Search Results (51)

In aquaculture practices, fish are mostly protected from lethal actions of predators. However, sub-lethal effects can be challenging to prevent, as they may be associated with chemical cues signaling predation risk that easily dissolve and spread in water, serving as potential stressors. These cues originate from predators, stressed or injured prey releasing blood, a conspecific alarm substance (CAS), and/or other bodily fluids. In this study, we simulated a small-scale net cage system and assessed the feeding and growth of Nile tilapia exposed chronically to a CAS. Nile tilapia, an invasive species in many aquatic systems, frequently coexist freely alongside those cultivated in cages. Consequently, caged tilapia may regularly be exposed to a CAS, potentially leading to chronic stress and impacting growth and development. Fish were exposed daily to either a CAS or a control vehicle (distilled water) for 45 days (one fish per cage). Fish in both conditions exhibited similar increases in body mass, weight gain, and length over time and displayed an allometric negative growth profile, indicating that the CAS did not affect the length–weight relationship as well. Specific and relative growth rates, condition factor, body axes, food intake, and feeding conversion efficiency were also unaffected by the CAS over time. This body of evidence suggests that the CAS did not act as a chronic stressor for caged Nile tilapia and a possible explanation is habituation. Full article

Popular foods such as sushi and sashimi depend on the quality of raw fish meat to maintain consumer satisfaction. Recently, dietary insect meal and insect-derived substances have been extensively studied for application in aquaculture as a protein alternative or immunostimulant. However, the impact of insect functional substances on the fish meat quality of teleosts remains unclear. Here, we investigated the influence of dietary inclusion of silkrose-BM, a novel bioactive polysaccharide derived from the silkworm, Bombyx mori, on the meat quality of yellowtail (Seriola quinqueradiata). This study was conducted by comparing two groups given different feeds, commercial EP and feeds containing Silkrose-BM (0.1%), after a culture period of six months in separate floating-net cages. The yellowtail were specifically cut into loins and several meat quality parameters were observed, including proximate, meat color changes, total collagen, drip loss, muscle histology, and gene expression (qRT-PCR). The results of the color-change analysis showed that discoloration of red muscle in the EP feed group occurred faster than in the silkrose-BM group, indicating an antioxidant property of silkrose-BM. Dietary silkrose-BM also significantly reduced drip loss and increased the total collagen content of yellowtail meat. Furthermore, qRT-PCR analysis showed that genes related to lipid and protein degradation were downregulated in the muscles of fish fed on silkrose-BM. In contrast, proximate analysis indicated no significant change in the nutritional composition of the meat between the groups. Taken together, our results suggest that dietary silkrose-BM could improve fish meat quality by minimizing protein denaturation and inhibiting lipid oxidation during fish meat storage. Full article

Aquaculture plays a crucial role in meeting the needs of a growing human population and achieving the sustainable development goals outlined in Agenda 2030. However, it is essential that this sector grows sustainably. In this study, we hypothesized that environmental sustainability decreases as the trophic level of farmed species increases and that it is higher in integrated systems compared to monocultures. To test these hypotheses, we conducted a comparative analysis of the environmental sustainability indicators of some aquaculture systems, including the farming of primary producers, filter feeders, and low-trophic phagotrophs. We compiled secondary data on eighteen environmental sustainability indicators from seven aquaculture systems. Five are monocultures, including the farming of macroalgae (Hypnea pseudomusciformis), oysters (Crassostrea gazar) in a tropical environment, oysters in a subtropical environment, as well as tambatinga (hybrid Colossoma macropomum × Piaractus brachypomus) and tambaqui (Colossoma macropomum). Additionally, two are integrated systems: tambaqui raised in hapa nets (small cage-like enclosures) within Amazon river prawn (Macrobrachium amazonicum) ponds, and tambaqui and prawns cohabitating freely in the same ponds. A benchmark tool was utilized to establish reference values for comparing indicators between the systems, and a method was developed to create environmental sustainability indices that integrate all indicators. Environmental sustainability tends to decrease as trophic levels rise, supporting the initial hypothesis. However, the data revealed that Integrated Multi-Trophic Aquaculture (IMTA) systems ultimately have lower environmental sustainability than monocultures, which was contrary to our expectations. Algae and oyster farming were found to be more environmentally sustainable than low-trophic fish farming systems. Among these, the integrated systems did not demonstrate significantly greater sustainability than the monocultures, as initially anticipated. To gain a comprehensive understanding of sustainability, further research on the social and economic sustainability of these systems is necessary. Full article

