Mitochondrial DNA variation, effective female population size and population history of the endangered Chinese sturgeon, Acipenser sinensis

The anadromous Chinese sturgeon (Acipenser sinensis), mainly endemic to the Yangtze River in China, is an endangered fish species. The natural population has declined since the Gezhouba Dam blocked its migratory route to the spawning grounds in 1981. In the near future, the completion of the Three Gorges Dam, the world's largest hydroelectric project, may further impact this species by altering the water flow of the Yangtze River. Little is currently known about the population genetic structure of the Chinese sturgeon. In this study, DNA sequence data were determined from the control region (D-loop) of the mitochondrial genome of adult sturgeons (n = 106) that were collected between 1995–2000. The molecular data were used to investigate genetic variation, effective female population size and population history of the Chinese sturgeon in the Yangtze River. Our results indicate that the reduction in abundance did not change genetic variation of the Chinese sturgeon, and that the population underwent an expansion in the past. AMOVA analysis indicated that 98.7% of the genetic variability occurred within each year's spawning populations, the year of collection had little influence on the diversity of annual temporary samples. The relative large effective female population size (N _ef) indicates that good potential exists for the recovery of this species in the future. Strikingly, the ratio of N _ef to the census female population size (N _f) is unusually high (0.77–0.93). This may be the result of a current bottleneck in the population of the Chinese sturgeon that is likely caused by human intervention. This revised version was published online in July 2006 with corrections to the Cover Date.     

中华鲟的保护生物学研究进展

中华鲟是一种洄游性的鲟科鱼类,平时生活于海洋,亲鲟成熟后溯游到江河里繁殖。在长江葛洲坝修筑以前,中华鲟产卵场位于长江上游和金沙江下游江段。６０－７０年代中期,一些科研单位对上游中华鲟繁殖群体及产卵场等进行了较为全面的调查,撰写出现敢《长江鲟鱼类生物学与人工繁殖研究》,中华鲟的人工繁殖也于１９７１年产首获成功。葛洲坝枢纽建成以后,中华鲟繁殖群体被阻隔于葛洲坝下游宜昌江段,围绕大坝对中华鲟生存带来的不     

Biology, fisheries, and conservation of sturgeons and paddlefish in China

This paper reviews five of the eight species of acipenseriforms that occur in China, chiefly those of the Amur and Yangtze rivers. Kaluga Huso dauricus and Amur sturgeon Acipenser schrenckii are endemic to the Amur River. Both species still support fisheries, but stocks are declining due to overfishing. Acipenseriformes of the Yangtze River are primarily threatened by hydroelectric dams that block free passage to spawning and feeding areas. The Chinese paddlefish Psephurus gladius now is rare in the Yangtze River system, and its spawning activities were severely limited by completion of the Gezhouba Dam in 1981. Since 1988, only 3–10 adult paddlefishes per year have been found below the dam. Limited spawning still exists above the dam, but when the new Three Gorges Dam is complete, it will further threaten the paddlefish. Artificial propagation appears to be the only hope for preventing extinction of P. gladius, but it has yet to be successfully bred in captivity. Dabry's sturgeon A. dabryanus is a small, exclusively freshwater sturgeon found only in the Yangtze River system. It is concentrated today in reaches of the main stream above Gezhouba Dam. The fishery has been closed since 1983, but populations continue to decline. Acipenser dabryanus has been cultured since the 1970s, and holds promise for commercial aquaculture; availability of aquacultural methods offers hope for enhancing natural populations. The Chinese sturgeon A. sinensis occurs in the Yangtze and Pearl rivers and seas of east Asia. There is still disagreement about the taxonomy of the Pearl and Yangtze River populations. The Yangtze River population is anadromous. Adults begin spawning at about age 14 years (males) and 21 years (females), and adults spend over 15 months in the river for reproduction. Spawning sites of A. sinensis were found every year since 1982 below the Gezhouba Dam, but it seems that insufficient suitable ground is available for spawning. Since 1983, commercial fishing has been prohibited but more measures need to be taken such as establishing protected areas and characterizing critical spawning, summering and wintering habitats.     

