Freshwater Cetacean Research Articles

Charismatic, but not attractive: bringing attention to the conservation of freshwater cetaceans

Charismatic, but not attractive: bringing attention to the conservation of freshwater cetaceans

Spatial distribution, trophic magnification, and risk assessment of per- and polyfluoroalkyl substances in Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis): Risks of emerging alternatives

The Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis) is the only freshwater cetacean found in China. However, per- and polyfluoroalkyl substances (PFASs) risks in YFPs remain unclear. In this study, legacy PFASs, their precursors and alternatives, were determined in YFP muscles (n = 32), liver (n = 29), kidney (n = 24), skin (n = 5), and blubbers (n = 25) collected from Poyang Lake (PL) and Yangtze River (YR) between 2017 and 2023. Perfluorooctane sulfonic acid (PFOS) was the predominant PFAS in all YFP tissues, with a median hepatic concentration of 1700 ng/g wet weight, which is higher than that in other finless porpoises worldwide. PFOS, chlorinated polyfluorinated ether sulfonates (Cl-PFESAs), and perfluoroalkane sulfonamides concentrations in YFP livers from PL were significantly higher than those from YR (p < 0.05); however, the opposite was observed for hexafluoropropylene oxide acids. Biomagnification and trophic magnification factors (BMF and TMF, respectively) of most PFASs in the YFP food web were > 1. Perfluoroheptane sulfonic acid had the highest BMF value (99), followed by 6:2 Cl-PFESA (94) and PFOS (81). The TMFmuscle and TMFliver values of the total PFASs were 3.4 and 6.6, respectively, and were significantly positively correlated with the fluorinated carbon chain length (p < 0.01). In addition, up to 62 % of the hazard quotients for 6:2 Cl-PFESA were > 1, which was higher than that of PFOS (48 %), suggesting a high hepatotoxicity of 6:2 Cl-PFESA to YFPs. Bioaccumulation and biotoxicity of legacy and emerging alternatives in aquatic organisms continue to be a concern, especially for underscoring the vulnerability of the long-lived and endangered species.

Tooth wear and dental pathology in Amazon River dolphins (Inia geoffrensis) and tucuxis (Sotalia fluviatilis)

The investigation of tooth wear and pathology in freshwater dolphins can increase our understanding of their life history, including interactions with the environment and impacts of disease and morbidity. This paper evaluated the occurrence, prevalence and discussed the putative etiology of dental wear and pathology in freshwater dolphins - tucuxi (Sotalia fluviatilis) and the Amazon River dolphin (Inia geoffrensis) - from the central Amazon basin. Teeth of 29 Amazon River dolphins and 14 tucuxis were visually inspected to identify wear facets and the presence of pathology. Dental wear was observed in 55% (n = 16) of the Amazon River dolphin and 79% (n = 11) of the tucuxi specimens. For both species, superficial wear restricted to the tooth crown was more frequent. Calculus deposits were observed in both species, occurring in 14% of tucuxi (n = 2) and 41% of Amazon River dolphin (n = 12) specimens. Caries-like lesions were observed in a third of Amazon River dolphin specimens (n = 10), affecting 10% of the teeth (n = 197). Gross caries was the most commonly caries type observed. Only one tucuxi had caries-like lesions, affecting 1.6% of the teeth (n = 13). While conditions such as tooth wear arise from normal physiological processes, severe wear and pathology such as caries and calculus can contribute to further disease development and morbidity, impacting the health of the animals. Further studies using materials from museum collections in other regions from the Amazon Basin will help elucidate the occurrence, etiology, and health impact of tooth wear and dental pathology in freshwater cetaceans, contributing to our growing understanding of their life history.

