1. Prepare grill for indirect grilling. If using a gas grill, heat one side to medium-high and leave one side with no heat. If using a charcoal grill, arrange hot coals on either side of charcoal grate, leaving an empty space in the middle.
2. Combine first 7 ingredients, stirring until well blended. Spread mustard mixture over fish; let stand 15 minutes.
3. Carefully remove grill rack. Place a disposable aluminum foil pan on unheated part of grill. Carefully return grill rack to grill. Place fish, skin side down, on grill rack over unheated part. Close lid; grill 30 minutes or until fish flakes easily when tested with a fork or until desired degree of doneness. Remove fish from grill by inserting a spatula between skin and fish. Discard skin.