1Cooperative Research Centre for Freshwater Ecology, Department of Environmental Management & Ecology, La Trobe University, Wodonga 3689, Victoria, Australia
2Cooperative Research Centre for Freshwater Ecology, Murray-Darling Freshwater Research Centre, Lower Basin Laboratory, Mildura 3502, Victoria, Australia
3Current address: Parks, Conservation and Lands, Territory and Municipal Services, GPO Box 158, Canberra, ACT, 2601, Australia; Email: brendan.ebner@act.gov.au
Time required for adult Australian smelt Retropinna semoni, to digest a meal of Daphnia carinata (10 prey items) was found to depend on temperature and feeding frequency based on sacrificial experiments in aquaria. At 10oC, 20oC and 30oC, complete digestion occurred by 5 hr, 1 hr and 2 hr, respectively. This highlights an important functional difference among dietary samples collected in the field at different times of year and is likely applicable to many temperate fishes as poikilotherms. Also, an initial meal of ten D. carinata was digested more slowly (2 hr v 1 hr) if after its ingestion, Australian smelt continued to feed on copepods, as opposed to if additional feeding was prevented, at 20oC. Collectively, these results provide an empirical basis for estimating zooplankton consumption by Australian smelt.
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