by Colin Smith
Year two of the Crystal Lake Mixing Project’s rainbow smelt (Osmerus mordax) eradication efforts have officially begun. The project is testing a new method of removing cold water invasive fish from a lake inhabited by warm water tolerant native species.
Essentially, the experiment involves big trampoline-like air bladders that rise and fall through the water column throughout spring and summer. The hypothesis is that this mixing will warm the entire lake and prevent the cold, bottom layer of water from forming in the summer, giving cold water smelt nowhere to go. (Read more about the mechanics of the project here.)
“We wanted to get the mixing system deployed and operational as soon as remnants of the long winter’s ice melted from the lake,” says Center for Limnology research technician, Colin Smith. “The mixing system transfers heat to the lake on an incremental basis, so every day of mixing brings us closer to our goals.”
Last season the experiment exceeded expectations, warming hypolimnetic (usually the cold, bottom layer of the lake) to temperatures of 21 degrees Celsius for 25 days before autumn air temperatures drastically cooled the lake. By comparison, when the waters aren’t being mxied, Crystal Lake’s summer hypolimnetic temperatures don’t rise above 7 degrees C. In addition to the stellar performance of the lake mixing technology (a full order of magnitude more efficient than aeration lake mixing technology), another hypothesis gained some preliminary support.
Called the “thermal stress hypothesis,” the idea is that, basically, the lack of the cold deep waters of the lake will stress smelt so much that they couldn’t survive.
“Around the middle of August 2012 the smelt population began to behave completely differently than has previously been observed in Crystal Lake,” says CFL graduate student and long-time Crystal “crew member,” Zach Lawson. Smelt were congregating at the surface in large numbers and generally moving in unusual patterns. “By the end of September, a significant portion of that population had disappeared. Our preliminary data suggests sixty to ninety percent of the rainbow smelt population expired and we are eager to begin sampling efforts this season to check our estimates.”
(all slideshow pictures courtesy of Gosia Golub, expect final picture, courtesy of Steve Carpenter)
As of May 14th this year, lake mixing has begun. The hard work of the crew, including the generous contributions of volunteers Gosia Golub and Jill Marzella, enabled the group to finish assembly and deployment by the end of last weekend. The team worked non-stop for twelve-hour days on both Saturday and Sunday in the freezing wind and falling snow.
“By the end of operations we were in a position to conduct some initial testing and, a few days later, press the start button on the mixing system,” says Smith. “We are excited to observe how the smelt population responds this year as well as how Crystal Lake’s ecosystem responds in general.” Hopefully it’ll mean a lot fewer smelt and a lot more perch and walleye. To quote Crystal crew member, Page Mieritz, “Let the mixing begin!”
Watch the waters warm in Crystal Lake and get project updates here. (crystallakemixing.com)