The conservation outcome of Indo-Pacific humpback Dolphin in China: A habitat suitability-based assessment

Effective planning of protected areas (PAs) for Indo-Pacific humpback dolphins (IPHDs) requires habitat identification and assessment of existing conservation outcomes. However, a systematic framework to evaluate the conservation outcomes of protected areas for this species is still absent. Therefore, we applied the MaxEnt model to estimate habitat suitability for eight IPHD populations in China. We further employed the Geographic Detector model to quantify the relationships between human activities and habitat suitability. To evaluate conservation outcomes, we developed a spatial framework integrating the Reasonable Site Selection Index (RSI) and the Sufficient Cover Index (SCI) to derive the Relative Protection Level (RPL). Results indicate: (1) Chlorophyll-a concentration, salinity, and sea surface temperature are the top-ranking influential factors shaping IPHD habitat preferences. Among anthropogenic variables, vessel density and offshore fixed infrastructure density showed strong associations with suitability, and their interactions with each other further amplified these effects. (2) All populations have less than 40 % coverage of high-suitability areas, and both the Longtou Bay and Raoping Chinese White Dolphin Nature Reserves encompass only low-suitability habitats. (3) The 14 PAs fall into three protection types: “High RSI - High SCI” ( n = 1), “Low RSI - Low SCI” ( n = 3), and “High RSI - Low SCI” ( n = 10), indicating a critical need of expanding PAs to larger areas. (4) RPL ranges from 30 % to 55 % except for the alarming level of Shantou waters (≤4.76 %). The work can inform more strategic PA design and provide evidence-based recommendations for enhancing IPHD conservation. • Evaluated habitat suitability across China's eight dolphin populations. • Influencing factors of suitable habitat distribution vary significantly. • 13 of the 14 existing PAs have a Sufficient Cover Index below 50 %. • The relative protection level shows more MPA coverage in need.