Data from: Predator-mediated trophic connectivity between reef and oceanic habitats in Palau

Effective fisheries management and marine spatial planning depend on
understanding how mobile predators link reef and oceanic ecosystems
through cross-habitat movements and foraging. Predator resource use shapes
movement and space-use strategies, providing insight into life history and
behavioral variation, the identification of critical habitats, and spatial
patterns of vulnerability to fishing and other human activities. Yet
cross-habitat trophic connectivity remains poorly quantified in diverse
coral reef and oceanic systems. Here, we used stable isotope (δ13C, δ15N)
analysis, complemented by stomach content analysis, to examine
cross-habitat resource use of predatory fishes across reef and near-reef
oceanic ecosystems in Palau, in the Western Pacific, evaluating patterns
across species, trophic guilds, and habitat associations. Cluster
analyses, isotopic niche metrics, and Bayesian stable isotope mixing
models revealed asymmetric but bidirectional connectivity, with resource
utilization typically spanning both habitats but skewed towards reef or
oceanic depending on species groups. Reef predators showed greater
variability in resource use and higher reliance on oceanic inputs than
oceanic predators relied on reef resources, with broad isotopic niches
consistent with mobility, water-column use, and generalist foraging
strategies. In contrast, most oceanic predators largely specialized on
oceanic prey, although stomach contents documenting larval and juvenile
reef fishes indicate occasional incorporation of reef-origin resources.
Our results highlight the disproportionate importance of oceanic
production in supporting reef predator populations, particularly where
physical forcing concentrates prey near reef margins. Although reef
contributions to oceanic predator diets were comparatively small, even
limited inputs may be ecologically meaningful for migratory species during
critical life stages. Together, these findings demonstrate widespread but
trait-structured and individually variable predator-mediated connectivity
that challenges binary “reef” versus “oceanic” classifications.
Incorporating trophic connectivity into fisheries management and marine
spatial planning can better align protection with the energetic pathways
and habitat utilization sustaining predators in reef–ocean systems.