Influence of shade and artificial vegetation on the avoidance responses of bluegills (Lepomis macrochirus) in the presence of largemouth bass (Micropterus salmoides)

Includes bibliographical references (pages [59]-62)This research addressed how juvenile bluegills (Lepomis macrochirus) may use shaded water, vegetation, and shaded vegetation as possible refuges from largemouth bass (Micropterus salmoides) and how light intensity may influence bluegills? use of vegetation. Three experiments were conducted. The first experiment was designed to address if juvenile bluegills use shaded water as a refuge from a largemouth bass. I used two half-shaded wading pools, one without a bass present and one with a bass present. The second experiment was designed to address how bluegills use artificial vegetation and shade as a refuge from a largemouth bass. I used two wading pools divided into shaded/vegetated, shaded/unvegetated, unshaded/vegetated, and unshaded/unvegetated sections, one pool without a bass present and one with a bass present. Finally, the third experiment was designed to address whether bluegills may alter their use of vegetation at different light intensities. I conducted the experiment in a 220L aquarium at light intensities of 1.5lux, 170lux, and 340lux and in which one half of the aquarium had artificial vegetation. In experiment one, the bluegills used shaded water more than unshaded water when shade was the only refuge available; the presence of a bass did not affect the use of shaded water (greater than 70% for both pools). However, the location of the bass did affect the use of shaded water. An unshaded bass caused the bluegills to use the shaded water almost exclusively (>90%), while a shaded bass decreased the bluegills? use of shade to about 60%. In experiment two, the bluegills used the vegetation greater than 70% of the time, even when open water was partially shaded. Use of shade (within vegetation) by the bluegills was not statistically different between the no bass and bass treatments. In experiments one and two, the bluegills? schooling was consistently low regardless of the presence of shade, vegetation, or bass. In experiment three, the bluegills? use of vegetation differed among light intentsities. The bluegills used the vegetation greater than 50% at 1.5lux and 340lux, but only about 35% at 170lux.M.S. (Master of Science