Threat identification and spatial risk assessment for a vulnerable Australian humpback dolphin (Sousa sahulensis) population in an urban embayment

Context Intensifying human activities in coastal regions are placing growing pressures on dolphin populations, highlighting the urgent need for comprehensive threat assessments to guide effective conservation and management actions. Aim This study aimed to identify, characterise and rank the level of risk from threats present to an Australian humpback dolphin (Sousa sahulensis) population, a listed Vulnerable species, in the urbanised embayment of Moreton Bay, Queensland, and perform a spatial assessment of cumulative risks to identify areas of more intensive exposure and management priority. Methods Expert elicitation and empirical data were used to identify and rank threats based on the relative risk level. The spatial distribution of threats was then overlaid with relative dolphin density data gathered through vessel-based field observations completed between 2014 and 2022 (1717 h of effort). Key results Twelve key threats to humpback dolphins from anthropogenic activities were identified, with over 50% ranked as high-risk, present throughout the year and exhibiting increasing trends. Pathogens, pollution, habitat degradation, and climate change were the highest-ranked threats in terms of consequence, while vessel traffic and illegal provisioning (hand-feeding) had the highest likelihood scores. Spatial analyses revealed extensive overlap between high-risk areas and hotspots of highest dolphin density. Conclusions This study outlines the level of cumulative risk from anthropogenic threats to humpback dolphins and highlights areas of conservation concern and management priority within a marine protected area. Implications The framework applied offers a robust approach for adaptive conservation strategies and regional species-specific risk assessments, with broader implications for the management of vulnerable coastal dolphin populations.