Quantifying patterns and drivers of larval dispersal in Japanese anchovy ( Engraulis japonicus ) in the China Seas

Abstract. Larval dispersal is a fundamental process linking marine populations and shaping individual fitness and population connectivity, making its quantification essential for understanding recruitment dynamics in fisheries. However, larval dispersal of the commercially and ecologically important Japanese anchovy (Engraulis japonicus), one of the most abundant pelagic fishes in the China Seas, remains poorly understood. Here, we applied 1D and 2D dispersal kernels to quantify larval dispersal outputs from previously published Lagrangian particle-tracking simulations, in which particles were released from seven spawning grounds across the China Seas during April–August (1987–2004) and tracked for 30–60 d. We evaluated the relative influences of spawning ground, spawning month and year, and larval travel duration, on dispersal patterns and connectivity. Larval settlement was concentrated in the Bohai Sea, the northern Yellow Sea and along the southern coast of the Shandong Peninsula, with peak densities near 39° N, identifying these regions as major nursery areas. A Weibull 1D dispersal kernel best described larval dispersal-distance distribution, with modal dispersal distances from 42.67 to 153.23 km among spawning grounds. Of the factors examined, spawning ground was the dominant driver of dispersal and connectivity, explaining 31 % of the variance. Larvae from Changjiang Estuary spawning ground dispersed more broadly to the Yellow Sea, Sea of Japan and the northwestern Pacific, whereas larvae from other grounds were largely retained within the China Seas, suggesting the Changjiang Estuary may provide a potential pathway for connectivity among regional populations. Dispersal patterns exhibited strong seasonal shifts, with enhanced eastward and northward export in spring–early summer and increased retention in late summer. Increasing larval travel duration promoted directional long-range transport while reducing occupied area, local retention and self-recruitment, indicating that longer dispersal does not imply broader spatial occupation. Pelagic larval duration captured mean dispersal trends but was a poor predictor of individual dispersal outcomes. Overall, these findings provide a quantitative framework for understanding larval dispersal dynamics and may help inform fisheries management of Japanese anchovy.