Genetic Integrity and Population Status of Shoal Bass in the Upper Chattahoochee River Basin, Georgia Andrew T. Taylor and James M. Long Contact: [email protected]

Introduction Objectives Results (cont.)

Background For all 3 UCRB populations Big Creek Population Size 1. Assess genetic integrity using 16 microsatellite DNA loci • Phenotypic Shoal Bass abundance varied from 2. Estimate age and mortality with non-lethal scale samples 219–348 fish from May 2014 to May 2016 3. Examine variables influencing recruitment • 78% of tagged fish were aged 0–2 years old, indicating very few reproductive adults For Big Creek population 1. Estimate population size with mark-recapture surveys Big Creek Adult Movements 2. Characterize adult movements with ultrasonic telemetry • Adults occupied shoals from May (spawning) • The Shoal Bass (Micropterus cataractae) is a tags and stationary receivers through late August, then occupied areas near the popular sportfish endemic to the Apalachicola- river confluence through winter Chattahoochee-Flint Basin of the southeastern US • Shoal Bass require flowing water and rocky, shoal Results habitats to complete their life cycle, but extensive Genetic Integrity damming has led to habitat fragmentation and loss • 76% of fish in Big Creek • Non-native black basses (e.g., Smallmouth Bass) were hybrids with non- have also been introduced into the area, native Smallmouth Bass threatening Shoal Bass via hybridization • Few hybrids with non-native Alabama Bass detected in all • Unfortunately, few population assessments exist to three populations inform management and conservation efforts • Effective population size estimates for pure Shoal Bass in both rivers (combined) ranged from 94–198, suggesting Study Area short-term stability but risk of losing adaptive potential • We focused on three isolated populations of Shoal Bass in the Upper Chattahoochee River Basin Age and Mortality (UCRB), Georgia • Fish were aged 1–12 years in all populations • Big Creek • Chestatee River • Annual mortality was estimated at 18–24% in all • Chattahoochee River (above Lake Lanier) populations, which is markedly lower than 40–69% Multi-agency sampling teams estimated in southerly portions of the species’ range • Big Creek is were vital to project success the most Recruitment urbanized, and • Year class strength was most variable in Big Creek the population • Recruitment variability in Big Creek was positively related to Discussion is presumably variability in summer discharge, suggesting that flashy, limited to 2 km sediment-laden streamflows reduced age-0 survival Chestatee and Chattahoochee rivers between an Appear to be the last strongholds for Shoal Bass in upstream mill the UCRB. Monitoring of hybridization is needed. dam and the Big Creek

confluence with (Lake Lanier creates cold, tailwater habitat downstream) At risk of extirpation because of introgression, the thermally- ≠ recruitment variability, and low adult abundance. depressed Immediate supplemental stocking and non-native mainstem removals could help conserve this population.

Background image: shoals of the Chestatee River (site 2 on study area map)