Search Results (154)

Overexploitation has led to a rise in pathogenic bacteria within aquaculture, increasing reliance on antibiotics, and developing microorganism resistance. This situation underscores the need to explore alternatives with a reduced ecological impact. Metabolites derived from essential oils have demonstrated antimicrobial properties that can inhibit or diminish the activity of various microorganisms. In this study, the antimicrobial efficacy of cinnamon (Cinnamomum zeylanicum), tea tree (Melaleuca alternifolia), and thyme (Thymus vulgaris) essential oils against pathogenic bacteria (Aeromonas, Pseudomonas, Shewanella, Comamonas, Vibrio, Acinetobacter, and Empedobacter) isolated from tilapia (Oreochromis spp.) brooded in Hidalgo State, Mexico, were investigated. Diffusion tests were conducted using discs infused with 12 different antibiotics and discs infused with essential oils at concentrations of 15, 10, and 5 μL each. Minimal inhibitory concentration tests were performed using a 96-well microplate format. All bacterial strains exhibited multi-resistance to various antibiotics; however, thyme and cinnamon effectively inhibited the tested bacteria at the lowest concentrations, while tea tree oil was the least effective. The findings suggest the potential incorporation of thyme and cinnamon as an alternative prevention to decrease the use of antibiotic treatment. Full article

To address the growing global demand for aquatic protein and the need for sustainable aquaculture, this study explored Aspalathus linearis tea extract as a novel feed additive for Oreochromis mossambicus larvae. Over an eight-week feeding trial, the efficacy of diets supplemented with 30% fermented or green rooibos extract was assessed against a control. Both fermented and green rooibos treatments significantly (p < 0.05) enhanced larval growth, evidenced by improved weight gain and feed conversion ratios (fermented: 1.50 ± 0.25; green: 1.41 ± 0.07). Notably, A. linearis extracts also demonstrated genoprotective potential, as indicated by a marked reduction in micronucleus frequency, most likely attributed to their abundant phenolic compounds. These findings demonstrate that rooibos extract, especially the green variety, can improve growth performance and feed utilization, and also provide genoprotective benefits. The superior outcomes in growth and feed conversion are likely due to the bioactive phenolic compounds, which may enhance palatability, gut health, and nutrient absorption, rather than macronutrient content. This positions rooibos extract as a promising natural functional additive for aquafeed, offering a sustainable strategy to enhance tilapia farming productivity and resource utilization. However, further research is necessary to uncover specific molecular mechanisms, conduct in-depth analyses of gut health and immune responses, and evaluate effects on product quality to facilitate its sustainable and effective integration into aquaculture practices, thereby contributing to both fish health and food security. Full article

Effective surveillance of viral disease in fish populations is critical for disease control and the sustainable development of global aquaculture. Here, we evaluated the application and performance of pooled serum samples using an indirect ELISA based on recombinant segment 4 protein to assess farm-level immunity in tilapia infected with Tilapia lake virus (TiLV). The TiLV-S4 ELISA was developed using a recombinant nucleoprotein (segment 4) antigen, optimized through checkerboard titration, and validated for repeatability and reproducibility, with intra- and inter-assay coefficients of variation below 10%. A pooling strategy was used to combine multiple serum samples before testing for the presence of TiLV-specific antibodies using an enzyme-linked immunosorbent assay (ELISA). Our results showed that pooling five serum samples was effective for detecting TiLV-specific antibodies, particularly when multiple seropositive individuals were presented in the pool, supporting its application for population-level surveillance. However, ELISA sensitivity may be reduced when only one seropositive sample is included in the pool, due to the dilution effects. Despite this limitation, pooled testing yielded a high proportion of positive results, suggesting similar detection performance in many cases. Overall, the pooling strategy provides a cost-effective and time-efficient approach for large-scale monitoring of immune status in tilapia populations. Full article

