Search Results (929)

The high demand and economic value of kingfish (Scomberomorus commerson) have led to intensive fishing of this species in the Omani waters. The increased fishing pressure has made the fishery vulnerable; hence, information on the current stock status is essential for the sustainability of the kingfish stock. Three length-based stock assessment approaches (TropFishR, spawning potential ratio, and Bayesian biomass method) were used to estimate growth, mortality, exploitation, spawning potential capacity, and relative biomass in relation to maximum sustainable yield (MSY). Asymptotic length (L_∞) was 186.31 cm, and the growth coefficient (K) was 0.15 yr⁻¹ for S. commerson. Fishing mortality was 0.45 yr⁻¹, which was higher than natural mortality (M = 0.18 yr⁻¹) and optimal fishing mortalities (F40% = 0.15 yr⁻¹). The exploitation rate (E) was found to be 0.71 yr⁻¹, higher than the optimum exploitation (E = 0.50), indicating a total overfishing of 42% of the S. commerson in Oman waters. The current length at first capture (Lc50 = 74.38 cm) was significantly smaller than the length at first maturity (Lm50 = 91.25 cm), indicating growth overfishing. The current spawning potential ratio (SPR) was 10%, which was significantly below the reference point (SPR = 20%), indicating that the stock was severely overfished. Biomass was critically low (B/Bo = 0.17), and lower than the reference point of 0.20. Additionally, the current biomass was 44% of Bmsy (B/Bmsy = 0.44), which is significantly lower than the reference point of 1, indicating that the stock biomass was below the maximum sustainable yield level, suggesting recruitment overfishing. Stock indicators revealed that the fishery was primarily targeting immature/juvenile fish, as well as older and larger fish, which indicated stocks were both growth- and recruitment-overfished. Therefore, carrying out commercial fishing for an optimum size range (118 to 144 cm) and reducing fishing pressure to a sustainable level (F = M, 0.18 ^yr−1) would sustain a healthy stock biomass of kingfish in Omani waters. Full article

Gut health is essential for optimal growth, immune function, and robustness in aquaculture. This study evaluated the potential of dietary supplementation with micro- and macroalgae to promote intestinal recovery following an insult. Four experimental diets were formulated for gilthead seabream (Sparus aurata) juveniles (176 ± 0.32 g): a control commercial-like diet (CTRL), and the same diet supplemented with either microalgae (Phaeodactylum tricornutum; PHA) or macroalgae (Gracilaria gracilis; GRA) at 2.5%, or a 5% blend of both (50:50; BLEND). To induce an intestinal insult, fish from each dietary group were assisted-fed with gelatine capsules containing soy saponins (CTRL + S, PHA, GRA, BLEND), while control fish received empty capsules (CTRL). After 72 h, CTRL and CTRL + S groups were fed the control diet, while PHA, GRA, and BLEND received their respective algae-supplemented diets. After 20 days, CTRL + S fish had significantly increased mucus cell numbers and submucosal cellular infiltration compared to CTRL fish, indicating intestinal disruption. PHA diet significantly upregulated igm, il10, and gpx. Fish fed GRA displayed a significant increase in mucosal vacuolation. BLEND diet showed synergistic effects, significantly upregulating il1b and pcna and reducing ALP activity. These results highlight the potential of combining micro- and macroalgae compounds to enhance gut recovery and immune activation. Full article

