Search Results (2,262)

Intensive recirculating aquaculture systems are vulnerable to spikes of nitrite, which oxidizes hemoglobin to methemoglobin and compromises oxygen transport. Methylene blue (MB) is a classical antidote for methemoglobinemia, yet its use in fish has been limited to injections or immersion baths that are impractical for large-scale operations. This study assessed whether MB incorporated into a medicated feed could mitigate acute nitrite intoxication in Nile tilapia. Fish received either a control diet or 0.1% MB diet. After five days on the experimental diets, fish were exposed to nitrite for 48 h. Control fish experienced five deaths, whereas no mortality or behavioral distress was observed in MB-treated fish. Hematology indicated significantly lower circulating methemoglobin concentration in the MB group, while the control fish had higher hemoglobin concentration and erythrocyte counts, consistent with compensatory erythropoiesis. Gill histology revealed preserved lamellae with only mild changes in MB-fed fish, whereas control fish displayed lamellar aneurysm, edema, capillary congestion, fusion and epithelial hyperplasia. Therefore, oral MB administration appears to ameliorate the physiological consequences of acute nitrite exposure, offering a scalable intervention for emergency management of nitrite spikes. Future work should define dose–response relationships, evaluate post-exposure rescue, quantify gill lesions and assess MB residues in food fish. Full article

This study investigated the effects of dietary lysophospholipids on growth performance, hepatic lipid metabolism, intestinal health, and dietary lipid levels of largemouth bass. The 56-day experiment included five groups: CON (0% lysophospholipids), LL50 (0.05% lysophospholipids), LP50 (0.05% lysophospholipids—0.5% oil), LP100 (0.1% lysophospholipids—1.0% oil), and LP200 (0.1% lysophospholipids—2.0% oil), with 3 replicates (30 fish/replicate) per group. The results showed that compared with the CON group, dietary supplementation of 0.05% lysophospholipid had no significant effect on the growth performance of largemouth bass, but increased the crude protein content and decreased the crude lipid content in the whole body. An amount of 0.05% lysophospholipid improved hepatic lipid utilization efficiency. Specifically, this supplementation level promoted serum lipid transport (increased serum HDL-C content and decreased triglyceride and LDL-C contents), and enhanced hepatic lipid metabolism by regulating the expression of lipid metabolism-related genes (fas, hsl, and acc) and the levels of lipid metabolites (phosphatidylcholine and fatty acids), thereby reducing hepatic triglyceride content. In addition, 0.05% lysophospholipid improved intestinal health by increasing lipase activity and intestinal villus height, up-regulating the expression of the anti-inflammatory gene (tgf-β1) and tight junction protein genes (claudin-1, claudin-4, and zo-1), and down-regulating the expression of the pro-inflammatory gene (tnf-α). In terms of dietary lipid reduction, supplementation with 0.1% lysophospholipid allowed a 1% reduction in dietary lipid level without affecting the growth performance of largemouth bass, whereas at the same level of lysophospholipid supplementation, a 2% reduction in dietary lipid level resulted in decreased growth performance of largemouth bass. These findings provide theoretical support for the practical application of lysophospholipids, and demonstrate that reducing dietary lipid inclusion by adding lysophospholipids helps to reduce feed costs and improve aquaculture economic benefits. Full article

A 6-week feeding trial evaluated composite protein mixtures as partial replacements for fish meal (FM) in diets for juvenile yellowtail (Seriola quinqueradiata). Five diets were prepared: a control diet (C) with FM as the main protein source, and four test diets in which 25% and 35% of FM protein were replaced by either a composite mixture of SSM (44% shark by-product meal + 56% surimi by-product mixture; SS25 and SS35) or SMM (58% shark by-product meal + 42% other by-product mixture; SM25 and SM35). Fish (initial mean weight 0.85 g) were stocked at 30 fish per 500-L tank, with three replicate tanks per treatment. Growth performance indicators, including final mean weight, percent weight gain, specific growth rate, daily feeding rate, and survival, did not differ significantly among treatments (p > 0.05). Feed efficiency was significantly higher in SS25 and SS35 than in the control (p < 0.05), whereas no significant differences were observed among the by-product-based diets. Whole-body proximate composition was unaffected, except for crude ash. The levels of key n-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid, were significantly lower in SM25 and SM35 than in the control (p < 0.05). These results indicate that up to 35% of FM protein can be replaced with shark by-product-based mixtures without compromising growth in juvenile yellowtail. Full article

