Scientists at the Great Lakes Indian Fish & Wildlife Commission (GLIFWC) connected the Mille Lacs walleye fisheries decline to spiny water flea and zebra mussels. In the Summer 2017 edition of Mazina'igan- A Chronicle of the Lake Superior Ojibwe they reported,
In 2005, zebra mussels were found in Mille Lacs Lake, which were most likely introduced by hitchhiking on boats and trailers or in bilge water. Similarly, spiny waterflea was introduced in 2009 and again, these organisms were most likely transported by unknowing boaters. These invasive species can compete with and consume native zooplankton (microscopic organisms that age-0 fish eat), which can negatively affect their population size. In fact, by 2012, the native zooplankton population decreased from ~60/liter to less than 20/liter, directly correlating with the increasing number of spiny waterfleas and zebra mussels in the lake.
That's greater than 60% reduction in the base food chain and it only took 6 years to happen on Mille Lacs. The resulting impacts trickled down to the greater community resulting in over $26 million in economic loss as reported by the Mille Lacs County tax assesor.