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Simple Summary: The present study shows how different combinations of eco-efficient ingredients can be considered reliable solutions for European aquaculture production. For this purpose, three different formulations were designed and tested in a 77-day gilthead sea bream trial. All diets supported similar growth rates, but the diet without poultry meal and processed animal proteins as the main fish meal replacer (NOPAP diet) shaped better nutrient utilization with an overall improvement of biomarkers of physiological condition. Such an integrative approach contributes to better understanding of what could be the best and least-cost feed formulation for an effective balance of sustainability and aquaculture profitability in a scenario of intensive aquaculture production and limited availability of marine feed ingredients for fish production. The growth of the aquaculture industry requires more sustainable and circular economy-driven aquafeed formulas. Thus, the goal of the present study was to assess in farmed gilthead sea bream (Sparus aurata L.) how different combinations of novel and conventional fish feed ingredients supported proper animal performance in terms of growth and physiological biomarkers of blood/liver/head kidney. A 77-day feeding trial was conducted with three experimental diets (PAP, with terrestrial processed animal protein from animal by-products; NOPAP, without processed animal protein from terrestrial animal by-products; MIX, a combination of alternative ingredients of PAP and NOPAP diets) and a commercial-type formulation (CTRL), and their effects on growth performance and markers of endocrine growth regulation, lipid metabolism, antioxidant defense and inflammatory condition were assessed at circulatory and tissue level (liver, head kidney). Growth performance was similar among all dietary treatments. However, fish fed the PAP diet displayed a lower feed conversion and protein efficiency, with intermediate values in MIX-fed fish. Such gradual variation in growth performance was supported by different biomarker signatures that delineated a lower risk of oxidation and inflammatory condition in NOPAP fish, in concurrence with an enhanced hepatic lipogenesis that did not represent a risk of lipoid liver degeneration. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of starvation and refeeding on the growth and food intake of gilthead seabream (Sparus aurata) and seabass (Dicentrarchus labrax) and on the growth and nitrogen uptake of glasswort (Salicornia europaea) in a polyculture aquaponic system under 12 ppt salinity for 75 days. Nine small-scale autonomous aquaponic systems were used, each containing 10 gilthead seabreams (average weight of 6.33 ± 0.73 g and average length of 5.73 ± 0.72 cm) and 10 seabasses (5.82 ± 0.77 g and 6.35 ± 0.45 cm), as well as five glasswort plants. Three fish feeding treatments were performed, a control (A), in which fish were fed daily until satiation, and two fasting treatments for 4 (B) and 7 days (C). Fish growth performance was significantly lower (p < 0.05) in the C treatment for both species compared to treatments A and B. Food consumption (FC) and feed conversion ratio (FCR) were significantly higher (p < 0.05) in treatment C. Glasswort growth performance was significantly higher in treatment C (p < 0.05). The results showed that the 4-day food-deprived fish were similar to the control fish by achieving partial compensatory growth. The more extended fasting period (7 days) resulted in significantly lower growth performance. The lipid and nitrogen retention levels in both species were significantly lower in food-deprived fish than in the control fish both before and during compensatory growth. The results suggest that a feeding schedule involving starvation–refeeding cycles is a promising feed management option for these species in polyculture aquaponic systems. The effect of food deprivation was also significantly beneficial (p < 0.05) for the growth performance of glasswort compared to the control treatment. [ABSTRACT FROM AUTHOR]