Water-soluble pectin (WSP) is a soluble dietary fiber with a high esterification degree and certain viscosity and emulsifying properties. It has diverse bioactivities—including antioxidant, anticancer, and anti-inflammatory properties. This study aimed to investigate the in vitro antioxidant mechanisms of water-soluble pectin, and the in vivo effects of intestinal antioxidant capacity and gut microbiota composition in hybrid grouper (Epinephelus lanceolatus♂ × Epinephelus fuscoguttatus♀). In an experiment involving feeding fish with WSP added to the diet, the addition of 600 mg/kg WSP promoted the activities of CAT, SOD, and GSH-Px in the grouper intestinal tract, thereby enhancing the antioxidant properties. At the phylum level, the relative abundance of Actinomycetes and Armatimonadetes decreased significantly. At the genus level, the relative abundance of Vibrio and Subdoligranulum increased significantly. In addition, antioxidant genes, inflammatory factor genes, immune genes, apoptosis genes, and genes of specific transmembrane proteins may participate in the regulation and improvement of the hybrid grouper intestinal tract. (CAT, MnSOD, and GPX), (TNF-α, IL-β, IL-6, and TGF-β), (MHC2, TLR3, KEAP1, and IKK-α), (C3, C8, C9, and P53), and (Claudin-3a, Occludin, ZO-1, and ZO-3) may regulate the intestinal function of hybrid grouper. Therefore, adding an appropriate volume of WSP to the diet is beneficial for the intestinal health of hybrid groupers. Full article

Research designed to reduce or eliminate fishmeal (FM) in trout feeds, for reasons that have changed over time, has been conducted for over a century. Reducing the dependency on FM remains one of the most urgent issues facing the industry. Feed represents the most expensive operational cost of fed aquaculture, and is responsible for ecosystem disturbance following nutrient discharges. Rainbow trout, the second most farmed salmonid globally, can be raised completely without FM or fish oil (FO), with its growth and efficiency not differing from trout fed FM-based feeds. However, ingredient choice and nutrient supplementation strongly influence physiological responses, efficiency, and long-term outcomes. As land animal proteins are increasingly used in place of FM, both with and void of dietary FO, their distinct biological effects warrant focused evaluation. Although numerous studies have synthesized findings across various alternative protein categories including those with insect proteins and animal by-products, this literature is widely disseminated and sometimes difficult to access. The present contribution focuses on terrestrial/aerial animal proteins that have been used to totally replace FM in rainbow trout feeds. Attention is given to their effects on physiological control processes that may influence production efficiency. Areas worthy of future study are identified and include long-term performance and health dynamics, the refinement of nutritional and formulation strategies, and the broader evaluation of biological interactions and system-level outcomes. Full article

Sustainable expansion of global aquaculture relies on innovative alternative diets that reduce dependence on marine-derived ingredients. Poultry by-product meal (PBM) and insect meal have emerged as promising protein sources, yet their combined use under commercial farming conditions remains poorly explored. This study evaluated a plant-based finishing diet low in marine proteins and supplemented with 10% Hermetia illucens larvae meal (HIM) and 30% PBM (H10P30) and compared it with a conventional commercial diet (COM) in gilthead sea bream (Sparus aurata) reared on a land-based farm for 65 days. Health and welfare indicators, product safety, fillet quality, fatty acid profile, oxidative status, and consumer acceptance were assessed. Fish fed the H10P30 diet showed a significantly higher body weight and specific growth rate and a lowered feed conversion ratio than COM-fed fish. No external or internal lesions or liver histopathological alterations related to the H10P30 diet were observed. While the diet influenced the fatty acid profile of raw fillets, differences disappeared after cooking, except for a higher C22:6n-3 content in cooked H10P30 fillets. Sensory analysis penalised COM fillets due to the perceived hard texture and low juiciness. In summary, incorporating both PBM and HIM into a plant-based finishing diet serves as a viable feeding strategy for gilthead sea bream, contributing to improved feed sustainability. Full article