Assessing the effect of the Three Gorges reservoir impoundment on spawning habitat suitability of Chinese sturgeon (Acipenser sinensis) in Yangtze River,China

The Chinese sturgeon (Acipenser sinensis), a kind of maricolous anadromous migratory fish species, is endangered and protected in China. Historical spawning habitats were distributed in the lower reaches of Jinsha River and the upper reaches of Yangtze River. Since the establishment of the Gezhouba water conservancy pivot in 1981, the migratory route of Chinese sturgeon spawning was blocked. Therefore, the fish was forced to propagate in a new spawning ground which was mainly distributed in the 4-km-long mainstream from Gezhouba Dam to Miaozui in the middle Yangtze River. After water storage and power generation of the Three Gorges reservoir (TGR) in 2003, the propagation of Chinese sturgeon has been impacted gradually. According to field surveys, the fish used to spawn twice a year before TGR impoundment, but only once happened after that. Besides, the spawning scale is also declining with each passing year.In order to simulate and evaluate the effect of TGR impoundment on spawning habitats of Chinese sturgeon, with consideration of their reproductive characteristics, an eco-hydrodynamic model was established by coupling a two-dimensional hydrodynamic model and a fuzzy fish habitat module based on fuzzy logic inference. Flow fields at the studied site in an impoundment scenario and an assumed no impoundment scenario were simulated with the 2D hydrodynamic model. Afterwards, by linking hydrodynamic conditions to the expert knowledge base, the fuzzy habitat model used fuzzy logic inference to compute habitat suitability of the Chinese sturgeon. In addition, the approach was used to propose a suitable instream flow range during the propagation period for Chinese sturgeon. The results indicated that the suitable instream flow needed for Chinese sturgeon spawning in middle Yangtze River should be between 10,000 m³/s and 17,000 m³/s and it also showed that after TGR was put into pilot impoundment operation at the designed water level of 175 m, the habitat suitability has decreased significantly in October. Besides, the water temperature of spawning habitat increased to a higher level in propagation period due to the impoundment of the TGR. All these alterations have had imposed tremendous impacts on the propagation of Chinese sturgeon. Therefore, adjusting impoundment schedule of the TGR to recover the water flow over spawning habitat in October is a crucial way to improve the habitat suitability. Furthermore, the presented method also provides a theoretical basis for further research on the assessment of habitat suitability of aquatic species at a micro-habitat scale.     

水生所与三峡和葛洲坝水利工程中的鱼类保护

葛洲坝和三峡水利枢纽是世界上著名的大型水电工程, 对长江中下游防洪、发电、航运、水资源利用等产生了巨大的综合效益。如何减轻葛洲坝-三峡工程对长江流域生态环境及水生生物的影响经历了漫长而激烈的论证过程。中国科学院水生生物研究所(以下简称“水生所”)自始至终参加了这两个工程的水域生态环境影响评价和鱼类保护工作, 并且做出了重要的贡献。在葛洲坝工程的救鱼对象讨论中, 水生所指出救鱼的主要对象是中华鲟; 在救鱼的措施方面, 水生所科学论证了葛洲坝工程不必修建过鱼设施, 中华鲟在葛洲坝下能够自然繁殖, 中华鲟的救护措施以人工繁殖放流和产卵场的保护为主。在葛洲坝工程建设后, 水生所进一步预测了三峡工程对长江珍稀特有鱼类、重要经济鱼类以及渔业的影响, 并且建议在赤水河建立自然保护区, 作为长江上游珍稀特有鱼类的庇护所; 提出最早的生态调度想法, 通过三峡水库的调度形成人造洪峰, 刺激“四大家鱼”产卵等等。实践证明, 水生所做出的工程影响评价和鱼类保护建议是科学的、符合客观实际的, 对国家的决策起到了重要作用。     

Using drift nets to capture early life stages and monitor spawning of the Yangtze River Chinese sturgeon (Acipenser sinensis)

A sampling system for capturing sturgeon eggs using a D-shaped bottom anchored drift net was used to capture early life stages (ELS) of Chinese sturgeon, Acipenser sinensis , and monitor annual spawning success at Yichang on the Yangtze River, 1996–2004, before and just after the Three Gorges Dam began operation. Captured were 96 875 ELS (early life stages: eggs, yolk-sac larvae = eleuthero embryos, and larvae); most were eggs and only 2477 were yolk-sac larvae. Most ELS were captured in the main river channel and inside the bend at the Yichang spawning reach. Yolk-sac larvae were captured for a maximum of 3 days after hatching began, indicating quick dispersal downstream. The back-calculated day of egg fertilization over the eight years indicated a maximum spawning window of 23 days (20 October–10 November). Spawning in all years was restricted temporally, occurred mostly at night and during one or two spawning periods, each lasting several days. The brief temporal spawning window may reduce egg predation by opportunistic predators by flooding the river bottom with millions of eggs. During 1996–2002, the percentage of fertilized eggs in an annual 20-egg sample was between 63.5 to 94.1%; however, in 2003 the percentage fertilized was only 23.8%. This sudden decline may be related to the altered environmental conditions at Yichang caused by operation of the Three Gorges Dam. Further studies are needed to monitor spawning and changes in egg fertilization in this threatened population.     

