Prediction of the migration route of Ommastrephes bartramii in Northwest Pacific Ocean based on Habitat Suitability Model and its relationship with ENSO

The environmentally sensitive neon flying squid (Ommastrephes bartramii) undertakes large-scale, long-range and seasonal migrations between spawning and feeding grounds in the Northwest Pacific to seek the optimal habitat conditions for growth and development. To elucidate the general feeding migration routes of the neon flying squid in the Northwest Pacific Ocean, this study developed a Habitat Suitability Index (HSI) model utilizing environmental data, including Sea Surface Temperature (SST), Sea Surface Height (SSH), and Photosynthetically Active Radiation (PAR), along with fisheries catch statistics. The model was applied to analyze the squid's migration distribution during the feeding season (from July to November) from 1998 to 2020 and its relationship with the El Niño Southern Oscillation (ENSO). The results indicated that in early July, the squid were widely distributed within 152°–165°E and 38°–42°N. The feeding migration comprised three distinct phases: 1) Initially, the squid aggregated rapidly northwestward, reaching 155.48°E, 41.75°N by early August. 2) Subsequently, they turned northeastward, progressed slowly along the Subarctic Front, and arrived at the northernmost point (156.56°E, 43.46°N) in late September. 3) Finally, they commenced a direct return migration southwestward, arriving at 151.52°E, 41.26°N by late November. Over the past 23 years, the significant interannual variability was observed in the migration routes, with longitudinal and latitudinal shifts of approximately 1.7° and 0.5°, respectively. The research reveals that ENSO events influence the spatiotemporal distribution of juvenile squid, leading to a more eastward-biased northward feeding migration. Compared to normal years, during La Niña events, the expanded suitable habitat promoted faster growth and a quicker northward migration, resulting in a more northerly terminus (43.76°N). Conversely, during El Niño years, the migration tended to stall south of 43°N, with slower north-south progression. Furthermore, constrained by regional environmental conditions, the squid exhibited a higher aggregation tendency from mid-August to early October, which enhanced the commercial fishing efficiency. It is concluded that the neon flying squid in the Northwest Pacific follows a defined feeding migration route, which exists distinct modifications in response to ENSO events. These findings particularly provide a scientific support for understanding and managing the fisheries resource of neon flying squid in the Northwest Pacific Ocean.