SEAFWA 2017

AUTHORS: Andrew T. Taylor, Oklahoma State University; Michael D. Tringali, Florida Fish and Wildlife Conservation Commission; James M. Long, U.S. Geological Survey and Oklahoma Cooperative Fish and Wildlife Research Unit

ABSTRACT: The Shoal Bass (Micropterus cataractae) is a sportfish endemic to the Apalachicola-Chattahoochee-Flint Basin of the southeastern US. Introgressive hybridization between Shoal Bass and non-native congeners poses a pertinent conservation threat. In 2003, supplemental stocking of Shoal Bass fingerlings began in a reach of the Chattahoochee River below Morgan Falls Dam (MFD), Georgia, in response to local population declines. However, several non-native species may be jeopardizing these restoration efforts, including Smallmouth Bass (M. dolomieu) that were illegally introduced beginning in 2004. Our primary objective was to characterize hybridization following Shoal Bass and non-native stockings. A secondary objective was to examine the accuracy of phenotypic identifications based on a simplified suite of characters examined in the field. Fish were genotyped with 16 microsatellite DNA markers, and results indicated that at least four, or possibly five, black bass species are involved in introgressive hybridization below MFD. Of 29 fish collected below MFD, 16 were pure Shoal Bass. Six hybrid Shoal Bass included both F1 and backcrosses with non-natives, including Alabama Bass (M. henshalli), Spotted Bass (M. punctulatus), and Smallmouth Bass. Two other genotypes likely represented non-native hybrids with native Chattahoochee Bass (M. chattahoochae). Phenotypic identification resulted in an overall correct classification rate of 0.86 when discerning pure Shoal Bass from all other non-natives and hybrids. Results suggest that continued supplemental stocking coupled with selective removal of non-natives and hybrids, which appears to be practical with phenotypic identification, may provide increased benefit towards conserving a genetically-pure Shoal Bass fishery below MFD.