Gezhouba Dam Research Articles

Sudden change of fish functional compositions during a drought in the wet season of the middle Yangtze River, China

Climate anomalies such as drought may lead to cascading effects on river ecosystems, ultimately resulting in the change of aquatic biocenosis. Here, we investigated functional assemblies of fish communities at three sites below the Gezhouba Dam of the middle Yangtze River in China before and during a drought event from 2021 to 2022. As the drought proceeded, the richness of the fish functional groups decreased, and the abundance of demersal/invertivore species increased. These changes might indicate adaptive responses of fish communities to the reduction in water volume and shrinkage in habitat areas. The shifts in functional structure also caused fish communities to become more similar during the drought. The null model based on functional traits showed a distance effect of the fish community assembly rules. The communities close to the dam were structured more stochastically under drought stress, which may be attributed to the impact of ecological operation by cascade hydro-junctions. In contrast, the communities far away from the dam were structured by environmental filtering. Our results support the hypothesis that the natural hydrological regime is the main force driving the spatiotemporal dynamic of riverine fish assemblages, and the drought stress on fish communities may need more attention to cope with future biodiversity loss under global climate changes.

Migration dynamics simulation of migratory fish in rivers

The decline of migratory fish stocks is a major problem facing the global aquatic ecosystem. Understanding the dynamics of fish migration and their entire life history is crucial for quantitatively assessing the impact of natural and anthropogenic barriers on migratory fish and to understand the mechanisms of their decline. However, this understanding is largely ambiguous due to limited field survey data in the absence of models. Although Huang and Wang (Curr. Biol. 28, 2018, 3640–3647) and Huang (iScience 19(9), 2019, 772–785) proposed a Migration Dynamics Model (MDM) to describe the upriver and downriver migration processes of the Chinese sturgeon, but a crucial intermediate link—the breeding aggregation process—is still missing, while the standard Crank-Nicolson scheme, a common computational method, of finite difference methods cannot adapt to the model parameters changing with time and space. Here we propose a six-point implicit scheme to address the complexity of model parameters. The parameters of migration speed and diffusion coefficient are decomposed into fish-related and current-related components for analyzing their effects on model parameters and estimating them. Additionally, we propose a parameterization method for the aggregation process of spawners during the breeding season by introducing a set of clustering functions. Next, we examine the complete migration processes of adult and juvenile Chinese sturgeons in the Yangtze River and elucidate the underlying mechanisms behind the fish migration dynamics, including their spatiotemporal distributions, aggregation behavior, and migration schedule. We discover that the Gezhouba Dam (GD) significantly impacted the breeding aggregation behavior of Chinese sturgeon during the breeding season. The GD altered the distribution of fish along their migration path and schedule. Prior to the construction of the dam, 99.9 % of the total Chinese sturgeon were able to reach the 240 km-long spawning ground. However, after the dam was built, only 36.7 % were able to reach the 30 km-long spawning ground below the GD on the day of mating. Finally, we discuss the aggregation phenomenon and its driving factors during Chinese sturgeon migration, and categorize it into three types, namely biotic-driven, abiotic-driven and dual-driven aggregation behaviors. We reveal the existence of aggregations for non-biological reasons, such as the slowdown of fish migration speed induced by natural and anthropogenic barriers and estuarine tidal effects.

The last giants of the Yangtze River: A multidisciplinary picture of what remains of the endemic Chinese sturgeon

The Chinese sturgeon, an important endemism of the Yangtze River, belongs to ‘the most critically endangered group of species’ worldwide, with overfishing and habitat destruction being the main drivers towards extinction. Newly obtained microchemical comparisons between animals and water from different river locations revealed a probable shifting of the spawning ground few kilometers downstream compared to the only previously known site, located under the Gezhouba Dam. This offers a glimmer of hope for an adaptive response to habitat perturbation caused by the recently built Three Gorges dam on the Yangtze River. On the other hand, genetic data provide an estimate of about 20 breeders participating in the only significant breeding event of the past 10 years. This warns of a near species extinction forecast if no in situ and ex situ conservation efforts occur promptly. Given these results we propose a list of priority conservation actions that urgently need to be promoted, supported, and put into practice.

