Habitat Suitability Modeling Predicts Two Migratory Groups of the Japanese Sardine, Sardinops melanostictus, in the Sea of Japan

The Japanese sardine, Sardinops melanostictus , is a major fishery resource in the Sea of Japan (SOJ) and East China Sea (ECS); however, recent research on suitable habitats and migration patterns of this fish in these seas is lacking. We aimed to identify the oceanographic conditions (temperature, chlorophyll‐ a concentration, and sea surface height anomaly) suitable for Japanese sardines and predict migration patterns based on temporal variation in areas with suitable oceanographic conditions. We evaluated suitable oceanographic conditions using generalized linear models and presence/absence data from Japanese purse seine fishery operations. Based on the ocean general circulation models, monthly habitat suitability index (HSI) values were calculated and mapped. Areas with high HSI values indicated two possible migration patterns: (1) From January to June (winter–spring), sardines move from the northern SOJ to the Japanese coastal area and then migrate northward again. This pattern matches temporal variations in egg distribution, potentially reflecting the migration of age‐1+ sardines. The HSI maps suggest that age‐1+ sardines inhabit the northeastern edge of the SOJ and its adjacent areas during summer. (2) From July to December (summer–autumn), sardines migrate from the southern part of the SOJ to the coastal area. We consider this a possible age‐0 sardine migration pattern because mainly age‐0 sardines are caught in the southern part of the SOJ in summer–autumn. Thus, we suggest that the two age cohorts have different migration patterns and that sardine stocks in the SOJ and ECS comprise a mix of these two migration groups.