TERRESTRIAL AND BENTHIC FOODS IN THE DIET OF THE SHORTJAWED KOKOPU, GALAXIAS-POSTVECTIS CLARKE (TELEOSTEI, GALAXIIDAE)

Shortjawed kokopu from diverse localities feed extensively on several species of cased caddisflies from the stream benthos and on diverse te rrestrial invertebrates from the surface. Small caddisflies often domi nate the diet numerically and are selected for, whereas other often ab undant benthic insects, such as Chironomidae and the mayfly Deleatidiu m, are avoided. We hypothesise that this selectivity indicates that ca ddisflies are taken by grazing the benthos rather than from the invert ebrate 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 proport ion of the material assimilated from the diet is of terrestrial origin .