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Article

Population Viability Analysis Revealed the Vulnerability of Yangtze Finless Porpoise (Neophocaena asiaeorientalis) in Poyang Lake

by
Bin Wu
1,2,*,
Weiping Wang
3,
Yuehua Wang
2 and
Zhihong Zhang
4,*,†
1
Jiangxi Fisheries Research Institute, Nanchang 330000, China
2
College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
3
Jiangxi Provincial Aquatic Biology Protection and Rescue Center, Nanchang 330000, China
4
Institute of Biological Resources of Jiangxi Academy of Sciences, Nanchang 330096, China
*
Authors to whom correspondence should be addressed.
†
Dr. Zhihong Zhang is the primary corresponding author responsible for coordinating the research and communication.
Diversity 2025, 17(6), 410; https://doi.org/10.3390/d17060410
Submission received: 12 April 2025 / Revised: 31 May 2025 / Accepted: 31 May 2025 / Published: 10 June 2025
(This article belongs to the Special Issue Wetland Biodiversity and Ecosystem Conservation)
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Abstract

:
Poyang Lake in China is the most critical habitat and final refuge for the Yangtze finless porpoise (Neophocaena asiaeorientalis), YFP. In 2022, its population reached approximately 492 individuals, an increase of 35 from the 457 individuals recorded in 2017, showing a steady upward trend. The infrequent movement of YFPs between Poyang Lake and the Yangtze River represents a considerable threat to the long-term viability of this population. Additionally, serious water shortages in the lake during the dry season have led the government to consider the establishment of a hydraulic project. Therefore, a reliable risk assessment and quantitative analysis of conservation scenarios are urgently needed for this population. Population viability analysis of the YFP population in Poyang Lake was conducted using the VORTEX software. The baseline model predicted a probability of extinction of 0.241 over the next 100 years, with no probability of extinction in the first 30 years; the genetic diversity would be on a continuous downward trend and decline by 91.5%. The comprehensive protection model predicted a probability of extinction of 0.0028 and that the genetic diversity would be maintained at about 0.996 in 100 years. Breeding rate, sex ratio at birth, mortality rate, and gene flow were the factors that were sensitive to maintaining population viability. The results showed that the population of YFPs in Poyang Lake was at a high risk of extinction due to the decline in genetic diversity and the higher mortality and lower birth rate caused by habitat degradation. A total ban on productive fishing and the rescue and interchange of YFPs are conducive to enhancing the viability of the YFP population in Poyang Lake.

1. Introduction

The extinction risk of a population is caused by deterministic and stochastic factors [1]. Certain small populations, particularly of endangered species, are vulnerable to inbreeding and loss of genetic diversity [2,3,4,5]. Population viability analysis (PVA) can enable the prediction of the dynamics of population size and extinction probability [6,7]. PVA can help identify the factors that contribute to the loss in viability, thus allowing appropriate conservation and management measures to be selected and implemented [8].
Yangtze finless porpoise (Neophocaena asiaeorientalis), YFP, is a relatively small, freshwater, toothed cetacean that occurs only in the middle and lower reaches of the Yangtze River and its adjoining lakes (Poyang and Dongting lakes) [9,10,11]. The maximum weight of the YFP is 78.5 kg, with an average of 39.1 kg. The maximum body length is 1.77 m, and the average is 1.30 m [11]. The species is genetically isolated from other porpoise populations and reveals the genomic signatures of adaptation to its freshwater environment [10]. The YFP has been upgraded to the Grade-1 National Key Protected Animals, and Poyang Lake is the “last refuge” for YFPs. As a generalist apex predator, the YFP consumes semi-migratory and non-migratory fish prey [12]. Its population size is considered to be in decline across its entire range due to habitat degradation, with only about 1000 individuals extant and critically endangered. However, the results of the 2022 scientific expedition show that the population of Yangtze finless porpoises has reached 1249, an increase of 237 compared to 2017 [13]. In Poyang Lake, the population size of porpoises remained relatively stable between 2005 and 2007 (484), 2012 (450), 2017 (457), and 2022 (492) [13,14]. 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 [15]. In Poyang Lake, the stranding risk of the critically endangered YFPs is high due to the significant differences in hydrological and landscape conditions between the flood and dry seasons [16].
In contrast to its previous endangered status and compared with other endangered species in the Yangtze River Basin, such as the extinct Chinese paddlefish and the functionally extinct Yangtze river dolphin, the Yangtze finless porpoise (YFP) has been regarded as the “most successfully conserved natural population” with more remarkable conservation achievements. Although the YFP population in Poyang Lake represents the most successful case of natural population protection, numerous threats still persist at the population level. In recent years, the water level in Poyang Lake has been relatively low; the low water period is ahead of schedule, the water level recedes after the flood, and so on. At the same time, the construction of sluice gates in Poyang Lake has become an issue of concern. Therefore, it is of great theoretical and practical significance to study the dynamic characteristics of the Yangtze finless porpoise population in Poyang Lake using a population viability analysis. Here, we used a VORTEX model to simulate the Poyang Lake YFP population dynamics over the next 100 years to determine the key factors affecting its survival through sensitivity analysis. The process we used can serve as an example for developing a framework of conservation priorities at the population level.

