Major Chinese Carps Research Articles

Characterization of the flavor profile of four major Chinese carps using HS-SPME-GC–MS combined with ultra-fasted gas chromatography-electronic nose

The four major Chinese carps are highly popular for their distinctive nutritional benefits. However, the differences in flavor among these carps remain unclear. This study investigated the flavor profiles of these carps using headspace solid-phase micro-extraction gas chromatography–mass spectrometry (HS-SPME-GC/MS) combined with ultra-fasted gas chromatography electronic nose (GC E-nose). The four major Chinese carps had high protein content (16.68–18.61 %) and low fat levels (0.42–1.29 %). A total of 45 volatile compounds were identified in these carps. Both the GC E-nose and HS-SPME-GC–MS results consistently showed significant flavor profiles differences among these carps, with Ctenopharyngodon Idella (CI) exhibiting the most pronounced distinctions compared to the other three species. Based on VIP >1 and p < 0.05, 10 key compounds including 2-Nonanone, Cyclodecanol, Eugenol, 1,3-Cyclooctadiene, etc., largely contributed to the distinctive overall flavor profile of four major Chinese carps derived mainly from amino acid and fatty acid metabolism.

Compounding effects of human activities and climatic changes on the river water temperature evolution mechanism for ecological effects

AbstractUnderstanding the drivers and ecological effects of river water temperature (Tw) change remains a complex and challenging task in the field of ecohydrology. We developed the extreme‐point symmetric mode decomposition to quantitatively identify the trend, period and mutation of water temperature (Tw). The sparrow search algorithm‐long short‐term memory model was constructed to reconstruct the historical Tw to quantitatively identify the effects of human activities (HA) and climate change (CC) at different time scales. The random forest method was used to analyse the contribution rates of different meteorological factors and to clarify the main factors. Our results demonstrate that the Tw had a cooling trend in the 1980s, and the other decades have a warming trend, and the annual Tw distribution shows an obvious ‘unimodal’ distribution. The interannual Tw has a short period of 2–3a, 6–12a and a long period of 10–15a. At the interannual scale, as the distance from estuaries decreases, the influence of HA gradually diminishes, and only the great Tw is governed by CC. Contributions from HA and CC to Tw vary at the seasonal and monthly scales due to geographical differences. In Cuntan, the contribution of HA to Tw is greater than that of climatic factors. The contribution rates of climatic and HA in the three regions of Yichang, Hankou and Datong also exhibit their respective characteristics and fluctuation patterns. The maximum temperature is the most important factor affecting the change of Tw. Abnormal Tw changes result in delayed spawning and characteristic reproduction Tw attainment dates for the Four Major Chinese Carps and Acipenser sinensis.

Enhancing ecological success in Yangtze River channel construction: A numerical modelling approach

AbstractChannel constructions significantly impact river hydrodynamics, subsequently influencing river ecosystems. To mitigate the negative influence of channel construction and protect fish habitat, it is essential to evaluate fish habitat suitability through the integration of hydrodynamic and habitat models. This study models channel constructions on both the left and right riverbanks to evaluate habitat suitability for Four Major Chinese Carps and the Chinese sturgeon. Initially, flow velocity, water depth and grain size are simulated, followed by an assessment of habitat conditions using the Habitat Suitability Index (HSI) for three distinct construction strategies. Results reveal that constructing channels on the left bank mitigates adverse effects on fish habitat, while constructions on the right bank and both riverbanks lead to habitat degradation. Long‐term effects on riverbed elevation and fish habitat suitability post‐construction were also investigated. Notably, the Four Major Chinese Carps consistently demonstrate greater suitability for the studied river, regardless of flow rate or construction strategies, in comparison to the Chinese sturgeon. These findings underscore diverse responses to channel construction, providing valuable insights for identifying critical habitat areas for endemic fish conservation. This research presents a robust framework for assessing fish ecology in river systems, offering support for conservation decision‐makers.

