Predation and its influence on the condition of a newly settled tropical demersal fish

Abstract

The effects of predation by a common tropical piscivore on levels of variability in size and body composition of a demersal fish at settlement were examined in a series of laboratory experiments. Wild-caught, newly metamorphosed goatfish (Upeneus tragula) were placed in large tanks and subjected to predation by lizardfish (Synodus variegatus). Three trials failed to show an influence of predation on the size distribution of the newly settled prey. In a second experiment, mid-larval-phase goatfish were subjected to one of two feeding regimes; this resulted in two groups of metamorphs that differed markedly in biochemical composition (i.e. total lipid levels). Twenty fish from each treatment were randomly chosen, under the constraint of a similar mean size, and subjected to predation. Susceptibility of newly metamorphosed fish to predation by the lizardfish was independent of their initial biochemical composition. These results suggest that predation by this common tropical reef fish predator may be non-selective with respect to both size and body composition of U. tragula. Consequently, the high variability found in these body attributes at settlement may extend its influence into the juvenile population.