Studies on the distribution and habitat charac-density estimate, MODIS teristics of the Indo-Pacific humpback dolphin (Sousa chinensis) indicate a general preference Introduction toward estuarine environments. However, quantitative connections between this preference Studies on the distribution and habitat characterand estuarine characteristics are seldom investi-istics of animals identify the dynamic function of gated. Distribution of the humpback dolphin in animal habitat use as it relates to the accessibility the northern Beibu Gulf, China, was evaluated of prey, social interactions, predator-prey interacthrough systematically designed surveys and tions, and inter-habitat-patch mobility (Wilson was compared to oceanographic characteristics et al., 1997; Karczmarski et al., 2000; Heithaus, from on-board measured and remotely sensed 2001; Davis et al., 2002; Braulik et al., 2012; variables. The humpback dolphins' core distri-Wang et al., 2015, 2016). Baselines for such data bution zone, measured by the 50% kernel den-provide further insights into practical habitat prosity estimate (50% KDE), was confined to the tection and management planning (International Dafengjiang River Estuary in a 50.23 km 2 area, Union for Conservation of Nature [IUCN], 2001; with a steep-edged underwater sand bar below Wilson et al., 2004; Cañadas et al., 2005; Garaffo and locally high chlorophyll-a concentration. The et al., 2011; Zhao et al., 2013; Wang et al., 2016). surface salinity distribution showed an eco-cline Relevant studies can be especially important in environment in which riverine runoff mixes with protecting key habitat for coastal cetacean species, sea water in the 50% KDE. We found significant such as the Indo-Pacific humpback dolphin (Sousa relationships between distribution probability and chinensis), which frequently interact with anthrotwo oceanographic variables: (1) water depth and pogenic activities (Jefferson, 2000; Ross et al., (2) chlorophyll-a concentration. This associates 2010; Dungan et al., 2012; Würsig et al., 2016). the distribution preference of humpback dolphins The Indo-Pacific humpback dolphin (known with regional productivity and biodiversity peaks as the Chinese white dolphin in Chinese waters) that may facilitate prey aggregation. As hump-is known to specifically rely primarily on coastal back dolphins inhabit comparable environments waters shallower than 20 m deep (Jefferson, 2000; in other locations throughout their range, the Jefferson & Karczmarski, 2001; Hung, 2008; Ross oceanographic features of the 50% KDE may help et al., 2010; Jutapruet et al., 2015). The taxonomy to provide proxies to identify other key habitats of the humpback dolphins was recently revised, over a broader spatial scale.

Coastal and estuarine waters are important ecosystems with high primary and secondary productivity, but they are prone to the impacts of habitat loss caused by anthropogenic activities. For species exclusively inhabiting coastal and estuarine waters, such as the Indo‐Pacific humpback dolphin, Sousa chinensis, irreversible habitat loss can have dramatic implications for population viability. A Landsat image database was used to determine the extent of coastal changes along the northern Beibu Gulf, where a large humpback dolphin population is found. The results were compared with the standardized sighting gradient (SPUF) determined from a questionnaire survey of fishermen and likely core habitats identified by application of a global digital elevation model. Both SPUF and likely core habitat results indicated a continuous distribution of the humpback dolphin along the northern Beibu Gulf. Landsat images revealed that 129.6 km2 of coastal waters were permanently lost in the past 40 years, 60 km2 within the likely core habitats. Although this may be considered small, the impact of such habitat loss could be substantial in some local habitats. The humpback dolphin population in the northern Beibu Gulf should be regarded as one management unit, with two or more social subunits. Immediate systematic surveys are needed to fill information gaps on true distribution range and habitat‐use patterns. Habitat protection actions for dolphins in the northern Beibu Gulf should include both core and linking habitats, including enacting protected areas in core habitats, mitigating anthropogenic impacts in likely habitats, restoring both coastal waters and surrounding landscape quality, effective treatment of industrial sewage discharge, and comprehensive environmental impact assessments for the planning of coastal development projects.

