How do fish breathe

The striped bass breathes by taking in water through its mouth and passing it through its gills and out under its gill covers. The gills are so constructed that they can extract oxygen which is dissolved in the water and throw off carbon dioxide into it.

Several groups of fishes also have accessory breathing organs which enable them to breathe in directly the air above the surface. Such species often live in stagnant or warm water, where the amount of dissolved oxygen is low and that of asphyxiating carbon dioxide is high. Among these fishes are ones which have become completely dependent on their accessory breathing organs and drown if kept too long under water.