Effects of damming on population sustainability of Chinese sturgeon, <Emphasis Type="Italic">Acipenser sinensis</Emphasis>: evaluation of optimal conservation measures

The numbers of spawning sites for Chinese sturgeon have been drastically reduced since the construction of the Gezhouba Dam across the Yangtze River. This dam has blocked migration of Chinese sturgeon to their historic spawning ground causing a significant decline of the Chinese sturgeon population. We conducted a VORTEX population viability analysis to estimate the sustainability of the population and to quantify the efficiency of current and alternative conservation procedures. The model predicted the observed decline of Chinese sturgeon, resulting from the effect of the Gezhouba Dam. These simulations demonstrated the potential interest of two conservation measures: increasing spawning area and reducing predation on sturgeon eggs. The simulations also demonstrated that the actual restocking program is not sufficient to sustain sturgeon population as the artificial reproduction program induce the loss of more wild mature adults that the recruitment expected by the artificial reproduction.     

VARIATION OF RUNOFF IN THE YICHANG REACH OF YANGTZE RIVER AND ITS INFLUENCE TO THE CHINESE STURGEON SPAWNING UNDER THE CASCADED HYDROPOWER OPERATION北大核心CSCD

Based on the Gini coefficient and Mann-Kendall test, the runoff variation in the Yichang reach of Yangtze River from 1982 to 2017 was evaluated, and its influence to the Chinese sturgeon spawning below the Gezhouba Dam was discussed under the cascaded hydropower operation. The results showed that the runoff and Gini coefficient decreased significantly after the construction of Gezhouba Dam, which synchronously decreased the flow and water levels in spawning days of the Chinese sturgeon. Water temperature had no significant change. The analysis of the abruption revealed great change of hydrological conditions in the spawning days and Gini coefficient in 2004 and 2009, which are coincided with time of the second and fourth phase impoundment of the Three Gorges Reservoir. The correlation analysis indicated that the higher runoff and Gini coefficient would induce Chinese sturgeon to spawn in days with high flow and water levels. These results suggest that the ecological operation of the Three Gorges-Gezhouba cascaded hydropower could enhance the runoff with large inequality and create long duration of high flow pulses during flood seasons. © 2019, Institute of Hydrobiology, Chinese Academy of Sciences. All rights reserved.     

Assessing the effect of Separation Levee Project on Chinese sturgeon (<Emphasis Type="Italic">Acipensor sinensis</Emphasis>) spawning habitat suitability in Yangtze River,China

Chinese sturgeon (Acipenser sinensis) is a protected anadromous fish species. The migration pattern of the fish has been blocked by the construction of Gezhouba Dam, reducing the natural spawning site length to less than 7 km along the Yangtze River. However, the fish has since established an alternative spawning ground in the narrow reach downstream of Gezhouba Dam. To enhance navigation, a Separation Levee Project (SLP) was implemented in the new-found spawning habitat of the fish. To therefore evaluate the effect of the SLP on Chinese sturgeon spawning habitat suitability, the conditions in the spawning habitat were simulated using River2D (a two-dimensional hydrodynamic model). Two main approaches (habitat kinetic energy and circulation metrics) were used in the simulation. The study showed that SLP only slightly changed the physical conditions in the spawning habitat. Using hydrodynamic simulation, the weighted usable area (WUA) before and after the SLP construction was also computed and habitat preference curve developed for water depth and velocity. On the average, SLP reduced WUA—a finding that was consistent with field-measured data. Based on WUA, the habitat conditions were more sensitive to SLP proximity than metrics based on velocity gradients. SLP posed detrimental impacts on the suitability of spawning habitats of Chinese sturgeon. The findings in this study provide further basis for the protection and restoration of Chinese sturgeon spawning habitats in especially the lower reach of Yangtze River.     

