Think Out Loud

Reintroducing carp could help control a fast-growing weed that’s taking over Lincoln City’s Devil’s Lake

By Rolando Hernandez (OPB)
Feb. 27, 2023 5:28 p.m. Updated: Feb. 27, 2023 9:15 p.m.

Broadcast: Monday, Feb. 27

In Lincoln City, Devil’s Lake provides a picturesque destination for recreation. But a fast-growing water weed known as Canadian pondweed is now taking over the lake, clogging motorboat engines and competing with native plants for nutrients. The Oregon Department of Fish and Wildlife has recently adopted rules that allow officials to reintroduce a grass-eating carp to the area. Joshua Brainerd is the executive director of the Devil’s Lake Water Improvement District. He joins us to share the issues this weed is causing and how this carp could help control vegetation.


This transcript was created by a computer and edited by a volunteer.

Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. Devil’s Lake in Lincoln County is a picturesque destination for recreation, but a fast growing water weed known as Canadian pondweed is now taking over the lake, clogging motorboat engines and competing with native plants for nutrients. So the Devil’s Lake Water Improvement District asked the state if they could reintroduce a grass eating carp to essentially munch away their problems. A week and a half ago, the Fish and Wildlife Commission agreed. Joshua Brainerd is the executive director of the Devil’s Lake Water Improvement District and he joins us with more details. Welcome to Think Out Loud.

Joshua Brainerd: Good morning, Dave.

Miller: Good morning. For people who haven’t visited Devil’s Lake yet, can you describe it for us?

Brainerd: I think you really kind of capture it there with your intro very well. It is a beautiful, picturesque piece of water surrounded by mountains and actually quite a bit less developed than a lot of the areas that we see right now other than some of our Alpine lakes and some really remote areas. It has a really incredible geographic location in that it’s located directly next to the Pacific Ocean, connected by arguably one of the world’s shortest rivers at 120 feet. But that’s been the source of some debate.

Miller: Whether it’s a river or not, you mean?

Brainerd:  Yeah. They based it on the high tide line and [by] some definitions… I believe it was a Boy Scout organization from somewhere in the Midwest several years ago, before my time, who had contested that.

Miller: Okay, that will be a topic for another day. Because as I mentioned, we called you up because the lake in recent years has been really overrun by this waterweed. What is it?

Brainerd: It is called Elodea canadensis. It’s a very common weed in most areas, and in some areas it can be native, even in our state here in Oregon. What’s happened is we have some very, very good conditions for those plants to grow and indeed that’s why they grew. And there was an over-vegetation problem in Devil’s Lake approximately 40 or so years ago back in the early ‘80s, which led to them forming the district. But the plant itself is extremely prolific. We’re not the only ones dealing with it, especially out here in the Pacific Northwest. Alaska, and their fisheries and wildlife commissioners are having a very difficult time right now. They’ve committed I believe $100 million to this issue just to protect their salmon fisheries alone. So it’s something that a lot of places are struggling with.

We unfortunately had it up here in our lake a little under three years ago, whereas previously we had almost no vegetation in the lake to the point where we have been running a committee for several years to try and revegetate native plants. However, that one’s been shelved as you can imagine at the moment, as we’re dealing with just the catastrophic amount of growth of this plant.

Miller: Can you put it in perspective? How much is it in there? Whether at the bottom of the lake or or visible at the top?

Brainerd: It is visible everywhere in the lake. As I mentioned, we had little to no vegetation less than three years ago. Within two years, we went from what would likely be 2-3% vegetative cover at best to 85% or more. There’s one issue with this plant as well: it grows in shallow areas extremely well, and Devil’s Lake is definitely a shallow lake. Additionally, it grows to pretty great lengths. So we have unfortunately seen this plant in beyond 12 ft depths of water, which is indicative of its growing characteristics.

Miller: Do you know why the last three years have seen such explosive growth? What is it about the water right now, or the climate, that has made this weed take off?

Brainerd: There are several factors that can definitely be involved in that. And you even mentioned the climate, we definitely have warming waters, as do many places around the world and something that we’re waiting to see what the total effects we have on that. Devil’s Lake, itself, is a natural “peat bottom” waterway, which means it holds a great deal of nutrients and typically always has. They were talking about tens of twenties or more feet, geologically, of really rich substrate material that contains these heavy nutrient loads.

