Search Results (2,841)

Optimizing oxygen supply and nitrogen removal in recirculating aquaculture systems (RAS) requires species-specific metabolic benchmarks. This study quantified the effects of body size and stocking density on oxygen consumption and total ammonia nitrogen (TAN) excretion in the silverside Odontesthes bonariensis under controlled RAS conditions. A 2 × 2 factorial design was used to compare small (48–140 g) and large (>140–250 g) fish stocked at low (3.2 kg m⁻³) and high (6.2 kg m⁻³) densities. Oxygen consumption was significantly influenced by both factors, with mean routine rates ranging from 146.12 ± 35.07 mg O₂ kg⁻¹ h⁻¹ in high-density large fish to 226.31 ± 50.71 mg O₂ kg⁻¹ h⁻¹ in low-density small fish. Smaller fish exhibited higher mass-specific rates, and individuals held at lower densities consumed more oxygen, consistent with allometric scaling and density-dependent metabolic suppression. In contrast, TAN excretion was unaffected by size or density, with mean values ranging from 4.59 ± 0.77 to 10.81 ± 3.76 mg TAN kg⁻¹ h⁻¹ across treatments, indicating stable protein catabolism under a uniform feeding regime. Both parameters displayed pronounced diurnal fluctuations, with postprandial peaks associated with specific dynamic action: oxygen consumption fluctuated between 61.75 and 333.03 mg O₂ kg⁻¹ h⁻¹, while TAN excretion ranged from 0 to 78.63 mg TAN kg⁻¹ h⁻¹ over 24 h cycles. These findings demonstrate that oxygen demand in O. bonariensis is strongly modulated by bioenergetic scaling and stocking density (ranging from 146 to 226 mg O₂ kg⁻¹ h⁻¹), whereas ammonia excretion (4.6–10.8 mg TAN kg⁻¹ h⁻¹) is primarily driven by dietary input. These results provide species-specific baseline benchmarks for aeration sizing and biofilter design, thereby supporting the sustainable intensification of silverside aquaculture in RAS. Full article

Praziquantel (PZQ) is a widely used antiparasitic drug in aquaculture; however, data on its environmental fate, tissue distribution, and metabolite kinetics in fish following bath treatment remain limited, particularly with respect to its metabolites. This study investigated the long-term elimination of PZQ and its two major metabolites, trans-4-hydroxypraziquantel (TPZQ) and cis-4-hydroxypraziquantel (CPZQ), in water and selected biological matrices of grass carp (Ctenopharyngodon idella) following a 24 h therapeutic bath with PZQ administered at 4 mg/L. Results showed a rapid decrease in PZQ in water after the transfer of fish to clean water, accompanied by a transient increase in its metabolites, with TPZQ as the predominant metabolite. PZQ tissue residues were highest in the hepatopancreas, caudal kidney, and skin, where the parent compound remained detectable up to day 14 of the experiment. Among the metabolites, higher concentrations of CPZQ were detected across all examined tissues; however, its elimination rate was faster than that of TPZQ. This difference was most pronounced in plasma and skin, where TPZQ remained detectable until day 7 of the experiment, whereas the cis-form was detected only up to day 3. Similar to the parent compound, the highest concentrations of both monitored metabolites were observed in the hepatopancreas and caudal kidney, where they remained detectable until day 7 of the experiment. These findings provide comprehensive insight into the distribution and elimination of PZQ in grass carp following 24 h bath administration and contribute valuable data that may support environmental risk assessment and future withdrawal-period evaluation in aquaculture. Full article

