Conservation Status of the Indo-Pacific Humpback Dolphin (Sousa chinensis) in the Northern Beibu Gulf, China

Long‐term habitat loss in a lightly‐disturbed population of the Indo‐Pacific humpback dolphin, Sousa chinensis

“…Meanwhile, distribution gradients of the dolphins, indicated by SPUF, did not change significantly over past decades. These results might lead to a conclusion that the demographic status of the humpback dolphin in northern Beibu Gulf is stable, but this might be too optimistic, considering the increasing habitat loss (in this study) and anthropogenic activities in the northern Beibu Gulf in the past decades (Chen et al, ; Wu et al, ). Instead, these results perhaps indicate the shortcomings of using questionnaire results to assess demographic status of humpback dolphin in northern Beibu Gulf.…”

“…The moderate correlation between SPUFs and Hcs, on the other hand, suggests the effectiveness of LEK in identifying distribution patterns and likely habitats over a mesoscopic range. Along the coast of the northern Beibu Gulf, occurrence of the humpback dolphin has been formerly reported from the waters east of sector L (Hepu Dugong Reserve) and the centre of sector G (the Sanniang Bay–Dafenjiang River Estuary waters) (Chen et al, , ; Wu et al, ). A recent review of humpback dolphin status in this region claims that there are two somewhat distinct social communities inhabiting these two areas, separated by a possible gap in distribution (Chen et al, ).…”

“…Along the coast of the northern Beibu Gulf, occurrence of the humpback dolphin has been formerly reported from the waters east of sector L (Hepu Dugong Reserve) and the centre of sector G (the Sanniang Bay–Dafenjiang River Estuary waters) (Chen et al, , ; Wu et al, ). A recent review of humpback dolphin status in this region claims that there are two somewhat distinct social communities inhabiting these two areas, separated by a possible gap in distribution (Chen et al, ). Both the SPUF gradients and likely core habitat identification, however, indicate that distribution of the humpback dolphin may be continuous along the entire northern Beibu Gulf.…”

“…To identify the likely habitat of the humpback dolphin in the northern Beibu Gulf, three isobath contours (−1 m, −5 m and −15 m) were applied to the global digital elevation model (DEM) overlaying the study area from ETOPO 1 Global Relief Model, National Geophysical Data Center (NGDC), National Oceanic and Atmospheric Administration (NOAA) (Amante & Eakins, ; https://www.ngdc.noaa.gov/mgg/global/global.html). Waters between −1 m and −5 m isobaths were assigned as likely core habitats (Hc), and between −1 m and −15 m were assigned as likely habitat‐maximum (Hm), based on current knowledge of the distribution patterns and habitat preferences of the humpback dolphin (Chen et al, ; Jefferson & Karczmarski, ; Jutapruet et al, ; Wang, Wu, Turvey, Rosso, & Zhu, ; Wu et al, ). Then, areas for which habitat loss occurred inside Hc s were extracted and calculated as the primary habitat loss at sector s , Hl s .…”

“…In the northern Beibu Gulf, occurrence of the humpback dolphins has been systematically investigated at two neighbouring locations, the Hepu Dugong Reserve (HDR) and Dafengjiang River Estuary (DRE) habitats (Chen, Zheng, Yang, Xu, & Zhou, ; Chen et al, ; Wu et al, ) and interpreted as possible evidence of two social communities (Chen et al, ). Outside these two habitats, opportunistic sightings of the humpback dolphin were reported at Red River Estuary in Vietnamese waters based on two cetacean surveys (Smith et al, ).…”