Spiny water flea (Bythotrephes cederstroemi)
The spiny water flea (SWF) is a free-swimming predatory crustacean native to lakes of northern Europe and Asia. This species arrived in North America in ship ballast water, and was first discovered in Lake Huron in 1984. It quickly spread to the other Great Lakes, and has since spread to over 50 inland lakes in Ontario, and numerous lakes in Michigan, Minnesota, New York, Wisconsin, and Ohio by hitchhiking on recreational watercraft (Yan and others 1992; MacIsaac and others 2004). SWF is relatively ineffective at moving from lake to lake by hitchhiking on recreational watercraft. Thus, lakes near the Great Lakes or other invaded lakes are considered most vulnerable. Studies from North America and Europe indicate that SWF tend to inhabit large, deep, clear lakes (MacIsaac and others 2000). Based on this, a large number of lakes in Wisconsin are capable of supporting this invasive species.
The first SWF population in Wisconsin was discovered in 2003 in the Gile Flowage in Iron County. This impoundment was not considered a likely candidate for SWF invasion based on its poor water clarity. On the other hand, this impoundment lies in close proximity to Lake Superior. The location of the Gile Flowage allows it to serve as a stepping stone for SWF to colonize the hundreds of potentially vulnerable lakes of the northern highlands lake district of Wisconsin that offer suitable habitat for SWF (Havel and others 2005). In 2007, the spiny water flea was discovered by the Center for Limnology in Stormy Lake in Vilas County.
SWF can become abundant in lakes and are a voracious predator upon native zooplankton. Their introduction in North American lakes has resulted in dramatic declines in the native zooplankton community (Yan and others 2002). SWF are a preferred prey of large-sized zooplantivorous fishes (Coulas and others 1998), but their long spine inhibits consumption by smaller fishes including juvenile gamefish. The replacement of edible zooplankton species with largely inedible SWF could have negative impacts on small fishes, though these food web interactions are poorly understood at present.
References:
Coulas, R.A., MacIsaac, H.J. and Dunlop, W. 1998. Selective predation on an
introduced zooplankter (Bythotrephes cederstroemi) by lake herring (Coregonus
artedii) in Harp Lake, Ontario. Freshwater Biology 40: 343-355.
Havel, J.E., Lee, C.E. and Vander Zanden, M.J. 2005. Do reservoirs facilitate
invasions into landscapes? BioScience 55: 518-525.
MacIsaac, H.J., Borbely, J.V.M., Muirhead, J.R. and Graniero, P.A. 2004.
Backcasting and forecasting biological invasions of inland lakes. Ecological
Applications 14: 773-783.
MacIsaac, H.J., Ketelaars, H.A.M., Grigorovich, I.A., Ramcharan, C.W. and Yan,
N.D. 2000. Modeling Bythotrephes longimanus invasion in the Great Lakes basin
based on its European distribution. Arch. Hydrobiol. 149: 1-21.
Yan, N.D., Dunlop, W.I., Pawson, T.W. and MacKay, L.E. 1992. Bythotrephes
cederstroemi (Schoedler) in Muskoka lakes: First records of the European invader
in inland lakes in Canada. Canadian Journal of Fisheries and Aquatic Sciences
49: 422-426.
Yan, N.D., Girard, R. and Bourdreau, S. 2002. An introduced invertebrate
predator (Bythotrephes) reduces zooplankton species richness. Ecology Letters 5:
481-485.