Hydrogen-rich water (HRW) is known for its antioxidant, anti-inflammatory, and growth-enhancing properties. However, research on its effects on mandarin fish (Siniperca chuatsi) is limited. This study aimed to explore the effects of HRW on the growth and liver antioxidant capacity of mandarin fish. A total of 3600 fish, with an initial average weight of 30 ± 1 g, were randomly divided into four groups (three replicates each) and treated with HRW for 0 h (control), 1 h, 2 h, and 3 h over an 8-week period. In this study, we found that HRW significantly enhanced weight gain, specific growth rate, and feed intake in mandarin fish, while reducing the feed conversion ratio. It also boosted antioxidant enzyme levels (SOD and GSH-PX) in the liver and lowered MDA. Additionally, HRW increased muscle growth-related gene expression (mrf4, myos, myod, mhc) and upregulated appetite-related genes (npy and agrp) while decreasing leptin levels. This study reveals that a hydrogen concentration of 200–320 ppb, especially with a 2 h HRW treatment, produces the most significant antioxidant effects in juvenile mandarin fish, while a 3 h treatment notably enhances growth. These findings offer valuable insights and support for the advancement of the mandarin fish breeding industry. Full article

This study investigated the effects of vitamin E supplementation on growth performance, antioxidant capacity, and hepatic lipid metabolism in one-year-old juvenile Chinese sturgeon (Acipenser sinensis). A total of 270 fish (initial weight 1.37 ± 0.04 kg) were allocated into 9 fiberglass tanks and fed isonitrogenous and isolipidic diets with graded concentrations of vitamin E (DL-α-tocopherol acetate) including, 0, 1000, and 2000 mg/kg, respectively, for 2 months. Results showed that 1000 mg/kg vitamin E significantly improved growth performance and decreased hepatosomatic index. Dietary vitamin E supplementation significantly reduced the hepatic crude protein and crude lipid levels, withnot significantly affecting moisture and crude ash. Dietary vitamin E led to significant increases in plasma high-density lipoprotein cholesterol and vitamin E levels, while decreasing plasma low-density lipoprotein cholesterol. Additionally, it raised liver vitamin E content and reduced hepatic triglycerides, total cholesterol, crude protein, and crude lipid levels. Vitamin E also significantly downregulated mRNA levels of lipogenesis-related genes (ACC1, acetyl-CoA carboxylase 1; FASN, fatty acid synthase; and PPARγ, peroxisome proliferator activated receptor γ) and inhibited the enzyme activities of ACC1 and FASN, while upregulating lipolysis-related genes (HSL, hormone-sensitive lipase; CPT1, carnitine palmitoyltransferase 1α, and PPARα, peroxisome proliferator activated receptor α) and enhancing the activities of HSL and CPT1α. Furthermore, vitamin E supplementation significantly improved plasma reduced glutathione and superoxide dismutase activities, lowered plasma reactive oxygen species, malondialdehyde levels, and hepatic malondialdehyde contents, and upregulated mRNA levels of hepatic Nrf2 (nuclear factor-erythroid 2 related factor 2), Keap1 (Kelch-like epichlorohydrin associating protein 1), and CuZnSOD (copper/zinc superoxide dismutase). In conclusion, dietary 1000 mg/kg vitamin E supplementation could improve growth performance, enhance antioxidant capacity, and reduce liver fat deposition, indicating its potential as a beneficial dietary additive for promoting health and lipid regulation in juvenile Chinese sturgeon. Full article

Microalgal protein demonstrates considerable potential for reducing dependence on fishmeal in aquafeeds. However, limited research has been conducted on the effects of Chlorella pyrenoidosa meal (CM) on carnivorous fish species. This study evaluated the impact of replacing 0% to 40% of fishmeal with CM within isonitrogenous and isolipidic diets (designated as CM0, CM5, CM10, CM20, and CM40) on juvenile tiger puffer (initial weight: 11.34 ± 0.01 g) over a 56-day feeding trial. Three replicate tanks were established for each experimental group, with 30 fish per tank. The experimental data were statistically analyzed using one-way analysis of variance (ANOVA) and regression analysis. The results showed that no significant differences were observed in final body weight (FBW: CM0, 55.45 ± 1.87 g; CM40, 45.6 ± 2.09 g) or specific growth rate (SGR: CM0, 2.83 ± 0.06%/d; CM40, 2.48 ± 0.08%/d) among the dietary groups; however, the growth linearly decreased with increasing CM levels. The CM40 group exhibited a significantly higher feed conversion ratio (FCR: CM0, 1.17 ± 0.02; CM40, 1.28 ± 0.03). Muscle texture parameters (hardness, adhesiveness, cohesiveness, springiness, gumminess, and chewiness) and proximate composition were not significantly affected by dietary treatments. In contrast, the CM40 diet significantly decreased the n-3/n-6 polyunsaturated fatty acid (PUFA) ratio in the muscle, while increasing the contents of 18:2n-6 and total n-6 PUFAs. These results indicate that substituting up to 5% of fishmeal with CM did not produce significant adverse effects on growth or body composition, although linear trends indicated a progressive decline in performance at higher inclusion levels. This investigation provides valuable insights into the application of sustainable protein alternatives in feeds for marine carnivorous fish. Full article

