Endangered Yangtze Finless Porpoise Research Articles

Temporal and spatial biosonar activity of the recently established uppermost Yangtze finless porpoise population downstream of the Gezhouba Dam: Correlation with hydropower cascade development, shipping, hydrological regime, and light intensity.

Numerous dams disrupt freshwater animals. The uppermost population of the critically endangered Yangtze finless porpoise has been newly formed below the Gezhouba Dam, however, information regarding the local porpoise is scarce. Passive acoustic monitoring was used to detect the behaviors of porpoises below the Gezhouba Dam. The influence of shipping, pandemic lockdown, hydrological regime, and light intensity on the biosonar activity of dolphins was also examined using Generalized linear models. Over the course of 4 years (2019-2022), approximately 848, 596, and 676 effective monitoring days were investigated at the three sites, from upstream to downstream. Observations revealed significant spatio-temporal biosonar activity. Proportion of days that are porpoise positive were 73%, 54%, and 61%, while porpoise buzz signals accounted for 78.49%, 62.35%, and 81.30% of all porpoise biosonar at the three stations. The biosonar activity of porpoises was much higher at the confluence area, particularly at the MZ site, during the absence of boat traffic, and during the Pandemic shutdown. Temporal trends of monthly, seasonal, and yearly variation were also visible, with the highest number of porpoises biosonar detected in the summer season and in 2020. Significant correlations also exist between the hydrological regime and light intensity and porpoise activity, with much higher detections during nighttime and full moon periods. Hydropower cascade development, establishment of a natural reserve, fish release initiatives, and implementation of fishing restrictions may facilitate the proliferation of the porpoise population downstream of the Gezhouba Dam within the Yichang section of the Yangtze River. Prioritizing restoration designs that match natural flow regimes, optimize boat traffic, and reduce noise pollution is crucial for promoting the conservation of the local porpoises.

Increased Yangtze finless porpoise presence in urban Wuhan waters of the Yangtze River during fishing closures.

Wuhan, a highly urbanized and rapidly growing region within China's Yangtze Economic Zone, has historically been identified as a gap area for the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) based on daytime visual surveys. However, there has been a noticeable increase in porpoise sightings since 2020. This study employed passive acoustic monitoring to investigate porpoise distribution in Wuhan between 2020 and 2022. Generalized linear models were used to explore the relationship between shipping, hydrological patterns, light intensity, and porpoise biosonar activity. Over 603 days of effective monitoring, the daily positive rate for porpoise biosonar detection reached 43%, with feeding-related buzz signals accounting for 55% of all porpoise biosonar signals. However, the proportion of minutes during which porpoise presence was detected was 0.18%, suggesting that while porpoises may frequent the area, their visits were brief and mainly focused on feeding. A significant temporal trend emerged, showing higher porpoise biosonar detection during winter (especially in February) and 2022. Additionally, periods without boat traffic correlated with increased porpoise activity. Hydrological conditions and light levels exhibited significant negative correlations with porpoise activity. Specifically, porpoise sonar detections were notably higher during the night, twilight, and new moon phases. It is highly conceivable that both fishing bans and COVID-19 pandemic-related lockdowns contributed to the heightened presence of porpoises in Wuhan. The rapid development of municipal transportation and shipping in Wuhan and resulting underwater noise pollution have emerged as a significant threat to the local porpoise population. Accordingly, it is imperative for regulatory bodies to effectively address this environmental stressor and formulate targeted protection measures to ensure the conservation of the finless porpoise.

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

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.

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.

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.

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 <1 m within 15 days. The high stranding risk area is 284.54 km2 in the dry scenario, >251.04 km2 in the normal scenario, and >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 Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) movements in the Poyang Lake, China: Implications on flexible management for aquatic animals in fluctuating freshwater ecosystems