Integrated Conservation Strategy for Endangered Small Cetaceans: Insights from the Case of the Yangtze Finless Porpoise

The Yangtze finless porpoise (YFP) is an endemic freshwater cetacean species that exclusively inhabits the middle and lower reaches of the Yangtze River basin. Since the late 1970s, the YFP has experienced a drastic population decline and was classified as critically endangered by the IUCN in 2013. To save this unique species, a range of integrated conservation measures have been implemented, including strengthening natural habitat protection (in-situ), enhancing insurance populations (ex-situ), and advancing captive breeding and research initiatives. These efforts have yielded significant progress in the conservation of the YFP. The natural population has been starting to increase after a sharp decline, and the establishment of three insurance populations has provided a solid foundation for recovery. Additionally, advancement in captive breeding and research has delivered crucial technical support for population conservation. As a flagship species of Yangtze River biodiversity and an indicator of the river’s ecosystem health, the YFP’s integrated conservation strategy not only benefits its own population but also offers valuable insights for the protection of other endangered aquatic species in the Yangtze River and other threatened small cetaceans worldwide.

Vorticity preference of the Yangtze finless porpoise (Neophocaena asiaeorientalis) during the dry season at the Wanhe River Estuary confluence

The Yangtze finless porpoise (Neophocaena asiaeorientalis) is critically endangered. Finless porpoises rely on small fish as their primary food source. Fish distribution is impacted by topography and vorticity (i.e., water flow patterns), which are markedly more complex in river channel confluences than in other aquatic habitats. Thus, the hydrodynamic conditions imposed by confluences may influence habitat selection by fish and the subsequent behavior and predation strategies of porpoises. However, hydrodynamic effects and driving mechanisms for porpoise occurrence, distribution, and feeding strategies remain unclear. Based on survey data and hydrologic measurements, we created a hydrodynamic model to investigate the driving mechanism of porpoise clustering in a confluence of the Wanhe River Estuary, China. We showed a preference for vorticity in the range 0.001 s−1–0.0015 s−1. Our multivariate logarithmic linear model revealed a fit of R2 = 0.792, indicating consistency between theoretical and actual occurrence values. Certain patch parameter effects suggest that vorticity fragmentation affects porpoise habitat selection and utilization. Our study provides a new perspective on the ecological impact of the Yangtze River wading project and the habitat protection of aquatic animals in rivers and aids future research examining hydrodynamic effects on the feeding behavior of freshwater cetaceans.

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.

Virulence factors of Gram-negative bacteria from free-ranging Amazon river dolphins (Inia geoffrensis).

Freshwater cetaceans play a significant role as sentinel animals, providing important data on animal species and aquatic ecosystem health. They also may serve as potential reservoirs of emerging pathogens and host virulence genes in their microbiota. In this study, we evaluated virulence factors produced by Gram-negative bacteria recovered from individuals belonging to two populations of free-ranging Amazon river dolphins (Inia geoffrensis). A total of 132 isolates recovered from the oral cavity, blowhole, genital opening and rectum of 21 river dolphins, 13 from Negro River and 8 from Tapajós River, Brazil, were evaluated for the production of virulence factors, such as biofilms and exoproducts (proteases, hemolysins and siderophores), in planktonic and biofilm forms. In planktonic form, 81.1% (107/132) of the tested bacteria of free-ranging Amazon river dolphins were able to produce virulence factors, with 44/132 (33.4%), 65/132 (49,2%) and 54/132 (40,9%) positive for protease, hemolysin and siderophore production, respectively. Overall, 57/132 (43.2%) of the isolates produced biofilms and, under this form of growth, 66/132 (50%), 88/132 (66.7%) and 80/132 (60.6%) of the isolates were positive for protease, hemolysin and siderophore production. In general, the isolates showed a higher release of exoproducts in biofilm than in planktonic form (P < 0.001). The present findings show that Amazon river dolphins harbor potentially pathogenic bacteria in their microbiota, highlighting the importance of monitoring the micro-organisms from wild animals, as they may emerge as pathogens for humans and other animals.

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.

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.

