Limited information exists on the dietary requirements of the African bony‐tongue (Heterotis niloticus) fry as well as the suitable age to wean fry from live prey to formulated diets. These have been the major challenges to the commercial culture of the species. This study assessed the optimal weaning age of fry as well as the effect of varying phospholipid (PL) content and long chain polyunsaturated fatty acids (LC‐PUFAs) on survival, performance, and digestive enzyme activity of H. niloticus fry. The two weaning diets used were formulated to be isonitrogenous, isolipidic, and isoenergetic (49% CP, 20% CL, and 22.7 MJ/kg). The diets differed only in the content of PLs and LC‐PUFAs; eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Soy lecithin (PLs) and Algatrium DHA70 (a glyceride product high in DHA and EPA) were included at two levels. The diets were, respectively, labeled low phospholipid (LPP) (formulated to contain: 3.16% PLs, LC PUFAs: 0.66% DHA 0.10% EPA) and high phospholipid (HPP) (formulated to contain: 12.96% PLs, LC PUFAs: 3.04% DHA, 0.75% EPA). African bony‐tongue fry were fed Artemia nauplii until 15, 25, 35, 45, 65, or 85 days after hatching (DAH), respectively, then cofed with Artemia and one of the two weaning diets for an additional 7 days after which Artemia feeding was completely withdrawn. Hereafter, the fry were maintained solely on the experimental diets for 10 days. A control group was kept on Artemia nauplii throughout the experiment. The results showed that the survival rate of fish on the LPP and HPP diets increased significantly (p < 0.05) with weaning age; from 0% (LPP and HPP) for fry weaned at 15 DAH to a survival rate of 69.4% ± 3.9% (LPP) and 80.0% ± 9.4% (HPP) at 65 and 85 DAH, respectively. This was, however, lower than the survival rate obtained for the control (Artemia) which was 93.3% ± 3.33% at 85 DAH. The final mean weight, weight gain, and survival rate improved significantly (p < 0.05) for fry fed the HPP diet compared to the LPP diet. All digestive enzyme activity decreased significantly with increasing fish age (p > 0.05). Based on the results, it is recommended, that H. niloticus fry is maintained on live Artemia nauplii and provided with dry feeds high in LC‐PUFAs (33.98 mg g−1 diet) and PLs (12.96 mg g−1 diet) from <65 DAH to obtain higher survival rates.

Land‐based recirculating aquaculture systems (RASs) for smolt production are now widely used in the salmon industry, requiring sufficiently high stocking densities to be economically viable. However, elevated densities have often been associated with poor growth and reduced fish condition. Recently, Chinook salmon producers have begun to adopt similar practices, yet the impact of smoltification density on this species at commercially relevant levels remains unstudied. This research evaluated the effects of various smoltification densities (average densities of 20.9–68.5 kg/m 3 ) on growth and survival during smoltification and subsequent seawater transfer. Mortalities were low across all density groups, with the highest density group exhibiting the lowest mortality during the freshwater phase. While slight but significant growth reduction and fin damage were observed at the highest density during smoltification, these effects did not persist after seawater transfer to a lower density that simulated transfer to marine farms. Our findings indicate that Chinook salmon can be smolted at an average density of 55.1 kg/m 3 , with a maximum density of 80.4 kg/m 3 , without adverse effects on growth and with minimal density‐related injuries in freshwater and post‐transfer phases. In cases where freshwater or nursery space is constrained, smoltification at an average density of 68.5 kg/m 3 (up to a maximum density of 95.2 kg/m 3 ) may be feasible. These results provide a basis for optimising Chinook salmon RAS operations, balancing production efficiency with fish welfare.

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.