Aquaculture faces challenges in reducing feed costs while promoting sustainable use of by-products. This study aimed to evaluate the effects of totally replacing soybean oil (SBO) with fish by-product oil (FBO) in the diet of Colossoma macropomum, focusing on growth performance, physiological and hepatic responses, meat composition, and economic viability. A total of 360 juveniles (9.1 ± 0.59) were distributed in a randomized design with six treatments (0–100% SBO replacement) and six replicates each, and fed to apparent satiation for 91 days. Growth performance did not differ significantly among treatments (p > 0.05), although fish receiving 40% FBO achieved the best feed conversion ratio among treatments. Hematological and biochemical analyses indicated that higher FBO levels (particularly 100%) indicating subtle yet adaptive physiological adjustments, such as moderate modulations in lipid metabolism and erythropoietic activity. Liver weight and hepatosomatic index decreased linearly with increasing FBO levels. In meat composition, FBO inclusion enhanced protein and reduced lipid contents. Although economic indicators were not statistically different (p > 0.05), offered the most favorable trade-off between biological performance and economic efficiency. These findings demonstrate that partial replacement of SBO with FBO, particularly at 40%, represents a sustainable and economically viable alternative for C. macropomum farming. Full article

This study aimed to explore the effects of dietary rapeseed meal replacing fish meal on growth performance, intestinal structure, gut microbiota, and related gene expression of juvenile largemouth bass (Micropterus salmoides). Five isonitrogenous and isolipidic diets were designed, in which rapeseed meal replaced 0% (FM, control), 5% (RM5), 10% (RM10), 15% (RM15), and 25% (RM25) of fish meal. Then, largemouth bass (11.00 ± 0.20 g) were randomly and equally allocated to 15 experimental tanks (25 fish per tank) for an 8-week feeding trial. The results showed that growth performance declined as replacement levels increased to 25%. However, the RM5 group had the highest body crude protein, distal intestinal muscle layer thickness (MLT), and plica height (PH) and width (PW), which were significantly higher than those of the FM group. In addition, compared to the FM group, the RM15 and/or RM25 groups had higher levels of D-lactic acid, diamine oxidase, and lipopolysaccharide. Furthermore, the RM25 group exhibited higher abundances of Lactococcus and Weissella but lower levels of Aeromonas and Staphylococcus compared to the FM group. Intestinal transcriptome analysis revealed that the PI3K-Akt and NF-κB signaling pathways were significantly up-regulated when comparing the RM25 and FM groups. The results demonstrate that the replacement of 5% fish meal with rapeseed meal did not have a negative impact on the physiological status of largemouth bass. However, a replacement level of 25% reduced growth performance and damaged intestinal structure, potentially by altering the abundance of intestinal microbiota and up-regulating the PI3K-Akt and NF-κB signaling pathways. Full article

