Population Dynamics of Introduced Flathead Catfish in Rivers of Southern Georgia
Adam J. Kaeser, Timothy F. Bonvechio, Donald Harrison, and Robert R. Weller
Abstract.—The flathead catfish Pylodictis olivaris is a widely successful invader of lotic ecosystems across North America. The ability of flathead catfish to grow quickly to large sizes while preying upon native fish has caused concern and spurred aggressive measures to control introduced populations in states like Georgia. Although studies have examined differences among native and introduced populations with respect to demographic factors such as age, growth, and mortality, little is known of introduced population dynamics over the long term. As a unique opportunity to improve our understanding of the trajectory and fate of introduced flathead catfish populations, we examined temporal dynamics within some of the oldest (30+ years), introduced populations in the southeastern United States, those of the Flint River and Altamaha River systems of Georgia. Flathead catfish abundance (both density and biomass) was substantially (71–88%) lower among populations recently examined relative to historical observations. A comparison of modeled growth indicated that individual growth rates of flathead catfish were also lower among contemporary populations than among those previously observed. Monitoring of relative abundance over a 22-year period in the Altamaha River revealed a distinct and recurrent population boom and decline, suggesting that equilibrium abundance of flathead catfish has either not been reached or will remain dynamic in the future in this system. Changes in the population demographics of introduced populations occurred rapidly, within a matter of years, and represented striking shifts in the abundance of flathead catfish populations in southern Georgia. An investigation of factors associated with such dynamics and their ecological consequences remain important areas for future research.