Yangtze Finless Porpoise Research Articles

Yangtze finless porpoise (Neophocaena asiaeorientalis) prey fish diversity based on environmental DNA metabarcoding

Abstract Knowledge of the feeding habits of the Critically Endangered Neophocaena asiaorientalis (Yangtze finless porpoise, YFP) is vital for the management and protection of this species. However, stringent protections implemented in 2020 dictate that only non‐invasive methods may be used to gain information. Therefore, environmental DNA (eDNA) metabarcoding was used to obtain YFP prey diversity and community structures from different environmental samples collected from YFP habitat in April 2021. Sampling strategies for using eDNA to monitor the YFP were explored. Of the 63 fish species detected, more species were detected in samples from surface water than in samples from deeper water and sediment, but the diversity and community structures of fish in the samples from surface water, deeper water, and sediment did not significantly differ. The number of YFP sequences in the main lake area of Poyang Lake was significantly higher than that in other sampling areas. The YFP sequence number, operational taxonomic unit (OTU) number, and OTU occurrence frequency in surface water samples were higher than those in deeper water samples. Eighteen previously verified species of YFP prey fishes were detected, with more species detected in water samples than in sediment samples. The sequence numbers of the YFP and their prey fishes Ctenopharyngodon idella, Pseudolaubuca engraulis, and Tachysurus argentivittatus were significantly positively correlated, indicating that YFP preferentially selected these three species. Surface water samples yielded good results for the convenient and non‐invasive eDNA metabarcoding method of monitoring the feeding habits of this flagship species and for identifying early signals of YFP responses to changes in prey fish communities. The creation of critical conservation areas, eDNA monitoring standards, and emergency rescue plans are vital for YFP conservation.

LEVERAGING MACHINE LEARNING AND REMOTE SENSING FOR WILDLIFE CONSERVATION: A COMPREHENSIVE REVIEW

In recent years, the application of machine learning and remote sensing technologies in wildlife conservation has demonstrated tremendous promise. This article provides a comprehensive overview of the advancements in these fields and the impact they have had on various aspects of wildlife conservation. These technologies contribute to more efficient and effective conservation strategies by automating species identification, mapping and monitoring habitats, tracking population dynamics, detecting wildlife crime, and analysing animal vocalisations. This article talks about the development of machine learning algorithms capable of classifying bird and amphibian calls, differentiating fish species, and identifying plant species such as orchids and cacti has made automated species identification possible. Incorporating machine learning algorithms with remote sensing techniquesprovides significant advantages for mapping and monitoring habitats. This article discusses that images captured by camera trapswhen combined with acoustic analysis, can help in monitoring population by enabling automated detection and tracking. These technologies provide efficient and non-invasive approaches to monitor and manage animal populations, from estimating animal density using passive acoustics to identifying and tracking endangered species such as tigers, cheetahs, and sea turtles using camera trap images. The analysis of animal vocalisations using machine learning techniques has revealed information about species behaviour, population dynamics, and habitat quality. Examining the acoustic communication of species such as black rhinoceros and Yangtze finless porpoise has been the focus of research. Acoustic analysis provides a non-invasive method for comprehending the communication patterns of animals and their implications for conservation efforts. By utilising artificial intelligence and remote sensing data, conservationists can make informed decisions and take targeted actions to protect and preserve endangered species and their habitats. These technologies continued development and application hold great promise for the future of wildlife conservation.

