Ecologically critical thresholds of marine heatwaves control spatiotemporal patterns of Japanese flying squid

Marine heatwaves (MHWs), discrete and prolonged periods of anomalously high ocean temperatures, have been occurring with increasing frequency and intensity in recent years, threatening global fisheries. This study employs nighttime imageries and random forest models to analyze the impacts of MHWs on Japanese flying squid (Todarodes pacificus) nighttime fisheries in the Sea of Japan (East Sea) (2014–2023). For the first time, critical MHWs thresholds were identified: monthly duration exceeding 16 days and cumulative intensity surpassing 50 °C·days trigger significant contraction of core fishing grounds, particularly in summer/autumn, exhibiting strong negative correlations to catch and vessel numbers (|r| > 0.7, p < 0.05). Sea surface temperature (SST) is the primary driver of spatiotemporal patterns of squid fishing grounds (45% model contribution), with optimal fishing conditions at 17.08 °C. Regional MHWs sensitivity varies across exclusive economic zones (EEZs), with the South Korean EEZ responding strongest (R² = 0.77) to MHWs characteristics. This research establishes novel MHWs impact thresholds for migratory squid fisheries and provides a data-driven framework for adaptive management in semi-enclosed seas, highlighting the urgency of addressing extreme climate events in fisheries governance.