The Evidence for Nekton Distribution Modulated by Plankton Abundance in the High Seas Area of Northwest Pacific During Summer Season

ABSTRACT Deterministic biotic interactions and abiotic conditions define species distributions and abundance, with plankton underpinning food webs to spatially structure predator distributions through bottom‐up processes. However, characterizing the mechanism underlying species abundance formation in an oceanic system remains challenging. We applied piecewise structural equation models to examine plankton abundance and environmental conditions in nekton assembly, combined with joint species distribution models to investigate the distribution associations between nekton and plankton in the high‐seas area of northwest Pacific. Results revealed that nekton distribution (fish and squid) showed significant associations with plankton abundance, where zooplankton correlations markedly surpassed phytoplankton associations. The fluctuations of plankton abundance directly influence nekton abundance, whereas the effects of environmental conditions were mediated indirectly through effects on plankton. These findings affirm the primacy of plankton abundance in driving nekton distribution and advance understanding of how bottom‐up trophic pathways modulate nekton distribution dynamics in pelagic ecosystems.