Healthy Fish Research Articles

Mucosal Exosome Proteomics of Hybrid Grouper Epinephelus fuscoguttatus♀ × E. lanceolatus♂ Infected by Pseudomonas plecoglossicida

Pseudomonas plecoglossicida infection, which causes visceral white spot disease, is a significant and economically devastating disease in aquaculture. In this study, we investigated the impact of bacterial infection on the protein composition of exosomes derived from the surface mucus of the hybrid grouper Epinephelus fuscoguttatus♀ × E. lanceolatus♂. Two hundred healthy fish were randomly separated into challenge and control groups. Fish from the challenge group received 103 CFU/g of the bacterial pathogen P. plecoglossicida via intraperitoneal injection, while sterile PBS was used as a negative control. After injection, the mucus was collected and the exosomes were extracted for proteomic analysis. The results of proteomic analysis revealed that P. plecoglossicida infection significantly increased the levels of innate immune proteins, including lysosomal and peroxisomal proteins, within the exosomes. Furthermore, the CAD protein was found to play a pivotal role in the protein interaction networks involved in the response to P. plecoglossicida infection. Intriguingly, we also observed a significant increase in the levels of metal-binding proteins within the exosomes, providing important evidence of nutritional immunity on the surfaces of the fish hosts. Notably, several proteins, such as plasma kallikrein, Annexin A5, eukaryotic translation initiation factor 3 subunit M, and S-methyl-5-thioadenosine phosphorylase, exhibited a remarkable increase in abundance in exosomes after infection. These proteins show promising potential as noninvasive biomarkers for the diagnosis of visceral white spot disease. The study contributes to the understanding of the host response to P. plecoglossicida infection and may aid policymakers in implementing appropriate intervention measures for effective risk management of this devastating disease.

Application of AMIS-optimized vision transformer in identifying disease in Nile Tilapia

Efficient health monitoring in Nile tilapia aquaculture is critical due to the substantial economic losses from diseases, underlining the necessity for innovative monitoring solutions. This study introduces an advanced, automated health monitoring system known as the “Automated System for Identifying Disease in Nile Tilapia (AS-ID-NT),” which incorporates a heterogeneous ensemble deep learning model using the Artificial Multiple Intelligence System (AMIS) as the decision fusion strategy (HE-DLM-AMIS). This system enhances the accuracy and efficiency of disease detection in Nile tilapia. The research utilized two specially curated video datasets, NT-1 and NT-2, each consisting of short videos lasting between 3–10 s, showcasing various behaviors of Nile tilapia in controlled environments. These datasets were critical for training and validating the ensemble model. Comparative analysis reveals that the HE-DLM-AMIS embedded in AS-ID-NT achieves superior performance, with an accuracy of 92.48% in detecting health issues in tilapia. This system outperforms both single model configurations, such as the 3D Convolutional Neural Network and Vision Transformer (ViT-large), which recorded accuracies of 84.64% and 85.7% respectively, and homogeneous ensemble models like ViT-large-Ho and ConvLSTM-Ho, which achieved accuracies of 88.49% and 86.84% respectively. AS-ID-NT provides a non-invasive, continuous, and automated solution for timely intervention, successfully identifying both healthy and unhealthy (infected and environmentally stressed) fish. This system not only demonstrates the potential of advanced AI and machine learning techniques in enhancing aquaculture management but also promotes sustainable practices and food security by maintaining healthier fish populations and supporting the economic viability of tilapia farms.

