Neophocaena Research Articles

A real-time passive acoustic monitoring system to detect Yangtze finless porpoise clicks in Ganjiang River, China

Phocoenidae live in fresh, coastal waters where they often share a significant portion of their habitat with humans. As a result, local activities (e.g., coastal fisheries and shipments) cause underwater noise pollution and threaten their ecosystem. To better conserve the habitat of porpoises, we aimed to study their activities in these waters by recording their echolocation clicks using a passive acoustic monitoring (PAM) system. However, because the off-line PAM instruments were often used in the past that need to be periodically deployed and recovered, data acquisition is typically obtained and analyzed in batches, rather than in real-time. A real-time PAM detection system would help minimize the impact of underwater noise on approaching porpoises. Furthermore, issues of bad quality data–with gaps due to loss or damage of the off-line PAM instruments–could be avoided with a real-time detection system. Therefore, in this study, we developed the Real-time Porpoise Click Detector-II (RPCD-II), equipped with a digital hydrophone, main memory (2 TB storage), a central processing unit, and a wireless transmission module. We deployed the RPCD-II under a docked fishing vessel at the Ganjiang River in Yangzi Zhou Town Fisheries Village, Nanchang City (8–9 December 2021), where it recorded signals of Yangtze finless porpoise and produced a real-time report. To validate the results of RPCD-II, another underwater sound recorder, the SoundTrap 300HF (ST), was also set up (as a control device) under the docked fishing vessel. Both devices recorded consistent results of 9330 clicks, further demonstrating RPCD-II’s ability for the real-time detection of Yangtze finless porpoise in the field.

Ecological risk assessment on the habitats of typical aquatic species in the middle reach of the Yangtze River: Implication for three gorges reservoir operation

The operation of a reservoir may change natural hydrological processes, thus affecting the habitat of aquatic organisms. However, the risks posed by reservoirs on aquatic organisms remain to be fully evaluated. In this study, a risk assessment model was established to assess the ecological risk of reservoir flow regulation based on the consequences of deviating from the environmental flow range of an aquatic habitat. We applied this model to the Three Gorges Reservoir by obtaining the risk time series of different aquatic habitats in the Yangtze River before and after the construction of the reservoir. The risk analysis results showed that when habitat discharge is above or below the appropriate range of environmental flows, the ecological risk increases. The Chinese sturgeon, four major Chinese carp species, and finless porpoise habitats were identified to be at low-flow risk, low-flow risk, and high-flow risk, respectively. We suggest that the habitat flows of Chinese sturgeon, four major Chinese carp species, and finless porpoise during the spawning period should not be less than 6,850, 7,000, and 13,500 m3/s, respectively. The results of this study could help river managers optimize reservoir operations to minimize risks and maximize ecological benefits.

A metagenomic insight into the Yangtze finless porpoise virome.

The Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) inhabiting the Yantze River, China is critically endangered because of the influences of infectious disease, human activity, and water contamination. Viral diseases are one of the crucial factors that threatening the health of Yangtze finless porpoise. However, there are few studies which elaborate the viral diversity of Yangtze finless. Therefore, this study was performed to investigate the viral diversity of Yangtze finless by metagenomics. Results indicated that a total of 12,686,252 high-quality valid sequences were acquired and 2,172 virus reads were recognized. Additionally, we also obtained a total of 10,600 contigs. Phages was the most abundant virus in the samples and the ratio of DNA and RNA viruses were 69.75 and 30.25%, respectively. Arenaviridae, Ackermannviridae and Siphoviridae were the three most predominant families in all the samples. Moreover, the majority of viral genus were Mammarenavirus, Limestonevirus and Lambdavirus. The results of gene prediction indicated that these viruses play vital roles in biological process, cellular component, molecular function, and disease. To the best of our knowledge, this is the first report on the viral diversity of Yangtze finless porpoise, which filled the gaps in its viral information. Meanwhile, this study can also provide a theoretical basis for the establishment of the prevention and protection system for virus disease of Yangtze finless porpoise.

Habitat configuration of the Yangtze finless porpoise in Poyang Lake under a shifting hydrological regime.