The aim of this study was to explore the effects of adding Lactobacillus plantarum (LAB) to a high-starch diet on glucose and lipid metabolism, gut microbiota, and the composition of metabolites in Megalobrama amblycephala. This experiment was equipped with three isonitrogenous and isoenergetic feeds as control group (LW), high starch group (HW), and high starch with LAB group (HP). A total of 180 experimental fish (13.5 ± 0.5 g) were randomly divided into three treatments, and three floating cages (1 m × 1 m × 1 m) were set up for each treatment. A total of 20 fish per net were kept in an outdoor pond for 8 weeks. The results showed that both the HW and HP groups had an altered structure and a reduced diversity of gut microbiota. LAB increased the abundance of Cetobacterium and the ratio of Firmicutes/Bacteroidota and decreased PC (16:1/20:5) and taurochenodeoxycholic acid levels. LAB promoted the expression of genes related to the intestinal bile acid cycle (fxr, hmgcr, rxr, shp and hnf4α) and inhibited the expression of pparβ and g6pase (p < 0.05). LAB reduced the expression of genes related to transported cholesterol (lxr and ldlr) (p < 0.05) in the liver. In conclusion, LAB addition could regulate the gut microbiota disorders caused by high starch levels, promote cholesterol metabolism, produce bile acids, and reduce lipid deposition. Full article

The Haor region in northeastern Bangladesh, characterized by seasonal wetlands and a heavy reliance on fisheries, faces significant challenges due to climate change. Erratic rainfall, prolonged flooding, and ecosystem degradation threaten traditional fishing practices and community livelihoods. This study investigates the potential of climate-resilient cage aquaculture as a sustainable, alternative income-generating solution for vulnerable Haor communities. An 80-day experiment was conducted in five villages of Sunamganj district, Sylhet division, Bangladesh, where tilapia (Oreochromis niloticus) fry were reared in climate-resilient floating cages at five stocking densities: T1 (800 fry/m³), T2 (900 fry/m³), T3 (1000 fry/m³), T4 (1100 fry/m³), and T5 (1200 fry/m³). Key environmental parameters, including temperature (28.12–29.55 °C), dissolved oxygen (4.61–6.55 mg/L), pH (7.53–7.72), and ammonia (0.05–0.76 mg/L), remained within optimal ranges across treatments. Growth performance, survival rate, and economic feasibility were evaluated with T5 yielding the highest gross production (51.77 ± 4.80 kg/m³) and net benefits (7500 ± 500 BDT/m³), achieving a benefit–cost ratio of 1:2.86. The survey findings revealed that a majority of fishers (82%) identified tilapia cage culture as a promising alternative livelihood, yet financial constraints and limited access to credit hinder adoption. Despite these socioeconomic challenges, our findings suggest that tilapia cage culture offers a viable income-generating solution, particularly during flood periods. The study highlights floating cage aquaculture as a climate-resilient strategy to mitigate climate impacts, enhance food security, and improve economic resilience in flood-prone and ecologically sensitive regions. Full article

Ecological floating beds are effective in mitigating lake eutrophication. To examine the effects of their in situ remediation processes on the food sources and trophic structures of consumers, particularly fish, this study used stable isotope techniques to compare cage enclosures, net enclosures, and natural lake area in Meiliang Bay, Lake Taihu. The results revealed that among basic carbon sources, only the δ¹³C values of phytoplankton and POM differed significantly, while most consumers showed no significant differences in carbon and nitrogen stable isotope characteristics across the three remediation areas. In cage enclosures, the food chain transitioned from being grazing-based, dominated by phytoplankton, to detritus-based, primarily relying on SOM. In contrast, net enclosures enhanced the utilization of phytoplankton. The trophic levels of most consumers in cage enclosures were significantly lower than those in net enclosures and the natural lake area. Trophic niche indices indicated that cage enclosures exhibited the highest trophic diversity and the lowest trophic redundancy. The in situ remediation using ecological floating beds altered the food resource conditions within the remediation areas due to differences in the degree of enclosure provided by the floating beds and interception facilities. These changes have consequently reshaped the internal trophic structure through trophic cascade effects. Full article