The impact of dams on the river connectivity of the two largest river basins in China

AbstractDams are built on rivers for power generation, flood prevention and control, and water resources utilization. However, dams also reduce the connectivity of rivers, which hinders the exchange of material and organisms within rivers. The Yangtze River Basin and the Yellow River Basin are the two largest river basins in China. In this study, the connectivity of these two huge and highly impacted systems was investigated. The Dendritic Connectivity Index (DCI) was applied to evaluate the impact on river connectivity of dams with a reservoir capacity of larger than 0.1 km3. The results show that river connectivity decreased following an increase in dam construction. The connectivity of the Yangtze River Basin was close to 80 (0 is completely disconnected and 100 is connectivity under natural condition) in the 1980s, but declined significantly after the Gezhouba Dam was constructed on the mainstream of the Yangtze River. From 1980 to 2010, the connectivity of the Yellow River Basin was always lower than that of the Yangtze River Basin. The changes in the connectivity indices of potamodromous fish (DCIp) and diadromous fish (DCId) were determined for the period of 1980–2010. In the Yangtze River Basin, the DCIp decreased by 67.28% and the DCId decreased by 65.72%. In the Yellow River Basin, the DCIp decreased by 43.8% and the DCId decreased by 100%. In conclusion, the construction of dams, especially those on the main stream, has reduced the connectivity of the basin. The connectivity of the Yangtze River Basin and the Yellow River Basin has been severely affected.

What is actually the main cause for the survival crisis of Chinese sturgeon?

野生中华鲟（Acipenser sinensis）种群正面临灭绝的风险，一个重要原因是长期以来对其生存危机的主因缺乏共识，导致缺乏针对性保护措施.基于中华鲟种群模型，我们把主流专家提出的五个主因——捕捞、污染、航运、全球气候变化、水利工程与中华鲟种群衰退的影响因子进行对比，归并为繁殖群体损失、补充群体损失、存活率降低和长江水坝累积影响四种可能因子，在此基础上进行单因子和多因子情景计算和分析，并评估这些情景发生的可能性.结果表明：长江水坝的累积影响是中华鲟生存危机的主因.捕捞、污染、航运等其他因素对种群数量有一定不利影响.我们的定量情景计算和分析，验证了1982年中央批准把中华鲟列为葛洲坝救鱼唯一对象的共识和观点-葛洲坝对中华鲟影响最大；揭示了长江水坝对中华鲟种群衰退和灭绝风险的影响机制；厘清了各影响因素的主次关系，否定了长期存在的、把中华鲟生存危机主因归咎于非法捕捞、污染、航运、全球气候变化等传统主流观点.我们认为，要挽救野生中华鲟种群，必须采用针对性措施减缓长江水坝的影响，恢复野生群体的自然繁殖是中华鲟保护的当务之急.;The wild Chinese sturgeon (Acipenser sinensis Gray, 1835) has been facing the risk of extinction due to no consensus on the chief culprit of its survival crisis for a long time, resulting in the absence of targeted protection measures. Based on our population model of Chinese sturgeon, we merged the five potential culprits proposed by the elite experts—illegal fishing, pollution, shipping, global climate change and Yangtze dams—to the four possible factors of Chinese sturgeon population decline, which are breeding population loss, recruit population loss, reducing survival rate, and cumulative effects of the Yangtze dams. Then we calculated single-factor and multi-factor scenarios of anthropogenic activities and evaluated the possibility of these scenarios. The results show that the cumulative impact of the Yangtze dams is the main cause of the survival crisis of Chinese sturgeon. Other factors such as fishing, pollution, and shipping have a certain adverse effect on the population. Our quantitative scenario calculation and analysis validated the consensus that the Chinese sturgeon was listed as the sole target for the fish rescue programme of Gezhouba Dam (GD) in 1982 because of the worst impact of the GD on the Chinese sturgeon. We reveal the impact mechanism of the Yangtze dams on the decline and even extinction and overturn the long-standing mainstream opinions that the survival crisis of Chinese sturgeon was caused by illegal fishing, pollution, shipping, or global climate change. Then we suggest that targeted measures must be adopted to mitigate the impact of the Yangtze dams to save wild Chinese sturgeon and restoring the natural reproduction of wild population is now the urgent matter for the Chinese sturgeon conservation.

Spatiotemporal photosynthetic physiology responses of remnant Myricaria laxiflora populations to regulated water level fluctuations.

