An experimental study of body size and food size relations in crucian carp,Carassius carassius |
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Authors: | Cynthia A Paszkowski William M Tonn Ismo J Holopainen |
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Institution: | (1) Department of Zoology, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada;(2) Department of Biology, University of Joensuu, P.O. Box 111, SF-80101 Joensuu, Finland |
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Abstract: | Synopsis In dense, single-species assemblages of crucian carp, competition is intense and results in populations of stunted fish. To
explore mechanisms underlying this competition, we measured handling times, return rates, and prey choice for five sizes of
crucian carp feeding on six sizes of a standardized food. Handling times increased with prey size and decreased with fish
size. Return rates (dry mass ingested per unit handling time) increased dramatically with fish size, and generally decreased
with increasing prey size, especially for small fish. Patterns of return rates among size-classes suggested that one or more
size-related shifts in feeding efficiency exist for crucian carp; combined with physiological stresses related to winter anoxia,
the inability of fish to make these shifts may contribute to size structures observed in high-density populations. Comparisons
of relations among fish size, prey size, and return rates for crucian carp and bluegill, Lepomis macrochirus, suggest that similar intraspecific competitive relations exist between generalist species with size-structured populations.
Despite differences in return rates among prey sizes, the extent of food selectivity based on prey size exhibited by crucian
carp in two types of choice trials was less than predicted. Crucian carp commonly take in several items before mechanically
processing food with their pharyngeal apparatus; this multiple prey processing may contribute to disparities between observed
choice patterns and those predicted based on return rates for single prey. |
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Keywords: | Feeding behavior Handling time Intraspecific competition Multiple prey processing Prey choice Stunting Cyprinidae |
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