Search Results (1,587)

Biofouling communities are usually managed as pests in aquaculture, yet their natural proliferation in fish farms makes them also promising IMTA extractive components. The growth and biomass production of four dominant macrofoulers, Mytilus galloprovincialis (mussels), Sabella spallanzanii (polychaete worms), Phallusia mammillata and Styela plicata (ascidians), were evaluated under a novel IMTA system in the Ionian Sea (southern Italy). Coconut-fiber ropes (10 m) were deployed around fish cages in October 2022 and monitored over a 1-year cycle. Monthly density, length-frequency and cohort analyses combined with species-specific length-weight relationships were used to estimate target species’ growth and biomass. Mytilus and Sabella showed single-cohort dynamics, with densities steadily declining over time, whereas ascidians displayed continuous recruitment allowing for additional rope-deployment windows. Specific growth rates in length were significantly higher in Phallusia and Sabella (≈25% month⁻¹) than in Mytilus and Styela (≈17 and 22% month⁻¹). Total macrofouling biomass (live weight) increased from ≈350 kg in May to a peak of ≈2500 kg in August, remaining as high in October. Mytilus and Sabella accounted for 60–80% of total biomass while ascidians contributed 20–40%. Beyond environmental restoration, this multispecies biomass offers several potential commercial opportunities and could be further valorized through biorefinery-based cascading extraction, including final conversion into bioenergy. Overall, IMTA could leverage traditionally undesired fouling organisms as multifunctional crops, enhancing bioremediation while supporting circular blue-bioeconomy principles. Future research should focus on optimizing rope deployment timing, harvesting strategies, and biomass valorization pathways to fully exploit the emerging potential of integrating multispecies fouling biomass within IMTA systems. Full article

Inspired by the Tesla valve, the island-type fishway is a novel design whose biological performance remains unelucidated. This study integrated hydraulic experiments, CFD modeling, and 3D computer vision to investigate the passage performance and swimming behavior of juvenile silver carp (Hypophthalmichthys molitrix). The results confirmed high biological feasibility, with upstream success rates exceeding 70%. The island and arc-baffle configuration create a heterogeneous flow field with an S-shaped main flow and low-velocity zones; each island unit contributes 8.9% to total energy dissipation. Critically, fish utilize a multi-dimensional navigation strategy to avoid high-velocity cores: temporally adopting an intermittent “rest-burst” pattern for energetic recovery; horizontally following an “Ω”-shaped bypass trajectory; and vertically preferring the bottom boundary layer. Passage failure was primarily linked to suboptimal path selection near the high-velocity main flow. These findings demonstrate that fishway effectiveness depends less on bulk hydraulic parameters and more on the spatial connectivity of hydraulic refugia aligning with fish behavioral traits. This study provides a scientific basis for optimizing eco-friendly hydraulic structures. Full article

Aquaculture faces environmental challenges from sediment contamination by potentially toxic elements. This study investigated how aquaculture patterns and seasons jointly affect the distribution and ecological risks of these potentially toxic elements in sediments. By analyzing and comparing sediment samples from different aquaculture systems across seasons, we found that Mn (mean = 435.42 mg/kg) was the most abundant, followed by Zn (mean = 172.69 mg/kg), Cr (mean = 106.79 mg/kg), and Cu (mean = 63.44 mg/kg). Aquaculture patterns were the primary factor determining the composition of potentially toxic elements, followed by season. Fish farming tended to promote their accumulation in sediments, whereas the rice–crayfish co-culture model effectively reduced the enrichment of potentially toxic elements and their associated ecological risks. Therefore, optimizing aquaculture practices proves more effective in controlling these risks than managing seasonal variations. Moreover, total phosphorus was identified as a key driver of potentially toxic element accumulation in sediments. The results from the rice–crayfish co-culture system indicate that enhanced phosphorus management is crucial for mitigating such risks. Accordingly, it is necessary to develop systematic monitoring and integrated remediation strategies focused on priority metals and their main drivers. Full article

