The increasing interest in sustainable and cheaper protein resources in aquaculture production has generated a growing interest in alternative feed ingredients. Aquaculture is one of the world’s most rapidly expanding and largest food production industries. Notably, the inclusion of fishmeal in aqua feed has been gradually replaced with alternative sources of protein inputs due to the high cost of production, limited availability of raw materials, and environmental pressures. The black soldier fly larvae (Hermetia illucens; BSFL) meal is attracting greater attention as a feed ingredient for aqua feeds, as it contains high protein content similar to fishmeal (FM). H. illucens larvae rearing can also be realized with different biodegradable substrates, which are converted into high-value biomass. BSFL-based diets have been evaluated in several finfish and crustacean species have assessed final body weight (FBW), specific growth rate (SGR), feed conversion ratio (FCR), feed intake (FI), feed efficiency (FE), survival rate (SR), and apparent digestibility coefficients (ADC), using fishmeal-based diets as the reference. Although previous reviews have examined insect meals and black soldier fly larvae, integrated evidence remains fragmented regarding the practical use, sustainable production, benefits, and limitations of BSFL meal in aquafeeds. Therefore, this review aims to evaluate the practical use of BSFL meal as a protein source in aquaculture, with particular emphasis on sustainable production practices, nutritional benefits, and the challenges associated with its wider application in the aquafeed industry as well as its benefits.
Balancing dietary n−3 long-chain polyunsaturated fatty acids (LC-PUFAs) is essential for optimizing growth and disease resilience in Atlantic salmon and will become an increasing challenge when implementing novel sources of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), such as genetically modified (GM) oils and microalgae oils. To study this, Atlantic salmon (Salmo salar L.) fry (initial weight 0.15 g) were pre-fed diets differing in EPA/DHA ratios (0.2 E/D, 0.9 E/D, and 2.2 E/D) while maintaining constant total EPA+DHA for 4 weeks. Following this, and while kept on the same dietary treatments, the fry were challenged with wild-type or attenuated salmonid alphavirus (SAV-WT and SAV-Att, respectively). The duration of the disease challenge was up to 28 days, with a final fish weight of approximately 1.1 g at the end of the trial. There was a clear decrease in fatty acid storage during SAV-WT infection, which was not observed during SAV-Att infection. We demonstrate a preferential decrease in monounsaturated fatty acids during SAV-WT infection, preserving the n−3 LC-PUFA content in the tissues. Increasing the dietary EPA/DHA ratio significantly reduced growth performance, indicating that the dietary balance of EPA to DHA influences growth during the start feeding of salmon fry. Following infection, dietary effects were outcome-dependent. Fish fed the low EPA/DHA diet (0.2 E/D) showed overall higher viral loads, but improved histopathology at the end of the trial. In contrast, fish fed the high EPA/DHA diet (2.2 E/D) exhibited signs of improved histopathology at the end of the trial, yet experienced the highest (non-significant) mortality after SAV-WT challenge. Fish fed the balanced diet (0.9 E/D) showed poorer histopathological scores at the end of the trial, but did not display elevated mortality. These findings demonstrate that dietary EPA/DHA ratios differentially modulate growth and disease outcome, exerting distinct and sometimes opposing effects on viral load, tissue inflammation, and survival. The results highlight the complexity of optimizing n−3 LC-PUFA balance to support both performance and antiviral resilience in Atlantic salmon.
