By Lindsay Gardner and Dr. Steve Sammons
Native shoal bass in Georgia and Alabama, one of the eight described black bass species in the United States, are facing serious threats to their habitats and the integrity of the species. Dr. Steve Sammons of the Fisheries Department at Auburn University, who has studied shoal bass populations extensively, calls this situation “a war of attrition”, with numbers of shoal bass populations threatened by a variety of factors, including dams and flow alterations, land use changes, and competition from illegal introductions of black bass not native to the range of the shoal bass. Further evaluation of the life history of shoal bass, including habitat requirements and availability of and competition for food sources, is critical to developing a conservation strategy that will prevent further extirpation (elimination from its former range) of populations.
Shoal bass are endemic to the Apalachicola Basin and are considered fluvial specialists, meaning they require rivers and streams to survive. They are typically found in rocky habitats with strong current, referred to as “shoals”, and do not withstand impoundment. Harold Hurst was probably one of the first biologists to study shoal bass in the Chattahoochee River tributary streams in Alabama, during his Master’s work at Auburn University in the late 1960s. Forty years later, a team of researchers, led first by Dr. Mike Maceina and currently by Dr. Steve Sammons, returned to these streams to see how shoal bass were faring. What they found was a shocking wake-up call. While populations of native shoal bass and largemouth bass, along with non-native spotted bass were still distributed throughout the mainstem of the Chattahoochee River, there had been marked shifts in the types of black bass found in some of the smaller creeks, with notable declines in the numbers of shoal bass. Shoal bass had been virtually eliminated from three of the four streams in Alabama that had historically had these fish and were replaced by non-native spotted bass. In the last remaining population found in the state, located in a 600-meter stretch of shoal habitat at Moffits Mill on Little Uchee Creek, there was an 80% reduction in the estimated population of shoal bass from 2005 to 2007, mostly due to persistent drought conditions that almost completely desiccated the creek. Currently, there are likely fewer than 100 adult shoal bass found in Alabama.
Several key factors have contributed to shoal bass population declines and have likely benefitted spotted bass, the shoal bass’s main competitor for food and habitat. Dams along the Chattahoochee create impoundments and restrict movement among main-channel habitats and between tributaries and main channel habitats. Dr. Sammons and his team recently completed a one-year telemetry study in a shoal bass population below a low head dam in the headwaters of Bartletts Ferry Reservoir. Results from this study demonstrated that shoal bass movement was not only restricted upstream by the dam, but also downstream by the reservoir. No fish during the nine-month study were found below the area where noticeable flow ceased and reservoir conditions began, despite the fact that multiple streams that formerly had shoal bass populations flowed into the reservoir. This restricted movement has the potential to isolate populations and potentially affect gene flow. Also, work by Dr. Sammons on the undammed portion of the Flint River in Georgia, has revealed that shoal bass typically make long migrations upstream and downstream to preferred spawning shoals. Thus the series of dams on the Chattahoochee River has broken up the formerly large meta-population of shoal bass into an
unconnected group of isolated populations. Also, because shoal bass will not move into reservoir habitats, they have eliminated a drought refugia for these fishes. Both of these factors make these populations more vulnerable to local extinctions, as has occurred in the Alabama tributary streams. Similarly, land use changes, associated with development, especially in Alabama, have taken a toll on shoal bass populations. However, spotted bass may not have been adversely impacted by all of these alterations in habitat, as they are an adaptable species that can be found in small creeks, larger rivers, or in reservoirs. Furthermore, spotted bass pose a genetic threat to the remaining shoal bass populations, as hybrids and genetic mixing of spotted bass and both shoal bass and largemouth bass have been found throughout the Apalachicola Basin. Spotted bass have been illegally introduced into almost every drainage in Georgia, except areas in the extreme southeast and southwest. The long-term genetic effects of these introductions on the native black bass communities are unknown.
AU’s work is part of a SARP-supported Native Black Bass Initiative, which has been accepted by the National Fish and Wildlife Foundation as a Keystone Initiative. This initiative was intended to promote and fund efforts to conserve native black bass and their riverine habitats throughout the Southeast. Other key partners include Georgia Department of Natural Resources, Alabama Wildlife & Freshwater Fisheries, Florida Fish and Wildlife Commission, Georgia Power Company, GeorgiaRiverFishing.com, the Flint Riverkeeper organization, the Chattahoochee RiverWarden organization, and the Department of Fisheries and Allied Aquacultures at Auburn University. It is hoped that the data collected on shoal bass will help fisheries biologists, conservationists and recreational anglers put measures in place that will help the shoal bass populations of Georgia, Alabama, and potentially beyond, to not only survive, but thrive.
For more information about shoal bass and the Native Black Bass Initiative, contact Dr. Steve Sammons, at firstname.lastname@example.org or by phone at (334) 844-4159.