Marine by-products, including fishery discards, seafood-processing residues, aquaculture wastes, crustacean shells, and seaweed-derived side streams, are heterogeneous feedstocks rich in proteins, lipids, minerals, chitinous materials, polysaccharides, and bioactive compounds. This review examines insect-mediated bioconversion as a controlled biorefinery strategy for transforming these unstable marine residues into functional aquafeed ingredients and value-added bioproducts. We compare major marine feedstock classes and industrially relevant insects, with emphasis on substrate–insect matching, moisture control, salinity, lipid and ash load, texture, spoilage risk, and safety. Particular attention is given to how marine substrates can tailor insect meal, insect oil, chitinous fractions, hydrolysates, frass, and functional feed additives. The review further summarizes aquafeed applications of insect-derived products, including fishmeal and fish-oil replacement, protein and amino acid quality, lipid enrichment, gut health, immunity, and disease resistance in aquatic animals. Microbiome-assisted strategies, such as fermentation, enzymatic pretreatment, and gut or substrate microbial management, are discussed as tools to improve substrate stability, digestibility, and product quality. Finally, safety, regulation, scale-up, life cycle assessment, and techno-economic issues are considered. Overall, marine insect biorefineries should be optimized not only for biomass yield, but also for product quality, traceability, and application-specific safety. Full article

Largemouth bass (Micropterus salmoides) is a major aquaculture species in China. Facility-based aquaculture, such as the “168” model, a high-efficiency recirculating system using funnel-shaped ponds, has promoted water conservation and improved aquaculture efficiency through structural innovation. However, fish die sporadically as the stocking density increases with increasing fish growth. To address this issue, three density groups were established, namely, low (2.5 ± 0.5 kg/m³), medium (4.0 ± 0.5 kg/m³), and high (7.5 ± 0.5 kg/m³). Histological examinations, biochemical assays, and transcriptomic and metabolomic analyses of liver tissues were performed, and fish health was comprehensively evaluated. Histopathological analysis revealed that progressive hepatic vacuolization and severe tissue damage occurred as the fish density increased. Biochemical indicators revealed that the immune system and growth underwent compensatory activation at medium density, shifting to immune suppression, growth impairment, and hepatic exhaustion at high density. Integrated omics analysis revealed that under medium-density stress, the urea cycle was impaired; under high-density stress, Ser metabolism in the liver was rerouted, potentially to overcome methyl donor depletion and prevent disorders of polyamine metabolism, accompanied by a gradual transition from compensatory activation to functional exhaustion. These findings improve our understanding of the physiological response mechanisms of fish to high-density stress. This study provides a theoretical basis for optimizing high-density aquaculture technologies such as the “168” model. Full article

Grass carp (Ctenopharyngodon idella) is a major freshwater aquaculture species in China, but its growth is limited under intensive high-density farming. This study aimed to investigate the characteristics of plasma exosomes associated with distinct growth performance by isolating and characterizing exosomes from fast- and slow-growing grass carp after nine months of culture. Exosomes showed typical morphology and expressed characteristic markers (CD63, CD81, TSG101). Small RNA sequencing identified 3325 miRNAs, with 177 highly abundant miRNAs differentially expressed: immune-related miRNAs were upregulated, while development-inhibitory miRNAs were downregulated in fast-growing fish. Target gene enrichment highlighted pathways in neural and skeletal development and amino acid metabolism. Integrative analysis across tissues revealed 26 miRNAs with coordinated expression patterns between plasma exosomes and brain, liver, or muscle, validated by qPCR. DIA proteomics quantified 4203 proteins, identifying 843 differentially enriched proteins linked to immune response, energy metabolism, and endoplasmic reticulum stress. Notably, TYMP was upregulated in muscle and exosomes, while several proteins (e.g., GYG2, BHMT) showed coordinated downregulation across tissues and exosomes in large fish. These results provide comprehensive evidence of exosome-mediated cross-tissue communication in teleosts and suggest a potential role for plasma exosomal miRNAs and proteins as non-invasive biomarkers correlated with growth status in aquaculture. Full article

