Fish respond to chemicals and other stressors at intensity levels that are often far below those that can be detected by terrestrial animals (Wendelaar Bonga, 1997). Fish are more sensitive to stressors than many other vertebrates because their physiological homeostasis is intimately bound to and dependant upon the water in the surrounding environment. Disturbance of water and ion homeostasis during stress is due to the very intimate relationship between body fluids in the gills and the ambient water. The high bioavailability of chemicals in water is also a factor. Fish are exposed to pollutants through delicate respiratory surfaces of the gills. Marine fish also drink the saltwater.