Dam‐induced difference of fish habitat distribution in the fluctuating backwater zone of the Three Gorges Dam

AbstractChanges in fish habitat induced by dam construction in the downstream river have been well documented in an increasing body of literature. Fish habitats in the backwater zone of dams have undergone dramatic changes, which have still remained poorly understood. This study aims to provide a more complete understanding of fish habitat distribution and clarify fish habitat utilization patterns in the upstream dam in order to adopt effective remediation activities. This study was conducted in the Three Gorges Dam (TGD) as it is the world's largest installed capacity hydropower station, with a backwater zone length of about 660 km. Four major Chinese carp (FMCC) were selected as target fish species, and fish habitat distribution upstream of TGD was assessed by integrating the swimming ability and environmental preference of different fish species into their critical life stages. Assessment results at different life stages of the target fish species showed that June was a critical period for spawning activities FMCC in the fluctuating backwater zone of TGD. The riverbank was an important feeding habitat for FMCC, and the high‐velocity flow in the centre of the channel exceeded the limits of the swimming ability of target fish. The fish habitat distribution in the fluctuating backwater zone of TGD was heavily affected by runoff from April to September and by dam operation from October to March of the next year. This work provide valuable information about river conservation and management in the upstream of TGD.

Numerical Simulation of Habitat Restoration for Floating Fish Eggs in the Upper Yangtze River Tributaries

The upper reaches of the Yangtze River not only serve as a crucial waterway in China’s southwestern region but also function as a conservation area for rare fish species. Recognizing the tendency of current navigation channel improvement projects to overlook the impact on aquatic habitats and the limitations of existing habitat assessment systems, this study specifically focuses on the bifurcation section of the upper Yangtze River. To address these issues, a two-dimensional mathematical model is established to simulate and validate various improvement schemes. An analysis of the flow conditions necessary for fish migration and spawning in this section is conducted, determining optimal flow rates and water levels during spawning and migration periods. A suitability assessment system for spawning and migration is then established, utilizing the four major Chinese carps as representative fish species for evaluation. Through a comprehensive analysis of the results, rational improvement schemes are identified. The findings underscore the importance of considering elevation of dam crest during the construction of sub-dams to regulate the navigation channel, particularly regarding its impact on fish habitats during the dry season. In this plan, the weighted available area of the spawning ground increased by 189,251 m2, 165,860 m2, 89,527 m2, 66,542 m2, and 47,182 m2 under five conditions. Additionally, the evaluation indexes PPA, HFI, and CQI showed increases of 5.011%, 4.176%, and 2.901%, respectively. Moreover, this study refines fish habitats based on their reproductive and living habits, thereby enhancing existing habitat assessment models.

Aquaculture activities influencing the generation of geosmin and 2-methylisoborneol: a case study in the aquaculture regions of Hongze Lake, China.

Contamination by odor substances such as geosmin (GSM) and 2-methylisoborneol (2-MIB) was examined in the cultured water from aquaculture farming in the region of the Hongze Lake in 2022, and some factors influencing residual levels of them in the water were analyzed. Geographically, high concentrations of GSM were located mainly in the north and northeast culture areas of the lake, while those of 2-MIB were found in the northeast and southwest. Analysis of the water in the enclosure culture revealed significant differences in the concentrations of GSM and 2-MIB among the cultured species. The mean concentrations of GSM in culture water were ranked in the order: crab > the four major Chinese carps > silver and bighead carp, and silver and bighead carp > crab > the four major Chinese carps for 2-MIB. The concentration of GSM was significantly higher at 38.99 ± 18.93 ng/L in crab culture water compared to other fish culture water. Significant differences were observed in GSM concentrations between crab enclosure culture and pond culture, while 2-MIB levels were comparable. These findings suggest that cultural management practices significantly affect the generation of odor substances. The taste and odor (T&O) assessment revealed that the residual levels of GSM and 2-MIB in most samples were below the odor threshold concentrations (OTCs), although high levels of GSM and 2-MIB in all water bodies were at 30.9% and 27.5%, respectively. Compared with the corresponding data from other places and the regulation guidelines of Japan, USA, and China, the region in the Hongze Lake is generally classified as a slightly T&O area, capable of supporting the aquaculture production scale.