Leveraging the Red List of Ecosystems for action on coral reefs through the Kunming‐Montreal Global Biodiversity Framework

AbstractCountries have committed to conserving and restoring ecosystems after signing the Kunming‐Montreal Global Biodiversity Framework (GBF). The IUCN Red List of Ecosystems (RLE) will serve as a headline indicator to track countries' progress toward achieving this goal. Using Kenyan coral reefs, we demonstrate how nations implementing the GBF can use standardized estimates of ecosystem degradation from RLE assessments to support site‐specific management decisions. We undertook a reef‐by‐reef analysis to evaluate the relative decline of four key ecosystem components over the past 50 years: hard corals, macroalgae, parrotfish, and groupers. Using the two benthic indicators, we also calculated standardized estimates of state to identify reef sites which maintain a better condition through time relative to adjacent sites. Kenya's coral reefs have degraded across all four ecosystem components. At more than half the monitored sites parrotfish and grouper abundance declined by more than 50%, while coral cover and macroalgae‐coral ratio declined by at least 30%. This resulted in an Endangered threat status for coral reefs in Kenya (under criterion D of the RLE). The results can guide management actions related to 9 of the 23 GBF targets. For example, we identified several sites with relatively healthy benthic and fish communities as candidate areas for protection measures under Target 3. The RLE has a key role to play in monitoring and meeting the goals and targets of the GBF, and our work demonstrates how using the wealth of data within these assessments can inform local‐scale ecosystem management and amplify the GBF's impact.

The impact of apple cider vinegar on nonalcoholic fatty liver disease in rainbow trout, Oncorhynchus mykiss: A study of therapeutic potential and health benefits

AbstractIn this study, we aimed to experimentally induce fatty liver disease in rainbow trout, Oncorhynchus mykiss, and then assessed the illness recovery process, growth, and changes in the expression of FAAH and ACADL genes in both healthy (0 [C2] and 4% apple cider vinegar [T4]) and diseased fish (0 [C1], 1 [T1], 2 [T2], and 4% [T3]) apple cider vinegar. To conduct the study, 180 rainbow trout were randomly assigned to six different experimental treatments, each with three replications. The investigation lasted for 60 days. Growth indices, liver histology, blood biochemical parameters, and transcription of the ACADL and FAAH genes in the liver tissue were measured. The study found no significant differences in the final weights across all the treatments. Apple cider vinegar (ACV) administration resulted in a decrease in AST, ALT, and ALP; however, these values did not show a significant difference from C2. In T3, triglycerides significantly decreased (p < 0.05), whereas in T4, triglycerides significantly increased (p < 0.05). Hepatocytes from ACV‐containing treatments showed reduced fat compared with T4 and the control group (C1). While there was a significant difference (p < 0.05) in the expression of the FAAH gene, there was no significant difference (p > 0.05) in the expression of the ACADL gene between experimental treatments. The findings of our study indicate that an inclusion of up to 2% ACV may have positive effects on trout aquaculture and NAFLD treatment.

Acceptability of Bangus-Clam Sisig

Milkfish is one of the healthy and nutritious fish available, and it is loaded with omega-3 fatty acids and protein, which are essential for the proper functioning of the body. Mud clams, on the other hand, are rich in Vitamin B12, providing iron and additional protein. Mud clams, with their potential to regulate high blood pressure and support thyroid health, are a promising addition to any diet. Their rich content of riboflavin, choline, minerals, and vitamins, coupled with their low-fat content, make them a healthy choice. This study utilized bangus flakes and clam meat in varying proportions, combined with butter, garlic, chili, onion, liver spread, soy sauce, black pepper, annatto oil, oil, and salt. The objectives of the study were to develop a bangus-mud clam sisig product, evaluate its sensory characteristics (color, odor, taste, and texture) in different formulations, and determine whether there were significant differences in the acceptability of bangus-clam sisig across treatments. Moreover, the study aimed to identify the most preferred formulation (MPF) and assess consumer preferences. The development was performed in five (5) treatments with three (3) replications. The quality of the product was determined through sensory evaluation. The bangus-clam sisig had similar color, odor, taste, texture, and acceptability, regardless of the amount of bangus flakes and mud clam meat added to the formulated product. The addition of bangus and mud clam in the development of sisig, even in varying percentages, had no significant effect on the results in terms of color, odor, taste, and texture. However, during cooking, especially when pan-frying, the skin browns and crisps up. This contributed a significant amount of brown color to the overall dish. The results show that there was no significant difference in the overall acceptability of bangus-clam sisig, regardless of the amount of bangus and clam. All treatments were acceptable. Out of the five (5) treatments, the most preferred formulation consisted of 50% bangus and 50% mud clams. The findings show that most of the faculty employee and college students at the Capiz State University-Dayao Satellite College, preferred the bangus-clam sisig.

