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Trouts and Salmon (Salmonidae)

There are few families as attractive to fisherman as the salmonids. No other taxa has been so extensively stocked, introduced, researched and genetically altered as this group. In fact, some trout species have been so widely stocked that most don't realize their status as an "exotic". The brown trout (Salmo trutta), for example, is a native to Europe, while the rainbow trout (Oncorhynchus mykiss) is indigenous to the Pacific Northwest. While introductions of these two species have had varying degrees of success, they can now be found throughout the United States.

Figure 1

Figure 1. Family level identifiers. Rainbow trout (Oncorhynchus mykiss).

Family Level Identifiers (see Fig. 1):

Habitat:

Salmonids occupy a variety of habitats, but most require clean, cool water where food is plentiful and dissolved oxygen is high. Many stockings have failed due to water temperatures exceeding 70 F in the summer months. While some salmonids are primarily marine dwelling species (e.g. pacific salmon), all reproduce in freshwater.

Pollution Tolerance:

Like other families, salmonids vary in pollution tolerance. Many species, as previously mentioned, are temperature sensitive. Etnier and Starnes (1993) commented that brook trout (salvelinus fontinalis) do not tolerate maximum water temperatures much higher than 61 F. Consequently, native brook trout populations are confined to streams fed by groundwater, and are susceptible to stressors such as siltation, urbanization and riparian destruction, all of which are known to raise stream temperatures. Another indirect stressor to native trout populations involves the introduction of exotic species, such as the rainbow and brown trout in Tennessee and Northern Georgia, where success of these exotic species has been to the detriment of the native brook trout (Etnier and Starnes 1993). Finally, although some dams have been made "fish friendly", many of these structures still impede highly migratory (and anadromous) salmonids from carrying out essential life migrations.

Use in IBI:

Family Salmonidae is evaluated under Metric 9: Percent Top Carnivores. In the western United States, salmonid juveniles are commonly used in place of darter species in Metric 2: Number and Identity of Darter Species. Occasionally, salmonids are used in place of, or in conjunction with, sunfish, in Metric 3: Number of Sunfish Species.

Table 1. Tolerance designations for selected trouts and salmon.
Species Name Common Name Pollution Tolerance Habitat Disturbance
Coregonus artedi Cisco or Lake Herring M NR
Coregonus clupeaformis Lake Whitefish M NR
Oncorhynchus clarki Cutthroat Trout I NR
Oncorhynchus kisutch Coho Salmon M NR
Oncorhynchus mykiss Rainbow Trout M I
Oncorhynchus tshawytscha Chinook Salmon M NR
Salmo salar Atlantic Salmon M NR
Salmo trutta Brown Trout M I
Salvelinus fontinalis Brook Trout M NR
Salvelinus namaycush Lake Trout M NR
Key
Pollution Tolerance Habitat Disturbance
T = Tolerant T = Tolerant
M = Intermediate MT = Moderately Tolerant
I = Intolerant MI = Moderately Intolerant
NR = No ranking I = Intolerant
  NR = No ranking

Biological Indicators | Aquatic Biodiversity | Statistical Primer

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