Cutthroat trout face upstream swim against climate change
May 12, 2013
Colorado’s cutthroat trout live life on the edges, at high elevations and in isolated pockets other trout haven’t been able to reach. It appears to have toughened them up, according to a recent study looking at climate change’s impact on the species.
Rising water temperatures, the Colorado State University study concludes, aren’t impacting the indigenous fish like some of its non-native brothers.
Results of the study, which included six streams in Summit County, indicate that the hardy fish may be less susceptible to increases in water temperature than other trout.
Researchers James Roberts and Kurt Fausch are suggesting this may be because cutthroat trout have already sought refuge in short, high-altitude streams, above the barriers that keep out non-native brook, rainbow and brown trout.
Although isolated havens of cool-water habitat could help native trout survive future temperature increases, they still face peril in the event of a drought, fire or hard freeze because they don’t have the expansive habitat larger fish populations rely on to survive.
“We had to take into account that these populations are isolated,” Roberts said. “Because they live in small portions of rivers and streams, just one disturbance event could extirpate an entire population.”
Cutthroat trout are also more prone to genetic risks caused by inbreeding because of their habitat restrictions, scientists said.
With only 14 percent of original habitat remaining, the study found that 63 percent of the remaining populations will be at some risk of decline or extinction by 2080.
Scientists are optimistic their findings can have a positive impact on conservation efforts for native trout populations, including those in Summit County, because it is the first ever of its kind.
“The complexity and depth of this study has allowed us to sharpen our focus and help managers create sustainable solutions for this iconic native fish species,” Roberts said. “Our hope is that this research will empower land managers with the tools and information needed to make a significant impact on the conservation of native Colorado River cutthroat trout for generations to come.”
Prior to this research, Fausch was involved with studies focused on finding the potential effects climate change has on both native and non-native trout populations throughout the Rocky Mountain West.
“What is predicted for the West is that we’ll have more rain and less snow. The snow that does fall will do so at higher elevations and will melt sooner,” Fausch explained.
Fish, as a result, will face low stream flows that will dry out more quickly, he said.
Fausch brought in his colleague Roberts to take a closer look at Colorado’s native trout populations. For the past few years, they have been able to focus on more than 300 individual fragments of rivers and streams where pure cutthroat trout populations still exist.
Roberts developed a sophisticated model to predict future stream temperatures based on the latest information about future air temperatures and stream flows under climate change. It also incorporates variables of latitude, slope and elevation.
This work could help wildlife managers plan their restoration efforts on a stream-by-stream basis by determining which native populations can, or cannot, be saved.
“The outcome of this research is that we now have a targeted tool to help land managers plan efficient and strategic habitat restoration to reduce these risks,” Fausch said. “In many other cases, managers may be able to do little for native trout as the climate changes and makes streams too warm for their survival.”