Nonnative Fish Species

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Nonnative Fish Species

Nonnative fish distribution and their influence on native fish are not static. While they have not been intentionally stocked since the 1930s, nonnative fish continue to advance into new habitats and hybridize with or displace native fish.

Hybridization of cutthroat trout resulting from rainbow trout range expansion continues to be the greatest threat to the park’s remaining native fish populations in waters outside the Yellowstone River headwaters, Yellowstone Lake, and the Snake River headwaters.

Not all of the movement by nonnative fish in Yellowstone has occurred naturally. Nonnative lake trout, intentionally introduced by managers in 1890 to Lewis and Shoshone lakes, and introduced (possibly intentionally) to Yellowstone Lake in the mid-1980s, first appeared in angler catches in 1994. The lake trout population expanded and, over the following decade, caused a rapid decline in the Yellowstone cutthroat trout population in Yellowstone Lake.

 

 

History At a Glance

• When the park was established, many of its waters were fishless.
• Park waters were stocked with native and nonnative fish until the mid-1950s.
• Stocking changed the ecology of many Yellowstone waters as nonnative fish displaced or interbred with native species.
• By the 1960s, native trout populations were in poor condition and the angling experience had declined.
• By the late 1980s, native trout had recovered in some areas due to restrictions in fish harvest.
• In 2001, fishing regulations changed to require the release of all native fishes caught in park waters.

 

Resources

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Source: Data Store Collection 7797. To search for additional information, visit the Data Store.