Blind Indus Dolphin: Its Risk towards Extinction and Protective Measures

The Indus River dolphin, sometimes known as the blind dolphin, is a freshwater cetacean that is exclusively found in Pakistan's Indus River. The IUCN Red List of vulnerable species lists the Indus River dolphin as endangered due to an 80% drop in its distribution range and a habitat that has been badly disrupted by dams and degraded by water diversions. The blind dolphin is a member of one of the oldest families of cetaceans, which separated about 29 million years ago, or roughly 22 million years before the emergence of contemporary dolphins. Its eyes are little and its vision is weak. Typically, indus dolphins are observed either singly or in small groups of two to three dolphins. They can occasionally be found in bigger groups of 20 to 30 people. On the Indus mainstem, there are still five subpopulations of indus dolphins, each of which is divided by irrigation barrages. In Bear River, India, there is a tiny, isolated colony of 18 to 35 Indus River dolphins. The Indus River barrages capture the flowing water and redirect it into a vast network of irrigation canals that emerge from each barrage to meet the demand for water for agriculture. Dolphins from the Indus River frequently travel to irrigation canals using flow regulator gates that are adjusted to the barrages throughout the year. Dolphins become stuck after the canals are shut down for maintenance because of an unexpected water deficit. Since 1992, Sindh Wildlife Department and WWF-Pakistan have collaborated on a dolphin rescue initiative to carefully remove any stranded dolphins from canals and return them to the main river channel. Between 1992 and 2017, 147 dolphins were reported to be caught in canals. Of those, 130 dolphins were successfully recovered and released back into the river, while one dolphin perished in the process. Because they could not be saved. However, little is known regarding the post-release survival rate of the people that were rescued. A dolphin monitoring network has also been established by WWF-Pakistan and Sindh Wildlife Department in conjunction with pertinent stakeholders and neighborhood groups to keep an eye on the Indus River as well as its nearby canals and tributaries and to search for any dolphins that may be stranded there. One of the main risks to Indus dolphins is intensive fishing, which raises the risk of dolphin entanglement in fishing nets and, ultimately, their mortality, especially when they travel near irrigation canals. After the devastating flood of 2010, there was a noticeable rise in illegal fishing between the Guddu and Sukkur barrages. In addition, the altered fishing system in Sindh province significantly increased the number of fishing licenses granted and exacerbated the negative effects of illegal fishing on the Indus River dolphin. In 2011, the Indus River dolphin's death rate peaked with 45 dolphins being reported dead, the majority of which were found while fishing was at its busiest. Since that time, the frequencies of dolphin fatalities have significantly decreased, but they are still not entirely under control. Especially in the Indus Dolphin Game reserve between Guddu and Sukkur Barrages, saving stranded dolphins from the irrigation canals is crucial to maintaining this dolphin population during the low flow season. Standard procedures and tools, such as a soundproof truck, are required for dolphin rescue operations

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.

Seasonal and diel activities of the Yangtze finless porpoise in natural and highly disturbed habitats: Implications for conservation planning of freshwater cetaceans

Abstract Knowledge of fine‐scale seasonal and diel activity patterns of animals provides insights into habitat utilization dynamics and informs conservation action planning against potential human impacts. Such information is particularly important for riverine cetaceans, such as the Yangtze finless porpoise, which is threatened by habitat loss and disturbances by a variety of human activities. Passive acoustic monitoring (PAM) techniques were used to survey the seasonal and diel activities of the Yangtze finless porpoise in two natural habitat patches of the Anqing Yangtze Finless Porpoise Natural Reserve, and in one highly disturbed area adjacent to the reserve. In the two natural habitat patches, significantly higher detection rates of porpoises were observed during autumn and winter. The detection rates during autumn and winter were significantly higher at night than during daytime, whereas during spring and summer the diel difference in porpoise detection rates was not statistically significant. In the highly disturbed habitat, the porpoise detection rates were significantly lower than those in the two natural habitats. Although seasonal differences in porpoise detection rates were not statistically significant, diel detection rates were significantly different in autumn and winter. Information on seasonal patterns of porpoise activities suggested strengthening monitoring and law enforcement during autumn and winter, during the period in which diel activity patterns implied a potential conservation gap during nighttime. Extremely low levels of porpoise activities in port areas implied an ecological impact of coastal engineering on megafauna viability through the alteration of habitat functionality. To provide information on animal occurrences and activities and to minimize the bias of ‘false‐absence’ from visual surveys, the census survey design should consider both visual and PAM techniques. In seasons when occurrences of river cetaceans and habitat use are increasing, heightened conservation monitoring and law enforcement efforts are required, particularly during nighttime.

