US Long-Term Ecological Research Network

University of Wisconsin-Madison researchers are conducting a whole-lake mixing experiment on Crystal Lake (Vilas County, WI) to eradicate an invasive fish from the lake. Rainbow smelt invaded Crystal Lake in the early 1980s, and a sharp decline in native yellow perch populations followed shortly thereafter. To specifically target this invasive for removal from the lake, researchers are taking advantage of the smelt's need for cold water habitat in a lake with no other cold water fishes. The Crystal Lake Mixing scientists will experimentally mix the lake to remove this cold water habitat, stressing the rainbow smelt beyond the limits of survival.

Crystal Lake is a small clear lake that normally stratifies during the summer months, with bottom water temperatures near 50° and surface water temperatures above 70°F. Rainbow smelt occupy the colder, deeper waters of Crystal Lake, while other fish with warmer water tolerances are found closer to the water surface. Crystal Lake Mixing researchers have been studying the lake for many years, but have recently intensified this effort by introducing new sampling to more effectively monitor fish, aquatic plants, algae, water clarity and other properties of the lake during 2010 and 2011. This broad sampling regime allows the researchers to monitor effects of the mixing experiment on the entire ecosystem and see if the lake can return to pre-invasion conditions after the smelt are removed.

The mixing experiment will begin in June of 2011, with continued mixing and monitoring until 2012. Depending on whether rainbow smelt survivors can be found in the lake, a third year of mixing could take place in 2013 with the goal of completely eliminating the invasive from the lake. Monitoring of Crystal Lake will continue into the future, along with additional efforts to further reduce the spread of this harmful invasive.


Watch REU student Ellen Heyn's movie 'Crystallakemixing' on YouTube