Habitats of freshwater cetaceans are under increasing threats of deterioration globally. A complete understanding of long-term variations of habitat configurations is therefore critical. Poyang Lake in China contains a large and stable population of the Yangtze finless porpoise, a critically endangered freshwater cetacean species. However, constant water decline and intensified human activities in the lake since 2000 have led to uncertainty for porpoise conservation. We address this issue via remote sensing and hydrodynamic modeling of nine environmental variables during different seasons over the past two decades. The MaxEnt model was used to extrapolate changes in likely habitat configurations of the porpoise, and MARXAN algorithms delineated habitat protection priorities in different seasons. Results illustrate that flow velocity, water depth, Chl-a concentration, distance to grassland and boats greatly affect the porpoise distribution. Shifts in these environmental variables can lead to significant habitat decreases in all seasons. In particular, unstable hydrological regimes may force the porpoises to live in habitats with lower water depths for suitable flow velocity conditions in the dry season, and habitats are increasingly infringed by grassland and mudflats. High protection priority areas such as the northern channel and the estuaries of the tributaries urgently need long-term systematic and targeted surveys of ecosystem functionality and flexible management of anthropogenic activities. Combining remote sensing with hydrodynamic and species distribution models can also assist in understanding the situation of other aquatic species.

Underwater Noise Level Recordings from a Water Intake Pontoon and Possible Impacts on Yangtze Finless Porpoises in a Natural Reserve.

Simple SummaryRelocation of endangered freshwater cetaceans in natural reserves is an effective conservation strategy to recover their populations. However, due to historical reasons, some natural reserves have facilities that cannot be removed, such as water intake pontoons that are important for residents nearby. These facilities generate underwater noise which may affect cetaceans. To investigate the potential impacts of underwater noise from water intake pontoons on freshwater cetaceans, this study measured such noise within a Yangtze finless porpoise (Neophocaena asiaeorientalis) nature reserve, analyzed its effects on porpoise behavior, vocalization, and hearing, and explored porpoise adaptation to the transient holding pen environment. This study provides a reference for assessing whether human facilities have impacts on freshwater cetaceans.Underwater noise pollution caused by human activities may affect freshwater cetaceans to different degrees. To analyze the impacts of water intake pontoons on Yangtze finless porpoises (Neophocaena asiaeorientalis), this study collected underwater noise data from such a pontoon in a nature reserve, plotted the power spectral density of acoustic signals, and calculated the root mean square sound pressure levels and the magnitude of sound source levels. The 1/3-octave sound pressure level root mean square values at the transient holding pens were <18.0 kHz, 39.5−60.0 kHz, which were slightly higher than the Yangtze finless porpoise hearing threshold curve values and therefore could be perceived. However, the results indicated that the porpoises would not develop a temporary hearing threshold shift. Meanwhile, pontoon noise did not interfere with the porpoises’ high-frequency acoustic signal nor did it affect their echolocation; it significantly interfered with their low-frequency acoustic signal, however, and the mother–child communication of the finless porpoises was affected, but this effect was quickly compensated due to the limited space range of the holding pens. Through this study of Yangtze finless porpoises, this paper provides a reference for assessing whether human facilities have impacts on freshwater cetaceans.

Impacts of Sand Mining Activities on the Wetland Ecosystem of Poyang Lake (China)

Increasing anthropogenic activities are threatening freshwater ecosystems worldwide. Sand mining in Poyang Lake has significantly impacted the wetland ecosystem over the past 20 years, yet a quantitative analysis of these impacts remains insufficient. Here, we used 63 Landsat images taken from 2000 to 2020 along with the support vector machine (SVM) method and a retrieval model of suspended sediment concentration (SSC) to identify sand mining vessels and areas affected by sand mining. Then, we analyzed the changes in landscape patterns in the areas affected by sand mining. The potential impact of underwater noise generated by sand mining vessels on Yangtze finless porpoises was analyzed by a sound propagation model. The number of sand mining vessels in Poyang Lake during the flood, normal, and dry seasons increased from 2000 to 2016 but rapidly decreased from 2017 to 2020. Sand mining vessels were mainly distributed in the northern channel from 2000 to 2006, moved toward the center of the lake from 2007 to 2010, then moved northward in 2017. Within the areas affected by sand mining, water and mudflats declined, grassland and sandbars increased, and the landscape discontinuity increased. The habitat of the Yangtze finless porpoise affected by underwater noise from sand mining vessels in all seasons has significantly increased overtime. The mean area of the affected habitats was 70.65% (dry), 64.48% (normal), and 63.30% (flood) of the total habitat areas. The porpoise habitats in the northern channel and the west branch of the Ganjiang River are more seriously affected by the underwater noise of sand mining vessels than the southern lake. The impact of sand mining activities on wetland landscape and aquatic species demands systematic investigation in the future.