Underwater optical sensor networks are essential for fish monitoring, yet imagery is often affected by illumination variability, low contrast, and complex backgrounds. Attention mechanisms are vital for feature representation in deep networks, yet existing approaches often struggle with spatial information loss and limited multi-scale interaction under such challenging conditions. This paper introduces Convolution to Interactive Capture and Recalibration Enhancement (C2ICARE), a lightweight attention module designed to overcome these challenges. The principal contribution of C2ICARE is the adaptation of memory interaction principles into an edge-oriented attention framework that enhances feature discrimination while maintaining computational efficiency. The architecture employs three core innovations: a 1:3 memory-feature split to preserve context while reducing cost, parallel multi-scale depthwise convolutions (3 × 3 and 7 × 7) for fine-grained and broad feature extraction, and a cross-branch interaction mechanism coupled with a ConvNeXt-style feed-forward network that avoids dimensionality reduction. Experimental results on an underwater fish dataset demonstrate that YOLO26n with C2ICARE achieves a mean average precision (mAP@0.5:0.95) of 0.7033, outperforming Coordinate Attention (+3.8%), FasterBlock (+1.7%), and CBAM (+0.4%) while adding only 0.05M parameters and 0.16 GFLOPs. Multi-objective Pareto Frontier analysis confirms that C2ICARE provides an effective balance between accuracy, efficiency, and generalization for resource-constrained deployment. EigenCAM visualizations further validate that the model focuses on biological morphology rather than background noise. Its lightweight design enables seamless integration with underwater sensor networks and fog platforms for real-time fish detection in aquaculture, commercial fisheries, and scientific research. Future work will investigate broader marine applications and cross-platform deployment scenarios. The code is available on GitHub. Full article

Ammonia nitrogen is one of the most common environmental stressors in aquaculture water environments, and its accumulation can induce physiological disturbance, altered ventilation regulation, and abnormal behavioral responses in fish. To achieve non-invasive quantitative characterization of rainbow trout responses to ammonia nitrogen stress, this study developed a computer-vision-based framework for the integrated analysis of locomotor behavior and ventilation activity. Rainbow trout were exposed to four ammonia nitrogen concentrations: 0, 15, 30, and 60 mg/L. A total of 16 rainbow trout were used in this study, with an average body length of 14.0 ± 1.0 cm and an average body weight of 38.65 ± 2.42 g. The fish were assigned to four experimental aquaria, with four fish maintained in one aquarium for each TAN treatment. Stereo videos for locomotor behavior analysis and monocular mouth-region videos for ventilation analysis were simultaneously collected, and the final 5 min of each recording was analyzed. YOLOv11n, multi-object tracking, and stereo vision were used to extract three-dimensional position sequences of rainbow trout and calculate the amount of exercise, average swimming speed, and spatial distribution. Meanwhile, optical-flow analysis was applied to quantify mouth opening–closing motion and estimate ventilation frequency. The results showed that with increasing ammonia nitrogen concentration, rainbow trout locomotor behavior tended to be suppressed, with average swimming speed showing the clearest decrease, whereas ventilation frequency continuously increased. Average swimming speed decreased from 3.83 cm/s in the 0 mg/L group to 1.03 cm/s in the 60 mg/L group, while ventilation frequency increased from 84.91 breaths/min to 133.43 breaths/min. Compared with locomotor indicators, ventilation frequency showed a more stable response to changes in ammonia nitrogen concentration. This study achieved the synchronous quantification of rainbow trout locomotor behavior and ventilation activity, revealing a differentiated response pattern characterized by enhanced ventilation and suppressed locomotor behavior under acute ammonia nitrogen stress. These findings provide a methodological reference for fish stress assessment and risk warning in aquaculture environments. Full article

The silver pomfret (Pampus argenteus) is a high-value marine food fish, but its aquaculture is limited by juvenile intestinal immaturity, characterized by impaired digestion, barrier dysfunction, and microbial dysbiosis. This study evaluated whether early-life dietary inulin could improve intestinal health and muscle nutritional composition. After an 8-week feeding trial, fish fed a 5 g/kg inulin-supplemented diet showed improved growth performance, as reflected by higher final body weight (+17.2%), WGR (+18.5%), and SGR (+6.4%) than the control group. These benefits were associated with enhanced intestinal morphology, increased α-amylase and lipase activities, upregulated expression of tight junction genes, and a remodeled gut microbiota. These gut-associated changes were accompanied by improved selected muscle compositional traits. Specifically, inulin supplementation enriched essential amino acids, including methionine and threonine, as well as flavor-related amino acids, such as glutamate, glycine, and serine. Meanwhile, the muscle lipid profile was also modified, as reflected by reduced levels of selected saturated fatty acids and increased levels of monounsaturated fatty acids, particularly oleic acid. Collectively, our findings suggest that early-life dietary supplementation with 5 g/kg inulin may support intestinal homeostasis-related indicators and improve selected muscle nutritional traits in farmed silver pomfret. Full article