Low-fishmeal feed is increasingly being adopted across the global aquaculture industry. This study evaluated dietary Clostridium butyricum and alanyl-glutamine (Ala-Gln) supplementation in juvenile triploid rainbow trout (Oncorhynchus mykiss) with a low-fishmeal diet. Four diets were tested: basal diet (SBM, 15% fishmeal and 21.6% soybean meal), SBM + 0.5% C. butyricum (CB), SBM + 1.0% Ala-Gln, and SBM + 0.5% C. butyricum + 1.0% Ala-Gln (CB-AG). Fish were fed in 500 L tanks in recirculating aquaculture systems for 8 weeks (62.52 ± 0.47 g). Each group comprised three tanks, with each tank housing 30 fish. Then 10 fish per tank were challenged with Aeromonas salmonicida. CB-AG showed significantly higher weight gain and specific growth rates than the SBM group (p < 0.05). Mortality was significantly lower in CB-AG and AG than in SBM after A. salmonicida challenge. Histomorphology revealed significant differences (p < 0.05) between CB-AG and SBM in muscularis thickness, villus width, and height. SBM sections showed inflammatory infiltration and border damage were attenuated in supplemented groups. Serum malondialdehyde (MDA) and dioxygenase (DAO) were significantly lower in CB-AG than SBM (p < 0.05), while serum and hepatic lysozyme (LZM) and hepatic superoxide dismutase (SOD) were higher. Digestive enzymes indicated significantly higher trypsin and lipase activities in CB-AG (p < 0.05). CB-AG upregulated intestinal tight junction proteins and PepT1 and downregulated pro-inflammatory mediators. Combined 0.5% C. butyricum and 1.0% Ala-Gln inclusion effectively preserved growth performance, antioxidant capacity, gut microbiome homeostasis, and intestinal health in rainbow trout on low-fishmeal diets. Full article

Sequentially hermaphroditic fish begin life as one sex and change to another at some stage of their lifecycle. To date, the majority of research into this fascinating process has focused on sex change in sexually mature fish. The current study on the New Zealand spotty wrasse (Notolabrus celidotus) seeks to describe sex change in sexually immature females that are transitioning to become so called initial-phase males. This was achieved through analysis of gonadal histology, and the expression of key genes involved in sex differentiation (amh, dmrt1, and cyp19a1a) and methylation (dnmt1 and dnmt3a). It was found that initial-phase (IP) male spotty wrasse likely reach sexual maturity at a much earlier developmental stage and smaller size than previously realised. This study furthermore shows that all juvenile spotty wrasse are female first, before some individuals undergo pre-maturational sex change to become IP males. Thus, we confirm diandry in the protogynous New Zealand spotty wrasse and provide clarity around the definitions of primary male formation. Full article

Recirculating aquaculture systems (RAS) address pollution, disease, and sustainability in commercial fish farming, but marine RAS are limited by biofilter maturation and nitrification. This study investigated the effects of air nanobubbles on water quality, fish growth, and bacterial communities in marine RAS stocked with juvenile Malabar red snapper, barramundi and saline-tolerant hybrid tilapia. Flow cytometry was evaluated as a rapid management tool for non-culturable microbes, finding viable bacterial counts 30–100 times higher than conventional total plate counts. There were no significant differences in fish growth, survival, or Feed Conversion Ratio between groups, likely due to low stocking densities (<20 kg/m³) and high water exchange rates (>100%/hour), indicating low system stress. Air nanobubbles did not significantly increase dissolved oxygen levels. While bacterial abundance in water was consistently higher in nanobubble-treated RAS (RAS-N), tank walls showed less biofilm. RAS-N also exhibited a higher abundance of nitrifying bacteria like Nitrospira and Marinobacter, leading to improved nitrogenous waste breakdown and lower nitrite levels. Future research should investigate nanobubbles’ benefits at higher stocking densities and longer durations to fully assess their impact on intensive aquaculture. Full article