Artificial intelligence (AI) is transforming aquaculture by enabling precision management, environmental monitoring, and sustainability-oriented decision support. This review advances the discourse by integrating human-centered AI, ethical governance, and sustainability frameworks into a cohesive analysis of digital transformation in aquaculture. Based on a structured synthesis of 220 peer-reviewed publications from multidisciplinary literature published between 2015 and 2025, the study employs a qualitative review methodology to identify emerging trends, challenges, and research directions in AI-enabled aquaculture systems. The analysis reveals three emergent research pillars: (1) human-centered and explainable AI (XAI) systems that enhance decision transparency and farmer engagement; (2) ethical and governance frameworks addressing data ownership, algorithmic bias, and accountability; and (3) technological applications and innovation pathways linking machine learning, computer vision, and Internet of Things (IoT) platforms to operational sustainability. Findings indicate that while AI-driven tools have improved biomass estimation, behavior tracking, disease detection, and feed optimization, adoption remains constrained by affordability, digital literacy, infrastructure limitations, and data interoperability barriers. Ethical concerns related to transparency, cybersecurity, privacy, and equitable access to data further underscore the need for adaptive governance mechanisms. Aligning these technological and ethical dimensions with the Food and Agriculture Organization (FAO) Blue Transformation agenda and the Organization for Economic Co-operation and Development (OECD) AI Principles highlights a pathway toward inclusive, responsible, and context-sensitive AI ecosystems in aquaculture. By bridging the technical and human dimensions of AI deployment, this synthesis proposes a conceptual framework for responsible digital aquaculture in which innovation is embedded within social, ethical, and policy-responsive systems. The review concludes that the long-term sustainability of AI in aquaculture will depend not only on technological advancement but also on the co-evolution of governance structures, human capacity, and environmental stewardship.
Rising sea surface temperatures and salmon lice (Lepeophtheirus salmonis) are interacting environmental and health pressures that can affect growth, condition, survival, treatment needs, and production outcomes in farmed Atlantic salmon (Salmo salar). This systematic review evaluated growth models used in farmed salmonid aquaculture to identify frameworks suitable for quantifying the combined effects of temperature and salmon lice burden during the post-smolt to adult production phase. We initially screened salmonid growth-model studies broadly, including farmed and wild systems, but excluded wild salmonid models from the final synthesis because their ecological objectives, feeding assumptions, data structures, and outputs were poorly aligned with farm-level aquaculture scenario modeling. The retained farmed-salmonid models included empirical index and phenomenological models, bioenergetic models, and nutritional models. Empirical approaches such as Thermal-unit Growth Coefficient and logistic growth models require relatively few inputs and are practical for farm-level scenario analysis, but their transferability depends on local calibration and validation. Mechanistic bioenergetic and nutritional models provide greater biological realism and can represent stressor effects more explicitly, but require substantially more parameters and higher-resolution data. Explicit coupling of salmon growth with salmon-lice dynamics remains rare. For scenario-oriented assessment of warming and salmon lice in Atlantic salmon aquaculture, the most practical near-term framework is a validated, temperature-driven farmed-salmon growth model that is locally calibrated with production and environmental data and coupled modularly to a lice-dynamics or infestation-pressure component.
In response to growing interest in bio-conservation as a means of limiting the use of chemical preservatives, this study optimized the formulation of a fish sausage using a bacteriocin derived from Lactococcus lactis F01. The optimized “BIO Opti” formulation was then compared to a non-optimized organic sausage, a formulation containing sodium benzoate “CHE”, and a control. The optimization, conducted using a centered composite design, determined that the optimal conditions are 327.015 µg of bacteriocin per 50 g of product and 5.02% NaCl. Under these conditions, “BIO Opti” exhibits a significantly lower microbial load of 1.56 ± 0.84 log10 CFU/g and a moisture content of 61.55 ± 0.09%, compared with 1.75 ± 0.72 log10 CFU/g and 62.55 ± 0.31% for BIO (p< 0.05). Furthermore, after 28 days of storage at 8 °C, the sensory quality of “BIO Opti” remains equivalent to that of “CHE” (p > 0.05). Taken together, the results indicate that optimization extends shelf life and positions bacteriocin as a credible natural alternative to synthetic preservatives.