This study evaluates the hydrodynamic performance of a movable fish cage equipped with a spread mooring system in offshore condition. It investigates the global behavior and safety of a mooring system under environmental influences such as waves, currents, and biofouling. A numerical model was developed using the Cummins equation and a lumped-mass line model to capture the coupling effects between the floating structure and mooring lines. The steel frame was modeled using Morison members, whereas fishing nets were represented by a screen model incorporating drag forces. Parametric studies were performed to assess the effects of varying mooring line lengths, current speeds, and biofouling on cage behavior. Evidently, heavier chains reduced excursions but increased tension, whereas high current speeds increased the line tension (owing to increased drift) and mooring line stiffness by up to 66%. Biofouling increased the maximum excursion by 6% and line tension by up to 17%. Safety evaluations based on the American Bureau of Shipping rules examined intact and damaged conditions, comparing estimated line tensions with allowable values. The findings confirm that the mooring system ensures reliable station-keeping performance even under challenging conditions, validating its suitability for offshore deployment and ensuring the safety and stability of floating fish cage systems. Full article

Malondialdehyde (MDA) is a reactive carbonyl compound produced through lipid peroxidation during feed storage, which poses a significant threat to fish health. This study aimed to evaluate the effects of dietary MDA on the growth rate, gastrointestinal health, and muscle quality of striped catfish (Pangasianodon hypophthalmus). A basal diet (M0) containing 34% crude protein and 10.5% crude lipid was formulated. Each group was sprayed with malondialdehyde solution (0, 5, 10, 20, 40, and 80 mg/kg, on dietary crude lipid basis; 0, 0.53, 1.07, 2.13, 4.26, and 8.52 mg/kg, on dietary basis) before feeding, respectively. Each diet was randomly assigned to triplicates of 30 striped catfish (initial weight 31.38 g) per net cage. After 8 weeks, dietary inclusion of MDA regardless of level significantly depressed the growth rate and feed utilization. The extent of structural damage to the gastrointestinal tract increased progressively with increasing dietary MDA levels. The extent of damage to the intestinal biological barrier (intestinal microbial structure), chemical barrier (trypsin, lipase, amylase, and maltase activity), physical barrier (zonula occludent-2, occludin, claudin 7α, and claudin 12 relative expression), and immune barrier (contents of complement 4, complement 3, immunoglobulin M, and lysozyme activity) was dose-related to dietary MDA. Moreover, a linear decline in the activities of intestinal antioxidant enzymes (catalas, superoxide dismutase, et al.) and anti-inflammatory factor (transforming growth factor beta1, interleukin 10) relative expression was noted alongside an increase in dietary MDA content. In contrast, the relative expression levels of intestinal inflammatory factor (interleukin 8, transcription factor p65, tumor necrosis factor alpha) relative expression displayed an opposing trend. Additionally, dietary MDA exerted a linear influence on muscle color and texture characteristics. In conclusion, high doses of MDA (5–80 mg/kg) reduced the growth performance of striped catfish, attributed to linear damage to the gastrointestinal tract, a linear decrease in antioxidant function, and the occurrence of an inflammatory response. High doses of MDA (>40 mg/kg) were observed to significantly increase dorsal muscle b-value and induce muscle yellowing. Full article

This study explores the hydrodynamic behaviour of a fish cage in a steady current by employing a fluid–structure interaction model with one-way coupling between a fluid solver and a structural model. The fluid field around the fish cage is predicted using a computational fluid dynamics solver, while the stress and deformation of the netting are calculated using finite element structural algorithm with solid elements reflecting their real geometry. The fluid velocity and hydrodynamic pressure are calculated and mapped to the structural analysis model. The fluid–structure interaction model is validated by comparing drag force results with published experimental data at different current conditions. Instead of modelling the netting of the fish cage as porous media or using lumped mass methods, the complete structural model is built in detail. The analysis of the fluid field around the nets shows that the change in the current condition has a limited impact on the flow behaviour, but the increase in the current velocity significantly enhances the magnitude of the drag force. This study reveals a reduction in flow within and downstream of the net, consistent with prior experimental findings and established research. Mechanical analysis shows that knotted nets have better performance than knotless ones, and although fluid pressure causes some structural deformation, it remains within safe limits, preventing material failure. Full article

