 Flatfish are demersal fish ( bottom @-@ feeding fish ) that show a greater degree of asymmetry than any other vertebrates . The larvae are at first bilaterally symmetrical but they undergo metamorphosis during the course of their development , with one eye migrating to the other side of the head , and they simultaneously start swimming on their side . This has the advantage that , when they lie on the seabed , both eyes are on top , giving them a broad field of view . The upper side is usually speckled and mottled for camouflage , while the underside is pale . 
