Everything about Freshwater Fish totally explained
Fresh water fish are
fishes living the whole or parts of their lifes in
fresh water, such as
rivers and
lakes with a
salinity on less than 0.05%. These environments differ from marine conditions in many ways; most obvious is the different salinity. To survive fresh water, the fish needs a range of
physiological adaptations in order to keep the ion concentration of the body balanced.
41% of all known species of fish are found in fresh water. This is primarily due to the rapid
speciation the scattered habitats make possible. When dealing with ponds and lakes, one might use the same basic models of speciation as when studying
island biogeography.
Physiology
Fresh water fish differ physiologically from salt water fish in several aspects. Their
gills must be able to diffuse water while simultaneously keeping the salts of the bodily fluids inside.
The scales of the fish also plays a part in the scientific process; fresh water fish that have lost too many scales get a surplus of water diffused in through the skin, causing the fish to die.
Another trait characteristic of fresh water fish are the well developed
kidneys. These have to be large because a lot of water passes through them.
Migrating fishs
Many species of fish do reproduce in fresh water, but spend most of their adult lives in the sea. These are known as
anadromous fish, and include, for instance,
salmon,
trout and
three-spined stickleback. 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.
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. Many species solve this problem by associating different habitats with different stages of life. Both eels, anadromous salmoniform fish and the
sea lamprey have different tolerances in salinity in different stages of their lives.
Sources and references
- Borgstrøm, Reidar & Hansen, Lars Petter (red): Fisk i ferskvann - et samspill mellom bestander, miljø og forvaltning, Landbruksforlaget 2000
- Jonsson, Bror: «Fiskene» i Norges dyr - Fiskene 1, Cappelen 1992
Further Information
Get more info on 'Freshwater Fish'.
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