Assessing Potential Effects of Climate Change on Pacific Salmon in Southeast Alaska and the Fisheries Implications

As global climate change progresses, temperatures will continue to increase dramatically at higher latitudes. With increased temperatures, glaciers will continue to melt at alarming rates, causing greater volumes of glacial freshwater to enter streams and rivers, changing the temperature and flow dynamics. Additionally, both the frequency and intensity of climate events, such as the El Niño-Southern Oscillation, as well as ambient ocean temperatures, are projected to rise significantly. These climatic changes will have dramatic and multifaceted effects on many environmental and socioecological systems, both at the global and local scale. Southeast Alaska is particularly vulnerable to the effects of climate change since much of the region is glaciated, feeding the region’s streams and lakes, and the socioeconomic structure is highly dependent on natural resources, especially salmon fisheries. Because of this particular vulnerability, my Master’s Thesis focuses on the potential effects of climate change on salmon populations in Southeast Alaska, and how fisheries management in the region can adjust to ensure sustainable catches throughout uncertain futures. To do this, I built a suite of mathematical models and completed a variety of statistical analyses using available data, projections, and estimates from literature. My thesis is structured into an introduction chapter, three body chapters, and a conclusory analysis. In the first body chapter, I derive a simple model of glacial dynamics within the region’s watersheds as a function increasing temperature. In the second body chapter, I present models to estimate four components of stream dynamics: the impacts of rising air temperature and changing glacial dynamics on stream temperature, the influence of changing precipitation and glacial retreat on streamflow rates, the consequences of increasing storm events on mortality events, and effects of variable salmon populations on nutrient flow as well as stream and forest health. In the third body chapter, I build models to inspect the roles of rising ambient sea surface temperature, El Niño-Southern Oscillation, and the Pacific Decadal Oscillation in the survival of migratory adult salmon in the open ocean. In the conclusory chapter, I assess the overall effects on Pacific salmon by integrating the results of the models described in the previous chapters, examining what all of these environmental factors entail for the area’s salmon fisheries, and how the fisheries can adapt or even adopt precautionary management systems. The model results indicate that Pacific salmon are at great risk of the effects of climate change while residing in the region’s streams, especially from the increased frequency and amplitude of flood events. Ultimately, on the basis of these results, I suggest potential adaptation strategies for fisheries management in Southeast Alaska, and identify knowledge gaps where further research should be prioritized.

Keywords:  Earth Systems Program
School of Earth Energy &amp; Environmental Sciences
fisheries management
Alaskan salmon
ecosystem modeling
Thesis
Advisor: De Leo Giulio
Arrigo Kevin