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Article

Diversity Patterns and Environmental Drivers of Bivalve Communities in the Caizi Lake Group and Its Major Tributaries During the Initial Post-Fishing Ban Period

by
Chao Jiang
1,
Min Jiang
2,
Chenliang Ren
3,
Xiaoke Zhang
4,
Bowen Li
4 and
Kai Liu
1,2,3,*
1
Wuxi Fisheries College, Nanjing Agricultural University, Wuxi 214081, China
2
Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture and Rural Affairs, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi 214081, China
3
School of Ecology and Environment, Anhui Normal University, Wuhu 241000, China
4
Engineering Technology Research Center for Aquatic Organism Conservation and Water Ecosystem Restoration in University of Anhui Province, School of Life Sciences, Anqing Normal University, Anqing 246133, China
*
Author to whom correspondence should be addressed.
Diversity 2025, 17(11), 773; https://doi.org/10.3390/d17110773
Submission received: 28 September 2025 / Revised: 30 October 2025 / Accepted: 31 October 2025 / Published: 3 November 2025
(This article belongs to the Special Issue Ecology and Conservation of Freshwater Bivalves)
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Abstract

To characterize freshwater bivalve communities and their environmental drivers in the Caizi Lake water system following the 10-year fishing ban in Yangtze River, this study three rounds of standardized surveys across hydrological periods in 2024—May (normal-water), September (high-water), and November (low-water). The results recorded 22 freshwater bivalve species belonging to 15 genera and 4 families. Notably, Ptychorhynchus pfisteri and the second-class national key protected wild animals in China, Lamprotula leaii and Uninovaculina chinensis, were first recorded in the Caizi Lake water system. Community composition was partitioned into three subgroups: Group I—Dasha River, Guache River, Longmian River, and Kongcheng River; Group II—the lake area; and Group III—Chang River. Biomass, density, and dominant species exhibited pronounced spatial heterogeneity, and the assemblage reflected a state of moderate disturbance. Redundancy analysis indicated that the variables that contribute significantly to species richness in sequence are the bitterling and suitable host fish, phytoplankton, and zooplankton. The research results reveal for the first time the population status and distribution patterns of bivalve resources in the Caizi Lake water system following the fishing ban. They not only provide a decision-making basis for the conservation and protection management of bivalve resources in the Caizi Lake water system but also offer data support for the assessment of the fishing ban effect and the evaluation of biological integrity in key waters of Anhui Province.

