Fishes are a class of aquatic vertebrates. Fishes are cold-blooded (with the exception of Tuna and Mackerel family) means they do not have the ability to maintain a constant internal body temperature. Their temperature is highly influenced by outer environment. They are vertebrates, having a backbone. They mainly breathe through their gills and swim with the help of their fins. Dolphins are mammal not fishes. Dolphins are warm blooded.