Impacts of Mesoscale Eddies on the Abundance and Distribution of Chub Mackerel (Scomber japonicus) in the Northwest Pacific Ocean

The Chub mackerel (Scomber japonicus) is a key commercial species in the light purse seine fishery in the Northwest Pacific Ocean. Its distribution is highly sensitive to environmental change, yet the regulatory mechanisms of mesoscale eddies on its aggregation remain poorly understood. To further understand the regulatory mechanisms, this study employed a dataset of mesoscale eddies in the Northwest Pacific Ocean (2014–2021) from AVISO (Archiving, Validation, and Interpolation of Satellite Oceanographic Data), combined with fishery data of Chub mackerel and multi-source environmental data (including chlorophyll-a, temperature and dissolved oxygen at different water layers, sea surface salinity, current velocity, and mixed layer depth). By integrating the Gradient Forest (GF) approach, a Generalized Additive Model (GAM), and a Habitat Suitability Index (HSI) model, we quantitatively analyzed the ecological mechanisms of mesoscale eddies on the distribution of Chub mackerel. A total of 800982 mesoscale eddies were identified in the study area, and cyclonic eddies (CEs) accounted for 52.3% of the whole quantity. They were densely distributed in the Kuroshio Extension region (140°–160°E) and exhibited significant seasonal fluctuations. The abundance of Chub mackerel and the proportion of suitable environmental conditions (e.g., chlorophyll-a ‘Chl-a’ and temperature at 150 m depth ‘T150m’) were significantly higher in CEs than in anticyclonic eddies (AEs). The HSI values in CEs were higher than in AEs, driven primarily by the significant advantages of Chl-a suitability (SI_Chl-a) and T150m suitability (SI_T150m) in CEs, while the effects of dissolved oxygen (DO, SI_DO/SI_DO150m) showed minor differences between the two eddy types. This study reveals that CEs enhance primary productivity, alleviate hypoxia stress, and maintain favorable thermal conditions through upwelling, providing critical feeding and habitat conditions for Chub mackerel and ultimately driving its aggregation.