Predation risk and feeding patterns of crucian carp |
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Authors: | C A Paszkowski O-P Penttinen † I J Holopainen † W M Tonn |
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Institution: | Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9;Department of Biology, University of Joensuu, SF-80101 Joensuu, Finland |
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Abstract: | As part of an experimental study of the direct and indirect effects of piscivory on prey fish, the diets of crucian carp Carassius carassius were compared across sections of a divided pond; two sections were stocked with crucian carp alone and two with crucian carp plus perch Perca fluviatilis . Analysis of crucian gut contents indicated that the composition of invertebrate prey did not differ in the presence v . absence of perch. However, crucians, particularly small individuals (<10cm) that were most vulnerable to predation, displayed a lower intake of invertebrate prey in sections with perch. Although diet composition differed between crucians caught in inshore v. offshore habitats (with habitat use being related to crucian size and the presence or absence of perch), no clear pattern existed between habitat and total food intake. Overall, the major effects of predators on the diet of crucian carp appeared to be caused by increased ecological density (resulting from confinement of small crucians inshore) and reduced activity levels, rather than simple shifts to safer habitats. |
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Keywords: | indirect effects of predation Carassius carassius Perca fluviatilis diet body size habitat use |
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