In most bony fishes, the gill openings are covered by a flexible plate called an operculum that protects the gills. Oxygenated water enters through the fish's mouth and is forced over the gills. It exits behind the operculum. The nostrils of most bony fishes have no internal connections with the oral cavity. In some bony fishes such as eels, the nostrils' incurrent and excurrent openings are widely separated.
Most bony fishes have mouths at the front end of the head.
These barbers are used to detect food. Bony fishes have separate incurrent and excurrent nostril openings. Most species of bony fishes are covered with and protected by a called scales. Some bony fishes may have scales only on portions of their body, and some species have no scales. Scales lay head to tail in all bony fishes.