Hong Kong's iconic pink dolphins are disappearing at an unprecedented rate, experts say.
They warn the animals could vanish altogether from the city's waters unless pollution and disruption to the marine environment are checked.
Figures due next month will show a major decline in the number of pink dolphins - also known as Chinese white dolphins - found in Hong Kong waters at any one time, says Dr Samuel Hung Ka-yiu, chairman of the Dolphin Conservation Society.
Rampant reclamation and development - including the Hong Kong-Zhuhai-Macau bridge and the planned third airport runway - combined with pollution and ever-increasing vessel traffic are believed to have hit the pink dolphin, the city's mascot for the 1997 handover.
"They are diminishing their use [of Hong Kong waters], they are not reproducing and they are dying," Hung said. "It is hard to say if they will leave Hong Kong permanently … but [the trend] will become worse and worse."
Dolphins have been recorded in Hong Kong waters since the 1600s. Hung said the number shrank from 158 in 2003 to 78 in 2011. The figure for last year, to be released next month, would be "significantly lower", he said.
Sightings of dead calves have also risen sharply, with three cases recorded last month alone. The calves are suspected to have died from contaminated milk produced by their mothers.
Concerns were highlighted when a boat party videoed a mother and other dolphins trying to support her dead calf on the water's surface last Sunday near Lung Kwu Chau Marine Park.
Janet Walker, spokeswoman for Dolphinwatch, which runs dolphin-spotting boat trips, said: "Half the dead ones every year are juveniles and babies.
"If the third runway goes ahead and when the bridge is complete, an awful lot of habitat will be lost and there will be a lot more pollution."
She added: "If the dolphins are dying it says a lot about the state of our ocean. They are a monitor of the general condition of the marine environment. If they are in trouble, so are we."