Resumen del producto

Individual diet specialization (IDS) is documented across numerous animal taxa, and has been shown to be driven in many cases by density-dependent resource competition. Highly mobile predators are not subject to density dependence, but it is not known if such organisms demonstrate IDS, in part because they are often hard to study longitudinally. In this study, we combined stomach content (SC), stable isotope (SI), and fatty acid (FA) analyses to assess IDS in three species of mobile pelagic predators: striped marlin (Kajikia audax), blue marlin (Makaira nigricans), and common dolphinfish (Coryphaena hippurus). In order to assess diet specialization, we compared short-term SC with longer-term diet proportions estimated from SI ratios and FA profiles using a Bayesian mixing model. Individuals of all three species demonstrated generalist feeding habits, with minimal differences in long-term diet estimates between predators with different short-term SC. This study suggests that longitudinal integration of diets is indispensable for our understanding of diet specialization in predators whose short-term diets may reflect high resource variability in space and time. These results support theory suggesting that generalist feeding strategies are likely an adaptation for traversing a range of resource-variable habitats, in contrast to specialist strategies that enable more competitive foraging.

Palabras clave: Guadalupe fur seal; fatty acid; Striped marlin; diet

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