ANNUAL CONTRIBUTION OF TERRESTRIAL INVERTEBRATES TO A NEW-ZEALAND TROUT STREAM

Whole-stream drift from stream reaches enclosed by 1 mm mesh barriers was sampled to estimate the potential contribution of terrestrial inve rtebrates to trout production in a high-country pasture stream in New Zealand. Invertebrates were classified into two activity groups: winge d or wingless. Biomass of winged insects was significantly related to temperature but not discharge. Biomass of wingless invertebrates was n ot related to temperature or discharge; however, abundance was signifi cantly related to discharge but not temperature. These results suggest that mode of entry differed between activity groups. Winged insects a pparently entered the stream as a function of overall activity, wherea s wingless invertebrates entered the stream passively-possibly a-resul t of fluctuations in discharge. An empirical model based on these rela tionships indicated that total input of terrestrial invertebrates may support as much as 5% of annual production by resident brown trout.