And what that does [is] many of those plants in the tubers and the way they propagate are still in that lake and sometimes they can go dormant for a very long period of time. As soon as those conditions are right, everything is already lined up for those plants to go. And that is what we believe has been happening here in Devil’s Lake. We had, unfortunately, perfect growing conditions for this plant. And with the lack of competition and the speed at which it propagated itself, it’s been very difficult to keep up.

Miller: What has this meant in terms of the lake’s ecology?

Brainerd: We had installed, [in] about 2018, an aeration system. Because our lake once again didn’t have many plants in it, and for several years that experienced harmful algal blooms and that has definitely led to the clarity of the water. The past several years we’ve had record great water quality, [according to] many reports, and pretty much the community [is] in agreement that it’s the best that has been in quite some time.

Miller: Am I right that five years ago or so, it literally meant putting in pumps that put air at the bottom of the lake in different places?

Brainerd: Yeah, there’s several different ways you can do that. What Devil’s Lake [inaudible] for us [is] what’s known as the lake-bottom aeration system. And we have one shoreside air compressor located at a county-owned boat ramp, [with a] very small footprint. And from that we run a small manifold to the shore line, and on the lake bottom, there are 24 individual ceramic diffusers. And what that does is puts a fine bubble in the water over a predetermined location area. And we chose that based on a lot of data.

Miller: But that was some previous work you had done because of the lack of vegetation and the fear of algal blooms.

Brainerd: Correct.

Miller: So what has happened since then? We’ll get to recreation and the economy. But what has it meant, say, in terms of salmon or the other species that would like to make their homes in the lake? What has this weed meant for them?

Brainerd: Well, in terms of wildlife, we’ve had a really great resurgence since the aeration, and water clarity had returned. Everything from salmon to warm water fish. Indeed, we have even more trout that overwinter, because fish and wildlife does stock trout in many waterways and Devil’s Lake is one of those in the state. And previously, when we had anoxic conditions (no real oxygen on the bottom of lake during intermittent periods) a lot of those fish would die off, and we just wouldn’t see that biotic life really carry over.

We haven’t seen a lot of turtles, reptiles, amphibians, a lot of your key indicator species during those years when there were the harmful algal blooms as well. We’ve seen, in the past few years and up until now, a real boom and a lot of that biotic life. However, recently, and especially this last year, with the amount of weeds that have taken hold in the lake and some of the ecological problems we’re having, such as giant mats and rafts of dead weed, detritus floating on the lake, we’ve seen a shocking over-abundance of waterfowl. One thing Devil’s Lake does too, yearly, and always has, is we test for E. coli samples and waterfowl can definitely be a source of those contaminants in a water body as well.

So we have yet to see all the full effects and it is certainly a moving target, but we’ll continue our monitoring program as we move forward throughout all of our water quality management efforts.

Miller: So that’s the water management and the ecology question. What about recreation? What has this profusion of water weeds meant for boaters in particular?


Brainerd: We’re a pretty heavily recreational lake, especially when you consider things like non-motorized paddle boards, stand ups, kayaks and power boats as well. This past year, many people just did not come back. They decided against recreating on the lake. There’s quite a vibrant rental property business around the lake for part-time homeowners and many of them saw a major reduction in the amount of people wanting to come to the lake, just based on their concerns with our weed growth.

Miller: So let’s turn to this plan because my understanding is that you had to convince the Fish and Wildlife Commission to change one of their administrative rules to make it possible for you to go forward [with the carp plan]. What was standing in your way?

Brainerd: There are a couple of rules that Fish and Wildlife has put in place to protect the general public and our waterways around the state, and rightly so. A couple of those [rules] are if they’re connected to another water body. One of the major concerns is if [the carp] get out, they can impact another ecosystem somewhere in an unintended way. And of course we’re able to address any of those concerns, given our plan and procedures that we’re working on.

Technically there wasn’t really a lot to change. It was a rule that was put in place, like I said, for basic environmental protection reasons. Several years ago they had done that after Devil’s Lake had stopped once before. But Fish and Wildlife has done a great job working with us here at the district to try and come up with an agreeable plan to let this happen.

Miller: And what is that plan? What are you actually planning to do this spring?

Brainerd: We will be releasing a predetermined number of grass carp. We’re still settling on the exact amount of those, but it will be quite a few less than they had in the past. So we can definitely meter and monitor that as it goes. But essentially it will be ordering that number of grass carp from a Fish and Wildlife approved fish farm in Arkansas. And those fish will be transported here to a few various locations in Devil’s Lake where we’ll be releasing them. Each one of those fish, before they come here to the lake, have to be individually certified by the US Fish and Wildlife Service. And each one will have a unique radio tag implanted in each individual fish as well.