2. Materials and Methods

2.1. Study Area

Poyang Lake is located in the northern part of Jiangxi Province and the southern coast of the Yangtze Plain. Its geographical coordinates are between 28°22′–29°45′ N and 115°47′–116°45′ E. The water in the lake is collected from the Gan River, Xiushui, Raohe, Xin River, Fu River and flows northward through Hukou into the Yangtze River. The main lake area of Poyang Lake is generally gourd-shaped, bounded by Songmenshan island, and divided into north and south parts. The northern section comprises the river channel, with a narrow surface and deep water, and the main southern lake has a wide surface and shallow water. The north–south span is more than 170 km, the east–west width is 74 km, and the average width is 16.9 km. Lake Poyang is the largest freshwater lake in China and one of the two remaining lakes that is freely connected with the Yangtze River in the middle reaches of the Yangtze River (Figure 1). Poyang Lake is a “through-flow type” and seasonal freshwater lake whose water level, area, and volume can vary significantly with seasons and years. Factors such as different measurement times, measurement methods, and the scope of the study area may also lead to differences in data on average water depth. Currently, when the water level of Poyang Lake is 21 m (Wusong Datum), the north–south length is 170 km, the maximum east–west width is 74 km, the minimum is 3 km, and the average width is 20.4 km; the maximum water depth is 23.7 m, and the average water depth is 5.1 m; the water surface area is 3960 square kilometers, and the volume is 26 billion cubic meters [17,18]. Natural waters are mainly distributed in the eastern and the northern parts of the lake. Wet meadows are widely scattered in Nanji Town, and the beaches on both sides of river channels lead to Poyang Lake, taking up the largest area among other types of wetlands during low flow periods [17]. Based on the remote sensing image data over the past 20 years (2002–2019), the analysis showed that the overall water area of Poyang Lake presented a decreasing trend and distinct seasonal variations. The monthly change in water area was evident across the whole year, with the largest average area of 3509 km2 in July and the smallest average area of 1434 km2 in January [18]. YFPs mainly inhabit waters with a depth of 2 to 9 m. When the water depth exceeds 3 m, the number of YFP decreases exponentially. They prefer relatively slow flow velocities, generally ranging from 0.3 to 1.2 m per second [11,12].

2.2. VORTEX Simulation Model

VORTEX 10.50 software was used to model the viability of YFP populations in Poyang Lake. VORTEX is an individual-based model that is most appropriate for analyzing extinction dynamics in small populations [19]. The software is developed and recommended by the Conservation Breeding Specialist Group (IUCN/SSC/CBSG), and its owner is the Species Conservation Toolkit Initiative (SCTI) project under the Species360 organization. A VORTEX baseline model was based on three main sources of data: (i) the third Yangtze Freshwater Dolphin Expedition in waters of the Yangtze River, Dongting, and Poyang Lakes, conducted between November and December 2017 [20]; (ii) four capture/release surveys in Poyang Lake conducted in the spring of 2009, 2010, 2011, and 2015, during which all captured individuals were marked with an internal ID and genetic samples were obtained [21]; and (iii) published literature and personal observations.
The YFP population in Poyang Lake was modeled for 100 years so that long-term population trends could be evaluated. The generation length of YFPs was estimated to be 8–9 years [22,23], and the 100-year simulation covered approximately 12 generations. Instead of 1000 replicate simulations that are usually used, we used 10,000 replicate simulations [24]. Extinction was defined as the total removal of at least one sex [25]. The impact of inbreeding was modeled as 3.14 lethal equivalents [26], with 50% of the effect of inbreeding ascribed to recessive lethal alleles.

