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Presented at the NABS Annual meeting, Athens, Georgia, 2003
in Community Ecology II
Ontogenetic ecology of the signal crayfish, Pacifastacus leniusculus, in a small temperate stream.
C.A. Bondar and J.S. Richardson. Department of Forest Sciences, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
A comprehensive understanding of the ecological role of an organism requires consideration of the ecology of all life history stages. Adult crayfish are consumers of vascular detritus and invertebrate prey, and can affect stream ecosystems through direct and indirect processes. Adult crayfish can have significant effects on organisms on several trophic levels. However, the ecology of juvenile crayfish is not well understood, despite well-documented ontogenetic shifts in feeding preference. We contrasted the role of adult and juvenile signal crayfish (Pacifastacus leniusculus) in a small stream ecosystem in British Columbia, Canada. We manipulated densities and ontogenetic stages of crayfish in enclosures. Results showed that adult and juvenile crayfish had distinct effects on the stream ecosystem. Invertebrate communities inhabiting leaf packs differed between adult and juvenile treatments; however, leaf decomposition rate was not significantly different, suggesting functional compensation among shredding invertebrates. Including crayfish biomass as a covariate did not alter these results, suggesting that overall consumption remained similar despite changes in crayfish density. These results illustrate that different ontogenetic stages of the same organism may be playing different ecological roles in the community. Such alternate roles should be considered in food web analysis and trophic level designation of organisms in freshwater communities.
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