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How one scientist enlisted a lakeside community to study (and eat) invasive crayfish

For 12 years, UW's Julian Olden has studied the native and invasive crayfish populations of Sammamish's Pine Lake. But the citizen scientists who live onshore are his secret weapon.

A scientist holds a crayfish

Since 2007, Dr. Julian Olden, professor at the University of Washington's School of Aquatic and Fishery Sciences, has sampled Pine Lake nearly 50 times. “I think we all do work hoping it's going to inform a better process around natural resource management and contribute to science in a basic or applied way," said Olden. (Hannah Weinberger/Crosscut)

Dr. Julian Olden’s research subject is unhappy. The granola-bar-sized red swamp crayfish in his hand gesticulates wildly, her spiky red claws sweeping outwardly like a malfunctioning C3PO. She’s looking to pinch Olden’s fingers, but she won’t find them: He’s holding her shell just outside her legs’ range of motion. 

“Let’s see, I’m guessing 63,” he says, eyeballing her body length in millimeters, excluding her tail.

Our canoe rocks in Sammamish’s 85-acre Pine Lake, crowded by a park and dozens of lake houses with docks and man-made beaches. Midsummer, hordes would be out to splash and set nonmotorized boats adrift here, but in September, our only company is a swimmer tugging a yellow buoy. Olden positions the crayfish (“crawfish” is also acceptable, he says) inside metal calipers, from the equivalent of her nose to the base of her ribcage, and gives a gentle squeeze. 

“It's right on 63 — I'm not lying,” he says with a laugh, eyes crinkling at the corners. “That's pretty good. I don't need calipers anymore. Calipers out the window!” He logs other measurements, sex, location and a few notes before plopping her back into the water.

Olden drops a crayfish back in the water
Olden monitors changing populations of invasive to native signal crayfish in an effort to document environmental changes. (Hannah Weinberger/Crosscut)

It’s not surprising that Olden’s dimensional sense for crayfish is dialed in. A professor at the University of Washington's School of Aquatic and Fishery Sciences, Olden has floated Pine Lake four times each summer for 12 years to study them, and we’re out doing his final sampling of 2019. But it’s jolting to see him return her to the lake: Red swamps, the pride of Louisiana crayfish boils, are invasive in this lake. She’s not supposed to be anywhere in Washington, period. But she’s an unwitting accomplice in Olden’s effort to evaluate invasive species management in a changed lake. 

To monitor changing population dynamics of invasive to native signal crayfish, he sets 40 traps full of large-breed dog food around the lake perimeter on summer weekends, sometimes with his daughter. Olden then analyzes and releases, rather than removes, animals unlucky enough to crawl into them, so he can evaluate the ecosystem’s natural responses to invasion. 

It’s humble research, repetitive by design. There’s no dedicated funding. But to Olden, it’s a proving ground for a looming ecological disaster, and he’s the only researcher behind enemy lines. He’s sampled a couple hundred Western Washington lakes, but Pine Lake has historic importance: The state’s first red swamps were found here in 2000, and they’ve since spread to about a dozen other bodies of water in the state. So far, he’s shown that signals and red swamps tensely coexist in Pine Lake, with human intervention; he spent a few years removing red swamps to gauge management impacts. But in many invasions, native crayfish disappear completely. 

Invasive crayfish are the main reason for declines in native crayfish; according to Oregon Sea Grant, 45 percent of North American crayfish are at risk of extinction. There are about 380 crayfish species in North America, but the only one native to Washington is the signal crayfish. And because crayfish play huge roles in food chains, threats to them are serious.

“The biomass of crayfish alone exceeds every other animal that lives on the bottom, combined,” says Dr. Brian Roth, a Seward Park-raised crayfish researcher at Michigan State University handling a more-recent influx of red swamp in Michigan. “There’s a tremendous amount of [nutritional] energy that flows through [them].” 

Studying one small, unassuming animal in one small, unassuming lake might not seem important, but it has implications for how we manage future invasions. More than that, Olden’s study depends on involvement of people living on the lake: By tapping into the human power of the local population, he’s showing citizens can play a key role in keeping our lakes alive. 

How to watch a crayfish 

While sampling more than 100 Washington lakes to establish invasive and native crayfish baselines at the start of his UW career, Olden learned biologist Karl Mueller discovered red swamps in Pine Lake in 2000, and saw an opportunity to watch an invasion develop in a common environment. 

“It’s always like, ‘Well, it's just one lake. What does one lake tell you?’ ” Olden says. “I can tell you this lake is very similar to many of the other lakes around here. So as opposed to spreading yourself thin and visiting [20 or 30] lakes every 10 years, … I think there's value in going to one lake multiple times over a decade. Then the really complicated questions can be answered.”

