Individual specialization and trophic adaptability of northern pike (Esox lucius): an isotope and dietary analysis |
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Authors: | Catherine P Beaudoin William M Tonn Ellie E Prepas Leonard I Wassenaar |
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Institution: | (1) Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada e-mail: bill.tonn@ualberta.ca, Fax: +1-780-4929234, CA;(2) Environment Canada, National Water Research Institute, 11 Innovation Blvd, Saskatoon, SK, S7N 3H5, Canada, CA |
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Abstract: | Northern pike (Esox lucius) are often considered to be specialist piscivores, but under some circumstances will continue to eat invertebrates as adults.
To examine effects of fish assemblage composition on the trophic ecology of pike, we combined stable isotope analysis (SIA)
of carbon and nitrogen and stomach content analysis (SCA) on pike from five lakes in northern Alberta, three of which contain
only pike (“pike-only”) and two that also contain yellow perch (Perca flavescens) or white sucker (Catostomus commersoni) (“pike-other”). Fish were more important as prey and empty stomachs, which often characterize piscivores, were significantly
more frequent in pike-other than in pike-only lakes. However, even though invertebrates were more important for pike in pike-only
lakes, SIA and SCA indicated that invertebrates were also an important component of pike diets in pike-other lakes. SIA and
SCA also revealed considerable intrapopulation variation in trophic ecology, with individuals in some populations differing
by as much as two trophic levels. Comparisons of stomach contents and isotope signatures of the same fish suggested that within
these variable populations, specialization on invertebrates or fish was a long-term trait of some individuals. SIA indicated
that trophic position increased and diets shifted to a greater importance of littoral prey as pike grew in pike-only lakes,
but not in lakes with other fish present. Trophic adaptability in northern pike is expressed at both the population level,
where the trophic ecology is sensitive to differences in prey regimes, and at the organismal level, in the form of intrapopulation
variation and individual specialization.
Received: 1 July 1998 / Accepted: 3 February 1999 |
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Keywords: | Esox lucius Individual variation Stable isotope analysis Stomach content analysis Trophic adaptability |
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