Growth, Feed Efficiency, and Health Status of Tilapia sp. Fed with New Technology Promoter Binder Fortified Diet

Developing a sustainable feed with minimal or no fishmeal in tilapia production is a challenge to this industry. New Technology Promoter Binder (NTPB), a guanidinoacetic acid, is a nutritional supplement to enhance the energy metabolism of the muscle and brain tissue of vertebrates. This study aimed to evaluate several plant-based diet formulations with zero and minimal use of fishmeal enriched with NTPB on the growth, feed efficiency, and health status of Tilapia sp. The experimental diets in this study were conducted based on four formulations (minimum fishmeal/FM and zero fishmeal/NFM-based diets) with 0, 0.6, and 1.2 mg·kg−1 feed of NTPB supplementation. The research indicated that the various diets given to tilapia affected the growth performance of fish in terms of growth parameters and feed efficiency. Tilapias fed with NTPB grew better than those without NPTB in both FM- and NFM-based diets. The addition of NTPB was safe for tilapia as demonstrated in the blood glucose, urea, and creatinine levels, which were normal for healthy fish. The viscerosomatic and hepatosomatic indexes of tilapia fed with the experimental diets showed no distinct differences. Adding NTPB to tilapia diets increased the hardness and amino acid contents of the tilapia’s muscle, which would benefit consumers.

The Growth Performance, Haematological Parameters and Serum Biochemistry of the Flathead Grey Mullet Mugil cephalus Under Recirculating Aquaculture System and Traditional Culture Systems.

The present investigation explored the growth performance, haematological parameters and serum biochemistry of flathead grey mullet under recirculating aquaculture system (RAS) and traditional culture systems. Nine hundred healthy fish, weighing 43.80 ± 3.55 g and length 16.54 ± 0.82 cm were randomly distributed to three treatments of RAS and traditional culture systems (T1: 20% of water changed daily; T2: once-through system 250 L/h; T3: RAS-20% of water changed weekly) in nine concrete tanks of 4000 L at stocking density of 100 fish/tank and each treatment had three replicates. Fish were fed (33.1% crude protein, 3 mm pellets) twice a day at a rate of 3% for 12 weeks. These findings suggest that the T3 followed by T2 led to notable improvements in growth performance compared to other culture systems. Significantly elevated values of weight gain, length gain, specific growth rate, average daily gain and survival % were observed in T3. The RBCs exhibited a significant decrease under T2. Haemoglobin concentrations and WBC counts significantly increased under RAS. Significant values of mean cell haemoglobin and mean cell haemoglobin concentration were recorded in T2. Total protein, albumin and globulin enhanced significantly under RAS, whereas the highest values of cortisol were observed in T2 and T3. These findings demonstrate that the RAS followed by once-through system significantly improve growth performance, feed efficiency and survival, as well as enhancing the haematology and serum biochemical status of flathead grey mullet. In conclusion, RAS provides ideal conditions for optimizing physiological functions, growth performance and fish health.

Genome-wide identification of the TRAF gene family in humpback grouper (Cromileptes altivelis) and analysis of their expression in response to Vibrio harveyi challenge

