Drift and upstream movement in Yuccabine Creek,an Australian tropical stream |
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Authors: | L J Benson R G Pearson |
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Institution: | (1) Zoology Department, James Cook University of North Queensland, 4811 Townsville, Queensland, Australia |
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Abstract: | Drift and upstream movement were monitored over 14 months in a seasonal upland tropical stream in northeastern Australia.
There were distinct seasonal pulses in the drift with variable peak levels in the summer wet season and low more stable levels
during the dry season. Drift density ranged from 0.36 to 3.98 animals per m3 (monthly mean = 1.26). There was no correlation between drift density and either benthic density or stream discharge. In
the absence of catastrophic drift, drift was dispersive, not depletive in the wet season. A total of 121 taxa were caught
in the 14 drift samples. Most taxa had nocturnal maximum drift levels with a peak immediately after sunset, a pattern apparently
related to level of light and not temperature. Compensation for drift by upstream-moving nymphs and larvae was least during
the wet season and increased during the dry season to a peak of 27% by numbers. Mean compensation was 8.2%. It is suggested
that apart from in the wet season when an animal may drift substantial distances, most riffle animals will spend their larval
lives in one small stretch of stream. |
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Keywords: | drift upstream movement macroinvertebrates streams tropics Australia |
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