“Chinese white dolphins are very beautiful, and have long been part of the history here,” said Dr Lawrence McCook, head of oceans conservation at WWF-Hong Kong. “But they are in a dire situation.”

Since the construction of the Hong Kong-Zhuhai-Macau Bridge started in 2012, the dolphins largely disappeared from northeast Lantau and concentrated in southern and western Lantau, where the long and continuous natural coastline provides them with abundant prey, WWF conservationists said.

Along with 12 other areas, including Sanxiakou and the Dajin and Xiaojin Islands to the west of Zhuhai, WWF-Hong Kong proposed prioritising “core” protection zones in southern and western Lantau for conservation, with fishing and development banned.

Three buffer zones, which would allow less harmful human activities but be managed like marine parks, were also proposed to connect to the core zones and act as ecological corridors, allowing the dolphins to travel safely.

WWF backs Hong Kong teen’s campaign to save rare Chinese white dolphins

WWF hoped the conservation zones could be set up by 2024 with the help of the local authorities, as well as its partners at various universities across the region.

About 2,000 of the iconic pink sea mammals, officially known as the Indo-Pacific humpback dolphins, live in the waters of the Pearl River Delta.

They are also found across Asia, including in Bangladesh, Malaysia, Singapore, Taiwan and Vietnam, but their numbers are decreasing, and the population in the Pearl River Delta is likely to be the largest in the world.

The International Union for Conservation of Nature’s Red List lists the Chinese white dolphin as vulnerable. It is particularly susceptible to habitat loss and degradation due to a boom in development works. Shipping and illegal fishing also pose threats to its food sources, while pollution, marine rubbish and climate change are exacerbating the problem.

Hong Kong’s Chinese white dolphin numbers remain critically low

Dr Lindsay Porter, a senior research scientist at the University of St Andrews who has worked on the dolphins for more than 20 years, said the species also reproduced slowly and many of their offspring died prematurely.

“Year after year, it’s becoming tougher for the dolphins to survive in Hong Kong,” she said. “If Hong Kong’s marine environment is not healthy enough to sustain the dolphins, then it is also not healthy enough for the fish we eat every day.”

Porter said she was willing to support the WWF’s plan by joining the monitoring efforts and helping with reporting illegal fishing to the authorities.

Doris Woo Ka-yi, an oceans conservation officer with WWF-Hong Kong, said the government should also widen environmental impact assessments to include underwater noise, which affects the dolphins’ hunting and navigating abilities.

The NGO also suggested improved regulation of fishing, marine traffic, coastal development and formulation of a cross-boundary water quality management plan to handle marine pollution.

“The government needs to fulfil Hong Kong’s obligation under the Convention of Biological Diversity and its own commitments to the dolphins under the city’s Biodiversity Strategy and Action Plan,” Woo said. “We cannot wait any longer.”

Officials from the Environmental Protection Department and the Agriculture, Fisheries and Conservation Department said they would consider the suggestions.

The EPD also said a marine park on the southwest coast of Lantau Island had been established on April 1, while two other marine protection zones around Lantau would be set up by 2022 and 2023 respectively.