Disturbance of Harbor Seals by Vessels in Johns Hopkins Inlet, Glacier Bay, Ak
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DISTURBANCE OF HARBOR SEALS BY VESSELS IN JOHNS HOPKINS INLET, GLACIER BAY, AK A Thesis Presented to The Faculty of Moss Landing Marine Laboratories San José State University In Partial Fulfillment of the Requirements for the Degree Master of Science by Colleen Young December 2009 © 2009 Colleen Young ALL RIGHTS RESERVED The Designated Thesis Committee Approves the Thesis Titled DISTURBANCE OF HARBOR SEALS BY VESSELS IN JOHNS HOPKINS INLET, GLACIER BAY, AK by Colleen Young APPROVED FOR MOSS LANDING MARINE LABORATORIES SAN JOSÉ STATE UNIVERSITY December 2009 Dr. James T. Harvey Moss Landing Marine Laboratories Dr. Michael H. Graham Moss Landing Marine Laboratories Dr. Scott M. Gende National Park Service ABSTRACT DISTURBANCE OF HARBOR SEALS BY VESSELS IN JOHNS HOPKINS INLET, GLACIER BAY, AK by Colleen Young Pacific harbor seal (Phoca vitulina richardii) abundance in Johns Hopkins Inlet (JHI), a glacial fjord in Glacier Bay National Park (GBNP), Alaska, has been decreasing at a concerning rate. Disease, increased predation, emigration, depletion of prey resources, and disturbance by vessels all have been implicated as causal factors of the abundance decrease. This study involved evaluating the role of disturbance by vessels during 2007 and 2008 as a causal factor in the harbor seal abundance decrease by (1) quantifying the vessel disturbance regime experienced by seals in JHI and (2) quantifying behavioral and bioenergetic impacts of vessels on seals in JHI. The presence of vessels altered the haulout patterns and behavioral activity budgets of seals by increasing the rate of flushing (vacating an iceberg and entering the water) and increasing vigilance behavior. According to the bioenergetic model used during this study, all seals flushed by vessels incurred an energetic cost, though that cost was disproportionately greater for pups than non-pups. The overall proportion of the JHI seal aggregation that was impacted by vessel disturbance was relatively low; however, repeated disturbance may be inducing the relocation of seals to other areas, and direct energetic impacts may be decreasing the individual fitness levels of pups. Vessel disturbance, therefore, may be playing direct and indirect roles in the harbor seal abundance decrease in JHI. ACKNOWLEDGEMENTS This thesis would have been impossible without Scott Gende, who provided funding for my work and provided constructive comments and encouragement during the tenure of this project. I also am eternally indebted to Jamie Womble, who provided encouragement and critical logistical support before, during, and after field camps. Jim Harvey was instrumental in my success; his help with developing this thesis and his tolerance of my sarcastic (albeit witty) comments and practical jokes are greatly appreciated. :-) Words cannot express my gratitude toward the following volunteers, who braved the cold, wet weather of southeast Alaska in order to collect data for this project: Natalie Bool, Lindsay Carroll, Ellen Chenoweth, Jesse Cohen, Brian Hoover, Anne McShane, Trevor Ose, Melissa Senac, Norma Vazquez, Eric Venturini, and Hannah Wallis. Thanks also are due to Justin Smith, Margaret Hazen, Lewis Sharman, Shannon Bros-Seemann, Mridula Srinivasan, Dave Lundquist, and Allison Banks for their many contributions. Finally, I'd like to thank my friends at MLML, who enriched my life, both academically and socially, my dive buddies, and my family, who always supported my crazy ideas and adventures. I could not have survived grad school without their support. This study was conducted under GBNP permits: GLBA-2007-SCI-0003 and GLBA-2008-SCI-0004 and SJSU IACUC protocol #899. Research was funded by NPS under Task Agreement #J9815070505 and Cooperative Agreement #H853003004. Morphometric data were collected under NOAA Fisheries Permit #358-1787 issued to ADFG (2007) and NOAA Fisheries Permit #782-1676-02 issued to NMML (2008). v TABLE OF CONTENTS List of Figures…………………………………………………………………………… vii List of Tables…………………………………………………………………………… viii Introduction………………………………………………………………………………...1 Chapter I: Quantification and characterization of the vessel disturbance regime experienced by harbor seals (Phoca vitulina richardii) in Johns Hopkins Inlet, Glacier Bay, Alaska ………………………………………………………………………………. 2 Abstract .………………………………………………………………………………….. 3 Introduction ...…………………………………………………………………………….. 4 Methods ...………………………………………………………………………………..11 Results ...………………………………………………………………………………… 19 Discussion ...…………………………………………………………………………….. 40 Literature Cited ...……………………………………………………………………….. 50 Appendix I : Relevant nomenclature defined in the MMPA ..…………………………. 55 Appendix II : Vessel regulations, with regard to harbor seals, for JHI ...