Vietnam Journal of Agricultural Sciences

Artemia parthenogenetica is an emerging species used in marine hatcheries in Vietnam. Disinfection during their cyst incubation is important, however, disinfectants might have side-effects. This study examined the effects of polyvinylpyrrolidone-coated nanosilver particles (AgNPs) on A. parthenogenetica cyst hatching and nauplii development. Cysts were exposed to low (0.1, 0.4, and 0.7 mg L-1) and high (1, 4, and 7 mg L-1) levels of AgNPs for 48h. The total Vibrio in the incubated water and nauplii significantly decreased when AgNPs were applied, however, the hatching success significantly reduced when the AgNPs level exceeded 1 mg L-1. Nauplii Instar I and Instar II were exposed to 10, 50, 100, 200, 500, 600, 700, 750, 800, 900, and 1000 mg L-1 to determine their LD50. The LD50-36h and LD50-48h of AgNPs on Instar I were 136.5 and 53.21 mg L-1, respectively, while those on Instar II were 22.15 and 12.1 mg L-1, respectively. Thus, the safe level of AgNPs, which could be used to control Vibrio during Artemia cyst incubation in fish/shrimp hatcheries, is 0.7-1 mg L-1.

Coastal aquaculture zones, including areas for shrimp and mollusk farming, are subject to multiple stressors, such as internal farming activities, inland runoff, and extreme weather events. These factors contribute to spatiotemporal fluctuations in water quality, directly affecting aquaculture productivity and sustainability. This study aimed to assess the current status of the water quality in the shrimp and clam farming areas across the Nam Dinh coastal districts identify the spatial and temporal variation trends, and propose appropriate management measures. Environmental parameters, including pH, dissolved oxygen (DO), salinity, alkalinity, COD, ammonium (N-NH₄⁺), nitrite (N-NO₂⁻), hydrogen sulfide (H₂S), total suspended solids (TSS), and total Vibrio count, were monitored biweekly. The samples were collected on the same day between 5:00 and 7:30 a.m. The results indicated significant temporal fluctuations in water quality, with a clear deterioration trend during the rainy season and in storm-affected months, particularly in September, during the passage of Typhoon Yagi. In the shrimp farming areas, the water source quality tended to decline during June-August. Localized differences were also observed: Nghia Hung was characterized by low DO levels, while Hai Hau experienced large salinity fluctuations. In the clam farming zones, water quality was lowest in June and July. Giao Thuy exhibited a higher frequency of salinity values falling below acceptable thresholds compared to Nghia Hung, suggesting greater variability in salinity levels. These findings provide a scientific basis for local authorities and farmers to plan adaptive water management strategies, such as storing high-quality water for use during periods of environmental stress.

Flavobacterium oreochromis is a major bacterial pathogen that causes columnaris disease in tilapia (Oreochromis spp.) and other freshwater fish species. This study assessed the antibiotic resistance profiles and minimum inhibitory concentrations (MICs) of F. oreochromis isolates obtained from infected tilapia cultured in Northern Vietnam. A total of 51 isolates retrieved from diseased fish collected in Hai Duong (n = 23), Bac Ninh (n = 16), and Hoa Binh (12 isolates) were used in the study. The bacteria were cultured on TYES agar, identified through morphological and biochemical analyses, and confirmed by PCR. Antimicrobial susceptibility testing employed the disk diffusion method against 15 antibiotics, while the MICs of six frequently used antibiotics were determined via the broth microdilution method. The antimicrobial susceptibility test revealed that the isolates exhibited high resistance to oxacillin (100%) and neomycin (76.5%), and moderate resistance to sulfamethoxazole-trimethoprim (37.3%), doxycycline (35.3%), and oxytetracycline (41.2%). Resistance values to the remaining antibiotics were below 12%. Notably, all the isolates were multidrug-resistant (MDR), exhibiting resistance to 2-10 antibiotics, and 14 distinct resistance phenotypes were identified. The MIC values ranged from 0.063-1 µg mL-1 for amoxicillin, 0.125-8 µg mL-1 for erythromycin, and 0.25-8 µg mL-1 for florfenicol. For oxytetracycline, doxycycline, and sulfamethoxazole-trimethoprim, the MICs ranged from 0.016-1 µg mL-1, 0.125-2 µg mL-1, and 0.5-16 µg mL-1, respectively. These findings highlight a decline in the efficacy of commonly used antibiotics against F. oreochromis, underscoring the necessity for routine antimicrobial susceptibility testing to promote rational antibiotic use in aquaculture.

