New Zealand Journal of Marine and Freshwater Research abstracts
M00031Received 21 June 2000; accepted 21 September 2000
Short communication
Effects of turbidity on the migration of juvenile banded kokopu
(Galaxias fasciatus) in a natural stream
JODY RICHARDSON
DAVID K. ROWE
JOSHUA P. SMITH
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 11 115
Hamilton, New Zealand
email: j.richardson@niwa.cri.nz
Abstract Laboratory experiments have shown that the juvenile
migratory stage of banded kokopu (
Galaxias fasciatus (Gray 1842)) is
more sensitive to turbidity than other native fish species and avoids turbidity
levels of >25 nephelometric turbidity units (NTU). Field trials using
juvenile fish collected from the Tarawera River and Hays Stream, New Zealand,
were used to test the results from these laboratory experiments by measuring
the effects of turbidity on the migration direction and rate for banded kokopu
in a natural stream setting. In the stream setting, neither the migration rate
nor the migration direction were affected at turbidity <25 NTU. At higher
turbidity levels, significantly fewer fish migrated up stream within a given
time period. Because there was rarely any downstream movement, this suggests
the fish either halted or slowed their upstream movement. A slower rate of
migration could result in fewer juveniles reaching adult habitat, and would
account for the reduced abundance of adult banded kokopu in rivers that are
turbid during the migration season. Achieving turbidity levels of <25 NTU in
rivers and streams during the migration season would therefore help maintain
upstream migrations and populations of banded kokopu, and hence other native
fish species.
Keywords turbidity; suspended solids; migration; Galaxias
fasciatus
New Zealand Journal of Marine and Freshwater Research, 2001, Vol. 35: 191-196
0028-8330/01/3501-0191 $7.00 (c) The Royal Society of New Zealand 2001
PDF file of entire paper: medium quality (956K); (scanned from paper original: notes about this process)
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