Read the regulations. "Perch" traps are only legal in saltwater.
Minnow traps can be used in freshwater, may not be longer than 24", throat cannot be larger than 1 inch X 5 inches. Gear tag required and must be redated every ten days.
Personally I think the whole regulation is silly. What harm would any size be if the opening was kept at 1" X 5"?
That opening on the minnow trap is 1"X3" I do believe! Minnow Trap: May be used to take NONGAME fish only. Trap may not exceed 24 inches in length. The throat may not exceed 1 inch by 3 inches. Gear tag valid for only 10 days must be visibly attached