1. Introduction

Freshwater bivalves are integral components of aquatic ecosystems. They mediate material cycling and energy flow, and they play key roles in water purification, ecological restoration, and environmental monitoring [1,2,3,4]. As filter feeders, bivalves increase water transparency by removing suspended particulates and contribute to nutrient dynamics; their burrowing promotes sediment oxidation, enhances microbial activity, and sustains benthic food webs [5]. In addition, most freshwater bivalves have complex life cycles that depend on host fishes, and they serve as obligatory incubation substrates for embryos of bitterlings (Subfamily Acheilognathinae) during the spawning season; consequently, their population dynamics are closely linked with fish assemblages [6].
Against the backdrop of global biodiversity loss, freshwater bivalves have become one of the most threatened faunal groups. At the catchment scale, hydrogeomorphic features, hydrological regimes, and human activities shape invertebrate distribution patterns to varying degrees [7,8]. Environmental drivers can also regulate physiological processes and life-history events, thereby determining survival, growth, and dispersal potential, which ultimately manifests in species’ geographic distributions [9]. In recent decades, pollution in inland waters (lakes and rivers), altered flow regimes, increasing frequency of extreme climatic events, and anthropogenic disturbances such as channel dredging and dam construction have led to rapid habitat degradation for bivalves; many rare taxa have become increasingly scarce or even verge on extinction [10,11,12,13,14,15]. Historical data indicate that over 20% of China’s freshwater bivalves are threatened, with several species listed as Endangered or Near Threatened [16,17]. The Yangtze River Basin—recognized as a global hotspot of freshwater biodiversity—once harbored abundant bivalve resources [18,19], but faces severe pressures from human activities and recurrent extreme weather, and its bivalve resources show a marked declining trend [13,14,20]. In light of the ongoing erosion of bivalve biodiversity, there is an urgent need for effective measures to conserve and manage freshwater bivalve natural resources and their diversity.
The ten-year fishing ban on the Yangtze River came into effect on 1 January 2020, covering the main stream of the Yangtze River, important tributaries and large lakes connected to the river. It aims to restore aquatic biological resources and ecosystem functions by prohibiting productive fishing. The Caizi Lake Group, composed of Baitu Lake, Xizi Lake and Caizi Lake, is one of the representative shallow lakes in the middle and lower reaches of the Yangtze River. It is located on the southeast side of the Dabie Mountains and the north bank of the Yangtze River in Anqing. Since the completion of the Zongyang Gate in 1959, the Cai Zi Lake group has transitioned from a lake connected to the Yangtze River to a semi-closed lake regulated by a control gate. In 2023, a newly constructed 680 m vertical two-way fishway was installed at the Zongyang Weir on the Changhe River, part of the Caizi Lake branch of the leading water project from the Yangtze River to the Huaihe River, to facilitate the bidirectional migration of fish between the river and the lake, thereby restoring hydrological connectivity and ecological passage between the Yangtze River and Caizi Lake [21]. In 2003, the World Wide Fund for Nature (WWF) assessed Poyang Lake, Dongting Lake, and Shengjin Lake and the lakes of the Anqing Yangtze River Wetland Nature Reserve, including the Caizi Lake Group, as the three most ecologically significant wetland areas in the middle and lower reaches of the Yangtze River [22]. In addition, the Caizi Lake complex serves as a critical stopover and wintering habitat for waterbirds migrating along the East Asia-Australia Flyway. After the trial operation of the Caizi Lake Line of the Yangtze River to the Huaihe River Water Diversion Project began on 16 September 2023, in order to reduce the impact of shipping on the Caizi Lake wetland and migratory birds, navigation was prohibited in the waterways of the lake area during the wintering period of winter migratory birds. To protect the fishery resources in the Yangtze River Basin, a complete fishing ban has been implemented in the Caizi Lake Group since 2021. Historical data show that the investigation of bivalve species in the Caizi Lake Group can be traced back to 1982 at the earliest. Only eight species were recorded in the early stage, mainly Corbicula fluminea [23]. By 2020, a total of 22 species had been recorded [24,25,26,27,28]. Overall, the historical research on bivalves in this area is limited, and there is a lack of systematic investigation of the main tributaries. The environmental driving factors of the distribution pattern of bivalves have not been explored either. Therefore, the support provided for the conservation and protection management of bivalve resources in the Caizi Lake water system is still insufficient.
This study takes the Caizi Lake Group and its major tributaries as the research area. From May to December 2024, a freshwater bivalve resource survey was conducted. Through standardized sampling and data analysis systems, the diversity pattern of bivalve communities in the Caizi Lake Group and its five major tributaries during the initial stage of the ten-year fishing ban was analyzed. Combined with historical data, the impact of the fishing ban policy on the community structure was explored. And we explore the correlation between biological and abiotic factors and the distribution pattern of freshwater bivalve resources. This study fills the gap in the ecological research of bivalves in the Caizi Lake water system after the fishing ban based on previous studies. It not only provides a scientific basis for the protection of bivalve resources in the Caizi Lake water system but also offers data support for the ecological effect assessment of the fishing ban policy in the Yangtze River Basin.

2. Materials and Methods

2.1. Collection of Bivalve

Based on the hydrological conditions and geographical characteristics of the Caizi Lake water system, a total of 129 quadrat plots (each measuring 50 m2) were systematically distributed across the three lake subbasins of the Caizi Lake Group and its five major tributaries to ensure comprehensive coverage of the entire aquatic system (Figure 1). Among them, 3 quadrat areas with 32 quadrat plots were set up in Baitu Lake (BT), 3 quadrat areas with 36 quadrat plots were set up in Caizi Lake (CZ), and 3 quadrat areas with 24 quadrat plots were set up in Xizi Lake (XZ). Five quadrat plots are set for Kongcheng River (KC), six each for Longmian River (LM), Guache River (GC), and Chang River (CR), and a total of 14 quadrat plots are set for Dasha River (DS) and its branches. Surveys were conducted three times during 2024 to capture contrasting hydrological periods: May (normal-water), September (high-water), and November (low-water). Combining qualitative and quantitative sampling methods, samples were collected through trawling nets (0.5 × 0.5 m), hand-held clam harrows (width: 0.5 m), and manual picking. The sampling time, longitude and latitude of each sample were recorded. After the samples were washed, they were numbered, classified, measured and counted [29,30,31].
This research team holds a valid fishing license (No. 00002582161). All collected live protected species were documented with photographs, while the remaining specimens are preserved in the Germplasm Resource Bank of the Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences. The entire experiment strictly adhered to the operational guidelines set by the Animal Ethics Committee of the Freshwater Fisheries Research Center, ensuring compliance with research ethics and biodiversity conservation requirements.

2.2. Measurement of Environmental Parameters

When collecting bivalve samples, the substrate types were classified as clay, silt, sediment, hard mud, sandy, gravel and stony. Meanwhile, the water temperature (T), pH, dissolved oxygen (DO), electrical conductivity (Cond) and turbidity (Tur) were measured on-site using a portable multi-parameter water quality analyzer (HACH, Loveland, CO, USA). Measure the water depth (WD) using a portable depth sounder (HACH, Loveland, CO, USA). The water transparency (SD) was measured using the Secchi disk (JuKai, Weifang, China).
In addition, biotic covariates from our 2024 aquatic resource monitoring in the Caizi Lake water system were incorporated to assess correlations between biological factors and bivalve distribution. Fish assemblages were surveyed in each lake subarea using two three-panel gillnets (length 200 m, height 2 m; mesh sizes 2, 6, 10, and 14 cm) and three fixed tandem pot traps (total length 18 m; width 45 cm; height 33 cm; mesh size 0.8 cm), each gear set for 12 h. Upon retrieval, all fishes were identified in the field, and catch numbers and biomass by species were recorded. Zooplankton and Phytoplankton sampling followed standard methods for freshwater plankton studies [32]. Taxonomic identifications were based on established keys [33,34,35,36,37,38], and then the density and biomass were calculated according to Zhang & Huang [32].