A Drone Study of Sociality in the Finless Porpoise Neophocaena asiaeorientalis in the Ariake Sound, Japan

The social structure of animal populations is a fundamental component of their biology, influencing gene flow, habitat use, competition and co-operation around resources, and communication. However, ecological and social relationships can be challenging to describe in most marine mammals, who spend the majority of their lives underwater. The finless porpoise (Neophocaena asiaeorientalis) is one such cetacean species with a largely unknown social structure. Recent advances in drone technology enable more systematic surveys, photogrammetry, and photo-identification for diverse animal species. The present study aimed to validate new survey methods and provide a preliminary description of the spatiotemporal distribution of free-ranging finless porpoises in the coastal open-sea area of Ariake Sound, Japan. A vertical take-off and landing (VTOL) drone equipped with an action camera yielded GPS location datasets through line and area surveys, covering a total sea area of 120 km2. The results suggest highly flexible and varied aggregation sizes in finless porpoises. Distance analysis across individuals and aggregations revealed a cohesive tendency among groups, compared to solitaries and in pairs. Therefore, the present VTOL drone surveys both elucidated some social aspects of the study population and confirmed the efficacy of these standardized research protocols involving automated, programmed, and repeatable flight missions.

Marine mammal morphometrics: 3D modeling and estimation validation

Techniques of 3D modeling have earned increasing popularity in scientific studies as they offered unprecedented traits in representing objects. As with all mathematical models, the 3D model will be useful once its accuracy has been validated with direct measurements and the robustness of its predictive capability tested. Although measures of body mass and volume are essential to comprehend the life history of animals, such morphometrics, especially total volume, are challenging to obtain from marine mammals due to their elusive nature, aquatic lifestyle, and large size. In this study, accurate measurements of body volume were directly detected from fresh carcasses of eleven finless porpoises (Neophocaena asiaeorientalis sunameri) and used to validate 3D models recreated from the same animals using Blender 3D graphics. Published models using truncated cones or elliptical shapes, based on 3, 5, 8, or 19 measurements of girths or heights & widths along the body, were also applied to porpoises to verify their accuracy. The Blender-generated 3D model produced the most accurate estimates of body volume compared to conventional truncated models, with a mean error of only 2.5% to the direct volume measurements. When photogrammetric images are available, the model can predict the body volumes based on total length alone. Similar accuracy was possible with the elliptical model using 19 height & width measurements (5% increments in total length). However, significant (p < 0.001) inaccuracy resulted from truncated models with 3, 5, or 8 girth measurements and elliptical models with 3 or 5 height & width measurements, and the accuracy of these models also decreased significantly as the number of measurement sites was reduced. Moreover, Blender 3D models can be extrapolated to animals with images absent, and such predicted volumes were tested to be trustworthy (overall skill = 0.998, r = 0.998, p < 0.01). Therefore, we recommend that researchers use either digital 3D models or elliptical models with 5% increments sectioning the torso to obtain accurate estimates of the body volumes of free-ranging marine mammals.

Variation of blubber thickness of the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) in human care: Adaptation to environmental temperature

Blubber thickness (BT) has a seasonal pattern in most small cetaceans in temperate and polar regions, which may be a crucial adaptive mechanism in response to environmental temperature changes. However, BT and environmental temperature correlations have never been tested experimentally in any cetacean species owing to logistical difficulties in the aquatic environment. The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis, YFP) is one of the smallest cetacean species worldwide, which exclusively inhabits the middle and lower regions of the Yangtze River in China. Here, we investigated BT variation patterns in YFPs and their relationship to environmental temperature changes using ultrasound imaging technology by longitudinally monitoring four YFPs in human care. We found that blubber was not evenly distributed in the skin of YFPs. BT increased along the craniocaudal axis from the head to the umbilical girth, and decreased towards the fluke, with relatively thicker blubber in the dorsal region than in the ventral and lateral regions. Significant negative correlations between BT and seasonal water temperature changes were observed in YFPs. However, different body regions display different sensitivities to seasonal temperature changes. The BT in the anal girth region exhibited noticeable seasonal changes. In contrast, the umbilical lateral and ventral regions showed relatively blunt seasonal changes, indicating different adaptive functions of the blubber in different regions. BT in the dorsal region decreased linearly with increasing water temperature. In the lateral and ventral regions, BT significantly changed with water temperature at a threshold of 18 ​°C. The YFPs had relatively thinner BT than similar-sized harbor porpoises that inhabit relatively high latitudes with much lower water temperatures. This further demonstrates the adaptive function of BT in response to environmental temperatures in small cetaceans. This study elucidates the seasonal pattern of BT variation in small cetaceans and provides insight into adaptation mechanisms of small cetaceans to temperature changes.

