DOLPHINS are returning to the Brothers Islands, where blasting and dredging had apparently driven them away.
But researchers say their long-term prospects are not good.
The dolphins - which are pink, grey, white or mottled - have been seen feeding around the islands and elsewhere north and south of Lantau Island after divers reported they shunned the area last year.
They have been seen several times this year by marine biologists Lindsay Porter and Chris Parsons, who are doing the first study of the dolphins and are expected to come up with a management strategy within three years.
The animals' habitat is under pressure from the new airport development, which is bringing more and larger boats to the area and stirring up a lot of sediment.
Ms Porter said it was unclear whether the airport-related work was the main cause for the dolphins' disappearance last year because there was little known about their habitual movements, but the project was undoubtedly affecting them.
''They have to put up with the disturbance [of the airport], pollutants and heavy metals in the water, the destruction of their habitat and the loss of food because their habitat is being destroyed,'' Ms Porter said.