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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

Rio Grande cutthroat trout

Duration

July 2015 - December 2019

Narrative

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.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. We are working closely with USGS (National Wildlife and Climate Adaptation Science Center), US Forest Service (Santa Fe, Carson), and the New Mexico Department of Game and Fish.

Research Products and Activities

Presentations

  • Flynn, L.M., B.M. Huntsman, C.A. Caldwell, and A.J. Lynch. 2018. Effects of biotic and abiotic factors on the specific growth rates of Rio Grande cutthroat trout, Oncorhynchus clarkii virginalis. Western Division of the American Fisheries Society Annual Meeting. Anchorage, Alaska.
  • Huntsman, B.M., Caldwell, C.A., Lynch, A.J., and Abadi, F. 2018. Rio Grande Cutthroat Trout population dynamics and persistence along a temperature and precipitation gradient. American Fisheries Society Annual Meeting, Atlantic City, New Jersey, August 20-24, 2018.
 

Current Staff

Federal Staff: 100

Masters Students: 237

Phd Students: 155

Post Docs: 56

University Staff: 246

5 Year Summary

Students graduated: 714

Scientific Publications: 1979

Presentations: 4410

 

Personnel

Funding Agencies

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

Links

Cooperative Research Units Program Headquarters Cooperators

  1. U.S. Geological Survey