Gather all the ingredients. You will need 2 bowls for breading the fish. Place fish in one of the bowls and pour milk over the fish.
In the second bowl, mix together the flour, salt, and pepper.
Heat avocado oil in the skillet over medium heat. Once oil is hot (350℉), begin breading fish.
Remove one perch from milk at a time and place it in the flour. Cover perch on all sides and shake off excess flour.
Place the floured fish into the hot skillet and continue breading and placing in skillet until the skillet is full, about 4 butterfly pieces per batch.
Fry fish for about 4 minutes on each side, or until breading is a dark golden color. Place on wire rack or paper towel lined plate and continue with batches until finished. Cooked perch can be kept warm in a 100℉ oven, covered with foil to keep warm while other batches are cooking.