Rainbow smelt

(Osmerus mordax)

In rainbow smelt’s native range of northeastern North America, the species is anadromous, meaning that it normally lives in marine systems, but moves into rivers to spawn. Rainbow smelt were intentionally introduced into Crystal Lake in Michigan almost a century ago, and spread through the upper Great Lakes during the 1920s and 30s. They subsequently dispersed into inland lakes, and now inhabit portions of Mississippi and Hudson Bay drainage systems (Franzin et al. 1994).

Smelt continue to colonize Wisconsin’s inland lakes, and currently occur in at least 25 inland Wisconsin lakes (Mercado Silva et al. 2006). While smelt are capable of dispersing through river networks, smelt in Wisconsin are associated with lakeshore development, indicating an important role for human introductions (Hrabik and Magnuson 1999). There is anecdotal evidence that anglers have intentionally introduced rainbow smelt into northern Wisconsin lakes. Another potential factor is the unintentional introduction of fertilized eggs into lakes while cleaning and processing smelt collected from other lakes.

While rainbow smelt generally prefer deep, unproductive lakes, they can inhabit a wide range of lake types (Evans and Loftus 1987). Mercado-Silva et al. (2006) estimated that over 500 lakes in Wisconsin are suitable for smelt invasion, indicating that there remains great potential for further spread of this invasive fish.

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 et al. 1998). Rainbow smelt predation caused the decline of cisco in Sparkling Lake, WI, while competition with smelt caused the decline of yellow perch in Crystal Lake (Hrabik et al. 1998). In addition, numerous Wisconsin lakes have lost reproducing walleye populations following smelt infestation (Mercado-Silva et al. 2007). Smelt introductions also correspond with increased levels of pollutants such as mercury and PCBs in fish (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.

A recent project at UW-Madison has aimed to control populations of rainbow smelt in Crystal Lake (Vilas County, Wisconsin) using a novel approach. Several large mixing devices called GELIs have been deployed in Crystal Lake in 2012 and 2013. Mixing action of the GELIs cause the depths of the lake to warm – thus the intent is to exceed the thermal limits of rainbow smelt (Gaeta et al. 2012). Results to date indicate that a small number of rainbow smelt have been able to withstand the warm temperatures, indicating that this may not be a viable control strategy for this harmful invasive species.


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. PDF

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 American Journal of Fisheries Management. 14: 65-76. PDF

Gaeta, J. W., J. S. Read, J. F. Kitchell, and S. R. Carpenter. 2012. Eradication via destratification: whole-lake mixing to selectively remove rainbow smelt, a cold-water invasive species. Ecological Applications 22:817-827. PDF

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. PDF

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 two lakes. Canadian Journal of Fisheries and Aquatic Sciences 55: 1364-1371. PDF

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. PDF

Mercado-Silva, N., S. Gilbert, G.G. Sass, B.M. Roth, M.J. Vander Zanden. 2007. Impact of rainbow smelt (Osmerus mordax) invasion on walleye (Sander vitreus) recruitment in Wisconsin lakes. Canadian Journal of Fisheries and Aquatic Sciences 64: 1543-1550. PDF

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