Place-based management can be an effective conservation tool to protect cetaceans from anthropogenic pressures. The spatial use of the world's second largest population of the threatened Indo-Pacific humpback dolphins (Sousa chinensis) is not well-documented, which makes it challenging to designate protected areas for this population. To address this knowledge gap and to test the efficacy of an existing dolphin protected area (Zhanjiang Leizhou Bay Municipal Humpback Dolphin Nature Reserve, ZLBMHDNR), boat-based surveys were conducted to document dolphin occurrence from 2015 to 2018, covering an area of 1221 km(2) in the eastern waters off Zhanjiang, China. In total, 253 dolphin group sightings were obtained during 174 survey days. Spatial analysis showed that humpback dolphins aggregated in three core-use areas with higher sighting density within the survey area. Furthermore, intermediate-use and broad-use areas were identified that could be essential for the movements of humpback dolphins among these core-use areas. The spatial usage of humpback dolphins was compared inside and outside the ZLBMHDNR. Results suggest that the ZLBMHDNR is insufficient to encompass a significant portion of dolphin habitat. The ZLBMHDNR (21 km(2)) is not large enough, and thus it should be expanded for effective place-based conservation management in this region. For developing a protected area network, important dolphin habitats identified in this study should be protected as a single management unit. Additionally, mitigation of anthropogenic pressures is needed to be taken into consideration as conservation initiatives in the study area. This study provides support for a more science-informed protected area network, and highlights the necessity of implementing place-based conservation and management for the world's second largest humpback dolphin population.