Fish skin, a by-product of commercial fish processing, represents a viable source of type I collagen. Acetic acid has been widely used for the extraction of collagen from fish skin because it can preserve the native structure. However, it requires an extraction time of more than 72 h and complex and time-consuming dialysis steps to remove acetic acid residues from the extracted collagen which can otherwise cause inferior structural modifications. Therefore, this study describes a simple time- and cost-effective method to extract collagen using hydrochloric acid. The experiments focused on understanding the behavior of fish skin and changes in the extraction medium. The extraction procedure developed in this study includes treatment with a 0.01 M hydrochloric acid solution at a 1:20 mass to volume ratio for 5 h, followed by homogenization. The native triple-helical structure of collagen was confirmed by ATR-FTIR and circular dichroism spectroscopy. Thermal stability was confirmed by differential scanning calorimetry. This study also provides guidelines for the application of this knowledge to skin of any fish species of interest: (i) an upper limit of pH 4 during collagen extraction; (ii) a manageable viscosity of the collagen extract solution; and (iii) as few undissolved skin pieces as possible after homogenization. Full article

Amid the intensifying global mandate for sustainable aquafeed strategies, this study investigates the functional efficacy and biochemical implications of black soldier fly larvae oil (BLO), extracted via recently approved patent method depending on cold-aqueous process, as a substitute for conventional fish oil (FO) in zebrafish (Danio rerio) diets. The refined extraction technique, representing an advancement over traditional aqueous methodologies, was engineered to selectively preserve bioactive lipid fractions while minimizing environmental footprint and processing residues. Over a 28-day feeding period, adult zebrafish were allocated into triplicate groups and fed diets comprising 0%, 50%, and 100% substitution of FO with BLO and growth, lipid composition, and dietary fatty acid profiles of both diets and flesh were rigorously evaluated. Zebrafish fed the BLO₁₀₀ diet exhibited the most pronounced somatic growth (2.47 ± 0.01 g), significantly elevated specific growth rates (3.88 ± 0.82% day⁻¹), and the most efficient feed conversion, without compromising survival. Flesh lipid analysis revealed a substantial enrichment in saturated fatty acids—most notably lauric acid (C12:0)—corresponding to increasing dietary BLO levels. Although dietary EPA and DHA levels were reduced, DHA concentrations in fish tissues remained comparable to those of the control group, indicating a compensatory capacity mediated by endogenous elongation and desaturation pathways. These findings substantiate the dual potential of BLO as both a nutritionally viable lipid source and a vector for enhancing aquafeed sustainability. The cold-aqueous extraction method demonstrated here underscores a pivotal advancement in green lipid processing, aligning oil quality with ecological stewardship. This integrative approach not only reinforces BLO’s candidacy as a strategic fish oil substitute but also delineates a pathway toward scalable, species-adapted feed innovation. Future investigations should prioritize the modulation of fatty acid profiles through dietary and extraction optimization to fully realize the translational potential of insect-derived lipids in aquaculture. Full article

With increasing contamination in aquatic ecosystems, effective monitoring is crucial to preserve biodiversity and protect public health. This study quantified bioindicators (red swamp crayfish (Pcla), Genji-firefly (Lcr2), Ayu fish (Paa), and caddisfly (Sma)), microbial source tracking markers (ruminants (BacR), pigs (Pig2Bac), and humans (gyrB)), and a fecal indicator bacterium (Escherichia coli (sfmD)) using quantitative PCR on river water samples collected every 2 h between 21 and 22 July 2023 (from the Omo and Bingushi Rivers in Yamanashi Prefecture, Japan). Initially, the optimal filter sizes of 1.0, 0.65, and 0.22 µm were evaluated, where the 0.65 µm filter yielded higher Paa concentrations (Kruskal–Wallis test, p < 0.05) and was used subsequently. BacR and Paa exhibited 100% detection in the Omo (13/13) and Bingushi (13/13) Rivers with concentrations of 5.0 log₁₀ and 5.5 log₁₀ copies/L, respectively. These concentrations were used to assess 24 h temporal variability, but no significant fluctuations or cyclical trends between morning, afternoon, evening, and night were observed in either river. The BacR–Paa pair exhibited perfect positive detection correlation (Φ = 1.0) and complete similarity (Jaccard Index = 1.0), but a moderate negative correlation of mean concentrations highlights the importance of considering habitat overlaps and behavioral synchronicity. Full article

