Long-Term Variations in Habitat Use of Humpback Dolphins Due to Anthropogenic Activities in Western Pearl River Estuary

Abstract

Marine mammals near coastlines are highly vulnerable to human activities like rapid industrialisation, port construction, and sea reclamation, which can alter their habitat use. This study examines changes in the habitat use of Indo-Pacific humpback dolphins in the western Pearl River Estuary (WPRE) by employing a kernel density estimation model that considers physical barriers. Sighting records from systematic surveys in 2007–2008 and 2019–2020, along with remote sensing data, were used to analyse changes in shorelines and areas affected by maritime projects since 1973. Approximately 552.98 km2 of water was permanently lost to reclamation between 1973 and 2020. In 2007–2008, dolphins preferred natural shorelines, while reclamation drove them away from artificial ones. By 2019–2020, their core habitat had decreased by two-thirds, with some areas disappearing, likely due to aquaculture expansion. These results highlight the importance of adopting improved environmental assessment methodologies in the planning and regulation of aquaculture activities in the WPRE to better protect the dolphin habitat.