The construction of the Three Gorges–Gezhouba Dam cascade hydropower station has changed the water level fluctuation pattern of the habitats for remnant rare and endangered Myricaria laxiflora populations downstream of the dam. The present study utilized biochemical markers of photosynthetic physiology to evaluate the spatiotemporal responses of remnant populations to human-regulated water level fluctuations. The results showed that the photosynthetic physiological activities of remnant M. laxiflora populations underwent a period of rapid growth, followed by a gradual decline in the growth recovery phase after flooding. During the entire experimental period, photosynthetic physiological activities of remnant M. laxiflora populations changed with prolongation of emergence time: specifically, net photosynthetic rate and stomatal conductance initially decreased and then subsequently increased, intercellular carbon dioxide concentrations peaked at mid-phase and transpiration rate continuously increased. The maximum net photosynthetic rate, apparent photosynthetic quantum efficiency and dark respiration rate in the light–response curves of the plants continuously increased during growth. The water level gradient also significantly affected the photosynthetic physiological activities in the remnant populations, i.e. the photosynthetic physiological activities of high-altitude plants were significantly higher than the middle- and low-altitude plants. The changes in photosynthetic pigment content of plants in remnant populations during the growth recovery phase and the entire growth period were similar to those occurring in photosynthetic activities in plants. Further, canonical correspondence analysis showed that photosynthetic physiological activities in the plants were significantly correlated with changes in water levels, emergence time, elevation gradient, soil water and soil nitrogen contents. Therefore, the artificial regulation of water level fluctuations by large hydropower stations will inevitably affect the photosynthetic activities and growth of remnant M. laxiflora populations.

Drifting with Flow versus Self-Migrating-How Do Young Anadromous Fish Move to the Sea?

SummaryThe downriver migration process of young anadromous fish has a far-reaching impact on their survival rate and the efficacy of hatchery-reared fish release, but it is poorly understood. Moreover, the impact of dams on the fish remains unclear. The Chinese sturgeon is an anadromous and dam-affected fish in the Yangtze River. Here, we propose a novel theoretical framework to reveal the migration process of young Chinese sturgeon. We clarify the effects of active swimming of fish and water flow on the downriver migration and the parametric traits of the migrational stages. Then, we show that the young fish migrate downriver along the inshore waters in a gradually transforming manner from passive drift to active swimming. Lastly, we evaluate the impact of the Gezhouba Dam (GD) on the migration of the young fish, as well as demonstrate the life cycles of Chinese sturgeon in the Yangtze River pre- and post-GD.

Drifting with Flow Versus Self-Migrating ― How Young Anadromous Fish Move to Sea

The downriver migration process of larval or juvenile fish has a far-reaching impact on the survival rate of fish and the efficacity of hatchery-reared fish release and remains fragmented. Moreover, the quantitative mechanism of dam impact on the fish remains unclear. The Chinese sturgeon in the Yangtze River is a typical example or model organism of anadromous or dam-affected fish. Here, we propose a novel theoretical framework to reveal the downriver migration process of young Chinese sturgeons in the Yangtze River. We clarify the effects of active swimming of fish and the river’s hydrologic elements on the downriver migration, and the parametric traits of the migration stages. Then we show that the young fish migrate downriver along the inshore waters in a gradual transforming manner from passive movement to active swimming. Furthermore, we evaluate the impact of the Gezhouba Dam (GD) on the downriver migration of the young fish and achieve the lifecycles of Chinese sturgeon in the Yangtze River pre- and post-GD.

Combined effects of multiple large-scale hydraulic engineering on water stages in the middle Yangtze River

