Brook Trout Populations Are Different in Neighboring Streams Due to Climate Impacts

The abundance of brook trout in the Great Smoky Mountains National Park varies from stream to stream, and this variation is due partly to differences in temperature and flow patterns. This study highlights how the impacts of climate change can vary within even small geographic areas. 

Brook trout are native to the eastern part of North America, and are the only trout species native to the Smoky Mountains. They are cold-water fish that spawn during the fall and hatch in the late winter to early spring, which makes them especially sensitive to higher water temperatures and water flow extremes like with droughts (low flow) and floods (high flow).

The populations of brook trout are declining and high rates of mortality have been recorded due to environmental stressors like high summer temperatures and high winter stream flows, which can dislodge trout eggs and newborns from the stream bed. Being both an important game and ecologically significant species, it is critical to understand how future climate effects may impact this species. 

Researchers in this study analyzed long-term data sets on temperature, stream flow, and trout populations in the Great Smoky Mountains National Park to see how and where numbers changed over time. They then developed a statistical method to understand differences in the number of trout between nearby streams.

The study found that more rainfall helped offset the harmful effects of hot summers. They also found that while high winter flows decreased the number of newborns in some streams, that wasn’t the case everywhere. Some streams had cooler temperatures with consistent flow, and so were better places for brook trout to survive to maturity.

“Natural resources management agencies invest a lot of time and effort in maintaining native fish populations,” says Yoichiro Kanno, co-author of the study. “Our results show that the brook trout population in some streams are more vulnerable to climate change than other streams, showing that prioritizing streams for conservation is important to use limited resources efficiently.” 

This study can help managers and agencies make decisions about restoration efforts for particular streams. Future research could add more nuanced variables to this statistical method by incorporating more features of the landscape, helping to further understand and project population variations between streams.

The paper, “Regularized latent trajectory models for spatio-temporal population dynamics” was published in the Journal of Agricultural, Biological, and Environmental Statistics in April 2024. This paper was co-authored by Xinyi Lu from the Colorado Cooperative Fish and Wildlife Research Unit, George P. Valentine from Colorado State University, Matt A. Kulp from the National Park Service at the Great Smoky Mountains National Park, and Melvin B. Hooten from The University of Texas at Austin.

This research was supported by the U.S. Geological Survey’s Southeast Climate Adaptation Science Center Cooperative Agreement No. G21AC1005.

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