The risk associated with the presence of bacterial and fungal pathogens in recirculating aquaculture systems (RASs) has resulted in an industry‐wide need for low‐cost, safe, and effective disinfectants. The toxicity of peracetic acid (PAA) to Atlantic salmon (Salmo salar) eggs, fry, and fingerlings (~16.3 g) in freshwater RAS water has been previously assessed; however, its toxicity to later juvenile life‐stages was yet to be investigated. The 24‐h LC50 value of PAA was determined for parr ( = 47 g), smolt ( = 66.5 g), and post‐smolt ( = 176.7 g) Atlantic salmon in RAS water static PAA treatments. The 24‐h LC50 values were calculated using the trimmed Spearman–Karber (TSK) method and toxicity relationship analysis program (TRAP). TRAP LC50 values for parr, smolt, and post‐smolt were 4.26, 4.27, and 4.78 mg/L PAA, respectively, while TSK LC50 values for parr, smolt, and post‐smolt were 4.27, 3.94, and 4.65 mg/L PAA, respectively. These 24‐h LC50 values provide novel guidance for developing safe PAA treatment protocols for Atlantic salmon parr, smolt, and post‐smolt in freshwater RAS, although the influence of varying water quality scenarios needs to be considered.

Accurate modelling of gastric evacuation (GE) is a prerequisite for optimising feeding strategies in aquaculture and improving predator–prey interaction models in ecological studies. However, GE analysis is challenging because of the interdependencies of the variables influencing the evacuation process. To overcome this, a general power function was developed in 1992 and refined in 1998 using non‐linear regression techniques. The proposed method is robust for identifying the best‐fit evacuation function while simultaneously assessing the effects of potential predictor variables. This study demonstrated the application of R statistical software for parameter estimation of the general power function to characterise the influence of fish size, meal size and temperature on GE rate (GER) in brown trout (Salmo trutta Linnaeus, 1758) and rainbow trout (Oncorhynchus mykiss Walbaum, 1792). The statistical methods presented are remarkably adaptable and applicable to a wide range of GE datasets. Furthermore, they can be extended to incorporate additional variables influencing GE, making them integral tools for advancing research in fisheries management, ecological modelling and aquaculture.

This study explores the effects of synbiotics on growth, intestinal health, and immunity in the Asian fossil catfish (Heteropneustes fossilis), a crucial species in Southeast Asian aquaculture. With the rising use of antibiotics in aquaculture, which poses risks to both the environment and consumer health, there is an urgent need for sustainable alternatives. This study investigates how synbiotics—combinations of probiotics and prebiotics—can enhance fish health and performance. Four dietary treatments with varying synbiotic concentrations (0%, 4%, 6%, and 8%) were tested over 45 days. Results indicated that synbiotic supplementation significantly improved growth metrics, including final weight and specific growth rate (SGR), with the highest benefits observed at 8% inclusion. Additionally, dietary synbiotics enhanced intestinal health by increasing villi height and width and crypt depth and positively affected hematological parameters, notably elevating hemoglobin (Hb) levels. Histological analysis revealed improved liver tissue organization and hepatocyte morphology with higher synbiotic concentrations. These findings suggest that synbiotics offer substantial benefits for fish growth, health, and immunity, positioning them as a viable, ecofriendly alternative to antibiotics in aquaculture. Further research should aim to refine synbiotic formulations and investigate their underlying mechanisms to optimize their application in sustainable aquaculture practices.

Vitellogenesis‐inhibiting hormone (VIH) is known to suppress vitellogenin gene expression and consequently inhibit ovarian development in many decapod species. However, the broader effects of VIH on other ovarian genes, which are crucial for understanding the molecular mechanisms by which VIH regulates vitellogenesis, have not been investigated. In this study, we comprehensively examined the influence of VIH on ovarian gene expression in the kuruma prawn Marsupenaeus japonicus. Transcriptome analysis was conducted on ovarian fragments incubated with and without VIH, leading to the identification of differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of these DEGs revealed that VIH affects genes involved in the PI3K‐Akt, MAPK, Rap1, and insulin resistance pathways. Comparative expression analysis of selected DEGs and non‐DEGs in the ovaries of wild‐caught immature and mature individuals further indicated that ubiquitin‐40S ribosomal protein S27a, thrombospondin, thymosin β‐like, and insulin‐like growth factor 1 receptor are likely involved in vitellogenesis under the regulatory influence of VIH, and that insulin‐like receptor and GTP‐binding protein alpha subunit Gi may also contribute to this process. These findings provide novel insights into the gene networks and signaling pathways underlying VIH‐mediated regulation of vitellogenesis and provide a basis for future studies to clarify their specific roles in reproductive biology of decapod crustaceans.