Due to the limitations of farming space, fish cage aquaculture is gradually expanding into offshore deep-sea areas, where the environmental conditions surrounding deep-sea fish cages are more complex and harsher compared to those in shallower offshore locations. Conventional multi-point moored gravity flexible fish cages are prone to damage in the more hostile environments of the deep sea. In this paper, we present a design for a single-point mooring vessel-shaped fish cage that can quickly adjust its bow direction when subjected to waves from various angles. This design ensures that the floating frame consistently responds effectively to wave impacts, thereby reducing the wave forces experienced. The dynamic response of the floating frame and the mooring forces were simulated by coupling the Smoothed Particle Hydrodynamics method with the Moordyn numerical model for mooring analysis. The three degrees of freedom (heave, surge, and pitch) and the mooring forces of a scaled-down vessel-type ship cage model under wave conditions were investigated both numerically and experimentally. The results indicate that the error between the simulation data and the experimental results is maintained within 6%. Building on this foundation, the motion response and mooring force of a full-sized ship-shaped net box under wave conditions off the southeast coast of China were simulated. This study examined the effects of varying mooring lengths and buoy configurations on the motion response and mooring force of the fish cage. Finally, we constructed the fish cage and tested it under the influence of a typhoon. The results demonstrate that the fish cage could operate stably without structural damage, such as mooring failure or floating frame breakage, despite the significant deformation of the floating frame. Full article

Coastal aquaculture and local fisheries interact in shared marine environments, influencing each other synergistically and/or antagonistically. Salmon farming, notably with open-net sea cages along the Norwegian coast, attracts wild fish due to increased food availability from uneaten feed, but it also exposes wild fish to farm emissions like waste and toxic chemicals (de-lice treatments, antifouling and medical agents). The attraction behaviour of wild fish can impact fatty acid composition in fish tissues, influenced by the high terrestrial fat content in salmon aquafeed. We study how the Atlantic cod, aggregating around salmon farms in a subarctic fjord in Northern Norway, can be affected, potentially altering their natural diet and fatty acid profiles. Our study compares the muscle-tissue fatty acid compositions of cod caught near aquaculture facilities (impact) versus fish caught in neighbouring fjords (control), and we hypothesise decreased omega-3 fatty acids near farms. The analysis revealed no significant differences in the fatty acid concentrations or categories between the impacted and control fish, challenging our initial expectations. However, differences were found for C18:1(n9)t (elaidic acid), with a higher value in the impacted fish. These findings suggest that salmon farming’s influence on cod’s fatty acid profiles in the flesh (i.e., relevant for the nutritional quality of the fillets that consumers eat) may be limited or minimal despite their aggregative behaviours around farms. The threshold levels of salmon feed consumed by wild cod before it affects the quality and survival of, e.g., sperm or other life stages, are not known and require new investigations. This study underscores the complexity of interactions between aquaculture and wild fisheries, impacting both ecological dynamics and consumer perspectives on seafood quality and health benefits. Full article

The present review focuses on the theoretical model developments made in floating flexible net fish cages and the floating bodies application to offshore aquaculture. A brief discussion of the essential mathematical equations related to various theoretical models of flexible net cages in the frequency domain is presented. The single and array of floating or submerged flexible net cages connected with or without mooring lines are discussed. Further, as the combined effect of the hydroelastic behaviour of floaters and the flexible behaviour of fish cages are necessary to assess their efficiency and survivability from structural damages, the issues and the knowledge gap between the recent and future models are also discussed. In conclusion, the practical suggestions concerning advancements in future research and directions within floating flexible net cages and the hydroelastic response of elastic floaters are highlighted. Full article

