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.

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 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.

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.

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.

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.

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.

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.

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.

To investigate the effects of photoperiod on the feeding rhythms and gastrointestinal evacuation dynamics of second-instar juvenile Tachypleus tridentatus, this study examined diel feeding rhythms in second-instar juvenile T. tridentatus using eight observation time points over 24h under three photoperiod regimes: natural photoperiod, constant light, and constant darkness. Feeding rhythms were assessed via gastrointestinal satiety indices, and evacuation dynamics were tracked for 24h after satiation. The results showed that there were no significant differences in average satiety among time points within any photoperiod at 3h or 6h post-feeding. Under natural photoperiod at 3h, satiety was significantly higher at night than during the day, whereas no clear diel differences were observed under continuous light or darkness. By contrast, at 6h post-feeding, satiety indices were consistently higher at night than during the day under all three photoperiods. Feeding peaks under the natural photoperiod at 3h post-feeding occurred during the night-time period (21:00—06:00), while no distinct diel feeding rhythm was detected under continuous light or darkness. However, at 6h post-feeding, clear feeding rhythms emerged under both continuous light and continuous darkness, with feeding peaks occurring at 21:00—09:00, and 21:00—06:00, respectively. Most juveniles achieved substantial food intake within 3h, with only marginal increases observed by 6h. Gastrointestinal evacuation exhibited a biphasic pattern characterized by an initial rapid phase followed by a slower phase. First-time feeding juveniles reached 50% evacuation at 14.7h and 80% at 27.1h after satiation, whereas non-first-time feeding juveniles reached the same benchmarks at 8.8h and 16.3h, respectively. These findings demonstrate that second-instar juvenile T. tridentatus exhibit a pronounced diel feeding rhythm, only weakly influenced by photoperiod. Based on these results, it is recommended that juvenile rearing be conducted under a natural photoperiod with at least one feeding event after dusk and moderately extended during the early feeding stage. This study provides a scientific basis for optimizing feeding strategies in the artificial culture of juvenile T. tridentatus.