That was one of the ways we were able to work with Fish and Wildlife, and being able to satisfy some of their requirements. After that, we’re going to be monitoring if we have any of the fish die off, we’ll remove those, freeze them, send them to Fish and Wildlife and they’ll likely send them to their lab for a necropsy to see if there’s any issues or just to keep an eye on the program of what we’re doing.

Outside of that, there are a few different methods we’re going to use, between drone flights and some in-water, basic sonar methods to take bottom hardness, and a few other measurements. Which should give us a really good handle on the impact these fish are having.

Miller: As you noted, the biggest concern or one of the biggest concerns of state officials was that these introduced carp would get out of Devil’s Lake and go somewhere else where instead of fixing a problem, they might cause some new problem. What are you going to be doing to prevent that from happening?

Brainerd: Well, besides the radio tag, which is something of course is very, very unique, especially on each individual fish. Grass carp are not anadromous by nature. They stay in the lake where they’re at. They’re a freshwater fish solely. If they get out into the ocean, they’ll die. So the Fish and Wildlife did not have a concern with them escaping into a marine environment. None of the tributaries that come into Devil’s Lake are large enough to support [them] or [they’re] not the correct environment for these fish to live in anyway - not open water environments. So they don’t have any major hold backs right now as far as their concerns about the fish escaping. If for some reason anything does come up in the future, we have several options we can use, and one of those primary ones is fish screening our inlets, if there is any concern.

Miller: Am I right that these are also sterile fish so they can’t reproduce?

Brainerd: That is correct.

Miller: So the fishery in Arkansas, they sterilize these fish before they ship them to you?

Brainerd: Correct. They are each individually bred. Each one, after they’re bred, is individually [genetically] tested to ensure that it is indeed sterile. Like I said, each one has a unique identifier and fish tag and then at the end of all that process and during it, the US Fish and Wildlife Service certifies all of them.

Miller: How much grass can a grass carp eat?

Brainerd: Depends on the weight and the temperature, but an average is approximately two pounds per day.

Miller: Wow, that that sounds like a lot.

Brainerd: It is, but when you’re talking about the biomass we’ve seen grow in Devil’s Lake, hundreds of thousands of tons of vegetation sprouting up every day and dying and moving around right now . . .

Miller: So, then this is going to be a multi year process?

Brainerd: Absolutely. In addition to grass carp, Devil’s Lake has leased an aquatic vegetation harvester, which is a mechanical means of removing a lot of this vegetation, especially things like the floating mats that tend to be a little more difficult and things like grass carp will not feed on, generally speaking as much. And that is really our scenario at the moment.

We have tried some very limited pilot studies with herbicides that were EPA approved and eco-friendly and unfortunately, we did not have a good effect from those. They were not effective or efficient for what we needed to use. Throughout [our] conversations with the Oregon Department of Fish and Wildlife, we will be operating the mechanical harvester along with the grass carp, likely for several years to come as we monitor what happens with the amount of weed growth.

Miller: And just briefly, we have about a minute left, but what efforts are you taking to prevent boaters who do go to your lake, to prevent them from introducing this weed into other bodies of water in Oregon where it’s not currently found?

Brainerd: Well, this is an issue that really a lot of folks are dealing with now and especially more recreational water bodies than even before. There’s quite a few people out on the water and even more recently and everything from paddleboards to jet skis… many different ways to approach that. Some are very difficult. We put up signage, we do quite a bit of public outreach. We do a lot of social media outreach along with that, as well. We have monthly board meetings and as much public contact and connection and education we can do, and the physical route is things like boat-wash stations.

If you can indoctrinate people enough to use those, and to, I guess [encourage] some good environmental stewardship and to take advantage of those, that is a great way to decontaminate boats and equipment from and between any water body. Unfortunately, like I said, that’s something that’s very difficult to do. Those systems are expensive to put in, someone has to run them and take care of them. And typically speaking they need an attendant. Unfortunately, now it’s extremely difficult to find that human help with some of these things, but there are some options we’re looking at. There are some waterless cleaning systems and some other things like that. So personally, I am looking right now in our district’s budget season for some additional funding to hopefully put those at some of our many - I believe we have five boat ramps on this lake alone.

Miller: Joshua Brainerd, thanks very much.

Brainerd: No problem. Nice talking with you.

Miller: Likewise, Joshua Brainerd is the executive director of the Devil’s Lake Water Improvement District.

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