Investigation of water stages influenced by human projects provides better understanding of riverine geomorphological processes and river management. Based on hydrological data collected over ~60years, an extreme stage-extreme discharge analysis and a specific-gauge analysis were performed to research the individual and combined effects of multiple engineering projects on a long-term time series of water stages in the middle Yangtze River. Conclusions are as follows. (1) In accordance with the operation years of the Jingjiang cutoff (CF), the Gezhouba Dam (GD), and the Three Gorges Dam (TGD), the time series (1955–2012) was divided into periods of P1 (1955–1970), P2 (1971–1980), P3 (1981–2002), and P4 (2003−2012). Water stage changes during P1–P2, P2–P3, and P3–P4 are varied because of the differences in the types and scales of these projects. The stage decreased at Shashi and increased at Luoshan owing to the operation of the CF. Additionally, after the GD was constructed, the low-flow stage decreased in the upstream reach of Chenglingji and increased in its downstream reach, whereas the flood stage merely decreased at Yichang. Moreover, the TGD resulted in an overall decrease in low-flow stages and a limited increase in flood stages because of the differential adjustments of river geometry and resistance between the low-flow channel and flood channel. (2) Although differences existed in the scouring mechanisms between streamwise erosion associated with dams and headward erosion associated with cutoffs, particular bed textures in the gravel reach led to a similar adjustment that stage reduction at Shashi was the greatest of all stations, which caused the flow slope and sediment transport capacity to decrease in the sandy reach. (3) These engineering projects caused changes in average low-flow and flood stages that varied between Yichang (−1.58 and −0.08m respectively), Shashi (−3.54 and −0.12m), and Luoshan (1.15 and 0.97m) from P1 to P4. However, less influence was observed at Hankou owing to its remote location and the short impoundment time of the TGD. (4) Potentially detrimental decreases in low-flow stages and increases in flood stages should be monitored and managed in the future. Our results are of practical significance for river management and the evaluation of the influences of large-scale anthropogenic activities on the hydrological regimes of large rivers.

Assessing the hydrologic alteration of the Yangtze River using the histogram matching approach

Hydrologic changes of the Yangtze River, an important river with abundant water resources in China, were investigated using the Histogram Matching Approach. Daily streamflow data spanning the time interval from 1955 to 2013 was collected from Yichang and Datong stations, which monitor the hydrologic processes of the upper and lower reach of the Yangtze River, respectively. The Gezhouba Dam, the first dam constructed at the main stream of the Yangtze River, started operations in 1981. 1981 was used to differentiate the pre-dam (1955-1980) and post-dam (1981-2013) hydrologic regimes. The hydrologic regime was quantified by the Indicators of Hydrologic Alteration. The overall alteration degree of the upper Yangtze River was 31% and the alteration degree of every hydrologic indicator ranged from 10% to 81%. Only 1, 5 and 26 hydrologic indicators were altered at high, moderate and low degrees, respectively. The overall alteration degree of the lower Yangtze River was 30%, and the alteration degree of every hydrologic indicator ranged from 8% to 49%. No high alteration degree was detected at the Datong station. Ten hydrologic indicators were altered at moderate degrees and 22 hydrologic indicators were altered at low degrees. Significant increases could be observed for the low-flow relevant indicators, including the monthly flow from January-March, the annual minimum 1, 3, 7, 30 and 90-day flows, and the base flow index.

Dams induced stage–discharge relationship variations in the upper Yangtze River basin

Although stage–discharge relationships are crucial for discharge estimations and hydrological analyses, few efforts have been taken to assess their temporal alterations in the context of dam regulation. Here, the upper Yangtze River basin serves as an example to demonstrate the influence of hydraulic structures on stage–discharge relationships evolution. Daily records of water level and river discharge from 1950 to 2013 at Yichang hydrometric station were grouped and analyzed. Back-propagation artificial neural network was used to model the stage–discharge relationships. The obtained curves revealed substantial shifts since the Gezhouba Dam (GD) and Three Gorges Dam (TGD) were put into practice sequentially. In low flow scenarios, the decline of water levels due to GD and TGD regulation were variable with river discharge, whereas in normal flow scenarios, the rating curves indicate equilibrium state with almost the same slopes regardless of GD and TGD influence. In high flow scenarios, the rating curves representing natural condition, GD, and TGD regulation intersect with each other. Moreover, the detected changes in stage–discharge relationship were mainly in response to dam regulation, channel erosion and sand exploitation, while irrelevant to precipitation variability. The contribution of sand mining, GD regulation, and TGD regulation on rating curve variations at Yichang station were 36%, 11%, and 53%, respectively.

