Invasive species, climate change and habitat loss are some of the leading factors contributing to the extinction of native species worldwide. Native plants and animals in northwestern Montana are especially vulnerable to these pressures, where regional temperatures are warming at twice the global average, and invasive trout are abundant as a result of historical stocking for recreational fishing. In this region of the United States and Canadian Rocky Mountains, hybridization from invasive rainbow trout is the leading threat to the persistence of native westslope cutthroat trout populations. If left unchecked, the geographic spread of rainbow trout and their invasive hybridization could lead to the genetic extinction of native cutthroat trout populations.

Since the 1980s, Montana fisheries managers have been collecting genetic samples from wild populations to document the geographic spread of rainbow trout and their hybridization with cutthroat trout. This has resulted in a dataset of nearly 10,000 individuals sampled over four decades from more than 80 distinct sites, painting a clear picture of the spread of rainbow trout throughout northwestern Montana. Despite the availability of this impressive dataset, no one has synthesized this information for use in proactive management to conserve native cutthroat trout, until now.

For this project, Jared will compile all of the data that demonstrate changes in the genetic composition of native cutthroat populations resulting from hybridization with invasive rainbow trout. Alongside this information, Jared will analyze environmental data to identify the climatic and habitat factors that seem to be facilitating the spread of rainbow trout. Jared will also use a program that simulates individual fish movements to help identify evolutionary or ecological factors that might be associated with the spread of rainbow trout.

Conserving native trout populations is one of Montana Fish, Wildlife & Park’s main priorities. Through analyzing time-series genetic data along with projected future climate change data, Jared will work with fisheries managers to identify at-risk populations that don’t yet have rainbow trout but are near the front of the wave of the invasion. This information can be used to identify sentinel streams under climate change, indicating the geographic areas rainbow trout are newly colonizing. Managers can focus monitoring efforts in these areas and physically stop the spread of rainbow trout by installing in-stream barriers to preserve native westslope cutthroat trout populations.