2.3. Data Analysis

2.3.1. Advantage Status

Species dominance was evaluated using the Index of Relative Importance (IRI) [39], which integrates relative abundance, biomass, and frequency of occurrence to avoid bias from any single metric. Classification thresholds were dominant (IRI > 1000), important (100–1000), common (10–100), occasional (1–10), and rare (<1).

2.3.2. Diversity Index Analysis

Based on species counts and individual abundances in each sampling area, we calculated the Shannon–Wiener diversity index (H′) to characterize species diversity [40], the Margalef richness index (C) to assess species richness [41], and the Pielou evenness index (D) to quantify distributional evenness among species [42]. Together, these indices describe the community-level diversity characteristics of freshwater bivalves across sites.

2.3.3. Cluster Analysis and NMDS Analysis

Similarity clustering analysis of large benthic animal communities based on Bray–Curtis distance was conducted using PRIMER6 [43], and non-metric multi-dimensional scaling (NMDS) analysis was carried out. The Stress coefficient (Stress) is used to determine the validity of the grouping. Among them, when 0.1 < Stress < 0.2, it indicates that the grouping results have certain explanatory significance. When 0.05 < Stress < 0.1, it indicates that the grouping results are basically reliable. When Stress < 0.05, it indicates that the grouping results are well representative [44].

2.3.4. ABC Curve

We applied the Abundance–Biomass Comparison (ABC) method to diagnose disturbance to community structure [45], using the W-statistic as the summary metric [46]. When the biomass dominance curve lies above the abundance dominance curve, W is positive, indicating an undisturbed community; when the abundance curve exceeds the biomass curve, W is negative, indicating severe disturbance; values of W approaching 0, where the curves intersect, indicate moderate disturbance.

2.3.5. Correlation Analysis of Environmental Factors

The correlation heat map was drawn using Origin 2024 to illustrate the relationship between bivalve communities and environmental drivers. The gradient analysis of species richness and environmental drivers was further conducted using Canoco 5. De-trend correspondence analysis (DCA) was conducted on the sample size. Based on the lengths of each sorting axis in the analysis results, it was determined whether to adopt a linear or nonlinear model (gradient length > 4, it is nonlinear; 3 < gradient length < 4, both linear and nonlinear are acceptable; If the gradient length is less than 3, it is linear. The length of the sorting axis in this study is 2.36, and Redundancy analysis (RDA) is selected. The difference was significant when p < 0.05 [47].

3. Results

3.1. Species Composition and Spatiotemporal Pattern

A total of 22 species of freshwater bivalves belonging to 4 families and 15 genera were collected during the survey, of which 18 species, accounting for 81.82%, were collected alive. Ptychorhynchus pfisteri, Lanceolaria lanceolata, Schistodesmus lampreyanus, Lanceolaria eucylindrica were collected only from dead individuals. In this investigation, Ptychorhynchus pfisteri, Lamprotula leaii and Uninovaculina chinensis, two species of national second-class key protected wild animals, were discovered for the first time in the Caizi Lake water system (Figure 2). Corbicula fluminea dominates in the bivalve community structure of the Caizi Lake water system (Table 1), with a quantity proportion of 43.34%.
According to the List of National Key Protected Wild Animals (2021) [48], Uninovaculina chinensis and Lamprotula leaii are listed as second-class national key protected wild animals. According to the IUCN [14], Ptychorhynchus pfisteri was listed as a Near threatened species in 2020. Referring to the research results of Shu [20] and Liu [13], there were 6 species and 3 species, respectively, at the threatened level, and in addition, there were 4 species and 3 species, respectively, in the near-threatened state (Table 2).
The results of the spatiotemporal pattern analysis show that (Figure 3), in terms of different water periods, the differences in the types of bivalves collected in the three water periods are relatively small. Both the normal-water period and the low-water period collected 19 species, while the high-water period collected the most, with 20 species, and the proportion of species richness was 48.39%. Regarding the lake area and its tributaries, 19 species were collected from both habitats, with 15 species shared between them. Each habitat possessed its own endemic species. The dominant species in the lake area were Cristaria plicata and Corbicula fluminea, while only Corbicula fluminea was identified as the dominant species in the tributaries (Table 1).

