New Zealand Journal of Marine and Freshwater Research abstracts

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Terrestrial and benthic foods in the diet of the shortjawed kokopu, Galaxias postvectis Clarke (Teleostei: Galaxiidae)

R. M. McDOWALL

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

M. R. MAIN

Department of Zoology
University of Canterbury
Private Bag
Christchurch, New Zealand

Present address: Canterbury Regional Council, P. O. Box 345, Christchurch

D. W. WEST

Department of Biological Sciences
University of Waikato
Private Bag
Hamilton, New Zealand

Present address: National Institute of Water & Atmospheric Research Ltd, P. O. Box 11-115, Hamilton

G. L. LYON

Institute of Geological and Nuclear Sciences
P. O. Box 31-312
Lower Hutt, New Zealand

Abstract  Shortjawed kokopu from diverse localities feed extensively on several species of cased caddisflies from the stream benthos and on diverse terrestrial invertebrates from the surface. Small caddisflies often dominate the diet numerically and are selected for, whereas other often abundant benthic insects, such as Chironomidae and the mayfly Deleatidium, are avoided. We hypothesise that this selectivity indicates that caddisflies are taken by grazing the benthos rather than from the invertebrate drift. Gravimetrically, large terrestrial invertebrates such as beetles, ants, cicadas, and spiders are more prominent in shortjawed kokopu diet. Stable carbon isotope analysis shows that in Black Creek, a tributary of the Ohinetamatea River, South Westland, a high proportion of the material assimilated from the diet is of terrestrial origin.

Keywords  shortjawed kokopu; Galaxias postvectis; diet; terrestrial foods; stable carbon isotopes; New Zealand

New Zealand Journal of Marine and Freshwater Research, 1996: Vol. 30: 257-269

0028-8330/96/3002-0257 $2.50/0 (c) The Royal Society of New Zealand 1996

PDF file of entire paper: medium quality (1034K); (scanned from paper original: notes about this process)

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