Crossing the salt barrier

Salinity of water is a stumbling block for the movement of aquatic animals. There are thousands of fish species whose localization in water bodies is strictly restricted to either the sea or freshwater (rivers, lakes, ponds, etc.), or brackish water (where river or lake water mixes with sea water). Only three species known so far have conquered this deadly salt barrier and made crossing it a regular life process. This article gives an indepth account of the processes and strategies that enable them to do so.