The number of Indo-Pacific humpback dolphins, also known as Chinese white dolphins and pink dolphins, seen around Hong Kong has gone up since high-speed ferry traffic paused due to the coronavirus.
The calm water allowed the threatened species to make a comeback, scientists said. Marine scientist Lindsay Porter of the University of St. Andrews said the animals were moving back into parts of the Pearl River Delta that they typically avoided because of the ferries that connect Hong Kong and Macau.
Dolphin numbers in the area had jumped by up to 30% since March when the ferry traffic was suspended, allowing scientists a rare opportunity to study how underwater noise affected their behavior, she said.
“These waters, which were once one of the busiest thoroughfares in Hong Kong, have now become very quiet,” said Porter, who has studied dolphins for three decades from Hong Kong.
From a small rubber boat, Porter and her team drop microphones into the water and use drones to look out for dolphins. The research suggested the dolphins had adapted more rapidly than expected to the quiet environment, Porter said.
Scientists think there are about 2,000 dolphins in the area. A Hong Kong government survey from 2019 found only about 52 dolphins entered the waters around the Asian financial hub.
“I sometimes feel that we’re studying the slow demise of this population (of dolphins), which can be really sad,” Porter said.
Hong Kong’s conservation plans have focused on opening marine parks, where ship traffic is limited but not banned. Three of those areas are frequently visited by dolphins.
The Hong Kong WWF, a conservation group, and Porter said such measures were inadequate as dolphins were still in danger of being hit by ferries as they moved between the protected areas.
“If we did have a comprehensive management plan in Hong Kong with more effective conservation measures, we might be able to quickly stop the decline in the dolphin population,” Porter said.
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