For openers, they do not usually need to be turned. The under half of a thin fillet is cooked by a combination of heat penetrating through the upper half of the fish and heat emanating from the hot pan below. A fillet is also delicate, and the act of turning it is likely to break it apart, particularly if the flesh adheres to the grate or pan. To minimize the sticking tendency that can make removing the cooked fish difficult, butter or grease the cooking surface before placing the fish on it.
** Asian Recipes