Viral Diversity and Epidemiology in Critically Endangered Yangtze Finless Porpoises (Neophocaena asiaeorientalis asiaeorientalis).

The Yangtze finless porpoise (YFP) (Neophocaena asiaeorientalis asiaeorientalis) is a critically endangered freshwater cetacean, with about 1,249 individuals thought to be left in the wild. However, viral entities and viral diseases of YFPs remain obscure. In this study, anal swabs for virome analysis were collected during the physical examination of YFPs in the Tian-E-Zhou Oxbow (TEO) ex situ reserve. A total of 19 eukaryotic viral species belonging to 9 families, including Papillomaviridae, Herpesviridae, Picornaviridae, Picobirnaviridae, Caliciviridae, Retroviridae, Parvoviridae, Virgaviridae, and Narnaviridae, and other unclassified viruses were identified based on metasequencing. Among these detected viruses, a novel herpesvirus (NaHV), two different kobuviruses (NaKV1-2), and six different papillomaviruses (NaPV1 to -6) were considered potential risks to YFPs and confirmed by PCR or reverse transcription-PCR (RT-PCR). Most YFPs sampled were found to harbor one or more kinds of detected viral genomes (52/58 [89.7%]). Surveillance results demonstrated that kobuvirus and herpesvirus displayed obvious age distribution and PVs showed significant gender difference in YFPs. According to species demarcation criteria in individual genera in Papillomaviridae, two novel species (referred to as Omikronpapillomavirus 2 and 3) and four novel isolates of PV were identified in YFPs. Further evolutionary analysis suggested that NaPVs would occupy the mucosal niche and that virus-host codivergence mixed with duplications and host-switching events drives the evolution of cetacean PVs. Divergence times of PVs in YFP and other cetacean reflect the incipient speciation of YFPs. In summary, our findings revealed the potential viral entities, their prevalence, and their evolutionary history in YFPs, which raises an important issue regarding effects of viral infection on the fitness of YFPs. IMPORTANCE The Yangtze finless porpoise (YFP) is the only cetacean species in freshwater following the functional extinction of the baiji (Lipotes vexillifer). Health management, disease treatment, and other special measures are important for maintaining the existing YFP populations, especially in in situ and ex situ reserves. The discovery of potential viral entities and their prevalence in YFPs raises an important issue regarding the effects of viral infection on the fitness of YFPs and may contribute to the conservation of YFPs. The evolutionary history of papillomaviruses in YFP and other cetaceans reflects the phylogeny of their hosts and supports the status of incipient species, opening a window to investigate the evolutionary adaptation of cetaceans to freshwater as well as their phylogeny to remedy the deficiency of fossil evidence.

Novel morphological and molecular data for Nasitrema spp. (Digenea: Brachycladiidae) in the East Asian finless porpoise (Neophocaena asiaeorientalis sunameri)

The East Asian finless porpoise, Neophocaena asiaeorientalis sunameri, ranks among the most endangered species with rapidly decreasing population in the Northwest Pacific. Trematode parasites of the genus Nasitrema that inhabit the air sinuses, inner ear, and the central nervous system of cetaceans frequently cause equilibrium dysfunction, disorientation, interference with echolocation, incoordination, and nervous system degeneration. Due to their specific location and associated pathologies, they have been recognized as one of the causes of cetacean strandings. Stranding data provides crucial information on the species’ biology, population health, and on the status of entire marine ecosystem. However, published data on parasite-induced standings that include information on the causative parasite pathogens are scarce. As part of a wider survey on the causes of East Asian finless porpoise strandings along the west coast of Korea, herein, we provide novel morphological and molecular data on two sympatric species of Nasitrema, namely, Nasitrema spathulatum and Nasitrema sunameri based on newly collected specimens from a stranded alive East Asian finless porpoise at the West coast of Korea. Our study adds a new distribution record for important parasite pathogens in cetaceans and provides the first molecular data for the parasite species recovered, which enabled us to re-evaluate the species relationships within the family Brachycladiidae, a group of important parasite pathogens of marine mammals.

