Long-term increase in mortality of Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary following anthropic activities: Evidence from the stranded dolphin mortality analysis from 2003 to 2017

Sun, Xian; Guo, Lang; Luo, Dingyu; Yu, Ri-Qing; Liang, Yuqin; Liu, Zhiwei; Wu, Yuping

doi:10.1016/j.envpol.2022.119526

Cited by 20 publications

(21 citation statements)

References 68 publications

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“…In line with a recent study that revealed that vessel transportation, fishing activities, and pollutant bioaccumulation were the three major causes of humpback dolphin mortality in LDB (Sun et al, 2022), our results…”

Section: Conservation Perspectivessupporting

confidence: 93%

“…Threats to IPHDs include diverse types of intense fishing activities (e.g., gillnetting, trawling, and long‐lining) and aquaculture (e.g., oyster and fish farming) along the Chinese coast (Chen et al, 2016; Huang et al, 2022; Jefferson, 2000; Lin et al, 2021; Slooten et al, 2013). Vessel traffic (e.g., Chen et al, 2016; Sims et al, 2012) and contamination with pollutants, including PFAs, PCBs, DDTs, or heavy metals (Gui et al, 2014, 2017; Sun et al, 2022) are also important concerns for these animals. In recent decades, several populations of IPHDs have been shown to be in rapid decline (e.g., Lingding Bay, Huang et al, 2012; Guo et al, 2020; Xiamen Bay, Zeng et al, 2020; Sanniang Bay, Lin et al, 2022), while other populations inhabiting less developed coastal regions (e.g., Jiangmen area, Leizhou Bay) are thought to be less impacted by anthropogenic activities and therefore less threatened (Chen et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Injuries and skin condition ofIndo‐Pacifichumpback dolphins (Sousa chinensis) in the northern South China Sea

Serres

Lin

Liu

et al. 2023

Marine Mammal Science

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Indo‐Pacific humpback dolphins (Sousa chinensis) inhabiting the Chinese coastline of the northern South China Sea are subject to intense human activity. To investigate potential impacts to dolphins, photographs taken from 2010 to 2021 in five different locations were analyzed. Among individual dolphins (N = 1,159), 10.6% presented human‐induced injuries. Adults were more frequently injured than young dolphins, and individuals from around Jiangmen, Hainan, and Sanniang Bay presented the highest injury prevalence. More research should be conducted in areas that have been subject to less research, such as Jiangmen and Hainan, and the dolphin watching activities occurring in Sanniang Bay should be monitored and regulated. Forty‐seven percent of dolphins presented skin conditions, with orange patches being the most frequent (41.5%). Orange patches and hyper‐pigmented pink spots were significantly less prevalent in summer and fall than in winter and spring. Orange patches were less frequent in females than in males, as well as with calves relative to older age classes. Seasonal patterns may be linked to water temperatures, while demographic patterns may be associated with immune defenses. These findings allow for a better understanding of the potential impact of human activities on Indo‐Pacific humpback dolphins and should inform further conservation measures.

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Section: Conservation Perspectivessupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Injuries and skin condition ofIndo‐Pacifichumpback dolphins (Sousa chinensis) in the northern South China Sea

Serres

Lin

Liu

et al. 2023

Marine Mammal Science

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“…Historically, the Pearl River was a highly diverse aquatic ecosystem with abundant fishery resources, which contained 285 fish species in the river and 152 fish species in its estuary, as documented in the 1980s . After 40 years of development, the Pearl River experienced large perturbations and encountered almost all potential types of stress from anthropogenic activities, including overfishing, water pollution, water conservancy construction, and vessel navigation. − To date, the diversity of the fish community in the Pearl River decreased dramatically in the 2010s if comparison with that of in the 1980s, , wherein the larva and juvenile density of four major Chinese domestic carps (Mylopharyngodon piceus, Ctenopharyngodon idella (C. Idella), Hypophthalmichthys molitrix, and Hypophthalmichthys nobilis (H.…”

