The Potential Impacts of Climate Change on River Food Webs and Salmon Productivity in Southeast Alaska

Salmon that spawn and rear in Southeast Alaska watersheds are critically important to the region’s economic vitality and cultural identity. An estimated 90% of rural households in Southeast Alaska use salmon. Environmental changes that compromise the ability of these streams to support salmon could have dramatic consequences for the region. In particular, there is concern that climate change could undermine the capacity of the region’s streams to support productive fisheries. As a result, regional stakeholders are interested in identifying some of the potential impacts of climate change on watersheds that support abundant salmon. These stakeholders include federal and state agencies (U.S. Fish and Wildlife Service, U.S. Forest Service, National Park Service, Alaska Department of Fish and Game), native corporations (Sealaska), non-profit entities (Southeast Alaska Watershed Coalition, The Nature Conservancy, Trout Unlimited), and numerous local communities that rely on healthy salmon populations.

 

One of the difficulties in predicting the effects of climate change on stream food webs, however, is the lack of information on the sources and pathways of energy and nutrients that fuel fish production in freshwater habitats. The objective of this study is to quantify trophic linkages and energy flow through the food webs that support salmon production in glacial-, snow-, and rain-fed streams, and in so doing, illuminate the seasonal patterns of energy and nutrient flow that salmon rely on. This is the first study of this extent and focus in Southeast Alaska, where one of the largest fishing industries in the world operates. For Southeast Alaska and beyond, the research will provide a detailed understanding of the freshwater food webs that support productive and resilient fisheries, and how climate change may affect these webs. The work will help managers identify critical food resources for fish by highlighting the important pathways supporting juvenile salmon growth in freshwater. This information will be used in food web models that can inform community adaption and land management in not just Southeast Alaska, but in any region that contains abundant rearing habitat for salmon and where snow and glacier ice melt substantially contribute to streamflow.