Search Results (250)

Introduction: The invasive European catfish (Silurus glanis) is actively spreading across Iberian freshwaters, with no effective management measures in place to control its growing abundance or prevent its establishment in new localities. It poses a severe threat to endemic and already endangered species, and is simultaneously a preferred target by few anglers who continuously promote its spread. The LIFE-PREDATOR project aims to stop the spread of European catfish in lentic systems in Portugal and Italy, particularly in protected areas. Objectives: This talk will present the mid-term results of the LIFE-PREDATOR in Portugal, and discuss the difficulties and future challenges to reduce the size of local populations of European catfish. Methodology: The LIFE-PREDATOR team developed several tasks in Portugal: (1) established the reference situation of fish communities in six reservoirs in the Tagus Basin, using scientific fishing, fish telemetry and eDNA-based tools; (2) determined the optimal protocols for sampling catfish; (3) implemented an early detection programme based on warning teams, data-mining and eDNA tools; (4) developed population control actions in four reservoirs; and (5) organised dissemination events for the general public, anglers, and students from kindergarten to university levels. Results: Overall, there is a grim view about recipient communities in the studied lentic systems, which tend to be dominated by invasive fish species, including common carp (Cyprinus carpio), gibel carp (Carassius gibelio), European catfish, pikeperch (Sander lucioperca), European perch (Perca fluviatilis) and largemouth bass (Micropterus nigricans). At least three new localities harbouring catfish were identified from online data-mining and warning teams. A total of 8 tons of catfish were removed by mid-June of 2025, mostly from the Natural Park of International Tagus. Outreach activities were conducted in nearly 60 schools, reaching more than 5000 students. Moreover, 67 general public events have reached more than 4500 people since the project started (September 2023). Conclusions: Despite its positive outcomes, the LIFE-PREDATOR team has encountered challenges in engaging key stakeholders such as anglers, involving local municipalities, and implementing catfish removal actions in remote areas. Difficulties and challenges in catfish management must therefore be debated in order to assure the after-LIFE implementation across Portuguese protected areas. Full article

Introduction: A diverse ichthyofauna is supported by the Lima River in northern Portugal. Despite its ecological significance, Ramsar-protected wetlands status and Natura 2000 site, the system remains among the least studied in the Iberian Peninsula. Objective: This study characterises the fish assemblage of the Lima River and some of its tributaries. It examines the composition and abundance of species, as well as key biological parameters, across the river’s freshwater and estuarine sections. Particular attention is given to the balance between native and exotic taxa, and to the threats facing the native ichthyofauna. Methodology: Between 2021 and 2023, 3242 individuals belonging to 15 species were sampled using fyke nets, trammel nets, and electrofishing at 13 sites along the river system. Results: Native species accounted for 51.1% of the total catch. This comprised resident freshwater taxa, such as Pseudochondrostoma duriense, Achondrostoma oligolepis, Luciobarbus bocagei, Squalius carolitertii, Cobitis atlantica, Gasterosteus aculeatus, and resident Salmo trutta, alongside diadromous species, namely Chelon ramada, Petromyzon marinus, Alosa spp., migrant Salmo trutta and Anguilla anguilla. Exotic species accounted for 48.9% of the total catch, with four non-native taxa being recorded: Lepomis gibbosus, Micropterus salmoides, Carassius auratus and Gobio lozanoi. This reflects the extent of the biological invasion pressure on this system. Analysis of the stomach contents of Salmo trutta revealed active predation of non-native species. Plastic debris was detected in 1.1% of Salmo trutta stomachs, which evidences that anthropogenic pollution has reached freshwater feeding habitats. The first recorded instance of the invasive nematode Anguillicola crassus in the Lima River, where 84.8% of the eels sampled exhibited moderate-to-severe swim bladder damage, highlights the vulnerability of native species to biological invasions. Conclusions: Biometric analyses and condition factors suggest that the fish community is under cumulative anthropogenic stress, caused by factors including river fragmentation due to three dams and traditional fishing weirs. The near-equal representation of native and exotic species in catches indicates that the freshwater fish community is under significant invasion pressure, which has direct consequences for the conservation of the native ichthyofauna. These findings establish a crucial baseline for the evidence-based management of an Iberian river system that is ecologically important but data-poor. Full article

