Distribution and conservation of the Indo–Pacific humpback dolphin in China

Abstract

The Indo-Pacific humpback dolphin (Sousa chinensis Osbeck, 1765) is a threatened species inhabiting the waters of China. Despite being of conservation concern, the distribution and abundance of this species has not been comprehensively evaluated. From 1994 to 2008 we performed over 14 000 km of line-transect surveys and administered over 700 questionnaires to collect basic information on the geographic range and likely abundance of IndoPacific humpback dolphins along the southern and eastern coasts of China. Through our study we were able to establish a reporting network of stranding and incidental catches for this species. Our quantitative data suggests that only 76 animals remain around Xiamen, 39 in the Hepu Nature Reserve and 114 in the estuary of the Dafengjiang River. Qualitative data from local fishing people and government officials suggests that dolphins may exist yearround in waters off Ningde and Shantou. We found that wild populations of Sousa chinensis in this important region are clearly being affected by human disturbance and habitat deterioration, including underwater blasting, vessel collision, fishing, aquaculture and water pollution. Although some protected areas have been established and this species is protected under Chinese law, there remains virtually no protection for this animal.

First record of the Indo-Pacific humpback dolphins (Sousa chinensis) southwest of Hainan Island, China

“…Thus, these sightings consist of the first record of S. chinensis in the coastal waters southwest of Hainan Island, as until now the waters were considered void of S. chinensis ( Fig. 1a; Jefferson and Hung, 2004;Zhang and Tang, 2008;Chen et al 2009) despite previous records along the coastal waters of Vietnam within the Beibu Gulf (Smith et al 2003). This new record expands the currently known Chinese distribution range of this lion-sized mammalian predator by more than 300 km south.…”

“…1a; Jefferson, 2000;Jefferson and Hung, 2004;Chen et al 2009). It was assumed that S. chinensis was sporadically distributed along the coast, from the Beibu Gulf near the Vietnamese border to the mouth of the Yangtze River ( Fig.…”

“…On the basis of the best available information about S. chinensis and its habitat along the coast of mainland China (Jefferson and Rosenbaum 2014), waters around Hainan Island which are isolated from mainland China by the Qiongzhou Strait, where water is deep and appears to be a barrier for movement of this species (Chen et al 2009), did not include distribution records of S. chinensis (Jefferson andHung 2004, Chen et al 2009). However, targeted marine mammal surveys are too few and only carried out in certain waters along the coast of mainland China despite a need for a comprehensive understanding of S. Chinensis' distribution in Chinese waters to underpin a robust and sound conservation plan.…”

Whistle characteristics of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in Sanniang Bay, China

“…These are the populations in Leizhou Bay (20 51 0 S; 110 30 0 E) (N ¼ 268 with a 95% confidence interval of 189-413) (Xu et al, 2012), in the Pearl River Estuary of Guangdong (22 16 0 S; 113 43 0 E) (N ¼ 2555 and N ¼ 2517 during wet and dry seasons, respectively) , in Xiamen harbor of Fujian (24 29 0 S; 118 13 0 E) (N ¼ 76; 95% CI ¼ 43-109) (Chen et al, 2009), at the West coast of Taiwan (23 54 0 S; 120 12 0 E) (N ¼ 75; 95% CI ¼ 69-81) (Yu et al, 2010), and in the Beibu Gulf of Guangxi (21 32 0 S; 108 42 0 E) (N ¼ 251; 95% CI ¼ 136-794) (Pan et al, 2006;Chen et al, 2009), respectively. At least two small subpopulations have been discovered at the National Hepu Dugong Nature Reserve in Beibu Gulf: In the Dafeng River Estuary and in Sanniang Bay.…”

“…1) is relatively undeveloped with small human population and has only been impacted to a small extent from anthropogenic activities, such as smallscale fishery, rare merchant ship traffic, and relatively low levels of environmental contaminants (Pan et al, 2006;Chen et al, 2009). Thus it represents a preferable habitat for humpback dolphins.…”