Good or bad, they’re everywhere.
Introductions of rainbow trout have caused the extinction of many species and are one of the primary reasons that inland sub-species of cutthroat in the western US have declined, or in some cases become entirely extinct.
Rainbow Trout © Ken Cole
The Yellowfin, Waha Lake, and Alvord cutthroats, of Colarado Idaho, and Oregon respectively, have entirely disappeared due to the introduction of non-native rainbows which have hybridized them out of existence. Some subspecies only occupy tiny portions of their historic range for the same reason.
Brook trout in the eastern US are being displaced by rainbows in some places because they can inhabit warmer waters.
There are, however, the westslope and coastal cutthroat sub-species which co-exist naturally with rainbows.
Rainbows consist of several sup-species and are native to the rivers and lakes which flow into the Pacific Ocean from Russia to Mexico. They also inhabit some inland closed basins in California and Oregon where they became established when a stream or river changed course through a process called headwater transfer or when a river’s flow was insufficient to fill the basin and flow into the neighboring one.
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