the animal population of bodies of water whose salinity is lower than that normally prevailing in the ocean (from 0.3 to 2 percent). Examples of such bodies of water are the freshened waters of the Baltic Sea, Black Sea, Sea of Azov, and Caspian Sea, as well as those parts of seas close to river mouths, estuaries, and lakes (for example, Lake Balkhash). Brackish-water fauna embraces species indigenous to brackish waters and euryhaline forms of marine and freshwater organisms. The composition of the fauna and the numerical ratios of the various species are determined by the current salinity of the water and fluctuations therein throughout the history of the body of water.