Communication sounds produced by captive narrow-ridged finless porpoises (Neophocaena asiaeorientalis)

Communication sounds produced by captive narrow-ridged finless porpoises (Neophocaena asiaeorientalis)

Use of passive acoustic monitoring to document the distribution of the Indo‐Pacific finless porpoise in the south‐east region of Pearl River estuary, China: Implications for conservation and management

Abstract The Pearl River estuary in Guangdong is home to the Indo‐Pacific humpback dolphin (Sousa chinensis) and the Indo‐Pacific finless porpoise (Neophocaena phocaenoides). However, limited data are available for the latter species. Line‐transect passive acoustic monitoring surveys were conducted to investigate the distribution of the Indo‐Pacific finless porpoise in the Pearl River estuary in the period July to November 2019. The south‐east region of the Pearl River estuary is an important habitat for the Indo‐Pacific finless porpoise, and more than half of the acoustic detections were within 2 km of islands, concentrated around the uninhabited islands of Soko, Sanmen and Aizhou. The habitat extents of Indo‐Pacific finless porpoises in the survey areas were estimated as 209.04, 761.81 and 976.41 km2 using 50, 90 and 95% kernel densities, respectively. The 50% kernel density area was mainly around the aforementioned islands and is a priority candidate for protected area status. This is the first report of the distribution and critical habitat of the finless porpoise in the study area. Given the increasing human development in the Pearl River estuary, the results provide important data to help inform the protection of the habitat of finless porpoise in the context of marine planning and development, and promote the establishment of marine protected areas and stronger fisheries management measures.

Insights on Gut and Skin Wound Microbiome in Stranded Indo-Pacific Finless Porpoise (Neophocaena phocaenoides).

The gut microbiome is a unique marker for cetaceans’ health status, and the microbiome composition of their skin wounds can indicate a potential infection from their habitat. Our study provides the first comparative analysis of the microbial communities from gut regions and skin wounds of an individual Indo-Pacific finless porpoise (Neophocaena phocaenoides). Microbial richness increased from the foregut to the hindgut with variation in the composition of microbes. Fusobacteria (67.51% ± 5.10%), Firmicutes (22.00% ± 2.60%), and Proteobacteria (10.47% ± 5.49%) were the dominant phyla in the gastrointestinal tract, while Proteobacteria (76.11% ± 0.54%), Firmicutes (22.00% ± 2.60%), and Bacteroidetes (10.13% ± 0.49%) were the dominant phyla in the skin wounds. The genera Photobacterium, Actinobacillus, Vibrio, Erysipelothrix, Tenacibaculum, and Psychrobacter, considered potential pathogens for mammals, were identified in the gut and skin wounds of the stranded Indo-Pacific finless porpoise. A comparison of the gut microbiome in the Indo-Pacific finless porpoise and other cetaceans revealed a possible species-specific gut microbiome in the Indo-Pacific finless porpoise. There was a significant difference between the skin wound microbiomes in terrestrial and marine mammals, probably due to habitat-specific differences. Our results show potential species specificity in the microbiome structure and a potential threat posed by environmental pathogens to cetaceans.

Biofilm formation, antimicrobial assay, and toxin-genotypes of Clostridium perfringens type C isolates cultured from a neonatal Yangtze finless porpoise.

This is a culture-dependent study with the objective of pure culturing and characterizing pathogenic bacteria from the blowhole, lung, stomach and fecal samples of a neonatal crucially endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) that died 27days after birth. Bacteria were inoculated using a swab onto blood and MacConkey agar plates and representative isolates were identified through 16S rRNA gene sequence analysis. A total of three Clostridium perfringens type C strains from the fecal samples were isolated. Toxin genes, including cpa, cpb and cpb2, were detected by PCR amplification, whereas the etx, iap and cpe genes were not detected. Biofilm formation of the three strains was then examined. Only one strain was capable of biofilm formation. In addition, isolates showed strong resistance against the antibiotics amikacin (3/3), erythromycin (1/3), gentamicin (3/3), streptomycin (3/3), and trimethoprim (3/3), while sensitivity to ampicillin (3/3), bacitracin (3/3), erythromycin (2/3), penicillin G (3/3), and tetracycline (3/3). The results suggested C. perfringens type C could have contributed to the death of this neonatal porpoise.

