In contrast to the situation in FW where all animals are osmoregulators, multiple strategies are employed for the con-
trol of salt and water balance in SW organisms. All teleost fish regulate extracellular ionic concentrations much below that
of SW and are thus both osmo- and iono-regulators. All elasmobranch fish maintain osmotic pressure of extracellular fluids
similar to the surroundings but maintain ion concentrations at approximately 50%of SW(the discrepancy made up by organic
osmolytes) and are thus characterized as osmoconformers