Cryptocaryon irritans is an ectoparasitic protozoan responsible for white spot disease, posing a significant threat to mariculture systems in Vietnam. This study aimed to isolate and propagate C. irritans, and to establish an experimental infection model in Trachinotus spp. (5-7cm in length) under laboratory conditions. Between February and June 2025, a total of 106 fish samples were sourced from aquaculture operations in Quang Ninh and Khanh Hoa, revealing an average C. irritans infection rate of 59.43%, with the highest prevalence observed during March and April. Infected fish exhibited clinical signs including skin darkening, mucus loss, white spots on the skin and gills, fin erosion, ulcerations, and tissue damage. The parasite was successfully cultured at the trophont stage and was propagated to the tomont and theront stages at 28-30°C, achieving a conversion efficiency of 61.7% after 48 hours and yielding an average of 150-300 theronts per tomont. These theronts were introduced to Trachinotus spp. at a density of 5,000 theronts per 250L tank (50 fish) at a temperature of 28°C. The infection progressed rapidly, with trophonts observed within 2-3 days and cumulative mortality reaching 100% by day seven. The established infection model offers a robust platform for further research in epidemiology, immunology, and therapeutic interventions against C. irritans.

Depuration is a widely used post-harvest technique to reduce contaminants in shellfish. However, its effects on the nutritional quality of blood cockles (Anadara granosa) in the removal of microplastics (MPs) are not well understood. This study aimed to assess the changes in the biochemical composition of cockle meat during a five-day MP depuration process. Cockles were subjected to a controlled depuration protocol, with samples collected at day zero, three, and five for analyses of MP abundance and biochemical composition. Standard methods were used to determine the MPs, proximate composition (including ash, proteins, lipids, and carbohydrates), and mineral content (Ca, Mg, P, and Fe). The results showed that the five-day depuration period effectively reduced the mean MP load by 71.6%. The process removed larger MPs and films, resulting in a higher relative abundance of smaller MPs (<500µm) and fibers. However, this process resulted in a statistically significant decrease in the biochemical composition of the cockles. By day five, the contents of biochemical composition had declined significantly. These findings demonstrate that while depuration is an effective process for reducing MP contamination in A. granosa, it decreases the nutritional quality.

The present study aimed to investigate the effects of dietary supplementation of peptidoglycan, Lactobacillus plantarum, or their combination on the growth performance, disease resistance, and immune status of juvenile striped catfish. Fish were fed on a commercial feed supplemented with various concentrations of peptidoglycan (PG5.0: 5.0g per kg of feed), Lactobacillus plantarum (PL5.0: 5.0g per kg of feed), or the combination of the two (PP0.0: 0.0g + 0.0g per kg of feed; PP2.5: 2.5g + 2.5g per kg of feed); PP5.0: 5.0g + 5.0g per kg of feed). Fish were then fed at a rate of 3% of their body weight for six weeks. After the feeding trial, fish were infected with Aeromonas veronii at 50% the lethal dose (LD50, 107 CFU/mL). Blood samples were collected after two, four, and six weeks of the experiment and on the second day after bacterial infection for hematological parameters and immune assays. The results demonstrated that supplementation with PP2.5 significantly improved the growth performance and feed utilization in fish, while the LP5.0-based diet reduced mortality in A. veronii-challenged fish, indicating enhanced disease resistance. The modifications in hematology and immune status were affected by the pro-, pre-, and synbiotics tested in this study. In conclusion, dietary supplementation with peptidoglycan and L. plantarum enhances growth, immunity, and disease resistance in striped catfish, supporting sustainable aquaculture practices for improved fish health and production efficiency, with the optimal ratio being 2.5g peptidoglycan + 2.5g L. plantarum or 5g L. plantarum per kg of diet in striped catfish.

