FEEDING ECOLOGY OF AOTEAPSYCHE RARURARU (MCFARLANE) (TRICHOPTERA, HYDROPSYCHIDAE) IN A NEW-ZEALAND LAKE OUTLET

Changes in the quantities of seston (phytoplankton and zooplankton), a nd epilithic algae, and densities of Aoteapsyche raruraru (McFarlane) larvae were investigated over a six month period at three sites 15 m, 25 m, and 250 m below the outlet of Lake Kaniere, Westland, New Zealan d. Phytoplankton abundance varied little between sites, however zoopla nkton densities were highest 25 m below the outlet where the highest h ydropsychid densities were also found. In contrast, epilithic algal bi omass was greatest 250 m below the outlet where the fewest hydropsychi ds were collected. Higher densities and larger larvae were found on th e upper surfaces of stones in faster water (> 0.6 m s(-1)). Net morpho logy also changed as current velocity increased: at slower currents (< 0.2 m s(-1)) 70-80% of larvae had ''sail'' nets with a single jib sup port, whereas at >0.65 m s(-1) more than 80% of larvae had nets with t wo ''goal post'' supports. Glut analysis indicated that larvae in slow er currents had ingested a higher proportion of filamentous algae and diatoms, whereas larvae in faster currents had higher proportions of z ooplankton in their diets. Results of this study indicate that net des ign is influenced by current velocity which influences diet and possib ly growth in the outlet of Lake Kaniere.