Place taco seasoning in a large resealable bag; add perch fillets, one at a time, and shake to coat. In a shallow bowl, lightly beat the egg. Combine cornmeal and flour in another shallow bowl. Dip fillets in egg, then coat with cornmeal mixture. Place in a single layer on a plate; refrigerate for 15 minutes.
In a large skillet, heat oil over medium-high heat. Fry fillets for 2-3 minutes on each side or until fish flakes easily with a fork.