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Effect of Localized Prey Depletion on Prey Selectivity by Fish
Author(s) -
Wetterer James K.
Publication year - 1988
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1988)117<0313:eolpdo>2.3.co;2
Subject(s) - predation , lepomis macrochirus , foraging , biology , daphnia , optimal foraging theory , fish <actinopterygii> , functional response , ecology , zoology , predator , fishery , zooplankton
I compared the prey consumption by bluegills Lepomis macrochirus feeding on two size‐classes of Daphnia magna with the diets predicted by the apparent‐size model of foraging. The diets of fish that were acclimated to the laboratory for only 1 or 2 weeks contained significantly more small prey than predicted, but the diets of fish acclimated to the laboratory for over 3 months were consistent with the predictions of the model. The less‐acclimated fish fed closely together and mostly near the center of the arena. This localized feeding quickly depleted almost all the large prey from this area but left the large prey in other areas relatively untouched. The occurrence of localized feeding violated an assumption of the apparent‐size model that all prey were distributed randomly throughout the foraging bout. The results of trials with poorly acclimated fish, therefore, could not be used to test the predictions of the model. The reduced feeding rate and prey selectivity in response to perceived risk, however, have important ecological implications.