2.3. Reproductive System and Rates

Polygyny has been shown to be the mating system of YFPs [27]. The mature age of females is 4–6 years, and that of males is 4.5–7 years [27]. However, the female YFPs in Poyang Lake may be able to reproduce at the age of 4 years. The species may still be able to reproduce at the age of 18–19 years [28]. Thus, in this modeling, the first reproductive age of females was 4 years, and that of males was 5 years. The maximum age of reproduction for both male and female YFPs was set as 18 years. Female YFPs do not give birth to more than one young per litter [29]; therefore, the maximum litter size of progeny was set to a value of 1. The birth ratio of YFPs was 1:1 in the Yangtze River Tian-e-zhou ancient channel [29], and the sex ratio from the age of 0 to 1 was 1.1 in Poyang Lake (female to male was 11:10) [28]; therefore, the sex ratio at birth was considered to be 50% female and 50% male.
Assuming that pregnancy and lactation did not overlap, a reproductive cycle that includes both pregnancy and lactation lasted for approximately 18 months. However, taking into account the interval between reproductive activities, it was set to approximately 2 years [30]. In addition, some females may lose their offspring during lactation or due to stillbirths or neonatal deaths and come into estrus sooner afterward, therefore reducing the inter-birth interval. It was assumed that 50% of adult females were breeding annually in the baseline scenario. In other scenarios, the upper and lower limits were 30% to 70%, respectively. An average of 70% of the adult males were capable of reproducing each year. An EV of 10% was used in the simulation. Density-dependent reproduction was not included in the baseline model.

2.4. Mortality Rates

The mortality rate of YFPs in the Yangtze River is possibly 20% for the 0–1 age group, 20% for the 1–2 age group, and 15% for the other age groups [22]. YFP 0–1, 1–2, 2–3, 3–4, 4–5, and >5 age groups mortality was 13.66, 12.37, 11.47, 10.92, 10.68, and 13.15, respectively, in the Tian-e-zhou semi-natural ex situ reserve [29]. However, the mortality rate of the YFPs at the age of 0–2 was estimated at 30.8% [31]. Mei et al. (2012) calculated that the mortality rate of YFPs at the age of 0–1 was 22.4–27.7% [32]. For this modeling, the YFP 0–1, 1–2, and other age groups’ mortality was 25%, 20%, and 10%, respectively. Mortality rates for all age classes were considered to be equivalent between males and females. Standard deviations were set to 5% of the mean values for 0–2 age groups and 3% of the mean values for other age groups, which seemed to provide an appropriate interval.

2.5. Population Description

There was a historical large-scale movement of porpoises between Poyang Lake and the main stem of the Yangtze River [33,34]. However, following the construction of two bridges at the mouth of Poyang Lake in 2000 and 2008, this appeared to be no longer the case [35,36]. 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 [37]. In the baseline model, only one population was considered, with no immigration or emigration of individuals. A total of 457 individuals of the initial YFP population size estimated by Huang et al. (2020) were used in the model [20]. We set 2017 as the starting year for evaluating population viability. The 2022 data can be used to verify which simulation scenario is closer to the real population dynamics. The environmental capacity of YFPs in the Yangtze River was 5000 [22]. Hao et al. (2006) and Li (2017) estimated the environmental capacity to be 50–100 YFP individuals in the Yangtze River Tian-e-zhou ancient channel, whose total area was about 20 km2 [27,29]. The prediction results of the PVA model were credible when the maximum amount ever distributed in history was considered as the environmental capacity [7]. To be conservative, we set the environmental capacity to 1250 individuals in Poyang Lake.
The YFP population in Poyang Lake was seriously threatened by extreme weather, low water levels, water pollution, and sand-dredged shipping, which altered and destroyed the animal’s habitat. It is reported that the extreme low temperatures in 2008 affected the reproductive rate and survival rate of YFPs in the Tian-e-Zhou nature reserve by 71.43% and 82.86%, respectively. The combined effect of multiple adverse factors can be expected to be greater; therefore, for this modeling, catastrophes were included with an annual probability of 1.75%, causing a 50% decrease in survival and reproduction [4]. A compilation of all parameters used in the baseline model is presented in Table 1. A sensitivity analysis was performed to evaluate the effect of reproductive parameters, mortality initial population size, catastrophes, and carrying capacity parameters on the stochastic growth rate (Stoch-r) of the YFP population in Poyang Lake.

