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Title: Greenback cutthroat trout (Oncorhynchus clarkii stomias): A technical conservation assessment

Author: Young, Michael K.;

Date: 2009

Source: Golden, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Region. Online:

Publication Series: Miscellaneous Publication

Description: Greenback cutthroat trout (Oncorhynchus clarkii stomias) was once presumably distributed throughout the colder waters of the South Platte and Arkansas River basins in Colorado and southeastern Wyoming. Primarily a fluvial species, greenback cutthroat trout may have occupied 10,614 to 13,231 km of streams above 1,800 m in these basins. Nevertheless, the distribution of greenback cutthroat trout has dramatically contracted since the mid-1800's, particularly from lower-elevation sites. Rebounding from a low of two populations occupying a few kilometers of small streams in 1970, populations regarded as greenback cutthroat trout now occupy up to 72 streams and lakes, 23 of which meet criteria for populations to count toward delisting under the Endangered Species Act. The bulk of these populations are found on federal lands, and many in the South Platte River basin are in Rocky Mountain National Park. Recent genetic evaluations, however, indicate that many populations considered historical remnants of greenback cutthroat trout may be Colorado River cutthroat trout. Individuals of both taxa were often mixed to develop recovery broodstocks, so the number of non-introgressed wild populations of greenback cutthroat trout is uncertain.

Keywords: greenback cutthroat trout, Oncorhynchus clarkii stomias

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Young, Michael K. 2009. Greenback cutthroat trout (Oncorhynchus clarkii stomias): A technical conservation assessment. Golden, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Region. Online:


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