Subadult flathead grey mullets (Mugil cephalus) were fed three experimental diets containing increasing percentages of partially defatted black soldier fly (Hermetia illucens, BSF) that proportionally replaced the protein sources in the reference diet. At the end of the feeding trial, fish growth and gut, liver and spleen histology were evaluated. BSF inclusion did not significantly affect growth performances in any dietary groups. However, Fulton’s condition factor was lower in fish who were fed diets with the highest replacement levels (15% and 20%; BSF15 and BSF20) compared to those fed the 10% replacement (BSF10) and the control diet (BSF0). Histological analyses revealed increased villi thickness and mucous cell proliferation in the intestine of fish from BSF10 and BSF15 groups. A significant worsening of intestinal condition was observed in fish from the BSF20 group. Liver histology was not affected, while a dose-dependent effect on spleen was observed in fish fed BSF inclusions. Despite the absence of enteritis signs, an increase in macrophages/like TNF-α+ cells in the intestine mucosa indicated immune stimulation in the BSF10 group. Results indicate, for the first time, a threshold for BSF meal inclusion in diets specifically formulated for flathead grey mullets. The BSF10 diet was optimal, as growth performance was not affected and intestine health improved at both morphological and innate immune system levels. Full article

Skin pigmentation is a crucial factor influencing the market value of gilthead seabream. A three-month feeding trial evaluated the effects of dietary inclusion of Rhodotorula mucilaginosa on skin and fillet pigmentation of gilthead seabream (Sparus aurata). Four diets containing yeast were tested in triplicate tanks using 120 fish in total. Skin and fillet colours were assessed via computer-based image analysis in CIELAB, RGB and HSB spaces. Analysis of total carotenoids was also performed. Yeast inclusion increased L* and Whiteness values in the operculum and enhanced lightness in ventral skin regions. In the abdominal area, RGB values decreased, particularly in the 3% diet. Fillet responses were limited to the red muscle, where the 3% diet significantly increased a* and Chroma values. Overall, inclusion of R. mucilaginosa exceeding 2% influenced seabream skin brightness and total carotenoid content, while 3% inclusion enhanced red muscle pigmentation, suggesting potential as a natural pigment source in seabream feeds. Full article

This study investigated the effects of Lycium barbarum polysaccharides (LBP) supplementation on various indicators in coral trout (Plectropomus leopardus), including growth performance, digestive enzyme activity, muscle and skin morphology, inflammatory immune gene expression, as well as immune and antioxidant responses. In the experiment, fish were fed diets supplemented with different concentrations of LBP (0%, 0.05%, 0.1%, 0.2%, 0.5%, and 1%) over a designated experimental period. The results showed that moderate supplementation of LBP significantly improved growth performance, with the optimal concentration being around 0.243%, achieving the highest specific growth rate. LBP supplementation also enhanced intestinal digestive enzyme activity, such as trypsin in the 0.1% and 1% groups, and α-amylase in the 0.5% group. Additionally, LBP improved the nutritional composition of muscle, with the 1% group showing higher crude protein content and the 0.2–1% groups having lower crude fat content. Moderate LBP supplementation improved skin color and pigmentation, increasing the brightness, redness, and yellowness of the dorsal skin, as well as boosting carotenoid and astaxanthin concentrations. It also enhanced the immune and antioxidant functions of the skin (e.g., SOD, CAT, GSH-Px, AKP, and LZ) and improved the immune functions of the mucus (e.g., C3, C4, IgM, IgT, AKP, and LZ). Furthermore, the expression of key pro-inflammatory genes, such as TNF-α and IL-1β, was reduced. These findings suggest that LBP can serve as a natural feed additive to enhance the overall quality and health of coral trout, contributing to sustainable aquaculture practices. Full article