IntroductionFunctional feed additives are increasingly incorporated into aquaculture diets to improve nutrient utilization and production efficiency. However, their effects on growth, morphometric development, and stress resilience in shrimp remain incompletely understood.MethodsJuvenile whiteleg shrimp (Penaeus vannamei) were fed either a control diet or a diet supplemented with choline chloride, L-carnitine, glycerol monolaurate, and lysophospholipids for 42 days, using four replicate tanks per treatment. Growth performance, feed conversion ratio, protein efficiency ratio, growth uniformity, morphometric traits, length–weight relationships, growth dynamics, and responses to an acute low-salinity and temperature-shock challenge were evaluated.ResultsSupplementation significantly increased protein efficiency ratio compared with the control treatment (0.0237 ± 0.0008 vs. 0.0221 ± 0.0006; p = 0.019). Survival, final biomass, final body weight, feed conversion ratio, growth uniformity, final body length, modified condition factor, allometric coefficient, and stress-challenge survival were not significantly affected. Length–weight relationships indicated approximately isometric growth in both treatments. Multivariate analyses consistently identified protein efficiency ratio as the principal variable associated with supplementation.DiscussionThe additive blend improved apparent protein-use efficiency without substantially altering growth performance, morphometric development, growth dynamics, or stress tolerance. Nutrient-use efficiency may therefore be a more sensitive indicator of dietary additive responses than conventional growth metrics. However, the limited number of tank replicates and the combined osmotic and thermal stress challenge should be considered when interpreting the findings.
Quantitative information on the fate of macronutrients derived from fish effluents, their concentrations in culture water, and their assimilation by plants across hydroponic and aquaponic systems remains limited. To bridge this gap, this study examined the growth response of lettuce (Lactuca sativa) and the dynamics of key nutrients, nitrogen (N), phosphorus (P2O5), potassium (K2O), calcium (Ca), and magnesium (Mg), in water and plant tissues under three production strategies: coupled aquaponics (T1), conventional hydroponics (T2), and nutrient supplemented decoupled aquaponics (T3) integrated with African catfish (Clarias gariepinus). Over a forty-day cultivation period, lettuce grown in conventional hydroponics achieved higher biomass values than plants in either of the aquaponic systems. T1 produced intermediate growth, while T3 showed the lowest biomass. Morphological observations revealed greater shoot development in T2, moderate shoot formation in T1, and comparatively higher root biomass in T3, indicating differences in nutrient uptake and allocation among treatments. Although measured macronutrient concentrations suggested sufficient availability, plant productivity was not directly proportional to total nutrient levels, highlighting the role of nutrient assimilation efficiency. Economic evaluation indicated that although T2 achieved the highest vegetable yield, T1 generated the highest gross income due to the combined fish and crop sales, while T3 achieved the highest return on investment and the shortest payback period. Overall, this study provides quantitative insight into nutrient dynamics, plant uptake, and economic performance across hydroponic and aquaponic systems. These findings contribute to a better understanding of resource use efficiency and support the optimization of nutrient management and system design for sustainable integrated aquaculture production.
