Hybridization between Native Bartram’s Bass and Two Introduced Species in Savannah Drainage Streams
Jean K. Leitner, Kenneth J. Oswald, Max Bangs, Dan Rankin, and Joseph M. Quattro
Abstract.—Bartram’s Bass (an as yet unnamed species similar to Redeye Bass Micropterus coosae) is endemic to the Savannah drainage of South Carolina and Georgia. Hybridization between this native species and introduced Alabama Bass M. henshalli is widespread in the upper portions of the drainage. Recent studies have documented a precipitous decline in genetically pure Bartram’s Bass in Savannah drainage reservoirs and a corresponding increase in fish of hybrid origin. We surveyed tributary populations associated with these reservoirs and with the Savannah River main stem in 2004 and 2010. Results indicate an increased occurrence of hybrids in Bartram’s Bass native stream habitats over time. We also document the new occurrence of a second nonnative species, Smallmouth Bass M. dolomieu. Both Smallmouth Bass and their hybrids with Bartram’s Bass were collected from shoals in the Savannah River near the lower extent of the Bartram’s Bass range. Bartram’s Bass is a species of highest conservation concern in South Carolina, due to its limited native range and threats associated with hybridization. Conservation actions directed at this species, and its native stream habitats, will need to consider the establishment of nonnative species in the drainage and their potential to impact tributary populations over time.