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AN ABSTRACT OF THE THESIS OF Katelyn M. Qualls for the degree of Master of Science in Ocean, Earth, and Atmospheric Sciences presented on April 2, 2019. Title: Drivers of Euphausiid Abundance and Biomass in the Kitimat Fjord System, BC Canada. Abstract approved: _____________________________________________________________________ Kim S. Bernard Euphausiids are recognized as essential components of marine food webs throughout the world’s oceans due to their role as prey for many species including whales, seabirds, and commercial fishes. The Kitimat Fjord System is an important fisheries area and is the only fjord habitat on the British Columbia coast that is designated as Critical Habitat for humpback whales. Despite this, very little was previously known about the area’s composition of euphausiid species, temporal and spatial patterns in these species’ abundances and distributions, and the environmental drivers of those patterns. In this study, zooplankton samples were collected and CTD casts were conducted at a repeated network of stations in the Kitimat Fjord System in summer 2015 (May-September). The relationships between euphausiid abundance and a suite of spatial, temporal, and oceanographic variables were analyzed in order to examine the potential drivers of euphausiid abundances in this important coastal fjord environment. Six species of euphausiids were present in the study area, with Euphausia pacifica and Thysanoessa spinifera being the most abundant (52.6% and 46.3%, respectively). The following rare species were also captured: Thysanoessa longipes, Thysanoessa gregaria, Tessarabrachion oculatum, and Nematoscelis difficilis. However, due to the scarcity of these rare species, (1) it was difficult to establish patterns in their distribution and (2) there was not enough data available to examine the drivers of these species’ abundances. Results indicated that while E. pacifica and T. spinifera were typically found to be sympatric, E. pacifica was more dominant in the inner fjords and T. spinifera was more dominant near the mouth of the fjords. Strong temporal changes in the abundance of early furcilia suggest that peak E. pacifica spawning occurred about one month earlier than peak T. spinifera spawning in this region. Competing generalized additive model (GAM) formulations, each representative of a different hypothesis for euphausiid distribution, were used to investigate the effects of (1) temporal, (2) spatial, (3) oceanographic, and (4) combined temporal, spatial, and oceanographic covariates on E. pacifica and T. spinifera abundance and biomass. Results of these GAMs suggested some species-specific responses to environmental factors, indicating that niche differentiation is occurring in this dynamic habitat. Combined models were consistently more parsimonious than others, suggesting that the controls on euphausiid abundance are complex. Model results indicated that E. pacifica biomass is significantly positively related to sea surface temperature and highest around seafloor depths of 375 m. T. spinifera biomass was found to be positively affected by day of the year and negatively affected by distance into the fjordland. Determining the drivers of species-specific spatiotemporal patterns in euphausiid abundance is (1) crucial to understanding how environmental variables shape the distribution of euphausiid species and (2) necessary for understanding how oceanographic change could impact euphausiid populations. The results of this study have implications for understanding the distribution patterns of top predators in the area and can be used to predict future changes in euphausiid abundance and distribution in the Kitimat Fjord System. ©Copyright by Katelyn M. Qualls April 2, 2019 All Rights Reserved Drivers of Euphausiid Abundance and Biomass in the Kitimat Fjord System, BC Canada by Katelyn M. Qualls A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented April 2, 2019 Commencement June 2019 Master of Science thesis of Katelyn M. Qualls presented on April 2, 2019. APPROVED: _____________________________________________________________________ Major Professor, representing Ocean, Earth, and Atmospheric Sciences _____________________________________________________________________ Dean of the College of Earth, Ocean, and Atmospheric Sciences _____________________________________________________________________ Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. _____________________________________________________________________ Katelyn M. Qualls, Author ACKNOWLEDGEMENTS I find myself indebted foremost to my advisor, Kim Bernard, for her guidance, helpful critiques, insight, and support. Her suggestions, edits, and assistance during the preparation of this thesis were invaluable and without her mentorship this project would not have been possible. Her excitement for science rubbed off on me and she kept me motivated and pointed in the right direction during the many points in my degree at which I felt stressed and overwhelmed. I am also immensely appreciative of the knowledge of modeling analyses that my committee member Lorenzo Ciannelli shared with me, and am grateful for the help with modelling in R that he provided. His expertise in modelling and guidance in designing and verifying statistical analyses greatly improved the statistical methods in this thesis. I am also indebted to my graduate committee member Jim Lerczak, who assisted with interpreting environmental data and provided valuable feedback and advice on the oceanographic component of my thesis. My research was supported by the National Science Foundation Graduate Research Fellowship under Grant No. 1314109-DGE. I am grateful for my mentors and friends who wrote reference letters and provided advice that helped me receive this grant. I am also thankful for my friends and family who were always rooting for me and filled my years at Oregon State with laughter, fun, and adventure. This research also would not have been possible without the tirelessness, persistence, and adventurous spirit of Eric Keen, the captain of the RV Bangarang and PI who organized the collection of zooplankton and CTD data analyzed in this thesis. His extensive and impressive work collecting, organizing, and processing data, in addition to his help with analyzing data in R, made this thesis possible. Fieldwork was conducted under federal permit (DFO XR 83 2014) in collaboration with the North Coast Cetacean Society and under a formal research agreement with the Gitga’at First Nation. Funding for fieldwork was provided by the Gitga’at First Nation Guardian Watchmen, Canadian Department of Fisheries and Oceans, Cascadia Research Collective, NSF Graduate Research Fellowship program (DGE-114086), Lewis and Clark Fund, and private donations from the Watson, Ayres, Cunningham, Barlow, Wright, and Keen families. The CTD used in this research was provided by Gitga’at Guardian Watchmen and Tides Canada. Fieldwork would not have been possible without the friendship and support of J. Wray and H. Meuter, or without the dedication, skills and friendship of RV Bangarang crew: W. and K. Watson, D. and L. Padgett, M. Irwin, N. Pierson, K. Beach, J. Carpenter, M. Keen, K.-L. Thompson, W. Bostwick, J. Barlow, B. Taylor, A. Simonis, S. Watson, E. Ezell, S. Keen, N. Bruns, and J. Garretson. This thesis, in part, is a reprint of a manuscript that has been submitted to Progress in Oceanography: Qualls, K.M., Bernard, K.S, Keen, E.M., Ciannelli, L., Picard, C.R. “Drivers of Euphausia pacifica and Thysanoessa spinifera Abundances in the Kitimat Fjord System, BC Canada”. The thesis author was the primary investigator and author of this paper. TABLE OF CONTENTS Section Page Chapter 1: Introduction ................................................................................................... 1 1.1 Euphausiids ....................................................................................................... 1 1.2 Drivers of Spatial and Temporal Variability in Euphausiid Abundance .............. 4 1.3 Common Euphausiid Species Found on the British Columbia Coast .................. 5 1.4 Study Area: The Kitimat Fjord System .............................................................. 7 1.5 Objectives ........................................................................................................ 13 Chapter 2: Material and Methods .................................................................................. 16 2.1 Data Collection ................................................................................................ 16 2.2 Calculations ..................................................................................................... 24 2.3 Statistical Modeling ......................................................................................... 25 Chapter 3: Results ......................................................................................................... 35 3.1 Oceanographic Results..................................................................................... 35 3.2 Euphausiid Abundance, Biomass, and Distribution .......................................... 41 3.3 E. pacifica and T. spinifera Abundance Model Results .................................... 49 3.4 E. pacifica and T. spinifera Biomass Model
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