This study investigates the synergistic effects of swimming activity and dietary restriction on the metabolic and nutritional characteristics of muscle tissue in juvenile rainbow trout (Oncorhynchus mykiss, Walbaum, 1792). During a 6‐week study, four groups of juvenile rainbow trout, each starting with an average weight of 26.54 ± 0.36 g, were analyzed: the first group was allowed to feed freely in static water (SW group), the second experienced a dietary limitation (25% feed restriction) (LF group), the third was required to swim at a speed of one body length per second (SE group), and the fourth group faced a combination of dietary restriction (25% feed restriction) and enforced swimming activity (SELF group). Swimming activity was implemented using a water flow rate of one body length per second (1 BL s−1), ensuring a standardized exercise intensity. Comprehensive analysis revealed significant alterations in biochemical parameters, amino acid composition, and fatty acid profiles in rainbow trout muscle tissue. The results indicate a decrease in histidine levels (p < 0.05) with the combined effect of both swimming and feeding restrictions. Additionally, cysteine and semi‐essential amino acids (EAAs) showed a decrease (p < 0.05) solely due to the influence of swimming. As for fatty acid outcomes, linolenic acid exhibited a reduction with the combined impact of both swimming and feeding restrictions (p < 0.05), while margaric acid significantly decreased (p < 0.05) only with the influence of swimming. Crucial shifts in antioxidant defense mechanisms, including glutathione (GSH) and lipid peroxidation (LPO) levels, were identified, highlighting the roles of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) as biochemical parameters. Detailed examination further clarified modifications in glucose‐6‐phosphate dehydrogenase (G6PD) activities, reactive oxygen species (ROS) levels, and lactate dehydrogenase (LDH) activity, serving as pivotal indicators of oxidative stress and tissue damage. These findings contribute to a holistic understanding of nutritional dynamics within rainbow trout muscle tissue, offering insights crucial for optimizing fish health and productivity in aquaculture.

A feeding trial was conducted to assess the impact of a microalgal diet and a natural diet on the growth performance, water quality, nutrition, and survival of the edible oyster, Saccostrea cucullata. Four experimental diets, designated as “Chl” (100% Chlorella vulgaris), “Chaeto” (100% Chaetoceros gracilis), “Chl + Chaeto” (50% C. vulgaris + 50% C. gracilis), and “Outdoor” (natural diet), were used to develop the treatments. The growth performance and survival of oysters were evaluated by measuring initial and final weights and counts, alongside daily water quality monitoring, weekly chemical analysis, and nutritional composition analysis of muscle tissue at the end of the experiment. The treatments fed with microalgae showed significantly better growth performance, higher survival, and improved water quality parameters compared to the outdoor treatment (p < 0.05). Multivariate analysis revealed that salinity, total dissolved solid (TDS), conductivity, and dissolved oxygen (DO) positively influenced oyster growth, while temperature, ammonia, and soluble reactive phosphorous (SRP) showed negative associations. Additionally, protein content (29.1%–30.7%) showed no significant difference among treatments, while lipid (11.1%–18.2%) and carbohydrate (30.6%–36.2%) levels varied significantly (p < 0.05), with the highest values in the “Chl + Chaeto” treatment. Moreover, essential amino acids (EAAs) and non‐essential amino acids (NEAAs) varied significantly (p < 0.05), with EAAs higher in monoalgal (“Chl” and “Chaeto”) diet, and NEAAs higher in mixed and outdoor treatments. These findings highlight the potential of microalgal diets, particularly monoalgal formulations, in enhancing the nutritional quality and overall performance of cultured S. cucullata.

