Fine-scaled habitat preference of the Yangtze finless porpoise in the Yangtze River

Abstract The Yangtze finless porpoise (Neophocaena asiaeorientalis) is critically endangered and suffered from extensive habitat loss and fragmentation. Knowledge on habitat preference of the Yangtze finless porpoise could assist finless porpoise and associated ecosystem-based conservation by knowing porpoises’ suitable environments and prioritizing conservation sectors. In the present study, porpoise occurrences and numbers were collected in a 30-kilometer mainstream of the Yangtze River. Environmental variables were uniformly sampled in the dry and wet seasons. The maximum entropy model (MaxEnt) was then applied to porpoise data and environmental variables to analyze the effects of environmental variables on porpoises habitat preference. Within the study area, suitable habitats of the finless porpoises accounted for 19.0% and 15.4% of the study area during the dry and wet seasons. The suitable habitat of the finless porpoises shifted from the mainstream in the dry season to the sandbar head and tributary area in the wet season. In the dry season, variables influencing finless porpoise distribution were phytoplankton biomass, flow rate and zooplankton biomass, which contributed 97.05% variation in the MaxEnt modeling. In the wet season, water depth and surface water temperature accounted for 88.45% of the porpoise distribution. Above results highlighted higher conservation priority for the finless porpoise in the dry season when fish resources are relatively scarce while porpoises mainly distribute in the mainstream. Measures including monitoring and evaluating prey resources, management of shipping routes and shipping speed should be considered.