Dr Kongkiart Kittiwatanawong, said the centre was conducting a dugong sighting survey in the Andaman Sea around Koh Libong and Koh Muk from February 28 through to this Tuesday. Each sortie spotted some 60 to 150 dugongs, including repeated encounters of pairs of mothers with babies, he said. He added that Trang has the biggest population of dugongs in the country and they live on sea grasses around Koh Libong and Koh Muk. Last year, more than 200 dugongs were sighted in the Trang habitat, Kongkiart said. The Phuket Marine Biological Centre is under the Marine and Coastal Resources Department.