The construction of the Guxian Water Control Project causes blockage of river sections, hindering population exchange between fish upstream and downstream across the dam. Fish passage facilities can mitigate this barrier, and detailed knowledge of fish swimming behavior is critical for their effective design. This study targeted two main fish species for the project: Leuciscus waleckii Dybowski and Opsariichthys bidens-and tested their induced velocity and critical swimming speed. The study also analyzed ecological behavioral indicators including tail-beat frequency, tail-beat amplitude, body wave velocity, body wave length, maximum head angle, and maximum head angle velocity during upstream swimming at three swimming velocitys (2, 4, and 6 BL/s). The results showed that the absolute induced velocities of Leuciscus waleckii Dybowski and Opsariichthys bidens were (0.06±0.01) and (0.11±0.03) m/s, respectively, with corresponding relative values of (0.55±0.11) and (1.11±0.27) BL/s. The absolute and relative rheoreaction velocities of Leuciscus waleckii both exhibited significant negative correlations with body length (P<0.05), whereas the absolute rheoreaction velocity of Opsariichthys bidens showed a significant positive correlation with body length (P<0.05). The absolute critical swimming speeds of Leuciscus waleckii Dybowski and Opsariichthys bidens were (0.99±0.20) and (0.96±0.14) m/s, respectively, and the relative critical swimming speeds were (9.30±1.14) and (10.07±1.47) BL/s, respectively. Both absolute and relative critical swimming speeds of Leuciscus waleckii Dybowski were significantly positively correlated with body length (P<0.05). For both species, tail-beat frequency, body wave velocity, and maximum head angle velocity increased with flow velocity, while tail-beat amplitude and maximum head angle decreased with increasing flow velocity. The body wave length of Leuciscus waleckii Dybowski at 2 BL/s was significantly higher than that under the other two swimming velocitys (P<0.05), whereas the body wave length of Opsariichthys bidens showed no significant change with increasing flow velocity (P>0.05). Among the ecological behavioral indicators, tail-beat frequency, maximum head angle velocity, and body wave velocity showed the strongest correlations with swimming speed, suggesting their central role in propulsion. For fish-passage designs targeting Leuciscus waleckii Dybowski and Opsariichthys bidens, we recommended an entrance velocity of 0.9—1.2 m/s for upstream collection vessels and an internal velocity of 0.1—0.9 m/s within the collection chamber. This study quantifies the swimming ability and key swimming behavioral characteristics of two representative fish-passage target species, providing a reference for the design and optimization of fish passage facilities.

To investigate the relationship between personality traits and cognitive abilities in fish, this study used juvenile Chindongo demasoni, a highly social cichlid species, as the model organism. Through associative learning training and tests based on a “color-food reward” paradigm, we assessed cognitive performance and analyzed its correlation with three personality traits: activity, boldness, and sociability. The results showed that: (1) Activity and boldness were positively correlated in Chindongo demasoni (P=0.024), supporting the Behavioral Syndromes Hypothesis; (2) The fish successfully formed associations between color cues and food rewards through associative learning, with the correct choice rate increasing significantly over training days (P<0.001); (3) Sociability was positively correlated with cognitive performance, as measured by the correct choice rate during the test phase (P=0.006), while no significant relationship was found between cognitive performance and either activity or boldness. The link between sociability and cognitive ability supports the Social Brain Hypothesis, suggesting that for social fish, the demand to process complex social information may be an important driver in the evolution of cognition.