Optimizing flow regime for the Four Major Chinese Carps by integrating habitat suitability within reservoir operation

The construction of dams has brought many benefits to human society. However, it has also altered the natural hydrological regime, affected aquatic organisms’ habitat conditions and decreased important fishery resources. In the post-dam construction era, it has become crucial to evaluate the ecological flow requirements for all stages of fish life and ensure the provision of dynamic flow pulsation, particularly during the spawning stage. Here, we proposed a Reservoir Operation Model for Fish Habitat across Life Stages (ROM-FHLS) to reconcile the apparent contradiction between fish habitat preservation and hydropower generation in the Yangtze River Basin. Compared with the conventional outflow conditions, our model demonstrated significant improvements in power generation and suitable habitat area during the migration, spawning and incubation, and juvenile periods. Specifically, we observed average increases of 15.2%, 13.1%, and 6.7% in power generation, and enhancements of 16.5%, 17.3%, and 1.8% in suitable habitat area, respectively. Our approach advocates for the comprehensive protection of fish throughout their entire life cycle while highlighting the feasibility of enhancing fish habitats without compromising power generation. Furthermore, we proposed an outflow scheme that incorporates pulsation patterns into reservoir operations to effectively stimulate fish spawning activities. This study presents a fresh perspective on comprehending the intricate interplay among dam-controlled hydrological processes, river hydrodynamic environment, and fish behavior. The findings have the potential to enhance fish spontaneous reproduction and aid in the recovery of aquatic populations in large dammed rivers.

Effects of short-term water velocity stimulation on the biochemical and transcriptional responses of grass carp (Ctenopharyngodon idellus).

Since 2011, ecological operation trials of the Three Gorges Reservoir (TGR) have been continuously conducted to improve the spawning quantity of the four major Chinese carp species below the Gezhouba Dam. In particular, exploring the effects of short-term water velocity stimulation on ovarian development in grass carp (Ctenopharyngodon idellus) is essential to understand the response of natural reproduction to ecological flows. We performed ovary histology analysis and biochemical assays among individuals with or without stimulation by running water. Although there were no obvious effects on the ovarian development characteristics of grass carp under short-term water velocity stimulation, estradiol, progesterone, follicle-stimulating hormone (FSH), and triiodothyronine (T3) concentrations were elevated. Then, we further explored the ovarian development of grass carp under short-term water velocity stimulation by RNA sequencing of ovarian tissues. In total, 221 and 741 genes were up- or downregulated under short-term water velocity stimulation, respectively, compared to the control group. The majority of differentially expressed genes (DEGs) were enriched in pathways including ABC transporters, cytokine-cytokine receptor interaction, ECM-receptor interaction, and steroid hormone biosynthesis. Important genes including gpr4, vtg1, C-type lectin, hsd17b1, cyp19a1a, cyp17a1, and rdh12 that are involved in ovarian development were regulated. Our results provide new insights and reveal potential regulatory genes and pathways involved in the ovarian development of grass carp under short-term water velocity stimulation, which may be beneficial when devising further ecological regulation strategies.

Identification and restoration of hydrological processes alteration during the fish spawning period