Deep-sea aquaculture can alleviate the spatial and environmental pressure of near-shore aquaculture and produce higher quality aquatic products, which is the main development direction of global aquaculture. The coastline of China is relatively flat, with aquaculture operations typically operating in sea areas with water depths of approximately 30–50 m. However, with frequent typhoons and poor sea conditions, the design of mooring system has always been a difficult problem. This paper investigated the multiple cages, considering two layouts of 1 × 4 and 2 × 2, and proposed three different mooring system design schemes. The mooring line tension of the mooring systems under the self-storage condition was compared, and it was observed whether the mooring line accumulation and the contact between the mooring line and the steel structure occurred on the leeward side. Additionally, flexible net models were compared with rigid net models to evaluate the impact of net deformation on cage movement and mooring line tension. Finally, based on the optimal mooring design, the dynamic response of the mooring system under irregular wave conditions was analyzed and studied, providing important reference for the safety and economic design of the mooring system of multiple fish cages. Full article

In mariculture facilities, bacterial infections pose significant production challenges, with potentially catastrophic impacts on fish species. Bacterial co-infections are a widespread phenomenon in the natural marine environment, although their impact on aquatic organisms remains poorly investigated. This study aimed to detail the pathological findings associated with a natural bacterial co-infection caused by three different pathogens, namely Photobacterium damselae subsp. piscicida, Tenacibaculum maritimum and Vibrio sp., as the cause of mass mortality in European sea bass. The fish had been reared in open-net cages in Sicily and later transferred for experimental research purposes to a user establishment after immunization with an inactivated vaccine. Macroscopic, cytological and histopathological examinations were performed on 109 animals, and bacterial species were identified by the 16S rRNA gene. Overall, ulcerative skin lesions, necrotizing myositis and tail rot with occasional tail loss were associated with tenacibaculosis and vibriosis, while P. damselae subsp. piscicida mainly caused granulomatous inflammation in the spleen and head kidney. Finally, an injection site reaction due to the oil-adjuvanted vaccine administered intraperitoneally was observed in the abdominal fat. Understanding the impact of bacterial pathogens is essential to manage the health and welfare of farmed fish, and the importance of a good health monitoring program cannot be overstated to avoid outbreaks and the possible emergence of new pathogens due to the intensification of the production systems, antibiotic resistance and climate changes. The study would also highlight the importance of the quarantine period when animals supplied for research come from aquaculture farms and how the main goal in the near future should be to better define the procedures to provide completely pathogen-free animals. Full article

This paper analyzes the factors influencing households’ resilience capacities to shocks within Kenya’s fisheries and aquaculture sectors and draws from primary data collected from 419 fish-dependent households across Kisumu, Busia, Mombasa, and Kilifi counties. The sample represents a total of 48,000 fishing households. The study adopted a quasi-longitudinal design and computed the household resilience capacity index (RCI) using the resilience index measurement and analysis (RIMA-II) model. The results indicate that male-headed households’ mean household RCI scores (mean = 45.07 ± 10.43) were statistically significant to that of female-headed households (mean = 38.15 ± 9.25), suggesting that female-headed households are associated with lower resilience capacities than male-headed households. Moreover, the study identifies differences in resilience levels across various occupations within the sector. For instance, RCI scores among fish traders (mean = 40.71 ± 9.97), a function performed mainly by women, statistically differed (p < 0.005) from male-dominated cage farming (mean = 48.60 ± 10.47), whereas RCI scores at the production level for fisher folks (mean = 44.89 ± 10.09) and pond farmers (mean = 44.04 ± 12.07) showed no statistical difference (0 > 0.05. Additionally, households with more income sources tend to have higher resilience capacities. Seasonality in fishing cycles limited households’ ability to recover from climate-induced shocks; the more months without fishing activity, the less the odds of recovery from shocks (OR = 0.532, 95% CI [0.163, 0.908], p = 0.022). Furthermore, households that lacked guaranteed market access and inputs during COVID-19 were less likely to recover during and after the shocks (OR = 0.401, 95% CI [0.161, 0.999], p = 0.05). Households organized in cooperatives with better access to credit showed a higher chance of recovery. The study recommends (a) adopting gender-sensitive approaches in fisheries and aquaculture interventions to empower women in trade, (b) strengthening policies to enhance access and adoption of climate-smart technologies such as cage fish farming, (c) promoting livelihood diversification to sustain households’ income during fishing off-seasons, and (d) enhancing market linkages in the fish value chain through coordinated producer organizations. Further research should explore the possibilities of introducing index-based weather insurance and other tested suitable safety nets for the fisheries and aquaculture sector. Full article