Colorado River fish monitoring in Grand Canyon, Arizona; 2002–14 humpback chub aggregations

Open-File Report 2016-1177
Prepared in cooperation with the U.S. Fish and Wildlife Service
By: , and 



The humpback chub (Gila cypha) is an endangered cyprinid species endemic to the Colorado River. The largest remaining population of the species spawns and rears in the Little Colorado River in Grand Canyon. Construction and operation of Glen Canyon Dam has altered the main-stem Colorado River in Glen and Grand Canyons. Cold, clear water releases from the dam result in a river that is generally unsuitable for successful humpback chub reproduction. During the early 1990s, nine locations within the main-stem Colorado River were identified as humpback chub aggregations—areas with a consistent and disjunct group of fish with no significant exchange of individuals with other aggregations. We monitored main-stem Colorado River aggregations of humpback chub in Grand Canyon during 2010 to 2014 and compared our results to previous investigations. Relative abundance, as described by catch per unit effort (fish per hour) of adult humpback chub at most main-stem aggregations, generally increased from the 1990s to 2014. In addition, distribution of humpback chub in the main-stem Colorado River has increased since the 1990s. Movement of humpback chub between the Little Colorado River and other aggregations likely adds fish to those aggregations. There is clear evidence of reproduction near the 30-Mile aggregation, and reproduction at Middle Granite Gorge and downstream seems likely based on catches of gravid fish and captures of very young fish, especially during relatively warm water releases from Glen Canyon Dam, 2004 to 2011. Humpback chub relative abundance at Shinumo and Havasu Creek inflows increased following translocations of young humpback chub starting in 2009. In light of this information, we modify the original nine aggregations, combining two previously separate aggregations and dropping two locations to form six distinct aggregations of humpback chub. Trends in humpback chub abundance at main-stem aggregations, relative to management actions (for example, translocations) or changing environmental conditions (for example, river warming), informs management of the species across a riverscape scale within the Colorado River.

Suggested Citation

Persons, W.R., Van Haverbeke, D.R., and Dodrill, M.J., 2017, Colorado River fish monitoring in Grand Canyon, Arizona; 2002–14 humpback chub aggregations: U.S. Geological Survey Open-File Report 2016–1177, 43 p.,

ISSN: 2331-1258 (online)

Table of Contents

  • Abstract
  • Introduction
  • Methods of Investigation
  • Results and Discussion
  • Summary and Conclusions
  • Acknowledgments
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Colorado River fish monitoring in Grand Canyon, Arizona; 2002–14 humpback chub aggregations
Series title Open-File Report
Series number 2016-1177
DOI 10.3133/ofr20161177
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Southwest Biological Science Center
Description v, 43 p.
Country United States
State Colorado
Other Geospatial Grand Canyon
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details