The Effects of Drought on Rio Grande Cutthroat Trout: The Role of Stream Flow and Temperature

Increasing temperatures and decreasing precipitation threaten the persistence of the Rio Grande cutthroat trout, the southernmost  subspecies of cutthroat trout, found only in parts of New Mexico and Colorado. This subspecies appears to be more vulnerable to drought than more northern subspecies, because it occupies small and fragmented streams which are at greater risk of drying up during drought. Most notably, in 2002 drought in the Southwest resulted in the loss of 14 different Rio Grande cutthroat trout populations – about 10% of the total population.

 

While it is known that drought is having an effect on Rio Grande cutthroat trout, the specific ways in which individuals and populations are affected by drought remains unclear. In light of worsening drought conditions in the Southwest, the need to identify the specific impacts of drought on the Rio Grande cutthroat trout is only increasing. This project is examining the effects of reduced stream flow and higher stream temperature on Rio Grande cutthroat trout to identify how factors such as the survival of individual fish and the growth rates of entire populations may be changing. Once these effects have been identified, researchers will model the long-term survival of the subspecies under predicted future drought conditions.

 

Although the Rio Grande cutthroat trout is not at immediate risk of extinction according to the U.S. Fish and Wildlife Service, more than half of the remaining populations are considered to be in fair or poor condition. The results of this research will directly inform managers as to the vulnerability of this species to drought and which actions can be taken to increase the survival of Rio Grande cutthroat trout during drought. The results will also be valuable for managers working to protect other southwestern trout species under a changing climate, such as the Gila trout and the Apache trout.