Aquaculture Research最新文献

Brewery byproducts such as brewer’s spent yeast (BSY, Saccharomyces cerevisiae) have little-to-no commercial value; however, BSY contains nutritional properties with the potential to be utilized as a beneficial feed additive by the aquaculture industry. It was hypothesized that BSY could be used as a supplement in farmed rainbow trout (Oncorhynchus mykiss) diets to improve production and health in relation to the gastrointestinal (GI) bacterial community. Fourteen juvenile rainbow trout (28.6 ± 0.4 g, mean ± standard error [SEM]) were stocked per 12 polyethylene tanks (170 L each) in a single recirculating aquaculture system (RAS). Three treatment groups, performed in quadruplicate at the tank level, included a control (commercial feed), low yeast (LY, commercial feed coated with 2% BSY), and high yeast (HY, commercial feed coated with 5% BSY). Over the 8-week trial, compared to the control, the LY and HY fed fish grew significantly (p  < 0.01) faster, with a 20.8% and 35.4% increase in weight gain, respectively. No differences were observed for fish biometrics or bacterial communities between treatment groups. However, between tissue types significant differences (p  < 0.05) in the bacterial communities were observed for alpha diversity. Overall, supplemented BSY served as an effective growth additive for rainbow trout without negatively impacting animal health.

Ecytonucleospora hepatopenaei (EHP) is an obligate intracellular microsporidian that primarily infects the epithelial cells of the shrimp digestive systems and is a major pathogen plaguing the shrimp industry. The development of a robust detection system is crucial for facilitating point-of-care, affordable, and equipment-free identification of this pathogen, especially in field places. This present study involved screening aptamers for EHP spores through the whole-cell Systematic Evolution of Ligands by Exponential Enrichment (SELEX) technique, resulting in the identification of the most suitable aptamer (Apt-6) with a dissociation constant (K_d) of 8.28 nM. By utilizing this aptamer alongside the hybridization chain reaction (HCR), we have established a visual detection method for EHP, employing lateral flow strips. This method exhibits high specificity, effectively differentiating EHP from similar microsporidian and common shrimp pathogens with a detection limit of EHP of 7.8 × 10² spores/mL. The method eliminates the need for genomic DNA extraction, which saves detection time and decreases the possibility of contamination. This is the inaugural screening of the aptamer against the EHP, and it is anticipated that the specific aptamer and the convenient assay will offer an additional option for EHP detection, particularly in field settings.

The introduction of invasive suckermouth catfish (SMC) Hypostomus plecostomus has greatly affected the freshwater ecosystems in Bangladesh, posing a significant threat to indigenous fish species. This species is not commonly harvested and consumed, sparking debate over whether to eradicate it from the natural waterbody or repurpose it beneficially. This study explored the feasibility of utilizing SMC as a partial or complete replacement of commercial fish meal (CFM) in the diets of climbing perch Anabas testudineus, assessing impacts on growth performance, whole-body composition, hematobiochemical parameters, intestinal and liver health, and economic viability. Five isoproteic (32% crude protein) and isocaloric (9% crude lipid) diets were formulated with varying SMC levels: (0% [D1, control], 25% [D2], 50% [D3], 75% [D4], and 100% [D5]) and fed to fish until satiety over 90 days. Diets D1–D3 significantly improved palatability, growth metrics (final weight, weight gain, and specific growth rate), and feed utilization (feed conversion ratio and protein efficiency; p < 0.05), compared to D4 and D5. Enhanced levels of white blood cells, lymphocytes, and platelets were also recorded in D1–D3 (p  < 0.05). Blood biochemical parameters varied significantly across treatments (p  < 0.05), but no specific trend was observed. Superior intestinal integrity characterized by abundant goblet cells, intact stratum compactum, and well-developed villi was observed in D1–D3, along with improved liver morphology, particularly in D3. Economically, D1–D3 treatments yielded better outcomes, including higher production, reduced feed cost, increased revenue, gross margin, return on investment (ROI), and profit index (PI). Overall, replacing CFM with SMC up to 50% proved effective, supporting optimal growth, health, and profitability in A. testudineus, while offering a sustainable strategy to mitigate the ecological impact of this invasive species.