2.6. Sensitivity Analysis and Conservation Scenario

Sensitivity analysis was used to elucidate the effects of environmental parameters on the viability of the population over the next 100 years. Fourteen alternative scenarios were created (Table 2), and the levels in each scenario were selected appropriately. The deterministic growth rate (Det-r), stochastic annual population growth rate (Stoch-r), and YFP population size change (%) of each scenario were compared to the corresponding value of the basic scenario.
The baseline model was used to analyze different scenarios and conservation challenges faced by the YFP in Poyang Lake and surrounding habitat fragments. The scenarios modeled included (i) the impact of gene flow and (ii) the effect of the establishment of protection measures. To simulate the interchange of YFPs, annual capture and supplement of an equal number of 2–3 aged individuals with a sex ratio of 1:1 were set, and different numbers of interchange of YFPs (2, 4, 8, 16, and 32 individuals) were used to represent gene flow at different scales. Meanwhile, to reduce the direct impact of capture and replenishment, such interchange of YFPs was modeled to take place only when the population was larger than 50 individuals.
Based on the above simulation analysis, it was found that the most realistic choice for YFP protection in Poyang Lake was to adopt a comprehensive protection scenario; that is, the main sensitive and rigid factors were all improved marginally but effectively compared with the baseline scenario. The establishment of protection measures was tested, and the impact of increased gene flow (interchange of YFPs was set as 16 male individuals aged 2–3 years), increased breeding rate (increased to 55%), reduced mortality rate (the mortality of 0–1 age, 1–2 age, and other age groups females was reduced to 22.5%, 18%, and 9%), and reduction of the impact of natural catastrophes (reduced to 55%) on the viability of the YFP populations was analyzed.

3. Results

3.1. Population Trend of YFPs in Poyang Lake

The baseline model resulted in a deterministic growth rate of −0.0230 (λ = 0.9773) over 100 years, representing a potential annual decline of 2.3%. Generation time was estimated to be approximately 9 years for both sexes. The ratio of adult males to adult females was 0.878. Stoch-r, PE (probability of extinction), and N-extant (number of extant individuals) were −0.0338, 0.2414, and 50 YFPs, with 86% of genetic diversity remaining (Figure 2). However, in the complete absence of catastrophes and threats, Stoch-r, PE, and N-extant of this population were −0.0072, 0.0004, and 278 YFPs, respectively, with 96% of genetic diversity remaining.

3.2. Sensitivity Analysis and Conservation Scenario

Sensitivity analysis indicated that the breeding rate, the sex ratio at birth, and mortality rate were the parameters that had the strongest influence on the dynamics of YFP populations, as shown in Table 2. Further, the increase in mortality in females had an impact on population stability, and compared with young individuals, the increase in mortality in sexually mature females had a greater impact on population stability, as shown in Figure 3.
The results of gene flow simulation at different scales showed that the population viability was not affected when the size of individuals exchanged was less than 8 individuals. However, when more than 16 individuals were exchanged, the rate of population decline began to slow down, as shown in Table 3 and Figure 4. In a comprehensive protection scenario, the probability of extinction was 0.0028, the genetic diversity was maintained at approximately 0.996, and the population size increased relatively steadily by 13.3% in 100 years.

4. Discussion

4.1. Vulnerability of YFPs in Poyang Lake

Direct and indirect evidence of significantly reduced movements between Poyang and Dongting Lakes and the Yangtze main stem indicated the fragmented distribution of porpoises between these three water bodies [33,34,35,36,38,39,40]. Although the Poyang Lake population remained relatively stable from 2006 to 2017, the fragmentation of porpoise populations in the Yangtze River main stem and significantly reduced migratory movements between Poyang Lake and the Yangtze main stem pose a continuous threat to the long-term viability of this species [20]. In the present paper, the baseline model resulted in a potential annual growth rate of the YFP population in Poyang Lake of −2.3%, which is higher than the value of −3.5% estimated using life table modeling [41]. Nevertheless, this growth rate provided evidence that the YFP population in Poyang Lake would still decline even in the absence of additional catastrophes and threats.
Franklin (1980) proposed the 50/500 rule, which is still useful in conservation biology [42] as long as it is used as a guiding principle to indicate when genetic concerns are likely to have an important role in the short- and long-term viability of populations [43]. The population size of the YFP population in Poyang Lake has been lower than 500 individuals in recent years [20,44], indicating some genetic vulnerability in the population in Poyang Lake. As evidenced by the VORTEX model simulations, the probability of extinction was 24.14%, and 14% of genetic diversity was lost at the end of 100 years. The loss of genetic diversity was, in part, due to the relatively small population size and due to the selection of a closed population. Recent genetic analyses suggested a highly asymmetric gene flow between YFP populations in Poyang Lake and the Yangtze River [40].