Identifying High Stranding Risk Areas of the Yangtze Finless Porpoise via Remote Sensing and Hydrodynamic Modeling

Freshwater cetaceans that inhabit river basins with seasonally changing hydrological regimes have a higher risk of stranding, leading to increased mortality and population decline. In Poyang Lake, the stranding risk of the critically endangered Yangtze finless porpoise are high, due to the significant differences in hydrological and landscape conditions between the flood and dry seasons. However, this stranding information is not well recorded, resulting in poorly guided investigation and rescue efforts. We here employ remote sensing and hydrodynamic modeling to obtain four evaluation indicators in dry, normal, and flood scenarios in Poyang Lake. Results show that nearly 50% of the largest habitat range of the porpoises in the flood season will be land areas during the dry season, and that landscape fragmentation between land and water has increased over the past three decades. In all scenarios, the mean water depth of the habitat varied from 1.77 to 4.89 m from September–February. In the dry scenario, about 59% of the habitat experiences a water depth of &lt;1 m within 15 days. The high stranding risk area is 284.54 km2 in the dry scenario, &gt;251.04 km2 in the normal scenario, and &gt;90.12 km2 in the flood scenario. High-stranding risk areas are located within city boundaries, where porpoise stranding cases have been recorded, especially in Duchang, which has the most high-risk areas in all scenarios. In all scenarios, the high stranding risk area has an average bathymetry of 7.81 m and an average water depth between 1.75 and 5.54 m. Our results can guide future investigations to establish sound stranding networks, and the methods proposed here are also applicable to studies of other freshwater cetaceans facing severe stranding risk.

Evaluation of the survival of Yangtze finless porpoise under probabilistic hesitant fuzzy environment

Considering the significant advantages of probabilistic hesitant fuzzy sets (PHFSs) in the multicriteria decision-making (MCDM) problems and the limitations of existing methods for PHFSs, we develop an improved probabilistic hesitant fuzzy MCDM (PHF-MCDM) model based on distance measure of probabilistic hesitant fuzzy elements (PHFEs) in this study. First, the hesitant degree is proposed to measure the hesitation caused by the multiple membership degree and the corresponding preferences of decision-makers in the PHFEs, then we put forward a series of distance measures and corresponding similarity measures of PHFE. Afterwards, we introduce the axiomatic definition of PHF entropies for PHFE, and then present the relation between distance measure and entropy measure. Finally, we develop a PHF-MCDM model that can solve completely unknown attribute weights, and provide a case study of Yangtze finless porpoise protection to verify the effectiveness of the proposed methods. Meanwhile, a comparison analysis with the previous method and sensitivity analysis are discussed.

Blood Transcriptome Analysis Reveals Gene Expression Differences between Yangtze Finless Porpoises from Two Habitats: Natural and Ex Situ Protected Waters

The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis, YFP) is a critically endangered small odontocete species, mainly distributed in the middle and lower reaches of the Yangtze River, Poyang Lake, and Dongting Lake. Under the influence of human activities, many factors are threatening the survival and reproduction of YFPs in their natural habitat. Ex situ conservation is of great significance to strengthen the rescuing conservation of YFPs by providing suitable alternative habitats and promoting the reproduction and growth of the ex situ population. To reveal the differences in gene expression of YFPs in natural and ex situ protected waters, and to investigate the effects of environmental factors on YFPs and their mechanisms, we performed transcriptome sequencing for blood tissues of YFPs collected from natural waters and ex situ protected waters. Using RNA-seq we identified 4613 differentially expressed genes (DEGs), of which 4485 were up-regulated and 128 were down-regulated in the natural population. GO analysis showed that DEGs were significantly enriched in entries related to binding, catalytic activity, and biological regulation; KEGG analysis showed that DEGs were enriched mainly in signal transduction, endocrine system, immune system, and sensory system-related pathways. Further analysis revealed that water pollution in natural waters may affect the hormone secretion of YFPs by altering the expression pattern of endocrine genes, thus interfering with normal endocrine activities; noise pollution may induce oxidative stress and inflammatory responses in YFPs, thus impairing the auditory function of YFPs. This study provides a new perspective for further research on the effect of habitat conditions on the YFPs and suggests that improving the habitat environment may help in the conservation of YFPs.

