Is a fish an animal or mammal?

Indeed, lungfish and coelacanths are closer relatives of tetrapods (such as mammals, birds, amphibians, etc.) than of other fish such as ray-finned fish or sharks, so the last common ancestor of all fish is also an ancestor to tetrapods. read more

Yes, all fish belong to the animal kingdom. However, it depends on what kind of fish you are talking about. Sharks, rays, and skates belong to the Class Chondrichthyes. They have skeletons of cartilage rather than bone. Your typical goldfish, however, would belong in the Osteichthyes class, or bony fish, as they have skeletons of bone. read more

Many types of aquatic animals with common names ending in "fish" are not fish in this sense; examples include shellfish, cuttlefish, starfish, crayfish and jellyfish. In earlier times, even biologists did not make a distinction—sixteenth century natural historians classified also seals, whales, amphibians, crocodiles, even hippopotamuses, as well as a host of aquatic invertebrates, as fish. read more

Animals such as whales, dolphins and porpoise are mammals although they live in the same environment as fish. Mammals cannot filter air out of the water with their lungs, as fish do with their gills. There are two types of fishes - Osteichthyes, or bony fishes, and Chondrichthyes, the cartilaginous fishes. read more