Sulfamethoxazole (SMZ), a widely used broad-spectrum antibiotic in aquaculture, lacks comprehensive research on its residual elimination kinetics in tilapia. This study investigated SMZ residue depletion, withdrawal periods, and dietary risks in 1-year-old GIFT tilapia (Genetically Improved Farmed Tilapia Oreochromis niloticus) weighing 500 ± 50 g, following oral gavage administration of a loading dose (200 mg/kg BW on day 1) and then 100 mg/kg BW daily for 6 more days, at 22 ± 2 °C. Tissue samples (plasma, muscle, skin, liver, kidney, gill, and remaining tissues) were collected from five fish per time point at intervals from 0.33 to 30 days post-administration, with SMZ residues quantified via HPLC-MS/MS. Results revealed peak SMZ concentrations at 0.33 days (8 h), ordered as liver > skin > plasma > kidney > remaining tissues > gill > muscle. Muscle residues fell below the maximum residue limit (MRL, 100 μg/kg) by day 3, while skin required 10 days. Kidney residues dropped below the limit of detection (LOD) earliest (16 days), followed by muscle, gill, and remaining tissues (25 days), whereas plasma, liver, and skin retained detectable levels until day 30. Elimination equations for SMZ across tissues exhibited first-order kinetics. Based on the specific conditions of this study, a minimum 11-day withdrawal period is recommended for edible tissues (muscle + skin) after SMZ administration. Hazard quotient (HQ) values for all tissues remained below the safety threshold (HQ = 1), indicating low dietary risk. These findings support SMZ use standardization in tilapia aquaculture to ensure food safety compliance. Full article

The cage tilapia farming boom in Kenya’s Lake Victoria region underscores its role in food security and economic growth. Success depends on understanding producer and consumer behaviors within the value chain. Using the Theory of Planned Behavior (TPB), this study examines how attitudes (evaluations of farming/consumption), subjective norms (social pressures), perceived behavioral control (confidence in actions), environmental awareness, and moral obligation shape decisions. A survey of 66 producers and 169 consumers, analyzed via structural equation modeling (SEM), reveals key drivers. Producers are driven by positive attitudes toward profitability, technical feasibility, and sustainability, reinforced by community norms and resource access, promoting sustainable practices. Consumers prioritize health, affordability, and accessibility of cage-farmed tilapia, with environmental and ethical factors less influential. These findings highlight opportunities for targeted interventions to enhance production, boost demand, and ensure sustainable aquaculture. Full article

Effective sustainable fish farming necessitates enhanced models that incorporate environmental variability and contemporary monitoring methods. This research presents an innovative framework for assessing and modeling the environmental carrying capacity based on phosphorus (ECCp) in tropical and neotropical lakes and reservoirs. The model evaluates phosphorus waste from tilapia farming (Oreochromis niloticus) under diverse climatic conditions and production scenarios in cage systems. Using bioenergetic modeling and Monte Carlo simulations, we estimated phosphorus retention in fish and maximum production limits across different temperatures (21 °C, 25 °C, 29 °C) and dietary phosphorus concentrations (0.8%, 1.2%, 2.1%) in Brazil’s Chavantes reservoir. Results indicated that phosphorus retention diminished with higher dietary phosphorus and increased temperatures, ranging from 51% (0.8% P) to 20% (2.1% P). Phosphorus discharge ranged from 3.3 to 20.5 kg/ton of fish produced. The ECCp model forecasted an allowable production of roughly 40 tons per year at full operational capacity, reflecting a 41% increase compared to current regulations. The model’s accuracy (96%) surpassed that of traditional regulatory frameworks, which rely on static parameters, emphasizing the shortcomings of existing practices. The findings promote enhanced modeling strategies, sophisticated monitoring, adaptive management, and revised public policies to mitigate phosphorus emissions and support sustainable aquaculture in tropical and neotropical regions. Full article

