Razorback and Flannelmouth Sucker hybrid hatch rates and larval survival

Authors: Pilar. Gibb Wolters, Ward Alice, Rogowski David, Pilar. Gibb David

Year: 2016 (xlviii)

Abstract

Prior to the construction of large dams, the endangered Razorback Sucker Xyrauchen texanus once made long spawning migrations through the Grand Canyon to the upper basin of the Colorado River. Historically, hybridization between Razorback Sucker and Flannelmouth Sucker Catostomus latipinnis rarely occurred because of separation in spawning location and timing of the two species. As a result of modification of the river by dams, we are seeing an increase in hybridization between Razorback and Flannelmouth suckers. To enhance management of the endangered Razorback Sucker, the Arizona Game and Fish Department in collaboration with Grand Canyon Research and Monitoring Center-USGS, and Northern Arizona University is conducting a study to develop field identification tools for hybrid suckers, and evaluate sucker hybrid viability. Gametes were stripped and mixed to make four treatments: 1) female Razorback x male Flannelmouth, 2) female Flannelmouth x male Razorback, 3) Flannelmouth, and 4) Razorback. Each combination was reared in replicate among four tanks. We compared hatch rates and larval survival of t he four treatments to determine if there were any significant differences between hybrids and pure fish. If hybrid offspring are fully viable, it has very important ramifications for species definitions, listing status, and recovery of razorback suckers throug hout the Colorado River basin.