I also catfish in Wi but I don’t use Trotlines. Perch are legal in WI and work great for catfish - live or as cutbait. They catch bigger fish than crawlers do. Here is the language from the WI fishing regulations “Illegal to use gamefish as bait unless they meet any length restriction for the water body you are fishing and are included in your daily bag limit for that species.” Since there isn’t a minimum length for perch on the Mississippi, you can use them. You just can’t use more than 25 a day since that is the daily bag limit. I don’t believe you can trap or net them though. I use a small hook and worms to catch the perch first