Growth and Survival of Larval Razorback Sucker in Natural Floodplain Depressions Inhabited by Nonnative Fish in the Green River, Utah
Garn J. Birchell and Kevin D. Christopherson
Abstract.—Floodplains are presumed to be important rearing habitat for the endangered razorback sucker Xyrauchen texanus. In an effort to recover this endemic Colorado River basin species, the Upper Colorado River Endangered Fish Recovery Program developed a floodplain acquisition and enhancement program. A levee removal study was initiated in 1996 as one component of this floodplain restoration program. The goal of the Levee Removal Study was to evaluate the system responses to levee removal and make specific recommendations concerning the value of floodplain reconnection for endangered species (specifically razorback sucker) recovery. However, because there were very few razorback suckers in the Green River, answers to several important questions pertaining to razorback sucker utilization of the floodplain were not answered during this initial study. In an effort to answer some of these questions, age-1 and larval razorback suckers were stocked into depression floodplain wetland habitats along the Middle Green River in northeastern Utah. Age-1 razorback suckers were stocked during the spring of 1999 and 2000 into The Stirrup (river kilometer [Rkm] 444.0), Baeser Bend (Rkm 439.3), and Brennan (Rkm 432.0) wetland sites. Larval razorback suckers were stocked during the spring of 1999 into The Strirrup and into Baeser Bend during 2001. At the time of stocking, each floodplain site was occupied by numerous nonnative fish, including black bullhead catfish Ictalurus melas, fathead minnow Pimephales promelas, green sunfish Lepomis cyanellus, and common carp Cyprinus carpio. The goal of this study was to test if floodplain depressions will aid in the recovery of razorback suckers.