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Impacts of Drought on Southwestern Cutthroat Trout: Influences of Changes in Discharge and Stream Temperature on the Persistence of Rio Grande Cutthroat Trout Populations


July 2015 - September 2018


Rio Grande cutthroat trout (RGCT) are the southernmost subspecies of cutthroat trout and currently occupy less than 12% of their historic range. Loss of habitat due to competition and hybridization with introduced trout and habitat alteration has restricted the remaining 122 populations to small (5.8 km median length) isolated habitat patches. A stream temperature and discharge monitoring program also identified that the majority of occupied habitat patches, while currently thermally suitable for the subspecies, have very low summer baseflows (< 1.0 cfs) which restrict fish movement and increases the risk of population extirpation due to stochastic disturbances (i.e., drought). Stream temperature loggers from four of the eight streams reflected thermal profiles that exceeded the ultimate upper incipient lethal temperature for RGCT. The warmest streams on average included two grassland streams (Comanche and Vidal) followed by Cañones and El Rito. A total of 1,762 RGCT, of which 1,201 were PIT tagged, and 515 recaptures were encountered. The fewest number of fish encountered was from Columbine Creek (the only RGCT population sympatric with brown trout) followed by the two grassland study streams (Vidal and Comanche). Population abundance was highest in the deepest stream segments and were inversely related to stream temperature, where the highest number of RGCT were observed in colder streams.


Current Staff

Federal Staff: 101

Masters Students: 236

Phd Students: 160

Post Docs: 58

University Staff: 268

5 Year Summary

Students graduated: 676

Scientific Publications: 1886

Presentations: 4311



Funding Agencies

  • National Climate Change and Wildlife Science Center and Climate Science Centers


Cooperative Research Units Program Headquarters Cooperators

  1. U.S. Geological Survey