Nocturnal and diurnal feeding by Galaxias auratus, a lentic galaxiid fish

Abstract –  We examined the diel feeding pattern, gastric evacuation and daily ration of a lentic, endemic Tasmanian galaxiid fish, Galaxias auratus . Analysis of stomach contents and consumption estimates based on collections of fish every 3 h over three 24-h periods in summer 2002/2003 revealed that feeding always occurred during both day and night, with no obvious peaks. We also estimated the gastric evacuation rate of G. auratus in a laboratory experiment using the two prey species found to be dominant in stomachs of field-sampled fish. The relationship was best described by an exponential model, with rate parameters ( R ) of 0.104 and 0.081 for the evacuation of the amphipod, Austrochiltonia australis , and the cladoceran, Daphnia carinata , at water temperatures of 11.5 and 16.5 °C, respectively. Daily ration of G. auratus in summer was estimated to be approximately 3% (dry body weight) using the models of Elliot & Persson and Eggers. Galaxias auratus appears to be unusual in that its feeding pattern cannot be classified as nocturnal, diurnal or crepuscular, but its gastric evacuation and daily ration estimates are still similar to other comparable Northern Hemisphere freshwater fishes.