With the development of cost-effective high-throughput shellfish genotyping tools, the application of genomic selection in oyster breeding is quickly becoming a reality. A critical, but laborious step in this process is the non-lethal DNA sampling of candidate broodstock for genotyping. Benignly sampling oysters is complex, requiring anesthesia to induce incomplete adductor muscle paralysis, followed by DNA sampling via biopsy, hemolymph or tissue extraction which can take significant time per individual and physically damage valuable breeding candidates. In this study genotype concordance of multiple non-lethal, and less injurious DNA sampling methods in Eastern (Crassostrea virginica) and Pacific (C. gigas), oysters were evaluated. Genotypes obtained via swabbing, eDNA collection, and mantle tissue clipping were compared to a reference adductor muscle-derived genotype, which was obtained lethally. Eastern oyster (Crassostrea virginica) samples were evaluated on a 66K Single Nucleotide Polymorphism (SNP) array and Pacific oyster (Crassostrea gigas) samples were evaluated using PCR-based genotyping-by-sequencing. Retention of glue-on tags and oyster survival were also evaluated for 27 days in Pacific oysters in the field, after non-lethal sampling. Overall SNP genotype concordance rates were high in both oyster species (> 99% in samples passing quality control) with DNA quality having little impact on genotype concordance rate. Using a microhaplotype sequence workflow in two Pacific oyster genotyping panels resulted in a higher non-concordance rate (approx. 4%), however the missing (non-called) allele was found in raw sequencing data in the vast majority of cases, suggesting that rudimentary genotype calling parameters are likely driving the higher error rate. This is not surprising given the nascent implementation of microhaplotypes in aquaculture research and ongoing panel development. Post-swab survival was high, and all animals retained physical tags for subsequent identification. Overall, non-lethal swab DNA collection provided high quality genotype data similar to mantle or adductor tissue-derived genotype data; swab sampling was also faster and easier to implement and may be less stressful. The use of non-lethal swabbing for genotyping will be an important step for implementing genomic selection and using advanced genetic tools in research supporting oyster restoration and production aquaculture.
Aquaculture sludge from recirculating systems contains a substantial share of feed-derived nutrients, yet it is typically discarded despite nutrient limitations in aquaponics. In this study, tilapia sludge from a commercial RAS was treated by sealed storage, gradual acidification (pH 5), ultrasonication, aerobic mineralization, anaerobic digestion (AD), and two AD-based sequential approaches (AD pH, AD US pH). Total and dissolved fractions were quantified to assess nutrient distribution between solid-bound and dissolved pools, and treatment-dependent mineralization performance was calculated. In untreated sludge, >75–90% of nitrogen, phosphorus, calcium, magnesium, and most trace elements were associated with the solid phase, whereas potassium was largely dissolved. AD variants achieved the highest nitrogen mineralization (up to ~47%) with ammonium-dominated supernatants (≈460–480 mg NH4–N L−¹), while aerobic mineralization promoted nitrification and yielded nitrate-dominant nitrogen (≈257 mg NO3–N L−¹). Phosphorus mobilization was primarily pH-driven, peaking under acidification (≈165 mg PO4–P L−¹) and increasing after post-acidification of AD supernatants. Micronutrient responses were element-specific; manganese increased markedly under acidified and unaerated conditions, whereas dissolved iron remained low across treatments. Compared to ideal hydroponic nutrient media, most supernatants required dilution due to elevated ammonium, and iron supplementation remained necessary. Most potentially toxic elements remained in the low µg L−¹ range and below irrigation and reported algal toxicity thresholds. Selected sludge-derived nutrient media were suitable for Arthrospira platensis cultivation to support circular nutrient reuse. In growth trials, the non-acidified AD supernatant (AD S) supported the strongest biomass and pigment performance among sludge-derived media, reaching up to 1.32 g DW L−¹, with a chlorophyll a content of 21.7 mg L−¹ and a C-phycocyanin content of 24.6 mg g DW−¹. Overall, sludge mineralization shifted nutrients from bound to dissolved pools and generated distinct nutrient profiles, highlighting the importance of aligning treatment strategy with the intended downstream application in circular RAS–aquaponic systems.