The hydrological processes play an important role in stimulating fish spawning behavior. Changes in the natural hydrological processes will alter the populations and distribution of fish, which may have a negative impact on the native aquatic organisms. The aim of this study is to identify the alteration of the water rising process during the fish spawning period and to construct an ecological flow optimization model to restore the water rising conditions for fish reproduction. The Mann–Kendall test and the sliding t-test were used to detect the mutation year of the mean daily flow data sets in the fish spawning period in each monitoring year. Then the data sets can be divided into pre-altered and post-altered periods. The water rising process was characterized by the water rising processes count, the duration, the daily flow increase rate, the date of the water rising process, and the initial water rising flow. The changes in hydrological processes in the middle reaches of the Yangtze River were investigated by comparing the post-altered and pre-altered characteristic parameters. Furthermore, we integrated the statistical values of the five characteristic parameters in pre-altered into an ecological flow optimization model to simulate the natural water rising processes for the spawning of the Four Major Chinese Carps (FMCC) and Chinese Sturgeon (CS). The analysis showed that after the hydrological mutation year, the duration and the initial water rising flow in the FMCC spawning season were increased, with hydrological alteration degrees of 63.10% and 70.16%, respectively; however, the daily flow increase rate was significantly decreased, with hydrological alteration of 86.50%. During the CS spawning season, the water rising processes count and the initial water rising flow were dramatically altered parameters, with hydrological alteration degrees of 50.86% and 83.27%, respectively. The former parameter increased, but the latter decreased significantly in the post-altered period. To induce the spawning activity of FMCC and CS, appropriate ecological flows and hydrological parameters were proposed. These results showed that during the spawning seasons of FMCC and CS, the hydrological processes of the middle reaches of the Yangtze River changed significantly. Therefore, ecological flow must be ensured through ecological operation of upstream reservoirs to provide suitable spawning conditions in target fish spawning grounds.

Balancing economic and ecological benefits for hydro-junction operation based on the ecological flow from the four major Chinese carps: a case study from Xinjiang River, China

The construction and utilization of the hydro-junctions would change the water flow and affect the hydrologic process required for the survival and reproduction of the aquatic organism in the river basin. To investigate the influence of the construction of the Jiepai (JP) and Bazizui hydro-junction (BZZ) on the hydrologic process in the Xinjiang River and coordinate the benefits between power generation and downstream ecological protection of the four major Chinese carps (FMCC), a one-dimensional hydrodynamic model is established to simulate the river hydrological regime of the spawning site before and after the construction of BZZ. Meanwhile, eleven ecological hydrologic parameters are used to evaluate the degree of hydrological changes for the spawning site caused by JP and BZZ, and four hydrological methods are applied to calculate the minimal and optimal ecological flows to satisfy the demands of FMCC. The multi-objective operation model combined with the non-dominated sorting genetic algorithm II(NSGA-II) is established to evaluate the relationship among the objective functions and design the ecological operation scheme of BZZ. The results indicate that the hydrologic changes in the spawning site has been moderately changed since the construction of the JP and would change more after the construction of BZZ. An obvious antagonistic relationship between electricity generating and ecological changes are presented in the simulation results, and the multiobjective operation model could clearly increase the comprehensive benefits under three typical years (dry, average, and abundant) by 20%, 19%, and 34% with the corresponding electricity generating lost by 4.9%, 3.5%, and 4.1%, respectively. This study is expected to provide scientific guidance to coordinate the restrictions and conflicts between economic and ecological benefits of hydro-junction operation in the lower reaches of the Xinjiang River.

Determination of suitable ecological flow regimes for spawning of four major Chinese carps: A case study of the Hongshui River, China

Due to the construction and operation of cascade reservoirs in Hongshui River (HSR), most natural fish spawning grounds have been destroyed, thus causing ecological-economic impacts on local riverine ecosystems and fisheries. An effective way to restore spawning habitats and fulfill their spawning requirements is to generate an appropriate ecological flow regime. With a focus on the existing spawning ground of Dingzi Beach (DZB) for four major Chinese carps (FMCC) in HSR, this study built a one- and two-dimensional (1D and 2D)-coupled and fuzzy logic-based fish habitat model to estimate a suitable ecological flow to ensure the existence of continuous and connected habitats. In addition, critical indicators and timing to trigger spawning behaviors were quantified given the requirements for water temperature and high-flow pulses. Thus, suitable ecological flow regimes during the spawning period of FMCC in HSR were established based on the notion of thresholds of flow discharge. The ecological flow between 2,500 and 11,000 m3/s from April to July at DZB was found to be maintained. Three high-flow pulses characterized with different thresholds of flow indicators were recommended to be generated to meet the requirements of the FMCC spawning either in the second half of May, June, or July. Results of this study can provide the basis for sustainably managing cascade reservoirs as well as establishing a suitable ecological flow regime to protect the reproduction of FMCC in HSR.