AI enhances aquatic resource management by automating species detection, optimizing feed, forecasting water quality, protecting species interactions, and strengthening the detection of illegal, unreported, and unregulated fishing activities. However, these advancements are inconsistently employed, subject to domain shifts, limited by the availability of labeled data, and poorly benchmarked across operational contexts. Recent developments in technology and applications in fisheries genetics and monitoring, precision aquaculture, management, and sensing infrastructure are summarized in this paper. We studied automated species recognition, genomic trait inference, environmental DNA metabarcoding, acoustic analysis, and trait-based population modeling in fisheries genetics and monitoring. We used digital-twin frameworks for supervised learning in feed optimization, reinforcement learning for water quality control, vision-based welfare monitoring, and harvest forecasting in aquaculture. We explored automatic identification system trajectory analysis for illicit fishing detection, global effort mapping, electronic bycatch monitoring, protected species tracking, and multi-sensor vessel surveillance in fisheries management. Acoustic echogram automation, convolutional neural network-based fish detection, edge-computing architectures, and marine-domain foundation models are foundational developments in sensing infrastructure. Implementation challenges include performance degradation across habitat and seasonal transitions, insufficient standardized multi-region datasets for rare and protected taxa, inadequate incorporation of model uncertainty into management decisions, and structural inequalities in data access and technology adoption among smallholder producers. Standardized multi-region benchmarks with rare-taxa coverage, calibrated uncertainty quantification in assessment and control systems, domain-robust energy-efficient algorithms, and privacy-preserving data partnerships are our priorities. These integrated priorities enable transition from experimental prototypes to a reliable, collaborative infrastructure for sustainable wild capture and farmed aquatic systems. Full article

As agricultural heritage systems provide crucial ecosystem service functions, conducting functional zoning serves as a fundamental and essential approach to implementing the ecological civilization strategy and promoting targeted conservation and sustainable utilization. Taking the Mountain Spring Water Fish Farming System in Kaihua, Zhejiang, a site recognized as a China-Nationally Important Agricultural Heritage System, as a case study, this research integrates the equivalent factor method and the Self-Organizing Map neural network clustering method to evaluate ecosystem service values, identify ecosystem service clusters, and conduct ecological functional zoning. Protection and utilization strategies are subsequently proposed for each functional zone. The results show the following findings: (1) From 2005 to 2020, the total ecosystem service value of the system exhibited a fluctuating yet overall declining trend, decreasing by approximately 0.25%; (2) five ecosystem service clusters were identified, within which services generally showed synergistic relationships, while trade-offs were mainly concentrated between food provision and other ecosystem services; (3) based on these findings, the study area was divided into five functional zones—the Heritage Culture Core Zone, the Ecological Restoration and Conservation Priority Zone, the Industrial Integration and Development Zone, the Ecological–Industrial Transition and Optimization Zone, and the Multi-Value Protection and Exploration Zone. Specific protection and utilization strategies were proposed for each zone. This study provides a novel theoretical perspective and practical reference for rational ecological functional zoning, as well as the protection and sustainable use of agricultural heritage systems. Full article

This study investigates the predictive modeling of total Polycyclic Aromatic Hydrocarbon (PAH) concentrations in smoked fish products based on various smoking parameters using machine learning techniques in the Waikato Environment for Knowledge Analysis (WEKA) software environment. Key input variables included fish fat content, smoking temperature, and wood type, all of which were statistically significant predictors of PAH levels (p < 0.05). A multiple linear regression analysis conducted in SPSS revealed a strong correlation between predictors and PAH concentration (r = 0.801), with an explained variance of 64.1% (R² = 0.641) and a standard error of 3.52. Among the evaluated machine learning algorithms—Linear Regression, SMOreg, Multilayer Perceptron, M5P, Random Forest, and IBk—performance was assessed using five criteria: Correlation Coefficient, Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), Relative Absolute Error (RAE), and Root Relative Squared Error (RRSE). All models were validated using 10-fold cross-validation. For classification tasks based on fish species, Logistic Regression outperformed the Random Forest and J48 algorithms, indicating superior predictive capability. This integrated analytical framework demonstrates the effectiveness of machine learning in food safety monitoring and provides a scientific basis for optimizing smoking processes to mitigate PAH contamination. Overall, the findings underscore the practical value of machine learning tools in the predictive modeling of PAH contamination in smoked fish. The approach not only offers high predictive accuracy but also serves as a scientific framework for improving food safety by optimizing smoking conditions to minimize PAH formation. This integrated model can aid food technologists and manufacturers in establishing safer processing parameters while maintaining product quality. Full article

