Zooplankton preference of two species of freshwater ornamental fish larvae

The dietary preferences of larval mollies, Poecilia sphenops Steindachner, 1863, and angel fish, Pterophyllum scalare (Lichtenstein, 1823), were studi ed using the rotifer Brachionus calyciflorus and the cladoceran Moina macro copa as prey. The experiments were conducted at 5- to 7-day intervals from day 5 after hatching until day 55 for mollies, and from day 15 after hatchi ng until day 40 for angel fish. Rotifers and cladocerans were offered alone or in combinations. Moina individuals were sized as neonates or adults bef ore being used as prey. Regardless of their age, the larval mollies preferr ed rotifers, while even during their early stages the angel fish consumed h igher numbers of cladocerans. Prey preference values were calculated using Murdoch's electivity index.