The influence of dietary arachidonic acid (ARA) on the reproductive performance of broodstock fish is a critical area of aquaculture research. This study investigates the impact of ARA levels in broodstock diets on broodstock hormone, fecundity, egg quality, and larval survival of largemouth bass (Micropterus nigricans). Experimental diets containing 0.9%, 2.0%, and 3.6% ARA as a percentage of total fatty acids (TFAs) were formulated and administered to broodstock over 84 days. Results indicated that a dietary ARA level of 3.6% significantly increased vitellogenin content in broodstock serum while reducing serum estradiol levels. Despite this hormonal shift, reproductive performance metrics, including fecundity, egg hatch rates, and the number of viable eggs until mouth opening, were not significantly affected by the ARA content in the broodstock diet. However, the 3.6% ARA group showed notable improvements in egg size and higher concentrations of ARA and docosahexaenoic acid in the eggs. Based on these results, 0.9% ARA in TFA content in broodstock diet could be sufficient for the reproduction of largemouth bass. A level of 3.6% ARA of TFAs can be added to the diet of largemouth bass broodstock to enhance offspring potential growth performance and healthy status.

Oxygen consumption rate (OCR), which reflects the metabolism requirement of fish, is regulated by body weight and temperature. However, the priority of body weight and temperature in determining the OCR of fish is not clear. The optimal temperature and feeding time for the commercially important silver pomfret (Pampus argenteus) in China were evaluated using two sizes of fish (15.8 ± 2.7 g, S; 35.3 ± 6.1 g, L) at four different water temperatures (21, 24, 27, 30°C) and four time periods (5:00–6:00, 11:00–12:00, 17:00–18:00, 23:00–24:00) in static respirometers. The results showed that the OCR of fish was significantly higher at 21 and 24°C than that at 27 and 30°C (p < 0.05). The Q10 increased from range of 21 and 24°C to range of 24–27°C but decreased from range of 24–27°C to range of 27–30°C. The body weight and water temperature significantly affected the OCR of fish (p < 0.05). The OCR of S was significantly higher than that of L (p < 0.05), while the OCR of fish increased linearly with increasing temperature. The OCR decreased with increasing fish body weight, and the coefficient (a – 1) in the linear regression equation of the logarithmic plot ranged from −0.568 to −0.191 (11.2–47.4 g, 21–30°C), with the mean value was −0.346. Overall, a two‐factor regression equation for OCR of silver pomfret was established as OCR = 0.0558 × W –0.0081 × T + 0.0341 (N = 120, R2 = 0.5626, p < 0.05). The OCR was relatively higher at 5:00–6:00 compared to other time periods of the day. These results suggested that body weight exerted a more significant influence on the metabolic rate of silver pomfret compared to temperature. The optimal temperature for this fish species was between 27 and 30°C based on Q10, and the recommended feeding time was at 5:00–6:00 for maximizing growth for silver pomfret.

An experiment using a 4 × 3 factorial design was conducted to evaluate the impact of three commercial probiotics and a control (no probiotic treatment) on the growth, digestive, and immune enzymatic indices of prawns (Macrobrachium rosenbergii) at three stocking densities (2, 4, and 6 m−2). The experiment took place in rectangular earthen ponds with a surface area of 120 m2 and a water depth of 1.5–2.0 m. The prawns in the treatment groups were fed commercial pelleted feed supplemented with probiotics. The results indicated a significant interaction effect on weight gain (WG), daily weight gain (DWG), daily growth rate (DGR), relative growth rate (RGR), specific growth rate (SGR), and survival. Overall, prawns treated with probiotics showed better growth performance compared to nontreated groups. Prawn cultured with P1 at a stocking density of 4 m−2 had better nutritional value, including higher protein level. The activity of prophenoloxidase (proPO), superoxide dismutase (SOD), and lipase enzyme was higher in probiotic‐treated groups up to a stocking density of 6 m−2 compared to control groups (p < 0.001). Probiotic P1 at stocking densities of 2 and 6 m−2 showed a significant interaction effect on the protease activity, with other probiotics also enhancing protease activity compared to control. This study highlights that the growth performance, proximate composition, protease, and lipase activity, as well as proPO and SOD activity, of prawns can be improved through the application of probiotic P1. In conclusion, the study suggests that commercial probiotics enriched with bacterial compositions like P1 can be effectively used for culture intensification of prawns.

