Limited effects of stocked trout on littoral invertebrates in boreal foothills lakes
Abstract:Stocking lakes with trout for the purposes of recreational angling is a management strategy that introduces a new predator into these systems and thus deserves careful scrutiny. To assess the impact of non-native trout on littoral invertebrates in naturally fish-bearing lakes in the boreal foothills of Alberta, Canada, we compared their community composition, abundance, and size structure in stocked (n = 5) and unstocked (n = 6) lakes over a 2-year period. We detected no clear negative effects of introduced trout on invertebrate community composition and only few taxa-specific examples of decreased or increased invertebrate abundance. Furthermore, predation by trout had inconsistent direct effects on the size structure of invertebrate populations. Indirect effects were suggested by increased abundances and sizes of some invertebrate taxa in stocked lakes and might also contribute to the limited overall differences that we observed. We propose that net effects of stocked trout on littoral invertebrates are influenced by key characteristics of receiving ecosystems. In our boreal foothills lakes, dense macrophyte cover in warm littoral zones, high productivity, abundant forage fish, and limited densities of trout all likely combine to allow littoral invertebrate communities to withstand the impact of introduced trout with minimal effects.
Document Type: Research Article
Affiliations: 1: Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada. 2: Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; and Parks Canada Agency, Western and Northern Service Centre No. 1550, 635-8 Avenue S.W., Calgary, AB T2P 3M3, Canada.
Publication date: January 16, 2012
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