Climate-driven dispersal and potential migration pathways of Decapterus macarellus in the South China Sea

Understanding the migration patterns of pelagic economic fish species is fundamental to fisheries research, development, and management. Mackerel scad ( Decapterus macarellus ) is a migratory species with a circumglobal distribution and represents an important commercial resource in the South China Sea. This species is characterised by a wide distribution range, a complex population structure, and high sensitivity to climatic variability. Elucidating individual dispersal, migration, and distribution patterns of D. macarellus under climatic fluctuations is therefore critical for effective resource development and management. In this study, D. macarellus samples collected in different years were analysed, and otolith trace elements were quantified using laser ablation–inductively coupled plasma mass spectrometry (LA-ICP-MS). Individual life-history processes were subsequently inferred using multivariate regression tree (MRT) analysis. On this basis, developmental dispersal patterns of D. macarellus individuals were predicted for different years. The results indicated that Sr/Ca and Na/Ca ratios differed significantly among years ( P < 0.05), whereas Mg/Ca, Ba/Ca, Fe/Ca, and K/Ca ratios showed no significant interannual variation ( P > 0.05). MRT analysis partitioned the otolith transects into five clusters, corresponding to five life-history stages. Regression models were established between Sr/Ca and Na/Ca ratios and sea surface temperature (SST), and areas with high probability values were interpreted as potential suitable habitats. Based on these results, potential individual dispersal pathways were predicted. El Niño–Southern Oscillation (ENSO) events may contribute to interannual differences in the spatial locations and extents of habitats occupied by D. macarellus at different developmental stages. Although interannual differences in inferred dispersal patterns were evident, the overall potential migration direction remained broadly consistent across years.