Preheat the oven to 300 degrees . Trim the skin from the edges of the fish. Place the fish between 2 pieces of parchment and pound gently to 1/4-inch thickness.
Place the bread crumbs in a dish. Combine the lemon and orange zests on a board. Chop with the parsley, garlic and anchovy (if using) to form a gremolata. Add to the bread crumbs and work through with your fingers. Season the fish with salt and pepper, then gently press the fish into the bread crumbs to coat thoroughly. In a large skillet, heat a layer of EVOO over medium-high heat.
Arrange the orange slices, arugula and onion on a platter. Top with the oregano and season liberally with salt and pepper. Dress with the lemon juice and a liberal drizzle of EVOO.
Add the fish to the hot skillet and cook in batches for 1 to 2 minutes on each side. Transfer to a rack lined baking sheet and keep warm in the oven as you continue. Serve the fish with the lemon wedges and citrus salad.