Winter Abundance and Breeding Habitat Suitability of Spotted Seals (Phoca largha) in the Liaodong Bay of China, 2025

The spotted seal (Phoca largha), a Class I Protected Species in China, relies on Liaodong Bay as its primary breeding habitat in China. In field surveys conducted within the ice-covered zones of Liaodong Bay during January-February 2025, we recorded spotted-seal occurrence records and applied the MaxEnt species-distribution model to identify key predictors of breeding-habitat suitability. The model exhibited fair predictive performance with a mean training AUC of 0.778 and mean test AUC of 0.736. Variable-contribution analysis indicated that sea-ice thickness and distance to shipping lanes were the two dominant predictors, followed by zooplankton biomass and distance to the coastline; these four variables together accounted for 88.2% of the total model contribution. Within the effective survey area, suitable breeding habitat covered approximately 1785 km2, accounting for 80.9% of the whole domain and mainly concentrated in the central ice zone. Suitable habitats corresponded to adequate sea-ice thickness and appropriate distances from shipping lanes and coastlines, whereas unsuitable habitat patches (421 km2, 19.1%) were distributed in marginal zones limited by thin sea ice or high human-disturbance risk. Jackknife tests confirmed that sea-ice thickness was the most influential single environmental variable. Our results demonstrate that physical sea-ice properties constitute the primary driver for spotted-seal breeding-habitat selection. Human disturbance originating from vessel navigation imposes obvious constraints on habitat use, while seawater-related factors may exert indirect effects by mediating prey-resource distribution. This field-based study provides scientific support for targeted conservation and management of spotted-seal winter breeding habitats in Liaodong Bay.