How does Interbreeding Between Non-native Rainbow Trout and Native Westslope Cutthroat Trout Affect Seasonal Growth Rates and Survival in Three Different Streams in Northwestern Montana?

In Progress

Native westslope cutthroat trout (Oncorhynchus clarkii lewisi)is a species of conservation concern throughout its range. This status is primarily driven by habitat loss and fragmentation, climate-related stressors and interactions with non-native species, specifically competition and hybridization (interbreeding) with rainbow trout (Oncorhynchus mykiss). Due to historic stocking of Northwest rivers with rainbow trout, many populations of westslope cutthroat trout are experiencing hybridization with rainbow trout. However, we currently lack the data to understand how rainbow trout hybridization impacts individual and population performance across environmental conditions.

This project seeks a mechanistic understanding of the consequences of rainbow trout hybridization for individual and population performance. We have collected a five-year dataset in each of three populations to understand how rainbow trout admixture affects individual traits such as growth rate, survival and migratory behavior. By monitoring water temperature and streamflow across our study sites, we will gain an understanding of how environmental variation interacts with rainbow trout admixture to positively or negatively affect individual performance traits. Having this mechanistic understanding will enable managers to prioritize populations for conservation and plan management actions under current and projected climate scenarios.