FEEDING-HABITS OF HATCHERY-REARED BARRAMUNDI LATES-CALCARIFER (BLOCH) FRY

Hatchery-reared barramundi Lates calcarifer fry were studied to determine feeding behaviour, diel feeding patterns, stomach evacuation rates, daily food consumption and growth rates. At 16-18 mm total length, the feeding behaviour of the fry changed abruptly from a roving zooplanktivore habit to that of a lurking predator. A distinct change in pigmentation accompanied the change in feeding behaviour. Fry reared in hatchery ponds were obligate zooplanktivores between 10 and 17 mm. Between 17 and 50 mm the diet changed progressively from zooplankton to insect larvae and small vertebrates. The fry were visual feeders, taking food throughout the day, and showed a peak in feeding activity at dusk. Feeding continued at a reduced level under moonlit conditions, but ceased in total darkness. Stomach evacuation rates for 16-mm fry under continuous feeding and non-feeding conditions were 47 and 210 min, respectively; for 37-mm fry the rates were 73 and 108 min, respectively. The daily rations for these two size groups were 19-86% and 38-56%, respectively. Weight specific daily growth rates were 13-16% for fry reared in ponds. The significance of these results is discussed with respect to the biology and husbandry of small barramundi.