In 2021, a group of conservation organizations estimated that one-third of the world's freshwater fish species were at risk of extinction. The critically endangered Mekong giant catfish Common warmwater fish include catfish, largemouth bass, bluegill, crappies, and many other species from the family Centrarchidae.
Warmwater fish can survive cold winter temperatures in northern climates, but thrive in warmer water. Warmwater fish species can survive in a wide range of conditions, preferring a water temperature around 80 ☏ (27 ☌). Common coolwater species include muskellunge, northern pike, walleye, and yellow perch. They are found throughout North America except for the southern portions of the United States. Common coldwater fish include brook trout, rainbow trout, and brown trout.Ĭoolwater fish species prefer water temperature between the coldwater and the long warmwater species, around 60 to 80 ☏ (16–27 ☌). In North America, air temperatures that result in sufficiently cold water temperatures are found in the northern United States, Canada, and in the southern United States at high elevation. Coldwater Ĭoldwater fish species survive in the coldest temperatures, preferring a water temperature of 50 to 60 ☏ (10–16 ☌). The water temperature affects the amount of oxygen available as cold water contains more oxygen than warm water. Both eels, anadromous salmoniform fish and the sea lamprey have different tolerances in salinity in different stages of their lives.Ĭlassification in the United States Īmong fishers in the United States, freshwater fish species are usually classified by the water temperature in which they survive. Many species solve this problem by associating different habitats with different stages of life.
Species migrating between marine and fresh waters need adaptations for both environments when in salt water they need to keep the bodily salt concentration on a level lower than the surroundings, and vice versa. Some other kinds of fish are, on the contrary, born in salt water, but live most of or parts of their adult lives in fresh water for instance the eels. These are known as anadromous fish, and include, for instance, salmon, trout, sea lamprey and three-spined stickleback. Many species of fish do reproduce in freshwater, but spend most of their adult lives in the sea. Sturgeons are found both in anadromous and fresh water stationary forms