In late Feb or Mar, or if ice hangs until Apr, the perch are moving toward spawning structure. I've had my best luck by moving into the nearest area of weeds off of the deeper areas I caught them in mid winter. The weeds are usually 12 ft or less. I guess they can be caught over woody structure in lakes that have it. Perch dont make nests, they string their egg directly on weeds and dead wood, or whatever they can.
As the weather warms and the ice is beginning to rot, this is my technique, right up until the ice is unsafe.