Quantitative assessment methodology framework of the impact of global climate change on the aquatic habitat of warm-water fish species in rivers

Global climate change (GCC), with global warming as the main characteristic, has become a global issue widely concerned by people. GCC impacts the hydrological regime at the watershed scale and affects the hydrodynamic force and the habitat conditions of freshwater ecosystems at the river scale. The impact of GCC on water resources and the water cycle is a research hotspot. However, there are few studies on water environment ecology related to hydrology and the influence of changes in discharge and water temperature on warm-water fish habitats. This study proposes a quantitative assessment methodology framework for predicting and analyzing the impact of GCC on the warm-water fish habitat. This system integrates GCC, downscaling, hydrological, hydrodynamic, water temperature and habitat models and was applied to the middle and lower reaches of the Hanjiang River (MLHR), where there are four major Chinese carps resource reduction problems. The results showed that the calibration and validation of the statistical downscaling model (SDSM) and the hydrological, hydrodynamic, and water temperature models were carried out using the observed meteorological factors, discharge, water level, flow velocity and water temperature data. The change rule of the simulated value was in good agreement with the observed value, and the models and methods used in the quantitative assessment methodology framework were applicable and accurate. The rise of water temperature caused by GCC will ease the problem of low-temperature water in the MLHR, and the weighted usable area (WUA) for spawning of the four major Chinese carps will appear in advance. Meanwhile, the increase in future annual discharge will play a positive role in WUA. In general, the rise in confluence discharge and water temperature caused by GCC will increase WUA, which is beneficial to the spawning ground of four major Chinese carps.

Settling and transport properties of grass carp and silver carp eggs in the water-hardened phase: Implications for resource protection and invasion control during early life period

Grass carp and silver carp eggs have no swimming ability in the water-hardened phase and need to drift for tens or even hundreds of hours before complete incubation. A full comprehensive understanding of the settling and transport properties of eggs is crucial for the resource protection and invasion control of Four Major Chinese Carps (FMCCs) during their early life stages. Artificial eggs have been used extensively in previous field and flume experiments; however, our understanding of the settling and transport properties of real eggs in the water-hardened phase remains limited. In the present study, a series of column and flume experiments were conducted in stagnant and moving water, respectively. In light of the differences in settling characteristics, caution should be exercised when applying research results obtained from artificial eggs having the closest diameter and specific gravity as real eggs. Compared with grass carp and silver carp eggs in the water-hardening phase, egg diameters in the water-hardened phase were 36% and 33% greater, respectively, and egg hydrostatic settling velocities were 31% and 40% lower, respectively. Significant interspecific differences between the two species exist in terms of egg size and hydrostatic settling velocity. Based on linear mixed effects analysis of dominant transport trajectories and regression analysis between suspending rate and flow velocity, 0.30 m/s can be considered as critical drifting velocity in uniform flow. Adaptive management schemes are discussed to promote resource protection and invasion control of FMCCs during the early life stages. The results of the present study enhance our understanding of drifting egg movement and provide insights that could facilitate the comprehensive management of FMCCs.