Neuroimmune interactions in the intestine are essential for maintaining tissue homeostasis, yet they remain poorly understood in teleost fish. This study investigated the structural and cellular organization of enteric neurons and immune cells in the intestine of goldfish (Carassius auratus) using semithin histology, transmission electron microscopy (TEM), and confocal immunofluorescence. Histological observations revealed a well-organized epithelium composed of enterocytes and goblet cells, with numerous lymphocytes located in the basal epithelium. Prominent gut-associated lymphoid tissue (GALT) was identified in both scattered and aggregated forms within the lamina propria and submucosa. Macrophages were widely distributed throughout all intestinal layers and were consistently found in close proximity to enteric neurons and nerve fibers. Ultrastructural analysis confirmed direct contacts between macrophages and neuronal elements. These macrophages exhibited typical phagocytic features, including lysosomes, vacuoles, and engulfed material, particularly in association with myenteric nerve fibers. Immunofluorescence analysis revealed strong expression of toll-like receptor 2 (TLR2) and major histocompatibility complex class II (MHC II) in macrophages and enterocytes, suggesting an active role in antigen recognition. Langerin-positive dendritic-like cells were identified in the submucosa, while CD4-positive lymphocytes showed partial colocalization with serotonin (5-HT). S100-positive cells also exhibited partial overlap with 5-HT, and goblet cells demonstrated serotonin immunoreactivity. In addition, inducible nitric oxide synthase (iNOS) colocalized with TLR2 in submucosal immune cells. These findings demonstrate a close structural and functional association between enteric neurons and immune cells, highlighting an integrated neuroimmune network in the goldfish intestine. Full article

Neolissochilus heterostomus, a cyprinid fish endemic to Yunnan Province, China, is highly valued for both ornamental and edible purposes, yet its wild populations are currently declining and classified as endangered. In this study, we present a chromosome-level genome assembly of N. heterostomus, utilizing the PacBio HiFi and Hi-C strategies. The assembled genome spans 1793.99 Mb and is anchored to 50 chromosomes, comprising a total of 50,203 genes. Genomic features and chromosomal karyotype data recorded in the present study are consistent with an allotetraploid origin for N. heterostomus. Comparative genomics shows that N. heterostomus shares a close phylogenetic relationship with another allotetraploid fish, the common carp Cyprinus carpio. In total, 4687 expanded and 1365 contracted gene families were identified in N. heterostomus. Further enrichment analyses indicated an overrepresentation of metabolism-related pathways among the expanded and positively selected gene families, whereas the contracted gene families were enriched in reproduction- and embryonic development-related pathways. Reproductive observations further indicate that N. heterostomus produces fewer eggs than other cyprinid species characterized by relatively long embryonic development periods (106.1 h; accumulated temperature: 2260.6 °C·h), including common carp, goldfish (Carassius auratus), grass carp (Ctenopharyngodon idella), pond loach (Misgurnus anguillicaudatus), and blunt snout bream (Megalobrama amblycephala). These findings suggest a potential association between metabolism-related genomic features and reproductive traits, although functional validation remains necessary. Overall, this study may offer insights into the polyploidization, metabolic, and reproductive traits of N. heterostomus, thereby providing genomic and biological resources that may support future studies relevant to the conservation and management of this endangered species. Full article

Mori Cortex Radicis (MCR), which is abundant in resources and low in cost, is a Chinese herbal medicine with antitussive, anti-inflammatory, analgesic, and hypoglycemic effects; however, its application in the prevention and control of aquatic pathogens remains understudied. In this study, a MCR water extract (MCR-WE) was prepared, and its contents of polysaccharides, polyphenols, and proteins were found to be 0.63%, 1.17%, and 2.79%, respectively. LC-MS metabolomics revealed that L(+)-Arginine, 9,12,13-Todea, Citric acid, 1-Deoxynojirimycin, and 4-Guanidinobutanoic acid were the most abundant compounds. Subsequently, by feeding the MCR-WE to crucian carp (Carassius auratus) and challenging them with Aeromonas veronii, it was found that the MCR-WE enhanced the activities of immune factors (AKP, ACP, LZM) and the phagocytic activity of leukocytes (p < 0.05). Furthermore, the MCR-WE improved the survival rate of crucian carp (p < 0.05), reduced the bacterial load in the kidneys (p < 0.05), decreased the mRNA expression of inflammatory factors (IL-6, IL-1β, TNF-α), and lowered the expression levels of antioxidant-related factors (CAT, GSH-Px, SOD, MDA) and the mRNAs of oxidative stress pathway factors (Nrf2, HO-1, Keap1) (p < 0.05). Histopathological sections and immunofluorescence assays showed that the MCR-WE maintained the structural integrity of internal organs and reduced renal cell apoptosis and DNA damage. Therefore, MCR-WE is rich in immunologically active substances, can activate the immune response of crucian carp, reduce fish mortality, exert anti-inflammatory and antioxidant activities, and maintain the structural and functional integrity of internal organs. Thus, the MCR-WE holds promise as a therapeutic agent against A. veronii infection in fish. Full article