The functional restoration of large river ecosystems represents a significant global challenge. The “Ten-Year Fishing Ban” implemented across the Yangtze River Basin, a large-scale ecological intervention, offers an unprecedented opportunity to investigate the recovery processes in a highly regulated aquatic ecosystem. This study aimed to comprehensively explore structural changes in the fish community food web in the tailrace of the Three Gorges Reservoir (TGR) after the fishing ban. We focused on two hydro-morphologically distinct river sections, the downstream Fuling section and the upstream Mudong section, to analyze the spatio-temporal responses of the food web. Our methodology integrated stable isotope analysis (δ¹³C and δ¹⁵N), an advanced Bayesian Isotope Mixing Model (BIMM) incorporating trophic-level constraints and prior dietary information, and food web topological analysis. Fish and basal food source samples were collected before (2018—2019) and after (2023) the ban implementation. Our results reveal that although species richness recovered similarly in both sections (increasing to 36 species each), food web restructuring followed two divergent pathways shaped by local habitat. The food web exhibited “vertical deepening”: connectance decreased from 0.085 to 0.070 and generalization index from 2.55 to 2.44, indicating more specialized trophic interactions. Concurrently, an expanded δ¹⁵N range (10.94‰ to 11.51‰) reflected food chain elongation, and the proportion of omnivorous species rose from 58.3% to 65.5%. These shifts, together with an increased piscivorous diet in the key predator Siniperca kneri, support a top-down recovery cascade driven by restored predator populations. In contrast, the riverine Mudong section underwent “bottom-up reorganization” toward a flatter structure: connectance increased from 0.070 to 0.077 and the generalization index from 2.21 to 2.69, suggesting more generalized feeding links. However, this was accompanied by a compressed δ¹⁵N range (11.77‰ to 10.47‰), indicating a shorter food chain, and a decline in omnivory from 65.4% to 55.2%. Isotopic data revealed greater reliance on terrestrial C3 plant-derived carbon sources. The diet of the key predator, Culter alburnus, shifted from 78.9% to 64.9%, reflecting increased use of lower-trophic-level resources. This pattern suggests that the recovery was primarily driven by enhanced primary production and terrestrial organic matter inputs, facilitated by stronger land-water coupling and Flood Pulse Concept. In conclusion, ecological recovery after a major conservation intervention such as the fishing ban is not uniform; trajectory depends on local environmental conditions such as flow velocity and floodplain connectivity. These findings underscore the critical importance of assessing functional attributes like food web structure alongside biodiversity metrics. This research provides a crucial scientific foundation for developing and implementing spatially differentiated, adaptive management in the Yangtze River Basin to improve the effectiveness of large-scale conservation efforts.

To investigate interspecific variations in group behaviour characteristics among six Cyprinidae species and their responses to exercise training, we selected Carassius auratus, Tinca tinca, Cyprinus carpio, Spinibarbus sinensis, Procypris rabaudi, and Acrossocheilus fasciatus as experimental subjects. At 25℃, each species was divided into control groups, anaerobic exercise training groups (1 session/d), and aerobic exercise training groups [4 times body length per second (bl/s), 18h/d] for three weeks. Subsequently, within a six-arm maze, the following parameters were measured under both non-predator and simulated predator stimuli: centre density (CD), shelter density (SD), non-shelter density (NSD), and cohesion index (I_c). The results indicated that under both non-predator and simulated predator stimulation, the control groups of C. auratus, T. tinca, C. carpio, and S. sinensis exhibited relatively higher CD, NSD, and I_c values along with lower SD, whereas the control group of P. rabaudi showed relatively lower CD and NSD along with I_c higher SD and I_c values. The control group of A. fasciatus displayed relatively lower CD, SD, and I_c values but higher NSD. Regardless of predator stimulation, exercise training did not produce statistically significant effects on the collective behavioral characteristics of C. auratus, T. tinca, and C. carpio. Anaerobic exercise training led to an 81% significant decrease in NSD and a 21% significant increase in I_c values in P. rabaudi under non-predator stimulation (P<0.05); anaerobic exercise training resulted in a 39% significant increase in I_c values in A. fasciatus under simulated predator stimulation (P<0.05); aerobic exercise training caused a 17% significant decrease in I_c values in S. sinensis under non-predator stimulation (P<0.05). The study demonstrates that: (1) There are significant interspecific differences in the collective behavioral characteristics among the six cyprinid species, which may be related to their living habits and habitat factors; (2) Exercise training exerts varying degrees on collective behavioral characteristics by fish species and training regimen.