This paper presents two novel hybrid iterative schemes that combine Newton’s method and its variant with the Tuna Swarm Optimization (TSO) algorithm, aimed at solving complex nonlinear equations with enhanced accuracy and efficiency. Newton’s method is renowned for its rapid convergence in root-finding problems, and it is integrated with TSO, a recent swarm intelligence algorithm that surpasses the complex behavior of tuna fish in order to optimize the search for superior solutions. These hybrid methods are reliable and efficient for solving challenging mathematical and applied science problems. Several numerical experiments and applications involving ordinary differential equations have been carried out to demonstrate the superiority of the proposed hybrid methods in terms of convergence rate, accuracy, and robustness compared to traditional optimization and iterative methods. The stability and efficiency of the proposed methods have also been verified. The results indicate that the hybrid approaches outperform traditional methods, making them a promising tool for solving a wide range of mathematical and engineering problems. Full article

African catfish (Clarias gariepinus, AC) is one of the most widely farmed freshwater fish species in Central Europe. Processing operations generate up to 55% by-products (BPs), predominantly carcasses rich in proteins, lipids, and minerals. This study develops a comprehensive valorization process for ACBPs to recover gelatin, protein hydrolysate, fish oil, and pigments. The processing protocol consisted of sequential washing, oil extraction, demineralization, and biotechnological treatment to disrupt the collagen quaternary structure. A two-factor experimental design was employed to optimize the processing conditions. The factors included the extraction temperatures of the first (35–45 °C) and second fraction (50–60 °C). We hypothesized that enzymatic conditioning, combined with sequential hot-water extraction, would yield gelatin with properties comparable to those of mammalian- and fish-derived gelatins, while enabling a near-zero-waste process. The integrated process yielded 18.2 ± 1.2% fish oil, 9.8 ± 2.1% protein hydrolysate, 1.7 ± 0.7% pigment extract, and 25.3–37.8% gelatin. Optimal conditions (35 °C/60 °C) produced gelatin with gel strength of 168.8 ± 3.6 Bloom, dynamic viscosity of 2.48 ± 0.02 mPa·s, and yield of 34.76 ± 1.95%. Life cycle assessment (LCA) identified two primary environmental hotspots: water consumption and energy demand. This near-zero-waste biorefinery demonstrates the potential for comprehensive valorization of aquaculture BPs into multiple value-added bioproducts. Full article

Extreme weather events, particularly marine heatwaves (MHWs), increasingly threaten aquaculture systems worldwide by impairing animal physiology and economical sustainability. This showcases the need to develop nutritional approaches that enhance animal performance under sub-optimal conditions. This study evaluated the effects of dietary supplementation with the brown macroalga Laminaria digitata (whole dried powder or extract) on the antioxidant status, digestive activity, and lipid metabolism of juvenile Sparus aurata exposed to a simulated MHW. Fish were fed four diets (control, 0.3% extract, and 0.3% or 1.5% powder) for 30 days before being exposed to a category III Mediterranean MHW. Under optimal temperature, macroalgae supplementation reduced oxidative status (lower catalase activity). The powder-feeds decreased lipid peroxidation, while the extract-feed elicited the opposite. All supplemented diets reduced proteolytic activity, and the extract-feed also decreased amylase activity. The MHW impaired gastrointestinal antioxidant defenses and liver lipid metabolism, decreasing catalase and glutathione S-transferase activities, as well as ΣPUFA n-6, 16:1 n-7, and 18:2 n-6 levels. The 0.3% powder-feed mitigated MHW-induced reductions in antioxidant activity, while both 0.3%-diets prevented thermal stress-related alterations on fatty acid profile. Overall, L. digitata powder at 0.3% was most effective at enhancing thermal stress resilience, supporting its value as a functional aquafeed ingredient. Full article

