Combine 4 cups water and rice in a rice cooker and follow manufacturer's instructions for sticky rice, 20 to 30 minutes.
Place salmon in a large saucepan and add enough water to almost cover; season water with salt. Bring water to a simmer over medium heat; spoon hot water over salmon. Cover saucepan and simmer until salmon flakes easily with a fork, about 15 minutes. Remove salmon from saucepan and flake using a fork and spoon.
Spoon rice into bowls and top with salmon. Sprinkle tobiko and green onions over the top.