厚颌鲂和圆口铜鱼耗氧率与窒息点的测定

用封闭静水式装置测定了体重2.3-4.7g厚颌鲂幼鱼的耗氧率和窒息点,用封闭静水式和封闭流水式装置测定了体重9.9-55.1g圆口铜鱼的耗氧率和窒息点。结果表明:在15-27℃条件下,厚颌鲂的耗氧率随着温度的升高而升高,耗氧率与水温呈线性关系;在水温24.8℃时厚颌鲂的窒息点为(0.91±0.08)mg/L。在水温23-27℃、封闭静水实验条件下,圆口铜鱼的耗氧率随体重增加而降低,两者呈指数关系;圆口铜鱼耗氧率昼夜变化明显,夜间耗氧率大于白天,推测圆口铜鱼夜间活动较多。在水温24.5-26.0℃条件下,体重21.8-46.3g圆口铜鱼的窒息点变幅较小,平均(1.14±0.23)mg/L。研究表明两种鱼都为耗氧率和窒息点较高的鱼类。       

中华鲟的性腺发育与退化问题研究

中华鲟(Acipenser sinensis) 是我国的一级重点保护野生动物, 也是长江水生动物保护的旗舰物种。近年来, 中华鲟已多次被监测到未进行野外自然繁殖, 其生存前景堪忧。有关其没有繁殖的原因存在多方面的争议, 尤其是黄真理等提出葛洲坝水利枢纽修建造成中华鲟性腺退化严重, 是导致中华鲟种群数量急剧减少的主要因素; 同时, 还宣称“中科院水生所有关否定中华鲟性腺退化的方法和材料, 是不充分和不可靠的”。为了避免该错误观点对中华鲟的保护造成误导, 文章从中华鲟的性腺发育过程及退化的判断标准、中华鲟的生活史阶段及性腺状态、葛洲坝与三峡工程对中华鲟繁殖影响等方面, 分析该观点的谬误之处。柯福恩等将正常发育的中华鲟III期性腺误判为是“退化性腺”; 文章认为刚进入长江不久的中华鲟亲鱼即出现性腺退化, 不符合中华鲟性腺发育的规律。多年监测数据显示, 葛洲坝水利枢纽导致中华鲟洄游距离缩短并没有改变中华鲟繁殖的时间格局, 也没有改变中华鲟性腺成熟的比例。黄真理等歪曲他人实际监测的数据, 提出的洄游距离影响中华鲟性腺发育的模型纯粹是不懂鱼类生物学的人玩弄的数学游戏。尽管现阶段中华鲟的保护确实遇到了困境, 但随着“长江十年禁渔”的实施, 电捕和滚钩等彻底取缔, 限制产卵场区域人类活动, 加强中华鲟野外产卵场的修复, 并进行更大规格、更大规模的群体放流, 中华鲟的种群还是有可能恢复的。     

中华鲟天然群体蛋白质水平遗传多样性贫乏的初步证据

为阐明我国Ⅰ级珍稀水生保护动物中华鲟天然群体的遗传结构和遗传多样性特征,为其资源的监测量民保护提供科学依据,采用聚丙烯酰胺梯度凝胶电泳技术对中华鲟天然群体进行了蛋白质遗传多态性研究。共研究了１５种蛋白质,有４种蛋白无活呈活性很低,在有活性的１１种蛋白中人测得２６个座位;在２６个座位中,只有１个座位（ＭＤＨ－１）为多态座位。中华鲟多态座位比例（Ｐ）为３．９０％,遗传杂合度（Ｈ）为０．０４,均远远低于     

Biology and life history of Dabry's sturgeon, Acipenser dabryanus, in the Yangtze River

Dabry's sturgeon, Acipenser dabryanus, is a relatively small (130 cm, 16 kg) and now rare sturgeon restricted to the Yangtze River Basin. It behaves as a resident freshwater fish, does not undertake long distance migrations (except for spawning), and lives in a variety of habitats. It historically spawned in the upper Yangtze River, but the spawning sites are unknown. Acipenser dabryanus reaches maturity earlier than do other Chinese sturgeons, which gives the species aquaculture potential, and artificial spawning has been carried out. However, the native population in the Yangtze has sharply declined in the last two decades due to overfishing, pollution and habitat alteration and destruction, especially since the construction of the Gezhouba Dam, which was built in 1981 across the Yangtze River at Yichang, Hubei Province. Since 1981, Dabry's sturgeon rarely occurs below the Gezhouba Dam because downstream movements are blocked. Clearly, conservation of Dabry's sturgeon must be emphasized. Conservation methods may include protecting habitats, controlling capture and stock replenishment.     