Can the regulation of Golden Inland Waterways meet the needs of navigation, flood control, and ecology? A model-based case study

In recent years, the ecological functions of inland waterways have received much attention. Roughness elements have been used in waterway regulations (WRs) to guard the riverbed and improve physical habitat. However, the response of aquatic organisms to regulations varies widely. It is controversial whether inland waterway regulations can achieve the sustainable function of navigation, flood control and ecological needs.This paper evaluated the influence of WRs on aquatic habitat by using the physical habitat simulation models combining a 2D hydrodynamic model and habitat models. Compared with a reference model with no-engineering, the habitat suitability of zoobenthos, four major species of Chinese carp's spawning ground and the Yangtze finless porpoise at different flow discharges were simulated under different densities of river training structures and types of roughness elements. Results showed that the implementation of the WRs can adjust the distribution of the suitability of aquatic habitats, but does not change the pattern of suitability with discharge. The response of biological habitats to regulation projects varied by species. Regulation can maintain the stable habitat during dry and flood periods, reducing the effect of extreme weather on aquatic organisms. Roughness elements are not suitable for large-scale use in WRs. The “win-win” agreement between economic and ecological issues can be obtained through pre-optimization.

Acoustic Presence of Cetaceans in the Miaodao Archipelago, China.

Once an important cetacean habitat, the Miaodao Archipelago has been altered by human-induced disturbances over several decades. While cetacean diversity is known to have decreased, no recent data on species diversity around Miaodao are known to exist. Capitalizing on the high vocal activity of cetaceans, three passive acoustic surveys, including towed and stationary types, were undertaken to detect the presence of species-specific vocalizations in May 2021, October 2021, and July 2022, as most cetacean sightings occurred during May and August in recent years. The results revealed that the East Asian finless porpoise is the sole cetacean species that can be reliably observed around the archipelago, as no other species were detected. The acoustic data also revealed potentially clumped distributions of finless porpoises with some seasonal variation. While not acoustically detected during any of the surveys, humpback whales, minke whales, and killer whales have been visually sighted in the region. The lack of acoustic detection of these species suggests that they are likely to be temporary visitors to the region, or at least exhibit strong seasonality in their presence within the region. These new data provide the latest snapshot of cetacean presence around the Miaodao Archipelago that can help inform future research and conservation.

Is It Feasible to Preserve a Self-Sustaining Population of Yangtze Finless Porpoise in the Highest Density Section of Yangtze River?

Using the VORTEX v. 10. 5.0.0, population viability analysis (PVA) was performed for Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis) in the highest density section between Hukou and Meilong section (HMS) of the Yangtze River. Baseline model showed that this population was in a relatively vulnerability state; the deterministic growth rate (Det-r) was −0.0230; the stochastic growth rate (Stoch-r) was −0.0385; the probability of extinction (PE) was 0.5690; the mean population size of extant populations (N-extant) was 22; the genetic diversity (GD) was 0.7698. Under the general protection model, the Det-r was 0.0015, and the Stoch-r was −0.0092; Under the medium protection model, the Det-r was 0.0219, and the Stoch-r was 0.0144; Under the optimal protection model, the Det-r was 0.0383, and the Stoch-r was 0.0357. Sensitivity analysis found that adult females breeding rate, sex ratio at birth, and mortality rate of juvenile YFP were sensitive to maintaining population stability. The PVA showed that the conservation of YFP population in HMS depends on: neutralization of all threats affecting YFP population in the HMS; maintenance and, whenever possible, enhancement of the functional connectivity of the waterbody, increasing the food resources of YFP and reducing the risk of injury to YFP caused by human.