三峡蓄水以来葛洲坝下中华鲟产卵场河床质特征变化

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡蓄水以来葛洲坝下中华鲟产卵场河床质特征变化 DOI: 10.5846/stxb201306141703 作者: 作者单位: 中国水产科学研究院长江水产研究所,中国水产科学研究院长江水产研究所,中国水产科学研究院长江水产研究所,中国水产科学研究院长江水产研究所,中国水产科学研究院长江水产研究所,中国水产科学研究院长江水产研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然基金青年科学基金项目(31202003); 公益性农业行业专项(201203086) Changes of bottom substrate characteristics in spawning ground of chinese sturgeon downstream the gezhouba dam from impounding of three gorge reservoir Author: Affiliation: Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences,Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:中华鲟是国家一级保护水生动物,是产底层产粘性卵鱼类。河床质构成了中华鲟受精卵和早期胚胎发育的物理环境,其变化可能直接影响中华鲟自然繁殖的规模和效果。基于水声学和水下视频技术对葛洲坝下现存唯一已知中华鲟自然产卵场的河床质特征进行了连续观测,对三峡水库蓄水以来中华鲟自然产卵场的河床质特征变化进行了研究。水声学分析结果显示,2004-2012年间,中华鲟产卵场区域内河床硬度未有明显变化,但粗糙度显著增加 (P < 0.05)。对产卵位点的河床质特征分析表明,下产卵区的硬度增加(2012年显著高于2008和2004年 (P < 0.05)),上产卵区硬度呈明显下降趋势(2004年显著高于2008和2012年(P < 0.05));上产卵区的河床粗糙度均呈不显著上升趋势(P > 0.05);下产卵场区的河床粗糙度呈显著上升趋势(P < 0.05)。水下视频观测结果显示,三峡蓄水导致的水体含沙量明显减少,对河床的冲刷日益明显,表现在产卵场江段沉积细砂和粗砂区域面积显著减少,河床卵石缝隙充塞度明显下降 (P < 0.05)。下产卵区在2007-2012年视频观察过程中发现河床卵石缝隙充分暴露,几乎没有任何细砂或粗砂填充,与上产卵区河床卵石缝隙充塞度特征明显不同。长期观测表明,2004-2012年期间中华鲟自然产卵位点发生了明显的改变,2004-2007年均发生在下产卵区,而2008-2012年均发生在上产卵区,自然繁殖规模和效果也明显下降。综合分析显示,中华鲟产卵场河床质特征的变化可能是导致中华鲟自然产卵位点的改变和迁移的原因,进而影响中华鲟自然产卵场的繁殖适合度,影响中华鲟自然繁殖的规模和效果。对三峡蓄水清水下泄的生态影响评估以及中华鲟自然产卵场的改良或修复有重要借鉴意义。 Abstract:Since 2010, the Chinese sturgeon Acipenser sinensis, one of the first-class national protected animals in China, has been classified as Critically Endangered in the IUCN Red List of Threatened Species. The last spawning ground of the Chinese sturgeon is located just downstream from the Gezhouba dam(GZD) after its construction, and thus, it is critical to retain the availability of the spawning ground for the sustainability of the species. The riverbed substrate and its surrounding microhabitat supply an environment for survival and development of the embryos of the Chinese sturgeon, and so chronic change to riverbed characteristics could have significant consequences on the reproductive success of the Chinese sturgeon. Based on long-term investigation of the ecological factors linked with natural spawning and especially observation of the spawning substrate characteristics over the last 8 years, the arrangement and structure of the bottom substrate of the spawning ground have been greatly changed from impounding of water in the Three Gorge Reservoir (TGR). At the same time, the critically important spawning sites as well as the spawning scale have also changed with spawning events occurring at spawning sites downstream (SSD) from 2004 to 2007 and spawning sites upstream (SSU) from 2008 to 2012. The ecological effects of the bottom substrate on spawning success and embryo development of the Chinese sturgeon are still not well documented. To study the effects of bottom substrate characteristics linked to impounding of water in the TGR, acoustic surveys with a scientific echo-sounder (2004-2012) and underwater video surveys (2007-2012) were conducted in the 6 km reaches of the Yangtze river just downstream from GZD including the last spawning ground of the Chinese sturgeon. The echo-sounder surveys showed that great changes in bottom hardness (as seen in the 1st part of the 1st Bottom Echo from start to peak of the echogram) and roughness (as seen in the 2nd part of the 1st Bottom Echo from the peak to the end of the echogram) have occurred in the spawning ground. Even though bottom hardness did not change significantly over the whole spawning ground (P > 0.05), bottom hardness in the SSD in 2012 was significantly higher than that in 2008 and 2004 (P < 0.05), while at same time, bottom hardness in the SSU in 2008 and 2012 was significantly lower than in 2004 (P < 0.05). Bottom roughness over the whole spawning ground and in the SSD increased significantly from 2004 to 2012 (P < 0.05), while no significant changes were found in the SSU.Underwater video surveys showed that with the erosion by the cleaner water impounded in the TGR, the coarse and fine sand that could be observed in the spawning ground in 2008 had almost completely disappeared in 2012 and the embeddedness (a term describing the degree to which river bottom gravel, cobbles and boulders were covered or had settled into the coarse and fine sand of the river bottom as obervered from the underwater video surveys) in the whole study area had decreased dramatically (P < 0.05). The embeddedness in the SSD and SSU was about the same in 2008 and 2012, respectively. Particular note was that the embeddedness in the SSD from 2007 to 2012 was almost zero, which meant there was no coarse or fine sand embedded on the bottom and this represented a significantly lower embeddedness than that in the SSU in 2008 and 2012.Combining the changes in riverbed characteristics with the displacement of the critical spawning site of the Chinese sturgeon, we found that where spawning occurred was in areas with moderate bottom hardness, roughness and embeddedness. We can conclude that the changes in riverbed characteristics have possibly caused the positional changes of the critical spawning sites of Chinese sturgeon. The changes in bottom characteristics of the spawning ground may have also caused a degradation in suitability of the bottom substrate for spawning and consequently may have contributed to the habitat loss of the spawning ground. However, further proof is required in future studies, which will thoroughly evaluate the ecological effects of the erosion by the clean water from the TGR and help for outline the necessary steps to be taken to rehabilitate the spawning ground of the Chinese sturgeon. 参考文献 相似文献 引证文献