Potential causes of habitat degradation and spawning time delay of the Chinese sturgeon (Acipenser sinensis)

In fish conservation, it is important to simulate fish habitat suitability and determine the potential impact on habitat quality and species behavior. This study analyzed the impact of several hydraulic projects on fish habitat quality and spawning time by numerical modeling. The case study involved the only Chinese sturgeon spawning site in the Yangtze River, China. Four habitat assessment indexes reflected both habitat quality and spatial characteristics, including fragmentation and connectivity. Previous studies did not simulate the water temperature impact on the fish habitat; spawning time delay was attributed to water temperature increases and discharge decreases. The results of the present study showed that the water temperature increase from the Three Gorges Reservoir (TGR) impoundment primarily caused the habitat degradation and spawning time delay. The effect of the water temperature increase on the degradation of average habitat suitability was eight times that of a decrease in discharge. A 25-day delay in the water temperature trend line was significantly correlated with a 26-day delay in the first spawning date. A decrease in discharge after TGR impoundment did not cause the spawning date delay. The Dike Project mainly impacted spawning site connectivity. Controlling the water temperature of the released water discharge is the most important means of conserving the wild Chinese sturgeon. This research can benefit other regions considering hydraulic projects by identifying potential factors impacting fish habitat quality and overall ecosystem health.     

Three Gorges Dam and Its Impact on the Potential Transmission of Schistosomiasis in Regions along the Yangtze River

Large-scale hydroprojects have a propensity for incurring schistosomiasis epidemics by altering the environments of their vicinities. As the construction of the Three Gorges Dam, one of the world’s largest hydroprojects to date, draws near its conclusion, an assessment of the dam’s capacity in causing schistosomiasis becomes more urgent and pressing. This article reviews recent investigations into the possible effects of the dam on schistosomiasis in the Three Gorges region and areas along the Yangtze downstream from the dam. Data used in this article were extracted from peer-reviewed papers found in PubMed, Chinese Journal of Parasitology and Parasitic Diseases, and Chinese Journal of Schistosomiasis Control. Results indicate that the Three Gorges Dam is capable of inducing a wide variety of environmental and ecological changes both within the Three Gorges region and in downstream areas. These changes, however, carry ambivalent implications for the reproduction of Oncomelania snails and the spreading of schistosome infections. Furthermore, major changes in the demographics and agricultural practices of the Three Gorges and downstream Yangtze areas caused by the dam could also exert significant influence on the transmission of schistosomiasis in these regions. Major conclusions of this review include the need for further ecological simulations of the Three Gorges Dam and the need for deploying monitoring and intervention systems to provide successful prophylaxis of the Three Gorges Dam-associated schistosomiasis emergence.     

基于中华鲟繁殖群体数量的长江中、下游生态环境考核指标

繁殖群体数量是中华鲟能否成功繁殖的重要影响因子, 建议作为长江生态考核的重要评价指标。根据重要种群参数和历史数据, 基于稳态转换理论和方法, 确定中华鲟繁殖群体数量指标的评估基准值和等级, 670尾以上为“优”、400—670尾为“良”、200—400尾为“中”、50—200尾为“差”、50尾以下为“极差”。水声学探测结果显示, 1998—2001年中华鲟繁殖群体数量指标评级为“良”; 2004—2012年三峡工程蓄水后至向家坝蓄水前评级为“中”; 2013—2020年评级为“极差”。为了复壮中华鲟野生种群, 建议修复葛洲坝下中华鲟产卵场功能, 大规模放流性成熟亲鱼和大规格个体, 建立国家级中华鲟保育中心。     

The state of natural reproduction of stellate sturgeon Acipenser stellatus in the Lower Volga

Data obtained during 1979–2005 on the natural reproduction of stellate sturgeon Acipenser stellatus and water level in the Volga River were analyzed. The relationship between the number of stellate sturgeon larvae migrating down the river, flow quantity during the summer period of low water and the number of spawners entering spawning grounds was shown. Fish productivity of spawning grounds located in the river channel in different zones of the Lower Volga was estimated. Recommendations are presented concerning the increase in the level of stellate sturgeon natural reproduction in the lower pool of the Volgograd hydrosystem.     

