Consequences of Vegetation Density and Prey Species on Spotted Gar Foraging

Abstract

Adult spotted gar Lepisosteus oculatus are potentially important components of food webs given their predatory habits and high relative abundance. However, few studies have examined their foraging behavior. Therefore, we examined the effects of vegetation density on the foraging success of adult spotted gars preying on bluegill Lepomis macrochirus and fathead minnow Pimephales promelas. Spotted gars use ambush foraging and were more successful capturing fathead minnow than bluegills at all stem densities. Predation success was negatively correlated with stem density for bluegill prey but not for fathead minnow. Although fathead minnow and bluegills shoaled less as stem density increased, bluegills modified their behavior in the presence of a predator by moving lower in the water column at high stem densities, whereas fathead minnow did not. Predatory behaviors were directed at prey within a short distance and near the surface of the water. Foraging of spotted gar, a lie-in-wait predator, was primarily influenced by prey behavior, with the amount of vegetative cover playing a secondary role that also varies with prey species.