Why do fishes die when taken out of water?
Respiration in fishes takes place using gills.
Gills can only absorb oxygen which is dissolved in water and cannot take oxygen which is present in atmosphere. At the point when the water enters the fish through its mouth, the oxygen is taken inside and carbon dioxide is given out through the gills.
So when the fish is taken out of water, the supply of oxygen is cut down and they cannot breathe for long. That's the reason fishes die when we take them out of water