The growing global demand for food, coupled with climate change, underscores the need for sustainable strategies to enhance food security and reduce waste. Aquaponics offers a promising solution by integrating aquaculture and horticulture within a single system, thereby improving productivity, diversification, and environmental sustainability. Despite growing scientific and governmental interest, the commercialization of aquaponics remains challenging. This systematic review identifies 53 key challenges to scaling aquaponics, grouped into five categories: 1) infrastructure and mechanics, 2) system knowledge, 3) market dynamics and consumer preferences, 4) culture and norms, and 5) legal frameworks and policies. The largest number of challenges were identified in system knowledge (16 issues) and market dynamics and consumer preferences (20 critical topics). Technological advancements, including Artificial Intelligence (AI), Internet of Things (IoT), Machine Learning (ML), deep learning, sensor technology, monitoring systems, computer vision, digital detection, and data processing, offer potential solutions that enable automatic management and control of the system, continuous monitoring of fish and plants, analysis of large datasets, decision-making, and optimization of production and inputs. These solutions provide answers and a way forward across these challenging areas. The document critically examines the primary factors influencing the scalability of aquaponics, emphasizing the role of technology in enhancing efficiency and strengthening key production and management processes. While progress has been made, significant opportunities remain to use technology to optimize aquaponic systems, particularly in microbiology, pest control, and monitoring, offering a window for scalable technology and applications. The overarching aim is to address existing barriers to sustainable food production.
IntroductionFish feed management plays a central role in aquaculture productivity, but it is rarely analysed through a gender lens. This study examines how women and men differ in their use and sourcing of fish feed ingredients in smallholder aquaculture systems in Western Kenya. Drawing on feminist economics, it explores how everyday roles, access to resources, and mobility shape feed practices.MethodsThe analysis uses survey data from 213 fish farmers, including 112 women and 101 men, across six counties in Western Kenya. A binary logit model was used to assess factors associated with the use of selected feed ingredients, including poultry waste, plant leaves, and maize powder, while controlling for socio economic characteristics, mobile phone ownership, farming system, and county.ResultsClear gendered patterns emerged. Women reported higher use of maize powder, poultry waste, cassava waste, chicken manure, feathers, and other household organic by products. Men were more likely to use plant leaves, kitchen leftovers, rice bran, and a broader mix of other inputs, often accessed through male networks. Differences were also evident across farming systems. Semi intensive earthen ponds relied on more purchased and diverse inputs, intensive systems focused on energy dense staples such as maize and cassava, and extensive systems drew heavily on locally available organic materials. Men were more commonly involved in applying plant leaves and chicken manure in these systems. Regression results show that gender remains significantly associated with the use of poultry waste and plant leaves, but not maize powder, suggesting that some differences are not fully explained by location or production system.DiscussionThese findings point to feed practices as embedded in gendered divisions of labour and resource access rather than neutral technical choices. Women’s roles in cooking, managing household waste, and caring for backyard poultry provide regular access to organic by products that can be used as feed. Men’s greater control over land, cash, and mobility supports access to field based and market sourced inputs. This has practical implications for extension and advisory services, which need to recognise these differences rather than assume uniform practices. It also highlights the importance of monitoring how changes in feed practices affect women’s time use, decision making, and control over income.
The utilization of fish-derived collagen has become a promising sustainable approach to improve resource efficiency in the seafood processing industry while also revealing high-value applications in the functional food sector. Fish processing produces significant byproducts, including skins, scales, bones, and swim bladders, which are abundant in collagen but frequently remain unused or decomposed, exacerbating environmental issues. Collagen extracted from fish waste exhibits remarkable biocompatibility, biodegradability, substantial water retention capacity, and an advantageous amino acid profile, making it appropriate for transformation into gelatin, hydrolysates, and bioactive peptides with various functionalities. Recent advancements in extraction and purification methodologies such as enzymatic hydrolysis, ultrasound-assisted extraction, and membrane filtration have increased the yield, structural integrity, and bioactivity of collagen derivatives. Collagen-derived components exhibit significant antioxidant, antihypertensive, antibacterial, and immunomodulatory characteristics, justifying their inclusion in functional foods, nutraceutical formulations, edible films, microencapsulated delivery methods, and protein-fortified products. Furthermore, collagen derived from fish waste presents benefits compared with that derived from mammalian sources, including less immunogenicity, a lack of religious restrictions, and a safer profile for disease transmission. Despite its potential, commercialization is affected by hurdles such as unpredictability in raw material quality, standardization of extraction techniques, scale-up efficiency, regulatory compliance, and customer acceptance. This review rigorously assesses the valorization paths of fish waste collagen, including its structural and biological characteristics, extraction methodologies, technical applications in functional food product development, nutraceuticals and prospective research avenues. Collagen extracted from fish waste is a sustainable bioresource that may convert industrial waste into nutritionally useful functional components, supporting global sustainability and health-oriented food innovation.