To address the quality divergence between wild and cage-farmed red sea bream (Pagrus major), we conducted a comparative analysis of their proximate composition, fatty acid and amino acid profiles, and chromatic characteristics across varying size and growth stages. Farmed fish exhibited substantial lipid deposition (peaking at 4.77% in F4), yielding a high relative percentage of n-3 long-chain polyunsaturated fatty acids. In contrast, wild fish maintained a leaner muscle profile (<2.43% lipid) and were uniquely characterized by an elevated abundance of C22:1n-9 (up to 11.52%), distinguishing them from farmed cohorts. Regarding sensory quality, large-sized wild specimens contained significantly higher concentrations of delicious amino acids (DAA, up to 8.83 g/100 g), particularly glycine and alanine, indicating a superior flavor profile. Colorimetric analysis demonstrated that wild fish maintained vivid reddish pigmentation in the caudal fin (a* = 8.73), whereas farmed fish exhibited marked skin darkening. These findings elucidate a distinct phenotypic and nutritional divergence: intensive farming enhances overall somatic lipid retention, while natural marine environments optimize flavor-active amino acid accumulation and visual appeal, providing critical baseline markers to guide precision aquaculture. Full article

Saline–alkaline aquaculture is a promising strategy to alleviate freshwater shortages; however, such environments severely impair fish growth and physiological homeostasis. Nutritional regulation has been proposed to improve stress tolerance, yet the benefits of single additives are often limited under the multifactorial challenges imposed by saline–alkaline conditions. Therefore, a compound feed additive (CFA) consisting of glutamate, cholesterol, β-glucan, myo-inositol, zinc methionine, and curcumin was developed and evaluated in Nile tilapia (Oreochromis niloticus). To assess the robustness and practical applicability of this nutritional strategy, three independent feeding trials were conducted using different commercial basal diets as validation systems. Within each dietary system, fish were reared under freshwater (FW), saline–alkaline water (SAW), or saline–alkaline water supplemented with CFA (SAW+CFA). Saline–alkaline stress significantly reduced WG and SR, increased FCR, and elevated VSI and HSI, indicating impaired growth performance and metabolic burden. These changes were accompanied by increased serum glucose and ion concentrations (Na⁺, K⁺, Cl⁻), elevated ammonia levels, and reduced crude protein content. Dietary CFA improved growth and feed utilization under saline–alkaline conditions. It enhanced hepatic glycogen content and reduced serum glucose levels. Meanwhile, it downregulated glycolysis-related genes (hk, pfk1, pk) and upregulated genes involved in gluconeogenesis and the pentose phosphate pathway (g6pase, pc, g6pdh), indicating altered glucose metabolism and improved energy homeostasis. Saline–alkaline stress induced oxidative stress, apoptosis, and histological damage in the liver, whereas CFA alleviated these alterations by reducing MDA levels, enhancing antioxidant enzyme activities (CAT, GSH-Px, T-SOD) and suppressing apoptosis-related genes (caspases, p53, c-myc). In addition, CFA alleviated saline–alkaline stress-induced gill structural damage and reduced serum ion concentrations while modulating ion transport-related gene expression, suggesting improved osmoregulatory capacity. It also enhanced ammonia metabolism and transport, as reflected by reduced serum ammonia levels and altered expression of related genes. Furthermore, Saline–alkaline stress impaired intestinal structure and function, whereas CFA improved intestinal villus structure, increased digestive enzyme activities (amylase, trypsin, lipase), and suppressed pro-inflammatory genes (il-1β, il-8). Importantly, similar beneficial response patterns were observed across the three independently analyzed dietary systems. Overall, CFA improved saline–alkaline adaptability of Nile tilapia and was associated with improvements in energy metabolism, oxidative homeostasis, osmoregulation, ammonia detoxification, and intestinal function, providing a practical nutritional strategy for saline–alkaline aquaculture. Full article