The identification of critically endangered Yangtze finless porpoise high-density areas for priority protection

The identification of critically endangered Yangtze finless porpoise high-density areas for priority protection

Trophic transfer of polycyclic aromatic hydrocarbons in marine mammals based on isotopic determination

The tissue distribution (liver, kidney, heart, lung, and muscle), source, and trophic transfer of 15 polycyclic aromatic hydrocarbons (PAHs) were studied on 14 stranded East Asian finless porpoises (Neophocaena asiaeorientalis sunameri), 14 spotted seals (Phoca largha), and 9 stranded minke whales (Balaenoptera acutorostrata) from Yellow Sea and Liaodong Bay. The PAHs levels ranged from below the limit of detection to 459.22 ng g−1 dry weight in the tissues of the three marine mammals, and light molecular weight PAHs were the primary pollutants. Although the PAHs levels were relatively higher in internal organs of the three marine mammals, generally no tissue-specific distribution of the PAHs congeners was found, either for gender-specific distribution of PAHs in the East Asian finless porpoises. However, species specific PAHs concentration distribution were obtained. The PAHs were mainly originated from petroleum and biomass combustion in the East Asian finless porpoises, while those for the spotted seals and minke whales were complex. Trophic level associated biomagnification was found for phenanthrene, fluoranthene, and pyrene in the minke whale. Benzo(b)fluoranthene exhibited a significant biodilution with increasing trophic levels in the spotted seals, but the total concentration of the PAHs showed a significant biomagnification with increasing trophic levels. Trophic level-associated biomagnification of acenaphthene, phenanthrene, anthracene, and ∑PAHs were found in the East Asian finless porpoise, while pyrene exhibited obvious biodilution with increasing trophic levels. Our current study filled knowledge gaps on tissue distribution and trophic transfer of the PAHs in the investigated three marine mammals.

Microplastics in large marine animals stranded in the Republic of Korea

Microplastics (MPs) are found in every ocean and are frequently ingested by marine animals. This study analyzed MPs in the stomachs and intestines of 12 large marine animals comprising one fin whale (Balaenoptera physalus), seven finless porpoises (Neophocaena asiaeorientalis), two loggerhead turtles (Caretta caretta), one Indo-Pacific bottlenose dolphin (Tursiops aduncus), and one common dolphin (Delphinus delphis) that were stranded off the Republic of Korea between 2019 and 2021. MPs were detected with a mean abundance of 3.42 ± 3.2 items/g and were predominantly of transparent-white, fragment-shaped polypropylene smaller than 200 μm. The abundance of MPs found did not correlate with the biological information (maturity, body length) of the finless porpoises and there were no significant differences in the abundance of MPs between the stomachs and intestines. These results cannot accurately assess the impact of MPs on large marine animals, so further studies are necessary to understand how MPs can potentially affect them.

Preliminary study on genetic differences between two species of finless porpoises, genus Neophocaena, with lack of genetic divergence between two subspecies of the narrow-ridged finless porpoise, N. asiaeorientalis: cytochrome b sequence analyses

Using samples from bycaught finless porpoises, cytochrome b sequences were analysed and phylogenetic trees were constructed. The aims were to: (1) determine genetic divergences within the genus Neophocaena; (2) examine interspecific divergences between N. asiaeorientalis and N. phocaenoides; and (3) examine intraspecific divergence between N.a. asiaeorientalis and N.a. sunameri. For this purpose, complete cytochrome b sequences for 12 N.a. sunameri specimens, collected from fishery markets at Pohang in southeastern Korea, were obtained, and these sequences were compared to the corresponding partial (402bp) and complete (1,140bp) sequences of Neophocaena, obtained from GenBank. From a maximum likelihood tree with the partial sequences of the two Neophocaena species, two clades were detected, corresponding to the two species, with average genetic distance of 1.64%, four fixed site differences (1.00%), and a Gst value of 0.64, although we did not examine the specimens from Southeast Asia and contiguous South China Sea. Furthermore, from the complete sequences, we recognised a lack of genetic divergence between the two subspecies of N. asiaeorientalis, with a Gst value of 0.06 and two pairs of identical sequences between them, indicating that our results do not support current subspecies classification. Thus, we newly found that our cytochrome b sequencing results are useful for the examination of interspecific and intraspecific divergences in Neohpocaena, although further genetic analyses with additional specimens of Neophocaena across its distributional range are necessary to confirm the findings in this study.