TRAF (Tumor necrosis factor receptor-associated factor) proteins are key mediators of signal transduction in cell signaling and immune regulation within the toll-like receptor (TLR) and tumor necrosis factor (TNFR) superfamily. Despite the importance of TRAF genes in teleost innate immunity, study on their functions in C. altivelis is limited. This study utilized bioinformatics methods to identify and named eight TRAF genes (CaTRAF2a, CaTRAF2a-like, CaTRAF2b, CaTRAF3, CaTRAF4a, CaTRAF5, CaTRAF6 and CaTRAF7) in C. altivelis. Phylogenetic, syntenic and molecular evolution revealed that all CaTRAF members were evolutionarily conserved in teleost. Domain analysis indicated the presence of a conserved N-terminal RING finger domain in all CaTRAF proteins. Most CaTRAF proteins also featured a MATH domain at the C-terminal, with the exception of CaTRAF7 which contained seven repeat WD40 domains. In addition, qRT-PCR was used to detect the expression patterns of nine different tissues and eight different embryonic development stages of healthy fish, and it was found that there were spatial and tissue specificities among the members. HE staining revealed evident pathological lesions in the tissues post V. harveyi infection. Atrophy and significant bending of the gill lamellae were observed in the gills, while irregular cell shapes, increased fat vacuoles, and enlarged cell volume were noted in the liver. Intestinal tissues displayed thickening of the muscle layer, elongation of intestinal villi, and increased folds. Moreover, the expression of TRAF gene changed significantly after V. harveyi infection. These results would help to clarify the molecular role of CaTRAF gene in the regulation of immune and inflammatory responses in C. altivelis.

Spatial distribution of bacterial communities driven by environmental factors in the sediment of Lateolabrax japonicus ponds

Dynamic changes of bacterial communities in the sediment are very important for preventing diseases and water quality in aquaculture ponds. In this study, bacterial communities in the sediment of Sea perch Lateolabrax japonicus, an important farmed fish in China, ponds were studied using 16S rRNA Illumina sequencing and functional gene array. At the phylum level, Pseudomonadota, Actinomycetota and Chloroflexota were the dominant species. The bacterial community composition was different in spatial variation. Among the environmental factors, the concentration of nitrogen related factors (TN, NO3−-N NH3-N, NO2−N) and total organic carbon was the main impact on the composition of bacterial community, especially denitrifying bacterial community. Nitrifying and denitrifying bacteria accounted for 4.81 %, and bacteria related to nitrogen cycle accounted for 18.36 %. Higher diversity of bacteria in healthy fish pond than that of the diseased fish pond. In the diseased fish pond, lower abundance of Nitrosospira and higher abundance of Nitrobacter were found, and the contents of NH3-N, NO2−-N and total organic carbon were significantly higher. This study would help to reveal that microbial community structure could reflect the health of cultured animal and surroundings, and it could provide a theoretical reference for the healthy environments in the sediment of Sea perch ponds in South China.

Bioaccumulation potentials of per-and polyfluoroalkyl substances (PFAS) in recreational fisheries: Occurrence, health risk assessment and oxidative stress biomarkers in coastal Biscayne Bay

Per-and polyfluoroalkyl substances (PFAS) are a group of synthetic, highly fluorinated, and emerging chemicals that are reported to be used for both industrial and domestic applications. Several PFAS have demonstrated persistent, bioaccumulative and toxic tendencies in marine organisms. Therefore, this research aims to characterize and quantify these compounds in both recreational fisheries and surface water samples, including estimating their bioaccumulation potentials. In addition, we assessed the potential contribution of biomonitoring tools such as oxidative stressors and morphological index on fish and ecological health. Finally, human health risk assessment was performed based on available toxicological data on limited PFAS. All PFAS were detected in at least one sample except for N-EtFOSAA in lobster which was below the method detection limit. ƩPFAS body burden ranged from 0.15 to 3.40 ng/g wet weight (ww) in blackfin tuna samples and 0.37–5.15 ng/g ww in lobster samples, respectively. Wilcoxon rank paired test (α = 0.05) shows that there is statistical significance (ρ < 0.05) of ƩPFAS between species. Bioaccumulation factors (BAF) suggest an increasing trend in PFAS classes (PFCAs < PFSAs < FTSs), with higher BAFs observed in tuna compared to lobster. Long-chain PFESAs and FASAA were reported at higher concentrations in lobster compared to Blackfin tuna due to their bioavailability through sediment-sorption interactions. Although Fulton’s condition factor (FCF) indicates healthy fish conditions, oxidative stress biomarkers suggest that tuna and lobster might be under stress, which can weaken their immune system against exposure to emerging contaminants such as PFAS. Hazard risk (HR) suggests a low risk to human health based on the consumption of the studied species; however, the risk of contaminant exposure may be higher than estimated. This study is aimed at improving food safety by providing better understanding of how PFAS infiltrate into human diet and incorporating data on influence of contaminant exposure and environmental stressors on marine health.