Spatial distribution and habitat choice of adult Chinese sturgeon (Acipenser sinensis Gray, 1835) downstream of Gezhouba Dam, Yangtze River, China

Summary Eight hydroacoustic surveys were conducted between 2007 and 2010 to determine the spatial distribution and habitat choice of adult Chinese sturgeon (Acipenser sinensis) within 85 km immediately downstream of Gezhouba Dam, which is the lower-most dam blocking upstream sturgeon migration in the Yangtze River. A potential 32 A. sinensis were identified; depth, velocity, etc., characteristics were determined at the sturgeon site with an Acoustic Doppler Current Profiler. Most targets (26 individuals, 81.3%) were in water >12 m deep, and most (29 individuals, 90.6%) targets were near the river bottom. All targets stayed in or were close to the river channel (distance to the thalweg about one tenth of the river width). Fish were primarily distributed among four separate and deep areas. Variations in the water level played no significant role in fish distribution. Large, deep areas attracted the most fish. A preliminary analysis of environmental factors including water depth, flow velocity, Froude number and Reynolds number indicated that the bedform morphology (deep areas) was probably the key factor determining the A. sinensis habitat preference. Future conservation of the sturgeon will be more effective when special attention is given to the four refuges.

Effect of Release Temperature from Three Gorges Reservoir on the Procreation of Chinese Sturgeons

Chinese sturgeon is the national list endangered fish species. Since the construction of the Gezhouba dam in 1981, the migration of Chinese sturgeon for procreating to upstream of the Yangtze River has been blocked which cause the only spawning ground was left locating in a narrow zone downstream close to the dam site. The procreation of Chinese sturgeons need suitable ecological factors, including temperature, hydrology, sediment and so on, but after impoundment of Three Gorges Reservoir (TGR), the environment have changed a lot that brings a great threaten to the Chinese sturgeons. In this paper, based on previous hydrodynamics and thermal coupled model of TGR, three different scenarios including dry, normal and wet year is simulated to access the influences of release temperature from TGR on procreation of Chinese sturgeons. The result indicates that due to the weak stratification of the TGR, the release temperature changes compared to natural river water temperature, as a result, the time of the procreation is slightly delayed in different scenarios because the release temperature is higher than the upper bound temperature for spawning, of which the days been delayed is about 14 in dry years, 13 in normal years and 5 in wet years, respectively, so temperature becomes a limiting factor to the procreation of Chinese sturgeons.