Methionine (Met) and lysine (Lys), as primary limiting amino acids, play important roles in regulating muscle quality in aquatic animals. This study investigated the effects of dietary Met and Lys supplementation on the growth performance, antioxidant function, and muscle quality of Hefang crucian carp (HCC) using physiological and transcriptomic analyses. Fish were fed three diets for 8 weeks: a basal diet (LA) and two diets supplemented with DL-methionine at 1.7% (MA) and 3.4% (HA), respectively, while L-lysine supplementation was fixed at 3.4%. The results indicated that dietary Met and Lys supplementation had no significant effect on the growth performance of HCC (p > 0.05), but significantly reduced serum triglyceride (TG) and cholesterol levels (T-CHO) (p < 0.05). Additionally, serum total protein (TP) content was significantly increased in the MA group (p < 0.05). Analysis of serum antioxidant enzyme activities indicated that appropriate Met and Lys supplementation improved antioxidant capacity and upregulated the expression of antioxidant-related genes (Nrf2, GPX1a, GSTO1, GSTP1) in the muscle. Moreover, the MA group exhibited superior muscle hardness and gumminess, while the HA group had higher springiness and chewiness (p < 0.05). Muscle fiber density was significantly increased, whereas diameter and area showed opposite trends in fish fed 1.7% Met and 3.4% Lys (p < 0.05). Furthermore, appropriate Met and Lys supplementation significantly affected muscle fiber development genes (MyoD, MyoG, and MRF4), with MyoG highest in the HA group and MyoD and MRF4 highest in the MA group (p < 0.05). Comparative transcriptomic analysis of muscle tissue showed DEGs were mainly enriched in pathways correlated with muscle quality, involving cardiac muscle contraction, actin cytoskeleton regulation, PPAR signaling pathway and ECM–receptor interaction. Taken together, our findings enhance the understanding of the molecular mechanisms underlying the effects of dietary Met and Lys on muscle quality in HCC, providing valuable insights for the development of nutritional strategies in the aquaculture industry. Full article

Saline-alkaline water is increasingly used for aquaculture. Qihe crucian carp (Carassius carassius) is one of the major economic aquacultural species in China; however, the impact of saline-alkaline water on this fish remains unclear. In this study, a 60 d chronic alkalinity stress experiment was conducted to investigate the effects on the growth, physiology, and muscle quality of Qihe crucian carp. One hundred and eighty juvenile fish (31.03 ± 0.71 g) were divided into three treatments (three replicate tanks per treatment, 20 fish per tank): a control group (freshwater), a CA20 group (20 mmol/L), and a CA40 group (40 mmol/L). Despite no effect on survival, alkalinity stress significantly impaired growth performance in both the CA20 and CA40 groups, leading to reductions in final body weight, weight gain rate, and specific growth rate. Similarly, the feed efficiency decreased with increasing alkalinity. Compared to the control group, the alkalinity groups exhibited elevated serum Na⁺ levels and higher gill Na⁺/K⁺-ATPase activity, but reduced Ca²⁺/Mg²⁺-ATPase activity. For histology, chronic alkalinity stress induced several changes in the gills, including wider filaments, shortened lamellae, and the increase in interlamellar distance. Regarding muscle nutritional composition, the contents of crude protein and amino acids and the proportions of polyunsaturated fatty acids showed a downward trend with rising alkalinity. Additionally, alkalinity stress significantly decreased muscle fiber density and hardness. Taking into account both growth performance and muscle quality, the suggested aquacultural alkalinity should be controlled below 20 mmol/L for Qihe crucian carp. In conclusion, these findings supported Qihe crucian carp as a promising candidate species for saline-alkaline water aquaculture, providing a scientific basis for the utilization of this special water resource. Full article