Identifying the seasonal characteristics of likely habitats for the Yangtze finless porpoise in Poyang Lake

Abstract The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) has experienced significant decline and habitat degradation in recent decades. At present, nearly half of the total population inhabits Poyang Lake. The hydrological seasonality of the lake significantly influences porpoise habitat configuration, which brings problems for conservation in the delineation of reserve design and the management of human activities. A hydrodynamic model was used to distinguish the different hydrological conditions between the flood and dry seasons. The MaxEnt model was used to investigate the major environmental variables affecting porpoise distribution and delineate likely habitats of the porpoise under different hydrological conditions. The effectiveness of the present nature reserve was evaluated based on these results. Flow velocity and distance to fish spawning grounds were the primary variables influencing porpoise distribution during the dry season. Water depth, flow velocity and the distance to bank were the major variables during the flood season. The likely habitats were distributed discontinuously along the main channel during the dry season, with a total area of 112 km2. During the flood season, the habitats extended into the central areas of the lake and tributaries with a total area of 628 km2. At present, the nature reserve covers 4% and 18% of the likely core habitats during dry and flood seasons. An ideal nature reserve should be designed as an integrative network with reference to the seasonality of likely habitat distribution and major environmental variables. The habitats in conditions of extreme low water should be strictly protected in the dry season. Enhanced survey efforts, long‐term hydrodynamic modelling and species distribution modelling can greatly assist in understanding habitat configuration and changing processes for other freshwater cetaceans inhabiting river–lake systems. Future planning to improve protection should consider habitat characteristics under the shifting hydrological conditions caused by climate change or artificial flow alteration.

One Health Implications of Antimicrobial Resistance in Bacteria from Amazon River Dolphins

Studies on the microbiota of freshwater cetaceans are scarce and may provide important data on animal and environmental health. This study aimed to evaluate the antimicrobial susceptibility of Gram-negative bacteria recovered from two populations of free-ranging Amazon river dolphins (Inia geoffrensis). Twenty-one animals were captured and released, 13 from Negro River and 8 from Tapajós River, Brazil. Swab samples were obtained from the oral cavity, blowhole, genital opening and rectum and were cultured on MacConkey agar. Isolates were biochemically identified, and antimicrobial susceptibility was assessed by disk diffusion method. Overall, 132 isolates were recovered, of which 71 were recovered from animals from Negro River and 61 from Tapajós River. The most commonly recovered bacterial species were Enterobacter cloacae, Morganella morganii, Klebsiella pneumoniae and Pseudomonas aeruginosa. Overall, 51.6% (63/122) of the isolates were not-susceptible (intermediate resistance and resistance), of which 28/122 (22.9%) were resistant to at least one antimicrobial. Cephalothin, cefuroxime and cefepime were the drugs to which more resistant and intermediate results were observed (P < 0.001). The results indicate that free-ranging Amazon river dolphins host resistant bacteria, contributing for their maintenance in the environment. This study highlights the importance of the One Health approach to monitor the emergence of antimicrobial resistance. Summary Gram-negative bacteria recovered from 21 free-ranging Amazon river dolphins (Inia geoffrensis) from the Negro River and the Tapajós River populations were evaluated for their antimicrobial susceptibility. Overall, 51.6% (63/122) of the isolates were not-susceptible (intermediate resistance and resistance), of which 28/122 (22.9%) were resistant to at least one antimicrobial. Cephalothin, cefuroxime and cefepime were the drugs to which more resistant and intermediate results were observed. Thus, free-ranging Amazon river dolphins, never treated with antimicrobials, host resistant bacteria, contributing for their maintenance in the environment and highlighting the importance of the One Health approach to monitor the emergence of antimicrobial resistance.

