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Yellowstone cutthroat trout 2001 status assessment (Contains May et al. (2003) report, supporting data, and GIS files. Also contains the May et al. 2007 report on the 2006 assessment update.)

Data Categories istorical distribution
Current distribution
Dates of Data 2001 TO 2001
Data Set Status Complete
Data Set Update Schedule Approximately every 5 years.
Date Data Set Published on StreamNet Data Store 2/9/2005
Project Name & Number
Purpose of Data Set Purpose provided in Abstract
Summary / Abstract The distribution and abundance of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri; YCT) have declined from historical levels over part or all of their l range. For this YCT assessment we used existing information provided by 43 fisheries professionals applied through a consistent methodology to assess the extent of YCT historical range, their current distribution, including genetic status, and evaluated the foreseeable risks to 195 populations designated as conservation populations by management agencies. We estimated that YCT historically occupied about 17,397 miles of habitat in the western U.S. YCT currently occupy an estimated 7,528 miles of historical habitats (43%). Genetic testing has been completed across about 1,880 miles of habitat (25% of occupied habitats), but sample sizes were variable and sample sizes of 25 fish or more (a sample size that likely would detect as little as 1% introgression at alpha = 0.05) made up 27% of the samples. YCT with no evidence of genetic introgression currently occupy about 1,300 stream miles (17%) of habitat. Another 105 miles of currently occupied habitats (1%) contained YCT that were identified as part of a mixed stock where the YCT were not introgressed. We suggest that even though genetic sampling was nonrandom because sampling likely occurred more frequently in YCT populations that appeared non-introgressed, some, if not much, of the habitats currently occupied by YCT with no genetic testing likely support populations that are not introgressed. Approximately 3,000 miles of occupied habitat were identified as containing genetically unaltered YCT based on no record of stocking or by having no hybridizing species present. Much of the habitat currently occupied by YCT was located in designated parks (2%), wilderness areas (19%), and other road-less areas (40%), and almost 70% of habitats currently occupied lie within federally managed lands. A total of 195 separate YCT populations currently occupying 6,346 miles of habitat were designated as conservation populations (84.3% of currently occupied habitat). These conservation populations were spread throughout the historical range, occuring in 35 of the 41 hydrologic units historically occupied by YCT. Most of these conservation populations were judged to be isolets (143 or 73%); however, meta-populations occupied much more of the habitat (5,515 miles or 73%). Of the 195 designated conservation populations, 133 (68%) had at least some component that was tested as genetically unaltered or viewed as being potentially unaltered. Thirty nine populations (20%) consisted of only tested unaltered YCT. More isolet populations were at higher risks due to temporal variability, population size, and isolation than meta-populations, but these isolets were generally at less risk from genetic and disease factors than meta-populations.

This assessment clearly shows that YCT currently occupy significant portions of, and are well distributed across, their historical range. The data suggest that genetically unaltered YCT occupy at least 17% and possibly up to 58% of currently occupied habitats (7 to 25% of historical habitats). Conservation population designations suggest that two different conservation management strategies are needed and being implemented to conserve YCT. One strategy concentrates on preventing introgression, disease and competition risks through isolation of YCT, while the other concentrates on preserving meta-population function and multiple lifehistory strategies by connecting occupied habitats.
Broad Biological Groups Fishes
Taxa Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri)
Location Montana, Idaho, Wyoming
NPCC Subbasins (2001 Subbasins) Outside the Columbia basin: Outside Columbia Basin
Upper Snake: Snake headwaters
Upper Snake: Snake upper
Upper Snake: Snake upper closed basin
Keywords genetics introgression miles historical distribution barriers risks land management impacts range
Lead Person and Organization That Created the Data Set Dawn Anderson
Other Participating Organizations USDA Forest Service (USFS)
Montana Fish, Wildlife & Parks (MFWP)
Montana Cooperative Fishery Research Unit
Idaho Department of Fish and Game (IDFG)
Wyoming Game and Fish Department
Contact Person for Questions About the Data Name:  Dawn Anderson
Position:  Fisheries Database Manager
Organization:  Montana Fish, Wildlife & Parks
Address:  Montana Fish, Wildlife & Parks, Fisheries Division PO Box 200701 1420 E. Sixth Avenue
Helena, MT  59601
Phone:  406-444-3373
email:  Send a note to addressed for dawanderson.
Broad Category of Methods Field
Data Collection Methods Various. Original field data were collected using various methods. Data in this data set were compiled from available data.
File Formats Adobe Acrobat (.pdf)
Microsoft Access 2000 (.mdb)
Shape file (.shp, .shx, .dbf)
Microsoft Word (.doc)
Data structure description See data set files
URL where updated data may be available The most recent Yellowstone cutthroat trout assessment information can be found at The full data set for the 2006 assessment is available from the contact person. A 2007 update was done but the data are not yet available.
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Papers, reports, and presentations that were done under this project. May, B.E., W. Urie, B.B. Shepard, S. Yundt, C. Corsi, K. McDonald, B. Snyder, S. Yekel, and K. Walker. 2003. Range-wide status of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri): 2001.

May, B.E., S. E Albeke, and T. Horton. 2007. Range-wide status assessment for Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri): 2006.
Restrictions or legal prerequisites for accessing and using this data set. No

File Size: 42 MB