Sale of gamefish is illegal. Gamefish means anything with a size limit. Since perch don't have a size limit (unlike bass, crappie, trout, etc.) you can sell them and it has been this way for many years. I remember reading in one of the outdoor magazines (probly NY Outdoor News) that DEC has proposed to stop sale of any freshwater fish a few times in the past but it gets shot down every time because of all the bullhead and perch dinners up north. Best thing you can do is keep complaining to DEC and elected officials.