Fish Physiology: Euryhaline Fishes

The need for ion and water homeostasis is common to all life. For fish, ion and water homeostasis is an especially important challenge because they live in direct contact with water and because of the large variation in the salt content of natural waters (varying by over 5 orders of magnitude). Most fish are stenohaline and are unable to move between freshwater and seawater. Remarkably, some fishes are capable of life in both freshwater and seawater. These euryhaline fishes constitute an esti…