Ecological impacts of unsustainable sand mining: urgent lessons learned from a critically endangered freshwater cetacean.

Sand mining, which has tripled in the last two decades, is an emerging concern for global biodiversity. However, the paucity of sand mining data worldwide prevents understanding the extent of sand mining impacts and how it affects wildlife populations and ecosystems, which is critical for timely mitigation and conservation actions. Integrating remote sensing and field surveys over 14 years, we investigated mining impacts on the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) in Dongting Lake, China. We found that sand mining presented a consistent, widespread disturbance in Dongting Lake. Porpoises strongly avoided mining sites, especially those of higher mining intensity. The extensive sand mining significantly contracted the porpoise's range and restricted their habitat use in the lake. Water traffic for sand transportation further blocked the species's river-lake movements, affecting the population connectivity. In addition, mining-induced loss of near-shore habitats, a critical foraging and nursery ground for the porpoise, occurred in nearly 70% of the water channels of our study region. Our findings provide the first empirical evidence of the impacts of unregulated sand extractions on species distribution. Our spatio-temporally explicit approach and findings support regulation and conservation, yielding broader implications for sustainable sand mining worldwide.

Accumulation and risk prioritization of psychoactive substances in the critically endangered Yangtze finless porpoise.

Psychoactive substances have been identified as a kind of emerging contaminants in aquatic environment and pose potential adverse effects on aquatic animals. Yangtze finless porpoise, a critically endangered species in China, is also facing the threat of psychoactive substances. In this study, the accumulation characteristics and risk prioritization of psychoactive substances were investigated in Yangtze finless porpoise collected from Poyang Lake (PYL) and Tian-E-Zhou Oxbow (TZO) in Yangtze River basin. The levels of psychoactive substances were detected in the range of below method detection limits (MDLs) to 98.4ng/mL in the serum of Yangtze finless porpoise. Codeine (COD) and methamphetamine were identified as the major substances due to the highest residual levels with a median concentration of 0.72ng/mL and 0.33ng/mL, respectively. The total concentrations of psychoactive substances in the porpoise collected from TZO was significantly higher than those from PYL. Risk analysis based on effect ratio derived from the ratio of steady-state psychoactive substance serum concentration in the porpoise and human therapeutic plasma concentration revealed that COD was the substance with the highest risk among the psychoactive substances detected, followed by lysergic acid diethylamide (LSD), morphine, alprazolam (ALPZ) and lormetazepam. Location-specific risk prioritization of psychoactive substances found that the top 3 substances are LSD, lorazepam (LORZ) and ALPZ in PYL, and COD, LSD and LORZ in TZO. The results disclose the accumulation of psychoactive substances in Yangtze finless porpoise and suggest that the potential adverse effects should be concerned.

Evolution of fish community structure, cause analysis and implications for <i>ex-situ</i> conservation of Yangtze finless porpoise in Tian-e-Zhou Oxbow of Yangtze River

