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In Situ Observations of Bluegill (Lepomis macrochirus Raf.) Foraging Behavior: The Effects of Habitat Complexity, Group Size, and Predators
Mark J. Butler, IV
Vol. 1988, No. 4 (Dec. 28, 1988), pp. 939-944
Stable URL: http://www.jstor.org/stable/1445717
Page Count: 6
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Using diver observations, interactions among habitat complexity, predator presence, prey group (shoal) size, and prey foraging behavior were related to the abundance and foraging behavior of bluegill sunfish. Evidence for a predator effect on local bluegill abundance and foraging was weak, as was evidence for an interaction between predator presence and bluegill abundance in structurally simple vs complex habitats. However, large bluegill size classes (>50 mm), which are less susceptible to predation, were more common in observations than small bluegill. High plant densities were significantly associated with greater bluegill abundance. The largest bluegill shoals were observed in areas of moderate plant density and the smallest in dense vegetation, but most bluegill travelled alone or in pairs. Bluegill foraging intensity was not significantly affected by shoal size, but was greatest in shoals of four and eight fish. The results of this study largely corroborate earlier laboratory findings, though the proximal effect of predator presence on bluegill behavior may have been previously overestimated, particularly when the natural range of bluegill size classes is examined. In the field, prey may not respond to predators as dramatically as they do in the laboratory where interactions may be artificial and designed to maximize behavioral responses.