New Zealand Journal of Marine and Freshwater Research abstracts

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Prey availability and diet of juvenile brown trout (Salmo trutta) in relation to riparian willows (Salix spp.) in three New Zealand streams

P. M. SAGAR
G. J. GLOVA

National Institute of Water & Atmospheric
Research Ltd
P. O. Box 8602, Riccarton
Christchurch, New Zealand

Abstract  Macroinvertebrate benthos and drift and the diet of juvenile brown trout (Salmo trutta) were investigated in willowed and non-willowed sections of three New Zealand streams during summer. The abundance and biomass of the principal macroinvertebrate taxa in the benthos and daytime drift differed in relation to riparian willow (Salix spp.) density, but the trends were not consistent across all three streams. Crustacea, Ephemeroptera, Trichoptera, and Diptera comprised a major proportion of the diet of juvenile trout. Diets of trout from non-willowed and willowed sections were dissimilar in three of five pair-wise comparisons. In all three streams, juvenile trout fed selectively, with the amphipod Paracalliope fluviatilis, ephemeropteran Deleatidium, and trichopterans Aoteapsyche and Hydrobiosidae being the preferred prey. Their avoidance of the gastropod Potamopyrgus antipodarum, trichopteran Oxyethira albiceps, coleopteran Hydora, and drift of terrestrial origin appeared to occur in all streams. Total abundance and biomass of invertebrates drifting during the day described the potential prey available to juvenile brown trout better than did the abundance and biomass of benthic invertebrates.

Keywords  brown trout; macroinvertebrates; drift; benthos; riparian willows; abundance; biomass

New Zealand Journal of Marine and Freshwater Research, 1995: Vol. 29: 527-537

0028-8330/95/2904-0527 $2.50/0 (c) The Royal Society of New Zealand 1995

PDF file of entire paper: medium quality (758K); (scanned from paper original: notes about this process)

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