Minh Hoang Le

The growing demand for sustainable aquaculture requires improvements in shrimp production efficiency and health management. This study investigated the effects of dietary Bacillus subtilis and Lactobacillus acidophilus supplementation on the gut microbiota dynamics, growth performance, survival, and feed utilization of the Pacific white shrimp ( Litopenaeus vannamei ) post-larvae. Shrimp were reared over 84 days under four experimental groups: control (a probiotic-free diet), supplemented with 10⁷ CFU/g Lactobacillus (L), 10⁷ CFU/g Bacillus (B), and a mixed probiotic treatment (M) with 0.5x10⁷ CFU/g per each. Growth metrics, survival rate and, feed utilization were assessed, and entire intestinal samples were analyzed using high throughput DNA sequencing of V1-V9 of 16S rRNA hypervariable regions. Bacillus supplementation significantly improved final body weight and specific growth rate (SGR) compared to the other groups (p < 0.05), leading to notably higher biomass by Day 74. However, by the end of the 84-day experiment, these significant differences in body weight and length were no longer observed among the treatment groups (p > 0.05). The mixed probiotic group demonstrated significantly better FCR than the Bacillus group (p < 0.05), indicating improved feed efficiency. Gut microbiota analysis showed dominance of Pseudomonadota at the phylum level and Vibrio at the genus level (18.06%–48.28%). Neither alpha nor beta diversity was significantly affected by probiotic treatments (p > 0.05), though temporal and treatment-specific shifts in bacterial composition were detected. These results suggest that Bacillus and mixed probiotic supplementation may enhance shrimp growth and feed efficiency, supporting their potential application in sustainable shrimp farming.

Nghiên cứu này đánh giá ảnh hưởng của việc bổ sung vitamin C ở các mức khác nhau (150, 300, 600, 1.200, và 2.400 mg/kg thức ăn) lên thành phần sinh hóa cơ thể và hình thái xương của cá chim vây vàng (Trachinotus blochii) giai đoạn giống. Sau 10 tuần thí nghiệm, kết quả cho thấy việc bổ sung vitamin C không ảnh hưởng đến độ ẩm và hàm lượng tro, nhưng có tác động rõ rệt đến hàm lượng protein và lipid trong cơ thể cá. Hàm lượng protein và lipid cao nhất được ghi nhận ở mức bổ sung 300 mg/kg thức ăn. Ngoài ra, nghiên cứu không phát hiện dị hình xương ở cá, dù không bổ sung vitamin C, có thể do hàm lượng vitamin C sẵn có trong thức ăn nền đã đáp ứng đủ nhu cầu phát triển hệ xương của cá chim vây vàng giai đoạn giống. Kết quả này cung cấp cơ sở khoa học để tối ưu hóa dinh dưỡng trong nuôi cá chim vây vàng giai đoạn giống, đồng thời gợi ý cần nghiên cứu thêm về hàm lượng vitamin C tích lũy trong gan và cơ của cá. Từ khóa: Cá chim vây vàng, thành phần sinh hóa, hình thái xương, Trachinotus blochii, vitamin C. ABSTRACT This study assessed the effects of different dietary levels of vitamin C (150, 300, 600, 1,200, and 2,400 mg/kg feed) on the biochemical composition and skeletal morphology of juvenile snubnose pompano (Trachinotus blochii). After 10 weeks, results showed that vitamin C supplementation did not affect moisture or ash content but significantly influenced protein and lipid levels in the fish. The highest protein and lipid levels were observed at a supplementation level of 300 mg/kg feed. Furthermore, no skeletal deformities were detected, even in the absence of vitamin C supplementation, possibly because the vitamin C content in the basal diet was sufficient to meet the bone development requirements of juvenile snubnose pompano. These findings provide a scientific basis for optimizing the nutrition of snubnose pompano and suggest further research on vitamin C storage in the liver and muscle tissues of fish. Keywords: Snubnose pompano, biochemical composition, skeletal morphology, Trachinotus blochii, vitamin C.