………………. 56 Appendix III : Confounding factors relevant to data collection in JHI ...………………. 57 Appendix IV : Schedule of sampling days ...…………………………………………… 58 Appendix V : Ice cover index …………………………………………………………... 59 Appendix VI : Definitions of vessel types ...……………………………………………. 60 Appendix VII : Phoca follow protocol and behavior codes ...………………………….. 61 Appendix VIII : Calculation of flush rate ...…………………………………………….. 62 Appendix IX : ANCOVA results for harbor seal abundance ...………………………… 63 Appendix X : Number of vessels that entered JHI that caused a disturbance ...………... 64 Appendix XI : Parameter estimates for multinomial regression analysis ………………. 65 Appendix XII: Example: Calculating the probability of flushing ...……………………. 67 Appendix XIII: Probability of flushing a harbor seal in JHI ...…………………………. 68 Chapter II: Bioenergetic and behavioral impacts of vessels on harbor seals (Phoca vitulina richardii) in Johns Hopkins Inlet, Glacier Bay, Alaska ………..……………... 69 Abstract ...……………………………………………………………………………….. 70 Introduction ...…………………………………………………………………………… 71 Methods ...………………………………………………………………………………..74 Results ...………………………………………………………………………………… 86 Discussion ………………………………………………………………………………. 99 Literature Cited ………………………………………………………………………... 106 Appendix I: Definitions of metabolic rates ……………………………………………. 111 Conclusions…………………………………………………………………………….. 112 vi LIST OF FIGURES Chapter I: Figure 1. Locations of Glacier Bay National Park and Johns Hopkins Inlet…………….. 7 Figure 2. Census data for harbor seals (Phoca vitulina) in JHI, August 1992-2002…….. 9 Figure 3. Vessel permits issued in GBNP, 1998-2008………………………………….. 12 Figure 4. Average daily vessel use in JHI by month and vessel type during 2007 & 2008…………………………………………………………………………… 23 Figure 5. Extrapolated monthly vessel use of JHI during 2007 & 2008 based on vessel use during sampling days……………………………………………………… 24 Figure 6. Estimated percentage of vessels in GBNP that visited JHI during July and August, 2007 & 2008………………………………………………………….. 25 Figure 7. Harbor seal (Phoca vitulina) abundance in JHI by month and year, 2007 & 2008…………………………………………………………………………… 27 Figure 8. Diel variation in harbor seal (Phoca vitulina) abundance in JHI, 2007-2008.... 28 Figure 9. Population abundance trend for harbor seals (Phoca vitulina) in JHI, August 1992-2008………………………………………………………………………29 Figure 10. Daily proportions of total harbor seals (Phoca vitulina) present in JHI that were flushed by vessels during 2007 and 2008………………………………. 30 Figure 11. Disturbance rates of harbor seals (Phoca vitulina) in JHI among vessel types during 2007 and 2008………………………………………………………… 31 Figure 12. Effects of the covariates DIST and SEALS on disturbance rates among vessel types…………………………………………………………………… 33 Figure 13. Frequency of seal flushing based on the distance of an approaching vessel.... 38 Figure 14. Cumulative frequency of seal flushing based on the distance of an approaching vessel…………………………………………………………… 39 Chapter II: Figure 1. Predicted heat production and heat loss, as a function of body mass, for undisturbed harbor seals (Phoca vitulina) in JHI………………………………88 Figure 2. Disturbance-induced changes in energy for harbor seals (Phoca vitulina) in JHI……………………………………………………………………………... 89 Figure 3. Walleye pollock (Theragra chalcogramma) biomass necessary for consumption by harbor seals (Phoca vitulina) to compensate for energetic costs of vessel disturbance…………………………………………………….. 92 Figure 4. Vigilance behavior of harbor seals (Phoca vitulina) in the presence and absence of vessels………………………………………………………………98 vii LIST OF TABLES Chapter I: Table 1. Summer vessel quotas in Glacier Bay National Park, 1 May-30 September……………………………………………………………………..... 10 Table 2. Record of vessels that entered JHI on sampling days, July-September, 2007 & 2008…………………………………………………………………………….. 20 Table 3. Harbor seal (Phoca vitulina) abundance monitoring summary, 2007-2008…… 26 Table 4. Classification table for the final model used to predict the probability of harbor seal flushing in JHI……………………………………………………………... 36 Table 5. Vessel activity in JHI resulting in a violation of the 0.25 nm distance restriction……………………………………………………………………….. 37 Table 6. Suggestions for possible modifications to current harbor seal (Phoca vitulina) related vessel regulations for JHI………………………………………………. 49 Chapter II: Table 1. Sources, values, and equations of parameters used to estimate heat loss of harbor seals (Phoca vitulina) in JHI……………………………………………. 81 Table 2. Age class, sex, average morphometric measurements, and calculated values used in bioenergetic models……………………………………………………. 87 Table 3. Predicted differences in energy balance for disturbed harbor seals (Phoca vitulina) in JHI………………………………………………………………….. 91 Table 4. Number of Walleye pollock (Theragra chalcogramma) necessary for consumption