长江天鹅洲故道是长江江豚首个迁地保护区，其中充足而适口的饵料鱼类资源是长江江豚种群健康发展的保障。为此，根据2017年10月-2021年4月对长江天鹅洲故道进行的7次鱼类调查数据，结合禁捕前的历史数据，对其鱼类群落结构演变进行了分析，并针对长江江豚饵料鱼的供应状况对天鹅洲故道内鱼类资源管理提出了建议。调查期间，共采集到鱼类57种，其中，蒙古鲌（Culter mongolicus）、鲢（Hypophthalmichthys molitrix）和鳙（Aristichthys nobilis）等大中型鱼类生物量明显增加，而䱗（Hemiculter leucisculus）和似鳊（Pseudobrama simoni）等小型鱼类生物量呈现下降趋势。鱼类群落优势种逐渐由太湖新银鱼（Neosalanx taihuensis）、短颌鲚（Coilia brachygnathus）和䱗等小型鱼类转变为鳙、蒙古鲌和拟尖头鲌（Culter oxycephaloides）等大中型鱼类，尤其是新近出现的拟尖头鲌种群发展迅速。同时，短颌鲚和䱗等小型鱼类的体重在减小，而鲢、鳙等大中型鱼类规格在持续提高。长江江豚以小型鱼类和大中型鱼类的幼鱼为食，其资源下降将威胁长江江豚种群的维持和发展。为保障天鹅洲故道内长江江豚的食物供应，建议适当地捕捞鲢、鳙、蒙古鲌和拟尖头鲌，减缓鲢、鳙对小型鱼类的食物竞争压力，以及降低蒙古鲌和拟尖头鲌对小型鱼类的捕食压力；同时丰水期加强故道与长江的连通，引入更多长江干流繁殖的小型鱼类资源；并通过建设人工鱼巢以改善故道内䱗等产粘性卵小型鱼类的繁殖条件，增加小型鱼类资源量。;Tian-e-Zhou Oxbow is the first habitats for the ex-situ reserve established for the Yangtze finless porpoise. The rich and abundant forage fish resources are the guarantee for the healthy development of the Yangtze finless porpoise population. Therefore, the change of fish community structure was analyzed with combined of seven fish surveys data in Tian-e-Zhou Oxbow of Yangtze River from October 2017 to April 2021 and historical data before the fishing ban. In view of forage fish of Yangtze finless porpoise, some suggestions were provided for the scientific management of fish resources in Tian-e-Zhou Oxbow. During the investigation, 57 fish species were collected. The biomass of large and medium-sized fish such as Culter mongolicus, silver carp and bighead carp increased significantly while the biomass of small-sized fish such as Hemiculter leucisculus and Pseudobrama Simoni showed a declining trend. The dominant fish species gradually changed from small-sized fish such as Neosalanx taihuensis, Coilia brachygnathus and Hemiculter leucisculus to large and medium-sized fish such as bighead carp, Culter mongolicus and Culter oxycephaloides, in particular, the newly emerged Culter oxycephaloides population developed rapidly. Meanwhile, the body-weight of small-sized fish such as Coilia brachygnathus and Hemiculter leucisculus was decreasing, but the body-weight of large and medium-sized fish was increasing. Because the Yangtze finless porpoise feeds on the small-sized fishes and juveniles of large and medium-sized fishes, the decline of their food resources would threaten the maintenance and growth of the Yangtze finless porpoise population. In order to ensure food supply for the Yangtze finless porpoises in Tian-e-Zhou Oxbow, it suggested that rational capture of silver carp, bighead carp, Culter mongolicus and Culter oxycephaloides should be taken into consideration in order to reduce the food competition pressure of silver carp and bighead carp and the predation pressure of Culter mongolicus and Culter oxycephaloides on small-sized fishes. Besides, another measures to increase the small-sized fish resources like strengthening the connectivity of the oxbow with Yangtze River in the wet season to introduce more small-sized fish resources from Yangtze River and laying artificial fish nests in the oxbow to improve the breeding conditions for the small-sized fish species with adhesive eggs such as sharply should be carried out.

Anthropogenic activity, hydrological regime, and light level jointly influence temporal patterns in biosonar activity of the Yangtze finless porpoise at the junction of the Yangtze River and Poyang Lake, China.

