Haoran Liu

As a typical ecological aquaculture model, rice–fish integrated culture provides an alternative pathway to precision aquaculture. However, systematic comparisons of the effects of these two aquaculture models on the physiological health of Eleotridae fishes remain lacking. This study utilized Odontobutis potamophila and conducted a 3-month aquaculture experiment. The results show the precision model produced greater increases in standard length and body weight. However, serum levels of total cholesterol, triglycerides, glucose, and transaminases were significantly elevated, accompanied by tissue damage. In contrast, the ecological model maintained an intact intestinal mucosal structure and compact hepatic tissue morphology. Microbial analysis indicated that the ecological model enriched butyrate-producing bacterial genera and upregulated butyrate metabolism pathways. The precision model was dominated by microbial groups associated with rapid energy conversion. Intestinal metabolomics analysis indicated that the ecological model significantly enriched anti-inflammatory and antioxidant metabolites and activated homeostasis maintenance pathways. Whereas the precision model displayed lipid synthesis overload and oxidative stress. These results demonstrated that the ecological aquaculture model achieved robust growth while maintaining physiological homeostasis and intestinal microecological balance. Based on these findings, this study provides region-specific optimization pathways for aquaculture models across areas with different resource conditions. These insights provide theoretical and practical references for optimizing Eleotridae aquaculture and promoting sustainable global aquaculture development.

The freshwater sleeper (Odontobutis potamophilus) is a high-value freshwater fish endemic to China, farmed mainly in rice–crayfish–Odontobutis potamophilus integrated culture (RCO) and recirculating aquaculture systems (RAS). How these models differ in growth, physiological status, and feeding remains unclear. The same batch of fry was reared for three months (92 days) in six paddy fields (RCO, 3 individuals/m², no artificial feed, with access to natural food organisms and stocked crayfish) and six RAS tanks (6 individuals/m², fed Cirrhinus molitorella and pellet feed twice daily). Growth indicators were calculated from individual data of the sampled fish (n = 138 per model). Per group, 150 fish were sampled for stomach contents, 138 for morphometrics, and six for serum alanine aminotransferase (ALT), glutamic–oxaloacetic transaminase (AST), and glucose (GLU) assays; muscle nutritional composition was also determined. Relative weight gain rate (RWG) and specific growth rate in wet weight (SGRw) were significantly higher in RAS, with positive allometric growth in both models. Muscle crude protein was higher in RCO, whereas crude fat and serum ALT, AST, and GLU levels were higher in RAS, suggesting a heavier metabolic burden on the liver in RAS, which awaits confirmation with a broader panel of liver function markers. RCO stomachs contained nine food categories but had a 38% vacuity rate, whereas RAS fish consumed only C. molitorella (86% occurrence, 14% vacuity). Because stocking density and feeding regimen differed simultaneously between the two models, the observed differences reflect the overall effects of each culture model rather than the effect of the rearing system alone. These findings reveal a growth-metabolism trade-off between the two culture models as currently practiced: RAS produced faster growth accompanied by higher serum transaminase levels and body fat, whereas RCO maintained lower metabolic markers with slower growth. Moderate supplementary feeding in RCO and dietary diversification in RAS may reconcile yield and fish health.

Pine wilt disease is a devastating forest disease caused by Bursaphelenchus xylophilus infection. The associated bacterium Pseudomonas fluorescens and its flagellin protein have been implicated in this process, but the role of the flagellin-encoding gene fliC in pathogenesis remains unclear. Current gene knockout strategies in P. fluorescens are limited by low transformation efficiency and cumbersome procedures, which constrain functional studies of this gene. To address this methodological gap, we established a fliC knockout method based on the pT18sacB-sacB counterselection system. Short homologous arms were constructed by splice overlap extension PCR, and the knockout mutant ΔfliC was obtained through S17-1 λpir-mediated conjugation and sucrose counterselection. The mutant was verified by junction PCR, internal PCR, and sequencing. Using Pinus massoniana callus as the experimental material, we preliminarily compared the wild-type strain and the ΔfliC mutant in individual pathogenicity and in promoting complex infection by B. xylophilus. The ΔfliC mutant showed delayed symptom onset and lower disease severity than the wild type, and its ability to promote complex infection also appeared reduced. These results provide preliminary evidence that fliC contributes to symptom development in this callus assay. The established fliC knockout technique provides a methodological basis for further investigating the role of associated bacteria in pine wilt disease.

