Fish keep water moving over their gills?

Fish breathe by taking water into their mouths and passing it over their gills, which are located on either side of their heads. The gills are made up of thin filaments that are covered in tiny blood vessels. As the water passes over the gills, oxygen from the water diffuses into the blood vessels, while carbon dioxide from the blood diffuses into the water. This process of gas exchange is essential for fish to breathe.

The movement of water over the gills is created by the fish's mouth and operculum. The mouth opens and closes, drawing water into the mouth and then forcing it out through the operculum. The operculum is a flap of skin that covers the gills and helps to direct the flow of water.

Some fish, such as sharks and rays, have spiracles, which are small openings near their eyes that help to draw water into the mouth. Other fish, such as eels and lampreys, have a single nostril that they use to draw water into their mouths.

The rate at which fish breathe varies depending on the species of fish and the water temperature. In general, fish breathe more rapidly in warm water than in cold water. This is because the oxygen content of water decreases as the water temperature increases.

Fish need to keep water moving over their gills in order to breathe. If the water flow is interrupted, the fish will suffocate. This is why it is important to keep aquarium filters clean and to ensure that there is adequate water flow in ponds and other bodies of water where fish live.