Looks like an atlantic salmon to me - those "peacock spots" kind of give it away. But it could be a brown trout - atlantic salmon and brown trout are fairly closely related and I have seen brown's of that size and brightness - pictures of them anyway. Brown trout would be a common catch in Lake Michigan - the only way an atlantic salmon could get up there is through the locks, but along with lampreys and alewives that's certainly possible. Sure not any kind of pacific salmon or steelhead.