Identifying seasonal high-use habitats and migration corridors is the basis for migratory species conservation. Previous studies have focused on Marine Protected Areas, while freshwater ecosystems, often accompanied by severe hydrological fluctuations, suggest new perspectives for flexible management. Poyang Lake is an essential habitat for the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis, YFP), supporting almost half of their natural population. However, studies on the movement patterns and habitat preferences of YFPs still lack there, preventing potential protected areas’ effectiveness. In this study, we conducted 10 surveys for the YFP population in the main body and tributaries of Poyang Lake from October 2018 to August 2020. We used habitat modeling to analyze their seasonal habitat use and the environmental predictors. YFPs showed a seasonal movement pattern consistent with water level fluctuations. They entered the tributaries from the main lake body in low and medium water levels and returned to the main lake during high water level periods. The water depth was the most important environmental variable in each hydrological season that affects YFPs’ habitat selection. The suitable water depth was about 4-8 m during the low water level, 6-12 m during the medium water level, and 7-20 m during the high water level. YFPs’ 50% core habitats distribution showed noticeable seasonal changes. The proportion of their suitable habitats in the whole lake was relatively low, which was highest during high water level (16.89%), and the weakest during low water level (12.11%). Considering the seasonal movements of the YFPs in the lake, we recommend flexible management measures for their core habitats to alleviate human interference and restore their movement rhythm between the river and the lake, which shed light on protected area management for aquatic animals in such seasonal fluctuating habitats.

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.

Comparing fish prey diversity for a critically endangered aquatic mammal in a reserve and the wild using eDNA metabarcoding

Using environmental DNA (eDNA) metabarcoding, we compared fish diversity in two distinct water bodies within the Yangtze River Basin with known populations of the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis; YFP): the Tian-e-Zhou Reserve and Poyang Lake. We aimed to create a fish surveying tool for use in the Yangtze River Basin, while also gaining a better understanding of the prey distribution and diversity within two of the remaining strongholds of YFP. 16S rRNA universal primers were developed to amplify fish eDNA. After high-throughput sequencing and stringent data filtering, we identified a total of 75 fish species (6 orders, 9 families, 57 genera) across seasons and regions. Nine of the 75 fish species were among the 28 known YFP prey species, three of which were detected in all water samples. Our eDNA metabarcoding identified many species that had been previously captured using traditional netting practices, but also numerous species not previously collected in these water bodies. Fish diversity was higher in Poyang Lake than in Tian-e-Zhou Reserve, as well as higher in the spring than in summer. These methods provide a broadly applicable tool to quantify fish diversity and distributions throughout the Yangtze River Basin, and to inform conservation strategies of YFP.

Population survey showing hope for population recovery of the critically endangered Yangtze finless porpoise

The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), has experienced rapid declines in recent decades. We estimate its abundance based on surveys conducted between November and December 2017 in the main-stem of the Yangtze River and adjacent Poyang and Dongting Lakes. We compare these to published abundance estimates from 2006 and 2012, using a bootstrap resampling approach to make inference about population change over the 2006–2017 time period. Encounter rates of porpoise from additional surveys during this period provided another index for evaluating temporal changes in abundance in Poyang and Dongting Lakes. As of December 2017, free-ranging populations of this species are estimated at 1012 (95%CI: 791–1233) individuals of which 445 (95%CI: 295–595) occur in the main stem of the Yangtze River, 457 (95%CI: 329–634) in Poyang Lake, and 110 (95%CI: 65–187) in Dongting Lake. Porpoise numbers in main-stem of the Yangtze River and Dongting Lake declined rapidly from 2006 to 2012 (mean annual rates of −14% and −12%, respectively). These rates of decline greatly eased from 2012 to 2017 (−2.5% and +3% annual growth, respectively). In Poyang Lake, the encounter rates of porpoise have remained relatively stable between 2006 and 2017. This improved population trajectory was likely a joint consequence of government and public conservation efforts. However, fragmentation of porpoise populations in Yangtze River main-stem and significantly reduced migratory movements between the two adjoining lakes and the Yangtze main stem pose a continued threat to the long-term viability of this species. Further actions to improve habitat connectivity are urgently needed.

Hematologic and Biochemical Reference Interval Development and the Effect of Age, Sex, Season, and Location on Hematologic Analyte Concentrations in Critically Endangered Yangtze Finless Porpoise (Neophocaena asiaeorientalis ssp. asiaeorientalis).

