Yes, fish need air, specifically the oxygen present in the air that is dissolved in the water, to survive.
While fish live in water, they cannot use the oxygen that is chemically bound to hydrogen in water molecules (H₂O). They rely on dissolved oxygen, which is oxygen gas (O₂) present in the water. This is analogous to how humans need air, but fish extract oxygen from their aquatic environment.
Here's a breakdown:
- Dissolved Oxygen: Fish breathe dissolved oxygen, not the oxygen that makes up water.
- Gills: Fish use specialized organs called gills to extract dissolved oxygen from the water. Water passes over the gills, and oxygen is transferred into the fish's bloodstream.
- Oxygen Levels: The amount of dissolved oxygen in water can vary due to factors like temperature, salinity, and the presence of aquatic plants. Low dissolved oxygen levels can be harmful or even fatal to fish.
- Aquatic Plants: Just like terrestrial plants, aquatic plants produce oxygen through photosynthesis, which helps to maintain the level of dissolved oxygen in the water.
Therefore, while fish live in water, they are entirely dependent on the air (oxygen) that is dissolved in it for their survival.
