Which animals have gills?

Fish have gills. Fish are the gill-bearing aquatic craniate animals that lack limbs with digits. Most fish are ectothermic ("cold-blooded"), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish are abundant in most bodies of water.

They can be found in nearly all aquatic environments, from high mountain streams (e.g., char and gudgeon) to the abyssal and even in depths of the deepest oceans (e.g., gulpers and anglerfish). With 33,600 described species, fish exhibit greater species diversity than any other group of vertebrates.