Salmonidae is a family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of ray-finned fish, the only living family currently placed in the order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Salmoniformes. It includes salmon

Salmon

Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...

, trout

Trout

Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...

, chars

Salvelinus

Salvelinus is a genus of salmonid fish often called char or charr; some species are called "trout". Salvelinus is a member of the Salmoninae subfamily of the Salmonidae family. Charr may be identified by light cream pink or red spots over a darker body. Scales tend to be small, with 115-200 along...

, freshwater whitefish

Freshwater whitefish

The freshwater whitefish are fish of the subfamily Coregoninae in the salmon family Salmonidae. Along with the freshwater whitefish, the Salmonidae includes the freshwater and anadromous trout and salmon species as well as graylings...

es and graylings

Grayling (genus)

Thymallus is a genus of freshwater fish in the salmon family of order Salmoniformes; it is the only genus of subfamily Thymallinae. The type species is T. thymallus, the grayling. The genus's five distinct species are generically called graylings, but without qualification this also refers...

. The Atlantic salmon and trout of genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Salmo

Salmo

Salmo is a genus of fish in the salmon family that includes the familiar species Atlantic salmon and brown trout . The natural distribution of the genus is chiefly European. Only the range of the Atlantic salmon extends to northern North America...

give the family and order their names.

Salmonids have a relatively primitive appearance among the teleost fish, with the pelvic fins being placed far back, and an adipose fin towards the rear of the back. They are slender fish, with rounded scales and a forked tail. Their mouths contain a single row of sharp teeth. Although the smallest species is just 13 centimetres (5.1 in) long as an adult, most are much larger, and the largest can reach 2 metres (6.6 ft).

All salmonids spawn in fresh water, but in many cases, the fish spend most of their life at sea, returning to the rivers only to reproduce. This type of life cycle is described as anadromous

Fish migration

Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...

. They are predators

Predation

In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...

, feeding on small crustaceans, aquatic insects, and smaller fish.

Evolution

Current salmonids arose from three lineages

Lineage (evolution)

An evolutionary lineage is a sequence of species, that form a line of descent, each new species the direct result of speciation from an immediate ancestral species. Lineages are subsets of the evolutionary tree of life. Lineages are often determined by the techniques of molecular systematics.-...

: whitefish (Coregoninae), graylings (Thymallinae), and the char

Salvelinus

Salvelinus is a genus of salmonid fish often called char or charr; some species are called "trout". Salvelinus is a member of the Salmoninae subfamily of the Salmonidae family. Charr may be identified by light cream pink or red spots over a darker body. Scales tend to be small, with 115-200 along...

, trout

Trout

Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...

 and salmons (Salmoninae). Generally, it is accepted that all three lineages share a suite of derived traits indicating a monophyletic

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 group.

Salmonidae first appear in the fossil record in the middle Eocene

Eocene

The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 with the fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 Eosalmo driftwoodensis

Eosalmo

Eosalmo is a genus of extinct salmon which lived during the Eocene epoch. The genus was first described in 1977 from fossils found in lacustrine deposits near Smithers, British Columbia, Canada. Fossils from this genus have also been found at sites in Princeton, British Columbia and Republic,...

first described from fossils found at Driftwood Creek

Driftwood Canyon Provincial Park

Driftwood Canyon Provincial Park is a provincial park in British Columbia, Canada. Driftwood Canyon Provincial Park covers 23 ha of the Bulkley River Valley, on the east side of Driftwood Creek, a tributary of the Bulkley River, 10 km northeast of the town of Smithers. The park is accessible from...

, central British Columbia

British Columbia

British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

. This genus shares traits found in the Salmoninae, whitefish and grayling lineages. Hence, E. driftwoodensis is an archaic salmonid, representing an important stage in salmonid evolution.

A gap appears in the salmonine fossil record after E. driftwoodensis; until the late Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 (~7 m.y.a.) trout-like fossils appear in Idaho

Idaho

Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

, in the Clarkia Lake beds

Clarkia fossil beds

The Clarkia fossil beds is a Miocene lagerstätte located near Clarkia, Idaho.The fossil beds were laid down in a lake roughly 15 million years ago, when a drainage basin was dammed by the flood basalts of the Columbia River Plateau. Narrow and deep, the lake's cold, anoxic water and rapid...

. Several of these species appear to be Oncorhynchus

Oncorhynchus

Oncorhynchus is a genus of fish in the family Salmonidae; it contains the Pacific salmons and Pacific trouts. The name of the genus is derived from the Greek onkos and rynchos , in reference to the hooked jaws of males in the mating season .-Range:Salmon and trout with ranges generally in waters...

—the current genus for Pacific salmon and some trout. The presence of these species so far inland established that Oncorhynchus was not only present in the Pacific drainages before the beginning of the Pliocene

Pliocene

The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

 (~5–6 m.y.a.), but also that rainbow

Rainbow trout

The rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America. The steelhead is a sea run rainbow trout usually returning to freshwater to spawn after 2 to 3 years at sea. In other words, rainbow trout and steelhead trout are the same species....

 and cutthroat trout

Cutthroat trout

The cutthroat trout is a species of freshwater fish in the salmon family of order Salmoniformes. It is one of the many fish species colloquially known as trout...