Under increasing anthropogenic pressure, species with a previously contiguous distribution across their ranges have been reduced to small fragmented populations. The critically endangered Yangtze finless porpoise ( Neophocaena asiaeorientalis asiaeorientalis), once commonly observed in the Yangtze River-Poyang Lake junction, is now rarely seen in the river-lake corridor. In this study, static passive acoustic monitoring techniques were used to detect the biosonar activities of the Yangtze finless porpoise in this unique corridor. Generalized linear models were used to examine the correlation between these activities and anthropogenic impacts from the COVID-19 pandemic lockdown and boat navigation, as well as environmental variables, including hydrological conditions and light levels. Over approximately three consecutive years of monitoring (2020-2022), porpoise biosonar was detected during 93% of logged days, indicating the key role of the corridor for finless porpoise conservation. In addition, porpoise clicks were recorded in 3.80% of minutes, while feeding correlated buzzes were detected in 1.23% of minutes, suggesting the potential existence of localized, small-scale migration. Furthermore, both anthropogenic and environmental variables were significantly correlated with the diel, lunar, monthly, seasonal, and annual variations in porpoise biosonar activities. During the pandemic lockdown period, porpoise sonar detection showed a significant increase. Furthermore, a significant negative correlation was identified between the detection of porpoise click trains and buzzes and boat traffic intensity. In addition to water level and flux, daylight and moonlight exhibited significant correlations with porpoise biosonar activities, with markedly higher detections at night and quarter moon periods. Ensuring the spatiotemporal reduction of anthropogenic activities, implementing vessel speed restrictions (e.g., during porpoise migration and feeding), and maintaining local natural hydrological regimes are critical factors for sustaining porpoise population viability.

The bacteria of Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) are site-specific and distinct from freshwater environment.

Bacteria play an essential role in the health of marine mammals, and the bacteria of marine mammals are widely concerned, but less is known about freshwater mammals. In this study, we investigated the bacteria of various body sites of Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) and analyzed their association with freshwater environmental bacteria. The bacterial community and function of Yangtze finless porpoise showed apparent site-specificity. Various body sites have distinct differences in bacteria and have their dominant bacteria. Romboutsia, Plesiomonas, Actinobacillus, Candidatus Arthromitus dominated in the intestine (fecal and rectal samples). Fusobacterium, Streptococcus, and Acinetobacter dominated in the oral. The dominant genera in the blowhole include Suttonella, Psychrobacter, and two uncultured genera. Psychrobacter, Flavobacterium, and Acinetobacter were dominant in the skin. The alpha diversity of intestinal (fecal and rectal) bacteria was the lowest, while that of skin was the highest. The oral and skin bacteria of Yangtze finless porpoise significantly differed between the natural and semi-natural conditions, but no sex difference was observed. A clear boundary was found between the animal and the freshwater environmental bacteria. Even the skin bacteria, which are more affected by the environment, are significantly different from the environmental bacteria and harbor indigenous bacteria. Our results provide a comprehensive preliminary exploration of the bacteria of Yangtze finless porpoise and its association with bacteria in the freshwater environment.

Gapless genome assembly of East Asian finless porpoise

In recent years, conservation efforts have increased for rare and endangered aquatic wildlife, especially cetaceans. However, the East Asian finless porpoise (Neophocaena asiaeorientalis sunameri), which has a wide distribution in China, has received far less attention and protection. As an endangered small cetacean, the lack of a chromosomal-level reference for the East Asian finless porpoise limits our understanding of its population genetics and conservation biology. To address this issue, we combined PacBio HiFi long reads and Hi-C sequencing data to generate a gapless genome of the East Asian finless porpoise that is approximately 2.5 Gb in size over its 21 autosomes and two sex chromosomes (X and Y). A total of 22,814 protein-coding genes were predicted where ~97.31% were functionally annotated. This high-quality genome assembly of East Asian finless porpoise will not only provide new resources for the comparative genomics of cetaceans and conservation biology of threatened species, but also lay a foundation for more speciation, ecology, and evolutionary studies.Measurement(s)Neophocaena asiaeorientalis sunameri • Gapless genome assembly • sequence annotationTechnology Type(s)MGISEQ. 2000 • PacBio HiFi Sequencing • Hi-CSample Characteristic - OrganismNeophocaena asiaeorientalis sunameriSample Characteristic - EnvironmentseawaterSample Characteristic - LocationYellow Sea near Lianyungang City, Jiangsu Province, China