4.2. Conservation Implications for YFPs in Poyang Lake

The potential conservation scenario in this study examined a case in which gene flow, breeding rate, the mortality rate of young females, and the impacts of natural catastrophes were improved. Flow velocity and distance to fish spawning grounds were the primary variables influencing porpoise distribution during the dry season [15]. 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 [45]. These findings suggest management actions that would have the same effect, such as improving habitat quality in Poyang Lake through the establishment of feed supplements during the dry season, without making YFPs vulnerable to disaster mortality. The findings of this case study of YFPs in Poyang Lake highlight that many species-specific considerations need to be made when selecting gene flow as a conservation strategy. At the metapopulation level, habitat restoration and expansion are critical issues for facilitating dispersal to promote the interchange of YFPs between the Poyang Lake and Yangtze River mainstream YFP populations. Further, the establishment of a hydraulic project may not substantially benefit the porpoise, as it will block the only natural migration channel between Poyang Lake and the Yangtze River [46]. For neutralizing the genetic communication barriers, the interchange of YFPs is an alternative measure to maintain a viable YFPs population in Poyang Lake. Conservation actions for the YFP can be implemented through exchanges among the natural populations in Poyang Lake, Dongting Lake, and the mainstream of the Yangtze River. Additionally, coordinated conservation efforts can be established between the Poyang Lake YFP population and the four ex situ conservation areas, namely, Hubei Shishou Yangtze Tianezhou Dolphin National Nature Reserve, Anhui Tongling Freshwater Dolphin National Nature Reserve, Hubei Jianli Hewangmiao/Hunan Huarong Jichengwan Yangtze Finless Porpoise Provincial Nature Reserve, and Anhui Anqing Xijiang Yangtze Finless Porpoise Municipal Nature Reserve. The VORTEX model provided evidence that the Yangtze finless porpoise (YFP) population in Poyang Lake is vulnerable. The probability of its extinction is significantly influenced by extreme environmental fluctuations, which can sharply reduce the population size either over a short-term or long-term period. In November 2022, the Jiangxi Provincial Department of Agriculture and Rural Affairs orchestrated the relocation of 111 YFP individuals from the southern sand pit of Songmen Mountain. This group comprised 66 male porpoises, 45 female porpoises, 11 mother/calf pairs, 8 females confirmed pregnant via B-ultrasound, and 7 suspected to be pregnant. Given that the Poyang Lake YFP population was approximately 492 in 2022, the severe drought that year placed over one-fifth of the local YFP population in extreme peril. The drought exacerbated risks such as food scarcity and heightened stranding incidents. Consequently, the principle of “protecting water resources equates to safeguarding the YFP in Poyang Lake” has emerged as a national consensus. In the potential conservation scenario, the declining trend of the YFP population in Poyang Lake was changed to a stable and increasing trend. We suggest that the analysis and improvement of sensitivity parameters closely related to environmental conditions and the formulation of a complete set of protection schemes may be the most important insights based on the population viability analysis of the YFP population in Poyang Lake.
There is a strong coupling relationship between the YFP and the fish community in Poyang Lake. The fishing yield and the population of the YFP showed a relatively high tendency of coincidence; that is, both of them first decreased, then increased, and have been stable and increasing since 2012. The areas with a high probability of YFP occurrence overlapped with the areas with a high fish diversity index and catch per unit of effort. It is suggested that the YFP has a certain indicator function to fish diversity and fish density, and higher fish diversity and density can ensure the nutrient balance and improve the feeding efficiency of the YFP. It is important to note that the declining trend of fish diversity in Poyang Lake and its estuaries has not changed. The aggressive predatory fish were recovering rapidly, while the survival of small fish was under great pressure. Seasonal and regional food shortages might be one of the limiting factors to the recovery of the YFP population in Poyang Lake. However, the population of Coilia nasus in Poyang Lake was in an undeveloped state, and the population recovery trend was obvious. This was good for increasing the source of food for YFPs in Poyang Lake [47,48]. It should be noted in particular that the presence of ships was found to significantly alter the behavior patterns of YFPs. Specifically, the proportion of foraging behavior decreased from 48% to 33%, while the proportion of travel behavior increased from 32% to 43%. The distance between vessels and YFPs emerged as a critical factor influencing their behavioral responses. When vessels were positioned more than 300 m away, YFPs exhibited a neutral response in 95% of the observed cases, with no discernible escape behavior. Conversely, as the distance closed to within 300 m, the frequency of escape reactions among YFPs increased progressively, reaching approximately 30% when vessels were within 100 m. In contrast, vessel type and cluster size of YFPs had only minor and statistically non-significant effects on their behavioral responses [49]. These findings clearly demonstrate that the presence and proximity of vessels pose a substantial threat to the normal activities of YFPs. To safeguard the survival and well-being of this critically endangered species, it is imperative to implement strict regulations on navigation routes. In particular, maritime traffic should be restricted from traversing nearshore areas where YFPs are densely concentrated, thereby optimizing conservation efforts and enhancing the protection efficiency for YFPs.

