In a small saucepan, combine maple syrup, vinegar, lemon juice, mustard, shallot, salt and pepper.
Heat maple syrup mixture to boiling; reduce heat. Simmer uncovered, about 5 minutes, or until syrupy. Remove from heat ; stir in rosemary.
Preheat broiler. Place fish on the greased unheated rack of a broiler pan and brush with half of the glaze. Broil 6-7 inches from heat for 5 minutes. Turn fish over; brush with remaining glaze. Broil for 3 to 5 minutes more, or until fish begins to flake when tested with fork.