1. Combine the mayonnaise, relish, onion, capers, and mustard in a bowl; mix well and reserve.
2. Sprinkle the catfish fillets with the salt and pepper. Spread the flour on a large plate, lightly beat the egg in a bowl, and spread the cornmeal on a separate plate. Working one fillet at a time, dip the catfish first into the flour to lightly coat, shaking off excess; then into the egg; and finally into the cornmeal. Place the fish on a clean plate and repeat with the remaining fillets.
3. Heat 1/4-inch oil in a 14-inch nonstick skillet over medium heat until hot. Add the catfish fillets and cook until golden and cooked through, about 5 minutes per side.
4. To assemble sandwiches, arrange the bottom half of each roll on a plate. Top each with 4 slices tomato, 1/2 cup lettuce, 1 fillet, and 5 pickle chips. Spread cut side of top halves of rolls with tartar sauce and close sandwiches. Serve immediately.