Nile tilapia, as an ideal model for studying sex differentiation, is a popular farmed fish worldwide with a stable XX/XY sex-determination system. In tilapia, ovarian differentiation is triggered by estradiol-17β (E2) production in undifferentiated gonads. In a previous study, we suggested that follicle-stimulating hormone (FSH) signaling might be involved in ovarian differentiation in Nile tilapia. In this study, we further investigated the role of FSH signaling in ovarian differentiation via aromatase expression, which converts testosterone to E2. Masculinization of XX fry by aromatase inhibitor or 17α-methyltestosterone leads to suppression of fshr expression. Feminization of XY fry by E2 treatment increased fshr expression from 15 days after hatching, when E2 treatment was terminated. XX tilapia developed ovaries harboring aromatase expression if fsh and fshr were double knockdowns by morpholino-oligo injections. Finally, the transcriptional activity in the upstream region of the aromatase gene (cyp19a1a) was further increased by FSH stimulation when HEK293T cells were co-transfected with foxl2 and ad4bp/sf1. Collectively, this study suggests that the role of FSH signaling is not critical in tilapia ovarian differentiation; however, FSH signaling may have a compensatory role in ovarian differentiation by increasing cyp19a1a transcription in cooperation with foxl2 and ad4bp/sf1 in Nile tilapia. Full article

Nile tilapia (Oreochromis niloticus) is the most widely farmed tilapia species globally, making it one of the most important aquaculture species. To meet increasing demand, hatcheries occasionally use artificial breeding techniques such as hormonal induction to synchronize breeding. Despite the common use of human chorionic gonadotropin (hCG) in fish breeding, no detailed protocol has been established specifically for Nile tilapia. The objective of this study is to establish an effective hCG-induced artificial breeding protocol for gene editing and aquaculture production, optimizing fertilization, hatching, and survival rates. We employed a single intramuscular injection of 2 IU/g hCG to induce ovulation. The protocol achieved an average fertilization rate of 88.3% and a larval survival rate of 90.5%, demonstrating its potential for obtaining high-quality embryos for functional studies and enhancing reproductive performance on a commercial scale. Full article

This study highlights the significant environmental and health risks associated with heavy metal contamination (As, Cd, Cr, and Pb) in Oreochromis niloticus (Nile tilapia) from two locations: the Khon Kaen municipal landfill (study site) and the Thapra commercial fish farm (reference site). It also evaluates potential human health risks and investigates genotoxicity and oxidative stress markers, including malondialdehyde, hydrogen peroxide (H₂O₂), catalase (CAT), and superoxide dismutase (SOD) in fish. Heavy metal concentrations were analyzed using inductively coupled plasma optical emission spectrometry. To determine genetic differentiation, inter-simple sequence repeats with dendrogram construction and genomic template stability (%GTS) were applied. The results showed that the average concentrations of As, Cd, Cr, and Pb in water samples were 0.0848, 0.536, 1.23, and 0.73 mg/L, respectively. These values exceeded safety limits, and the average Cd in sediment (1.162 mg/kg) was above regulatory thresholds. In fish muscle, the average metal concentrations (mg/kg) followed the order Cr (1.83) > Pb (0.69) > Cd (0.096) > As (0.0758), with Pb exceeding food quality standards. The bioaccumulation factor ranked as Cr > Pb > As > Cd. Health risk assessments, including health risk index and carcinogenic risk, suggested Pb contamination poses significant health risks through fish consumption. From dendrogram results, the %GTS of O. niloticus from the landfill and reference sites were 46.34 to 71.67% and 87.34 to 96.00%, respectively. This suggests that fish from the landfill site exhibited greater genetic diversity compared to those from the reference site. Specific oxidative stress markers revealed higher levels of H₂O₂ and significantly lower activities of CAT and SOD in landfill O. niloticus than in the reference site. These results emphasize the urgent need for environmental monitoring, stricter pollution controls, and improved waste management strategies to protect aquatic ecosystems and human health. Full article