The valorization of agricultural by-products as functional feed additives represents a promising strategy for sustainable aquaculture. This study evaluated the effects of dietary fermented longan peel (FLP), produced through enzymatic hydrolysis and Lactiplantibacillus plantarum fermentation, on growth performance, digestive physiology, gut morphology, innate immunity, and gene expression in Nile tilapia (Oreochromis niloticus) cultured under a biofloc system. Five experimental diets were formulated with graded FLP levels (0, 5, 10, 20, and 40 g kg⁻¹) and fed to fish for eight weeks. Growth indices, including final weight, weight gain, and specific growth rate, improved significantly in fish receiving 20 g kg⁻¹ FLP, following a strong quadratic response pattern. In vitro digestibility assays showed enhanced carbohydrate and protein digestibility, coinciding with increased intestinal amylase and protease activities. Histological analysis indicated that moderate FLP inclusion (10–20 g kg⁻¹) promoted villus height, crypt depth, and epithelial organization. Innate immune parameters, including lysozyme, peroxidase, and alternative complement activity, were markedly elevated in serum and mucus, particularly at 20–40 g kg⁻¹ after eight weeks. Gene expression profiling revealed significant up-regulation of growth-related (IGF-1, GH, NPY-α, Galanin), immune-related (TLR-7, TNF-α, NFκB), and antioxidant-related (hsp70, Keap-1, nrf-2, GST-α) genes in fish fed higher FLP levels, with responses plateauing beyond 20 g kg⁻¹. Overall, FLP supplementation at 20 g kg⁻¹ optimally enhanced growth, digestive efficiency, intestinal health, and innate immune status. These findings demonstrate the potential of fermented longan peel as a cost-effective, bioactive, and sustainable functional feed ingredient for tilapia and other warm-water aquaculture species. Full article

Light is a critical factor influencing fish behavior, yet the low-light conditions in deep-sea cages may impair feeding in visual species like rainbow trout Oncorhynchus mykiss (Walbaum, 1792). This study investigated the effects of light intensity and photoperiod on the feeding behavior of rainbow trout. Using green light, a factorial design tested three light intensities (10, 100, and 1000 lx) and three photoperiods (8L:16D, 16L:8D, and 24L:0D), alongside a complete darkness control (0 lx and 0L:24D). Key behavioral parameters during feeding were quantified via video analysis. The results showed significant main and interactive effects of light intensity and photoperiod on feeding behaviors. Feeding activity was substantially suppressed under continuous darkness. On the initial experimental day, exploratory movement was greatest under 10 lx and 8L:16D. Following 50 days of exposure, fish in light groups exhibited more focused swimming trajectories near the feeding point, indicating behavioral adaptation and spatial learning. Correlation analyses suggested a strategic shift from broad exploration to precise, efficient localization over time. In conclusion, specific lighting conditions, notably low intensity under a regular photoperiod, promote efficient feeding behavior in rainbow trout, whereas darkness or extreme light regimens are inhibitory. These findings reveal adaptive behavioral plasticity in this species and provide a scientific basis for optimizing light management in offshore salmonid aquaculture. Full article

Brackish aquaponics is expected to be a promising approach to sustainable food production, integrating saline water resources with simultaneous co-cultivation of fish and halophytes. The present study investigated the effects of three feeding ratios (FR1.5: 1.5%, FR3: 3%, and FR6: 6% b.w/d) on the growth performance of European sea bass (Dicentrarchus labrax) and glasswort (Salicornia europaea) co-cultured in three autonomous one-loop recirculation aquaponic systems (180 L each) at 20 ppt salinity over 78 days. Each system comprised three fish-rearing tanks connected to a two-stage sump filter and a nutrient film technique (NFT) hydroponic subsystem. Sea bass fed at FR3 achieved significantly higher weight gain, specific growth rate, and feed conversion efficiency than FR1.5. At FR6, feed consumption nearly doubled compared to FR3 (3.79 vs. 1.91 g), yet the feed conversion ratio increased from 0.79 to 1.65, and protein efficiency ratio declined from 3.80 to 1.91, indicating overfeeding effects. Regarding glasswort, FR6 produced significantly higher chlorophyll a content and plant biomass, whereas FR1.5 showed superior ammonia removal efficiency. Overall, FR3 provided the best balance between fish growth, plant yield, and water quality maintenance. These findings highlight the critical role of feeding management in brackish aquaponics in order to optimize nutrient coupling between fish and halophyte production. Full article

