FATTY ACID PROFILES of ALASKAN ARCTIC FORAGE FISHES: EVIDENCE of REGIONAL and TEMPORAL VARIATION by Julia Dissen Dr.Tcatrin I Ke
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Fatty acid profiles of Alaskan Arctic forage fishes: evidence of regional and temporal variation Item Type Thesis Authors Dissen, Julia Download date 07/10/2021 21:00:15 Link to Item http://hdl.handle.net/11122/6083 FATTY ACID PROFILES OF ALASKAN ARCTIC FORAGE FISHES: EVIDENCE OF REGIONAL AND TEMPORAL VARIATION By Julia Dissen Dr.TCatrin I ken Program Head, Marine Sciences and Limnology APPROVED: Qfrl/l/i/t Dr. Joan Braddock FATTY ACID PROFILES OF ALASKAN ARCTIC FORAGE FISHES: EVIDENCE OF REGIONAL AND TEMPORAL VARIATION A THESIS Presented to the Faculty of the University of Alaska Fairbanks in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE By Julia Dissen, B.S. Fairbanks, AK August 2015 ABSTRACT Fatty acids, the main components of lipids, are crucial for energy storage and other physiological functions in animals and plants. Dietary fatty acids are incorporated and conserved in consumer tissues in predictable patterns and can be analyzed in animal tissues to determine the composition of an individual’s diet. This study measured the variation in fatty acid profiles of three abundant Arctic forage fish species, Arctic Cod (Boreogadus saida), Canadian Eelpout (Lycodespolaris), and Longear Eelpout (Lycodes seminudus) across multiple years (2010-2013) and geographic locations (Beaufort and Chukchi seas). These fishes are important prey items of marine mammals, sea birds, and predatory fishes, and as such they serve as a critical trophic step connecting lower trophic-level production to higher level predators. Analyzing forage fish fatty acid profiles across multiple years and geographic locations can provide insight into system-level trends in lipid transfer through the Arctic ecosystem. Fatty acid profiles differed among species, with Arctic Cod having higher concentrations of pelagic zooplankton indicator fatty acids, and Eelpout species containing higher concentrations of indicators for benthic prey. While the two Eelpout species displayed major overlap in fatty acid profiles, differences in individual fatty acids may represent niche separation between Canadian and Longear Eelpout in the Beaufort Sea. In addition to variation between species, fatty acid profiles also differed in Arctic Cod between the Beaufort and Chukchi seas, and among collection years. High lipid content and energy-rich fatty acid classes observed in Chukchi Sea Arctic Cod relative to the Beaufort Sea Arctic Cod may indicate favorable feeding conditions in this region over the years sampled, and high energy density of Arctic Cod as prey. Despite the within-species variation observed, the results of this study suggest that Alaskan Arctic forage fish with different foraging ecology can be distinguished based on fatty acid profile, which could be useful in studies that use fatty acid data to characterize diets of top predators. v TABLE OF CONTENTS Page Signature Page.............................................................................................................................................i Title Page................................................................................................................................................... iii Abstract ........................................................................................................................................................ v Table of Contents .....................................................................................................................................vii List of Figures............................................................................................................................................ix List of Tables .............................................................................................................................................xi List of Appendices..................................................................................................................................xiii Acknowledgements .................................................................................................................................. xv INTRODUCTION ..................................................................................................................................... 1 MATERIALS & M ETHODS................................................................................................................... 8 Sample Collection..........................................................................................................................8 Lipid extraction andfatty acid transesterification................................................................. 10 Fatty acid quantification and identification ...........................................................................11 Statistical Analysis.......................................................................................................................17 RESULTS................................................................................................................................................. 21 Interspecific variation.......................................................................................................................... 21 Intraspecific variation...........................................................................................................................33 Regional differences in Arctic Cod...........................................................................................33 Interannual differences...............................................................................................................36 DISCUSSION...........................................................................................................................................45 Species-specific variation in feeding preferences............................................................................45 vii Page Temporal and regional variations in feeding of Arctic Cod........................................................... 50 Future directions................................................................................................................................... 52 CONCLUSIONS.......................................................................................................................................54 LITERATURE CITED............................................................................................................................55 APPENDICES ..........................................................................................................................................65 viii LIST OF FIGURES Page Figure 1: Fatty Acid Transfer Through Food Webs........................................................................3 Figure 2: Study Species....................................................................................................................... 7 Figure 3: Sample Stations in the Beaufort and Chukchi seas.........................................................9 Figure 4: Length to Weight Correlation of Forage Fishes...........................................................20 Figure 5: Mean Fish Sample Wet Weight .....................................................................................21 Figure 6: Mean Fish Lipid Content.................................................................................................22 Figure 7: Multivariate Representation of Fatty Acid Profiles of Species, Regions, and Y ears.................................................................................................................................. 28 Figure 8: Variation in Major Fatty Acid Classes Among Arctic Cod and Eelpout Species ...31 Figure 9: Mean Concentration of Individual Fatty Acids Contributing to Differences Among Arctic Cod and Eelpout Species.................................................................................... 33 Figure 10: Non-Methylene-Interrupted Fatty Acids (NMI) in Eelpout Species.........................34 Figure 11: Comparison of ro7/ ro9 Fatty Acids among Forage Fish Species............................... 35 Figure 12: Mean Concentration of Individual Fatty Acids in Arctic Cod Contributing to Differences Among Regions and Years ....................................................................... 37 Figure 13: Fatty Acids in Beaufort and Chukchi sea Arctic Cod .................................................39 Figure 14: Regional Variation in Major Fatty Acid Classes for Arctic Cod .............................. 40 Figure 15: Temporal Variation in Major Fatty Acid Classes for Beaufort Sea Arctic Cod ...... 41 Figure 16: Temporal Variation in Major Fatty Acid Classes for Chukchi Sea Arctic Cod 42 Figure 17: Effect of Transformations to all Fish Fatty Acid Profiles by Species........................66 Figure 18: Effect of Transformations to Beaufort Sea Fish Fatty Acid Profiles by Species ....66 ix Page Figure 19: Effect of Transformations to Arctic Cod Fatty Acid Profiles by Region and Year 66 x LIST OF TABLES Page Table 1: Fish Sample Size by Species, Region, and Y ear...........................................................10 Table 2: Fatty Acids Quantified in Fish Samples......................................................................... 15 Table 3: PERMANOVA of Fatty Acid Profiles and Covariates Corrected to Total Tissue Mass .......................................................................................................................19 Table 4: PERMANOVA