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U.S. Geological Survey Fact Sheet 2009-3035

The science provider to the Glen Canyon Dam Adaptive Management Program

Status and Trends of the Grand Canyon Population of Humpback Chub

By Matthew E. Andersen



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The Colorado River Basin supports one of the most distinctive fish communities in North America, including the federally endangered humpback chub (Gila cypha). One of only six remaining populations of this fish is found in Grand Canyon, Arizona. U.S. Geological Survey scientists and their cooperators are responsible for monitoring the Grand Canyon population. Analysis of recently collected data indicates that the number of Grand Canyon adult humpback chub—fish 4 years old and older and capable of reproduction—increased approximately 50 percent between 2001 and 2008. When possible model error is considered, the estimated number of adult chub in the Grand Canyon population is between 6,000 and 10,000. The most likely number is estimated at 7,650 individuals.

Version 1.0

First posted April 27, 2009

This report is also available in print from:

USGS Information Services, Box 25286,
Federal Center, Denver, CO 80225
telephone: 888 ASK-USGS; e-mail:

This report is presented in Portable Document Format (PDF); at least version 7 of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Andersen, Matthew E., 2009, Status and trends of the Grand Canyon Population of humpback chub: U.S. Geological Survey Fact Sheet 2009-3035, 2 p. [].




Monitoring the Humpback Chub Population

Causes of the Population Increase

Experimental Water Releases

Removal of Nonnative Fish

Drought-Induced Warming


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