Aquaponics is a resource-efficient agricultural system, yet its overall productivity is frequently constrained by micro- and macronutrient deficiencies, particularly iron (Fe) and potassium (K). Currently, the efficacy of combined dietary Fe and K supplementation in optimizing nutrient management in these systems remains unclear. Therefore, a 60-day feeding trial was conducted to evaluate the effects of four dietary Fe and K levels—CK (basal diet without added Fe or K), T1 (Fe 0.1 g/kg + K 2.5 g/kg), T2 (Fe 0.2 g/kg + K 5.0 g/kg), and T3 (Fe 0.3 g/kg + K 7.5 g/kg)—on the growth and quality of lettuce (Lactuca sativa) and the physiological responses of crucian carp (Carassius auratus). The results demonstrated that the T2 treatment was suitable for enhancing system productivity. Compared with the CK group, the lettuce plant height, biomass, and net photosynthetic rate in the T2 group exhibited marked increases of 25.3%, 16.0%, and 26.4%, respectively. Furthermore, the vitamin C content increased by 52.2%, while the nitrate content notably declined by 32.2%. Plant nutrient analysis revealed that the combined Fe and K supplementation markedly promoted the foliar uptake of P, Mn, and Zn (peaking in the T2 group), whereas Cu and S contents increased linearly with the supplementation dose, reaching its maximum in the T3 group. Regarding fish health, the weight gain rate (WGR) of crucian carp in the T2 group peaked at 41.0%, and the feed conversion ratio (FCR) improved to 1.76. Additionally, the dietary supplementation maintained the stability of water quality parameters of the recirculating system. These findings indicate that a combined dietary inclusion of 0.2 g/kg Fe and 5.0 g/kg K can simultaneously enhance the yield and quality of both plants and fish. This approach provides a novel optimization strategy for mitigating acute water quality shocks, while also highlighting the inherent boundaries of competitive ion antagonism in aquaponic nutrient management. Full article

The accumulation of microplastics in aquatic ecosystems poses a significant threat to fish physiology and welfare. This study investigated the impact of exposure to virgin polystyrene microplastics (15 µm) on energy balance and welfare in goldfish (Carassius auratus). Fish were exposed for 14 days, and the effects were assessed through an integrated analysis of behavioral, metabolic, neuroendocrine, and physiological parameters. Microplastic exposure significantly reduces feed intake and feed anticipatory activity, indicating a potent anorexigenic effect. This effect was driven by neuroendocrine disruption, characterized by the downregulation of orexigenic neuropeptides (npy, agrp, hcrt) and the upregulation of anorexigenic signaling (pomca, cartpt, lepa). Simultaneously, exposed fish exhibited increased oxygen consumption, suggesting elevated metabolic demands. These factors converged to impaired growth and reduced hepatosomatic index, suggesting altered energy allocation. Furthermore, microplastic exposure induced anxiety-like responses and increased plasma cortisol levels, confirming the activation of the physiological stress response. Overall, these findings demonstrate that microplastics disrupt energy homeostasis and trigger behavioral shifts that ultimately compromise fish welfare and the biological resilience of aquatic species. Full article

Circular RNAs (circRNAs) exhibit significant sex- and development stage-specific expression patterns in the gonads of various fish species, yet their functions and regulatory mechanisms in male reproductive development remain largely unexplored in crucian carp (Carassius auratus). In this study, we characterized the expression features and biological functions of circSPEF2, a circular RNA derived from the reproduction-related gene spef2. Our results showed that circSPEF2 expression was markedly elevated in mature testes and progressively upregulated during gonadal maturation. Functional studies suggested that circSPEF2 likely does not act through a ceRNA-dependent mechanism. Transcriptome sequencing following circSPEF2 overexpression identified 45 upregulated and 70 downregulated differentially expressed genes, with GO and KEGG enrichment analyses revealing significant alterations in multiple gonadal development-related genes and signaling pathways. Subsequent siRNA-mediated knockdown of circSPEF2, combined with qRT-PCR validation, confirmed that circSPEF2 positively regulates the expression of genes associated with cell maturation and differentiation, including prdm1a, lamc2, and slc25a27, while concurrently suppressing that of proliferation- and apoptosis-related genes such as wnt8b, cpeb3, and bcl2l11. Furthermore, RNA pull-down combined with mass spectrometry identified three candidate circSPEF2-binding proteins, namely, hnRNP A/B, SRSF2, and CFAP263. Collectively, these findings indicate that circSPEF2 plays an important role in male gonadal development in fish and provide new insights into the post-transcriptional regulatory mechanisms underlying vertebrate male reproduction. Full article

