Integrating disparate data sources to investigate spatiotemporal population dynamics in U.S. West Coast fishes

Abstract

Fluctuations in fish populations are driven by many factors, including environmental, community, and anthropogenic variability. In my dissertation, I integrate a variety of data sources to model population dynamics and investigate how different fish species of conservation and management concern respond to this variability. I focus on a different species and study system in each chapter, tailoring the analysis to the key information gaps and available data. In my first chapter, I collate two sources of data, a reconstructed catch history and limited length data, to develop a data-limited population assessment model for threatened Yelloweye Rockfish in Puget Sound. Despite a high degree of uncertainty, I found that demographic information suggests that this population has recovered significantly in recent decades. Second, I construct a multistate model to estimate the combined influences of climate and hydropower on the movement decisions of adult Steelhead returning to the Columbia River Basin. I found that Steelhead movements are strongly thermally influenced, but that allowing individuals to move via dam spillways may increase survival to natal tributaries. Third, I model the proximate trophic drivers of marine survival in interior Columbia River Basin Fall Chinook Salmon, integrating three separate fishery-independent surveys that provide complementary data on the community in the coastal ocean. Top-down effects were generally more supported than bottom-up effects, with spatiotemporal overlap between salmon and their predators playing a key role in modulating survival. Finally, I investigate the drivers of spatiotemporal recruitment variability in Sablefish on the U.S. West Coast, using output from oceanographic models to describe environmental conditions. I found that while the presence of Sablefish recruits was not associated with the local environmental conditions examined, the abundance of recruits was associated with cooler temperatures and higher productivity. This dissertation reveals new mechanisms of variability in multiple key species on the U.S. West Coast, providing additional context for the management and recovery of these species.