3.2. Standing Crop and Spatiotemporal Pattern

Combined for all surveyed waters, the average density was 0.030 ± 0.001 ind./m2, with Corbicula fluminea, Parvasolenaia rivularis and Sinosolenaia oleivora contributing more to the density. The average biomass was 1.385 ± 0.020 g/m2, with Cristaria plicata and Lamprotula caveata contributing more to the biomass.
For the overall comparison analysis of the lake area and its tributaries, the average density and biomass of the lake area were 0.010 ± 0.000 ind./m2 and 1.517 ± 0.031 g/m2, respectively; and those of the tributaries were 0.082 ± 0.005 ind./m2 and 1.057 ± 0.005 g/m2, respectively. In the comparison of resource density between the lake area and the tributaries, the biomass in the lake area is higher than that in the tributaries, while the density is the opposite.
For the comparative analysis of each lake area and tributaries, the bivalve community shows significant spatial heterogeneity (Figure 4). The average density of the Dasha River was the highest, significantly greater than that of the Guache River (p < 0.05), Longmian River (p < 0.05), Kongcheng River (p < 0.001), Chang River (p < 0.001), and the three lakes (p < 0.001). The average biomass of Xizi Lake was the largest, significantly greater than that of the other two lake areas (p < 0.05), Dasha River (p < 0.05), and Chang River (p < 0.05). The average density and average biomass were both the smallest in CR. Besides the above significant differences, the average biomass of CR was also significantly lower than that of DS. The differences in average density and average biomass among the other water bodies were not significant (p > 0.05).

3.3. Community Diversity

For the Caizi Lake system overall, the Shannon–Wiener diversity index (H′) was 1.735, the mean Pielou evenness (D) was 0.600, and the mean Margalef richness (C) was 2.665.
For the overall comparative analysis of the lake area and its tributaries, the average diversity index, evenness index and richness index of the lake area are 1.740, 0.678 and 2.454, respectively. The average diversity index, evenness index and richness index of the tributaries were 1.451, 0.584 and 1.797, respectively. Among the species diversity indices of the lake area and the tributaries, the three diversity indices of the lake area were all higher than those of the tributaries.
For the comparative analysis of each lake area and tributaries, Caizi Lake has the maximum richness index (1.924), Longmian River has the highest diversity index and evenness index, which are 1.812 and 0.931, respectively, and Chang River has the smallest diversity index in all three aspects. It is speculated that this is due to the direct damage to the habitat of bivalves caused by the renovation and dredging of the old and new river channels of Chang River 0.931 (Figure 5)
Cluster analysis of bivalve communities in eight investigated water areas shows (Figure 6a) that the bivalve community structure of the Caizi Lake water system is divided into three subgroups at a similarity level of 24.92%. The Dasha River, Kongcheng River, Guache River and Longmian River belong to Group I, the three lakes belong to Group II, and Chang River alone belongs to Group III. The stress coefficient (Stress = 0.02) confirms the exceptionally high reliability of the NMDS ordination plot [44], and the result is in strong agreement with the cluster analysis, collectively providing robust support for the conclusion that the bivalve community within the Caizi Lake water system can be classified into three significantly distinct groups (Figure 6b).

3.4. Community Stability

Since only a single live Corbicula fluminea was collected in Chang River during quantitative sampling, community stability analysis was not conducted on it. For the remaining seven waterbodies, ABC curves (Figure 7) showed intersections between the abundance and biomass dominance plots, with W ranging from −0.430 to 0.448, indicating substantial variability in stability. Dasha River had W < 0, consistent with a strongly disturbed community dominated by small-bodied, r-strategist taxa. Xizi Lake and Guache River had W ≈ 0, suggesting moderate disturbance and dominance by transitional species with short life cycles and high growth rates. In contrast, Baitu Lake, Caizi Lake, Kongcheng River, and Longmian River had W > 0, indicative of lower disturbance and communities dominated by K-strategists—large-bodied, long-lived taxa with slow growth and late maturity but substantial biomass contributions.

3.5. Correlation Between Community Structure and Environmental Drivers

In the Spearman correlation analysis (Figure 8a), a correlation analysis was conducted on the matrix composed of environmental drivers and the number of species, the number of individuals, and the density of bivalve species in Caizi Lake Group. The results showed that the species richness and density of the bivalve community were significantly negatively correlated with turbidity (p < 0.05), and in biological factors, they were not significantly positively correlated with the bitterling and host fish and phytoplankton (p > 0.05) and not significantly positively correlated with zooplankton (p > 0.05).
By applying the quantitative collection data of bivalves in the Caizi Lake Group and data of biological factors, etc., for de-trend correspondence analysis (DCA), it can be known that the length of the first axis is less than 3, and RDA can be conducted. The RDA results are shown in Figure 8b. The explanatory degree of the first ranking axis is 50.55%, and the cumulative explanatory rates of species and the environment in axes one and two reach 86.37%. The coordinate axes have a relatively high explanatory rate for the correlation between species richness and environmental drivers. As can be seen from Figure 8b, the relevant fish species contribute the most to the richness of each species. The other environmental drivers are phytoplankton, zooplankton, water temperature, dissolved oxygen, pH, water period, transparency, turbidity, water depth, substrate type, and electrical conductivity in sequence. The relationship between species richness and environmental drivers shows that most species, such as the dominant Corbicula fluminea, are positively correlated with related fish species, substrate types, dissolved oxygen, water depth, and electrical conductivity, and negatively correlated with zooplankton and turbidity.

