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.

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.

Group living brings numerous ecological benefits and costs, and changes in social status (such as from group living to social isolation) have a profound effect on the morphology, physiology, behaviour, and life history characteristics of social animals. Refuges are intricate and variable, however, most earlier studies on animal group behavior focused on a single ecological context. Therefore, to examine the effect of social isolation and ecological contexts on the group behaviour of cyprinid fish, we utilized common carp (Cyprinus carpio) as the experimental subjects, setting up two social status treatment groups (group-rearing, 5 fish maintained together; isolation group, single fish isolated alone). After 28 days, we measured the collective behavior of each treatment across three contexts: open water, food presence, and food+refuge. We found that, social isolation had no significant effect on the individual behaviour of common carp, but in the food context, both two groups had the fastest individual swimming speed, and in the food+refuge context, the synchronization of speed synchrony was the lowest. Social isolation and contexts have an impact on the collective behaviour and structure. The group speed and the percentage of time spent moving in group-rearing increased with context complexity. The isolation group exhibited a decrease in polarization and in both the open water and food+refuge displayed decreased group coordination and cohesion. After 28 days, foraging efficiency increased significantly in both treatments compared to day 0, while time spent in refuge decreased significantly. Group size in the isolation group was also significantly higher at day 28 than that at day 0. The study shows that social isolation reduces the activity and group coordination in common carp, and that increasingly complex ecological contexts improve the movement ability at the expense of group coordination.

To explore the influence of nutrient sources on the beta diversity patterns of macrozoobenthic communities in plateau lakes, a quantitative survey of macrozoobenthos and their nutrient sources was conducted in the Zhaling Lake and Eling Lake basins from 2022 to 2024 in the dry and wet seasons. A total of 108 taxa belonging to 8 orders, 39 families were collected. Overall, the lake, habitat, season, and their interactions showed no significant effects on zoobenthos species richness (P>0.05). However, total beta-diversity was relatively high and primarily driven by turnover component. We used parameters in water (chlorophyll a, phytoplankton, total nitrogen, total phosphorus) and catchment characteristics (vegetation coverage, altitude differences, precipitation) to quantify allochthonous inputs and autochthonous nutrients. The Chl.a was significantly higher in the wet season than that in the dry season (P<0.001), and the allochthonous input in the littoral zone of Eling Lake was significantly higher than that in the river region (P<0.01). The Random Forest model indicated that allochthonous nutrient had a stronger correlation with the beta-diversity of the macrozoobenthic community. Allochthonous inputs outweighed autochthonous nutrients in both river and littoral zones during the wet season. In contrast, during the dry season in littoral zone, the importance of autochthonous nutrients such as chlorophyll a and total phosphorus increased significantly, revealing a co-dominant pattern driven by internal and external sources. The total beta diversity and its turnover component exhibited greater sensitivity to allochthonous input, while nestedness in river zone during the wet season also showed certain responsiveness to autochthonous nutrient. These findings provide fundamental scientific support for the ecological management of plateau lake ecosystems.

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 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.

The efficient underwater sensing and attack mechanisms of electric eels provide significant inspiration for the development of biomimetic equipment. To this end, this paper investigates the response strategies and discharge patterns of electric eels under various behavioral intents. By constructing specialized test scenarios and integrating behavioral recordings, data acquisition, and bio-electric field simulations, we systematically analyzed the correlation between attack/defense postures and discharge logic, as well as the corresponding discharge characteristics of electric organs. The results reveal that a curled attack posture enhances targeting efficiency through synergistic electric field and circuit interactions. Simulations indicate it can increase the voltage delivered to prey more than three times. Touch-based experiments further identified a deep-water passive defense mechanism through double/triple pulses. By comparing behavioral and electrogenic organ discharge (EOD) patterns in active and passive defense, this study concludes that active defense is suitable for shallow water, while passive defense is suitable for deep water environments, providing a more complete theoretical framework for understanding the different biological behaviors in electric eels.

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.

In order to find out the difference of rheotaxis between narrow range species Pseudorasbora elongata and widespread species Pseudorasbora parva, and whether differences in flow sensitivity contribute to their contrasting distribution patterns, with the aim of informing conservation measures for P. elongata. In this study, we examined the induction velocity for P. elongata and P. parva with the increasing velocity protocol. The results showed that absolute induction velocity (AIF) was (2.88±1.00), (6.81±1.20), (9.63±2.28) cm/s, and relative induction velocity (RIF) was (0.47±0.11), (0.83±0.11), (1.09±0.24) BL/s for body length of 5.0—6.9, 7.0—8.4, 8.5—9.0 cm for P. elongate, respectively. Both AIF and RIF differed significantly among length groups (P<0.05). The AIF and RIF for body length of 5.0—6.9, 7.0—7.9, 8.0—9.0 cm was (5.25±0.82), (7.34±0.46), (7.91±1.03) cm/s, and (0.83±0.10), (0.98±0.06), (0.94±0.10) BL/s for P. parva, respectively. Except for the groups between 7.0—7.9 cm and 8.0—9.0 cm, there were significant differences in AIF and RIF between the other body length groups (P<0.05). The AIF and RIF were positively correlated with body length for both two species (P<0.001). Independent-samples t test showed that the AIF and RIF of P. elongata were significantly lower than that of P. parva (P<0.05). The greater sensitivity of the narrow-ranged P. elongata to water flow, compared to the widespread P. parva, is likely a key factor constraining its distribution. Therefore, conservation of P. elongata habitats should fully account for its rheotactic characteristics. River realignment should follow natural variations in channel width and morphology while meeting flood-discharge safety requirements. In addition, in the sections where the P. elongata has been distributed, the density of lower head dams should be reduced to maximize free-flowing intervals, and removal should be considered where feasible.