To investigate the impact of the ten-year fishing ban on fish community structure and diversity, this study conducted fish resource surveys in four sections of the middle Yangtze River—Zhijiang, Jianli, Yueyang, and Huangshi—during the spring and autumn seasons from 2022 to 2024. A total of 91 species belonging to 15 families and 10 orders of fish were investigated. Cyprinidae fish are the most abundant (59 species, 64.84%), with lake-type fish (47.25%) and omnivorous fish (65.93%) being the predominant ecological types. Relative Importance Index (IRI) analysis identified eight dominant species: silver carp, bighead carp, crucian carp, grass carp, silver bream, snakehead, shortjaw goby, and yellow catfish, predominantly medium-to-large economic fish. In 2024, 72 fish species were monitored in the middle reaches of the Yangtze River, representing an increase of 10 species compared to 2022, while the average catch per unit effort (CPUE) rose by 11.35% to 10.40 kg per haul. The Shannon-Wiener diversity index remained relatively stable (3.06—3.22). The abundance/biomass comparison curve indicated low disturbance in the fish communities. Cluster and NMDS analyses separated the fish community into two distinct clusters: Zhijiang formed one cluster, while Jianli, Yueyang, and Huangshi formed another. Following the implementation of the 10-year fishing ban in the Yangtze River, CPUE showed an upward trend. Key fish resources such as the four major carp species and croaker recovered relatively quickly, indicating phased success of the ban. However, the diversity index remained relatively stable, suggesting that species diversity recovery is a long-term process. These findings provide scientific support for evaluating the effectiveness of the fishing ban and dynamically adjusting related policies.

Polycyclic aromatic hydrocarbons (PAHs), as a class of persistent organic pollutants (POPs), tend to accumulate in organisms due to their lipophilic. Penaeus vannamei, widely cultivated in such settings, is particularly susceptible to PAHs contamination, which may ultimately endanger human health. In this study, the contamination characteristics, ecological risks, and human health risks of 16 PAHs in a cultured water-biological system were investigated. Results showed that the total concentrations of the 16 PAHs (∑PAHs) in aquaculture water ranged from 44.62 to 350.46 ng/L, with Nap, Phe, BaA, Pyr, Chr, Flu, and Ace being the main pollutants. Pollution source analysis based on characteristic ratios showed that PAHs originated primarily from oil, coal combustion, and other biomass combustion. In shrimp muscle, the total concentrations of 16 PAHs ranged from 0.34 to 208.37 μg/kg (dry weight, dw), with 12 PAHs detected, and LMW PAHs predominated, while 5- and 6-ring PAHs accounted for minor proportions. The ILCR values associated with dietary exposure to shrimp ranged from 1.08×10^–11—2.02×10^–8, which was much lower than the USEPA standard value of 1×10^–6, indicating negligible carcinogenic risk under current conditions.

To understand the diversity characteristics and interannual variations of the fish community in the middle reaches and tributaries of the Huishui River during the early stage of the fishing ban, fish resource surveys were conducted from 2021 to 2023. A total of 59 fish species were collected, belonging to 40 genera, 12 families, and 7 orders. Among them, Cyprinidae fish were in an absolute dominant position, accounting for 67.80% of the total species, 89.22% of total abundance, and 91.65% of total biomass. The ecological types are dominated by benthic, omnivorous, and spawn-laying fish, with the proportions of species being 55.93%, 55.93%, and 44.07% respectively. Interannual characteristics showed that species richness ranged from 35 to 49, among which the common dominant species were Zacco platypus and Acrossocheilus fasciatus. The Margalef index, Shannon-Wiener index, and Pielou index all showed a fluctuating upward trend overall, ranging from 4.18—5.34, 1.97—2.37, and 0.55—0.62, respectively, while the Simpson index showed a downward trend from 0.19 to 0.31. Cluster analysis showed that community structure in spring, summer, and winter of 2021 was similar, as was that in winter of 2022 and winter of 2023; all other sampling occasions grouped together. This suggests that community recovery followed distinct phases, with a unique response pattern in the early stage (2021). Spatially, the main stream and tributaries generally formed separate clusters, indicating that habitat-driven differences remained dominant. Overall, the recovery of community structure was driven by multiple factors under temporal dynamics, including habitat conditions and seasonal variation, exhibiting phased progression and spatial heterogeneity. This research clarifies the characteristics and diversity trends of the fish community in the Huishui River during the initial stage of the fishing ban, providing a basis for the assessment of the fishing ban effect and the scientific management of aquatic biological resources.

