Brackish water consists of river or sea water, which recorded a salt content between 0.1 and 1%. In Anglo-Saxon countries, the salinity can vary between 0.05% and 3%. Brackish water zones occur largely through estuaries into the sea and are mainly inhabited by highly specialized species that demonstrate a high population density there. However, there are species of fish, such as flounder and Hecht, who have developed the ability to survive in brackish water. The brackish water fish include, for example, the kugelfish, some specimens of silver Blatter and scats, the green puffer fish, the humpback pufferfish, tiger fish and archer fish.