In August 2023, a severe skin ulcer outbreak occurred in net‐caged black rockfish (Sebastes schlegeli) of Nanhuangcheng Island, Bohai Sea. The causative bacterium, Vibrio harveyi, was identified through 16S rDNA and gyrB sequencing. Artificial infection experiments confirmed its high pathogenicity with a 7‐day LD50 of 5.41 × 106 CFU/mL. Histopathological analysis revealed hepatocyte vacuolization, erythrocyte aggregation in the spleen leading to splenic congestion and reducing the contrast between red and white pulp regions, glomerular atrophy, renal damage, intestinal epithelial necrosis, and muscle fiber disintegration. Immunoenzymatic assays showed elevated alkaline phosphatase (AKP), acid phosphatase (ACP), and lysozyme (LZM) activity. Additionally, qRT‐PCR analysis revealed downregulation of IL‐12B and upregulation of TNF‐α, CASP10, and RAFEA. Antibiotic susceptibility testing showed sensitivity to minocycline and doxycycline, but resistance to erythromycin and azithromycin. This study provides novel etiological and histopathological insights into V. harveyi infection in black rockfish, highlighting the bacterium’s impact on host tissues and immune response.

The rise of microplastics (MPs) as a significant environmental contaminant has raised concerns about their potential presence in aquatic ecosystems and food webs. The current study aimed to evaluate the properties and frequency of MPs in Bangladeshi commercial fish feed, a vital aquaculture sector component. Twenty‐one commercial fish feed samples representing three distinct grades (starter, nursery, and grower) and seven commercial formulations were tested. Standard digestion, density separation, and filtering techniques were used to extract MPs. The findings demonstrated that all the samples had extensive MPs contamination, with an average concentration of 9.23–14.27 MPs per gram of feed. Grower feeds have the lowest frequency of MPs, while starter feeds show highest MP abundance. The most abundant forms were fibers (45.44%), followed by fragments (36.30%) and microbeads (18.26%). The most frequently occurring colors were black (33.30%), transparent (27.37%), and blue (13.63%). The most dominant group of MPs was <300 µm (52.36%). Polystyrene (PS) and ethylene–vinyl acetate (EVA) were found to be the predominant polymers, making up 32.12% and 23.85% of the total MPs, respectively, based on Attenuated Total Reflection Fourier Transform Infrared Spectroscopy. Nitrile butadiene rubber (NBR) indicated low hazard, while low‐density polyethylene (LDPE) medium, polymethyl methacrylate (PMMA), polycarbonate (PC), and acrylonitrile butadiene styrene (ABS) indicated very high hazard. In addition, fish feed samples remained at low risk as specified by the Pollution Load Index (PLI). Given the possible dangers to fish health, human consumption, and environmental sustainability, this study emphasizes the urgent need for mitigation techniques to minimize MP contamination in aquafeeds.

The cocultivation of microalgae in aquaponic systems can improve nutrient removal and enhance water quality. Moreover, it can promote the biological and physicochemical balance in aquaponic ecosystems. However, the bacterial communities in aquaponic systems have not yet been comprehensively characterized and the effects of microalgae cocultivation remain unclear. Using 16S rRNA gene sequencing, we sought to elucidate the effects of a cocultivation of Chlorella vulgaris, Scenedesmus species, and Spirulina platensis cocultivation on the bacterial communities in the rearing tanks and the biofilter of a garlic (Allium sativum L.) and Nile tilapia (Oreochromis niloticus L.) aquaponic system during a 56‐days experiment. Feed intake, weight gain, and survival rates of Nile tilapia significantly improved in experimental groups cocultivated with microalgae compared to the control group, while garlic plant biomass, leaf number, and shoot length were not significantly different from the control. Alpha‐diversity analysis revealed significantly higher richness and evenness in the bacterial communities from the biofilter and rearing tanks of the cocultivated systems when compared with the control system. The cocultivation also had a statistically significant effect on the bacterial composition: nonmetric multidimensional scaling analysis of a Bray–Curtis dissimilarity matrix demonstrated unique clustering patterns, indicating distinct bacterial communities in the biofilter and rearing tank water cocultivated with microalgal strains. We found significantly decreased abundances of the potentially pathogenic bacterial genera Janthinobacterium, Aeromonas, Pseudomonas, and Flavobacterium in aquaponic systems cocultivated with microalgae when compared to the control. Furthermore, the beneficial bacterial genera Fusibacter, Geothrix, Thiobaca, and Treponema were significantly enriched in the microalgae cocultivated systems. The results clearly demonstrate that integrating microalgae into an aquaponic recirculating aquaculture system (RAS), not only improves weight gain and survival rates of Nile tilapia, but also enriches beneficial bacterial genera and reduces potentially pathogenic microorganisms, offering a promising strategy to reduce antibiotic use and enhance water quality in aquaponics, without growth impairments of cocultivated plants.

