Ferries threat to dolphins, study finds

PUBLISHED : Wednesday, 06 June, 2012, 12:00am
UPDATED : Wednesday, 06 June, 2012, 12:00am


Boat traffic and underwater noise in Hong Kong waters is proving too much for Chinese white dolphins, and has steadily driven down their numbers over the past decade, according to a study released yesterday.

The Hong Kong Dolphin Conservation Society report found the drop in numbers was especially marked in 2003/04 and 2007/08 - falling 23 per cent in each period.

The drops coincide with increases in boat traffic, it found. In 2003 the SkyPier ferry terminal opened at Hong Kong International Airport, while in 2007 there was a sharp rise in the number of high-speed ferries between Hong Kong and Macau, said society chairman Dr Samuel Hung Ka-yiu.

'Dolphins are acoustic creatures that rely on sound to detect their environment, search for food and communicate,' he said. Since dolphin mothers and babies maintain contact by communicating through sound, 'the baby may wander off and get lost when it's too noisy'.

The society, working with Professor Bernd Wursig of Texas A&M University, started underwater acoustic studies in 2010, setting up noise measuring stations at 19 points in Hong Kong waters. 'The professor [Wursig] was amazed,' Hung said. 'He said it's a miracle that dolphins still existed in Hong Kong with such heavy traffic.'

Between 2003 and 2004, after SkyPier opened, dolphin sightings in waters off the northeast corner of the airport fell by 80 per cent, they found.

In Hong Kong waters generally, dolphin numbers have declined almost continuously from 158 in 2003 to 78 last year - a slight rebound from 75 in 2010.

Commenting on last year's up-tick, Hung said: 'The number is still low. The situation didn't worsen but there is no improvement either.'

The society is asking the Marine Department to study diverting ship traffic farther to the south of Lantau Island - further from dolphin habitats - and to establish as soon as possible proposed marine parks at Fan Lau, Lantau, and the Soko Islands.

The society has asked the Airport Authority to limit SkyPier's ship traffic, impose speed limits on the ferries and solve current problems before discussing land reclamation for a third runway.

But the authority had refused to take action to deal with the dwindling dolphin numbers, said Hung.

'With their present attitude, it would be difficult for them to pass the environmental impact assessment [for construction of a third runway].'