Fish and their Respiratory System

A mouthful of water is taken in and the fish closes its mouth. At the same moment, the gill cover shuts to prevent the water from leaving. Fish then use pumping action of the floor of their mouth, together with the rhythmic opening and closing of the operculum, to send a steady stream of water out and over their gills. This pumping action, pushes open the gill covers for the water to then leave the fish’s body. As the water is pushed over the gills by this Built-in pumping action, the oxygen prepared for them in water is removed by their gills and enters its body. Magnificent construction!