Acclimation of razorback sucker, Xyrauchen texanus, in a manipulated flood plain wetland on the middle Green River, Utah

Authors: Aaron Webber

Year: 2009 (xli)

Abstract

The razorback sucker,Xyrauchen texanus, is an endangered fish endemic to the Colorado River Basin. As part of recovery efforts, razorbacks were taken in to hatcheries to be produced and stocked back into the rivers. These hatchery fish may lack the behavioral skills necessary to survive well in the wild. We thought that if we stocked larval razorbacks into the natural environment where they would grow up in the wild, these fish would acquire the skills necessary to survive in the wild and survive better than the razorbacks that grow up in a hatchery. We chose Baeser Bend (a wetland on the middle Green River, UT) as a wetland we could manipulate to use as an acclimation site for razorback suckers. Baeser was reset during the winter of 2007-2008 to eliminate any other fish species. In May 2008, 43,400 larval razorbacks from the Ouray National Fish Hatchery were stocked into the wetland. In April 2009, an estimated 3,500 survived (8%). In October 2008, 24,000 more razorbacks that were raised in an earthen pond at the hatchery and averaged 93 mm were stocked in Baeser. In April 2009, we estimated that cohort at 12,000. In June 2009, an additional 110,000 larval razorbacks were stocked. All of the razorbacks from the 2008 stockings should be between 250-400 mm by October 2009, when we plan to PIT tag them and release them into the Green River. Before abstract submission, 330 razorbacks were tagged and released from Baeser Bend to the Green River. We plan on continuing to use Baeser Bend as an acclimation site, and ultimately we plan to deploy pit tag readers on a known razorback spawning bar near Baeser Bend to determine if the razorbacks from Baeser Bend will contribute to the spawning razorback population.