Since 2007, he’s sampled Pine Lake nearly 50 times, relying on discretionary funds from when he first joined UW’s faculty in 2006 to pay for $10 traps or $20 of dog food. “It’s a small amount of money, but with huge rewards in the end,” he says. 

Multidecade invasive species monitoring projects are rare, but valuable, for evaluating species permanence, Roth says. “We would not know the outcome of invasions, in a lot of cases, if we did not have long-term research,” he says. “It really helps us understand and perhaps mitigate some of their impacts.” In Washington state, invasive aquatic species of greatest concern include zebra and quagga mussels and New Zealand mudsnails.

It’s a mystery how red swamps arrived in Washington, though there are theories (one of Olden’s favorites is that schoolchildren released class pets into lakes). There are only a handful of crayfish researchers in the Pacific Northwest, and the state lacks funding to fully monitor invasive crayfish, wildlife officials say. 

Allen Pleus, an aquatic invasive species expert with the Washington  Department of Fish and Wildlife, says the department doesn't monitor for invasive crayfish in Pine Lake. “We rely a lot on coordinators and cooperators such as Julian to provide a lot of data on the ground,” he says. At least 25 of King County’s hundred-odd lakes have been impacted by invasive species.

Native crayfish are linchpins of food chains, and threats to them are serious. Crayfish eat primary producers such as plants, but also fish eggs or, given the opportunity, each other. They in turn feed fish, birds, raccoons and more. 

“Any time you put in a new organism which may disrupt that [food chain, animals] might feed differently,” Olden says.

Invasive crayfish can completely alter the unlucky ecosystem targets of their diaspora. They put pressure on fish eggs, limiting sport fisheries; clear-cut aquatic vegetation other species depend on for food and shelter; and create erosion, red swamps especially. In pursuit of perfect hidey holes, they burrow channels in lake and stream banks that threaten to destabilize nearby building infrastructure while making water siltier. Diseases like white spot syndrome, currently wiping out entire crayfish populations in Louisiana, also concern Pleus. 

Where invasive crayfish have shown up, native species have also largely failed. Early studies at Pine Lake show signals are often outcompeted for territory by red swamps, limiting shelter necessary to hide from predators. While signal crayfish reproduce once a year, “red swamp crayfish reproduce twice per year, sometimes three if it’s a mild winter,” Olden says, handing me a red swamp to evaluate for myself. 

“Don't get me wrong, the signal is a tough crayfish,” he adds. “One on one, they can hold their own, but as soon as it's 20 to one, it's impossible.”

As far as Pleus knows, most Washington signal populations are healthy, “[but] there are no monitoring efforts out there to determine population status and distribution.” 

To put hard numbers on the red swamp threat to Pine Lake, Olden enlisted the help of the people who care about the lake most. 

Enter the crayfish destroyers 

While Olden visits Pine Lake outside the summer study season, he enlists locals to keep regular tabs. 

“I can't think of anyone better to collect data than the people living on the lake,” he says.

Nearly 50 or 60 households — half the population on the lakeshore —  have assisted in trapping since Olden first presented at Pine Lake Community Center in 2013.

“This project required a commitment,” Olden says. “If no one showed up for that first meeting, then the project wouldn’t have happened. Luckily they were excited about it.”

It was his first foray involving nonscientists in data collection. “There's a science behind citizen science. … It's building and maintaining relationships so that you can get the data, in this case,” he says. 

“Dr. Olden’s group is not the first group to engage in [citizen science] but certainly in terms of crayfish, it’s pretty unique,” Roth says. “The efforts there really demonstrate that it is possible to galvanize the general public to take action on invasive species.”

It helps, Roth says, that Olden is both a productive scientist and “a nice guy.” 

“One of the amazing things about Julian is how many collaborators he can get into his orbit as a scientist. ... That really speaks to his ability,” Roth says. Roth’s team has done community outreach, but “not to that extent. That is a special case.” 

The project has had three phases. In the first four years, Olden alone trapped, measured, logged and returned crayfish to the lake, establishing undisturbed population baselines.

From 2013 through 2016, Olden and the volunteers began a removal effort to see whether human intervention reduced red swamp numbers over time. 

Volunteers euthanized red swamps by sticking them in freezers. “Freezing them is the most humane,” Olden says. Some ate them. “Ask any wildlife scientist, [...] you always have to taste your study organism,” Olden jokes.

Volunteers removed 8,674 crayfish over more than 175,000 hours of trapping in that period. To date, the project has removed more than 10,000. 