1. Habitat configuration is an important baseline to delineate protected area design, refine impact mitigation measures and define habitat protection plans for threatened species. For coastal delphinids, outlining their habitat configuration becomes a real challenge when faced with large distribution ranges that straddle international borders, leaving broad information gaps in uninvestigated areas.2. This study projected likely habitats of Indo-Pacific humpback dolphins, Sousa chinensis, in the Beibu Gulf (Gulf of Tonkin) based on occurrence data and remotely sensed oceanographic characteristics. Net primary productivity was derived to measure the ecosystem service of humpback dolphin habitats.3. Bathymetry and chlorophyll-a concentration are major variables contributing to humpback dolphin habitat configuration, which is characterized by shallow water depth and high primary productivity. Three major, likely habitats were identified in the northern Beibu Gulf from western Leizhou Peninsula to the China-Vietnam border, western Gulf of Tonkin from the Red River estuary to the central coast of Vietnam, and south-western Hainan Island. Less than 9% of likely habitats are currently protected by marine protected areas.4. Affinity to high primary productivity and shallow depths implies that prey abundance and foraging efficiency influence habitat selection by Indo-Pacific humpback dolphins. Anthropogenic activities potentially altering oceanographic characteristics may impact regional marine ecosystem functions, and hence habitat configuration. Habitat protection actions for Indo-Pacific humpback dolphins includeimplementing coordinated and systematic surveys in major habitats, associating core habitat protection with protected area networks and maritime function zoning, ensuring ecosystem function integrity within major habitats, and reducing both explicit lethal impacts and implicit anthropogenic impacts from activities that change oceanographic features. The habitat protection plan should not only consider marine habitats, but also adjacent coastal landscapes and river catchments.

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Protecting critical habitats of the Indo‐Pacific humpback dolphin, Sousa chinensis, is a hot topic of discussion for marine biodiversity conservation in China and many Southeast Asian countries. In practice, sound habitat protection action (HPA) planning often suffers from information gaps in macroscopic habitat configurations and changes in the habitat conditions of humpback dolphins. Recent publications in the journal Aquatic Conservation: Marine and Freshwater Ecosystems (AQC) have served to advance humpback dolphin conservation in Chinese waters by resolving such habitat configurations and indicating significant changes in distribution patterns and habitat characteristics under intense coastal anthropogenic activity. We highlight an integrative research framework to investigate habitat configuration and long‐term habitat changes when planning a holistic HPA programme for humpback dolphins. When constructing habitat configuration baselines, field surveys should be designed and conducted in a systematic manner to ensure survey efforts cover diverse environments equally, in either a spatially stratified or gridded pattern, to minimize potential spatial sampling biases. Long‐term habitat changes can be revealed by comparing satellite images from different decades. Changes in habitat preferences and habitat characteristics can be explored through questionnaire surveys on local ecological knowledge, associating historical occurrences with coastline features and projecting historical habitat configuration by species distribution modelling exercises. A lack of good communication and sharing of information between research and management sectors can still be an obstacle to the implementation of sound conservation practices, however, even though there is robust scientific evidence to fill knowledge gaps in distribution and habitat baselines. We have addressed the need to establish a mechanism to improve and streamline information sharing between research teams, management sectors, and stakeholder groups.

The impact of noise made by vessels on marine animals has come under increased concern. However, most measurements on noise from vessels have only taken into account the low-frequency components. For cetaceans operating in the mid- and high-frequencies, such as the Indo-Pacific humpback dolphin (Sousa chinensis), mid- to high-frequency noise components may be of more concern, in terms of their potential impacts. In this study, noise made by a small high-speed boat was recorded using a broadband recording system in a dolphin watching area focusing on the effects on humpback dolphins in Sanniang Bay, China. The high-speed boat produced substantial mid- to high-frequency noise components with frequencies to >100 kHz, measured at three speeds: ∼40, 30, and 15 km/h. The noise from the boat raised the ambient noise levels from ∼5 to 47 decibels (dB) root-mean-square (rms) across frequency bands ranging from 1 to 125 kHz at a distance of 20 to 85 m, with louder levels recorded at higher speeds and at closer distances. To conclude, the noise produced by the small high-speed boat could be heard by Sousa chinensis and therefore potentially had adverse effects on the dolphins.

1. In Chinese and South-east Asian waters, the coastal and estuarine environments are important habitats for the Indo-Pacific humpback dolphin (Sousa chinensis).Coastal and estuarine maritime engineering (CEME), including land reclamation, embankment or shoreline armouring, harbour construction and marine farming, permanently changes coastal environments and threatens the long-term persistence of marine biota and ecosystems. Such impacts on humpback dolphin viability, however, are rarely discussed.

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