Juvenile inanga (G. maculatus) were caught by seine nets in Canterbury streams, placed in plastic containers filled with water from the stream and then transported to the aquarium facility at the University of Canterbury, Christchurch, New Zealand. The fish were left to acclimate to captivity for a minimum of three weeks. During this period they were maintained in a 500-l aquarium (fish density ~ 2.4 kg/m3), in flowing freshwater (17 mOsm kg− 1, 315–330 μM Na+, pH 6.8–7.2), at 14 °C on a 12:12 day:night cycle. Fish were fed ad libitum on commercial flake food (Nutrafin®Max, Hagen). Food was withheld for two days before the start of the experiments.