The Indo-Pacific humpback dolphin (Sousa chinensis) is a threatened coastal flagship species in Asian marine ecosystems, but the distribution of its suitable habitat remains unclear. In the present study, we characterized habitat relationships and predicted potential suitable habitats for humpback dolphins in the Beibu Gulf of China and Vietnam. Maximum entropy modeling identified six discontinuous areas in the Beibu Gulf, with a total area of 4396.8 km2, as suitable habitats for humpback dolphins. Of these, three suitable habitats covering 3948.8 km2 were known habitats, and three others covering an area of 448.1 km2 at the border of China and Vietnam or in Vietnamese waters (Beilun River Estuary, Qinghua, and Rongshi) were newly identified. Exploratory line-transect surveys are strongly recommended to determine whether dolphins are present in these three areas. The predicted suitable habitat showed seasonal variation, which increased slightly in the dry season compared with that in the wet season. Bathymetry is the most important predictor for habitat suitability, in line with the known coastal distribution of humpback dolphins. Our research predicted specific suitable habitat distributions, which can be used to develop practical protection measures, such as the establishment of marine protected areas for this species to monitor, mitigate, or prohibit harmful anthropogenic activities.
Two East Asian finless porpoises (Neophocaena asiaeorientalis sunameri) in Ningbo, East China Sea, China, were observed to be bacterially infected between the fat layer and muscle layer. The microbial communities in pus samples were identified by metagenome sequencing 16S in the PacBio platform and explored the relationship between emaciation and bacterial infection. The present paper was the first report on bacterial diversity in infected tissue pus of finless porpoise. In total, 101 bacterial species were identified, and the top nine species were Rhodococcus qingshengii (26.25%), Rhodococcus jialingiae (22.43%), Ralstonia pickettii (16.03%), Moraxella osloensis (9.97%), Psychrobacter cibarius (2.97%), Flavobacterium johnsoniae (2.11%), Flavobacterium chungbukense (1.80%), Stenotrophomonas maltophilia (1.73%) and Serratia marcescens (1.62%). These main bacteria could cause various diseases or metabolic disorder, such as endocarditis, meningitis, bacteraemia, septicaemia, and so on; they also involve microbiome metabolism of amino acids (12.47%), carbohydrates (11.58%), xenobiotic biodegradation (7.81%), lipids (6.01%) and energy (4.98%). Regardless of the type of disease metabolic disorder will firstly cause body weight loss. In conclusion, these bacteria could cause diseases or metabolic disorders, resulting in emaciation of East Asian finless porpoises. Admittedly, pathogenic assay is furthermore needed to determine the mechanisms regarding the pathological phenomena.
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