We've caught big perch well after dark, when nightfishing deep for rainbows, under a lantern. I'm not saying they all go deep, but we seldom see any small ones while fishing in this manner. Though the rainbows stay deep (we only use the lantern to see our lines) those big perch come right up under the lantern and are seen feeding on fry and zooplankton (daphnia). In most cases, we were anchored in 35-40 feet of water. This was in the heat of the summer. -Jim