Encapsulated probiotics, which are promising approaches for improving aquaculture species’ performance and health, have incompletely characterized dose-dependent physiological and immunological effects. This study represents the first report evaluating the probiotic efficacy of a novel encapsulated Lysinibacillus sp. PWR01, originally isolated from rubber latex nodules, in Nile tilapia (Oreochromis niloticus). A total of 300 Nile tilapia (10.80 ± 0.07 g) was allocated to four experimental groups receiving 0, 10⁴, 10⁵, and 10⁶ CFU/g of encapsulated Lysinibacillus sp. PWR01 in their diet. At 8 weeks of the feeding trial, growth performance, feed utilization, serum antioxidant status, intestinal bacterial counts and immune-related gene expression were analyzed. Results demonstrated that fish fed 10⁶ CFU/g achieved a final weight of 51.48 g, representing a 9.88% increase compared with the control (46.85 g), while weight gain (WG) improved by 12.82% and specific growth rate (SGR) by 6.34%. Feed conversion ratio (FCR) was reduced by up to 18.42% at 10⁵ CFU/g relative to the control. Encapsulated groups enhanced serum superoxide dismutase activity without altering malondialdehyde levels, increased total intestinal bacterial and lactic acid bacteria counts, and selectively upregulated TLR2 and MHC II mRNA transcript levels. Histological analysis further revealed increased intestinal villus height and width in encapsulated-fed groups, while liver architecture remained normal across treatments. Multivariate analyses demonstrated strong positive associations among growth performance, gut microbiota enrichment, and immune gene expression. Resistance to Aeromonas hydrophila infection was significantly improved at higher dietary doses, with post-challenge survival reaching 61.67–75% in supplemented groups versus 45.00% in controls. These findings demonstrate that latex-derived Lysinibacillus sp. PWR01 acts as a strain-specific immunomodulatory probiotic that enhances growth, antioxidant capacity, microbial community balance, and disease resistance to Nile tilapia. Future studies should investigate the role of the Nrf2 antioxidant pathway, clarify TLR2-mediated immune signaling, and assess gut microbiota–immune system interactions within commercial-scale production systems. Full article

The gonadal development of Japanese eels (Anguilla japonica) plays a crucial role in the success of artificial breeding. Soy isoflavones, a class of phytoestrogens commonly found in aquafeeds, have shown potential in enhancing gonad development in fish. The present study evaluated the effects of dietary soy isoflavones on gonadal development, growth performance, histology, sex hormone levels, vitellogenin content, and expression of related genes in female Japanese eel broodstock. A 4-week feeding trial was conducted with 120 two-year-old female eels randomly assigned to four groups and fed diets containing 0 (C), 0.1 (L), 0.5 (M), and 0.9 (H) mg/g of soy isoflavones. The results indicated that gonadal development was enhanced in the M and H groups, as evidenced by a significantly higher gonadosomatic index (GSI) and increased oocyte cross-sectional area (CSA) in M group, and greater nutrient accumulation in both the M and H groups. The expression of er and cyp19a genes in the ovary was downregulated in the treatment groups, leading to decreased serum estradiol (E2) and increased testosterone levels. Furthermore, hepatic vtg gene expression was upregulated in the M and H groups, though VTG protein content remained unchanged, suggesting an initiation of vitellogenesis at the transcriptional level. In conclusion, dietary soy isoflavones at 0.5–0.9 mg/g provide an effective pretreatment strategy to enhance early ovarian development in Japanese eel broodstock, potentially improving their responsiveness to subsequent hormonal induction in artificial breeding programs. Full article