In a small bowl or measuring cup, combine the orange juice, hoisin sauce, soy sauce, sherry and ginger. Mix well. Add the onions. Spray a large, non-stick skillet with vegetable oil spray. Heat over high heat until hot. Add the fish fillets and cook for 1 minute on each side. Add sauce and boil 1 minute. Turn fillets and boil 2 minutes longer. Remove fish to a serving platter. Boil sauce 1 minute longer, until it is reduced and slightly thickened. Pour over fish.
