Impacts of Aquatic Vegetation Management on the Ecology of Small Impoundments
Knight, Trevor J.
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Aquatic vegetation management and fisheries management are inseparable, however conflicts are often perceived between the two. We investigated the impact of biological, chemical, and no vegetation control on the ecology of private impoundments stocked with largemouth bass and bluegill sunfish. The primary purpose of this study was to determine if aquatic vegetation management had significant impact on pond ecology. A secondary purpose of this study was to collect data for a separate descriptive study on the impact of vegetation management on plankton populations. Nine 0.10 acre ponds were obtained at the Aquaculture Research and Teaching Facility of Texas A and M University in the fall of 2005. Southern naiad (Najas guadalupenis) was transplanted into each pond at a stocking rate of one ton per surface acre. One of three treatments was then randomly assigned to each pond. The treatments were replicated three times and consisted of: an herbicide treatment using Reward and Cutrine, a triploid grass carp treatment, and a control treatment. Fathead minnows (Pimephales promelas), bluegills (Lepomis macrochirus), and largemouth bass (Micropterus salmoides) fingerlings were stocked in each pond. The treatments were initiated on May 31, 2006. Prior to the initiation of the treatments, sampling of each pond occurred for hardness, total phosphorus, nitrite, nitrate, ammonia-nitrogen, dissolved oxygen, turbidity, pH, and temperature. Macroinvertebrate samples were collected from each pond. Post-treatment sampling was conducted on the herbicide treatment and the control at day 2, day 7, day 14, day 28, and monthly thereafter. Posttreatment sampling on the triploid grass carp treatment was conducted at day 14, day 28, and monthly thereafter. One-way ANOVA tests were conducted on the data using SPSS 15.0, and multivariate analysis was conducted using CANOCO software. Significant differences between treatments were found for the parameters turbidity, macrophyte percent coverage, macroinvertebrate species richness, largemouth bass mean weight, and largemouth mean length. Herbicide application and grass scarp stocking significantly decreased the percent coverage of macrophytes in the ponds. Turbidity was significantly increased in the herbicide and grass carp treatments. Largemouth bass mean weight and length were significantly higher in the grass carp ponds. No significant relationships were found in the multivariate analysis; however, there appeared to be several trends within the multivariate analysis that provide insight into potential ecological relationships between the various parameters. The results of this study provide great insight into the impact that various aquatic vegetation management strategies have on the ecology of small impoundments and will help private pond owners and managers conduct better pond management when dealing with aquatic vegetation problems.