Wisconsin Invaders

Zebra Mussels

Spiny Water Flea

Chinese Mystery Snail

Rusty Crayfish

Rainbow Smelt

Round Goby


Rainbow Smelt (Osmerus mordax)

This anadromous species is native to northern coastal regions of North America. Rainbow smelt were successfully introduced into Crystal Lake in Michigan almost a century ago, and spread through the upper Great Lakes during the 1920s and 30s. From there, they effectively dispersed through inland lakes and rivers, and now occupy portions of Mississippi and Hudson Bay drainages (Franzin and others 1994). Smelt continue to colonize isolated inland lakes, and now occupy at least 24 inland Wisconsin lakes (Becker 1983; Lyons and others 2000). While smelt can disperse through rivers, smelt introductions in Wisconsin are closely associated with lakeshore development, indicating an important role for human introductions (Hrabik and Magnuson 1999). There is anecdotal evidence indicating some anglers have intentionally introduced rainbow smelt into northern Wisconsin lakes. Another likely vector is the unintentional introduction of fertilized eggs into lakes while cleaning and processing smelt collected from other lakes.

Rainbow Smlet Distribution

While rainbow smelt prefer deep, unproductive lakes, they can inhabit lakes spanning a wide range of conditions (Evans and Loftus 1987). Mercado-Silva and others (2006) estimated that > 500 lakes in Wisconsin are candidates for smelt invasion, indicating that there remains great potential for further spread of this invasive. Rainbow smelt have had dramatic negative impacts on important native fish species such as lake whitefish, lake herring, yellow perch and walleye in Wisconsin and elsewhere (Evans and Loftus 1987; Hrabik and others 1998). Rainbow smelt predation was responsible for the decline of cisco in Sparkling Lake, while competition with smelt caused the extirpation of yellow perch in Crystal Lake (Hrabik and others 1998). In addition, numerous lakes in Vilas County have lost reproducing walleye populations following smelt infestation. Smelt introductions also correspond with increased levels of pollutants such as mercury and PCBs in gamefish (Vander Zanden and Rasmussen 1996). Though smelt are a small-sized forage fish, they commonly feed on other fishes, thereby adding an additional link in the food chain and generating greater pollutant biomagnification.

Becker, G.C. 1983. Fishes of Wisconsin. Madison, WI, University of Wisconsin Press.

Evans, D.O. and Loftus, D.H. 1987. Colonization of inland lakes in the Great Lakes region by rainbow smelt, Osmerus mordax: Their freshwater niche and effects on indigenous fishes. Canadian Journal of Fisheries and Aquatic Sciences 44 (Suppl. 2): 249-266.

Franzin, W.G., Barton, B.A., Remnant, R.A., Wain, D.B. and Pagel, S.J. 1994. Range extension, present and potential distribution, and possible effect of rainbow smelt on Hudson Bay drainage waters of Northwestern Ontario, Manitoba, and Minnesota. North Am. J. Fish Manage. 14: 65-76.

Hrabik, T.R. and Magnuson, J.J. 1999. Simulated dispersal of exotic rainbow smelt (Osmerus mordax) in a northern Wisconsin lake district and implications for management. Canadian Journal of Fisheries and Aquatic Sciences 56: 35-42.

Hrabik, T.R., Magnuson, J.J. and McLain, A.S. 1998. Predicting the effects of rainbow smelt on native fishes in small lakes: Evidence from long-term research on tuo lakes. Canadian Journal of

Lyons, J., Cochran, P.A. and Fago, D. 2000. Wisconsin fishes 2000: Status and distribution. Madison, WI, University of Wisconsin Sea Grant Institute.

Mercado-Silva, N., J.D. Olden, J.T. Maxted, T.R. Hrabik, M.J. Vander Zanden. 2006. Forecasting the spread of invasive rainbow smelt in the Laurentian Great Lakes region of North America. Conservation Biology 20: 1740-1749.

Vander Zanden, M.J. and Rasmussen, J.B. 1996. A trophic position model of pelagic food webs: Impact on contaminant bioaccumulation in lake trout. Ecological Monographs 66: 451-477.