Soak 8 wooden skewers in water. Heat grill to medium. Cut the fish into 1 ½-inch cubes.
With a sharp knife or vegetable peeler, remove strips of peel (not the white pith) from 2 lemons. Cut the other 2 lemons into wedges and set aside.
Alternately thread fish cubes and pieces of lemon peel on each skewer. Drizzle with oil and season with ½ teaspoon salt and ¼ teaspoon pepper.
Cook the kebabs, turning frequently, for 10 minutes. Serve with the lemon wedges and fresh chervil.