To understand the distribution characteristics of the fish community and evaluate the effectiveness of the Yangtze River fishing ban, this study selected the Fuhe River (an important tributary of the Yangtze River) as the research area. A total of 30,892 fish (belonging to seven orders, 20 families, and 92 species) were captured in the upper and middle reaches of the Fuhe River from 2022 to 2024. Among them, the Cypriniformes order accounted for the largest proportion, with nine families and 66 species, making up 71.74% of the total number of fish. According to the relative importance index, Carassius auratus was the dominant species for each sampling period and each sampling area. Moreover, the number of dominant species in the main streams was significantly higher than that in the tributaries, while the diversity of the fish community in the tributaries was significantly greater than that in the main streams. Additionally, ANOSIM revealed significant spatial differences in the fish community (p < 0.01). Cluster and NMDS analyses further divided the fish community into three groups. SIMPER indicated that the typical species of each group of fish community were basically the dominant species within that community. Furthermore, RDA indicated that potassium permanganate, ammonia nitrogen, total phosphorus, and chlorophyll a were the main water environmental factors affecting the fish community structure. Compared to the fish community before the fishing ban, the stability of the fish communities during the initial stage of the fishing ban was significantly improved, and the number of fish species also increased. Therefore, the fishing ban was beneficial for enhancing the diversity and stability of the fish community. However, compared with the composition of fish species before the fishing ban, a certain number of fish species in the upper and middle reaches of the Fuhe River were still not collected during the early stage of the fishing ban. Therefore, the ten-year fishing ban in the Yangtze River still needs to be continued and implemented. Full article

Yangtze finless porpoise (Neophocaena asiaeorientalis) is the only extant cetacean species in the Yangtze River, a national first-class protected wild animal in China, and a key indicator reflecting the health status of the Yangtze River ecosystem. Environmental changes can induce adaptive trophic responses in animal communities; thus, clarifying the dynamic interactions between fish assemblages and dietary shifts in the Yangtze finless porpoise after the fishing moratorium is critically important. In this study, fishery resources in Poyang Lake were surveyed using triple-layer composite gill nets and cage traps, with samples collected and analyzed accordingly. A total of 81 fish species belonging to 8 orders and 16 families were recorded. Following the fishing ban, the abundance of small-bodied fish species (e.g., Hemiculter bleekeri, Carassius auratus) decreased, while the proportion of piscivorous species among the top ten dominant fish increased from 40% to 60%. DNA barcoding was used to analyze gastric contents of 10 dead porpoises found post-moratorium, and the results were compared with pre-ban data. Gastric content analysis identified 11 prey taxa, and comparative analysis demonstrated that prey selectivity was closely correlated with local prey availability. Concomitant with the structural reorganization of the fish community in Poyang Lake during the early stage of the fishing ban, the Yangtze finless porpoise exhibited adaptive dietary shifts toward benthic and small-bodied fish species, suggesting a potential linkage between these ecological responses. These findings provide direct implications for formulating targeted conservation strategies for this endangered cetacean and highlight the necessity of protecting small and benthic fish populations to ensure their long-term survival. Full article