With rising global seafood demand, aquaculture has progressively expanded offshore due to spatial constraints and ecological pressures in coastal zones. Offshore aquaculture of extractive species, such as bivalves and seaweeds, offers a promising pathway to enhance food security while mitigating environmental impacts. However, the sustainability aspect of such aquaculture operations depends on ecologically conducted site selection. This systematic review examines the key criteria and methodologies used for site selection of extractive, low-trophic species aquaculture in offshore environments, emphasizing ecological carrying capacity as a critical determinant of sustainability. Following Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, peer-reviewed literature from Scopus and Web of Science (2000–2025) was systematically searched using predefined keywords related to offshore aquaculture and site selection. Studies were screened and analyzed for species focus, geographic region, methodological approach, environmental and socio-economic criteria, and incorporation of ecological carrying capacity assessments. Results reveal that most site selection frameworks rely heavily on Geographic Information System based Multi Criteria Evaluation approaches, with limited integration of offshore-specific ecological thresholds. Dynamic Energy Budget and Farm Aquaculture Resource Management models have been successfully applied to predict growth and potential environmental impacts, but empirical data from offshore systems remain scarce. We highlight key knowledge gaps and recommend integrating mechanistic models, ecosystem-based indicators, and adaptive thresholds into site selection frameworks. The review concludes that sustainable offshore aquaculture requires a paradigm shift from static suitability mapping toward dynamic, ecosystem-informed site allocation that respects ecological limits and supports multi-use marine planning.
Dietary nucleotides are functional feed additives that may improve fish health and physiological performance, although their efficacy can vary according to the nucleotide source. This study evaluated the effects of dietary supplementation with yeast (Saccharomyces cerevisiae) RNA (YR) and yeast-derived free nucleotides (YFN) on growth performance, immune response, digestive enzyme activity, and nutrient digestibility in Nile tilapia (Oreochromis niloticus). Juveniles (100 ± 5 g) were assigned to three dietary treatments (control, YR, and YFN), with four replicates of 15 fish per tank, and fed the experimental diets for 60 days before being challenged with lipopolysaccharide (LPS). Growth performance and survival were not affected by dietary treatments (p > 0.05). Whole-body composition was also largely unchanged; however, crude protein content was higher in fish fed YR compared to YFN (p < 0.05), while lipid and ash contents remained unaffected. Hematological and immune parameters were modulated by nucleotide supplementation. YFN-fed fish showed increased hematocrit and total serum protein after the LPS challenge, while both YR and YFN groups exhibited reduced red blood cell counts (p < 0.05). Additionally, YFN increased serum lysozyme activity and total immunoglobulin levels following the challenge, and all treatments showed enhanced mucus antiprotease activity. Digestive enzyme activity was influenced by dietary treatments, with YR increasing amylase activity in all intestinal sections (p < 0.05), while protease activity varied according to intestinal region and nucleotide source. However, apparent digestibility coefficients of dry matter, crude protein, and phosphorus were not affected (p > 0.05). In vitro, YFN increased superoxide anion production in head kidney leukocytes after LPS stimulation. These findings indicate that dietary nucleotide supplementation modulates physiological responses without affecting growth performance or nutrient digestibility, with YR favoring protein deposition and YFN enhancing immune responses.
