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Hong Kong dolphins lose the urge thanks to noise, pollution

Terra Daily


1st November 2004

Hong Kong's famous pink dolphins are among nature's great survivors: for decades they have managed to scratch out an existence in some of the filthiest waters in Asia.
Experts fear, however, that years of abuse of their habitat, a narrow stretch of waters off Hong Kong's western shores, may finally be taking their toll.

Urban and industrial development have poisoned the water and increasing sea traffic serving the city's booming port has not only made life tough for the dolphins, it also appears to have made the act of procreation near impossible.

"We are not seeing that many babies anymore, which suggests they are not mating as frequently," said Janet Walker, a guide with Hong Kong Dolphin Watch, the city's only official dolphin-watching tour.

Environmentalists characterise the fate of Hong Kong's dolphins as typical of the wider disregard for the once beautiful island territory.

Like the stunning views of leafy Lamma Island, which are marred by a huge smoke-belching power station, to Victoria Harbour, which is being devoured by reclamation, the dolphins have become victims of Hong Kong's pursuit of wealth.

"Habitat destruction is the single biggest threat to the dolphins -- forget the boats and ships, they can swim away from them: when they have no home to live in, that's when they die," said Samuel Hung, a doctoral student at Hong Kong University's ecology unit studying local dolphin families.

Sousa chinensis chinensis, a subspecies of the Indo-Pacific hump-back dolphin, thrives only in brackish estuarine waters.

While other groups of the species have been identified further north off the eastern shores of China, the ones in Hong Kong are among only a handful of pink examples.

Called Chinese White Dolphins, Hong Kong's creatures gain their distinct colouring from the blood that courses through microscopic blood vessels they have evolved in their skin to help cool them in the warm tropical waters.

Because they are so choosy about where they want to live, they confine their existence to a narrow stretch of water off Hong Kong's Lantau Island which, unfortunately, is also in the middle of one of the busiest stretches of waterway in the world.

Most of the coastal shipping trade between China's industrial heartland of Guangdong province and the Pearl River Delta Region passes through their habitat in the Pearl River estuary.

It is also close to a main route for international shipping that uses Hong Kong's port, the world's busiest.

Add to that the pollution that is brought to the waters, discharged from the Pear River, and the loss of habitat from reclamation needed to build the nearby international airport and the dolphins have an existence so precarious that experts are surprised they have survived this long.

"The reclamations were about the worst blow to the dolphins' habitats because it removed nooks and crannies in the coast that were breeding grounds for the fish that the dolphins eat," said Hung.

"They are adaptable and can tolerate a lot of things, but it's difficult to survive when one of your main sources of food is removed."

There is little agreement on how many dolphins are left. Estimates range from 100 to 1,000 depending on which academic is asked.

Most agree, however, that their numbers are falling.

"Every year we find about 10 or 12 dead dolphins washed up on the local beaches -- killed by boat propellers or other causes," said Walker. "And those are just the ones we find. Many more get washed away to sea or just sink to the bottom."

Hung's studies of carcasses has found that many of them have been poisoned by pollution.

"Their body tissues are full of toxins: chemical fertilisers, insecticides, heavy metals, the list goes on," said Hung.

He is not convinced by arguments that noise and pollution prevents the dolphins from mating, but he is in no doubt it is affecting their reproductive patterns.

"These poisons over time accumulate in the dolphins' bodies and attack the their immune systems and can even suppress their reproductive system," he said.

Beyond a wide scale cleaning up of Hong Kong's waters -- the prospects of which are slim thanks to poor regulation of China's environmental protection laws -- experts fear little can be done to improve the plight of the dolphins.

Awareness campaigns, including use of the dolphin as the mascot of the city's handover from Britain to China in 1997, have increased public understanding of the creatures' problems.

However, they have also raised the dolphins' profile among tourists, presenting a new set of dangers.

"A lot of private boat owners now take unofficial tours out to see the dolphins but they have no idea how to behave," said Walker. "I have seen boats get far too close to them, and that just scares them away, or worse, hurts them."