This study evaluated the monthly variations in reproductive indices, egg quality, and larval survival of broodstock snubnose pompano ( Trachinotus blochii ) reared under captivity conditions from January to December. The parameters assessed included gonadal maturation rate, fecundity, egg diameter, egg buoyancy rate, fatty acid composition (SFA, MUFA, PUFA, and HUFA) in egg, fertilization rate, hatching rate, and 3-day larval survival rate. The results showed that May, July, November, and December were the most favorable periods regarding reproductive performance and egg quality, with maturation rates exceeding 70% and hatching rates surpassing 90%. Notably, July recorded the highest fecundity (107,454 eggs/kg female), and larval survival peaked at nearly 60% during this month. These findings highlight the significant influence of time and environmental factors on reproductive success and seed quality. Analyses revealed a strong relationship between egg quality and larval survival, with the nutrient content of eggs, particularly long-chain polyunsaturated fatty acids such as DHA and EPA. Therefore, the study recommends proactively developing seasonally aligned spawning schedules and providing targeted nutritional supplementation to broodstock during maturation to enhance sustainable seed production efficiency for this high-value marine species.

Nghiên cứu này được thực hiện nhằm đánh giá ảnh hưởng cộng gộp của hai yếu tố nhiệt độ và ammonia lên chất lượng ấu trùng cá hồng Mỹ (Sciaenops ocellatus) trong điều kiện biến đổi khí hậu, với nhiệt độ ngày càng gia tăng. Ấu trùng cá hồng Mỹ được nuôi thí nghiệm trong các điều kiện nhiệt độ khác nhau (27-28℃, 30℃, 32℃) và nồng độ ammonia từ 0, 0,02, 0,03, 0,19, 0,23 và 0,31 ppm. Kết quả cho thấy, nhiệt độ và ammonia có tác động tiêu cực đến tỷ lệ sống, sinh trưởng, khả năng bắt mồi, tần số hô hấp và lượng oxy tiêu thụ của ấu trùng. Tỷ lệ sống và khả năng bắt mồi giảm khi nhiệt độ và nồng độ ammonia tăng, trong khi tần số hô hấp và lượng tiêu hao oxy tăng theo. Quan trọng hơn là ấu trùng cá hồng Mỹ không có khả năng phục hồi sau khi tiếp xúc với nhiệt độ và ammonia ở mức cao. Kết quả này cung cấp cơ sở khoa học cho việc phát triển kỹ thuật sản xuất giống và nuôi cá biển trong điều kiện biến đổi khí hậu hiện nay. Từ khóa: Cá hồng Mỹ, Nhiệt độ, Ammonia, Ấu trùng cá, Biến đổi khí hậu This study aims to evaluate the combined effects of temperature and ammonia on the quality of Red Drum larvae (Sciaenops ocellatus) under climate change conditions, with rising temperatures. Red Drum larvae were cultured under different temperature conditions (27-28℃, 30℃, 32℃) and ammonia concentrations ranging between 0, 0.02, 0.03, 0.19, 0.23, and 0.31 ppm. The results showed that temperature and ammonia significantly affected survival rate, growth, feeding capacity, respiratory rate, and oxygen consumption of larvae. Survival rate and feeding capacity decreased as temperature and ammonia concentration increased, while respiratory rate and oxygen consumption increased. More importantly, Red drum larvae were unable to recover after being exposed to high levels of temperature and ammonia. These findings provide a scientific basis for improving seed production and marine fish farming techniques under current climate change conditions. Keywords: Red drum, Temperature, Ammonia, Fish larvae, Climate change