The present study investigated the effects of dietary supplementation with Gamnui (Gnetum montanum) extract on growth performance, immune response, and disease resistance in striped catfish (Pangasianodon hypophthalmus). Four experimental diets were formulated by adding Gamnui extract at 0 (G0), 2 (G2), 5 (G5), and 10 g kg-1 feed (G10), and administered to juvenile fish for six weeks. Growth parameters including final weight, weight gain, daily weight gain (DWG), specific growth rate (SGR), and feed conversion ratio (FCR) were recorded, along with relative internal organ indices. Post-feeding, fish were challenged with Aeromonas veronii to assess cumulative mortality and immune-related parameters. The results indicated no significant differences among dietary treatments in terms of final weight, weight gain, specific growth rate, or feed conversion ratio. Similarly, hepatosomatic (HSI), viscerosomatic (VSI), and gut indices (GSI) were unaffected. After bacterial challenge, the G10 group exhibited the lowest cumulative mortality, compared to the control (G0). Dietary Gamnui extract modulated several immune-related indicators: myeloperoxidase (MPO) activity increased consistently in fish receiving 10 g kg-1, while glutathione (GSH) levels were elevated across all supplemented groups, indicating enhanced antioxidant capacity. Peroxidase activity exhibited a treatment-dependent response after infection, whereas lysozyme activity did not change.. In summary, dietary Gamnui extract did not influence fish growth performance but enhanced non-specific immune responses and disease resistance, particularly at 10 g kg-1. These findings highlight the potential of this medicinal plant extract as a sustainable immunostimulant in aquafeed for striped catfish.

Saccharomyces cerevisiae is considered to be an alternative to antibiotics in reducing the growth of pathogenic bacteria and enhancing the mucosal immune system. In countries with developed livestock industries, antibiotic resistance of Salmonella pullorum is still causing difficulties in controlling Pullorum disease. This study aimed to isolate and select S. cerevisiae strains with antagonistic activity against S. pullorum for potential application in probiotics production. A total of eight S. cerevisiae strains were isolated from 50 ripe mango samples. All the isolated strains exhibited inhibitory effects against S. pullorum. Among them, strains SC1, SC6, and SC8 showed strong antagonism, with inhibition zone diameters of 16 ± 0.87mm, 16 ± 0.50mm, and 17 ± 1.80mm, respectively. These isolates exhibited high stability under various conditions. These findings suggest that S. cerevisiae strains SC1, SC6, and SC8 are potential candidates for producing a probiotic to control poultry diseases.

This study analyzes the role of the Giao Hai fish market (Giao Thuy district, Nam Dinh province) in organizing and sustaining coastal community livelihoods. By integrating perspectives from small-scale fisheries, trader–fisher relations, gender analysis, and local ecological knowledge, the research is based on 27 in-depth interviews and participant observation conducted between March and June 2025. The findings reveal that the Giao Hai fish market functions as a strategic hub linking harvesting, trading, and processing, largely governed by informal institutions and community social capital. Relations between traders and fishers simultaneously provide essential financial and logistical resources but simultaneously create asymmetric dependencies. The gendered division of labor ensures the continuity of the supply chain but also reproduces inequalities in economic power. Current challenges include declining fishery resources, price volatility, competition from non-local traders, and limited cold storage infrastructure. The study recommends a combination of socio-economic measures and resource management strategies to secure sustainable livelihoods while protecting and restoring marine resources.  

Fish provide essential nutrients—high-quality proteins, omega-3 fatty acids, and vital vitamins—making them a key component of human nutrition. Previous studies have indicated that consumers prefer wild over cultured fish; however, whether real nutritional differences exist remains unclear. This paper reviews 41 studies on quality differences between wild and cultured fish across 27 species, examining proximate composition, minerals, fatty acids, amino acids, color, and texture. Cultured fish had a significantly lower moisture content but a higher lipid content, while the protein and ash contents showed no significant differences. Cultured fish sometimes exhibited lower polyunsaturated fatty acid percentages. Both groups were mineral-rich, though wild fish contained significantly higher toxic element levels. Color and texture differed substantially by origin. These results suggest both cultured and wild fish possess valuable quality attributes. Variations likely depend on sex, diet, region, season, farming mode, and environmental conditions. Although the core synthesis covers literature until November 2019, selected key studies from 2020-2024 were integrated to reflect recent developments, corroborating and refining the overall conclusions. This review offers insights for sustainable aquaculture quality development.