Characterisation of Crassicauda fuelleborni nematode infection in Indo-Pacific finless porpoises (Neophocaena phocaenoides) using postmortem computed tomography.

Nematodes of the genus Crassicauda are parasites that infect various body tissues of cetaceans, including the mammary glands which can influence the reproductive output and hence threaten the survival of endangered cetacean populations. In this study, postmortem computed tomography (PMCT) was used to characterise lesions related to Crassicauda fuelleborni infections in stranded Indo-Pacific finless porpoises (Neophocaena phocaenoides) from Hong Kong waters. Using PMCT and subsequently verified by conventional necropsy, Crassicauda-related lesions were found in 52% of finless porpoises examined (n = 13/25), including both males and females. These parasitic lesions were mostly located in the ventral abdominal muscles in both sexes and situated in proximity to the mammary glands in females. C. fuelleborni infections were also found in the male reproductive organs, which to our knowledge have not been reported in this cetacean species previously. PMCT characteristics of the lesions were also correlated with the gross appearance observed at necropsy and the chronicity of the parasitic infections. In conclusion, this study established the use of virtopsy, particularly PMCT, to characterise C. fuelleborni infections in stranded finless porpoises for the first time, which is non-invasive and can be used prior to conventional necropsy to aid disease diagnosis and targeted sampling. This technique can be extended to other species of cetaceans and parasites, as well as being used in the retrospective analysis of past PMCT scans to deepen our understanding of the prevalence, health impacts, and ecological implications of parasitic infection in cetaceans.

Association between porpoise presence and fish choruses: implications for feeding strategies and ecosystem-based conservation of the East Asian finless porpoise.

The associations between feeding activities and environmental variables inform animal feeding tactics that maximize energetic gains by minimizing energy costs while maximizing feeding success. Relevant studies in aquatic animals, particularly marine mammals, are scarce due to difficulties in the observation of feeding behaviors in aquatic environments. This data scarcity concurrently hinders ecosystem-based fishery management in the context of small toothed-cetacean conservation. In the present study, a passive acoustic monitoring station was deployed in an East Asian finless porpoise habitat in Laizhou Bay to investigate potential relationships between East Asian finless porpoises and their prey. The data revealed that porpoises were acoustically present nearly every day during the survey period. Porpoise detection rates differed between spring and autumn in concert with activities of fish choruses. During spring, fish choruses were present throughout the afternoon, and this was the time when porpoise vocalizations were the most frequently detected. During autumn, when fish choruses were absent, porpoise detection rates decreased, and diurnal patterns were not detected. The close association between fish choruses and finless porpoise activities implies an "eavesdropping" feeding strategy to maximize energetic gains, similar to other toothed cetaceans that are known to engage similar feeding strategies. Underwater noise pollution, particularly those masking fish choruses, could interrupt finless porpoises' feeding success. Fisheries competing soniferous fishes with finless porpoise could impact finless porpoise viability through ecosystem disruption, in addition to fishing gear entanglement.

Multilocus DNA metabarcoding diet analyses of small cetaceans: a case study on highly vulnerable humpback dolphins and finless porpoises from the Pearl River Estuary, China.

Accurate diet identification of top predators is crucial to fully understand their ecological roles. Compared to terrestrial animals, gathering dietary information from cetaceans is notoriously difficult. Here, we applied a multilocus metabarcoding approach to investigate the diet of vulnerable Indo-Pacific humpback dolphins and Indo-Pacific finless porpoises from the Pearl River Estuary (PRE), China. Our analyses identified 21 prey fish species from the 42 humpback dolphin stomachs, as well as 10 species of fish and 1 species of cephalopod from the 13 finless porpoise stomachs. All of the taxa were assigned to the species level, highlighting that the multimarker approach could facilitate species identification. Most of the prey species were small- and medium-sized fishes that primarily fed on zooplankton. The calculated similarity index revealed a moderated dietary overlap between the 2 cetaceans, presumably due to the feeding of the 2 predators in association with fishing vessels in the PRE. A more diverse diet was observed in humpback dolphins in the closed fishing season compared to the fishing season, implying the influence on the dolphin diet due to the availability of commercial fishery resources. However, according to the results of species rarefaction curves, our findings on the feeding habits of the 2 cetaceans are still limited by insufficient sample size and therefore should be interpreted with caution. This study represents a first attempt to apply the multilocus DNA metabarcoding technique in the diet analysis of small cetaceans, although more efforts are needed to improve this type of analysis.