Natural spawning of Chinese sturgeon during the 175 m tentative impoundment of Three Gorges Dam

The impoundment of the Three Gorges Project (TGP) may influence the natural reproduction of the Chinese sturgeon. From 2009 to 2011, a five-method investigation was conducted to analyse this influence. The Chinese sturgeon reproduced in late November 2009 to 2011, which was about two weeks later than in 2003 to 2006. The water discharge and water temperature did not exhibit any evident difference from 2003 to 2011. The investigation showed that the spawning sites transferred near the Gezhouba dam in 2010 and 2011. The estimated parent Chinese sturgeon greatly increased in 2011, which suggested that stopping the catching of parent fish increased the natural spawning number. The integral survival rate before the fish enters into the sea should be assessed, however. All the monitoring dates from 1997 to 2011 showed that the Chinese sturgeon could finish natural reproduction, while the Three Gorges Dam operated during the 175 m trial impoundment. Yet, spawning time was delayed and water temperature during spawning was slightly higher than before. The increase of spawning size in 2011 showed the number of parent fish has more influence in the reproduction number than the operation of TGP. Earlier impoundment to avoid the spawning time of Chinese sturgeon may be the key to reducing the effect on the natural reproduction of Chinese sturgeon.

Migrations and movements of adult Chinese sturgeon Acipenser sinensis in the Yangtze River, China

From 2006 to 2009, 27 ultrasonic-tagged wild adult Chinese sturgeon Acipenser sinensis [eight males, 19 females; total length (L(T)) range = 245-368 cm] were captured on the spawning ground just downstream of Gezhouba Dam (GZD) in the Yangtze River. Twenty-six individuals were tracked for 7 to 707 days (mean number of relocations = 859; range = 3-4549). Acipenser sinensis movements were divided into four categories: (1) spawning migration, two tagged A. sinensis (one female and one male) returned to the Yangtze River and migrated from the Yangtze Estuary (river kilometer, rkm, 0) to the spawning ground (1678 rkm) between June and October. Their mean upstream ground speed was 1.41 km h(-1) (range = 0.26-2.35 km h(-1) ). The speed of the male was faster than the female; (2) pre-spawning holding, four of five females tagged in November 2008 stayed within 1678.00-1674.15 rkm for c. 1 year before the spawning period; (3) spawning movements, all A. sinensis swam mostly from the tailrace of the GZD (1678 rkm) to the Miaozui (1674.15 rkm) reach and some moved downstream c. 18.21 rkm (range = 3.93-24.64 rkm), but then, returned upstream to the GZD. Most tagged A. sinensis were on the spawning ground on the day when the spawning occurred; (4) post-spawning migration males (n = 6) and females (n = 2) departed the spawning area on a different time schedule, females leaving before males. The mean seaward ground speed of six A. sinensis was 4.87 km h(-1) (range = 0.68-7.60 km h(-1) ). There were no significant differences (P > 0.05) in ground speeds among reaches or between sexes within reaches between telemetry receivers. These broad spatiotemporal scale results will help establish an effective protection strategy for the species in the Yangtze River.

The influence of dam and lakes on the Yangtze River streamflow: long‐range correlation and complexity analyses

AbstractEmploying long‐range correlation, complexity features and clustering, this study investigated the influence of dam and lake‐river systems on the Yangtze River flow. The impact of the Gezhouba Dam and the lake systems on streamflow was evaluated by analysing daily streamflow records at the Cuntan, the Yichang and the Datong station. Results indicated no evident influence of the Gezhouba Dam on streamflow changes. Distinct differences in scaling behaviour, long‐range correlation and clustering of streamflow at the Datong station when compared with those at the Cuntan and Yichang stations undoubtedly showed the influence of water storage and the buffering effect of the lake systems between the Datong station and other two hydrological stations on streamflow in the lower Yangtze River basin. Decreased regularity, enhanced long‐range correlation and increased clustering of streamflow in the lower Yangtze River basin due to the effect of water storage of the lake systems were corroborated. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Applying instream flow incremental method for the spawning habitat protection of Chinese sturgeon (Acipenser sinensis)

