What's the difference between a round and flat fish? As the names imply, round fish have a rounded rib cage, have eyes on either side of their head, and swim upright. You'll find flat fish have both eyes on one side of their body, with that side always facing up, and have flat rib cages. You can yield two fillets from a round fish, and four smaller fillets from a flat fish.
Select a round fish that has bright eyes, firm flesh and smells fresh. Ask your fish monger to "dress" the fish, which means they will gut, scale and remove the fins. They may also remove the gills upon request.
Place the fish on a large, clean cutting board and wipe with a paper towel to remove any moisture.
Using a sharp fillet knife, make an incision behind the head and gill plate and behind the fin.
With the knife tip still in the fish, turn the knife so the blade is now facing the tail. Using even, short strokes with the tip of the knife, cut along the top of the fish, allowing your knife to rest on the bones and top fin. As you get closer to the tail, allow the knife to cut straight through, as seen in the photo.
Gently lift the fillet from the tail, exposing the spine and bones. Using the spine as a guide, run the tip of the knife along the bones to release the fillet.
Flip the fish over and repeat on the other side. Fillets can then be cooked immediately, refrigerated for up to one day or frozen up to two weeks.
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