Rangewide Survey of the Introgressive Status of Guadalupe Bass: Implications for Conservation and Management

Abstract

The stocking of fishes outside of their native range for the purpose of sport fisheries can lead to secondary contact and introgression between species that were historically allopatrically distributed. Smallmouth Bass Micropterus dolomieu were introduced within the range of Guadalupe Bass M. treculii in central Texas and introgressive hybridization subsequently occurred. One recent survey of temporal changes in introgression in the Blanco River found that introgression had increased and that Guadalupe Bass had been extirpated. Thus, a survey of changes in introgression across the range of the Guadalupe Bass was conducted in 12 subbasins in the Brazos, Colorado, Guadalupe–San Antonio, and Nueces drainages in Texas using 15 microsatellite loci. The results indicate that introgression is now occurring in four subbasins but no longer occurring in the Lampasas and San Gabriel rivers, where rates were previously 6% and 46%, respectively. Additionally, we found no evidence that stocking of hatchery-reared individuals in the Guadalupe and Nueces rivers has led to severely depressed genetic variation. The variable success of restoration efforts to prevent extirpation of the Guadalupe Bass suggests that protection of the remaining nonintrogressed populations should be a priority for the conservation of this species.

Received April 24, 2012; accepted December 9, 2012

ACKNOWLEDGMENTS

M. Bean, J. Perkin, Z. Shattuck, K. Kollaus, C. Thomas, C. Williams, and numerous Texas State University–San Marcos ichthyology and zoology students assisted in field collection efforts. All fishes were collected under Texas State University–San Marcos IACUC permit number 0723-0830-07 and Texas Parks and Wildlife Department scientific collection permit 0601-159 issued to Timothy Bonner. Funding for this research was provided by the Texas Parks and Wildlife Department, Federal Aid in Sport Fish Restoration Act Project F-197-R-1, National Science Foundation (DGE-0742306), and the Texas State University–San Marcos Department of Biology.