Besides basic anatomical and physiological features common to all fishes,
due to the aquatic environment they share, there are some very significant differences.
Such differences range from major ones common to all species within each main group,
namely cyclostomes, chondrichthyans and osteichthyans, to more limited ones between
different species within each group. Even the latter can be very significant,
conditioning, for instance, the feeding behavior/strategy of a given species or its
reproductive ability. Some of the main anatomical and physiological features of the
different fishes are briefly reviewed, since a good knowledge of such features is crucial
to understand the behavior of each species in the wild and/or to assure the most correct
management of its populations either in captivity or in the wild.
Keywords: Anatomy, Chondrichthyans, Cyclostomes, Osteichthyans, Physiology.