Population characteristics of largemouth bass associated with changes in abundance of submersed aquatic vegetation in Lake Seminole, Georgia

Population characteristics of largemouth bass (Micropterus salmoides L.) including growth, body condition (relative weight), survival, and egg production were examined in relation to abundance of submersed aquatic vegetation (SAV) coverage (primarily hydrilla [Hydrilla verticillata L.f. Royle]) in three embayments of Lake Seminole, GA, and compared to a previous study conducted in 1998. Hydrilla in the Spring Creek arm was reduced by a drip-delivery fluridone (1-methyl- 3-phenyl-5-[3-(trifluoromethyl) phenyl]-4(1H)-pyridinone) system beginning in May 2000; total SAV coverage declined from 76% to 22% between 2000 and 2001. In contrast, SAV in the Flint River arm increased slightly from 1997 to 2000 (32% to 40%) then declined again in 2001 (28%). Plant coverage in the Chattahoochee River arm remained similar between 1997 and 2000 (26%) and declined in 2001 (15%). Following hydrilla reduction in Spring Creek, relative weight increased 3% to 7% between 1998 and 2003 for two of four length groups of largemouth bass. In the other two reservoir arms relative weight either declined or remained the same between the time periods. Growth of age 1-3 largemouth bass was higher in Spring Creek than in the other embayments and time to reach 305 mm and 406 mm decreased by 17% and 33%, respectively, between 1998 and 2003. Time to reach 305 mm and 406 mm remained similar between 1998 and 2003 in the Chattahoochee River arm but declined by 19% and 11%, respectively, in the Flint River arm. Mean annual survival of largemouth bass declined 21% to 23% in all three reservoir arms of Lake Seminole between 1998 and 2003. With faster growth, egg production of largemouth bass doubled in Spring Creek after the SAV reduction; whereas, egg production increased 65% between 1998 and 2003 in the Chattahoochee River and increased only 33% in the Flint River, which was lowest among embayments in 2003. The large reduction of hydrilla in Spring Creek was associated with faster growth, higher relative weights, greater egg production, and lower survival for largemouth bass. However, survival declined throughout Lake Seminole; thus, reduced survival in Spring Creek was likely not related to the fluridone treatment. Abundance of SAV continues to be a strong structuring factor influencing largemouth bass population characteristics in Lake Seminole. Our study demonstrated initial benefits in growth and condition of largemouth bass can result from large-scale removal of SAV in heavily vegetated reservoir systems.