Relationship of stranded cetaceans in Thai territorial waters to global populations: Mitochondrial DNA diversity of Cuvier's beaked whale, Indo Pacific finless porpoise, pygmy sperm whale, and dwarf sperm whale.

Cetaceans inhabit oceans throughout the world. Four specific odontocetes, namely Cuvier's beaked whale (Ziphius cavirostris), Indo Pacific finless porpoise (Neophocaena phocaenoides), pygmy sperm whale (Kogia breviceps), and dwarf sperm whale (Kogia sima), have occasionally been found stranded along Thailand's coastal waters (the Andaman Sea and the Gulf of Thailand). Although shared haplotypes of each species for many locations have been found, and some species have revealed genetic structure through haplotype networks, cetaceans in Thai waters have never been investigated in terms of comparing haplotypes to those that have existed before. Herein, we have illustrated the matrilineally phylogeographic relationships among worldwide populations through Bayesian Phylogenetic tree computations using Markov Chain Monte Carlo (MCMC) and Median-Joining Networks (MJNs). Unique haplotypes of the control region mitochondrial DNA of Thai odontocetes were found for all species. Moreover, a high degree of worldwide haplotype diversity (hd) above 0.8 among the four species was detected, while the lowest degree of nucleotide diversity (π) was observed in the Indo Pacific finless porpoise (1.12% ± 0.184%). An expansion of the effective female population size worldwide of three odontocete species was detected using Bayesian Skyline Reconstruction, but this did not include the Indo Pacific finless porpoise. Because Thai seas are located within the Indo Polynesian province, where this biodiversity hotspot exists, we speculate that these odontocetes may also inhabit specific habitats within the Malay Peninsula and Thailand's territorial waters. Therefore, closer attention and monitoring of these cetacean populations will be necessary for future conservation efforts.

Launching underwater bioacoustics in Asia by Whitlow W. L. Au

Whitlow W. L. Au combined biosonar science with engineering. His studies influenced so many students in Asia no matter what their specialities, such as physiology, morphology, and physics. The epoch-making book “The Sonar of Dolphins” is an ideal example of his interdisciplinary approach. Whit educated young researchers in various ways even he did not notice. He led discussion among scientists that motivated current and new generations to conduct underwater and terrestrial bioacoustic research in the lab, in the forest and in the ocean. Quite a few attendees were from Asia at the series of biosonar symposiums in 1991 Moscow, in 1994 Harderwijk, and in 1998 Algarve, but the symposium held in 2009 Kyoto accommodated nearly 200 international specialists and half of them were Asian. An example of his influence was the towed and fixed passive acoustic monitoring in the Yangtze River, China, which revealed a range-wide distribution of finless porpoises collaborating with an international team. These techniques were applied later in India, Thailand, Malaysia, Nepal, Taiwan, Hongkong, and many other areas including Japan for the impact assessment of offshore wind farm developments. We owe him all the outcomes of underwater biosonar studies in Asia.

Can the “10-year fishing ban” rescue biodiversity of the Yangtze River?

Can the “10-year fishing ban” rescue biodiversity of the Yangtze River?

Radiological Investigation of Gas Embolism in the East Asian Finless Porpoise (Neophocaena asiaeorientalis sunameri)

Cetaceans have long been considered biologically adapted to suffer no adverse effects from diving-related tissue gas tension. However, increasing reports of gas embolism in cetaceans inhabiting European, Mediterranean and American waters have challenged the conventional understanding of marine mammal diving physiology. In human hyperbaric medicine, virtopsy techniques such as post-mortem computed tomography (PMCT) facilitate the visualization of gas embolism and could be performed adjunct to conventional autopsy. This research presents the first case of gas embolism identified in an East Asian finless porpoise inhabiting Asian waters. Massive gas embolic lesions were found in the liver, which had been compressing both the lungs and abdominal organs, and signs of pneumonia and parasitic infection were observed in both lungs. It is hypothesized that this porpoise might have been unable to expelin vivogas bubbles from its circulation due to pulmonary dysfunction. Consequently, gas bubbles agglomerated in the liver, resulting in the development of gas embolic lesions. The findings of the present study provide insights into the occurrence of gas embolism in the East Asian finless porpoise, highlighting the potential of PMCT as a promising tool for the diagnosis of gas embolism in stranded cetaceans.