Bacillus Sp. as Potential Probiotics for Use in Tilapia Fish Farming Aquaculture – A Review

Abstract Aquaculture is a crucial and rapidly expanding industry in global food production. Fisheries are also an essential socio-economic activity, providing abundant resources and remarkable prospects. However, due to the deteriorating ecological environment, aquatic animals are often exposed to traumatic conditions and are susceptible to bacterial infections that pose significant challenges for aquaculture production. The indiscriminate use of antibiotics in the past has led to the emergence of multidrug-resistant pathogens and sudden outbreaks of infectious diseases, resulting in serious economic losses. Moreover, the use of expensive chemotherapeutic drugs and antibiotics has negative impacts on aquatic environments. Therefore, it is increasingly important to adopt alternative natural agents, such as probiotics and their metabolites, to enhance healthy fish production. Probiotics are microorganisms that have numerous beneficial effects on their hosts. They are environmentally friendly, non-toxic, and cost-effective. This review specifically focuses on the use of Bacillus sp. as probiotics to promote healthy tilapia production in the aquatic sector, while also examining their interactions with the immune system and gut micro-biota. The information presented in this review can guide future research and promote effective and healthy tilapia culture production.

A Convolutional Neural Network Approach for Precision Fish Disease Detection

Background: Detecting and classifying fish diseases is crucial for maintaining the health and sustainability of aquaculture systems. This study employs deep learning techniques, particularly Convolutional Neural Networks (CNNs), to automate the detection of various fish diseases using image data. Methods: The study utilizes a carefully curated dataset sourced from the Kaggle database, comprising images representing seven distinct types of fish diseases, along with images of healthy fish. Data preprocessing techniques, including resizing, rescaling, denoising, sharpening, and smoothing, are applied to enhance image quality and facilitate accurate disease detection. Data augmentation is employed to increase the model's ability to generalize to unseen data. The CNN architecture is designed with cascading convolutional layers, ReLU activation functions, and pooling operations to extract high-level features associated with fish infections. The model architecture, implemented using the Keras Sequential API, includes convolutional layers, max pooling layers, and densely connected layers for classification. Results: Experimental results demonstrated promising performance across various disease categories, with high accuracy and balanced precision and recall values for most classes. The study also discussed the impact of climate change on fish disease incidence and underscores the importance of effective monitoring and management practices facilitated by technological innovations such as Big Data, IoT, sensors, and robotics in ensuring sustainable fisheries management.

Development of improved technologies for protecting fish from infections in aquaculture

The current intensification of marine aquaculture is inevitably associated with such environmental issues as growing infections and the need to apply antibiotic and other antimicrobial preparations. This leads to antibiotic pollution in the environment. Latest technologies aimed at preventing fish infections in aquaculture are based on the vaccination of the objects under cultivation. These technologies allow the use of antibiotics to be reduced and the balance of the microbial environment in aquaculture to be restored, eventually minimizing the negative effects of antibiotic residues on the human health. In this work, we set out to study molecular mechanisms underlying the immune response of fish to viral infections. Data on the expression of some genes of the most important aquaculture objects in Russia and China in response to infection and during its progression was obtained. The research results can be used when developing vaccines against vibriosis with the purpose of minimizing the application of medical preparations, such as antibiotics. These measures are important for maintaining healthy fish habitats and, as a consequence, the human health.

