Large-River Fish Conservation in the Colorado River Basin: Progress and Challenges with Endangered Razorback Sucker

Authors: Kevin Bestgen, Thomas Dowling, Brandon Albrecht, Koreen Zelasko

Year: 2018

Abstract

Razorback Sucker Xyrauchen texanus, a historically widespread and abundant warmwater fish endemic to the Colorado River basin, has declined dramatically. Habitat alteration, dams that block migration routes and alter natural sediment, stream flow, and thermal regimes, channel change, and nonnative fish predation are reasons for decline of Razorback Sucker. Lack of recruitment was evident more than 50 years ago and all wild fish were eventually extirpated, with the possible exception of the small Lake Mead population. Extensive restoration efforts have had mixed outcomes. Various propagation programs have restored reproducing adults in lakes Mohave, Havasu, and Powell in downstream basin reaches, and the San Juan, Colorado, and Green rivers in the upper Colorado River basin. However, nonnative predators reduce survival of stocked fish and recruitment is non-existent except in Lake Mead. Localized recruitment in Lake Mead, and new strategies to enhance juvenile production in isolated lower Colorado River backwaters and connected Green River floodplain wetlands offer examples of recent successes. Further progress toward restoration of large-river fishes including razorback sucker requires?additional flow, habitat, and nonnative fish management, and continued long-term support for conservation programs.