Western Exotics (TU CSI)

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With all of the emphasis in recent years on native trout, we sometimes lose focus on how wonderful a wild trout stream holding browns, brookies, or rainbows can be.  No they’re not native (they’re exotic, meaning these species originated elsewhere).  But they’re well adapted to where they are, and in many cases their history extends over 125 years. 

Recognizing that preserving cold water resources is important, the TU Conservation Success Index has generated a series of KMLs covering virtually the entire Mountain West. These include some of the most famous trout streams in the world, attracting thousands of anglers every year. 

The TU CSI color codes basins for habitat quality (from high to low): blue, green, yellow, orange, red.  These don’t discriminate for specific species.  For example, cutthroat trout might be extirpated from a basin not because the habitat is poor, but because the native trout have been out competed by exotics.  Such a basin might be coded red or brown for cutthroat trout, but be rated much higher (yellow, green, even blue) for wild trout in general.

These TU basin data are often best used in combination with other resources on this site (such as cold water stream data).  You’ll find them in the download system in the “Natives” section, under the “Exotics” category.


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