Evaluation of the potential probiotic Bacillus subtilis isolated from darkbarbel catfish (Pelteobagrus fulvidraco) on growth performance, serum immunity, and disease resistance of Aeromonas hydrophila.

This study aimed to identify potential probiotic strains of Bacillus subtilis from healthy fish gut microbiota for application in aquaculture. The effects of dietary B. subtilis administration on growth performance, serum enzyme activity, immune gene expression, and disease resistance in darkbarbel catfish (Pelteobagrus fulvidraco) were investigated. The isolate, identified through gene sequencing and biochemical tests, demonstrated resilience to pH 3.0% and 6.0% bile, and exhibited extracellular protease, cellulose, lipase, and amylase production. Darkbarbel catfish were fed diets with varying B. subtilis concentrations (0 CFU/kg [T0], 107 CFU/kg [T1], 108 CFU/kg [T2], and 109 CFU/kg [T3]). After 8 weeks, significant increases (p < 0.05) were observed in final body weight, weight gain rate, specific growth rate, serum lysozyme, serum superoxide dismutase, alkaline phosphatase, and total antioxidant capacity, whereas malondialdehyde levels significantly decreased. Feeding darkbarbel catfish with B. subtilis diets increased immunoglobulin M (IgM) and C3 gene expression (p < 0.05), indicating a positive impact on the fish's immune system. The strain upregulated interleukin 10 (IL-10) and transforming growth factor-β (TGF-β) expression and downregulated TNF-α and IL-1β, suggesting potential anti-inflammatory effects. Following a 7-day challenge with Aeromonas hydrophila, fish fed with B. subtilis exhibited lower mortality, with higher survival rates in the T2 and T3 groups. In conclusion, supplementing darkbarbel catfish diets with B. subtilis effectively enhances growth performance, immune response, and disease resistance.

Characterization of IgD and IgT with their expressional analysis following subtype II megalocytivirus vaccination and infection in rock bream (Oplegnathus fasciatus)

In this study, heavy chain genes of IgD and IgT were sequenced and characterized their gene expression in rock bream (Oplegnathus fasciatus). Rock bream (RB)-IgD cDNA is 3319 bp in length and encodes a leader region, variable domains, a μ1 domain, and seven constant domains (CH1–CH7). A membrane-bound (mIgT) and secretory form (sIgT) of RB-IgT cDNAs are 1902 bp and 1689 bp in length, respectively, and encode a leader region, variable domains, four constant domains (CH1–CH4) and C-terminus. Their predicted 3D-structure and phylogenetic relation were similar to those of other teleost. In healthy fish, RB-IgD and mIgT gene expressions were higher in major lymphoid organs and blood, while RB-sIgT gene was more highly expressed in midgut. IgT expressing cells were detected in melano-macrophage centers (MMC) of head kidney in immunohistochemistry analysis. Under immune stimulation in vitro, RB-IgD and IgT gene expressions were upregulated in head kidney and spleen cells by bovine serum albumin or a rock bream iridovirus (RBIV) vaccine. In vivo, their expressions were significantly upregulated in head kidney, blood, and gill upon vaccination. Especially, RB-mIgT gene expression in head kidney and blood was upregulated at day 3 after vaccination while upregulated at earlier time point of day 1 by challenge with RBIV. This may suggest that memory cells might be produced during the primary response by vaccination and rapidly proliferated by secondary immune response by viral infection. RB-sIgT gene expression was highly upregulated in peripheral blood in vaccinated fish after viral infection, indicating that IgT plays an important role in systemic immune response as well as mucosal immune system. Our findings provide information on the role of RB-IgT in adaptive immunity during vaccination and viral infection in the vaccinated fish.

Identification of Aeromonas veronii as the Pathogen Associated with Massive Mortality in Bronze Gudgeon (Coreius heterodon).

