Seasonal dynamics and multi-season persistence of core habitats of the East Asian finless porpoise off the coast of China

Understanding whether important habitats for mobile marine species remain spatially stable throughout the year is essential for effective conservation planning. For small coastal cetaceans inhabiting highly seasonal and human-dominated shelf seas, habitat use may reorganize substantially across seasons, potentially limiting the effectiveness of static spatial protection. Here, we investigated the seasonal dynamics and persistence of core habitats of the endangered East Asian finless porpoise ( Neophocaena asiaeorientalis sunameri ) in the coastal waters off Qingdao, China, using multi-year boat-based surveys conducted between 2018 and 2024. Seasonal kernel density estimation revealed pronounced spatial variation in porpoise distribution. Core habitats expanded during spring, summer, and autumn but contracted and shifted in winter. No areas functioned as year-round core habitat across all four seasons. Instead, habitat use showed strong seasonal turnover, with 61% of core areas occurring in only a single season. However, tri-seasonal core habitats persisted across three seasons and accounted for nearly one-quarter of the cumulative core habitat area, indicating spatially persistent areas of importance. Environmental comparisons showed that multi-seasonal core habitats were characterized by shallow nearshore waters and intermediate to relatively high net primary productivity, whereas winter core habitats occurred farther from shore and showed weaker productivity associations. These results indicate that important habitats are temporally dynamic rather than spatially fixed, highlighting how mobile marine species respond to seasonal environmental variability in human-dominated coastal ecosystems and why temporally explicit habitat assessments are needed to support conservation in dynamic seascapes.