What else did you stock and at what sizes?
When the weather cools down a bit and the other typical midwestern gamefish start slowing down, try vertical jigging a small jig tipped with a minnow head. Or use a bobber with just a hook and a split shot! your original perch could be HUGE right now (or they could be the 4-6 inchers you are catching, did you watch the perch go in the pond?)

Do you feed your fish? if so the perch are probably HUGE, you just probably catch bluegills before the perch get a chance at your offering.

Good luck and be sure to post the pic of a huge perch you catch in the next couple weeks!