Critical swim speeds of two suckers and their hybrids

Authors: David Rogowski, Cory Nielson, Pilar Wolters

Year: 2019

Abstract

The Razorback Sucker, Xyrauchen texanus, and Flannelmouth Sucker, Castostomus latipinnis, are two fish native to the Colorado River basin. Currently within the Grand Canyon, Flannelmouth Suckers are abundant while Razorbacks remain extremely rare. Flannelmouth Suckers are found in abundance throughout the flowing waters of the Colorado River, while Razorback Suckers are generally found in the still or slow moving waters of Lake Powell, Lake Mead, and their inflows. Hybridization between these species occurs in the wild, however little is known concerning physiological differences between them and their hybrids. We investigated the differences in critical swim speed of purebred and hybrids of these species. A fish’s critical swimming velocity is a measure of its sustained swimming ability, not its maximum sprint speed. Determining the critical swimming speed of these species may illuminate how water velocity affect habitat constraints of these species, and increase our understanding of future repatriation challenges for the Razorback Sucker. Flannelmouth Suckers had a higher critical swim speed than Razorback Suckers, with hybrids intermediate. The critical swim speed results of these purebred catastomid species are consistent with general flow conditions of these habitat types where they are commonly found. The slower critical swim speed of Razorback Suckers could indicate challenges to repatriation throughout the Colorado River basin. Disparities in critical swim speed may be linked to physiological differences of the two species. Wolters (2017) did not see significant differences in body shape of Razorback and Flannelmouth Suckers and their hybrids up to 140 mm in length, but differences in behavioral and/ or metabolic performance have not been explored. Both hybrid types resulted in critical swim speeds between those of their parental stocks. The parental combination had significant effects, with swimming ability most consistent with their paternal species.