Section: Introductionmentioning

confidence: 99%

Supporting Evidence for the “Ten-Year Fishing Ban”: Different Modes of Fishing and Pollution Induce a Fish Diversity Decline between the Pearl River and Its Estuary

et al. 2023

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To settle the emerging debate on whether a "ten-year fishing ban" is too long or an annual fishing moratorium is enough for fish resource restoration in the Yangtze River, a long-term comparison between the 1980s and the 2020s in the Pearl River was performed. Significant declines in fish biodiversity were determined among both the Pearl River and its estuary over the past decades. The trophic level increased from 4 to 5 in the estuary, whereas it remained at 4 in the Pearl River. Interestingly, an opposite trend in interspecies networks of fish was observed between the Pearl River and its estuary. A reduced density and increased links were detected in the Pearl River as its interspecies networks became complex, which was in contrast to that in the estuary. Furthermore, fishing and pollution were both confirmed to participate in the fish biodiversity decline in the Pearl River, whereas pollution was the dominant factor inducing the fish biodiversity decline in the estuary. Our case indicated that an annual fishing moratorium is not enough for fish resource restoration and supports the strategy of "ten-year fishing ban". Moreover, pollution should also be brought under control so that we can facilitate fish resource restoration.

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“…Variuos studies have indicated that this population could reach the status of Endangered (EN) or even Critically Endangered (CR) (Huang et al, 2012;Chan, 2019). Several previous studies have investigated the life history, population size, survival rates, age structure, feeding habits, sociobehavioral dynamics, and pollutant accumulation in Indo-Pacific humpback dolphins in the PRE (Chen et al, 2010;Jefferson et al, 2012;Lin et al, 2021b;Sun et al, 2022). Since cetaceans have a fully aquatic lifestyle and are difficult to observe, surveys of their habitats are often subject to various limitations, such as weather conditions, and human and material resources.…”

Section: Introductionmentioning

confidence: 99%

Habitat decline of the largest known Indo-Pacific humpback dolphin (Sousa chinensis) population in poorly protected areas associated with the hypoxic zone

Guo

Luo²,

Yu³

et al. 2022

Front. Mar. Sci.

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Reserve planning based on the investigation of the core habitat distribution of wild cetaceans is a powerful conservation strategy for protecting target species. However, studies on core habitats and their variations at the large-scale distribution of cetaceans are limited. In this study, we conducted a seven years (2015-2021) boat-based field observation surveys with highly applicable and generalized methods to analyze the habitat changes and how these changes influenced the largest known Indo-Pacific humpback dolphin (Sousa chinensis) population in the Pearl River Estuary (PRE), China. Our findings revealed that there is 3204 km2 of dolphin habitat in the PRE, and dolphin distribution preferences are related to nutrients and biological resources. The decreasing trend of dolphin sighting rates in most areas (73.2%) indicated that the dolphin habitat had declined, and the annual habitat decline rate (2.83%; 95% confidence interval: 0.58%-5.08%) was consistent with the population decline rate. The annual habitat decline rate in the hypoxic zone revealed that low dolphin sighting rates from March to October in the hypoxic zone was 0.43% faster than that in the non-hypoxic zone, indicating long-term sustained effects of summer hypoxia on the dolphin population. Existing reserves have partially prevented habitat decline. However, more than 82.3% of the habitat has not been effectively protected and encounters the threats of pollution and hypoxic stress. This study offers new scientific evidence for developing effective monitoring strategies for humpback dolphin populations in the PRE, and also help establish spatial planning and management measures for reserve habitats.

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Long-term increase in mortality of Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary following anthropic activities: Evidence from the stranded dolphin mortality analysis from 2003 to 2017

Cited by 20 publications

References 68 publications

Injuries and skin condition ofIndo‐Pacifichumpback dolphins (Sousa chinensis) in the northern South China Sea

Injuries and skin condition ofIndo‐Pacifichumpback dolphins (Sousa chinensis) in the northern South China Sea

Supporting Evidence for the “Ten-Year Fishing Ban”: Different Modes of Fishing and Pollution Induce a Fish Diversity Decline between the Pearl River and Its Estuary

Habitat decline of the largest known Indo-Pacific humpback dolphin (Sousa chinensis) population in poorly protected areas associated with the hypoxic zone

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