Are Fish Cold-Blooded? Understanding Fish Body Temperature in One Article

Fish live in water, so are all fish that live in water cold-blooded?

Most fish are cold-blooded, with the opah being the only exception. The opah is the first warm-blooded fish discovered by humans, also known as the spotted opah or spotted moonfish.

Cold-blooded animals: refers to ectothermic animals, whose body temperature changes with the surrounding temperature, thereby reducing metabolism and lowering the energy lost to resisting cold. All cold-blooded animals are from the class Reptilia, amphibians, fish, and some insects as well.