Given the rising concerns about antibiotic resistance in aquaculture, the increasing need for sustainable, eco-friendly alternatives has been highlighted. In response, a 45-day feeding trial was conducted to evaluate the efficacy of dietary onion powder and probiotics as natural growth promoters and immune enhancers in stinging catfish (Heteropneustes fossilis). The study tested six dietary treatments: a basal diet (without prebiotics and probiotics, control), O (2% onion powder + basal diet), P (4% probiotics + basal diet), and three combined treatments—OP3% (1% onion powder + 2% probiotics + basal diet), OP6% (2% onion powder + 4% probiotics + basal diet), and OP12% (4% onion powder + 8% probiotics + basal diet). The trial aimed to assess their effects on growth performance, feed utilization, intestinal morphology, liver health, and immune response. Among the treatments, the OP6% diet demonstrated the most significant improvements. Fish in this group showed marked increases in weight gain (WG), percentage WG, daily WG, specific growth rate (SGR), hepatosomatic index (HSI%), and viscerosomatic index (VSI%). Feed efficiency also improved, as evidenced by a lower feed conversion ratio (FCR) and higher protein efficiency ratio (PER). Survival rates, however, remained consistent across all groups. Gut health was notably enhanced in the OP6% group, with significant improvements in villi length and width, crypt depth, goblet cell numbers, and overall intestinal architecture. Liver histology also indicated healthier hepatocyte structures. Immunologically, the OP6% diet significantly elevated white blood cell (WBC) counts—including lymphocytes, neutrophils, monocytes, and eosinophils—while basophils remained unaffected. In conclusion, the combination of 2% onion powder and 4% probiotics (OP6%) presents a promising natural alternative to antibiotics, promoting better growth, nutrient utilization, gut health, and immune function in stinging catfish.

Two additives, rosemary oil and a commercial herbal product (HP; AROTEC-G) containing garlic essential oil, carvacrol and thymol were investigated for their potential to reduce the parasitic burden in yellowtail kingfish (YTK; Seriola lalandi) infected with Zeuxapta seriolae. Naturally infected fish were fed diets supplemented with either 2.5 mL.kg⁻¹ rosemary oil or two concentrations of HP (5 and 10 g.kg⁻¹) for 20 days. At 10 and 20 days, the effect of the diets on parasite abundance was evaluated. Feed intake and growth were similar across treatments (p > 0.05). By day 10, both rosemary oil and HP significantly reduced parasite burden compared to the control (p = 0.03). Praziquantel (PZQ) baths on days 10 and 20 found that the supplements were more effective in reducing new parasite recruitment rather than eliminating adult parasites. The HP product, at both doses, significantly reduced reinfection by day 20. Rosemary oil reduced parasite load by 43% compared to the control by day 20. Liver and kidney function remained unaffected. This study concluded that rosemary oil and blended essential oils can assist in the management of Z. seriolae infection in YTK culture.

Nile tilapia (Oreochromis niloticus) supports both capture and aquaculture fisheries in Kenya, contributing 80% of the total annual aquaculture production. Poor management practices in fish hatcheries, resulting in inbreeding and a lack of genetic improvement and breeding strategies, have hampered the sustainable growth of farmed O. niloticus in Kenya. The native populations of O. niloticus suitable for use as the foundation stock for selective breeding are often threatened by hybridization and introgression, through uncontrolled transfer of genetic material across basins, especially with the introduction of cage aquaculture of O. niloticus in Lake Victoria. A study was initiated to assess the genetic diversity and population structure of O. niloticus from major hatcheries and natural stock from Lakes Victoria and Turkana. Eight microsatellite DNA markers designed for O. niloticus were used to genotype 89 natural and cultured individuals from 11 different sites in Kenya. Genetic diversity was moderate, with an overall mean of 5.46 alleles and 3.88 effective alleles per locus. Kamuthanga farm showed the highest allelic richness (7.63), followed by Turkana natural (6.75), while both Busia caged and Busia natural populations had the lowest (4.00). Analysis of molecular variance (AMOVA) results indicated that 95% of genetic variation occurs within the population, while only 2% is attributed to differentiation among populations, indicating strong within-population structuring. STRUCTURE outputs were summarized using STRUCTURE HARVESTER, which identified K = 3 as the optimal number of genetic clusters, indicating the presence of three genetically distinct subpopulations among the sampled tilapia. Usenge caged and Turkana formed Cluster 1, Victory, and Kenya Marine and Fisheries Research Institute (KMFRI) farmed populations formed Cluster 2, while Homa Bay and Dunga natural populations comprised Cluster 3, showing close genetic similarity. These results indicate a well-defined hierarchical structure at K = 3, representing the best fit for the dataset across all populations. High genetic diversity observed in farmed populations with a history of selective breeding, like KMFRI, demonstrates the need to operationalize such programs within the policy framework. The within-population variability demonstrated in this study could be leveraged to design breeding programs based on marker-assisted selection framework for increased aquaculture productivity.

This study investigated the distribution of odorant compounds in water collected from the tank, drum filter, biological filter, and UV system outlets and the sludge inside the drum filter across two sturgeon RAS farms. A combinatory sensory-analytical approach was applied to assess the aroma profiles via descriptive sensory analysis and the odorant composition by gas chromatography–olfactometry and gas chromatography–mass spectrometry. All water samples were described as fishy, moldy, earthy, algae-like, and sea-water-like notes. Eighty-six odorants were detected olfactorily, of which 44 were identified. Notably, several compounds are reported here for the first time in RAS water, including 1-butanol, myrcene, 1-tetradecene, γ-crotonolactone, 2,6-di-tert-butyl-4-methylphenol, 2-phenoxyethanol, ethyl palmitate, methyl stearate, and methyl dihydrojasmonate. Geosmin and 2-MIB were quantified in all samples. Their concentrations varied from 85 to 432 and from 40 to 43 ng/L for RAS 1 and from 70 to 178 and from 60 to 82 ng/L for RAS 2, respectively. The concentration of both compounds did not vary through the compartments due to water recirculation, and a high concentration was only detected in water from the sludge.

