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Aim Holistic marine biodiversity conservation refers to ecosystem‐based management through marine conservation planning (MCP), based on mapping habitat protection priority areas. In practice, MCP is frequently hindered by information gaps in biodiversity distributions, particularly on a marine ecoregion scale. Species distribution modelling (SDM) can help to resolve this gap and provide information essential for MCP scenarios. We constructed habitat configurations for three coastal marine megafauna animals using SDM, then based MCP scenarios on the projected habitat configurations and tested the use of marine megafauna animals as surrogates to protect major ecosystems. Location Gulf of Thailand, Southeast Asia. Methods A MaxEnt model was used to project likely habitats for Indo‐Pacific humpback dolphins (Sousa chinensis), Irrawaddy dolphins (Orcaella brevirostris) and sea turtles in the Gulf of Thailand. MARXAN software was used to prioritize spatial configurations for habitat protection. The percentage of overlaps between MARXAN delineations and major biodiversity features in the Gulf of Thailand were calculated. Results Habitat configurations of humpback dolphins, Irrawaddy dolphins and sea turtles were projected throughout the coastal and estuarine waters along the Gulf of Thailand. MCP based on the habitat of three marine megafauna animals highlighted five critical habitats for the protection of major ecosystems in the Gulf of Thailand. Main conclusions Holistic MCP starts with mapping critical habitats for marine protected area (MPA) networks, balances MPA networks with maritime livelihood activities and alleviates conflicts between MPA management and local livelihood needs. A combination of SDM and MARXAN methods provides a cost‐effective approach to delineate MPA networks. In this approach, surrogate selection and data preparation should consider niches representative of regional ecosystem features and avoid spatial sampling bias. In coastal and estuarine waters, marine megafauna such as coastal cetaceans and sea turtles may serve as efficient surrogates to protect major ecosystems.

Defining demographic and ecological threshold of population persistence can assist in informing conservation management. We undertook such analyses for the Indo-Pacific humpback dolphin ( Sousa chinensis ) in the Pearl River Delta (PRD) region, southeast China. We use adult survival estimates for assessments of population status and annual rate of change. Our estimates indicate that, given a stationary population structure and minimal risk scenario, ~2000 individuals (minimum viable population in carrying capacity, MVP k ) can maintain the population persistence across 40 generations. However, under the current population trend (~2.5% decline/annum), the population is fast approaching its viability threshold and may soon face effects of demographic stochasticity. The population demographic trajectory and the minimum area of critical habitat (MACH) that could prevent stochastic extinction are both highly sensitive to fluctuations in adult survival. For a hypothetical stationary population, MACH should approximate 3000-km 2 . However, this estimate increases four-fold with a 5% increase of adult mortality and exceeds the size of PRD when calculated for the current population status. On the other hand, cumulatively all current MPAs within PRD fail to secure the minimum habitat requirement to accommodate sufficiently viable population size. Our findings indicate that the PRD population is deemed to become extinct unless effective conservation measures can rapidly reverse the current population trend.

Cetacean-watching tourism has become an economically important recreation industry, but can compromise cetacean viability and hence tourism sustainability. While current management tactics pay much attention on industrialized cetacean-watching tourisms, impacts of tours operated by motorized boats in inshore waters are seldom discussed. This study investigated the spatial and temporal activities of dolphin-watching tours in Sanniang Bay, China, where tours specifically focus on Indo-Pacific humpback dolphins (Sousa chinensis). The primary boat-dolphin interaction directly overlaps with a core habitat of humpback dolphins. Average tour duration was shorter than 40 min and approximately one third of time was spent on following dolphins. Monthly tour activities were extremely high in February, early May, August, and October that corresponded to Chinese national festivals. An eastward shift of primary interaction site during high-tour-activity months implies a long-term tour impacts on habitat use of humpback dolphins in northern Beibu Gulf. We urge a collaboration and coordination between boat captains, tour managers, maritime administrative, academic teams, and NGOs to systematically collect tour statistics in Sanniang Bay, including daily tour and visitor numbers, encounter duration and locations, and unsustainable maritime activities. As eco-tourisms targeting humpback dolphins and other coastal cetaceans adopting small motorized boats are rapidly growing in southeastern Asia, management guidelines involving codes of conduct, allowable daily trips, and sustainable tourism tactics are urgently needed before the tourism becomes industrialized and economically oriented. Variables and statistics presented in this study can provide a baseline proxy to help design management guidelines to minimize unsustainable impacts on the target animals.