Background: The extensive use of antibiotics in aquaculture has raised serious concerns, emphasizing the need for sustainable and natural alternatives. This study evaluated the potential of red dragon fruit (Hylocereus polyrhizus) juice by-products (RJB) as a functional feed additive for juvenile red seabream (Pagrus major). Materials and Methods: The bioactive composition and antioxidant capacity of RJB were analyzed, and five experimental diets containing 0, 0.2, 0.4, 0.8, and 1% RJB were fed to fish for 56 days. Results: Growth performance, feed utilization, body composition, antioxidant enzyme activities, and lysozyme activity were evaluated. RJB contained substantial levels of phenolic and flavonoid compounds and exhibited strong radical-scavenging activity. Dietary inclusion of up to 1% RJB did not significantly affect growth, feed efficiency, or plasma biochemistry. However, fish fed the 1% RJB diet showed increased catalase and glutathione levels, significantly enhanced lysozyme activity, and improved survival following Edwardsiella tarda infection. Conclusion: These results demonstrate that RJB can be safely incorporated into marine fish diets to enhance antioxidant capacity and innate immune defense. The valorization of fruit-processing by-products such as RJB offers a promising strategy for developing antibiotic-free and sustainable aquaculture practices. Full article

This study evaluated the effects of feeding juvenile southern catfish (Silurus meridionalis) with one of six isonitrogenous and isoenergetic diets where fish meal (FM) was replaced by black soldier fly larval meal (BSFLM) at 0%, 10%, 20%, 30%, 40%, and 50% levels on growth, muscle quality, antioxidant capacity, immune response, and gut microbiota of juvenile southern catfish (Silurus meridionalis). A total of 1620 fish (9.20 ± 0.15 g) were fed one of six experimental diets for 8 weeks. Results demonstrated that a 50% replacement (H50 group) significantly improved weight gain rate, specific growth rate, and protein efficiency ratio (p < 0.001). Antioxidant capacity (T-AOC) was enhanced in groups H30 and H50, while immune markers lysozyme (LZM) and alkaline phosphatase (AKP) showed mixed responses. Muscle texture properties such as chewiness and adhesiveness were significantly altered across treatments. Gut villi remained structurally intact in all groups, and liver histology appeared normal. No significant differences were found in muscle amino acid or fatty acid profiles. Gut microbiota analysis revealed shifts in microbial composition, with increased abundance of Clostridia and Escherichia and functional enrichment in metabolic pathways at higher substitution levels. Interspecies network analysis indicated potential cooperation among beneficial microbes through metabolite exchange. It is concluded that 50% BSFLM substitution optimizes growth performance, muscle quality, and antioxidant capacity, while modulating gut microbiota, indicating its promise as a sustainable FM alternative and functional ingredient in aquafeeds. Full article

The overexploitation of wild populations for the marine ornamental trade necessitates optimized captive breeding, particularly for iconic species like the clownfish Amphiprion ocellaris. This study investigated the social behavior and cognitive abilities of juvenile clownfish in relation to artificial rearing practices. Using modified three-tank tests, we assessed social preference and cognition ability in two size groups: Small-bodied Group (SG: 2.0–2.5 cm) and Large-bodied Group (LG: 3.5–4 cm). The results indicated that clownfish have the following: (a) Strong Social Preference: Both SG and LG exhibited significant preference for areas near conspecifics (SPI > 0), with SG showing significantly higher SPI values than LG. (b) Developmental Stage Differences: SG demonstrated a stronger tendency to cluster tightly near conspecifics. LG showed wider exploration patterns and greater movement. (c) Cognition Ability: SG showed renewed interest towards a novel fish after habituation to a familiar fish, while LG displayed a stronger preference for the familiar fish. These findings suggest that clownfish juveniles possess advanced sociality and basic cognition ability. Furthermore, the observed shift in social interaction preference with developmental stages informs optimal timing for grading practices to minimize artificial rearing stress. This study provides some behavioral insights for optimizing large-scale artificial rearing protocols for clownfish, reducing pressure on wild populations. Full article