In this study, references intervals for 49 clinicopathological parameters were established for the critically endangered Yangtze finless porpoise (YFP) (Neophocaena phocaenoides asiaorientalis). Both from the wild (Poyang Lake) and seminatural (Tian-E-Zhou Oxbow) populations, individual blood samples from 188 animals were collected from 2009 to 2017 and from 2002 to 2015, respectively. For reference interval determination, we used a non-parametric bootstrap-based procedure to determine the 95th percentiles and the associated 90% confidence interval for each analyte. Our results indicated a need to partition the analyte concentrations by sex, age group, or pregnancy; however, we did not find a need to partition results by location. We then used a linear mixed model to determine if evidence existed for mean differences between location with sex and season as covariates and age group as the clustered random variable on mean hematological parameters in the YFP. We found that 88% of the analytes were significantly different between locations. Within the covariates, sex and season showed 31 and 69% significant difference in mean distributions, respectively. Additionally, age group provided a significant source of variation in 25% of the analytes. In summary, our finding suggests that analytes should be grouped according to sex, age, and reproductive status (non-pregnant and non-lactating, pregnant and lactating). Furthermore, we have provided the first set of reference intervals for 49 clinicopathological parameters that could provide guidelines for the initial evaluation of individuals during health assessments.

The impact of fisheries management practices on the survival of the Yangtze finless porpoise in China

Abstract The Critically Endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is facing a significant threat from illegal fishing in Poyang Lake and Dongting Lake, and current fisheries management has proved insufficient to eliminate illegal fishing. A survey of local communities around the two lakes was conducted to investigate fishing activities and their potential impacts. Using a series of six scenarios derived from our data, we suggest that enhanced daytime patrols may have driven fishers to conduct compensatory night‐time fishing when the patrols are absent. Night‐time fishing activities overlap temporally with the main period of Yangtze finless porpoise foraging, so the potential intensification of night‐time fishing with the use of illegal gears could pose an increased threat to porpoises. In addition to increasing law enforcement management efforts, helping fishers to secure alternative livelihoods may provide a more practical and sustainable long‐term method for reducing illegal fishing and its impacts on porpoises. This study also provides important lessons for conservation policy‐making and implementation for other cetacean species threatened by illegal fishing.

Genetic footprint of population fragmentation and contemporary collapse in a freshwater cetacean

Understanding demographic trends and patterns of gene flow in an endangered species is crucial for devising conservation strategies. Here, we examined the extent of population structure and recent evolution of the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis). By analysing genetic variation at the mitochondrial and nuclear microsatellite loci for 148 individuals, we identified three populations along the Yangtze River, each one connected to a group of admixed ancestry. Each population displayed extremely low genetic diversity, consistent with extremely small effective size (≤92 individuals). Habitat degradation and distribution gaps correlated with highly asymmetric gene-flow that was inefficient in maintaining connectivity between populations. Genetic inferences of historical demography revealed that the populations in the Yangtze descended from a small number of founders colonizing the river from the sea during the last Ice Age. The colonization was followed by a rapid population split during the last millennium predating the Chinese Modern Economy Development. However, genetic diversity showed a clear footprint of population contraction over the last 50 years leaving only ~2% of the pre-collapsed size, consistent with the population collapses reported from field studies. This genetic perspective provides background information for devising mitigation strategies to prevent this species from extinction.

Using environmental DNA to assess population-wide spatiotemporal reserve use.

Scientists increasingly rely on protected areas to assist in biodiversity conservation, yet the efficacy of these areas is rarely systematically assessed, often because of underfunding. Still, adaptive management strategies to maximize conservation success often rely on understanding the temporal and spatial dynamism of populations therein. Examination of environmental DNA (eDNA) is a time and cost-effective way to monitor species' distribution, and quantitative polymerase chain reaction (qPCR) provides information on organismal abundance. To date, however, such techniques remain underused for population assessments in protected areas. We determined eDNA concentration of the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) to describe its occurrence, range, and use of the Tian e-Zhou National Nature Reserve in Hubei, China, across seasons and hydrological depths. Despite the observation that total eDNA concentrations were highest in surface waters in summer, finless porpoise eDNA concentrations were significantly higher in deeper waters than in surface waters in summer. During the breeding season (spring), eDNA signals were site specific and restricted to the core area of the reserve. However, postbreeding eDNA concentrations were widespread across the reserve, encompassing sites previously thought to be unfrequented by the species. Our results suggest spatiotemporal idiosyncrasies in site, depth, and seasonal use of the reserve and a propensity for postbreeding population dispersal. With eDNA and qPCR we were able to assess an entire population's use of a protected area. Illuminating nuances in habitat use via eDNA could be valuable to set pragmatic conservation goals for this, and other, species.