To achieve non-contact and continuous monitoring of body length in Micropterus salmoides and overcome the stress damage and subjective error associated with traditional manual measurement, this paper proposes an improved YOLOv8-based multi-target tracking framework for intensive recirculating aquaculture systems. The system employs a geometric measurement framework based on monocular vision that achieves conversion from pixel coordinates to actual body length through camera calibration, water-surface refraction correction, and pose projection correction. Under a collaborative optimization framework integrating detection and tracking, the model incorporates multi-scale feature enhancement, lightweight re-identification (ReID), and a robust data association mechanism, which improves system stability under conditions of high fish density, variable illumination, and turbid water. A shallow feature fusion path is introduced to enhance small-target perception, and a MobileNetV3_ReID model is adopted to extract highly discriminative appearance features, which improves identity consistency while maintaining model compactness. In the data association stage, a hybrid cost matrix integrating IoU, cosine similarity, and motion consistency is constructed, and optimal matching is realized through the Hungarian algorithm. Dynamic threshold adjustment and an exponential moving-average feature-update strategy are introduced to effectively suppress identity switching. Experiments were conducted on an overhead video dataset of Micropterus salmoides collected at a recirculating aquaculture system facility. The results show that the proposed method achieves 82.7% mAP50 while maintaining a real-time throughput of 88 FPS, with MOTA reaching 76.9% and IDF1 reaching 81.5%—the latter representing an improvement of 3.2 percentage points over BoT-SORT and 5.3 percentage points over the YOLOv8 baseline tracker. The number of identity switches (IDSW) decreased from 89 in the baseline configuration to 39, a reduction of 56.2%. Crucially, these component-level improvements translate into a body length error (BLE) of 5.2 ± 1.8% (MAE = 1.35 cm, Pearson r = 0.972), representing a 38.8% improvement over the baseline BLE of 8.5% and satisfying the 5–10% tolerance required for aquaculture growth monitoring. Ablation analysis confirms that both detection enhancements (contributing −1.3% BLE) and tracking optimizations (contributing −2.0% BLE) are necessary to achieve this application-level accuracy. Full article

The increasing spread of invasive alien species (IAS) represents one of the major causes of biodiversity loss, making containment practices necessary. In this regard, the circular economy framework proposes to reuse the biomass from IAS in growing sectors such as aquaculture, in which more sustainable practices are required. This study evaluated the possibility of using biomass derived from two widespread freshwater IAS, Procambarus clarkii and Silurus glanis, as dietary ingredients for Oncorhynchus mykiss. Experimental diets were formulated by incorporating 20% of IAS-derived muscle powder into a commercial feed, and their effects were assessed through a 35-day feeding trial. Chemical analyses confirmed the nutritional suitability of the formulated diets and the absence of antibiotic residues. No mortality or significant differences in growth performance were observed among treatments. Blood biochemical parameters showed limited variations, remaining within physiological ranges, while oxidative stress biomarkers indicated only minor, diet-specific responses without evidence of oxidative damage. An increase in Hsp70 expression suggested adaptive physiological responses rather than pathological stress. Histological analyses of liver and gut tissues revealed no structural alterations across experimental groups. Overall, the results demonstrate that the inclusion of IAS-derived biomass at 20% is well tolerated by O. mykiss and does not impair fish health. These findings support the potential of invasive species valorization as a sustainable strategy for aquaculture feed production, contributing to both resource efficiency and ecosystem management. Full article