Deteriorating Habitats and Conservation Strategies to Repopulate the Endangered Indus River Dolphin (Platanista gangetica minor); a Lesson Learned From the Conservation Practices of the Yangtze Finless Porpoise (Neophocaena asiaeorientalis)

The Indus River dolphin (IRD;Platanista gangetica minor) is an endangered and blind freshwater cetacean, endemic to the Indus River system of Pakistan and India. This review article provides detailed information about the major challenges IRDs are facing, and their possible consequences on the population dynamics of the IRD. Furthermore, we have suggested future conservation strategies for the IRD based on the lesson learned from the conservation of the Yangtze finless porpoise (YFP;Neophocaena asiaeorientalis), a Critically Endangered freshwater cetacean. The major challenges for IRDs are habitat degradation, habitat fragmentation, and several types of industrial and agricultural pollutants. Worsening climatic changes, illegal fishing, and overfishing are additional threats. The construction of several barrages has fragmented the population into several short segments, some of which are too small for the IRDs to survive. In some segments, the population status of the IRD is unknown. In the remaining populations, genetic inbreeding, water shortage, canal entrapment, and altered ecological environment are potent negative factors for the survival of the IRD. Conservation strategies including fishing bans, translocation, and future research (tagging, periodic health assessments, necropsy and virtopsy, understanding the reproductive biology, and genomics) are possible recommendations. Very serious conservation efforts are needed to save the IRD from decline keeping in view the water shortage, pollution, lack of health assessment studies, and habitat degradation and fragmentation.

Mitigating the effect of shipping on freshwater cetaceans: The case study of the Yangtze finless porpoise

Shipping has increasingly become a major threat to cetaceans due to its direct effect (e.g. ship strikes) and indirect effects (e.g. noise and habitat displacement). Most previous studies have focused on the deleterious effects of shipping traffic on marine species, while the effect of shipping on freshwater cetaceans has received little attention. The Yangtze River is a major trade artery in China, and shipping traffic there caused deaths of the now-extinct Yangtze river dolphin or baiji (Lipotes vexillifer). Here, we examine the distributional overlap of another cetacean species, the critically endangered Yangtze finless porpoise (Neophocoena asiaorientalis asiaorientalis) and cargo ships in a busy section of Yangtze River from Ezhou to Zhenjiang City. We use vessel-based survey data from 2006, 2012, and 2017 to quantify the distribution of porpoise. We use satellite images to quantify the distribution of cargo vessels travelling upstream. Most porpoise were concentrated within 300 m of the river banks. Shipping increased by 65% from 2006 to 2017, and ~ 60% of the upstream vessels was also within 300 m of the banks. This increase in shipping may have caused an observed shift in porpoise distribution away from the banks after 2006. Enhanced enforcement of existing shipping regulations that limit vessels to established shipping lane and set refuges in the side channels could help reduce the distributional overlap of porpoise and ships and aid in porpoise conservation. This could be applied and benefit the cetacean conservation under continued growth of shipping in rivers.

