Rinse the fish under cold running water. Pat dry with paper towels.
In a small saucepan, bring the soy sauce to a boil and boil for 3 minutes, or until reduced by one-third. Remove from the heat.
Place the salmon in a baking dish. Brush the salmon with the soy sauce. Sprinkle with half the ginger.
Bake about 45 minutes, until the temperature in the center reaches 120°F on an instant-read thermometer. Sprinkle with the remaining ginger and serve.