Biomass of the plumose anemone Metridium senile has surged in the benthic ecosystem of the North Yellow Sea in recent years. Understanding its diet and the proportional contributions of food sources is essential for assessing the ecological consequences of this expansion. The species is often characterized as a passive suspension feeder, yet laboratory feeding trials have documented shrimp consumption. Because prior dietary information from the region is scarce, conventional stable isotope approaches are poorly constrained. We developed an integrative framework coupling trophic position estimation, isotopic niche metrics, spatial point pattern analysis, and a Bayesian mixing model to improve diet attribution under limited prior information and to test whether M. senile preys on small-bodied and juvenile teleosts and invertebrates under natural conditions. Our analyses showed that: (i) M. senile occupied a high trophic position (TP = 3.09 ± 0.25), exceeding those estimated for putative predators in our dataset, implying weak top-down control; (ii) in isotopic niche analyses, M. senile showed high posterior probabilities of occurring within the niches of cephalopods and medium-sized fishes (78.30% and 63.04%, respectively), consistent with shared prey and inconsistent with a strictly suspension-feeding strategy; (iii) mixing space diagnostics informed by spatial point pattern analysis indicated that including small-sized fishes and shrimps as sources was necessary to reconcile the elevated TP; and (iv) the Bayesian mixing model estimated that small-bodied and juvenile teleosts and invertebrates supplied most long-term nutrition (posterior mean ≈ 0.65), with the remainder from suspension-derived sources, consistent with an opportunistic generalist rather than a strict suspension feeder. Sustained predation on small-bodied and juvenile teleosts and invertebrates could suppress early fish recruitment, impose top-down control on forage species, and alter the local food web structure. Management should monitor M. senile (size structure, population density, and co-occurrence with juveniles and forage biota) and consider targeted removals and seafloor litter cleanups in priority habitats. The framework is applicable to diet studies with limited prior information; adding δ³⁴S, compound-specific amino-acid isotopes (CSIA-AA), and DNA-based dietary evidence should further sharpen source discrimination. Full article

This research explored the effects of supplementing taurine in a low-fishmeal diet on the growth, hepatic antioxidant capacity, muscle quality, intestinal health, and alleviation of inflammatory response of golden pompano (Trachinotus ovatus). Over an eight-week period, 300 juvenile fish (initial weight 9.4 ± 0.47 g) were randomly allocated into 12 net enclosures (1.0 × 1.0 × 1.5 m), with each treatment group comprising three replicate cages containing 25 specimens. The results demonstrated that an optimal taurine inclusion level of 1.0–1.5% significantly promoted growth, as evidenced by the increased weight gain rate (WGR) and specific growth rate (SGR). It also protected hepatic health by reducing alanine aminotransferase (ALT) activity and enhancing antioxidant capacity. Activation of the hepatic Nrf2/Keap-1/HO-1 signaling pathway increased the level of antioxidant gene expression, including catalase (CAT) and superoxide dismutase (SOD). In addition, the appropriate supplementation of taurine significantly down-regulated muscle hardness-related genes (cathepsin B (CatB) and cathepsin L (CatL)) and promoted the growth and differentiation of myoblasts, thus improving muscle quality. The chymotrypsin of fish fed the A25T10 diet was significantly higher than those in other groups (p < 0.05). The amylase (AMY) of fish fed the A25T15 diet was significantly higher than those in other groups (p < 0.05). The Chao1, Shannon, and Simpson of fish fed the A25T15 diet were significantly higher than those in other groups (p < 0.05). Proteobacteria were the most abundant in group A25T10. The relative abundance of Photobacterium rose in the A25RT10 group. In this study, taurine supplementation can down-regulate the expression of intestinal pro-inflammatory factors (interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8)) and up-regulate the expression of anti-inflammatory factor interleukin-10 (IL-10), enhance intestinal immunity, and improve intestinal digestion and absorption. Therefore, the addition of 1–1.5% taurine to low-fishmeal feeds can improve the growth performance of golden pompano. Full article