Date of Award

12-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Statement

Doctor of Philosophy in Fisheries

Department

Department of Fisheries

Granting Institution

University of Alaska Fairbanks

Committee Chair

Cunningham, Curry J.

Committee Member

Mueter, Franz J.

Committee Member

Kimmel, David

Committee Member

Rogers, Lauren

Table of Contents

Chapter 1: Introduction

Chapter 2: Evaluating the performance of a system model in predicting zooplankton dynamics: insights from the Bering Sea ecosystem

Chapter 3: Impacts of climate change on Bering Sea copepod phenology and reproductive strategy

Chapter 4: Understanding marine and freshwater processes affecting the survival of Yukon River chum salmon using an integrated population model

Chapter 5: Partitioning marine, freshwater, and parental contribution to sockeye salmon life history

Chapter 6: General conclusions

Abstract

Climate change is rapidly transforming Northeast Pacific ecosystems and fundamentally altering environmental conditions that drive species' survival, growth, and life histories. This dissertation examines relationships between environmental change and population-level processes across Northeast Pacific marine and freshwater ecosystems. This dissertation focuses on understanding the influence of environmental change on foundational zooplankton communities in the Bering Sea and Pacific salmon populations, specifically Yukon River Chum salmon and Bristol Bay Sockeye salmon. This research addresses knowledge gaps in zooplankton systems modeling, zooplankton phenology, and salmon population dynamics. First, this dissertation evaluated the performance of a systems model that utilizes climate and physical oceanography to simulate zooplankton biomass, against empirical zooplankton data collected via ship-based surveys. This research revealed misalignment in absolute biomass and interannual zooplankton variability, with implications for how current ecosystem models could inform fisheries management. Second, this research investigated climate-driven changes in Bering Sea copepod development phenology. Results indicated that temperature and wind frequency mediate copepod life stage composition, with evidence of environment-induced multivoltinism in Calanus spp. Next, this research examined Pacific salmon responses to ecosystem change across their life cycles. Using an integrated population model developed for Yukon River fall Chum salmon, this dissertation suggests that recent population declines are associated with reduced survival across multiple life stages, with the strongest survival-environment linkages occurring during marine residence periods. Reduced juvenile stomach fullness, increased winter temperatures, and elevated competition from hatchery-reared Chum salmon were related to decreased marine survival. Finally, this research used dynamic structural equation modeling to examine processes associated with sockeye salmon age composition in Lake Iliamna, Alaska. This revealed that temperature synchrony across freshwater and marine ecosystems is related to shifts toward more frequent occurrence of younger age classes, with implications for population resilience and fishery yields. Together, these findings advance understanding of how environmental relationships contribute to zooplankton and salmon population dynamics, with implications for ecosystem resilience and fisheries management in a changing North Pacific.

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