Tilapia (Oreochromis spp.) is a globally important farmed fish. Analyses of genetic variation across different types of tilapia are essential for the development of superior breeding populations. We investigated the genetic structures of breeding populations of blue tilapia (Oreochromis aureus) (OA), Nile tilapia (Oreochromis niloticus) (ON), and red tilapia (Oreochromis spp.) (OS) by whole-genome resequencing. The results showed that the OS population had maintained high genetic diversity but significant genetic differentiation from the OA population. Principal component analysis, phylogenetic analysis, and genetic clustering analysis revealed a clear pattern of genetic differentiation among the three populations. The genetic structure of the ON population differed from that of the OA population but was similar to that of the OS population. Population kinship analysis revealed a close relationship between the ON and OS populations. Selective scanning analyses of three comparison groups (OA vs. ON, OA vs. OS, and ON vs. OS) revealed population-selected regions related to metabolism, endocrine, and immune systems, harboring key genes (qrsl1, pde4d, hras, ikbkb, prkag1, prkaa2, prkacb, irs2, and eif4e2). These key genes were related to growth, reproduction, and disease resistance, indicating that breeding programs have selected for these traits. Due to the lack of stable morphological characteristics of juvenile fish and the changes in external environmental conditions that lead to changes in individual morphological characteristics, SNP fingerprints were successfully constructed for the identification of the three populations based on the differences in SNPs. Based on the five core SNP markers, two combinations of SNP markers were developed to accurately identify the three populations of tilapia at the genomic level. These results provide new information about tilapia genetic resources and reference data for identification and breeding purposes. Full article

The tilapia (Oreochromis) aquaculture industry in Malaysia has expanded rapidly to meet the increasing demand for animal protein. However, this growth is challenged by microbial infections, particularly those caused by the emerging pathogen Aeromonas dhakensis. This study aimed to investigate the microbial community composition across four distinct tilapia farming systems and assess associated water physicochemical parameters, with a focus on detecting the presence of A. dhakensis and elucidating its environmental associations. Water physicochemical parameters were measured to evaluate environmental conditions, microbial communities were characterized through 16S rDNA metabarcoding, and A. dhakensis was detected using both microbiological and molecular approaches. Principal component analysis (PCA) and canonical correspondence analysis (CCA) were employed to explore the influence of environmental variables and microbial community dynamics on pathogen occurrence. Our results indicated that floating cages exhibited higher levels of temperature, ammonium, and fecal coliform, while cement tanks showed signs of nutrient accumulation. PCA revealed that both systems were associated with degraded water quality. A total of 45 A. dhakensis strains with distinct fingerprints were isolated. The 16S metabarcoding revealed Proteobacteria, Actinobacteria, and Planctomycetota as the dominant phyla. Alpha diversity did not differ significantly among pond systems, while beta diversity revealed variations in microbial assemblages across aquaculture systems. CCA identified dissolved oxygen, temperature, macronutrients (phosphate, ammonium, nitrate, and nitrite), and turbidity as significant environmental drivers shaping the microbial community structure across the pond systems. In conclusion, this study highlights the importance of environmental factors, particularly dissolved oxygen, temperature, and nutrient levels, in shaping microbial community composition and potentially influencing the presence of pathogenic bacteria such as A. dhakensis. These findings underscore the need for improved environmental management in tilapia aquaculture to mitigate disease risks and support fish health. Full article

Background: Saline aquaponics integrates fish and crop cultivation in saltwater environments by utilizing abundant saltwater resources. The integrated aqua vegeculture system (iAVs) shows promise for water conservation and environmental resilience. Objective: To evaluate lettuce growth in iAVs with varying salt levels and investigate how saltwater impacts the biochemical properties and growth of both fish and lettuce. Methods: Over four months, iAVs were incorporated into an existing aquaponic system with lettuce (Lactuca sativa) and tilapia (Oreochromis niloticus). Four treatments were tested: freshwater (control-T1) and saltwater concentrations of 1 (T2—2.5%), 2 (T3—5%), and 3 (T4—7.5%). Results: Increased salinity did not affect the fish growth parameters, with a 90% survival rate across all groups. Higher salinity levels potentially improve fish farming efficiency. Lettuce growth was optimal in freshwater, with promising results at the T2 and T3 levels, but T4 had negative effects. Proximate composition analysis showed a decline in lettuce nutritional elements as the saltwater concentration increased. Conclusion: This approach could transform food production in coastal regions and arid nations, addressing food security and water scarcity issues while alleviating the pressure on freshwater sources. Full article