Characterization, optimization, and validation of environmental DNA (eDNA) markers to detect an endangered aquatic mammal

Environmental DNA (eDNA) represents a sensitive and efficient method for noninvasively sampling rare or otherwise hard to monitor taxa, potentially making it a powerful tool for conservation management. Still, this novel method can be affected by sampling protocols, abiotic characteristics of the microhabitat, the focal taxa itself, and primer design. Here we designed 12 species-specific primers for the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) inhabiting the middle to lower Yangtze River in China to enable complementary population survey tools for conservation efforts. Representing primer pairs that amplify a range of DNA fragment sizes, we test these primers for sensitivity at amplifying finless porpoise DNA using conventional PCR from serial diluted blood samples, and from eDNA in aquaria and in the wild, including a nature reserve and a negative control site. We further investigated the capacity for these primers to detect finless porpoise DNA signals from water samples over a 30-day period. Our study presents which primers were successful at amplifying finless porpoise DNA from aquaria and in the wild, and further demonstrates no significant amplicon size effects on primer sensitivity or longevity. We summarize the impact primer design may have on eDNA applications in general and suggest future considerations for conservation efforts with the Yangtze finless porpoise.

Parentage-Based Group Composition and Dispersal Pattern Studies of the Yangtze Finless Porpoise Population in Poyang Lake.

Social behaviors are poorly known for the critically endangered Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis). Here, group composition and dispersal patterns of the YFP population living in the Poyang Lake were studied by parentage-based pedigree analyses using 21 microsatellite loci and a 597 bp segment of the mitochondrial DNA control region. In this study, 21 potential mother-offspring pairs and six potential father-offspring pairs (including two potential parents-offspring pairs) were determined, among which 12 natural mother-offspring groups and a maternal group of three generations were found. No genetically-determined fathers were found associated with their offspring. This study also found that maternally related porpoises at the reproductive state tend to group together. This suggest maternal relationship and reproductive state may be factors for grouping in the YFP population. In natural mother-offspring groups, male offspring were all younger than two years old, which suggest male offspring may leave their mothers at approximately two years of age, or at least they were not in tight association with their mothers as they may have been under two years old. However, female offspring can stay longer with their mothers and can reproduce in the natal group.

Yangtze finless porpoises along the main channel of Poyang Lake, China: Implications for conservation

AbstractPoyang Lake is the largest freshwater lake in China and flows into the Yangtze River. It is a traditional habitat for the endangered Yangtze finless porpoise, which has not been well investigated. To reveal the distribution of the porpoise in Poyang Lake, 12 passive acoustic surveys were conducted along 123 km of the main channel of the lake during different seasons (spring transition season, wet season, autumn transition season, and dry season) from 2008 to 2012. We counted the number of phonating porpoises encountered and calculated the detection rate (encountered individuals detected per kilometer). The median porpoise detection rates ranged from 0 to 0.65 individuals per kilometer during the different surveys. The highest median detection rate of 0.50 was detected in the autumn transition season. The seasonal shrinking of the lake during the dry season may cause a concentration of porpoises in the narrow channels and a high incidence of collisions with cargo ships and fishing boats. Conservation actions should be focused on the main channel of the lake during the dry and transition seasons. In addition, the expansion of the existing reserve to include areas with high porpoise detection rates is necessary.

Genetic diversity and population structure of the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) as revealed by mitochondrial and microsatellite DNA.

Ecological surveys have indicated that the population of the critically endangered Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis asiaeorientalis) is becoming increasingly small and fragmented, and will be at high risk of extinction in the near future. Genetic conservation of this population will be an important component of the long-term conservation effort. We used a 597 base pair mitochondrial DNA (mtDNA) control region and 11 microsatellite loci to analyze the genetic diversity and population structure of the YFP. The analysis of both mtDNA and microsatellite loci suggested that the genetic diversity of the YFP will possibly decrease in the future if the population keeps declining at a rapid rate, even though these two types of markers revealed different levels of genetic diversity. In addition, mtDNA revealed strong genetic differentiation between one local population, Xingchang–Shishou (XCSS), and the other five downstream local populations; furthermore, microsatellite DNA unveiled fine but significant genetic differentiation between three of the local populations (not only XCSS but also Poyang Lake (PY) and Tongling (TL)) and the other local populations. With an increasing number of distribution gaps appearing in the Yangtze main steam, the genetic differentiation of local populations will likely intensify in the future. The YFP is becoming a genetically fragmented population. Therefore, we recommend attention should be paid to the genetic conservation of the YFP.