You will need to remove the scales from the skin of the fish if you are planning to serve the fish whole or if you have bought a fish that is not already scaled by the fishmonger.
This is a messy job, best done near the sink. Lay the fish dark-side up and hold the tail firmly. Working from tail to head with the back of a chef’s knife, scrape the scales off the fish. Hold the fish by the tail under the cold tap and rinse it thoroughly, washing away the scales by rubbing the skin vigorously with your hands.