Short-term fluctuations in dissolved oxygen are difficult to capture in warm outdoor Nile tilapia (Oreochromis niloticus) ponds using periodic manual measurements, yet they strongly influence fish performance and farm management. This study presents a preliminary field evaluation of a low-cost IoT workflow for dissolved oxygen monitoring and short-horizon forecasting in pond-based tilapia culture. An ESP32-based sensing node continuously measured dissolved oxygen, temperature, and pH, transmitted readings to a cloud backend, and generated short-horizon forecasts from 5 min aggregated windows. During live validation from 1 to 10 April 2026, the 30 min forecast achieved a mean absolute error of 0.783 mg/L and directional accuracy of 60.23%, with only modest improvement over a persistence baseline. The 6 h forecast achieved 1.109 mg/L and 53.82%, respectively, indicating limited predictive value at the extended horizon. An extended 47-day field deployment (May–June 2026) captured four sensor-recorded low-DO events and two documented power outages, causing sensor downtime and providing additional field-deployment evidence. These results demonstrate the engineering feasibility of the integrated workflow, but they do not establish robust operational forecasting validity because the data were collected from one pond, high-frequency records were temporally correlated, and independent reference-meter validation was not available. The study is, therefore, best interpreted as a proof-of-concept field evaluation that identifies practical requirements for future low-cost aquaculture forecasting systems. Full article

In cage aquaculture, precise estimation of fish biomass is critically important for determining appropriate feeding strategies and evaluating production capacity. Currently, prevailing fish counting approaches heavily rely on acoustic or optical technologies. However, the accuracy and reliability of the obtained data are largely compromised by factors such as fish occlusion and water turbidity in practical cage farming environments. To address this limitation, this study proposed a novel method for estimating fish population size deduced from dynamic feeding information, based on the model integrated environmental and biological factors, feed intake and biomass. A 10-week feeding experiment was carried out to collect multidimensional data including feed intake, growth parameters, and environmental variables to construct a dataset correlating feeding amount with primary influential factors. Herein a bioenergetics-informed radial basis function neural network, optimized via particle swarm optimization (BE-PSO-RBF), was developed based on those empirical data. Model validation using 47 independent test samples showed that the hybrid model achieved a mean absolute error (MAE) of 26.82, a root mean square error (RMSE) of 35.62, and a mean absolute percentage error (MAPE) of 4.14%, confirming its robust generalization performance. These findings suggest that feed-intake-based population estimation may provide a feasible complementary approach for fish population assessment under cage farming conditions similar to those investigated in this study. Full article

The gut microbiome of rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar) is increasingly recognized as a functional interface linking dietary inputs, epithelial barrier integrity, mucosal immunity, environmental stress, disease susceptibility, and antimicrobial-resistance risk in intensive aquaculture. Based on available salmonid studies and relevant evidence from broader fish and aquaculture systems, this review synthesizes current knowledge on salmonid gut microbial composition, nutritional modulation, microbiome–mucosal immune interactions, aquaculture stressors, antibiotic exposure, antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), metagenomics, multi-omics, and emerging microbiome-informed decision-support tools. Current evidence does not support a universally stable single-core microbiota in these species. Instead, community structure is shaped by developmental stage, freshwater–seawater transition, intestinal segment, digesta versus mucosa sampling, diet, temperature, stress, health status, and methodological workflow. Feed substitution and functional additives can remodel the gut microbiota, but these shifts should be interpreted alongside histology, barrier function, metabolic profiles, immune indicators, and disease-resistance phenotypes. Antibiotic exposure may reduce acute bacterial disease pressure while disturbing community structure and potentially enriching ARGs or ARG–MGE associations. Risk assessment should therefore move beyond ARG abundance toward host–ARG–MGE linkage using shotgun metagenomics, metagenome-assembled genomes, long-read sequencing, Hi-C, and externally validated multi-omics models. Machine learning and artificial intelligence approaches may support feature screening, risk stratification, and decision support, but their application in salmonid gut-health management remains at an early stage and requires external validation across sites, production stages, diets, and seasons. Full article