Author Contributions

Conceptualization, B.W.; methodology, B.W. and Y.W.; software, B.W. and Y.W.; validation, B.W. and Z.Z.; formal analysis, B.W. and Y.W.; investigation, W.W. and B.W.; resources, Z.Z. and B.W.; data curation, B.W. and W.W.; writing-original draft preparation, B.W.; writing-review and editing, B.W. and Z.Z.; visualization, W.W. and B.W.; supervision, B.W. and Z.Z.; project administration, Z.Z. and B.W.; funding acquisition, Z.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Global Environment Facility (GEF) pilot project on wetland reserve system in Jiangxi province, grant number GCP/CPR/052/GEF.

Institutional Review Board Statement

This study is a model-based theoretical research, and ethical review and approval are not required.

Data Availability Statement

All data information of this study is included in the article.

Acknowledgments

We would like to express our gratitude to the relevant leaders and teachers from the Jiangxi Fisheries Research Institute, College of Life Sciences at Nanjing Normal University, Institute of Biological Resources of Jiangxi Academy of Sciences, and Jiangxi Provincial Aquatic Biology Protection and Rescue Center for their selfless assistance and meticulous guidance.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Schematic Diagram of the Location and Water System of Poyang Lake Area.
Figure 1. Schematic Diagram of the Location and Water System of Poyang Lake Area.
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Figure 2. Population viability dynamics of YFPs in Poyang Lake ((a) Survival probability; (b) Extinction time-frequency; (c) Genetic diversity; (d) Population size).
Figure 2. Population viability dynamics of YFPs in Poyang Lake ((a) Survival probability; (b) Extinction time-frequency; (c) Genetic diversity; (d) Population size).
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Figure 3. Population size dynamics of YFPs in Poyang Lake in different mortality rates scenarios ((a) Male groups of different ages; (b) Female groups of different ages; (c) Gender differences in the sexually mature group; (d) Gender differences in 2 to 3 age groups).
Figure 3. Population size dynamics of YFPs in Poyang Lake in different mortality rates scenarios ((a) Male groups of different ages; (b) Female groups of different ages; (c) Gender differences in the sexually mature group; (d) Gender differences in 2 to 3 age groups).
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Figure 4. Population viability dynamics of YFPs in Poyang Lake in different interchanges of YFP scenarios ((a) Survival probability; (b) Extinction time-frequency; (c) Population size; (d) Genetic diversity).
Figure 4. Population viability dynamics of YFPs in Poyang Lake in different interchanges of YFP scenarios ((a) Survival probability; (b) Extinction time-frequency; (c) Population size; (d) Genetic diversity).
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Table 1. Summary of parameter input values used in the VORTEX baseline model for YFP populations in Poyang Lake.
Table 1. Summary of parameter input values used in the VORTEX baseline model for YFP populations in Poyang Lake.
ParameterBaseline Value
Number of populations1
Initial population size (N)457
Carrying capacity (K)1250
Inbreeding depression3.14 LE
% of the effect of inbreeding due to recessive lethal alleles50
Breeding systemPolygynous
Age of first reproduction by males/females5/4 years
Maximum reproductive age18 years
Annual % of adult females breeding (SD)50% (10%)
Density-dependent reproduction?No
Maximum litter size1
