In a small bowl, mix the maple syrup, soy sauce, garlic, garlic salt, and pepper.
Place salmon in a shallow glass baking dish, and coat with the maple syrup mixture. Cover the dish, and marinate salmon in the refrigerator 30 minutes, turning once.
Preheat oven to 400 degrees F (200 degrees C).
Place the baking dish in the preheated oven, and bake salmon uncovered 20 minutes, or until easily flaked with a fork.