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Monitoring population status of sea otters (Enhydra lutris) in Glacier Bay National Park and Preserve, Alaska: options and considerations

Open-File Report 2015-1119
National Park Service, Southeast Alaska Inventory and Monitoring Network
By: , , , and 
https://doi.org/10.3133/ofr20151119

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Abstract

After many decades of absence from southeast Alaska, sea otters (Enhydra lutris) are recolonizing parts of their former range, including Glacier Bay, Alaska. Sea otters are well known for structuring nearshore ecosystems and causing community-level changes such as increases in kelp abundance and changes in the size and number of other consumers. Monitoring population status of sea otters in Glacier Bay will help park researchers and managers understand and interpret sea otter-induced ecosystem changes relative to other sources of variation, including potential human-induced impacts such as ocean acidification, vessel disturbance, and oil spills. This report was prepared for the National Park Service (NPS), Southeast Alaska Inventory and Monitoring Network following a request for evaluation of options for monitoring sea otter population status in Glacier Bay National Park and Preserve. To meet this request, we provide a detailed consideration of the primary method of assessment of abundance and distribution, aerial surveys, including analyses of power to detect interannual trends and designs to reduce variation around annual abundance estimates. We also describe two alternate techniques for evaluating sea otter population status—(1) quantifying sea otter diets and energy intake rates, and (2) detecting change in ages at death. In addition, we provide a brief section on directed research to identify studies that would further our understanding of sea otter population dynamics and effects on the Glacier Bay ecosystem, and provide context for interpreting results of monitoring activities.

Suggested Citation

Esslinger, G.G., Esler, D., Howlin, S., and Starcevich, L.A., 2015, Monitoring population status of sea otters (Enhydra lutris) in Glacier Bay National Park and Preserve, Alaska—Options and considerations: U.S. Geological Survey Open-File Report 2015-1119, 42 p., http://dx.doi.org/10.3133/ofr20151119.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Chapter 1. Estimating Sea Otter Abundance and Distribution Using Aerial Surveys
  • Chapter 2. Estimating Sea Otter Diets and Energy Intake Rates
  • Chapter 3. Detecting Change in Population Status by Monitoring Ages at Death
  • Directed Research
  • Synthesis
  • Acknowledgments
  • References Cited
  • Appendix A. Simulation Plots
Publication type Report
Publication Subtype USGS Numbered Series
Title Monitoring population status of sea otters (Enhydra lutris) in Glacier Bay National Park and Preserve, Alaska: options and considerations
Series title Open-File Report
Series number 2015-1119
DOI 10.3133/ofr20151119
Year Published 2015
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Alaska Science Center Biology MFEB
Description iv, 42 p.
Country United States
State Alaska
Other Geospatial Glacier Bay National Park and Preserve
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details