Overall offspring sex ratio50:50
Adult males in the breeding pool (%)70
Mortality rates:
% mortality from age 0–1 (SD)25 (5)
% mortality from age 1–2 (SD)20 (5)
% mortality from other ages (SD)10 (3)
Catastrophe1.75%; 50%, 50%
16.7%; 95%, 95%
HarvestNone
SupplementationNone
Table 2. The deterministic growth rate (Det-r), stochastic annual population growth rate (Stoch-r), and YFP population size change (%) in 100 years under different scenarios.
Table 2. The deterministic growth rate (Det-r), stochastic annual population growth rate (Stoch-r), and YFP population size change (%) in 100 years under different scenarios.
ProjectsDet-rStoch-rDecrease
Model 1 (baseline scenario)−0.023−0.033891.5%
Model 2 (Model 1 + maximum reproductive age 16 years)−0.0305−0.043696.6%
Model 3 (Model 1 + maximum reproductive age 20 years)−0.0177−0.027485.0%
Model 4 (Model 1 + breeding rate 30%)−0.0758−0.0846100.0%
Model 5 (Model 1 + breeding rate 70%)0.01490.0082−70.2%
Model 6 (Model 1 + mortality rate of 0–1 age 30%, 1–2 age group 25%)−0.0373−0.049598.4%
Model 7 (Model 1 + mortality rate of 0–1 age 20%, 1–2 age group 15%)−0.0092−0.018464.2%
Model 8 (Model 1 + initial population size 329 individuals)−0.023−0.035292.40%
Model 9 (Model 1 + initial population size 634 individuals)−0.023−0.032590.92%
Model 10 (Model 1 +sex ratio at birth, male, 60%)−0.0467−0.058099.5%
Model 11 (Model 1 + sex ratio at birth, male, 40%)−0.0028−0.011136.8%
Model 12 (Model 1 + carrying capacity, 625 individuals)−0.023−0.03491.8%
Model 13 (Model 1 + carrying capacity, 2500 individuals)−0.023−0.03491.5%
Model 14 (Model 1 + effects of natural catastrophes, 0.25)−0.0279−0.045194.7%
Model 15 (Model 1 + effects of man-made catastrophes, 0.90)−0.0323−0.045197.1%
Table 3. The deterministic growth rate (Det-r), stochastic annual population growth rate (Stoch-r), and YFP population size change (%) in 100 years under different interchange scenarios.
Table 3. The deterministic growth rate (Det-r), stochastic annual population growth rate (Stoch-r), and YFP population size change (%) in 100 years under different interchange scenarios.
ProjectsDet-rStoch-rDecrease
Model 1
(baseline scenario, no interchange)		−0.023−0.033891.5%
Model 2
(Model 1 + 16 individuals interchange + age 2–3 years + sex ratio 1:1)		−0.023−0.012565.0%
Model 3
(Model 2 + all male)		−0.023−0.013468.2%
Model 4
(Model 2 + all female)		−0.023−0.004935.5%
Model 5
(Model 3 + age after 5 years)		−0.023−0.033089.8%
Model 6
(Model 4 + age after 4 years)		−0.023−0.016955.3%
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Wu, B.; Wang, W.; Wang, Y.; Zhang, Z. Population Viability Analysis Revealed the Vulnerability of Yangtze Finless Porpoise (Neophocaena asiaeorientalis) in Poyang Lake. Diversity 2025, 17, 410. https://doi.org/10.3390/d17060410

AMA Style

Wu B, Wang W, Wang Y, Zhang Z. Population Viability Analysis Revealed the Vulnerability of Yangtze Finless Porpoise (Neophocaena asiaeorientalis) in Poyang Lake. Diversity. 2025; 17(6):410. https://doi.org/10.3390/d17060410

Chicago/Turabian Style

Wu, Bin, Weiping Wang, Yuehua Wang, and Zhihong Zhang. 2025. "Population Viability Analysis Revealed the Vulnerability of Yangtze Finless Porpoise (Neophocaena asiaeorientalis) in Poyang Lake" Diversity 17, no. 6: 410. https://doi.org/10.3390/d17060410

APA Style

Wu, B., Wang, W., Wang, Y., & Zhang, Z. (2025). Population Viability Analysis Revealed the Vulnerability of Yangtze Finless Porpoise (Neophocaena asiaeorientalis) in Poyang Lake. Diversity, 17(6), 410. https://doi.org/10.3390/d17060410

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