The northern Beibu Gulf is one of the major habitats for the Indo-Pacific humpback dolphin ( Sousa chinensis ) in China. In this habitat, the core distribution zone of humpback dolphins was confined to the Sanniang Bay (SNB) and Dafengjiang River Estuary (DRE) areas. In our present research, the sediments of 14 sampling sites across the SNB and DRE waters were collected and further conducted for microbiomic and environmental analysis to explore the ecosystem characteristics of major humpback dolphin habitats in Northern Beibu Gulf. The environmental condition includes ammonia nitrogen (NH 4 + -N), nitrate nitrogen (NO 3 − -N), dissolved reactive phosphorus (DRP), sulfur content in the form of sulfuric acid (SO 4 2− -S), Fe, and heavy metals (including Cu, Zn, Cd, Pb, and As). The composition of the bacterial community was characterized by 16S ribosomal DNA analysis of the V3–V4 regions using the Illumina-based sequencing platform. The environmental characteristic of the nutrient elements and heavy metals indicated that SNB suffered more anthropogenic impact than DRE. The comparably higher concentration of NH 4 + -N, NO 3 − -N, DRP, Pb, and Cd in the SNB region was detected. The comparably higher nutrients in the SNB may have resulted in higher biomass and lower dissolved oxygen (DO) profile, which was further proved by Landsat thermal image data. The microbiome analysis showed that the DRE region was oligotrophic and SNB reflected an anaerobic environment in the sediments. Environmental factors rather than the spatial distance determined the similarity of bacterial community among different sites. Ecological associations between environmental, oceanographic, and bacterial characteristics were illustrated, which exhibited strong mutual associations. Our findings presented a feasibility that integrates empirical and remote sensing data to distinguish ecological features and evaluate ecosystem healthiness for the humpback dolphin habitats.

Background Populations of Indo-Pacific humpback dolphins ( Sousa chinensis ) in China were known to be distributed from the Beibu Gulf near the border with Vietnam to the mouth of the Yangtze River. According to existing studies, the waters around Hainan Island, China, were not considered to be part of the humpback dolphins’ distribution. Results In 2014, for the first time, we recorded humpback dolphins in waters southwest of Hainan Island. Conclusions This record expands the known southern distribution range of this dolphin in Chinese waters by more than 300 km.

Do freshwater ecosystems and their charismatic species attract sufficient public attention in global biodiversity conservation efforts? In this study, we analyzed web-based public interest, news reports, and academic research concerning freshwater cetaceans and their respective river basins. We compared these findings with those of other endangered flagship species (six species selected globally and three nationally in China) inhabiting terrestrial and marine ecosystems. Our results indicated that public interest in freshwater cetaceans remained stable over the past two decades, contributing 7% to the awareness of the basins they inhabit. Although the number of news reports and academic research on freshwater cetaceans increased significantly, by 705 and 52 respectively, the growth rate was notably slower compared to that of other endangered flagship species inhabiting terrestrial and marine ecosystems. Regions with higher attention to freshwater cetaceans were typically economically developed areas. Even in China where the freshwater cetacean conservation has recently achieved significant success, insufficient attention and local interest towards freshwater cetaceans were still underscored. Correlation analysis revealed that current news coverage and academic research were not effectively raising public interest in freshwater cetaceans. We strongly recommend launching nature education campaigns to enhance local awareness and interest in freshwater cetacean conservation, drawing insights from successful conservation efforts in other ecosystems. Effective collaboration between media and scientific agencies is essential to bridge the ‘knowing-doing’ gap, ensuring the dissemination of scientific findings to the public and academic institutions.

