Salmonids (family Salmonidae) are native to the cool and cold waters of the Northern Hemisphere. The members of this family may be restricted to fresh water (i.e., resident or non-anadromous) or spend parts of their lives at sea (i.e., anadromous), but none are strictly marine. Salmonids have been introduced into many countries around the world, primarily to provide recreational fishing. Salmonids exhibit a great range of phenotypic (e.g., body shape, coloration, size, and behavior) and genetic

Adaptive variation in salmonid life history is often related to these traits:

Anadromy, the migration between the freshwater (breeding) and oceanic (feeding) habitats. May vary between facultative or partial anadromy, when only a fraction of the population/species migrates to and from the ocean and obligatory anadromy when the entire population/species exhibits a migratory lifestyle.

Freshwater residency, the length of time individuals remain in fresh water rearing as juveniles prior to first ocean migration.

Ocean residency, the length of time individuals spend feeding in the ocean before entering fresh water as mature adults to spawn.

Homing, the ability to return to the natal streams (“home”, i.e. the stream where the fish hatched) for spawning. This is the opposite of straying, when individuals return to non-natal streams for spawning.

Degree of parity, the number of spawning episodes throughout the life cycle. May vary between semelparity when individuals reproduce only once in their lifetime and iteroparity when individuals survive over several reproductive events.

The Salmonidae family includes the “Pacific trouts and salmons” of the genus Oncorhynchus, the Atlantic salmon and brown trout of the genus Salmo, and the “charrs” of the genus Salvelinus.

Oncorhynchus
Pacific salmon are represented by seven different species occurring on both sides of the North Pacific Ocean: the chinook or king salmon (Oncorhynchus tshawytscha), the chum or dog salmon (O. keta), the coho or silver salmon (O. kisutch), the pink or humpback salmon (O. gorbuscha), and the sockeye or red salmon (O. nerka). The masu or yamame salmon (O. masou) and the amago or biwamasu salmon (O. rhodurus) occur only in Asia. These seven species are obligatory anadromous and semelparous: they start life in freshwater streams, migrate to the ocean where they feed and grow, and upon maturation return to the natal stream to reproduce once and then die. On the other hand, “Pacific trouts” are represented by two different species occurring in the Pacific rim of North America: the rainbow trout/steelhead (O. mykiss) and the cutthroat trout (O. clarki). Pacific trouts are facultative anadromous (with anadromous and non-anadromous life history forms), and highly iteroparous. In the anadromous form, the young fish remain in freshwater for one or more years, then migrate to the sea to feed and grow for at least a year before returning to fresh water to reproduce in their natal stream (homing instinct may not be as strong as in Pacific salmons). After breeding they return to sea. Pacific trouts may repeat breeding several times over their lives.

Salmo
The genus Salmo includes two different species occurring on both sides of the North Atlantic Ocean: the Atlantic salmon Salmo salar is predominantly anadromous, but there is also a non-migratory form, called landlocked salmon, Ouananiche, or Sebago salmon (S. s. sebago), iteroparous and with a strong homing tendency. The brown trout S. trutta is facultative anadromous (the migratory form is called sea-run brown trout) and highly iteroparous, with weaker homing than Atlantic salmon. The life cycle of anadromous forms of Salmo parallels that of anadromous Pacific trouts, although Atlantic salmon is, in general, less iteroparous.

Salvelinus
Among members of the genus Salvelinus are the lake trout S. namaykush and the brook trout or brook charr S. fontinalis, which are exclusively native to North America. Lake trout is almost exclusively fluvial or lacustrine, but some populations occasionally may enter salt water. Brook charrs are facultative anadromous, with anadromous and resident forms or populations, highly iteroparous, and with low homing capacity. The life cycle of anadromous forms of Salvelinus is similar to that of anadromous Pacific trouts.

Back