Status, distribution, threats, and conservation of the Ganges River Dolphin Platanista gangetica (Mammalia: Artiodactyla: Cetacea) in Nepal

The Ganges River Dolphin Platanista gangetica has been classified as Endangered in the IUCN Red List of Threatened Species. The IUCN changed its status from ‘Vulnerable’ to ‘Endangered’ in 1996 as the species population was declining in its entire distribution range. It is, however, classified as ‘Critically Endangered’ in Nepal. Historically, the freshwater cetacean has been documented in the Karnali, Koshi, Narayani, and Mahakali basins. With their population and distribution range in decline, the Ganges River Dolphin (GRD) is no longer found in the Mahakali River system, which demarcates and traverses the Western border of India and Nepal. This study examines the status and distribution of the GRD in the river systems of Nepal during the monsoon of 2016. The national dolphin population survey was conducted in the three largest river basins in Nepal—Karnali, Narayani, and Koshi. Each of the three basins represent the extreme upstream limit of the GRD distribution in Ganges River basin. The national population survey included both a boat-based survey and shore-based synchronized counting in each of the three river systems. Fifty-two (Best-High-Low: 52-61-50) dolphins were counted during the entire nationwide survey, conducted in July–August, 2016. Researchers gathered social-data from locals residing alongside the observed basin, giving priority to artisanal fishers and those subsisting to some degree from the rivers known to host the river dolphin. A questionnaire survey of ninety-two residents from riparian villages adjacent to the GRD hotspots sheds light on the local perspectives towards dolphin conservation coupled with an assessment of their socio-economic status; artisanal fishing practices; and their awareness of dolphin conservation. According to the survey, notable threats to dolphin conservation are prey depletion; non-availability of suitable habitat; habitat fragmentation and a low level of awareness. Based on the counting outcomes and social survey, recommendations have been put forward for the conservation of this species.

Non-invasive Fecal Steroid Measurements for Monitoring the Reproductive Status of a Critically Endangered Yangtze Finless Porpoises (Neophocaena asiaeorientalis asiaeorientalis).

Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is a critically endangered freshwater cetacean dwelling in the Yangtze River and its adjoining lakes. Affected mainly by the various anthropogenic activities in this region, its population decreased dramatically in the past two decades. To protect this animal from extinction, captive breeding program is an important way to provide basic knowledge for wild population conservation. Non-invasive fecal steroid radioimmunoassay technique was validated in three captive Yangtze finless porpoises for the first time in this study. The seasonality of one captive male and the reproductive status of two females were investigated by longitudinal monitoring their fecal reproductive steroid hormone metabolites. Pregnancy could be diagnosed by an abrupt increase in fecal progesterone metabolites. In late pregnancy (4 months before birth), a significant decrease of fecal progesterone metabolites was observed, which might be referenced for the expectation of parturition date. Seven estrous cycles were recognized in one breeding season of a non-pregnant female judged by the variation of fecal progesterone metabolite levels. The fecal progesterone metabolite level was proved a reliable and precise indicator for estrus and pregnancy diagnosis.

Fishing for the facts: river dolphin bycatch in a small‐scale freshwater fishery in Bangladesh

AbstractFisheries bycatch is a primary driver of cetacean declines, especially for threatened freshwater cetaceans. However, information on the factors influencing cetacean susceptibility to bycatch in small‐scale fisheries is limited, impeding development of evidence‐based conservation strategies. We conducted 663 interviews with fishers from southern Bangladesh to investigate the influence of net and set characteristics on seasonal bycatch rates of Ganges River dolphins Platanista gangetica gangetica and assess the sustainability of annual mortality levels. Between October 2010–October 2011, 170 bycatch events (and a minimum of 14 mortalities) were reported, 89% of which occurred in gillnets. The probability of bycatch increased as water depth declined, and as net mesh size increased. While the number of recorded bycatch incidents was higher in gillnets, risk of mortality was greater in set bagnets. Our mortality estimate indicates that fisheries‐related bycatch currently exceeds the sustainable limit recommended by the International Whaling Commission by 3.5 times. Numerous regulations have been developed to improve the productivity of commercially important fisheries, and if regulations were effectively enforced, these may also reduce river dolphin bycatch.