Comparison of Native and Introduced Flathead Catfish Populations in Alabama and Georgia: Growth, Mortality, and Management

Abstract

We compared growth of flathead catfish Pylodictis olivaris from two native populations in Alabama (Coosa and Tallapoosa rivers) and two introduced populations in Georgia (Ocmulgee and Satilla rivers). We also compared mortality rates and potential outcomes of various management regimes (minimum length limits [MLLs]) among the populations. Total length–log10(age) regression slopes for introduced fish were higher than those for native fish, and von Bertalanffy growth coefficients (K) were greater for introduced fish (Ocmulgee: 0.195; Satilla: 0.201) than for native individuals (Coosa: 0.057; Tallapoosa: 0.059). Therefore, introduced flathead catfish grew more rapidly than those in their native range. Mortality (instantaneous mortality rate, Z) was higher in the Satilla River population (Z = −0.602) than in the Ocmulgee River (Z = −0.227) and Coosa River (Z = −0.156) populations. However, fish in the Satilla River population had been introduced for only 10 years and presumably did not reach their theoretical maximum age, potentially biasing the mortality estimate for that population. Simulation of management regimes in Fishery Analyses and Simulation Tools software predicted that maximum biomass of flathead catfish in the Ocmulgee (1,668 kg) and Satilla (1,137 kg) rivers was substantially larger than that in the Coosa (873 kg) and Tallapoosa (768 kg) populations. However, increased exploitation rates in the Ocmulgee and Satilla River populations resulted in dramatic declines in overall biomass, especially at lower MLLs (254 and 356 mm, respectively). Therefore, in systems where introduced flathead catfish represent an important recreational fishery but have dramatically reduced the abundance of native fishes through predation, minimal protection is recommended. We contend that rapid growth of introduced flathead catfish has major implications for their management and the conservation of native fishes.

Population dynamics of introduced flathead catfish in Lake Mitchell, South Dakota

“…The only other estimate of annual mortality for a flathead catfish population in lentic waters came from at Lake Wilson, Alabama (17%; Marshall et al 2009), and was lower than for Lake Mitchell. Estimates for lotic populations range from about 12%-36% (Daughtery & Sutton 2005;Kwak et al 2006;Makinster & Paukert 2008;Jolley & Irwin 2011;Kaeser et al 2011), however, values similar to Lake Mitchell were reported for the Missouri River (34%-59%, Gavin's Point Dam to the Kansas-Nebraska border; Goble 2011) and the Satilla River, Georgia (45%; Sakaris et al 2006).…”

Longitudinal patterns in flathead catfish relative abundance and length at age within a large river: effects of an urban gradient

“…Although flathead catfish occur in modified river systems and may be fluvial generalists, these fish were more abundant along natural river banks compared to revetted bank in the Mississippi River (Pennington et al, 1983). Growth of flathead catfish is related to the environment (river or reservoir) or if the population is native or introduced (Kwak et al, 2006;Sakaris et al, 2006). However, little information exists on the variability in growth among reaches or habitats within a river.…”

Maximum Daily Consumption and Specific Daily Metabolic Demand of Juvenile Flathead Catfish (Pylodictis olivaris)

“…Extensively introduced outside its native range (Fuller et at. 1999), the flathead catfish has altered the composition of native fish populations through predation (Pine et al 2005, Sakaris et al 2006, Pine et al 2007). The growth of flathead catfish varies extensively from population to population (Grabowski et al 2004, Kwak et al 2006, but there is a general trend that reservoir residents grow faster than riverine individuals, introduced flathead catfish grow faster than those in native populations, and individuals in eastern United States populations grow more rapidly than those in western populations (Kwak et al 2006).…”