Sousa spp., humpback dolphin, Sousa plumbea, sousa chinensis, sousa teuszii, Sousa sahulensis, endangered, extinction risk, review, conservation status, anthropogenic, Threat assessment
The humpback dolphin genus (Sousa spp.) has recently been revised to contain four species: S. teuszii, S. plumbea, S. chinensis, and S. sahulensis (1). All four species are listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) (2). S. chinensis and S. sahulensis are classified as Vulnerable on the International Union for Conservation (IUCN) Red List, S. plumbea is Endangered, and S. teuszii is Critically Endangered (3, 4). The humpback dolphins and their habitats—shallow, coastal waters of the eastern Atlantic, Indian, and western Pacific Oceans—are threatened by fishing, vessel traffic, habitat degradation and destruction, environmental contaminants, and prey depletion, putting the humpback dolphins at risk of extinction (4–7). Interventions at the national and international levels are urgently needed. Environmental pollution and other anthropogenic activities affect humpback dolphins throughout their territories. High levels of organochlorines have been found in the blubber of humpback dolphins in China and South Africa (8, 9). Large-scale dredging, drilling, land reclamation, construction blasting, boat traffic, resource extraction, and other coastal development projects are concentrated within humpback dolphin habitat and threaten their survival in Africa, India, southeastern China, and northern Australia (4, 7, 9, 10). Saving the humpback dolphins, a charismatic megafauna and valuable genetic resource, is important to nearshore marine biodiversity (4). Yet dolphin populations in poor, developing countries receive little study and management attention (4). Even in the territories of relatively wealthy and well-developed nations, such as Australia, China, and South Africa, the state and local governments have failed to provide adequate protection for the humpback dolphins to prevent population declines (4, 7, 10). To ensure the safety of humpback dolphins, scientists and conservationists must thoroughly evaluate and recognize the conservation status and risk factors of the various species, subspecies, and populations. Governments of countries that are home to humpback dolphins should also take urgent action to support extensive and substantive national and international collaboration to put in place a set of conservation actions, such as helping coastal fishermen to broaden their income sources and decrease their reliance on nearshore fishing, thereby reducing the threat to humpback dolphins and their habitats.