New Zealand Journal of Marine and Freshwater Research abstracts
Effects of turbidity on the feeding ability of the juvenile
migrant stage of six New Zealand freshwater fish species
DAVID K. ROWE
TRACIE L. DEAN
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 11 115
Hamilton, New Zealand
Abstract Laboratory tank experiments were used to determine
the effect of turbidity levels ranging from 0-640 Nephelometric Turbidity Units
(NTU) on mean feeding rates for each species. Mean feeding rates for banded
kokopu (Galaxias fasciatus), smelt (Retropinna retropinna),
inanga (G. maculatus), and common bullies (Gobiomorphus
cotidianus) were all reduced by increased turbidity, but significantly so
only for banded kokopu and inanga. Banded kokopu was the most sensitive species
as feeding rates at 20 NTU were significantly lower than in clear water,
compared with levels over 160 NTU for the other species. Feeding rates for
redfinned bullies (Gobiomorphus huttoni) increased with turbidity up to
40 NTU then decreased. Reductions in feeding rate at elevated turbidity levels
were the result of a reduced inability to feed, rather than to stress, as
exposure to the highest turbidity level did not reduce feeding motivation or
appetite. Feeding tests in the dark indicated that, whereas vision was
important for feeding by all species, banded kokopu and common bullies had a
comparatively well-developed ability to feed using non-visual senses.
Non-visual feeding may have reduced the impact of high turbidity levels on
feeding for these two species, and could confound attempts to determine the
effects of turbidity on visual feeding on live prey.
Keywords whitebait; diadromous fish; river mouths; suspended
solids; feeding rate; NTU; non-visual feeding
New Zealand Journal of Marine and Freshwater Research, 1998, Vol. 32:
21-29
0028-8330/98/3201-0021 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (822K); (scanned from paper original: notes about this process)
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