Despite growing developments in aquaculture technologies, there is still a lack of clear understanding of the aspects of feeding strategies, nutrient dynamics, and resource-use efficiency between Biofloc Technology (BFT) and Recirculating Aquaculture Systems (RAS). This gap in knowledge limits the utilization of these systems for its full capacity for meeting the rising global demand for fish protein. This review aims to critically analyze and integrate existing knowledge on BFT and RAS, focusing on their roles in nutrient utilization, feeding strategies, water quality management, and overall fish growth performance. The adoption of advanced technologies, such as Biofloc Technology (BFT) and Recirculating Aquaculture System (RAS), in the fisheries sector can significantly improve fish production, thereby compensating for the protein needs of the growing population. The major role of RAS in waste removal and that of BFT in improving nutrient retention would help to accomplish the need for accurate utilization of land and water resources. The feeding strategy in the biofloc system differs from that of semi-intensive culture, where maintaining a proper C/N ratio is necessary. Even though the contribution of biofloc in the daily feeding ratio depends upon cultured fish species, with reported values of 30% for shrimp, 50% for tilapia, and 25% for common carp, it still indicates a favorable effect on growth and survivability. This is primarily due to the superior nutritional profile of biofloc. Biofloc systems are constrained by challenges in maintaining optimal C/N balance and managing excess solids. Meanwhile, in the RAS system, the feeding strategy focuses mainly on achieving energy satiation and maintaining a precise feeding frequency, resulting in reduced feed waste in the tank through the mechanical, chemical, and biological filtration systems. However, RAS involves high capital and operational costs. Therefore, integration of BFT and RAS into a Recirculating Biofloc System (RBS) can offer a synergistic approach that combines efficient waste utilization with advanced filtration, improving system stability, productivity, and can mitigate the risks associated with these two culture systems.
Edwardsiella ictaluri has emerged as a significant pathogen in farmed siluriform species worldwide; however, reports of disease caused by this pathogen in free-living fish are rare. This study aimed to identify the etiological agent responsible for a mortality event in wild streaked prochilod (Prochilodus lineatus) in the São Francisco River basin, state of Minas Gerais, Brazil. Additionally, the genetic profile and antimicrobial resistance of the isolates were evaluated using REP-PCR fingerprinting and disk diffusion assays. Diseased fish were sampled (n = 18) at two distinct points along the river and subjected to bacteriological examination. All obtained isolates were identified as E. ictaluri via qPCR and dnaJ gene sequencing. Pathogenicity was confirmed through experimental infection fulfilling Koch’s postulates, resulting in 100% mortality within 51 hours in the high-dose group and within up to nine days in the low-dose group. Macroscopic and histopathological analyses revealed granulomas in the kidney and liver. Regardless of the sampling point, all selected isolates exhibited the same genetic profile based on phylogenetic and REP-PCR analyses. The isolates were susceptible to florfenicol and oxytetracycline. To our knowledge, this is the first report of a natural outbreak of E. ictaluri in wild streaked prochilod in Brazil.
IntroductionThe sustainable recovery and reuse of nutrients from aquaculture waste represent a promising approach to reducing the environmental impact of fish farming while supporting cost-effective microalgal cultivation.Materials and methodsThis study investigated the potential of aquaculture sedimented sludge as a nutrient source for cultivating Arthrospira platensis. Chemical and thermochemical treatments were applied to enhance the solubilization of essential nutrients, particularly phosphorus.Results and discussionAmong the tested reagents, 1 M HCl and 2 M NaOH resulted in the highest phosphate release, with increasing sludge dosage up to 20 g L-1 further improving solubilization efficiency. Thermochemical treatments combining ultrasound or autoclaving with chemical conditioning significantly enhanced nutrient recovery, with the acid–autoclave (AUA) and autoclaved water (AUW) treatments achieving the highest phosphate concentrations (270.6 and 210.8 mg L-1, respectively). Recovered nutrient extracts were subsequently tested as culture media for A. platensis, with six treatments evaluated (acidic, alkaline, and water-based extracts with ultrasound and autoclaving) compared to a standard synthetic medium (Spirulina SAG). The AUW extract supported robust biomass accumulation, comparable to that in SAG medium, when supplemented with 2 g L-1 KNO3 and 10 g L-1 NaHCO3. Further optimization of nitrogen supplementation (0–2 g L-1 KNO3) identified 1 g L-1 KNO3 as optimal, yielding a biomass of 1.45 g L 1 and a protein content of 559.3 ± 21.6 mg L-1. Phycobiliprotein yields (C-phycocyanin: 25.12 mg g-1; allophycocyanin: 6.25 mg g-1) were comparable to those in synthetic medium. Nutrient analysis revealed substantial reductions in 1 g L-1 KNO3 medium: PO43- (90.90%), NH4+ (99.2%), NO3- (68.2%), and K+ (79.7%) during cultivation, indicating efficient nutrient assimilation by A. platensis. This study demonstrates a novel, sustainable approach to transforming aquaculture sedimented sludge into an effective culture medium for A. platensis, thereby reducing reliance on synthetic nutrients and advancing circular bioresource utilization in aquaculture systems.