Methods on quantifying ecological operation target based on bio-hydrological response model for stimulating the reproduction of four major Chinese carps in the Three Gorges Reservoir

Methods on quantifying ecological operation target based on bio-hydrological response model for stimulating the reproduction of four major Chinese carps in the Three Gorges Reservoir

Variation of heat flux and its effect on the reproduction of four major Chinese carp

Abstract River heat flux (HF) regime has been significantly affected by anthropogenic activities and climate variation, and it is of great significance to deeply explore intrinsic driving mechanisms and ecological effects. This study uses the middle reaches of the Yangtze River as its research area and, by constructing the wavelet model and the IHA-RVA model, quantifies the evolution mechanism and internal law of ‘flow- water temperature (WT) – HF’ over the past four decades and investigates the effects of Three Gorges Dam on the ecological reproduction of ‘four major Chinese carp’. The results show that, (1) flow and WT have three change cycle scales; the overall hydrologic variations of flow and WT were 64% and 62%, respectively, close to high variation. (2) The overall HF shows a decreasing trend from 1983 to 2019, with significant changes in HF in spring and winter regulated by the Three Gorges Reservoir; the basin flow-WT-HF relationships exhibit a hysteretic pattern, with the maximum WT occurring one month after the peak HF and flow. (3) The ‘four major Chinese carp’ natural breeding season is closely related to the time when the WT reaches 18 °C; HF is a vital habitat factor that influences fish spawning and reproduction.

Identifying priority areas of Four Major Chinese carps’ species in the Pearl River basin based on the MaxEnt model

The Pearl River basin (PRB) is an important producing area and the gene pool of wild resources of Four Major Chinese carps (FMCC). However human activities and climate changes causes the area shrink of the river network in PRB, the pollution aggregation, the serious habitat destroy of aquatic organisms, and the threat of biological resources and their living environment. Based on the accurate location and distribution data of FMCC from the literature and the field survey report of 2015–2016, this study used the MaxEnt model to predict the hot spot distribution area of FMCC in PRB. The simulation results show that the distribution of FMCC in the PRB gradually increases from the upper reaches to the middle and lower reaches. According to the MaxEnt model, the hot spots of FMCC in the PRB are mainly distributed in the south reaches and the lower reaches of the southeast. The model simulation also demonstrates that the hottest spots for the distribution of FMCC species in the PRB are the Yujiang basin, the Qianjiang basin and the lower reaches of the Xijiang basin. This study can provide the scientific guidance for the protection and the restoration of FMCC species in the PRB.

Ecological responses of spawning habitat suitability to changes in flow and thermal regimes influenced by hydropower operation

AbstractLarge reservoirs and dams can fundamentally alter downstream flow and thermal regimes by resetting the flow and water temperature release boundary conditions, resulting in significant impacts on fish habitat suitability. Therefore, it is critically important to understand how the volume and temperature of dam releases to influence downstream hydraulic and temperature dynamics and predict the ecological responses of fish habitat suitability to these changes. In this study, a physically based coupled model framework was developed to identify the temporal and spatial variations of hydraulic and water temperature regimes and the spawning habitat suitability of four major Chinese carps (FMCC) in the middle reach of the Yangtze River below Three Gorges Reservoir (TGR) responded to different upstream boundary conditions established by dam operation. The results showed that the dam discharge volume from TGR mainly affected the downstream hydraulic regime, while dam discharge temperature would have most impact on downstream water temperature. The spawning habitat suitability of FMCC obviously decreased due to TGR operation, and the declined water temperature suitability and the delayed and narrowed window of suitable water temperature were the main influencing factors. For the purpose of maximizing the spawning habitat suitability of FMCC in the downstream reaches below TGR, dam discharge volume ranged from 10,000 to 22,500 m3/s, and dam discharge temperature varied from 22 to 23.5°C would be recommended as the outflow conditions in the ecological operation of TGR.

