Thaw salmon and scallops, if frozen. Cut salmon into 1-inch cubes.

For marinade, combine pineapple juice, lemon juice, tarragon, mustard, and salt. Place salmon and scallops in plastic bag set into a shallow dish. Add marinade; seal bag. Turn fish and scallops to coat well. Chill for 1 to 2 hours, turning once. Meanwhile, in a medium saucepan cook zucchini, covered, in a small amount of boiling water for 3 to 4 minutes or until nearly tender. Drain and cool. Cut sweet pepper into 1-inch pieces.

Remove seafood from bag, reserving marinade. On eight metal skewers alternately thread salmon, scallops, zucchini, sweet pepper, and pineapple. Brush with marinade. Grill on an uncovered grill directly over medium coals for 8 to 12 minutes or until scallops turn opaque and salmon flakes easily when tested with a fork, turning once. Garnish with fresh tarragon, if desired. Makes 4 servings.

Arrange preheated coals around a drip pan in a covered grill. Test for medium heat above pan. Place skewers on grill over drip pan. Cover and grill for 8 to 10 minutes or until scallops turn opaque and salmon flakes easily when tested with a fork.