4. Discussion

4.1. Current Situation of Bivalve Community and Its Diversity

This study presents the first systematic investigation of bivalve resources in the Caizi Lake water system during the fourth year following the implementation of the Yangtze River fishing ban. A total of 22 species belonging to 15 genera and 5 families of bivalves were recorded, among which 19 species belonging to 14 genera and 3 families were recorded in the tributaries, and 19 species belonging to 12 genera and 4 families were recorded in the lake area. Compared with historical data before the fishing ban [24,25,26,27,28], the species composition of bivalves in the Caizi Lake water system has changed, with three newly recorded species—Ptychorhynchus pfisteri, Uninovaculina chinensis and Lamprotula leaii—documented in this survey. Following the implementation of the fishing ban, fish resources—including the bitterling and host fish—have gradually recovered, potentially facilitating the proliferation and dispersal of bivalve populations [49]. Species with historical records but not collected in this study include Anemina euscaphys, Anemina fluminea, Gibbosula rochechouartii, and Corbicula largillierti. Among these, due to issues of taxonomic validity, some researchers have reidentified Anemina euscaphys and Anemina fluminea as Anemina arcaeformis [30,50]. Furthermore, according to IUCN [14], Gibbosula rochechouartii and Corbicula largillierti are, respectively, in VU and NA, the absence of these two species in the present survey may be attributed to their small population sizes, limited research effort, and incomplete spatial coverage of the investigation area. Therefore, the continued presence of these species within the Caizi Lake water system requires confirmation through long-term monitoring [51].
The dominant status of Corbicula fluminea across the system is consistent with its broad distribution and strong ecological plasticity [52,53]. Its higher dominance in tributaries than in lakes likely relates to faster flows and gravelly substrates that favor its burrowing habit. In contrast, the relatively slow, deeper, and lentic conditions of the lake basins provide stable settings for the filter-feeding of Cristaria plicata, whose dominance there is more pronounced than that of Corbicula fluminea [49].

4.2. Spatial Heterogeneity of Bivalves in the Caizi Lake Water System

The density of bivalves in the Caizi Lake water system shows that the tributaries are greater than those in the lake area, while the biomass shows that the lake area is greater than the tributaries. Cluster analysis significantly distinguished the four tributaries (Group I), the lake areas (Group II), and Chang River (Group III) into three groups. The stress of NMDS analysis was 0.02, confirming the significant community differentiation [46]. It is speculated that different water body types and substrate types may be the main factors driving the changes in the community structure of bivalves. The Venn comparison indicated 15 species shared between lakes and tributaries and three habitat-specific species, implying divergent habitat preferences. Limnoperna fortunei prefers to attach to hard substrates such as artificial pipes. Sinosolenaia oleivora and Parvasolenaia rivularis mainly inhabit hard muddy water bodies with a certain flow and lead benthic burrowing lives. This spatial heterogeneity is consistent with the findings of Vaughn and Hakenkamp [1], emphasizing the role of habitat diversity in shaping bivalve communities.
The ABC curve reveals that he system as a whole is under moderate disturbance. Compared with the collection of 9 genera and 15 species in Caizi Lake and Xizi Lake, respectively, only 7 genera and 9 species were collected in Bai Tu Lake. The differences in bivalve resources among the three lake areas should mainly be influenced by human activities. Baitu Lake is the only one in the lake group where there are residual field ridges [54]. The high organic matter in sediments in the field ridge area limit gill respiration and filtration efficiency, which may lead to a decrease in the survival rate of bivalve larvae [55]. Unlike the relatively common solidification of the shoreline in Caizi Lake, Xizi Lake mostly features natural shorelines, which usually have diverse substrates and vegetation coverage. Shoreline hardening reduces habitat heterogeneity, and bivalve richness and density are significantly lower along artificial shores than natural ones [1]. Natural shorelines filter and absorb land-based pollutants through vegetation buffer zones, but the function of solidifying shorelines is relatively weak, which easily leads to the direct inflow of nutrients such as nitrogen and phosphorus into water bodies, causing eutrophication. Eutrophication is one of the key driving factors for the decline of freshwater bivalve populations, especially in artificially modified lakes and rivers [51].
Among the tributaries, due to the riverbed disturbance caused by the river channel improvement project, the Dasha River has formed a community characteristic of bivalves with high density and low biomass, dominated by opportunistic species such as Corbicula fluminea that can rapidly settle in the disturbance substrate, which is basically consistent with the community characteristics of dredged rivers worldwide [52]. The extreme scarcity of bivalves in Chang River is directly related to the habitat loss caused by the transformation of old and new river channels, indicating that it is difficult to reverse the systematic degradation of the habitat merely by fishing bans [56]. Different tributaries have heterogeneity in the substrate. The substrate directly affects the attachment, burrowing and filter-feeding behaviors of bivalves, and simultaneously influences species richness and species distribution [57,58,59,60]. Substrate heterogeneity can accommodate species from different ecological niches. Research in the Chao Lake Basin shows that in areas with high substrate heterogeneity, bivalves coexist with aquatic insects, and the species richness is significantly enhanced [61]. In the waters investigated, the Dasha River has a rich variety of sediment types, including sand and hard mud. Only Sinosolenaia oleivora and Parvasolenaia rivularis, which mainly inhabit hard mud, were found in the Dasha River. Moreover, Corbicula fluminea and Acuticosta chinensis, which prefer sandy substances, have the highest species richness in the Dasha River. The bottoms of the Guache River, Longmian River and Kongcheng River are mostly silt, sand and gravel, and stony. Universal species such as Nodularia douglasiae and Sinanodonta woodiana account for a relatively large proportion.