In this study, the effects of dietary supplementation of Indian Sphagnum junghuhnianum peat moss pectin were evaluated in Catla catla fingerlings. A total of 375 fish (10.47 ± 0.2 g) were randomly divided (n = 25/tank) into basal diet (Sphagnum peat moss pectin [SPMP] at 0% control) (crude protein: 37%, crude fat: 8%) or four treatment diets, 2% (SPMP2), 4% (SPMP4), 8% (SPMP8), and 16% (SPMP16) for 60 days. The water temperature was 27.5 ± 0.6°C, and fish were fed with the experimental diets at 4% of their live body mass. The results of this research revealed that the SPMP8 diet substantially enhanced growth indices in catla fingerlings (p < 0.05). The highest and lowest whole‐body lipid levels were in SPMP8 (5.03%) and control (4.06%), respectively. The gut amylase activity was significantly higher in the SPMP8 group, while lipase and protease remained unchanged. Additionally, fish given 8% and 16% SPMP had a significant decrease in the liver’s malondialdehyde concentration. Superoxide dismutase (SOD) activity was increased in SPMP‐supplemented groups, with the highest value in group SPMP8 while catalase (CAT) activity was higher in SPMP4, SPMP8, and SPMP16 compared to the other groups. Supplementing the diet with 4%–16% SPMP increased the fish’s red blood cell count and hemoglobin level. An 8% SPMP diet increased white blood cell count, phagocytic activity, lysozyme, acid, and alkaline phosphatase (AKP) activities compared to the other groups. The cumulative mortality of fish after challenge with virulent Aeromonas hydrophila significantly decreased in SPMP8 and SPMP16 groups, compared to the other treatments. The results of this study indicated enhancements in immunological markers, specifically an increase in levels of AKP, SOD, and CAT. This research proposes that providing catla fingerlings with 8% SPMP effectively boosts their growth, immune response, and disease resistance.

White spot syndrome virus (WSSV) is a highly infectious virus that poses an imminent threat to global shrimp aquaculture and is responsible for significant mortality in shrimp farms. There is a lack of targeted drug therapy options for preventing or treating WSSV. Consequently, these envelope proteins have garnered attention as an alternative focus for drug development at the molecular level. In the current study, the binding efficiency of pregnane‐3,20‐dione, 17,21‐[(methylborylene)bis(oxy)]‐, (5. beta)‐, a compound identified from Turbianria ornata, was predicted. The target proteins were major envelope proteins VP28, VP24, and VP110 of WSSV. The ligand structure was generated using PubChem and the SMILES platform. Docking was performed using AutoDock 4.2, employing blind docking to identify the preferred binding sites autonomously. A 100‐nanosecond molecular dynamics (MD) simulation was conducted for each protein–ligand complex using Desmond software to evaluate the stability and dynamics of these interactions. The complexes exhibited minimum values for both docking scores and binding energies. The additional data on root mean square deviation (RMSD) and root mean square fluctuation (RMSF) further supported the stability of proteins and ligands. The compound’s strong and stable binding with multiple WSSV envelope proteins suggests its potential as a broad‐spectrum antiviral agent against WSSV. The study found that the compound pregnane‐3,20‐dione, 17,21‐[(methylborylene)bis(oxy)]‐, (5. beta)‐ demonstrated high binding affinity Turbinaria ornata and stability with the viral envelope proteins VP28, VP24, and VP110, indicating strong antiviral potential against WSSV.