Cooperative Fish and Wildlife Research Units Program: Colorado
Education, Research and Technical Assistance for Managing Our Natural Resources

Colorado Project

Fish Population Models

August 2016 - December 2021


Participating Agencies

  • USGS Southwest Biological Center

Monitoring of the population status and dynamics of endangered humpback chub faces challenges that the population exists in remote locations (the Colorado and Little Colorado Rivers), where capture can only occur periodically, early life stages are difficult to tag, and fish are most accessible to capture only when spawning. Recently, arrays of PIT tag readers have been installed to increase the chance of tagged chub being detected. A model that integrates PIT tag detections with traditional recapture data is needed to better understand the population size and dynamics of humpback chub, including adult survival and reproductive rates, as well as juvenile recruitment and movement from the Little Colorado River to the Colorado River. In addition, for improved future monitoring a review of the sampling design and use of recapture and remote detections is needed. This project is a collaboration of the USGS-COCFWRU, the USGS Grand Canyon Monitoring and Research Center, and the USFWS. The results of the model of population size and vital rates will be used to better inform proposed management actions that affect the chub. Moreover, assessment of the sampling design itself will lead to more precise models and therefore better future management decisions.