4.3. The Environmental Drivers of Bivalve Species Diversity in the Caizi Lake Water System

RDA revealed that the bitterling and suitable host fish, phytoplankton and zooplankton were key environmental drivers significantly influencing species richness. The results of Spearman correlation analysis were largely consistent with those of the RDA.
The abundance of host fish directly determines the reproductive success rate of bivalves. The decline in their resources limits the parasitic opportunities of glochidia, thereby leading to the decline of bivalve populations. Fish migration activities also affect the geographical diffusion of bivalve larvae, thereby shaping the genetic diversity of the population. In the North American river system, the decline in the population density of host fish is significantly associated with the reduction in the species richness of freshwater mussels [62]. Phytoplankton such as Nitzschia and Navicula, as secondary contributors, serve as a major food source for freshwater bivalves, which preferentially consume Bacillariophyta and other phytoplankton that are appropriately sized, non-motile, and easily digestible. The abundance and community structure of phytoplankton directly influence bivalve survival and growth, with studies indicating a positive correlation between phytoplankton diversity, biomass, and bivalve population density [51]. However, the excessive reproduction of phytoplankton such as Cyanophyta caused by eutrophication may reduce the quality of food, inhibit the filtering efficiency of bivalves, and indirectly threaten the stability of the population [63,64].
The relationship between zooplankton and bivalves is rather complex. Some zooplankton in the Caizi Lake Group such as Trichocerca, Bosmina, Moina are secondary food sources for bivalves, but their main roles are manifested as competition and indirect regulation. Zooplankton reduce the food supply of bivalves by preying on phytoplankton [65], and the competitive effect is more significant in nutrient-poor water bodies [66,67]. Zooplankton are also a food source for host fish, and their abundance indirectly affects the fish population, thereby influencing the parasitic success rate of bivalve larvae. Vaughn and Hoellein [5] emphasized that turbidity is a key abiotic factor restricting the diffusion of bivalve larvae. In this study, freshwater bivalves showed a negative correlation with turbidity. High-concentration suspended particles not only clog its gill structure and reduce the filtering feeding efficiency [68], but also hinder oxygen exchange and cause respiratory stress. This effect is particularly obvious at the juvenile stage [69]. Studies have shown that high turbidity reduces the food sources of bivalves and indirectly interferes with their reproduction [70].

5. Conclusions

This study represents the first systematic assessment of bivalve resources within the Caizi Lake water system following the implementation of the ten-year fishing ban on the Yangtze River. A total of 22 species, representing 15 genera and 4 families of freshwater bivalves, were documented, with Corbicula fluminea dominating the community composition. The species composition has changed significantly compared to historical data collected before the fishing ban. For the first time, Ptychorhynchus pfisteri and the second-class national key protected wild animals Lamprotula leaii and Uninovaculina chinensis have been recorded in the area. It is hypothesized that the fishing ban has facilitated the recovery of fish populations, including the bitterling and host fish, thereby promoting the proliferation and range expansion of bivalve communities. This research further reveals that the distribution of bivalves in the Caizi Lake water system shows spatial heterogeneity. This community is divided into three groups: Dasha River, Guache River, Longmian River, Kongcheng River (Group I), the lake areas (Group II), and Chang River (Group III). Among them, the biomass in the lake areas is higher than that in tributaries, while the density is the opposite, but the differences are not significant. Due to variations in human activities such as shoreline types among lake areas and differences in substrate heterogeneity among tributaries, there are also differences in species and species richness between lake areas and tributaries. Environmental factor analysis indicates that the bitterling and suitable host fish, phytoplankton, and zooplankton are the key factors driving the changes in bivalve species diversity. However, turbidity is significantly negatively correlated with species richness and density. The above research results emphasize the comprehensive impact of the interaction between biological and abiotic factors on the diversity of bivalve communities. In the future, long-term monitoring should be carried out, and the continuous impact of the 10-year fishing ban on the Yangtze River on the population dynamics of bivalves in the Caizi Lake water system should be systematically evaluated in combination with historical data. The research results fill the gap in the status and distribution characteristics of bivalve resources in the Caizi Lake water system following the fishing ban, providing scientific support for the conservation and protection management of freshwater bivalve resources and the healthy recovery of the water ecosystem and promoting the coordinated efforts of the fishing ban policy and ecological restoration.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/d17110773/s1; In the Supplementary File, Sheet 1 ‘Nonbiological factors’ contains the water environmental factors for each location. Sheet 2 ‘Sampling situation’ contains the morphological parameters of the bivalve individuals. Sheet 3 ‘Biological factors’ represents the processed biological factors; Sheet 4 ‘Spp. composition of bio-factors’ shows the species composition of biological factors.

