Food partitioning and spatial subsidy in shelter-limited fishes inhabiting patchy reefs of Patagonia.

The diets of the most conspicuous reef-fish species from northern Patagonia, the carnivorous species Pseudopercis semifasciata, Acanthistius patachonicus, Pinguipes brasilianus and Sebastes oculatus were studied. Pinguipes brasilianus had the narrowest diet and most specialized feeding strategy, preying mostly on reef-dwelling organisms such as sea urchins, limpets, bivalves, crabs and polychaetes. The diet of A. patachonicus was characterized by the presence of reef and soft-bottom benthic organisms, mainly polychaetes, crabs and fishes. Pseudopercis semifasciata showed the broadest spectrum of prey items, preying upon reef, soft-bottom and transient organism (mainly fishes, cephalopods and crabs). All S. oculatus guts were empty, but stable-isotope analyses suggested that this species consumed small fishes and crabs. In general, P. brasilianus depended on local prey populations and ate different reef-dwelling prey than the other species. Pseudopercis semifasciata, A. patachonicus and probably S. oculatus, however, had overlapping trophic niches and consumed resources from adjacent environments. The latter probably reduces the importance of food as a limiting resource for these reef-fish populations, facilitating their coexistence in spite of their high trophic overlap.