The Responses of Skipjack Tuna in the Northwest Pacific to Climate Variability: Migration Pattern's Seasonality and Heterogeneity

Abstract Redistribution of highly migratory species, such as skipjack tuna (SKJ), poses significant challenges to fisheries management and often leads to international disputes, for which climate signals play an important role. In the Northwest Pacific, a critical SKJ temperate fishing ground, spatiotemporal anomalies such as extended fishing distances and compressed time periods underscore urgent needs to understand the underlying mechanisms. While correlations between SKJ abundance and climate indices are documented, a mechanistic understanding of how large‐scale climate governs the species' distribution has remained elusive. By leveraging a multi‐decadal data set (1972–2020) of pole‐and‐line fishery records and environmental parameters, we have developed an integrated analytical framework, which combines species distribution models with subsequent mechanism‐diagnostic analyses to quantify and unravel the climate‐habitat relationships. Aided by machine learning models, our analyses reveal a coherent SKJ's annual migration pattern. Beyond this, we uncover two‐tiered regulatory regimes controlling habitat variability: primary control from concurrent climate forcings (primarily the Pacific Decadal Oscillation, PDO), and secondary modulation from lagged climatic signals (primarily the Atlantic Multidecadal Oscillation, AMO). Our results designate PDO as the dominant driver, integrating the effects of other climate modes and modulating habitat dynamics primarily through its correlation with sea surface temperature. Our understanding provides a predictive foundation for dynamic ocean management and offers critical insights to guide adaptive fisheries policies in a changing climate.