The aim of this study was to evaluate the relationships among water quality variables and Secchi disk transparency in semi-intensive Oreochromis niloticus earthen ponds. A total of 38 water samples were taken from 27 O. niloticus culture ponds located in rural villages in Brazil, using a non-probabilistic convenience sampling approach. The main water quality variables analyzed included transparency, chlorophyll-a, total suspended solids (TSS), inorganic solids (IS), and volatile solids (VS). The results demonstrated that Chla (p-value = 0.04), TSS (p-value = 0.002), IS (p-value = 0.02), and VS (p-value = 0.04) had a significantly increasing trend with decreasing pond Secchi disk transparency. These findings indicated that the low water transparency readings were not caused solely by system’s primary production This was confirmed by the high percentage of IS in the TSS (> 60%), reinforcing the idea that solids in the water were composed of mineral particles such as sand, silt, and clay. This behavior could be caused by wind or bioturbation by O. niloticus, which causes sediment from the bottom of the pond to be carried into the water column, reducing water transparency. These findings demonstrated that water transparency was not directly related to pond primary production. Therefore, relying solely on Secchi disk depth, as commonly practiced, may not be sufficient for managing eutrophication in semi-intensive O. niloticus farming through water exchange. These results highlight the importance of accurately interpreting water transparency to support more effective environmental management, reduce potential stressors, and contribute to improved animal welfare in these farming systems.
The use of phytogenic feed additives in aquaculture has gained attention as a sustainable strategy to enhance fish growth and health; however, optimal inclusion levels and mechanistic responses remain insufficiently defined. This study aimed to evaluate the effects of dietary aqueous Cymbopogon citratus (lemongrass) extract on growth performance, feed utilization, morphometric development, biometric indices, and hematological status of red tilapia (Oreochromis spp.). A 60-day feeding trial was conducted using 360 fingerlings randomly assigned to four dietary treatments (0, 10, 20, and 30 g kg-¹), with three replicates per treatment. Growth metrics, feed efficiency, morphometric traits, organ indices, and hematological parameters were analyzed using parametric and non-parametric statistical approaches, complemented by dose–response modeling. Lemongrass supplementation significantly improved growth performance, with higher final weight, weight gain, and specific growth rate (p < 0.05), alongside reduced feed conversion ratio (lowest at ~2.4) and increased biomass. Morphometric traits, including total length and fin development, were significantly enhanced at 20 g kg-¹, while hematological parameters remained stable, indicating physiological safety. Quadratic dose–response modeling identified an optimal inclusion level of ~18–20 g kg-¹, linking enhanced growth performance to improved digestive organ development. Biometric responses further suggested selective increases in gut and visceral mass without adverse effects on liver indices. In conclusion, dietary lemongrass extract optimizes growth and feed efficiency through enhanced digestive capacity and allometric development, without compromising fish health. These findings highlight its potential as a functional phytogenic additive for sustainable and welfare-oriented tilapia aquaculture.