This study investigated the protective effects of Pandanus tectorius leaf extract (PLE) on the tolerance of the brine shrimp Artemia franciscana against the pathogen Vibrio campbellii. Axenic Artemia nauplii were hatched and exposed to PLE for 2 h, after which their resistance to V. campbellii was examined. Protective responses were evaluated by measuring nauplii survival and changes in the expression of key immune‐related genes, such as heat shock protein 70 (hsp70), hsp60, hsp90, high mobility group box 1 (hmgb1), prophenoloxidase (proPO), and transglutaminase (tgase) upon V. campbellii challenge. Additionally, a Vibrio colonization assay was conducted to assess PLE’s antimicrobial potential. The results revealed that 2 h pretreatment with PLE at a concentration of 1 g/L significantly improved survival against V. campbellii. Immune‐related gene expression was induced at different time points (e.g., 12–24 h) during the Vibrio challenge and the colonization assay confirmed PLE’s antimicrobial properties. The observed protection could likely be due to a combination of immune gene activation, antioxidant activity, and the antimicrobial effect of the extract. This study highlights the significance of PLE by indicating its potential to serve as a protective agent in aquaculture, enhancing the resilience of aquatic organisms against biotic stressors like vibrios.

Microplastics (MPs) are prevalent in aquatic ecosystems; however, inland water bodies have received relatively little attention. These ecosystems provide essential habitat for various fish species, which contribute to ecological equilibrium and support the livelihoods and food security of millions. Fish demonstrate increased vulnerability to microplastic ingestion, making them essential bioindicators of ecosystem health and contamination levels. This study evaluates the presence of MPs in the intestine, gills, and muscle tissue of 30 individuals belonging to five commonly found fish species (Rhinomugil corsula, Mystus tengara, Ompok pabda, Labeo bata, and Cirrhinus mrigala) in the Padma River. A total of 252 MP items of different shapes were recorded in 100% of individuals investigated, exhibiting an average frequency of 8.27 ± 2.16 items per individual. Among the fish species, Ompok pabda exhibited the highest ingestion of MPs, with an average of 11.5 ± 1.87 items per individual, followed by other species. Organ‐wise analysis of MPs trend was found to be: intestine > gill > muscle. Fiber was recognized as the most commonly consumed MP type (72%), followed by fragment (22%), pellet (4%), and foam (2%). The white‐color MP (24%) was predominant, followed by other colored MPs. The majority of MP particles were found in the size class 1–5 mm (41.10% ± 12.34%), followed by <500 μm (34.18% ± 16.34%) and 500 μm–1 mm (24.72% ± 11.51%). Fourier transform infrared (FT‐IR) spectroscopy investigation confirms both high‐ and low‐density polyethylene polymeric compositions of MPs. The study assesses the prevalence of microplastics in Padma River fish, highlighting the immediate necessity for focused conservation initiatives, ongoing monitoring, and evaluation of microplastic pollution to protect aquatic ecosystems and human health.

The medicinal herb Euphorbia hirta is abundantly available and exhibits impressive biological properties. This study looked at how dietary E. hirta extract (EHE) affected Clarias gariepinus growth, biochemistry, antioxidant status, immunological response, and resistance to Aeromonas hydrophila (AE) infection. Five isonitrogenous diets of 40% crude protein were prepared to contain 0.0, 0.5, 1.0, 1.5, or 2.0 g EHE/kg feed. Fish (n = 450; mean = 6.60 g) were randomly distributed to 15 500‐L aquaria (30 fish/aquarium; 100 cm × 100 cm × 60 cm, length × width × height) and fed thrice (07:00, 12:00, and 17:00 h) daily with experimental diets for 12 weeks until apparent satiation. Fish guts and blood samples were taken from the fish to measure antioxidant parameters, serum biochemical parameters, and intestinal morphometry. After the feeding trial, the fish received an intraperitoneal injection of pathogenic AE and were monitored for 14 days. Blood samples were taken for the immune response testing following the 14‐day challenge test. With a 0.5 g/kg diet, dietary EHE improved weight gain (WG), specific growth rate (SGR), villi height, and FCR. Blood proteins, urea nitrogen, and creatinine were unaffected, although alkaline phosphatase (ALP) concentrations appeared to decrease as the EHE inclusion levels increased. Fish‐fed EHE‐based diets showed increased activity of the serum antioxidant enzymes glutathione (GSH)‐s‐transferase (GST),GSH peroxidase (GPx), and superoxide dismutase (SOD). In the challenged fish‐fed EHE‐supplemented diets, respiratory burst, and lysozyme activity were increased, with the highest relative survival (RS) occurring at 0.5 g EHE/kg diet. In conclusion, this study found that 0.5 g EHE has growth‐promoting, antioxidant, and immune‐stimulating effects in C. gariepinus against AE infection, hence its inclusion at this level is advised.