The Use of Herbicides to Replace Hydrilla with Native Submersed Plants and Impact on Juvenile Largemouth Bass in Lake Seminole
Michael J. Maceina and Jeffery W. Slipke
Department of Fisheries, Aquacultures, and Aquatic Sciences, Auburn University, Auburn, AL

Shortly after impoundment in 1957, many native submersed plant species became established in Lake Seminole, Georgia (13,800 ha). In the early 1980's, the exotic plant hydrilla Hydrilla verticillata was discovered and by 1992, covered nearly 70% of this reservoir eliminating nearly the entire native submersed plant community. From 1997 to 2001, fluridone and endothall based herbicides were used to control hydrilla in treatment plots (< 10 ha). This also resulted in the partial reestablishment of native submersed plants, but at times, hydrilla was not completely eliminated. Typically, the dominant plants that became reestablished included Illinois pondweed Potomogeton illinoensis and stonewort Nitella sp., but coontail Ceratophyllum demersum, southern naiad Najas guadalupensis, and fanwort Cabomba caroliniana, were also found in treatment areas. Herbicide treatments only temporally reduced hydrilla, native plants were displaced by hydrilla unless additional applications were made. Catch-per-unit of effort for both number and weight of age-0 and age-1 largemouth bass sampled for the 1997 to 2000 year-classes were similar or higher in herbicide treated mixed plant areas compared to untreated dense hydrilla infested areas. Aquatic herbicides applied to hydrilla infested regions where a native seedbank existed temporally promoted the growth of native plants and at times, improved juvenile largemouth bass population characteristics. In one cove that has been utilized by adult largemouth bass for spawning, treatments with Aquathol K over three years reestablishment fanwort, and abundance of adult fish nearly doubled over time.