Rainbow trout farming in Kenya remains an underdeveloped yet high-potential sector within the country’s aquaculture industry, despite the availability of suitable ecological conditions in high-altitude regions. This review critically examines the historical evolution, current status, challenges, and future prospects of rainbow trout farming in Kenya, drawing on comparative insights from leading rainbow trout-producing nations. Introduced during the early 20^th century for sport fishing, rainbow trout aquaculture has gradually transitioned into a commercial enterprise, albeit at a limited scale. Despite increasing consumer demand and premium market value, the industry faces significant constraints, including inadequate seed supply, high feed costs, climate variability, weak market infrastructure, regulatory inefficiencies, and limited research and extension support. The reliance on imported fingerlings and feeds exacerbates production costs, making the sector less competitive. Furthermore, climate change-induced water scarcity and rising water temperatures threaten cold-water aquaculture, necessitating urgent adaptation strategies. Drawing lessons from global industry leaders, such as Norway, Chile, and India, this review highlights strategic interventions for optimizing Kenya’s rainbow trout farming industry, including strengthening hatchery systems, developing cost-effective local feed, enhancing climate-smart farming technologies, and establishing structured market linkages. Policy reforms and increased investment in research, extension services, and environmental conservation are crucial for unlocking the untapped potential of rainbow trout aquaculture. If effectively harnessed, rainbow trout farming could contribute significantly to national fish production, rural livelihoods, and economic growth while promoting environmental sustainability.

A nanocomposite of Ag/WO₃ was synthesized through a two-step process: first, the hydrothermal synthesis of WO₃ using Na₂WO₄, followed by gamma irradiation to dope the material with silver nanoparticles (Ag). To study the effect of silver doping, three different Ag⁺ concentrations −1, 2, and 3 mmol were introduced to a fixed 20 mmol concentration of WO₃. The resulting nanocomposites were designated as AgW1, AgW2, and AgW3, respectively. The presence of Ag was confirmed using elemental mapping, Energy Dispersive Spectroscopy (EDS), and X-ray diffraction (XRD). Dynamic Light Scattering (DLS) measurements revealed particle sizes of 6.879, 7.010, 7.093, and 7.101 μm for WO₃, AgW1, AgW2, and AgW3, respectively. The crystallite sizes of the Ag nanoparticles in the Ag/WO₃ composites, as determined from the XRD patterns, were found to increase with Ag content, measuring 42.5 nm, 53.2 nm, and 56.8 nm for AgW1, AgW2, and AgW3. The band gap energies, determined by UV-Vis Diffuse Reflectance Spectroscopy (DRS), decreased from 2.4 eV for WO₃ to 2.35, 2.30, and 2.25 eV for AgW1, AgW2, and AgW3, respectively. The photocatalytic activity was assessed through chloramphenicol degradation and antibacterial tests against E. ictaluri pathogens in catfish, using the Minimal Inhibitory Concentration (MIC).

Aquaculture production supports the United Nations Sustainable Development Goals (SDGs), especially SDG 2 (Zero Hunger), by enhancing food security and sustainable practices. This study investigated the seasonal dynamics of cyanobacterial (CB) blooms in aquaculture fishponds in South Africa (SA) and Nigeria (NGA). Water samples were collected twice per season for 1 year and analyzed for physicochemical (temperature, pH, and nutrients), biological (chlorophyl-a and cyanobacteria biomass), and meteorological parameters. FlowCAM analysis revealed Microcystis sp. as the dominant cyanobacterium across all seasons and locations. Cyanobacteria biomass peaked during dry and wet seasons in NGA, with strong positive correlations with nitrate (r = 0.87) and phosphate (r = 0.82). In contrast, SA fishponds showed lower cyanobacteria biomass, which was not significantly correlated with temperature or rainfall. Principal component analysis (PCA) revealed that chlorophyl-a and temperature were key drivers in SA, while nutrients were more influential in NGA. The study concludes that nutrient dynamics and aquaculture management practices, rather than seasonal temperature or precipitation, are the primary factors driving CB blooms in tropical fishponds. NGA fishponds experienced sustained dominance of Microcystis blooms, driven by elevated nutrient inputs from intensive fertilization and high stocking densities. Hydrological flushing and rainfall-induced dilution offer potential for CB bloom control, though their effectiveness is influenced by local management practices.