Non-random feeding enhances the contribution of oceanic zooplankton to the diet of the planktivorous coral reef fish Dascyllus flavicaudus
Combining gut content analysis and sampling of ambient zooplankton, we examine departures from random feeding in a planktivorous coral reef fish and explore the effects of apparent non-random feeding behavior on the relative contribution of oceanic versus reef-associated zooplankton to fish diet. The planktivorous damselfish Dascyllus flavicaudus appears to exhibit strong positive electivity for oceanic copepods including Candacia spp. and copepods from the families Oncaeidae and Corycaeidae and consistent negative electivity for cyclopoid copepods (Oithonidae). In total, prey taxa categorized as oceanic in origin contributed 10–76 % of total zooplankton biomass in fish guts. The summed contribution of oceanic prey taxa to fish diet was significantly higher than expected under a model of random feeding based on the availability of oceanic versus reef-associated prey as sampled by zooplankton net tows. The feeding behavior of D. flavicaudus appears to be visibility-selective rather than or in addition to size-selective, as electivity across prey taxa could not be explained by differences in prey size alone.