Author Contributions

C.J.: Writing—original draft, Methodology, Investigation, Data curation; M.J.: Writing—review and editing, Methodology, Data curation; C.R.: Methodology, Investigation, Data curation; X.Z.: Methodology, Investigation, Data curation; B.L.: Methodology, Investigation, Data curation; K.L.: Writing—review and editing, Funding acquisition, Conceptualization. All authors have read and agreed to the published version of the manuscript.

Funding

The study was funded by the Key Waters Aquatic Biological lonitoring Project in Anhui Province (2023AHNYC016XQ).

Data Availability Statement

The original contributions presented in this study are included in the Supplementary Material. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Figure 1. Sampling sites of freshwater bivalves in the Caizi Lake water system.
Figure 1. Sampling sites of freshwater bivalves in the Caizi Lake water system.
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Figure 2. The species composition of the Caizi Lake water system.
Figure 2. The species composition of the Caizi Lake water system.
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Figure 3. Species distribution in the spatiotemporal pattern. (a) Three water periods; (b) Lake area and tributaries; (c) Three lake areas; (d) Five tributaries. NW indicates normal-water period; HW indicates high-water period; LW indicates low-water period; RS indicates River system; WL indicates whole lake; MT indicates main tributaries.
Figure 3. Species distribution in the spatiotemporal pattern. (a) Three water periods; (b) Lake area and tributaries; (c) Three lake areas; (d) Five tributaries. NW indicates normal-water period; HW indicates high-water period; LW indicates low-water period; RS indicates River system; WL indicates whole lake; MT indicates main tributaries.
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Figure 4. Spatial characteristics of bivalve density (a) and biomass (b) in the Caizi Lake water system. * indicates p < 0.05; ** indicates p < 0.001; ★ indicates the average; The thick black line indicates the median.
Figure 4. Spatial characteristics of bivalve density (a) and biomass (b) in the Caizi Lake water system. * indicates p < 0.05; ** indicates p < 0.001; ★ indicates the average; The thick black line indicates the median.
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Figure 5. Species diversity index of each water area and indices of Pielou’s evenness (D), Margalef richness (C) and Shannon–Wiener (H′).
Figure 5. Species diversity index of each water area and indices of Pielou’s evenness (D), Margalef richness (C) and Shannon–Wiener (H′).
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Figure 6. Bray–Curtis clustering (a) and NMDS sequencing analysis (b) of bivalve communities in the Caizi Lake water system.
Figure 6. Bray–Curtis clustering (a) and NMDS sequencing analysis (b) of bivalve communities in the Caizi Lake water system.
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Figure 7. ABC curves of macrobenthos in Caizi lake water system: (a) Baitu Lake, (b) Caizi Lake, (c) Xizi Lake, (d) Dasha River, (e) Guache River, (f) Kongcheng River and (g) Longmian River.
Figure 7. ABC curves of macrobenthos in Caizi lake water system: (a) Baitu Lake, (b) Caizi Lake, (c) Xizi Lake, (d) Dasha River, (e) Guache River, (f) Kongcheng River and (g) Longmian River.
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Figure 8. Correlation analysis of bivalve communities and environmental factors. (a) Spearman correlation analysis of the Caizi Lake Group and bivalve communities—environmental drivers. (b) RDA of bivalve species in the Caizi Lake Group. WP represents different water periods; SD stands for transparency; T is the water temperature; pH is the degree of acidity or alkalinity; DO stands for dissolved oxygen; NTU stands for turbidity; Cond stands for Conductivity; WD represents the water depth; S is the substrate. * indicates p < 0.05.