Study on the spawning habitat suitability of four major Chinese carps in the fluctuating backwater area of the Three Gorges Reservoir

The upstream of the Yangtze River has abundant fish resources and is home to the four major Chinese carps (FMCCs), which are economically important fish in the Yangtze River that reside in the fluctuating backwater area (FBA) of the Three Gorges Reservoir (TGR). Their spawning habitat has been influenced by the Three Gorges Dam (TGD) operations. This study investigated the effects of dam operation on spawning habitat suitability and the potential spawning sites of FMCCs, using a physical habitat suitability model combined with a two-dimensional (2D) hydrodynamic numerical model. The habitat model was verified by field measurements of the fish egg density in the FBA, illustrating the capability of predicting the spawning availability of FMCC by comparing the habitat suitability index (HSI) distribution and the weighted usable area (WUA) with the simulation scenarios before and after the TGD construction. The habitat model was then applied to evaluate the effects of TGD operation on spawning habitat suitability and potential spawning grounds in the FBA. These results implied that the TGD operation had negative effects on spawning habitat suitability and produced temporal changes in the available WUA in the FBA. The predictions revealed that impoundment of the TGD decreased the suitability of the hydrodynamic factors. The main spawning period was delayed from April to May, and the variation in the water level induced by the reservoir operation scheme was likely the main factor. The HSI distribution in the FBA showed that the potential spawning grounds decreased to one site located in the Mudong-Luoqi River section. Furthermore, there was a rapid reduction in WUAs, accounting for approximately 18% of that seen in 2001 (before the TGD operation). The results of this study can aid in the management of the spawning grounds of FMCCs in the TGR and provide efficient methods for improving spawning habitat suitability, such as adjusting the pool level of the TGD during the falling stage.

Ecological risk assessment on the habitats of typical aquatic species in the middle reach of the Yangtze River: Implication for three gorges reservoir operation

The operation of a reservoir may change natural hydrological processes, thus affecting the habitat of aquatic organisms. However, the risks posed by reservoirs on aquatic organisms remain to be fully evaluated. In this study, a risk assessment model was established to assess the ecological risk of reservoir flow regulation based on the consequences of deviating from the environmental flow range of an aquatic habitat. We applied this model to the Three Gorges Reservoir by obtaining the risk time series of different aquatic habitats in the Yangtze River before and after the construction of the reservoir. The risk analysis results showed that when habitat discharge is above or below the appropriate range of environmental flows, the ecological risk increases. The Chinese sturgeon, four major Chinese carp species, and finless porpoise habitats were identified to be at low-flow risk, low-flow risk, and high-flow risk, respectively. We suggest that the habitat flows of Chinese sturgeon, four major Chinese carp species, and finless porpoise during the spawning period should not be less than 6,850, 7,000, and 13,500 m3/s, respectively. The results of this study could help river managers optimize reservoir operations to minimize risks and maximize ecological benefits.

Simulating Ecological Effects of a Waterway Project in the Middle Reaches of the Yangtze River Based on Hydraulic Indicators on the Spawning Habitats of Four Major Chinese Carp Species

The adaptability of fish to their habitats is closely related to river hydraulics. While navigation channel projects aim to improve the navigation conditions by adjusting the hydrodynamic force of local river sections, the impacts of these projects on the hydraulic indicators of habitats of the four major Chinese carp species (FMCCs) remain unclear. Taking the Daijiazhou reach in the middle reaches of the Yangtze River as a case study, a mathematical model for spawning suitability was established to simulate changes in these hydraulic indicators before and after the implementation of a navigation channel project. The optimal flow rate interval for the spawning of the FMCCs was 17,500–22,000 m3·s−1. After the navigation channel project was implemented, the habitat suitability index (HSI) and weighted useable area (WUA) increased across the spawning habitats of all FMCCs, indicating that the project implementation created more habitat space. The central bar (Chihugang central bar) became exposed during the dry season, with the HSI and WUA decreasing under low water flow but increasing under medium-low or higher water flow levels. At the Daijiazhou bar head floodplain, which remained unexposed during the dry season, the HSI and WUA increased after project implementation, providing more space for spawning and habitation for the FMCCs. For the low point bar with bank gullies (Lejiawan point bar), the implementation of the bar protection zone project restricted gully development, with the HSI and WUA decreasing for all FMCCs. Based on the above impacts of navigation channel projects on the hydrodynamic environment of fish habitats, this paper provides a reference for the optimization of navigation channel arrangement as well as for the restoration of fish habitats.