Corvina varies in thickness, try to choose a piece that is fairly even from one end to the other. This will make it easier to portion into equal sized pieces and it will guarantee that the cooking rate for all the pieces will be the same.
If you have one piece that is very thin and one piece that is very thick, the thin piece will be cooked through well before the thicker piece. In that case, put the thicker piece of fish in the pan first and let it get a head start on the thinner piece(s).