A fish (plural: fish or fishes) is an aquatic, anamniotic, gill-bearing vertebrate animal that has swimming fins and a hard skull, but lacks limbs with digits. Most fish are cold-blooded, meaning their body temperature varies with the surrounding water. However, some large, active swimmers like the great white shark and tuna can maintain a higher core temperature. Many fish can communicate acoustically with each other, particularly during courtship displays.
