New Zealand Journal of Marine and Freshwater Research abstracts
Short communication
Diel patterns of feeding and prey selection in giant kokopu (Galaxias
argenteus)
Eric A. Hansen
Department of Zoology
University of Otago
P.O. Box 56
Dunedin, New Zealand
email: haner436@student.otago.ac.nz
Bruno O. David
Department of Conservation
P.O. Box 842
Whangerei, New Zealand
email: bdavid@doc.govt.nz
Gerard P. Closs
Department of Zoology
University of Otago
P.O. Box 56
Dunedin, New Zealand
email: gerry.closs@stonebow.otago.ac.nz
Abstract We examined diel variation in prey selection
by giant kokopu, Galaxias argenteus, in relation to diel variation
in the abundance of drifting invertebrates in a second order stream in Otago,
New Zealand in summer. Clear differences in both the quantity and composition
of prey consumed was evident. Greater numbers of aquatic insects were consumed
at night relative to the day, whereas more terrestrial insects were consumed
by day relative to the night. Giant kokopu were selective in the prey consumed.
Trichoptera dominated giant kokopu diet at night even though drift samples
collected at night were dominated by Deleatidium mayflies. Results
suggest that giant kokopu feed actively during night and day in summer, and
that prey selection is influenced by interactions between factors including
prey availability, prey characteristics and light.
Keywords giant kokopu; diel activity; drift; feeding
selectivity
M03075; Received 3 November 2003; accepted 26 January 2004; Online publication
date 8 June 2004
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38:
341-345
0028-8330/04/3802-0341 © The Royal Society of New Zealand 2004
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