The Michigan Department of Natural Resources says that the rainbow trout are:
Native to the Pacific watershed, rainbow trout came to Michigan when eggs were imported from California in 1876. First stocked in the Au Sable River, then four years later in the Lake Michigan watershed, rainbows can now be found in all corners of the state. Large specimens that inhabit the Great Lakes but travel inland to spawn in streams have come to be called steelhead.
Young rainbow trout first eat waterfleas and then add aquatic (water) insects, like caddisflies, mayflies, and midges, to their diet. As they grow larger they include smallfish, but continue to consume larval and adult insects.
Like any trout, stream rainbows can be caught by a variety of techniques; live bait, artificial lures and flies all produce. In large lakes, rainbows can be caught by trolling or by fishing with bait or jigging through the ice in winter. Though most commonly associated with clear-water lakes in northern Michigan, rainbow trout have been successfully stocked into a number of southern Michigan lakes as well, where they provide a unique fishery. Fishing after dark at the thermocline — the depth at which there is a major change in temperature — with live bait, salmon eggs or corn is the principle technique.