Step 1) Combine soy sauce, pineapple juice, oil, ginger and garlic in shallow dish. Reserve 1/2 cup for later use. Add salmon, turning to coat; cover and let stand 15 minutes.
Step 2) Remove salmon from marinade and discard any remaining marinade. Grill over medium heat, turning once, about 5 minutes on each side, until salmon flakes easily with a fork.
Step 3) While salmon is cooking, transfer reserved 1/2 cup marinade to small saucepan. Bring to a boil over medium-high heat; boil until reduced.
Step 4) Serve salmon fillets, drizzling each with reduced marinade.