RII Track-4: Using Otolith Geochemistry to Understand the Ocean Ecology of a Changing Alaskan Salmon System

University Of Alaska Fairbanks Campus, Fairbanks AK

Investigators

Abstract

High latitude regions of the global ocean are responding rapidly to atmospheric and other environmental changes. Thus, these ecosystems are important models for understanding environmental driver and ecosystem response relationships, providing a framework for better predicting how other regions of the global ocean might respond to future environmental changes. Of particular concern are the impacts of rapid marine ecosystem changes to fisheries. Seafood plays a key role in meeting the food security needs of global human populations and is a critical foundation of many regional economies in the United States, particularly for remote states such as Alaska. Between 2014-2016, the eastern sector of the North Pacific Ocean including the Gulf of Alaska (GOA) experienced one of the largest marine heatwaves ever recorded. How the ocean ecology of Pacific salmon (Oncorhynchus spp.) responds to ocean-climate variability and other environmental changes is generally not well understood. The purpose of this study is to advance an understanding of the ocean ecology of salmon by taking advantage of the complete life history record captured by natural markers of water temperature, metabolic activity, and diet based on oxygen and carbon isotope values in the ear bones, or otoliths, of adult sockeye salmon (O. nerka) returning to the Copper River, Alaska. This research is important for advancing the general knowledge of high latitude marine ecosystem response to rapid and unprecedented levels of environmental change, as well as developing the scientific information needed to inform the long-term sustainable management of this key Alaskan salmon system. Between 2014-2016, the eastern sector of the North Pacific Ocean including the Gulf of Alaska (GOA) experienced one of the largest marine heatwaves ever recorded. Responses by southcentral Alaskan salmon stocks to these anomalous ocean-climate conditions in the GOA, and other density-dependent environmental changes related to the release of significant numbers of hatchery pink salmon to the GOA, have been highly variable and range from record returns by Prince William Sound pink salmon (Oncorhynchus gorbuscha) in 2015 to run failures by these same stocks in 2016, as well as run failures by sockeye salmon (O. nerka) returning to the nearby Copper River system in 2018. Thus, Pacific salmon of the GOA appear to be responding to recent, highly anomalous environmental changes, however, environmental driver and salmon response relationships have not been formalized. The research described here will fill this knowledge gap. The goal of this EPSCoR Fellowship project is to relate otolith and isotope variability during ocean residency of adult sockeye salmon returning to the Copper River, Alaska, over a 15-year period (2004-2018) to a suite of environmental variables that capture signals of ocean-climate and density-dependent factors operating in the North Pacific Ocean, as well as population performance traits of sockeye including adult body size and body condition. Time series analysis will be used to formalize relationships between environmental drivers and responses by Copper River sockeye to advance the general knowledge of high latitude marine ecosystem response to rapid and unprecedented levels of environmental change, as well as the scientific information needed to inform the long-term sustainable management of this key Alaskan salmon system. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.