Background/Objectives: The frequent use of antibiotics has led to increasing drug resistance in Aeromonas hydrophila; therefore, there is an urgent need to develop novel antimicrobial agents to prevent and control bacterial diseases in aquaculture. Allicin E (ALE) is derived from garlic (Allium sativum L.), a plant extensively used in traditional medicine for treating infections. This study aimed to evaluate the potential of ALE against A. hydrophila, a major aquaculture pathogen, by investigating its antibacterial efficacy, mechanisms of action, and in vivo protective effects. Methods: The minimum inhibitory and bactericidal concentrations (MIC/MBC) were determined by broth microdilution. Antibacterial mechanisms were investigated through ROS detection, electron microscopy, fluorescent staining, and content leakage measurement. In vivo efficacy was evaluated in Carassius auratus gibelio by monitoring survival rates and bacterial loads, analyzing immune and antioxidant biomarkers, and histopathological analysis after A. hydrophila challenge. Results: ALE exhibited potent antibacterial activity (MIC = MBC = 8 μg/mL), achieving complete bacterial elimination within 1 h and showing a low resistance propensity. Mechanistically, ALE induced ROS accumulation, causing oxidative damage that disrupted membrane integrity and facilitated the leakage of cellular contents. In vivo, ALE significantly enhanced fish survival, reduced bacterial loads, modulated inflammatory cytokines, boosted antioxidant enzyme activities (SOD and CAT), and alleviated tissue damage. Conclusions: ALE possesses potent in vitro antibacterial activity and exerts an inhibitory effect on bacteria-induced inflammatory responses, effectively combating A. hydrophila through a multi-target mechanism and enhancing host resistance. Full article

This study evaluated the efficacy of ammonia-nitrogen-reducing biofilms (aquatic nitrifying bacteria biofilm media, a fixed-bed biofilm capable of simultaneous nitrification and denitrification) in mitigating water quality deterioration and transport-induced physiological stress in live-transported Crucian carp (Carassius auratus). In a simulated bag transport system, the application of the biofilm significantly decreased ammonia-nitrogen concentrations through enhanced nitrification, stabilized pH and dissolved oxygen dynamics, and suppressed nitrite accumulation. Correspondingly, biofilm-treated fish exhibited significantly reduced systemic stress responses, as evidenced by reduced serum cortisol, glucose, and lactate dehydrogenase concentrations, along with diminished histopathological changes in gill and liver tissues and preserved muscle fiber integrity. Regarding post-transport muscle quality, biofilm treatment delayed glycogen catabolism and lactate accumulation, maintained elevated muscle pH and water-holding capacity, reduced shear force decline, decelerated ATP hydrolysis and freshness degradation (K-value), and simultaneously suppressed lipid peroxidation and myonuclear apoptosis. These findings demonstrate that ammonia-nitrogen-reducing biofilms represent a viable biotechnological approach for maintaining water quality, mitigating stress-induced physiological disturbances, and preserving flesh quality during live fish transportation. This approach has significant potential for improving post-harvest outcomes in aquaculture logistics. Full article

Background: Aeromonas veronii is an important bacterial pathogen in crucian carp and can cause serious disease outbreaks and substantial economic losses in aquaculture. Objectives: To evaluate how A. veronii infection and its inactivated vaccine modulate immune responses in Carassius auratus. Methods: 270 juveniles were allocated into three groups: a saline-injected control group (Ctrl), a vaccination group receiving an inactivated A. veronii vaccine (Vac), and an artificial infection group (AIG) subjected to stimulation. Liver, spleen, head kidney, gill, and intestine samples were collected from fish after anesthesia. The relative transcript levels of IgM, IgD, BAFF, MHCII, CD4, BCL6, MyD88, and NF-κB were quantified. For liver transcriptome analysis, the effective library concentration was determined. And the 16S rRNA gene resulting reads of fish gill symbiotic microbiota were processed for downstream bioinformatic analysis. Results: The results showed that the Vac achieved an RPS of 73.33%, and vaccination significantly upregulated multiple immune-related genes in different fish organs. With BAFF transcription across organs emerging as a robust sentinel readout. The Pearson correlation coefficient (r) of BAFF between other genes were all ≥0.8. GO and KEGG enrichment analyses indicated that AIG had more DEGs than Vac (5885 vs. 4008) and Ctrl (6910 vs. 6178), respectively. Some genes in AIG revealed significant over-representation of immune pathways, such as BCL6, MyD88, and NF-κB. The fish gill microbiota comprised a diverse set of low-abundance taxa, the phylum level was dominated by Proteobacteria and Fusobacteriota across all groups; whereas, the Vac group remained broadly closer to the Ctrl group in overall composition. Conclusions: These results indicated marked post-challenge immune–metabolic coupling in the liver, and suggested coordinated immunophysiological interplay between the liver and the spleen. Gill microecology of symbiotic bacteria was affected by vaccination or challenge reactions, which in turn affects the health of the gills or the organism itself. Full article