The Role of Aquatic Macrophytes in Mediating Predation Risk of Juvenile Largemouth Bass

Managers frequently invest considerable resources to establish native aquatic vegetation in aging reservoirs, typically with the goal of increasing recruitment of sport fishes (particularly largemouth bass). Submersed macrophytes provide structural complexity that produces a refuge and reduces predation mortality for some prey (i.e., bluegill). However, little is known about whether vegetation increases juvenile largemouth bass survival. Therefore, the objective of this study was to examine the effect of aquatic vegetation on survival of juvenile largemouth bass when exposed to predation. Aquatic vegetation was planted on one-half of a study tank at natural stem densities. A second tank, void of any structure, was used as a control. Videotaped behavioral trials were conducted with one adult largemouth bass and ten juvenile largemouth bass in the same tank. We quantified the time predators spent searching, orienting, and pursuing prey as well as the strike-to-capture ratio and the time the predator and prey spent in open water or vegetation to determine how the presence of vegetation alters predator-prey interactions.  Preliminary observations suggest juvenile largemouth bass may not always utilize vegetation, choosing instead to disperse to escape predation. This was likely a response to adult largemouth bass spending the majority of their time within vegetation.