AbstractThe Chinese sturgeon, Acipenser sinensis, is an anadromous species that spawns in the Yangtze River and Pearl River of China. Its population has declined dramatically since the construction of the Gezhouba Dam (GD) in 1981 and then with the impoundment of the Three Gorges Dam (TGD) upstream of the GD in 2003. This paper presents a quantitative method based on the instream flow incremental method to explore the relationship between the fish spawning habitat and the operations of the GD and TGD, aiming to find a solution for conservation of the species. A two‐dimensional hydrodynamic model was built with the River2D to simulate the hydraulic behaviour of the stream below the GD. Habitat suitability index was determined by the biological data of the fish collected in the field. The two parts were then integrated through a geographical information system developed via ArcGIS to outline the fish habitat area variation with flows. The decision support system is applied to set up a habitat time series for validating the assumption that more habitats have the potential to support more fish. The fish habitat results for alternative instream flow schemes are then compared with one another for defining the optimal flow requirements and evaluating effects of reservoir operation alternatives in order to improve the operation management for the GD and TGD projects. The results show that the optimal flow for spawning of the fish is about 7000–13000 m3/s and the optimal inlets combination is where the inflow comes from two power plants. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Impact of the Gezhouba and Three Gorges Dams on habitat suitability of carps in the Yangtze River

Summary The Gezhouba Dam and Three Gorges Project are the two largest hydraulic projects in the middle reach of the Yangtze River. Although these projects have yielded benefits to local communities by providing flood control, water supply, and safe navigation, they also have changed the physical habitat of the Yangtze River. As a consequence, aquatic organisms, including rare species and fishes with economic value, have been affected. The Yangtze River’s four major carp species (YFMCS)—black carp (Mylopharyngodon piceus), grass carp (Ctenop haryngodon idellus), silver carp (Hypoph thal michthys molitrix), and big-head carp (Aristichyths nobilis)—have significant importance to the fresh water fishery in China. According to field surveys, the percentage of the YFMCS in the total catch of fish from Tongting Lake has gradually reduced. The percentages were 22%, 14.1%, 11.84%, and 8.5% in 1963, 1980–1982, 1997, and 2002, respectively. These reductions in species population are mainly attributed to the loss of spawning ground caused by dam construction. Considering the spawning characteristics of the YFMCS, a habitat suitability index model (HSI) has been established. A one-dimensional (1-D) mathematical model was also developed to simulate and predict aspects of the physical habitat situation for the YFMCS. By coupling the habitat suitability curves and the 1-D mathematical model, a HSI model for the YFMCS was established. The HSI model was validated by comparing measured data with predictions from the model. These comparisons show that the computed results agree well with the measured results. The HSI model for the YFMCS is used to suggest a minimum instream flow and suitable daily discharge increase during the reproduction season for the carp species. The minimum discharge needed for the YFMCS in the middle reach of the Yangtze River is 3000 m3/s. Different daily discharge increases are required for different initial discharges, too small or too large of an increase in daily discharge is not good for carps spawning. Therefore, adjusting reservoir operations to create reasonable water level fluctuations is a key method to improve the habitat suitability of carps spawning sites.

Assessing spawning ground hydraulic suitability for Chinese sturgeon ( Acipenser sinensis) from horizontal mean vorticity in Yangtze River

The Chinese sturgeon, Acipenser sinensis, is an anadromous protected species. Its migration pattern has been blocked since the construction of Gezhouba dam and the length of the natural spawning site reduced to less than 7 km. However, the fish eventually established an alternative spawning ground in the narrow downstream reach of Gezhouba dam. In this article, we applied Delft3D-Flow model to simulate the hydraulic suitability of the spawning ground downstream Gezhouba dam. Horizontal mean vorticity was used to assess the hydraulic environment of spawning ground. The flow field state was determined through model simulation and field-measured data used to validate the model. The computational method was improved by calculating absolute horizontal mean vorticity from estimates the literature. The final vorticity was determined from the simulation output and its distribution pattern retrieved. The horizontal mean vorticity range was 0.71–4.61 10 −3 s −1 for the entire spawning grounds, with egg mass field upper limit of 1.0 × 10 −3 s −1. Vorticity strength selection of Chinese sturgeon spawning can enhance our understanding of egg fertilization rate, hence the protection of fertilized eggs. Furthermore, the results of the study would add to existing scientific database for spawning ground hydraulic environment protection, especially in the ecological regulation drive of the Three Gorges Reservoir.