Abstract
Maintaining beneficial, native plant structure and diversity while reducing invasive, nuisance species dominance is an important management domain for natural resource managers. One such vegetation component in North American lakes and reservoirs is submerged aquatic vegetation—a valuable aquatic resource which serves as productive habitat for fish, aquatic macroinvertebrates, and other wildlife. Reservoirs in the southern parts of the United States have experienced varying aquatic plant dominance dynamics due to historical water resource management actions, including drawdowns and introduction of herbivorous fish for the purpose of controlling invasive aquatic vegetation. Some of these management options have also been detrimental to native submerged aquatic vegetation. This paper explores an adaptive management research effort by installing herbivore-protected, fenced-pen submerged aquatic vegetation sites in a high-herbivore reservoir to determine effectiveness of protecting habitat and serving as founder colony sources for propagule spread. Four experimental sites with three management treatments each were planted with American eelgrass. Each site utilized one un-fenced treatment and two treatments with varying mesh sizes for protective fencing-pens. Site integrity, species survival and spread, and grazing were documented. One additional site was installed and planted with other native submerged aquatic vegetation species for nominal species performance descriptions. No plants survived unprotected in the high-herbivore system and plants, in general, performed consistently better within the smaller mesh size. These test planting results were ultimately used to inform adaptive management decision making for plant installation and expansion designs for managing reservoirs invested with Hydrilla, considered one of the most serious invasive aquatic plants in the United States.
Highlights
Establishing native submerged aquatic vegetation in the presence of substantial herbivore densities can be difficult [1]
We observed small basking turtles navigating through the larger mesh size on multiple occasions, but no such incursions were observed through 5 × 5 cm mesh
Monitoring and maintenance are required for long-term submerged aquatic vegetation (SAV) establishment and are being continued in Lake Austin past the initial installation/expansion phases
Summary
Establishing native submerged aquatic vegetation in the presence of substantial herbivore densities can be difficult [1]. Red-eared sliders (Trachemys scripta elegans) prefer to feed on American eelgrass (Vallisneria americana), a commonly utilized submerged aquatic vegetation species for restoration in southern United States (U.S.) reservoirs, making them an obstacle in re-establishing eelgrass [2] [3] [4]. This dynamic is compounded when new herbivores, such as triploid grass carp (Ctenopharyngodon idella), are released into systems for management of invasive submerged aquatic vegetation, such as hydrilla (Hydrilla verticillata) [5] [6] [7].
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