The family includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), char, graylings, freshwater whitefishes, taimens and lenoks, all coldwater mid-level predatory fish that inhabit the subarctic and cool temperate waters of the Northern Hemisphere.

Many salmonid species are euryhaline and migrate to the sea or brackish estuaries as soon as they approach adulthood, returning to the upper streams only to reproduce.

Many species of salmonids are thus considered keystone organisms important for both freshwater and terrestrial ecosystems due to the biomass transfer provided by their mass migration from oceanic to inland waterbodies.

Current salmonids comprise three main clades taxonomically treated as subfamilies: Coregoninae (freshwater whitefishes), Thymallinae (graylings), and Salmoninae (trout, salmon, char, taimens and lenoks).

[1][14] Based on the most current evidence, salmonids diverged from the rest of teleost fish no later than 88 million years ago, during the late Cretaceous.

[15][16] This duplication is the fourth of its kind to happen in the evolutionary lineage of the salmonids, with two having occurred commonly to all bony vertebrates, and another specifically in the teleost fishes.

[18] This fossil already displays traits associated with extant salmonids, but as the genome of E. driftwoodensis cannot be sequenced, it cannot be confirmed if polyploidy was present in this animal at this point in time.

Given a lack of earlier transition fossils, and the inability to extract genomic data from specimens other than extant species, the dating of the whole-genome duplication event in salmonids was historically a very broad categorization of times, ranging from 25 to 100 million years in age.

Salvethymus) Oncorhynchus Brachymystax Parahucho Hucho Order Salmoniformes The following table shows results of hybrid crossbreeding combination in Salmonidae.