, and Pacific salmon lineages had diverged before the beginning of the Pliocene. Consequently, the split between Oncorhynchus and Salmo

Salmo

Salmo is a genus of fish in the salmon family that includes the familiar species Atlantic salmon and brown trout . The natural distribution of the genus is chiefly European. Only the range of the Atlantic salmon extends to northern North America...

(Atlantic salmon) must have occurred well before the Pliocene. Suggestions have gone back as far as the early Miocene (~20 m.y.a.).

Classification

Together with the closely related Esociformes

Esociformes

Esociformes is a small order of ray-finned fish, with two families, the Umbridae and the Esocidae . The pikes of genus Esox give the order its name. There are ten species — five in each family....

 (the pikes and related fishes), Osmeriformes

Osmeriformes

Osmeriformes is an order of ray-finned fish that includes the true or freshwater smelts and allies, such as the galaxiids and noodlefishes; they are also collectively called osmeriforms. They belong to the teleost superorder Protacanthopterygii, which also includes pike and salmon, among others...

 (e.g. smelts) and Argentiniformes

Argentiniformes

Argentiniformes is an order of ray-finned fish whose distinctness was recognized only fairly recently. In former times, they were included in the Osmeriformes as suborder Argentinoidei. That term refers only to the suborder of marine smelts and barreleyes in the classification used here, with the...

, the Salmoniformes comprise the superorder

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Protacanthopterygii

Protacanthopterygii

Protacanthopterygii is a ray-finned fish taxon ranked as a superorder of the infraclass Teleostei. They inhabit both marine and freshwater habitat...

.

The Salmonidae (and Salmoniformes) are divided into three subfamilies and around ten genera:

Order Salmoniformes

• Family: Salmonidae
  • Subfamily: Coregoninae
    • Coregonus
      Coregonus
      Coregonus is a diverse genus of fish in the salmon family . The type species is the common whitefish . The Coregonus species are known as whitefishes...
      
      - Whitefishes (70 species)
    • Prosopium
      Prosopium
      Prosopium is a genus of freshwater whitefishes found in North America and parts of eastern Russia. It contains three fairly widespread species: the round whitefish, the pygmy whitefish, and the mountain whitefish. The remaining species, the Bonneville cisco, the Bonneville whitefish, and the Bear...
      
      - round whitefishes (6 species)
    • Stenodus - inconnu (1 species)
  • Subfamily: Thymallinae
    • Thymallus
      Grayling (genus)
      Thymallus is a genus of freshwater fish in the salmon family of order Salmoniformes; it is the only genus of subfamily Thymallinae. The type species is T. thymallus, the grayling. The genus's five distinct species are generically called graylings, but without qualification this also refers...
      
      - Graylings
      Grayling (species)
      The grayling is a species of freshwater fish in the salmon family of order Salmoniformes. It is the type species of its genus. Native to the Palearctic ecozone, the grayling is widespread throughout northern Europe, from the United Kingdom and France to the Ural Mountains in Russia...
      
        (12 species)
  • Subfamily: Salmoninae
    • Brachymystax
      Brachymystax
      Lenoks are a genus, Brachymystax, of salmonid fishes. It contains three species living in Mongolia, Siberia, the far East of Russia, Northern China, the Sea of Japan and South Korea....
      
      - lenoks (3 species)
    • Hucho
      Hucho
      Hucho is a genus of salmonids.There are five species in the genus Hucho, and all are native exclusively to Asia with the exception of Hucho hucho, the Huchen trout or the Danube salmon, and Hucho taimen the taimen. Hucho taimen is extinct from Europe and now only lives in Mongolia and Russia...
      
      (5 species)
    • Oncorhynchus
      Oncorhynchus
      Oncorhynchus is a genus of fish in the family Salmonidae; it contains the Pacific salmons and Pacific trouts. The name of the genus is derived from the Greek onkos and rynchos , in reference to the hooked jaws of males in the mating season .-Range:Salmon and trout with ranges generally in waters...
      
      - Pacific salmon
      Salmon
      Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
      
       and trout
      Trout
      Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
      
       (14 species)
    • Salmo
      Salmo
      Salmo is a genus of fish in the salmon family that includes the familiar species Atlantic salmon and brown trout . The natural distribution of the genus is chiefly European. Only the range of the Atlantic salmon extends to northern North America...
      
      - Atlantic salmon and trout (29 species)
    • Salvelinus
      Salvelinus
      Salvelinus is a genus of salmonid fish often called char or charr; some species are called "trout". Salvelinus is a member of the Salmoninae subfamily of the Salmonidae family. Charr may be identified by light cream pink or red spots over a darker body. Scales tend to be small, with 115-200 along...
      
      - Char and trout (e.g. Brook trout
      Brook trout
      The brook trout, Salvelinus fontinalis, is a species of fish in the salmon family of order Salmoniformes. In many parts of its range, it is known as the speckled trout or squaretail. A potamodromous population in Lake Superior are known as coaster trout or, simply, as coasters...
      
      , Lake trout
      Lake trout
      Lake trout is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, lake char , touladi, togue, and grey trout. In Lake Superior, they can also be variously known as siscowet, paperbellies and leans...
      
      ) (49 species)
    • Salvethymus (1 species)
    • Acantholingua (1 species)