Many native fish, such as bull trout and cutthroat trout, evolved with fire, and their populations are resilient to fire’s effects if their habitat is otherwise unaffected, or if fish from nearby, robust populations have freedom of movement. This resiliency has been reduced in many watersheds because of stream habitat fragmentation and degradation, and the invasion of nonnative fishes such as brook trout and brown trout that tolerate warmer water temperatures. Climate change
may further weaken this resiliency by directly increasing water temperatures and by changing the influence of fire. Thus, forecasting the persistence of native trout undergoing climate change requires an understanding of fire dynamics – including size, distribution, frequency, severity, and the influence of fuels management – and the responses of nonnative fish species.
FFS ecologist Lisa Holsinger, collaborating with researchers at the University of Montana, continues to investigate how a changing climate might affect wildland fire regimes and stream temperatures. Using a landscape fire succession simulation model Fire-BGCv2, a stream temperature model, and a trout growth model, researchers are forecasting potential changes in trout species distributions and productivity in the East Fork Bitterroot River basin in Montana. This basin has a history of large, stand-replacing fires, yet still supports native fish populations in many tributaries so the researchers hope to develop an understanding about those fire and landscape characteristics that pose higher risks for native trout species.