The study involved feeding lemongrass essential oil (LEO) supplements to red tilapia (Oreochromis sp.) at concentrations including Control - 0 mg, T1 – 200 mg, T2 – 300 mg, and T3 – 400 mg per kg of feed. The research investigated changes in hematological (HCT, Hb, RBC, WBC & thrombocytes) and erythrocyte’s morphological (major/minor axis; perimeter, and area of erythrocyte) parameters before infection, 5- and 10-days post-infection (DPI). According to analytical findings, a diet containing LEO enhanced the synthesis of both erythrocytes and leukocytes in the peripheral blood of red tilapia after 20 days of being used. Therefore, the indicators of this group of fish showed better performance than those that did not use LEO supplement five days after bacterial infection. Fish fed 200 mg/kg of LEO after being challenged with S. agalactiae for ten days showed an improved effect on red blood cell production. White blood cells decreased at all concentrations because of citral’s immunomodulatory properties.

Snakehead (Channa lucius Cuvier, 1831) is a species of potential aquaculture interest in the Mekong Delta, Vietnam. However, their optimum environmental conditions have yet to be determined. This study aims to study the hatching success and larval and fry growth of C. lucius at six pH levels (5.5, 6.0, 6.5, 7.0, 7.5, and 8.0). Two consecutive experiments were conducted. Experiment 1 focused on incubating eggs and nursing the yolk sac larvae, and was carried out in aquariums. The monitoring included incubation time (IT), hatching rate (HR), and deformation rate of the newly hatched larvae (DR). Larvae were also collected daily during nursing for growth determination. In Experiment 2, four-day-old fry after hatching from experiment 1 were reared in plastic tanks with live feeds for 30 days. Growth was checked every ten days, while survival rate (SR) and coefficient of variation (CV) were determined at the end of the experiment. pH 5.5–8.0 was favorable for incubation, larvae, and fry, as assessed through good indicators of IT, HR, DR, and larval length and weight growths, as well as length and weight growths, SR, and CV of fry. Furthermore, the lowest DR (0.33%) was at pH 5.5, while except for pH 7.0, the shortest IT (41.1 h) significantly differed from that at higher pH levels (p < 0.05), and the highest larval growth parameters were at pH 5.5–6.0; meanwhile, pH 5.5–6.5 supported a better life for fry, as showed by the significantly higher growth parameters (p < 0.05) and SR and CV improvements in fry after 30 rearing days. Overall, pH 5.5–8.0 was suitable for the early stages of C. lucius, in which pH 5.5–6.0 was better for incubation and larval growth and pH 5.5–6.5 was better for fry development.

A 63-day completely random experiment with three replications was carried out to compare the effects of five different combination ratios of rice flour (R) and molasses (M) on the growth and survival rates of Pacific white shrimp ( Litopenaeus vannamei Boone, 1931) postlarvae applied biofloc technology. Five biofloc (BF) treatments, including R90-M10, R70-M30, R50-M50, R30-M70, and R10-M90, formed with the addition of different combination ratios of rice flour and molasses, i.e., 90% R+10% M, 70% R+30% M, 50% R+50% M, 30% R+70% M, and 10% R+90% M, respectively, with C/N ratios of 15:1, and a control (neither rice flour nor molasses applied) was randomly arranged into the 18 plastic tanks of 1.0 m3 volume (with 0.5 m3 of water) each tank and salinity of 15‰. The postlarvae (0.095 g) were stocked into the tanks at a 150 ind. m−3 density and fed pelleted feed (40% protein). There was an improvement in growth (FMW, WG, DWG, and SGR) for all treatments. Besides, treatments with more than or equal to 30% molasses have improved SR, FCR, and FB. Especially the highest SR (94.2%) was obtained at the R70-M30, which perhaps created the highest FB (1.435 kg m−3) in this treatment. The lowest FCR (1.28) was also observed in the R70-M30 and significantly differed from the control and other treatments. Besides, water quality parameters were within the ranges recommended for Pacific white shrimp health during the experimental period. Our findings indicated the benefits of shrimp culture using the BF system when different combined ratios of rice flour and molasses were applied, of which a ratio of 70% rice flour and 30% molasses was considered as the best.

The darkfin hind, Cephalopholis urodeta , is a commercially valuable reef fish species inhabiting the ecologically important Spratly Islands. Understanding this species’ genetic diversity and population structure is crucial for developing effective conservation strategies, particularly given the increasing pressures on coral reef ecosystems. This study investigated the genetic diversity and population structure of C. urodeta within the Spratly archipelago using mitochondrial COI and Cyt b gene markers. We analyzed 30 individuals for COI and Cyt b, revealing high levels of haplotype diversity (Hd=0.9563±0.0226 for COI; Hd=0.9402±0.0229 for Cyt b). However, despite this high overall diversity, our analyses also revealed significant genetic structuring within the archipelago, suggesting restricted gene flow among some populations. This structuring is likely influenced by the complex oceanographic currents in the region and the spatial distance between reefs, which can limit larval dispersal. These findings highlight the need for spatially explicit conservation and management strategies for C. urodeta in the Spratly Islands. Recognizing the genetic differentiation within the archipelago and implementing management measures tailored to specific zones will be crucial for preserving genetic diversity, maintaining connectivity, and ensuring the long-term sustainability of this important resource.

The rapid growth of global aquaculture has led to a rise in bacterial diseases, threatening food security and economies in developing countries. Vibriosis, caused by Vibrio bacteria, is the most common and devastating disease in shrimp farming, a crisis severely exacerbated by the emergence of multidrug-resistant pathogens. This study isolates and characterizes three novel bacteriophages (P18, P24, and P25) targeting an extensively drug-resistant (XDR) Vibrio alginolyticus strain (V79) isolated from diseased Litopenaeus vannamei in Vietnam. The host strain V79 was confirmed by PCR using species-specific collagenase and 16S rRNA genes. V79 showed high multidrug resistance, resistant to 9 of 10 antibiotics, with a MAR index of 0.9. Transmission electron microscopy (TEM) classified all three isolated phages displayed a sipho morphotype, characterized by icosahedral capsids and long, non-contractile tails. In environmental tolerance assays, all three phages were completely inactivated at pH 3.0 and showed a precipitous decline in titers at 56°C, but remained highly stable across pH 5.0–9.0 and temperatures of 4.0–40.0°C (>108 PFU/mL). Notably, at pH 12.0, all three isolates showed remarkable alkaline resilience; Phage P18 exhibited significantly greater stability (p1.5 log ₁₀ reduction in bacterial load and maintaining sustained population suppression, whereas P18 and P24 were limited by the emergence of resistant small colony variants (SCV). Our findings suggest that, while all three phages exhibit high environmental resilience, Phage P25 is the most promising candidate for further genomic safety validation, serving as a vital biological component in therapeutic phage cocktail formulations to manage XDR vibriosis in sustainable aquaculture.