Fisheries and Aquatic Sciences

Fisheries and Aquatic Sciences

The application of fish protein hydrolysates (FPHs) in aquaculture has achieved encouraging outcomes due to its growth and health promoting properties. This trial was carried out to detemine the effects of various alcalase‐derived fish protein hydrolysate (FPH) supplementation on growth, feed utilization, proximate composition, liver and gut histology of juvenile giant trevally fed low fishmeal diets. Four tested diets (52% protein and 10% lipid) were produced, in which fishmeal and poultry meal (PM) were the main protein sources in the basal diet. 50 g/kg of each shrimp hydrolysate (SH), squid hydrolysate (SHH), and tuna hydrolysates (THs) were supplemented into the basal diet, namely SH, SHH, and TH, respectively. Fish were fed experimental diets in 56 days with four replicates per dietary group. The results reported that giant trevally fed SH, SHH and TH achieved higher growth than those fed the control. Feed intake (FI) didn’t alter, but lower feed conversion ratio (FCR) was seen in fish fed SH compared to the control, demonstrating that SH improved feed utilization. Protein and ash contents were increased in fish fed SH, SHH, and TH supplemented diets, whereas increased whole‐body lipid was obtained in those fed TH. Dietary SH, SHH, and TH supplementations contributed to higher whole‐body isoleucine, and higher lysine was seen in fish fed SH and TH. Total intestinal aerobic microbiota increased in fish fed SH, whereas Vibrio spp . density was relatively low among treatments. The goblet cells also increased in the intestine of the fish fed SH, indicating that SH could enhance intestinal health. The results indicated that all fish hydrolysates had beneficial effects of growth performance of juvenile giant trevally, in which SH showed more bioavailable than others, by improving feed efficiency and intestinal health.

This study investigates the combined effects of Vitamin E and temperature on the growth, biochemical composition, and immune responses of juvenile snubnose pompano ( Trachinotus blochii ). A 70-day experiment was conducted with six treatments combining two levels of dietary Vitamin E (0 and 400 mg/kg) and three temperature levels (28°C, 31°C, and 34°C). The results revealed that both temperature and Vitamin E significantly influenced growth performance, feed utilization efficiency, protein and lipid content, and certain immune parameters (P < 0.05). Fish reared at 34°C with 400 mg/kg vitamin E demonstrated the highest growth indicators (SGR _L , SGR _W ), protein efficiency, hepatosomatic index (HSI), and immune response, as indicated by elevated serum lysozyme levels, phagocytic activity, and white blood cells. Temperature notably affected lysozyme and respiratory burst activity, with values increasing at higher temperatures. Vitamin E supplementation improved these metrics regardless of temperature, increasing protein efficiency and reducing feed intake and feed conversion ratio (FCR). Moreover, Vitamin E enhanced immune responses, including increased white blood cell (WBC) counts and phagocytic activity. No interactive effects between Vitamin E and temperature were observed (P > 0.05). Overall, Vitamin E (400 mg/kg) positively influenced growth, biochemical composition, and immunity in snubnose pompano, particularly at elevated temperatures. The findings demonstrate that dietary vitamin E can enhance growth and immune performance, particularly under elevated temperatures, providing a basis for optimizing vitamin E use in snubnose pompano aquaculture.

Copepods are one of the most abundant invertebrate groups in the seas and oceans and are a significant food source for marine animals. Copepods are also particularly sensitive to elevated temperatures. However, it is relatively unknown how the internal microbiome influences copepod susceptibility to warming. We addressed this fundamental knowledge gap by assessing key life history traits (survival, development, and reproduction) and changes in the internal microbiome in the tropical calanoid copepod Acartia sp. in response to warming (26°C, 30°C, and 34°C). Copepod microbiomes were analyzed using high throughput DNA sequencing of V1–V9 of 16S rRNA hypervariable regions. Copepod performance was better at 30°C than at 26°C, as indicated by faster development, a higher growth rate, and fecundity. However, these parameters strongly decreased at 34°C. We recorded 1,262,987 amplicon sequence reads, corresponding to 392 total operational taxonomic units (OTUs) at 97% similarity. Warming did not affect OTU numbers and the biodiversity indices, but it substantially changed the relative abundance of three major phyla: Proteobacteria, Actinobacteria, and Bacteroidota. The thermophilic and opportunistic Proteobacteria and Bacteroidota increased under extreme temperatures (34°C) while Actinobacteria abundance was strongly reduced. Changes in the relative abundance of these bacteria might be related to reduced copepod growth, survival, and reproduction under extreme temperatures. Profiling the functional role of all internal bacterial groups in response to the temperature change will fundamentally advance our mechanistic understanding of the performance of tropical copepods and, more generally, marine invertebrates to a warming climate.