team conducted a trial run of capturing Clear Lake’s carp that will inform a broader fish removal effort in the autumn.

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Luis Santana: The last species that the state of California lost was here in Clear Lake.

I have two kids and I’m always worried about them, but the fish thing is what gives me the most anxiety. I’m just like, dude, am I going to be able to save these guys?

Text on-screen: Clear Lake is the largest freshwater lake in California. It has sustained Indigenous people and wildlife for thousands of years. But today it is California’s most polluted lake.

Sarah Ryan (environmental director, Big Valley Band of Pomo Indians): One of the things that we know about Clear Lake fish is that they’re contaminated. In terms of the mercury contamination and there’s the sulfur bank mercury mine which is located on the eastern side of Clear Lake and it’s now a Superfund site listed under US EPA for cleanup because of the toxicity of it.

Luis Santana (fisheries biologist, Robinson Rancheria Pomo Indians of California): Mining mercury for the gold rush back in the 1800s came directly from here. There’s no containment for anything running off and it’s just all in the lake now.

Text on-screen: The lake is also rich in nutrients. Too rich.

KPIX clip: This time of year, the southern section of Clear Lake is never exactly clear. The annual algae bloom seems worse than ever.

Sarah Ryan: Harmful algal blooms are caused by a water body having too many nutrients in it. That’s kind of the bottom line of it. Nutrients are the things that are coming in from fertilizers, dirt roads, with soils that are high in phosphorus, septic systems that are leaching into a water body. It’s just over-enriched.

Luis Santana: The carp add to the algal blooms, one, because of the foraging and spawning behaviors, but also when they do die, the decomposing just add nutrients to the system. It’s phosphorus that makes algae grow at a tremendous rate. The fishes can’t really survive when there’s harmful algal blooms in place in the system.

Jordan Wein: Mic check, mic check.

Radio response: Copy.

Text on-screen: In spring 2023, as part of an ongoing rehabilitation effort, one team began testing a way to help mend the lake.

Luis Santana: And when you hear a beep — like, you’ll hear it. You hear it? That’s a carp.

Jordan Wein (senior environmental scientist, WSB Engineering): The estimated amount of carp in the lake is in the millions of pounds. They can really dominate a lake ecosystem. They can outcompete native fish. They grow really fast in their early stages and they can get very big and at that point there’s just no native predators.

Text on-screen: Originally brought over by European settlers, common carp are one of the world’s most invasive species.

They’re a serious threat to native fish, including the culturally important Clear Lake hitch.

Clear Lake hitch, Lavinia exilicauda chi

Jesus Campanero Jr. (Tribal Council member, Robinson Rancheria Band of Pomo Indians): The hitch population has been on a downward spiral. The stories that I was told by my elders is there were so many hitch that you could walk across their backs from one side of a creek to another. When it comes to the hitch, the carp are eating the eggs by thousands, you know, by the hundreds per bite. And so it’s not even giving the hitch a chance to try at life.

Luis Santana: We know there’s a lot of carp here, so just to see what we can get in 20 minutes.

WSB has done a lot of studies on this — they take out carp and they see the other populations basically bounce back.

Jordan Wein: While we’re out here right now, we are trying to use commercial-fishing techniques and sort of testing as many areas around the lake as we can. Hopefully this feasibility study will help us to know exactly where to target. So when the rubber meets the road and we are actually taking out as many carp as we can, we’re as effective as possible in the shortest period of time.

Text on-screen: The team hopes to remove more than a million pounds of carp in autumn of 2023.

Sarah Ryan: I have been so impressed by this community of Big Valley Band as well as the other tribes here and how they integrate themselves into the things that need to be done for this lake. This is the place that has protected them and nurtured them just as they’ve nurtured this area for thousands and thousands of years. So why wouldn’t we be listening to Indigenous voices?

Luis Santana: What keeps me going is, like, knowing that some of the work that I do is going to help one species one way or another.

Jesus Campanero: My hope in the future is really for us to come together and understand that it’s bigger than a fish issue. If we let this lake go, it’s bad for all of us. If my grandkids’ grandkids could see a clean lake one day, that would be my wish.