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Assessment of Dragonfly and Damselfly (Odonata) Occupancy and Habitat Suitability at −12 Mile Slough, Glen Canyon National Recreation Area, Arizona

Open-File Report 2025-1042
National Park Service, Bureau of Reclamation, Springs Stewardship Institute
By: , , , and 
https://doi.org/10.3133/ofr20251042

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Abstract

Management practices that enhance habitat complexity in dam tailwaters often aim to increase biodiversity and improve ecosystem health. However, in other instances, management practices may simplify habitat features to help minimize the establishment of invasive species. These tradeoffs are complex, particularly in the face of drought and warming water temperatures. In Glen Canyon National Recreation Area, a backwater known as −12 Mile Slough (henceforth the Slough), located 5-kilometers downstream from Glen Canyon Dam, is being considered for removal to reduce breeding habitat for warmwater nonnative fishes. In this report, the habitat suitability for and occupancy of dragonflies and damselflies (Odonata) at the Slough are assessed. U.S. Geological Survey staff conducted three site visits to the Colorado River in Glen Canyon, the Slough, and another backwater (“Frogwater”) on September 11–13, and 26, 2024. The physical habitat of the sampling sites was characterized by recording water temperatures, specific conductance, dissolved oxygen, turbidity, flow, depth, and benthic substratum size distribution. We sampled aquatic macroinvertebrates and riparian macroinvertebrates using benthic and aerial collection methods, respectively. We describe three distinct benthic aquatic invertebrate communities in and around the Slough, two of which contained Odonata. We found no Odonata larvae in the mainstem, at Frogwater, or in the Lower Slough. Using historic specimen data from the Museum of Northern Arizona, we report 8 species of damselflies from one family (Coenagrionidae) and 8 species of dragonflies from three families (Aeshnidae, Gomphidae, and Libellulidae) in Glen Canyon between 1985 and 2024. We discuss the habitat requirements of Odonata larvae known to occur in the Slough, as well as their cultural and recreational values. We conclude that channelization of the Slough to cool water temperatures may reduce larval Odonata habitat locally but is unlikely to affect their diversity and abundance on a regional scale.

Suggested Citation

Metcalfe, A.N., Ford, M.A., Stevens, L.E., and Kennedy, T.A., 2025, Assessment of dragonfly and damselfly (Odonata) occupancy and habitat suitability at −12 Mile Slough, Glen Canyon National Recreation Area, Arizona: U.S. Geological Survey Open-File Report 2025–1042, 15 p., https://doi.org/10.3133/ofr20251042.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Background
  • Methods
  • Results
  • Discussion
  • Odonata Ecology and Biodiversity
  • Cultural Significance of Glen Canyon Odonata
  • Implications of Slough Channelization
  • Summary
  • Acknowledgments
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Assessment of dragonfly and damselfly (Odonata) occupancy and habitat suitability at −12 Mile Slough, Glen Canyon National Recreation Area, Arizona
Series title Open-File Report
Series number 2025-1042
DOI 10.3133/ofr20251042
Publication Date December 12, 2025
Year Published 2025
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Southwest Biological Science Center
Description Report, ix, 15 p.; Data Release
Country United States
State Arizona
Other Geospatial 12 Mile Slough, Glen Canyon National Recreation Area
Online Only (Y/N) Y
Additional publication details