Influence of stream flow patterns on juvenile salmon foraging and growth in southeast Alaska

In the Gulf of Alaska, streams will experience more dramatic low-flow events, interspersed with larger and potentially more frequent high-flow events in the coming decades. Reduced stream flows are likely to occur due to diminished snowpack and intensifying seasonal droughts, while higher flow events are likely to occur with more frequent storms and rain-on-snow events. These changes are likely to influence the growth of juvenile salmon, such as Coho Salmon and Chinook Salmon, that live up to two years in freshwater before migrating to the ocean. Streamflow can influence juvenile salmon growth by altering food availability, water clarity and temperature, and predation risk. 

This study examines how the sequence of high- and low-flow events that a watershed experiences influences foraging and growth conditions for juvenile Coho Salmon. Data collected will help in developing hypotheses of how ongoing and future changes in stream flows in Gulf of Alaska rivers may reshape the trajectories of fish growth. In turn, this will help inform broader-scale studies and future monitoring. This information could also be used to develop salmon life cycle models that link stream flow to population dynamics. Results from this study will allow future modeling to predict how changes in the sequence, magnitude and duration of high and low stream flows may influence the growth patterns (and survival) of juvenile salmon.

This study is occurring in collaboration with researchers at the University of Hawaiʻi, who will be conducting a similar study on the influence of flow regimes on organisms in Hawaiʻi streams. An aspect of this research is aimed at exchanging ideas, sampling techniques, and findings to improve evaluation of the effects of shifting hydrologic patterns in these two regions, which are dominated by steep and short watersheds that are closely connected to adjacent marine environments.