This study investigated the phytoplankton community structure, dominant species’ niche characteristics, and interspecific association in the Donghu Reservoir, Datun Reservoir, and Shuangwangcheng Reservoir along the Eastern Route of the South-to-North Water Diversion Project in Shandong Province. During the survey, 8 phyla, 59 genera, and 116 species of phytoplankton were identified, with Cyanophyta, Chlorophyta, and Bacillariophyta being the dominant groups. The phytoplankton communities in the reservoirs exhibited distinct seasonal succession patterns, that is, spring was characterized by a co-dominance of Bacillariophyta and Chrysophyta; Cyanophyta was absolutely dominant in summer and autumn, with harmful bloom-forming cyanobacteria such as Microcystis spp, Pseudoanabaena limnetica, and Cylindrospermopsis raciborskii were the dominant species; while Cyanophyta and Bacillariophyta were co-dominant phylum, with abundance of Pseudoanabaena limnetica reaching as high as 7.17×10⁶ cells/L. Niche analysis revealed that the average niche width (B_i) of dominant species in Cyanophyta increased by 77.3% and 34.0% in summer and autumn, respectively, indicating significant expansion during these seasons. Seasonal changes in niche overlap (ΔSO_ij) showed that Chlorophyta and Bacillariophyta were in developmental stages in spring, while the niche overlap of Cyanophyta continued to rise to 77.8% in summer and autumn, but the resource competitiveness of Cyanophyta gradually declined in autumn. Interspecific association analysis revealed that there was an overall non-significant negative association in spring and summer, and a significant positive association between the Cyanophyta and Chlorophyta in autumn, reflecting the functional complementarity and niche differentiation among these species. Among the 924 dominant species pairs, 57.47% showed significant association, with as many as 506 pairs having extremely significant negative associations, indicating that the community as a whole was in a state of intense competition. Based on these findings, it is recommended to incorporate positively associated species pairs with high niche overlap as water bloom early warning indicators into the risk management system, providing a scientific basis for ensuring drinking water safety.

This study investigated the relationships among energy metabolism, personality traits, and social hierarchy in breeding-season rosy bitterling (Rhodeus ocellatus), with further analysis of sex-specific differences. The results showed that male R. ocellatus had significantly higher standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS) than females (P<0.05), indicating a greater metabolic potential in males, likely linked to the high-energy-demand activities during reproduction. In females, SMR was positively correlated with both MMR and AS (P<0.05). In males, SMR was positively correlated with activity, while MMR and AS showed significant positive correlations with aggressiveness (P<0.05). The observed sexual differences in the relationships between metabolism and personality may stem from the distinct selective pressures and behavioral strategies experienced by males and females during reproduction. In both sexes, only activity was significantly and positively correlated with social hierarchy (P<0.05), while metabolic rates showed no correlation with hierarchy. These findings suggest that social hierarchy in R. ocellatus is determined more by behavioral traits than by metabolic levels, and while sex influences the relationship between energy metabolism and personality, it does not affect the mechanism determining social hierarchy.

To investigate the synergistic effects of probiotics and microalgae on larval rearing performance of giant freshwater prawn (Macrobrachium rosenbergii), this study selected Haematococcus pluvialis and Oocystis borgei, which were respectively combined with Clostridium butyricum and Lactobacillus for treatment. The impacts of different probiotic-microalgal combinations on larval survival, growth, development, water quality, and physiological parameters were systematically evaluated. The results showed that the O. borgei+Lactobacillus treatment achieved the highest survival rate (85.80%), significantly higher than that of the control group (50.2%, P<0.05), while the O. borgei+C. butyricum combination exhibited optimal performance in promoting larval growth and development. The two microalgae species demonstrated functional differentiation in water quality regulation: H. pluvialis showed significant advantages in nitrogen removal, whereas O. borgei was most effective in reducing organic matter load (COD_cr). Physiological analysis showed that probiotic-microalgal combinations could effectively alleviate oxidative stress in larvae, with malondialdehyde (MDA) content reduced by 68.3%—87.3% compared to the control (P<0.05), among which the H. pluvialis+C. butyricum combination demonstrated the strongest overall performance in antioxidant, immune, and digestive functions. Stepwise regression analysis revealed that total inorganic nitrogen (TIN) concentration and MDA were the key driving factors affecting larval survival rate, jointly explaining 61.0% of the variation. This study elucidates the mechanism by which probiotic-microalgal synergy enhances larval rearing efficiency through nutrient cycling and physiological regulation, providing theoretical basis and technical reference for microecological intervention in crustacean larviculture.