The survival rate of newborn Chinese white dolphins is alarmingly low, a study by the Agriculture, Fisheries and Conservation Department has found, sparking concerns about the future of the species in Hong Kong.
The report also highlights their "aging population" as two thirds of the dolphins are now aged 12 or above. There were only 47 white dolphins in Hong Kong last year, which were frequently sighted off Lantau.
That is the same number as quoted in 2016, the lowest since reports on the status of the dolphins were first published in 1995.
There were 88 dolphins in 2011, so the population appears to have shrunk by nearly 50 percent since.
Of the 149 confirmed white dolphin births, more than 40 percent of the calves were only observed once with their mothers before disappearing. This has sparked concerns about their low survival rate.
The report warns: "With the low survival rate of newborns, the low fecundity of reproductive females and the relatively long calving intervals, this raises serious concern for the future survival of dolphins."
In 2017, major dolphin habitats were located along the coast of west Lantau, extending from Tai O toward Fan Lau and Kau Ling Chung.
For the past seven years, dolphin habitats have consistently been located to the west of Lantau. However, the area of their habitat decreased between 2016 and 2017.
In the north Lantau region, dolphin sightings have greatly diminished in recent years, and have been largely confined to the area around Lung Kwu Chau since 2016.
Dolphin Conservation Society chairman Taison Chang Ka-tai said the population of white dolphins has continued to dwindle.
He suspects white dolphins have migrated away from the waters east and north of Lantau due to the emergence of large-scale construction projects in the vicinity in recent years, including the Hong Kong-Zhuhai-Macau Bridge and the airport's third runway.
He said the reports have clearly indicated that the waters west of the island have been one of the dolphins' known habitats for the past six years.
He also urged the Agriculture, Fisheries and Conservation Department to designate the area as a marine park to protect the dolphins living there.