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Tuesday, September 6, 2016, 01:28

Airport Authority defends measures to protect dolphins

By Wang Yuke

HONG KONG - The Airport Authority is having a hard time convincing the Advisory Council on the Environment (ACE) that measures it has introduced were in fact protecting Chinese white dolphins from the noise of ferries involved in constructing the third runway project.

The Airport Authority has done a six-month survey to review the effectiveness of the Marine Travel Routes and Management Plan for High Speed Ferries on the Chinese White Dolphins, which took effect on Dec 28 last year.

At a meeting with the ACE on Monday, representatives from the Airport Authority said that vessel movements were monitored in real time by the Automatic Identification System.

It noted that all vessels complied with the 15 knot speed limit, except in one instance where the vessel's speed was marginally beyond the limit due to safety reasons.

They concluded that there was no obvious negative impact on Chinese white dolphin habitats and behavior because of high speed ferries.

They told the ACE members that dolphins could adapt to the vessels and ferries. "The Chinese white dolphins swam slowly, roughly 2 km/h when the ferry ran at a low speed when there's no boat within the range of 500 meters. They would race up to 4 km/h to avoid hazards if the ferry moved fast."

Dolphins were not present much in the daytime and were more active at night. They were foraging a third of the time and swimming the rest of the time, the Airport Authority representatives explained.

But some members of the ACE considered the methodologies used in the survey flawed and unscientific. Several argued that although researchers claimed they spotted and monitored 52 groups of Chinese white dolphins between north Sha Chau and Lung Kwu Chau, it was likely the group spotted before and after the survey were not same.

Different vessels involved in the survey have distinctive acoustic characteristics. This creates concerns by ACE members about the accuracy and credibility of the survey. The land-based monitoring technique means the range of vision is limited. Therefore, researchers can only observe dolphins close to shore and vessels within 200 km away from the station.

A few members criticized survey researchers for neglecting to compare the collected data with historical records. One person, involved in the research, said the biggest problem was that the sample size was too small.

jenny@chinadailyhk.com

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