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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Community Ecology
BENTHIC INVERTEBRATE COMMUNITIES IN TROUT AND TROUTLESS LAKES IN NEW ZEALAND.
S.A. Wissinger1,2 and A.R. McIntosh2. 1Biology Department, Allegheny College, Meadville, PA 16433 USA, 2Department of Zoology, University of Canterbury, Christchurch, New Zealand
The effects of introduced trout on benthic invertebrate communities in New Zealand lakes were investigated by comparing the relative abundance and species composition in lakes with 1) trout and native fish (galaxiids, bullies, eels), 2) native fish only, and 3) no fish. Multivariate analysis of presence-absence data from lakes in the central mountains of the South Island suggested that invertebrate communities with trout were indistinguishable from those without. Every benthic invertebrate species encountered in troutless permanent lakes was also present in one or more lakes with trout, including a number of large bodied taxa (e.g., Odonata, Trichoptera, Hemiptera) that were hypothesized to be most vulnerable to trout predation. Quantitative samples from a subset of the lakes revealed major differences in the overall and relative abundance of invertebrates among microhabitats within lakes, but not between trout and troutless lakes. In all lakes, large bodied taxa were more abundant in littoral emergent vegetation and/or in offshore beds of submergent macrophytes than in non-vegetated benthic habitats. Not all lakes have littoral emergent zones, but most have extensive beds of emergent vegetation that could provide a refuge from fish predators, thus explaining the apparently minimal effects of trout introduction on benthic invertebrates.
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