Clinostomum is a genus of parasitic trematodes found worldwide, infecting a wide range of hosts, including freshwater fishes, snails, birds and occasionally humans. In this study, clinostomid metacercariae were collected from Nile tilapia raised in fish farms in the Upper Tana River region, Kenya. The prevalence of infection was 17.2%, with metacercariae infecting the skin, gills and buccal cavity of the fish. Using light microscopy, scanning electron microscopy (SEM) and molecular methods targeting both nuclear ribosomal (ITS1, 5.8S, ITS2) and mitochondrial (COI) regions, the metacercariae were identified as C. cutaneum, C. phalacrocoracis, C. tilapiae and Euclinostomum heterostomum. The three species of Clinostomum have previously been reported to infect fish or piscivorous birds in Kenya, while this is the first report of E. heterostomum in this country. SEM analysis revealed new ultrastructural features of C. cutaneum, including an excretory pore surrounded by minute spiny papillae, an everted cirrus and dome-shaped papillae on the tegumental area around the genital pore. The cirrus lacked basal papillae, showing morphological variation between the adult and metacercarial stages. Our study, therefore, provides new insights into the phenotypic identification of flukes that may be pathogenic to fishes and humans and, therefore, of scientific and practical importance. Full article

This study evaluates the efficacy of a new florfenicol-based drug, both in vitro and in vivo, in Nile tilapia (Oreochromis niloticus) against pathogens commonly found in fish farming and its withdrawal period. The drug’s efficacy was tested using prophylactic, metaphylactic, and therapeutic approaches against Streptococcus agalactiae (serotypes Ib and III) and Francisella orientalis. The minimum inhibitory concentration of florfenicol was 4, 5, and 128 μg/mL for the different pathogens. Fish mortality was lower in the prophylactic treatment compared to the metaphylactic and therapeutic treatments for S. agalactiae. No difference in mortality was observed for F. orientalis across treatments. Mild to moderate lesions suggestive of intoxication were observed, mainly in the liver of fish treated with overdoses or exposed to low temperatures. Florfenicol reduced mortality rates, especially with early treatment (metaphylactic), in fish experimentally challenged with the pathogens. Moreover, prophylactic antimicrobial use is not recommended, as it promotes the selection of multidrug-resistant bacterial strains. Additionally, the residual concentration of the drug in muscle tissue lasted for a shorter period than that recommended by the manufacturer, and at lower concentrations than required by national and international legislation. Full article

Despite the importance of Nile tilapia as a main aquaculture species in Uganda, limited research has been conducted concerning its genetic diversity, particularly in farmed populations. This gap has hindered the development of a systematic breeding program for this species. Successful aquaculture development, especially for genetic improvement, relies on the diversity and purity of wild and farmed populations as germplasm sources for selective breeding. Using microsatellite markers, the current study evaluated the genetic diversity of 480 samples collected from 20 populations of Nile tilapia (Oreochromis niloticus) in Uganda. All the populations exhibited a higher expected heterozygosity (0.50 ± 0.01) than observed heterozygosity (0.42 ± 0.01), although this was not significantly different. Populations from ponds showed lower FST values (<0.001), an indication of lower genetic differentiation. The populations formed four main clusters; the first comprising of mainly cages (Pal and Busana), the second with cages: Katosi and SON in addition to Rocks hatchery, the third comprised of Bawe cage fish farm and Tendo hatchery, and the fourth were populations from ponds and beaches on Lake Victoria. Given the higher genetic diversity and genetic differentiation of Tendo and Rocks populations, these farms would provide potential candidates for the development of local strains in Uganda. These results provide more insights into the management of local Nile tilapia strains towards reduction of inbreeding levels. Full article