Chinese white dolphins in Hong Kong waters have dropped by 80% in 18 years and there is no sign of recovery

The "Marine Mammal Surveillance Report 2021-22" released by the Agriculture, Fisheries and Conservation Department today (12th) mentioned that researchers have conducted 165 spline on-board surveys in the past 12 months, and a total of 158 groups of Chinese white dolphins (total 554) and 73 groups of finless porpoise (total 158) were observed.

In addition, the report also mentioned that the number of Chinese white dolphins in Hong Kong waters has dropped by nearly 80% in the past 18 years, and the number of local dolphins has not shown any signs of recovery.

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554 Chinese white dolphins and 158 finless porpoises observed

In the "2021-22 Marine Mammal Surveillance Report", it is mentioned that during the 12-month period, researchers conducted a total of 165 spline on-board surveys, sailed 6,566.1 kilometers in ten survey areas in Hong Kong, and conducted surveys on boats and helicopters. A total of 158 groups of Chinese white dolphins (554 in total) and 73 groups of finless porpoises (158 in total) were observed.

In 2021-22, Chinese white dolphins are often seen in the waters of West Lantau and the distributary peninsula, but they are less frequent in the northern part of Southwest Lantau, and there are sporadic records in the waters at the western end of North Lantau.

On the other hand, the sightings of finless porpoises are mainly concentrated in the waters east and south of the Soko Islands.

Concentrated on the waters near the coast of West Lantau and the western tip of South Lantau

According to the report, by mid-2021, the habitats of Chinese white dolphins are mainly concentrated in the waters near the coast of West Lantau and the western tip of South Lantau.

In the past decade, the occurrence rate of dolphins in the waters of North Lantau Island has dropped significantly, and in recent years, it has only concentrated in the western end of the waters, and because of the successive implementation of large-scale reclamation and near-shore development projects, the occurrence rate has not shown any signs of recovery.

In the past ten years, the occurrence rate of dolphins in Da Mo Dao Marine Park, Sha Chau and Lung Kwu Chau Marine Park has decreased significantly, and the trend is also consistent with the passive underwater sound monitoring study conducted during the same period; Steady and consistently high levels of dolphin use were recorded in 2018.

In 2021, the overall number of Chinese white dolphins in the four survey areas of southwest, west, northwest and northeast of Lantau is estimated to be 40. In the past two decades, the number of dolphins in the survey areas of northeast, northwest and west of Lantau has been recorded separately. There is a clear downward trend, and the overall number of dolphins in the four survey areas has also recorded a clear downward trend in the past ten years.

The number of finless porpoises reclaimed in Shekguzhou has decreased significantly recently

The habitats where the finless porpoise recorded the highest occurrence in 2021 are located in the waters east and west of the Soko Islands.

The finless porpoise has changed its habitat use in the waters off Shek Kwu Chau and Sok Kwu Islands and in the waters south of Cheung Chau at different times.

During 2015-17, the occurrence rate of finless porpoise in the waters between Shek Kwu Chau and Sok Kwu Islands was recorded at a high level, but then it decreased significantly during 2018-21, especially in the adjacent "Integrated Waste Management" The Shek Kwu Chau waters of the reclamation project are more obvious.

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The report also showed that the quality of the dolphin habitats in the two marine parks on North Lantau deteriorated rapidly and significantly after the implementation of the near-shore development projects; while the habitat quality in the marine parks on Southwest Lantau did not improve before and after the construction of the bridge. too big a difference.

On the contrary, the importance of marine mammal habitat in the South Lantau Marine Park has been increasing in recent years, proving the need to establish this marine park as soon as possible to protect the only remaining marine mammal habitat in the waters of western Hong Kong.

During the 2021-22 monitoring year, researchers identified 106 individual dolphins with a total of 370 sightings, three-quarters of which occurred in the waters west of Lantau.

In 2021, a total of seven new individual dolphins have been added to the photo identification list, and a total of 11 individual dolphins that have frequented Hong Kong waters in the past have disappeared in 2021.

The numbers of individual dolphins moving between the survey areas to the northwest and west of Lantau Island and between the survey areas to the west and southwest of Lantau Island have both continued to decline in recent years.

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The WWF said their sonar and visual survey data were also similar to the monitoring results, showing the ecological importance of west and south Lantau and the urgency of conserving the waters there.

It is recommended that the government set up a dolphin conservation and management area as soon as possible to expand the scope of the Southwest Lantau Marine Park to protect the waters of Tai O and Lo Kei Wan, as well as the natural and long coastline of southwest Lantau; it is also recommended that the government set up a buffer zone to connect the coast of Sha Chau and Lung Kwu Chau The park, the South-West Lantau Marine Park, the South Lantau Marine Park and the waters around Sok Kwu Islands and Cheung Chau maintain the integrity and connectivity of the cetacean habitat.

Wu Jiayi urged the government to immediately cooperate with the industry and consult relevant stakeholders, including maritime experts, ecologists, and conservation groups, to formulate and implement measures to mitigate the impact of marine traffic before the high-speed craft resumes sailing.

(WWF provided images/file images)

The foundation also mentioned that they found that the Chinese white dolphins near the South Lantau waterway have more active behaviors such as foraging and socializing after the suspension.

We observed the wandering and resting behaviors of white dolphins near the waterway, and these behavioral patterns have not been recorded in the past 5 years.

These data once again prove that the suspension of sailing has a direct impact on the activity of white dolphins in the South Lantau waters.

Wu Jiayi, manager of the cetacean conservation project, urged the government to immediately cooperate with the industry and consult relevant stakeholders, including maritime experts, ecologists, and conservation groups, to formulate and implement measures to mitigate the impact of marine traffic before the high-speed craft resumes sailing.

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