For the Indo-Pacific humpback dolphin, Sousa chinensis, an obligatory shallow water inshore species, the degradation of coastal habitats can have major consequences for population persistence and distribution. Off Taiwan's west coast (TWC), these animals are predominantly seen in two areas separated by a stretch of coast with only sporadic sightings, suggesting that either (a) only two sectors of TWC offer sufficiently suitable habitat for the dolphins or (b) a recent environmental change limits the population connectivity. We measured the extent of habitat destruction due to land reclamation off TWC since 1972 using a habitat integrity index (HII) and applied general linear models (GLMs) to compare HII with sightings of dolphins per unit effort (SPUE). While early Landsat data reveal extensive continuity and diversity of coastal habitats, by 2013, a total area of over 222 km² was lost to land reclamation (23 % of dolphin habitat and 40 % of dolphin foraging habitat). GLM analysis showed a significant relationship between and SPUE; the lower the lower SPUE, indicating that off TWC, the current discontinuous distribution of humpback dolphins is likely due to a different extent of habitat degradation rather than natural patchiness of their environment. We emphasize that the history of coastal habitat alteration must be considered when interpreting cetacean distribution from survey data and formulating habitat management decisions, especially in areas experiencing extensive anthropogenic coastal change.

Several cetacean species have demonstrated epimeletic behavior that relies on the tight social bonds between conspecifics. These behaviors and the corresponding vocalizations were recorded during a rare encounter with a group of Indo-Pacific humpback dolphins (Sousa chinensis) that included a presumed mother and deceased calf, in Sanniang Bay, China. The observed dolphins were divided into 2 apparent groups: 1) a central group with the presumed mother and her deceased calf, along with 1 to 6 other individuals swimming in synchrony with the presumed mother; and 2) a following group of several individuals, dispersed over varying distances from approximately 20 to > 300 m, that swam in the same direction as the central group. The mother was seen mostly supporting the calf's body using her back, anterior to the dorsal fin and posterior to the melon, while the other members of the central group exhibited standing-by behaviors (i.e., remaining close to the deceased calf but not providing aid). Whistles in this context were of a longer duration and a higher complexity in the frequency modulation compared to social contexts. Several whistle types were also repeated frequently. This paper provides a detailed description of epimeletic behavior and the whistles possibly associated with that behavior in an endangered population of Indo-Pacific humpback dolphins.

Baseline data on the distribution patterns of animals disclose the dynamic function of habitat use as it relates to the accessibility of prey, social interactions, predator-prey interactions, and interhabitat-patch mobility. Differentiated distribution patterns in sympatric animal species may imply a spatial-partitioning of habitat use. This study used minimum convex polygon and kernel density estimate techniques to measure the extent of occurrence and core habitat of the Indo-Pacific humpback dolphin (Sousa chinensis), Irrawaddy dolphin (Orcaella brevirostris), and Indo-Pacific finless porpoise (Neophocaena phocaenoides) in the central-western Gulf of Thailand. For the three cetacean species, their extent of occurrence greatly overlapped, while their core habitats were nearly disjointed, with minor overlap. Principal component analysis and discriminant analysis revealed significant differences in the habitat characteristics inside core habitats, which imply geographic separation of foraging patches between Irrawaddy dolphins, humpback dolphins, and finless porpoises. Based on the core habitat identification, we propose precautionary actions to maintain the habitat condition and integrity inside the core habitats for the three sympatric cetacean species, including revisiting the regulations and mitigation rules for local fisheries and dolphin-watching tourism; re-routing the ferry lanes to avoid the core habitats; and avoiding large-scale coastal modification, such as land reclamation and embankment, in the waters near core habitats.

Studies on the distribution and habitat characteristics of the Indo-Pacific humpback dolphin (Sousa chinensis) indicate a general preference toward estuarine environments. However, quantitative connections between this preference and estuarine characteristics are seldom investigated. Distribution of the humpback dolphin in the northern Beibu Gulf, China, was evaluated through systematically designed surveys and was compared to oceanographic characteristics from on-board measured and remotely sensed variables. The humpback dolphins' core distribution zone, measured by the 50% kernel density estimate (50% KDE), was confined to the Dafengjiang River Estuary in a 50.23 km^sup 2^ area, with a steep-edged underwater sand bar below and locally high chlorophyll-a concentration. The surface salinity distribution showed an eco-cline environment in which riverine runoff mixes with sea water in the 50% KDE. We found significant relationships between distribution probability and two oceanographic variables: (1) water depth and (2) chlorophyll-a concentration. This associates the distribution preference of humpback dolphins with regional productivity and biodiversity peaks that may facilitate prey aggregation. As humpback dolphins inhabit comparable environments in other locations throughout their range, the oceanographic features of the 50% KDE may help to provide proxies to identify other key habitats over a broader spatial scale.