An Integrated Approach to Managing Aquatic Plants at Lake Jacksonville, Texas

Richard A. Ott, Jr.
Texas Parks & Wildlife Department - Inland Fisheries 11942 FM 848 Tyler, Texas 75707

Michael Smart
USAE Waterways Experiment Station Lewisville Aquatic Ecosystem Research Facility RR 3 Box 446 Lewisville, TX 75056

Key words: hydrilla control, plant introduction, fish habitat, grass carp, macrophytes

We developed an integrated management plan to control 48 ha of hydrilla (Hydrilla verticillata) on Lake Jacksonville, Texas (a 547 ha municipal water-supply reservoir). Our objective was to control a problematic, invasive, exotic plant while increasing coverage and community diversity of native plants for fish habitat. Our plan was to reduce hydrilla biomass with aquatic herbicide, stock a minimal number of grass carp (Ctenopharyngodon idella) to control re-sprouting, and introduce a diverse native plant community. Hydrilla was treated with Aquathol K Ô in spring 1997 and 1998 followed by stocking 100 grass carp each year. Following each treatment, native plants representing floating-leafed, emergent, and submersed growth forms were planted in protective cages (to limit herbivory). In fall 1998 hydrilla was found only in cages where native plant survival was low. Herbivores appeared to be selectively removing hydrilla from the plant community outside of the cages where it had been observed in summer. Despite drought and low water conditions in 1998, many of the native plant species survived through fall 1999 and are expanding beyond the protective cages. These preliminary results indicate that an integrated approach has the potential to control hydrilla while promoting diversity of the native plant community.