Influence of socioeconomic costs on the conservation planning of Indo-Pacific humpback dolphin (Sousa chinensis) in a highly urbanised bay

Effective conservation protection requires the consideration of biological information and socioeconomic costs during the planning stage of reserve development, especially when coastal species occupy habitats that overlap with intensive human activities. Because of the public and liquid nature of the maritime environment, it is difficult to obtain data on its protection costs. Therefore, it is feasible to select a reasonable surrogate cost. This study explored how the spatial priority of marine protected areas changed under three different protection surrogate costs: habitat area, number of ships, and marine zone function; protection targets were set at 5% and 10%. This analysis was based on the distribution data of Indo-Pacific humpback dolphins (Sousa chinensis) in Xiamen Bay, a highly urbanised coastal city in southeast China. Using habitat area as a cost surrogate, the protection boundary length was the largest, but the projected protection area was the smallest, and function loss was also considerable. Using the number of ships as a cost surrogate, both the protection area and function loss were the largest. Using marine zone function as a cost surrogate, the optimal scenario was achieved in which the protection area was of moderate size and the boundary cost and function loss were the smallest. The higher the protection target percentage, the greater the correlation between the results of different protection cost scenarios; the marine zone functional cost scenario had the highest correlation with that of the habitat area cost scenario, while the correlation between the number of ships cost scenario and the habitat area cost scenario was the lowest. The predicted spatial distribution of protected areas differed under the same protection target and cost scenario, owing to seasonal variation in suitable habitats for S. chinensis. Our results suggested that the Jiulong River estuary should be protected and that the currently protected area of Tongan Bay needs to be expanded in the dry season. In the wet season, the southern part of the existing protected area, the marine habitats of the Jiulong River estuary, the northwestern part of Wuyu, and the southern part of Dadeng-Xiaodeng need to be expanded. This study demonstrated a utilitarian exploration of the Marxan model to aid in the protection of rare marine species in coastal areas, providing reference data for the conservation planning of S. chinensis and other marine species.