Poecilia reticulata is an important species in the global ornamental fish trade, known for its environmental adaptability and bright adult coloration. However, research on sex-dependent background color choice in this species remains limited, constraining the understanding of visual-environment requirements across sexes. In this study, we used a circular six-color maze (red, yellow, blue, green, black, and white) to independently test male and female P. reticulata at first sexual maturity. The results showed that both sexes spent proportionally more time in blue and green zones and less time in red zones, with no sex differences observed. This indicates a convergent pattern of immediate color choice between sexes at this stage. This cross-sex convergent choice pattern may reflect similar short-term visual-environment requirements between sexes. This study provides descriptive baseline data on immediate color choice, which can serve as a reference for subsequent investigations into long-term stable color preferences in this species. The sex-separated testing approach also offers a methodological reference for similar studies in other species.

The color preference of juvenile bronze gudgeon (Coreius heterodon), an endemic fish species in the Yangtze River, remains poorly understood despite its importance in animal welfare and aquaculture. In this study, color selection behavior was assessed across 6 background colors (red, yellow, blue, green, black, and white) under both isolated and grouped social conditions, using a 6-arm radial maze. The results reveal that juvenile C. heterodon exhibit a strong and consistent preference for yellow–green backgrounds and distinct avoidance of black–red, regardless of social context, with these behaviors likely rooted in early imprinting, that is, fixed responses formed without the need for subsequent reinforcement. Social condition was found to modulate responses to white and blue, shifting white from slightly attractive to neutral/aversive and blue from aversive to attractive. These findings directly inform aquaculture practice, suggesting that establishing yellow–green substrates while minimizing black–red areas is advisable. Presumably, prerelease acclimatization based on imprinting mechanisms would shorten natural acclimatization time and enhance poststocking survival. Our findings provide a scalable, behaviorally informed framework for optimizing welfare and production in C. heterodon and related species.

Coreius guichenoti, an endemic fish of the upper Yangtze River, has experienced severe population decline due to overfishing and habitat fragmentation. To inform its conservation, this study compared life-history traits between artificially bred and historical wild populations, revealing pronounced plasticity in response to environmental conditions. The cultured population, dominated by age 0–4 individuals but retaining a notable proportion of age 5–6 fish, exhibited faster growth and higher fecundity (mean absolute fecundity 32,724 ± 24,132 eggs; relative fecundity 37.5 ± 18.5 eggs/g) than the wild population. In contrast, the wild group consisted of >90% age 0–4 individuals, showed virtually no fish aged 5–7, reproduced seasonally with high total egg output, and tended toward a periodic life-history strategy, whereas the cultured group tended toward an opportunistic strategy that still retained some periodic traits. These results demonstrate that C. guichenoti can adjust its life history on a within-generation scale. Accordingly, we recommend pre-release conditioning with moderate flow and temperature variations to enhance field adaptability. This study provides evidence-based guidance for broodstock selection and preconditioning in restocking programs, aimed at improving post-release survival and reproductive success in the wild.

The Geheyan Reservoir, located on the Qingjiang River, a tributary of the Yangtze River, is important for regional water supplies and ecological conservation. Understanding changes in ecosystem structure and function has become critical for assessing efficacy after the implementation of a fishing ban. This study employs the Ecopath model to examine the ecosystem characteristics of the Geheyan Reservoir before (2017) and after (2022) the fishing ban. The results show significant differences in trophic levels, energy transfer efficiency, and ecosystem maturity between the two periods. The trophic levels increased from 3.36 pre-fishing ban to 3.89 post-ban, indicating an enhanced complexity in the food web structure. The highest eco-trophic efficiency for major commercial fish species increased after the ban, indicating improved energy utilization efficiency. However, energy transfer bottlenecks were still observed between trophic levels II and IV, suggesting ongoing challenges in nutrient cycling. The total primary production-to-total respiration ratio (6.93) and the connectivity index (0.25) indicate that the ecosystem’s maturity and stability have improved after the fishing ban. These findings underscore the ban’s effectiveness and provide a scientific foundation for sustainable management of Geheyan Reservoir and similar ecosystems in the Yangtze River Basin.