Aeromonas veronii, an opportunistic pathogen toward aquatic organisms, was identified as the causative pathogen (isolate WH10) in diseased bronze gudgeon via bacterial isolation, and morphological, physiological, biochemical, and molecular characterization. WH10 exerted its pathogenicity via five virulence genes, including those encoding cytotoxic enterotoxins (act and alt), lipase (lip), a quorum sensing-controlled virulence factor (LuxS), and a Type III secretion system inner membrane component (ascV). WH10 was shown to be sensitive to compound sulfamethoxazoles, cefothiophene, doxycycline, and sulfamethoxazole. Toward bronze gudgeon, WH10 had a median lethal dose (LD50) of 1.36 × 106 colony forming units/mL. Analysis of blood parameters of diseased fish revealed significant increases in monocytes and neutrophils, but decreased numbers of lymphocytes. Serum aspartate aminotransferase activity and triglyceride concentration were significantly higher in diseased fish than in healthy fish. The reverse was noted for alkaline phosphatase, total protein, albumin, total cholesterol, and glucose. Thus, Aeromonas veronii is implicated as the causative agent of the mass mortality observed in bronze gudgeon, warranting further investigations into the diagnosis, epidemiology, prevention, and treatment of this infectious disease.

Effect of Physical Factors on Milt Quality of Malabar Grouper, Epinephelus Malabaricus in Summer and Winter Season

A study was conducted to test the effect of physical factors such as temperature, salinity, and pH on spermatozoa motility of Malabar grouper (Epinephelus malabaricus). Mature and healthy male fishes were collected from the Red Sea during the summer and winter seasons for milt collection. Milt quality was assessed for colour, volume, sperm cell concentration, motility, and viability. Sperm motility was tested under different water temperatures, salinity, and pH media. A significant difference (P &lt; 0.01) in sperm cell concentration (density), sperm motility (%), and viability (%) was observed between the summer and winter seasons. Changes in water temperature, pH, and salinity influenced sperm motility (%) and motility duration (min). Low pH and salinity caused adverse effects on spermatozoa motility. The results of the study are useful for the germplasm conservation of Malabar grouper, E.malabaricus.

Fishers’ knowledge indicates that collective benefits outweigh the individual costs of coexisting with dolphins

Understanding interactions between small-scale fishers and endangered dolphins is crucial for informing coexistence strategies. We investigated the perceptions and encounters of 123 Amazonian fishers in the Tapajós River (Brazil) with two endangered freshwater dolphins, Sotalia fluviatilis and Inia geoffrensis. Furthermore, 51 fishers self-documented 2,013 fish landings over one year. All interviewed fishers reported regular encounters with dolphins during fishing activities, with landings and interviews showing a partial overlap in fish species caught by fishers and cited as consumed by dolphins. Fishers highlighted that only I. geoffrensis disrupts fishing activities, causing gillnet damage and stealing fish from nets. To avoid interaction, fishers refrain from fishing an average of 3.7 times per month, potentially leading to 14.8 to 18.5 % decrease in total fish harvest. Economic losses were reported by 63 fishers, totaling an estimated US$ 50.3 ± 30.1 per month per fisher, which is equivalent to three days of fishing income. The estimated bycatch of dolphins was 10 per year across the studied area (71 % from I. geoffrensis). While 86 fishers considered dolphins beneficial, 62 viewed them as harmful. Fishers who fish more frequently are more likely to consider dolphins “good”. The results revealed dolphins’ positive contribution to fisheries by reducing efforts and safeguarding fish, while causing harm through gillnet damage. Negative perceptions are linked to individual economic losses, while positive perceptions stem from perceived collective benefits. By emphasizing dolphins’ collective advantages in riverine communities, they can be a flagship species for conservation, leveraging their appeal and function as umbrella species for maintaining ecosystem functions, such as healthy fish stocks.

Transcriptome Analysis Reveals the Immunosuppression in Tiger Pufferfish (Takifugu rubripes) under Cryptocaryon irritans Infection.