Figure 8. Correlation analysis of bivalve communities and environmental factors. (a) Spearman correlation analysis of the Caizi Lake Group and bivalve communities—environmental drivers. (b) RDA of bivalve species in the Caizi Lake Group. WP represents different water periods; SD stands for transparency; T is the water temperature; pH is the degree of acidity or alkalinity; DO stands for dissolved oxygen; NTU stands for turbidity; Cond stands for Conductivity; WD represents the water depth; S is the substrate. * indicates p < 0.05.
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Table 1. Dominance status and distribution of bivalves in the Caizi Lake water system—indicates non-existent species.
Table 1. Dominance status and distribution of bivalves in the Caizi Lake water system—indicates non-existent species.
SpeciesIRI
Caizi Lake Water SystemLake AreasMain Tributaries
Corbicula fluminea (Müller, 1774)2045.671160.4328,677.74
Cristaria plicata (Leach, 1815)957.902206.91-
Lamprotula caveata (Heude, 1877)473.19908.9091.57
Sinanodonta woodiana (Lea, 1834)175.8643.21853.48
Nodularia douglasiae (Griffith & Pidgeon, 1833)151.6211.25950.26
Acuticosta chinensis (Lea, 1868)51.59-438.38
Sinanodonta pacifica (Heude, 1878)6.743.8625.46
Anemina arcaeformis (Heude, 1877)16.702.17117.56
Sinanodonta elliptica (Heude, 1877)9.66-114.68
Uninovaculina chinensis (Liu & Zhang, 1979)5.7034.64-
Parvasolenaia rivularis (Heude, 1877)4.94-31.45
Lanceolaria gladiola (Heude, 1877)2.492.5412.44
Sinosolenaia oleivora (Heude, 1877)1.85-14.11
Acuticosta ovata (Heude, 1877)1.83-16.77
Lamprotula leaii (Gray, 1833)1.472.06-
Sinohyriopsis cumingii (Lea, 1852)1.012.41-
Lanceolaria grayii (Lea, 1834)0.601.67-
Limnoperna fortunei (Dunker, 1857)0.271.64-
Table 2. The endangered status of bivalves in the Caizi Lake water system. T, threatened (=CR, EN, and VU); CR, Critically Endangered; EN, Endangered; VU, Vulnerable; NT, Near Threatened; LC, Least Concern; DD, Data Deficient; NA, not assessed; II, national category II key protected wildlife.
Table 2. The endangered status of bivalves in the Caizi Lake water system. T, threatened (=CR, EN, and VU); CR, Critically Endangered; EN, Endangered; VU, Vulnerable; NT, Near Threatened; LC, Least Concern; DD, Data Deficient; NA, not assessed; II, national category II key protected wildlife.
SpeciesOccurrenceShu
[20]		Liu
[13]		IUCN
[14]		Protection Class
[48]
Mytilidae
Limnoperna fortunei0.01LCNANA
Corbiculidae
Corbicula fluminea0.35LCNALC
Solecurtidae
Uninovaculina chinensis0.05DDNANAII
Unionidae
Nodularia douglasiae0.12LCLCLC
Parvasolenaia rivularis0.01NAENNA
Sinosolenaia oleivora0.01TVUNA
Acuticosta chinensis0.06NTLCLC
Acuticosta ovata0.02NTLCLC
Anemina arcaeformis0.05LCLCLC
Sinanodonta woodiana0.15LCLCLC
Sinanodonta elliptica0.02NANANA
Sinanodonta pacifica0.04NANANA
Cristaria plicata0.19LCLCLC
Sinohyriopsis cumingii0.01LCLCLC
Lamprotula caveata0.14LCLCLC
Lamprotula leaii0.01TLCLCII
Lanceolaria eucylindrica0TNANA
Lanceolaria gladiola0.02TLCLC
Lanceolaria grayii0.01NTLCLC
Lanceolaria lanceolata0NTNTLC
Schistodesmus lampreyanus0TLCLC
Ptychorhynchus pfisteri0TVUNT
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Jiang, C.; Jiang, M.; Ren, C.; Zhang, X.; Li, B.; Liu, K. Diversity Patterns and Environmental Drivers of Bivalve Communities in the Caizi Lake Group and Its Major Tributaries During the Initial Post-Fishing Ban Period. Diversity 2025, 17, 773. https://doi.org/10.3390/d17110773

AMA Style

Jiang C, Jiang M, Ren C, Zhang X, Li B, Liu K. Diversity Patterns and Environmental Drivers of Bivalve Communities in the Caizi Lake Group and Its Major Tributaries During the Initial Post-Fishing Ban Period. Diversity. 2025; 17(11):773. https://doi.org/10.3390/d17110773

Chicago/Turabian Style

Jiang, Chao, Min Jiang, Chenliang Ren, Xiaoke Zhang, Bowen Li, and Kai Liu. 2025. "Diversity Patterns and Environmental Drivers of Bivalve Communities in the Caizi Lake Group and Its Major Tributaries During the Initial Post-Fishing Ban Period" Diversity 17, no. 11: 773. https://doi.org/10.3390/d17110773

APA Style

Jiang, C., Jiang, M., Ren, C., Zhang, X., Li, B., & Liu, K. (2025). Diversity Patterns and Environmental Drivers of Bivalve Communities in the Caizi Lake Group and Its Major Tributaries During the Initial Post-Fishing Ban Period. Diversity, 17(11), 773. https://doi.org/10.3390/d17110773

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