Multi-fish tracking and behavior analysis in deep-sea cages face two critical challenges: first, the homogeneity of fish appearance and low image quality render appearance-based association unreliable; second, standard linear motion models fail to capture the complex, nonlinear swimming patterns (e.g., turning) of fish, leading to frequent identity switches and fragmented trajectories. To address these challenges, we propose SOD-SORT, which integrates a Constant Turn-Rate and Velocity (CTRV) motion model within an Extended Kalman Filter (EKF) framework into DeepOCSORT, a recent observation-centric tracker. Through systematic Bayesian optimization of the EKF process noise (Q), observation noise (R), and ReID weighting parameters, we achieve harmonious integration of advanced motion modeling with appearance features. Evaluations on the DeepBlueI validation set show that SOD-SORT attains IDF1 = 0.829 and reduces identity switches by 13% (93 vs. 107) compared to the DeepOCSORT baseline, while maintaining comparable MOTA (0.737). Controlled ablation studies reveal that naive integration of CTRV-EKF with default parameters degrades performance substantially (IDs: 172 vs. 107 baseline), but careful parameter optimization resolves this motion-appearance conflict. Furthermore, we introduce a statistical quantization method that converts variable-length trajectories into fixed-length feature vectors, enabling effective unsupervised classification of normal and abnormal swimming behaviors in both the Fish4Knowledge coral reef dataset and real-world Deep Blue I cage videos. The proposed approach demonstrates that principled integration of advanced motion models with appearance cues, combined with high-quality continuous trajectories, can support reliable behavior modeling for aquaculture monitoring applications. Full article

This work presents a numerical study of the water-exit characteristics of a bioinspired unmanned aerial-underwater vehicle (UAUV) equipped with a front-mounted propeller. A robust solution framework was established on the basis of a modified Shear Stress Transport (SST) turbulence model, volume of fluid (VOF) multiphase formulation, overset grid technique, and six degrees of freedom (6-DOF) motion model; the framework was verified against a canonical water-exit case of a sphere. Inspired by the morphology and water-exit behavior of flying fish, a bioinspired three-dimensional (3D) model was designed. Using this framework, the effects of the front-mounted propeller configuration, exit velocity, and exit angle were examined; the exit process under different conditions was analyzed; and the relationship between exit drag and exit state was quantified. The results demonstrate that the proposed approach can resolve the water-exit performance of the bioinspired UAUV in detail. Folding the front-mounted propeller effectively reduces exit drag and mitigates high-pressure concentrations on the blades. When the exit velocity is ≥8 m/s and the exit angle θ ≤ 30°, the peak exit drag does not surpass 90.004 N. The peak exit drag exhibits a pronounced quadratic relationship with both exit velocity and exit angle. To ensure safe water exit, the UAUV should avoid exiting with the front-mounted propeller deployed and avoid excessively low exit velocities and overly large exit angles. The numerical investigation of exit drag provides effective bioinspired design guidelines and a feasible analysis strategy for UAUV development. In conclusion, the findings provide crucial insights for designing more efficient bioinspired UAUVs, particularly in terms of minimizing water-exit drag and optimizing the configuration of the front-mounted propeller. Full article

In aquaculture and in laboratory settings, the development of sustainable and functional feeds is crucial in order to promote fish welfare, growth, and reproductive performance. Among natural dietary supplements, spirulina (Arthrospira platensis), a blue-green microalga rich in proteins, essential fatty acids, vitamins, and antioxidant molecules, represents a promising bioactive ingredient capable of influencing both physiological and behavioral traits. A 32-week longitudinal study was conducted on adult zebrafish (Danio rerio) to evaluate the effects of spirulina supplementation (5%, 25%, 50%, 75%, and 100%) compared to a standard diet. Parameters related to survival, growth, reproductive fitness, and reproductive behavior were assessed in vivo and supported by a morphometric analysis of the gonads. Supplementation with 5% improved survival rate and the Body Condition Index, while 25% supplementation increased survival, enhanced reproductive behavior and spawning success (140% egg production vs. control), and supported optimal gonadal development and gamete maturation timing. Higher percentages of spirulina (50–100%) seem to cause nutritional imbalance, impairing health and reproductive fitness. This study demonstrates that moderate spirulina supplementation (5–25%) supports health, reproductive physiology, and behavior in zebrafish in a dose-dependent manner. These results highlight the potential of spirulina as a functional supplement for precision nutrition approaches, with implications for fish welfare, reproductive performance, and aquaculture sustainability. Full article