Using adaptive resolution imaging sonar to investigate Chinese sturgeon (Acipenser sinensis Gray, 1835) behaviour on its only spawning ground in the Yangtze River

The present study investigated the presence of Chinese sturgeon Acipenser sinensis on its only remaining spawning ground (below the Gezhauba Dam), and monitored the behaviour under different environmental conditions from 24 December 2015 to 23 January 2016. A fixed ARIS (Adaptive Resolution Imaging Sonar) system was used and a total of 72 Chinese sturgeon were detected during nine observations. Detections initially recorded a few A. sinensis in the early days of late‐December 2015, with an increase in recordings, leading to a peak in early‐January 2016 and declining thereafter. Water temperature slowly decreased during the study period from 18.1 to 15.7°C. During the middle of this temperature decline the sturgeon observations peaked, suggesting that Chinese sturgeon could have an optimal temperature range. The sturgeon Detections Per Unit Effort (DPUE) was higher in the night hours, peaking before dawn, suggesting a circadian behaviour rhythm. Sturgeon spawning was not observed during the investigation period. A delay in the decrease in water temperature caused by the Three Gorges Reservoir and the few numbers of reproductively mature individuals are suspected to have contributed to the failure in natural breeding.     

Migration of green sturgeon, Acipenser medirostris, in the Sacramento River

Adult green sturgeon, Acipenser medirostris, were collected in San Pablo Bay, California, and surgically implanted with ultrasonic acoustic tags from 2004 to 2006. An array of automated acoustic monitors was maintained in the Sacramento River to record movements of these fish. We presumed movements to known spawning areas (based on previous green sturgeon egg collections) or areas with potential spawning habitat (characterized by substrate, flow, and temperature criteria) represented a “spawning migration.” Three separate annual “spawning migrations” were recorded involving 15 individuals. The majority of the Sacramento River migrants entered the system in the months of March and April. Two different patterns of “spawning migration” and out-migration were observed. Six individuals potentially spawned, over-summered and moved out of the river with the first fall flow event. This is believed to be the common behavior of the green sturgeon. Alternatively, nine individuals promptly moved out of the Sacramento River before 1 September, and any known flow or temperature cue. Some green sturgeon appeared to be impeded on their upstream movement by the 15 May closure of the Red Bluff Diversion Dam, and at least five passed under the dam gates during downstream migration. A delay in the closure of the Red Bluff Diversion Dam would likely allow upstream passage of spawning green sturgeon, further, the potential mortality affects of downstream passage beneath the Red Bluff Diversion Dam should be assessed. Specific protection should be also given to the large aggregation of green sturgeon located in the reach of the Sacramento River adjacent to the Glen Colusa Irrigation District pumping facility.     

Spatial distribution and habitat suitability indices for non‐spawning and spawning adult Chinese sturgeons below Gezhouba Dam,Yangtze River: Effects of river alterations

The study objectives were to identify the horizontal and vertical distributions of adult Chinese sturgeon (Acipenser sinensis) in relation to the Habitat Suitability Index (HSI) in order to assess the utility of the only remaining spawning grounds by adults and to understand the effects of river alterations on habitat use. Twenty‐five adults were surgically implanted with ultrasonic transmitters and located by mobile tracking and fixed monitoring stations during the 2006–2009 spawning seasons. Fish locations and depths along with water depth and bottom characteristics (topography, velocity, and embeddedness) were measured during tracking and used to determine HSI curves for non‐spawning and spawning adults. Most fish locations (91%) were on the spawning grounds (GZD to Miaozui reaches). Horizontal distribution differed before and after spawning, among years, and between the sexes. Adults used deeper depths during the day than at night (P < 0.001), while also preferring shallower depths on the day of spawning rather than the days before and after. Mature females used deeper water than other females (P < 0.001). Comparison of horizontal and vertical distributions before and after river alterations found fewer adults using the grounds impacted by a diversion dike which was built on the spawning grounds. Adults also used shallower depths after the Three Gorges Dam regulated river flow over the spawning grounds. The HSI model and the use of Weighed Usable Areas (WUA) for mature and immature adults indicated suitable habitat was available, but was reduced by the river alterations resulting in reduced spawning success and placing the population into a situation close to extirpation.