“There’s just incredible wealth in the volume and the quality of data that can be collected by people,” Olden says. 

Honing the experiment was a matter of trial and error: If the traps were too shallow, mallards dove down and banged on the sides to release dog food. Raccoons pulled up crayfish traps and ate study subjects. 

Olden was constantly dropping off supplies and picking up crayfish samples “like a milkman, but the reverse,” he says. “[People] gave all their time and I think that's remarkable.” 

Volunteers became helpfully competitive. Two 12-year-old boys spent their summers removing hundreds of crayfish with their grandmother, for which Olden rewarded them with shirts boasting, “Crayfish fear me.” 

“Julian is down to earth and a pleasure to interact with,” says resident Dwayne Lamb, who has been involved in the project since 2015. He says he’s removed more than 2,700 by himself over the years, and calls Olden’s effort “a very worthy pursuit” that “got him hooked” on environmental monitoring. “The project really drove home that everyone on the lake plays a big role in the health of [it] and the wildlife it supports,” he says. 

For the third phase, volunteers stopped removing crayfish to let the lake self-regulate. They gave red swamps a chance to rebound, informing how hard and long an effective removal effort would need to be.

Lamb still traps and sends Olden data, and Olden sends updates to a core group. The rest of the volunteers on Pine Lake operate like a sleeper cell waiting to deploy crayfish-destroying skills. Meanwhile, other lake associations have contacted Olden about setting up similar projects. 

Invasive crayfish discoveries so far

“Now that we have 12 years of data, you can start to better understand more decadal scale changes,” Olden says. Crayfish numbers have been variable, but with multiple generations logged, he’s finally evaluating which variability is natural and what might come from outside factors like the removal effort.

Despite year-to-year variability, there’s been strong consistency in population ratios. Around 2006, Mueller was seeing ratios of about three red swamps to one signal — the first data indicating invasive crayfish could outcompete signals in its natural range. Over the years, the ratio grew to as much as 15:1. Two years into the removal effort, the ratio narrowed to 5:1 and even 2:1 for a few months. "We have seen a 50-percent reduction of the abundance of red swamp crayfish comparing the years before and after the volunteer control effort," Olden says. Since then, “we’ve seen native crayfish popping up in parts of the lake where I've never seen them before… [which means] they're rebounding and spreading back out."

But invasive crayfish have rebounded this year. 

Signals were nowhere to be found during the final sampling trip. Traps either came up empty or full of (mostly male) invaders. “There are still some months when I come out that I don't catch a single signal crayfish,” Olden says. “It's not uncommon. But it's less common now than it was before.” 

Knowing red swamp reproduce more often during mild winters like the one Washington had a few winters ago, Olden can account for natural fluctuation and the removal effort to say that winter likely helped the invasives gain ground.

Mild winters “are a fact of climate change,” Olden says. “[No matter] how strong the volunteer effort is, sometimes the environment can just trump over that. You can't fight against their ecology. And that's why invasive species management has to be for the long term, and timed with other environmental factors.”

Over time, he’ll identify whether the removal effort created lasting impacts. If not, “that [would] basically tell us that we’ve got to remove more and you can't just take your foot off the gas,” Olden says. 

Olden pulls out a bucket holding two signals he caught before we set out in the canoe: a giant, 5-year-old “grandpa” at least 6 inches long, and a 2-inch-long baby. Their shells are smooth, and mottled blue-green like river rocks. They have attention-getting white  splotches — “signals” — on their claws.

Catching a baby “hasn’t happened in a long time." 

“It means they're still reproducing … which is a great sign,” he says. “I've never been so happy to see a small crayfish. Look at how cute that is!”

In working with volunteers and getting a sense of management challenges, Olden says he stopped thinking “purely as a scientist” and started caring about impacts. 

“It [proves it’s] not hopeless when an invasive species comes in,” he says.

Olden can’t hide his affection for his captives, even the the invasive ones. Earlier, while palming a red swamp crayfish, he scanned the water for a big leafy plant. “I'm going to put him on a nice resting spot,” he said.

Olden, with a sheepish, self-aware grin, sets him on a lily pad just so, like an action figure. 

“There's an inner kid in me. I'm playing with crayfish.” 

Update: We added language to clarify the methods of sampling; that Olden alone sampled during the first phase of the project; and that he didn't give a presentation to community members until 2013. 

Olden says he enjoys his time on the lake. “Other than the slight sound of a plane going by, it's pretty awesome. It's easy to just kind of drift away, if you will, both in your imagination and on the boat.”  (Hannah Weinberger/Crosscut)

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How one scientist enlisted a lakeside community to study (and eat) invasive crayfish

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