Feeding habits affect the energy accumulation capability of pelagic nektons in the high seas of northwest Pacific

Energy reserves are critical for survival, reproduction, and resilience to environmental variations for marine organisms. However, the energy accumulation capacity in terms of feeding habit impact remains poorly understood, especially for pelagic nektons in the high seas. Here, we measured muscle energy density, stable isotopes and fatty acids for nine pelagic species in the northwestern Pacific Ocean. We quantified isotopic hypervolume (based on stable isotopes, referred to trophic breadth) and nutritional hypervolume (based on fatty acids, referred to dietary richness) following Hutchinson’s n -dimensional hypervolume framework, and examined their relationships with energy density using Bayesian linear hierarchical models. Results revealed taxon-specific variations in energy accumulation capacity among the nektons. A significant positive allometric relationship was observed between energy density and dietary richness, whereas no significant association was detected with trophic breadth. Notably, energy density was not correlated with any individual fatty acid, suggesting that energy accumulation arises from synergistic interactions among diverse dietary components rather than specific prey item. Furthermore, interspecific variation in scaling exponents reflects niche-specific adaptations linked to life-history strategies. Our findings highlight that dietary richness shapes energy accumulation capability, emphasizing the importance of dietary complexity in mediating energy dynamics and species fitness in marine ecosystems.