Preheat the oven to 450°F Lightly spray a baking sheet with non-stick cooking spray. Arrange the potato wedges on one side, leaving enough room for the fillets, and spray them with the cooking spray. Bake in the preheated oven for 25 minutes, or until golden brown and tender.
While the potatoes are baking, combine the flour, bread crumbs, and pepper in a shallow bowl.
In another shallow bowl lightly beat the egg white. Dip the fish fillets in the egg white, then coat both sides with the flour mixture. Transfer to the baking sheet, alongside the potatoes, and continue to cook for 10 minutes more, or until the fillets are crisp and browned.
Combine all the ingredients for the tartar sauce in a small bowl and mix well. Serve 1 tablespoon on each fish fillet.