Investigating the Effects of Urban Watershed Hydrology on Hybridization Rates

The southeastern United States is a global hotspot for freshwater fish diversity, with over 250 species occurring in Georgia alone. Unfortunately, damming and habitat fragmentation has caused many species in this region to become imperiled or suffer loss of genetic diversity. This project focuses on a remnant population of Shoal Bass (Micropterus cataractae) within a 2 km section of Big Creek, a tributary of the Chattahoochee River basin. Shoal Bass previously inhabited the length of Big Creek, but populations have become limited upstream by Roswell Mill Dam and downstream by cold water releases from Buford Dam into the Chattahoochee River. The Big Creek watershed has become increasingly urbanized due to the expansion of metropolitan Atlanta, resulting in increased sediment deposition and rapid changes in streamflow. In addition to these factors, non-native generalist species such as the Smallmouth Bass (Micropterus dolomieu) and the Alabama Bass (Micropterus henshalli) are invading Big Creek from the colder waters of the Chattahoochee River, resulting in hybridization with Shoal Bass. To better understand the status of the Shoal Bass population, our objectives are to: 1) characterize annual trends in hybridization among Shoal Bass and non-native basses; and 2) investigate how hybridization rates may be influenced by the urban watershed hydrology of Big Creek. Our results could inform conservation efforts and encourage improved urban watershed management to protect the genetic integrity of the Shoal Bass population in Big Creek.