Rainbow smelt are an invasive fish species that was first detected in the Laurentian Great Lakes in the 1920’s and have since spread to numerous inland lakes. As of 2005, rainbow smelt have invaded 24 inland Wisconsin lakes and have the potential to spread to many more. In Wisconsin’s Northern Highland Lake District, rainbow smelt have been associated with several negative impacts on lake food webs. For instance, rainbow smelt have been associated with shifts in zooplankton community structure, reductions in yellow perch densities, extirpation of ciscoes, and walleye recruitment failure.
A team of LTER researchers is performing a whole-lake thermal manipulation to eradicate rainbow smelt in Crystal Lake, Vilas County. Adult rainbow smelt require cooler waters than most native fishes and, as a result, occupy the deeper, colder parts of the lake. By experimentally mixing Crystal Lake throughout the summer via common bubblers and experimental gradual entrainment lake inverters (GELIs), we will warm deeper areas of the lake and eliminate the cold-water habitat required by adult rainbow smelt. As a result of the manipulation, we expect adult rainbow smelt to be thermally stressed to the point of starvation, causing mortality. However, we do not expect the manipulation to have significant negative impacts on native yellow perch or walleye in Crystal Lake due to their warmer water temperature tolerances. 
Jordan Read (Civil and Environmental Engineering, UW – Madison) and I have combined empirically based hydrodynamic and bioenergetics models to predict the outcome of proposed manipulation and assess the likelihood of success. Our model results indicate that the experiment should be successful with yearling and adult rainbow smelt being predicted to surpass the lethal limit of seasonal weight loss. However, we will need to repeat the manipulation for consecutive years to allow young-of-the-year (Age 0) rainbow smelt to become physiologically susceptible to the manipulation. If our experiment is successful, this technique has the potential to be used as a management tool throughout the region to eradicate this detrimental species.