The tiger pufferfish (Takifugu rubripes), also known as fugu, has recently suffered from severe C. irritans infections under aquaculture environment, yet the underlying immune mechanisms against the parasite remain poorly understood. In this study, we conducted a comprehensive transcriptome analysis of the gill tissue from infected and uninfected fish using PacBio long-read (one pooled sample each for seriously infected and healthy individuals, respectively) and Illumina short-read (three pools for mildly infected, seriously infected, and healthy individuals, respectively) RNA sequencing technologies. After aligning sequence data to fugu's reference genome, 47,307 and 34,413 known full-length transcripts were identified and profiled in healthy and infected fish, respectively. Similarly, we identified and profiled 1126 and 803 novel genes that were obtained from healthy and infected fish, respectively. Interestingly, we found a decrease in the number of alternative splicing (AS) events and long non-coding RNAs (lncRNAs) after infection with C. irritans, suggesting that they may be involved in the regulation of the immune response in fugu. There were 687 and 1535 differentially expressed genes (DEGs) in moderately and heavily infected fish, respectively, compared to uninfected fish. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that immune-related DEGs in the two comparison groups were mainly enriched in cytokine-cytokine receptor interactions, ECM-receptor interactions, T-cell receptor signaling pathways, Th1 and Th2 cell differentiation, and Th17 cell differentiation pathways. Further analysis revealed that a large number of immune-related genes were downregulated in infected fish relative to uninfected ones, such as CCR7, IL7R, TNFRSF21, CD4, COL2A1, FOXP3B, and ITGA8. Our study suggests that C. irritans is potentially a highly efficient parasite that may disrupt the defense mechanisms of fugu against it. In addition, in combination of short-read RNA sequencing and previous genome-wide association analyses, we identified five key genes (NDUFB6, PRELID1, SMOX, SLC25A4, and DENND1B) that might be closely associated with C. irritans resistance. This study not only provides valuable resources of novel genic transcripts for further research, but also provides new insights into the immune mechanisms underlying C. irritans infection response in farmed fugu.

Metabolomics analysis of splenectomy of Nile tilapia (Oreochromis niloticus) reveals the spleen involved in regulating liver lipids and amino acids metabolism

The liver is essential for nutritional balance in fish, and liver damage in farmed fish often arises from factors like overfeeding, causing various health issues. Clinical observations indicate that liver diseases frequently involve spleen dysfunction, and there is evidence to suggest that the spleen has a significant impact on liver function. However, there has been no discussion on the role of the spleen in maintaining liver health in fish. To understand the role of fish spleen in liver metabolism, this study selected Nile tilapia (Oreochromis niloticus) as the experimental material and first established a tilapia splenectomy model. Various biochemical parameters of the liver and serum were measured, and the liver metabolism characteristics of the splenectomy group (SP group) and the sham operation group (SO group) were analyzed using metabolomics. After splenectomy, biochemical parameters of the liver and serum showed abnormalities, including significant increases in total cholesterol (T-CHO) and serum total bile acid (TBA) levels, alongside a significant decrease in liver TBA levels, suggesting impaired metabolic function and cholesterol deposition in the liver. Metabolomics analysis showed that metabolites such as lipids, lipid-like molecules, and organic acids and derivatives were differentially regulated between the SO and SP group. KEGG analysis showed that differential metabolites were enriched in lipid metabolism and amino acid metabolism. The metabolic pathway analysis of differential metabolites showed that after splenectomy, the low-activity urea cycle in the liver may accelerate lipid synthesis, while low concentrations of aromatic amino acids and taurine may inhibit lipid catabolism. These results indicate that after splenectomy, the liver metabolic capacity is impaired, which causes abnormal lipid metabolism by interfering with amino acid metabolism, making splenectomy tilapia liver at risk of liver disease, including cholesterol deposition, hepatic steatosis and nonalcoholic fatty liver disease (NAFLD). Our results show that the spleen is involved in regulating liver lipid and amino acid metabolism, and the spleen may interfere with lipid metabolism by regulating liver amino acid metabolism. Our data can provide support for further research on liver and spleen functions and the immune-nutrient metabolism mechanisms in fish, as well as new ideas for healthy fish farming.