Changes in the quantities of seston (phytoplankton and zooplankton), and 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 Zealand. Phytoplankton abundance varied little between sites, however zooplankton densities were highest 25 m below the outlet where the highest hydropsychid densities were also found. In contrast, epilithic algal biomass was greatest 250 m below the outlet where the fewest hydropsychids were collected. Higher densities and larger larvae were found on the upper surfaces of stones in faster water (> 0.6 m s-1). Net morphology 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 support, whereas at >0.65 m s-1 more than 80% of larvae had nets with two "goal post" supports. Gut analysis indicated that larvae in slower currents had ingested a higher proportion of filamentous algae and diatoms, whereas larvae in faster currents had higher proportions of zooplankton in their diets. Results of this study indicate that net design is influenced by current velocity which influences diet and possibly growth in the outlet of Lake Kaniere.
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