Without any context, Zach Lawson’s current endeavor seems downright morbid.
Lawson has spent the past two and a half years working on a project that, should things go according to plan, will kill thousands upon thousands of fish in a northern Wisconsin lake.
“The idea is to extirpate the entire population,” he said.
Some background: Lawson (BS’10, Zoology, Biological Aspects of Conservation and Geography) is a research technician with the Center for Limnology in the University of Wisconsin-Madison College of Letters & Science. He’s worked full-time out of the Center’s Trout Lake Research Station near the small town of Boulder Junction in Vilas County since 2010.
Specifically, Lawson is the point person for the Crystal Lake Mixing Project, an experiment aimed at eradicating rainbow smelt, an invasive fish species, from the lake.
Crystal Lake, which is one of the more than 2,500 lakes within 50 kilometers of the Trout Lake station, was invaded by rainbow smelt in the early 1980s.
Rainbow smelt aren’t big by any means – generally seven to nine inches long – but they feast on the young, small fish of other species, including such favorites of Wisconsin fishermen as walleyes and perch. The problematic smelt – whose scientific name, Osmerus mordax, is Greek for odorous and biting – have invaded around 25 lakes in Wisconsin, forcing managers to restock lakes.
“They’re nasty,” said Jake Vander Zanden, associate professor in the Center for Limnology and the Department of Zoology and the principal investigator on the Crystal Lake Mixing Project.
The usual tactic for eliminating an invasive population from a lake is a scorched-earth policy: Rotenone, a chemical, is added to the water to decimate anything with gills. Then, native species are added back into the environment.
The idea behind the Crystal Lake project is to test a decidedly more selective strategy.
Rainbow smelt require a cold-water habitat, and rely on the thermal stratification of lakes – while the water near the surface is warm, the bottom is much cooler – to survive in the summer. With a little help from the College of Engineering, CFL scientists are literally mixing Crystal Lake to establish a uniform temperature throughout the lake. This destroys the smelt’s cold-water haven.
Crystal Lake is an ideal candidate because the CFL has extensively studied it over the past 30-plus years, compiling loads of data that provides a context for the experiment. Crystal Lake also floods into larger lakes such as Big Musky and Trout, so there’s a risk of rainbow smelt spreading further.
Mixing a lake is no simple task, which is where the engineers come in.
Jordan Read, who recently completed his Ph.D. in civil and environmental engineering, designed a device called a Gradual Entrainment Lake Inverter (GELI), a large trampoline-like object that moves up and down to mix the water. Lawson and the rest of the project team have used six GELIs to mix Crystal Lake since the ice melted in the spring and have succeeded in creating a near-uniform temperature in the lake.
And they’re starting to see the fruits of their labor. Over the course of the summer, Lawson said, the smelt have begun congregating in one area of the lake. In recent weeks, some have begun dying and floating to the surface.
“We’re at a point where they’re acting really, really odd,” said Lawson, who noted that the team has observed population shifts in zooplankton species in the lake, as well as changes in the spatial distribution of various species.
Technically, Lawson oversees the ecosystem’s response to the massive manipulation, but the project is “kind of an all-hands-on-deck effort” and he’s also assisted with design, testing, deployment and maintenance of the GELI system.
Though he’ll begin work on a master’s degree in limnology and marine sciences this fall, he’s still planning on maintaining close involvement with the project. He certainly doesn’t want to miss out on a potential breakthrough.
“We feel like we’re kind of at the breaking point where something big is going to happen,” he said. “We’re either going to learn something really, really big about cold-water species and their ability to cope with increased temperature or we’re going to be pretty successful in this eradication attempt.”