The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.

Salmonids (a family of fish that includes salmon, trout, and char) are a keystone species for both aquatic and terrestrial ecosystems, and can be an early warning indicator of ecosystem health. Salmonids also have strong societal values and contribute enormously to regional economies and Native American cultures. Today, many native salmonid populations are small, highly fragmented, and isolated from genetic exchange, thereby increasing their vulnerability to disturbances due to their limited ability to adapt through migration.



Rising global air temperatures are altering the characteristics of aquatic ecosystems worldwide, including freshwater in the United States. Understanding the vulnerability of aquatic species and habitats to changing conditions is critical for conservation and management of these important natural resources. However, no studies have used existing data to understand the relationships between climate and the survival of salmonid populations to more accurately assess and predict climate effects on freshwater fish species across the entire United States.



This project aimed to use existing fish population and climate data from the recent past (1950 – current) to understand the responses of fish to climate impacts on streams. The project team focused on these main questions: 1) how have stream temperatures and flows been changing over the last 60 years and how do these changes vary across the United States?, 2) how have trout populations responded to these changes?, 3) have invasive species, land use change, and other stressors exacerbated the effects of climate on native trout populations?, and 4) how useful are current management and conservation tools when applied to historical data?