Fish were kept for six weeks at three different initial stocking densities and water O2 concentrations (low-LD, 8.5 kg/m3 and 95–70% O2 saturation; medium-MD, 17 kg/m3 and 55–75% O2 saturation; high-HD, 25 kg/m3 and 60–45% O2 saturation), with water temperature increasing from 19 °C to 26–27 °C. The improvement in growth performance with the decrease in stocking density was related to changes in skin and intestinal mucosal microbiomes. Changes in microbiome composition were higher in skin, with an increased abundance of Alteromonas and Massilia in HD fish. However, these bacteria genera were mutually exclusive, and Alteromonas abundance was related to a reactive behavior and systemic growth regulation via the liver Gh/Igf system, while Massilia was correlated to a proactive behavior and a growth regulatory transition towards muscle rather than liver. At the intestinal level, microbial abundance showed an opposite trend for two bacteria taxa, rendering in a low abundance of Reyranella and a high abundance of Prauserella in HD fish. This trend was correlated with up-regulated host gene expression, affecting the immune response, epithelial cell turnover, and abiotic stress response. Most of the observed responses are adaptive in nature, and they would serve to infer new welfare indicators for increased stress resilience. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the effects of black seed (Nigella sativa) and AQUA-IMMUNOPROTECT® on growth, feed utilization, serum constituents, and disease resistance against vibriosis in gilthead sea bream juveniles. The research involved three groups: TC (control) received a basal diet, TSI (received a basal diet with 2% AQUA-IMMUNOPROTECT®), and TNS (received a basal diet with 2% N. sativa). The experiment period extended for 2 months. Results revealed a significant rise in erythrogram (RBCs, HB, and PCV %), leucogram (total differential leucocytic count), serum total protein, and globulin in gilthead sea bream treated with 2% Nigella sativa supplemented diets after an 8-week trial. No substantial variations were found in liver enzymes, urea, uric acid, and creatinine between the groups. Respiratory burst activity was notably greater in the N. sativa group after 2 months of feeding compared to the other groups. In the experimental challenge, the control group experienced higher mortality rates than the other groups following an IP injection of V. harveyi at a dose of 106 CFU per 0.5 ml/fish (106 fish/challenge). Overall, the findings of this research indicate that N. sativa can enhance non-specific immunity and minimize susceptibility and pathogenicity to V. harveyi in gilthead sea bream. [ABSTRACT FROM AUTHOR]

The Sirtuin (SIRT1-7) family comprises seven evolutionary-conserved enzymes that couple cellular NAD availability with health, nutrition and welfare status in vertebrates. This study re-annotated the sirt3/5 branch in the gilthead sea bream, revealing three paralogues of sirt3 (sirt3.1a/sirt3.1b/sirt3.2) and two of sirt5 (sirt5a/sirt5b) in this Perciform fish. The phylogeny and synteny analyses unveiled that the Sirt3.1/Sirt3.2 dichotomy was retained in teleosts and aquatic-living Sarcopterygian after early vertebrate 2R whole genome duplication (WGD). Additionally, only certain percomorphaceae and gilthead sea bream showed a conserved tandem-duplicated synteny block involving the mammalian-clustered sirt3.1 gene (psmd13-sirt3.1a/b-drd4-cdhr5-ctsd). Conversely, the expansion of the Sirt5 branch was shaped by the teleost-specific 3R WGD. As extensively reviewed in the literature, human-orthologues (sirt3.1/sirt5a) showed a high, conserved expression in skeletal muscle that increased as development advanced. However, recent sirt3.2 and sirt5b suffered an overall muscle transcriptional silencing across life, as well as an enhanced expression on immune-relevant tissues and gills. These findings fill gaps in the ontogeny and differentiation of Sirt genes in the environmentally adaptable gilthead sea bream, becoming a good starting point to advance towards a full understanding of its neo-functionalization. The mechanisms originating from these new paralogs also open new perspectives in the study of cellular energy sensing processes in vertebrates. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of starvation and refeeding on the growth and food intake of gilthead seabream (Sparus aurata) and seabass (Dicentrarchus labrax) and on the growth and nitrogen uptake of glasswort (Salicornia europaea) in a polyculture aquaponic system under 12 ppt salinity for 75 days. Nine small-scale autonomous aquaponic systems were used, each containing 10 gilthead seabreams (average weight of 6.33 ± 0.73 g and average length of 5.73 ± 0.72 cm) and 10 seabasses (5.82 ± 0.77 g and 6.35 ± 0.45 cm), as well as five glasswort plants. Three fish feeding treatments were performed, a control (A), in which fish were fed daily until satiation, and two fasting treatments for 4 (B) and 7 days (C). Fish growth performance was significantly lower (p

Abstract The economic impact of skeletal anomalies in aquaculture farming is a significant issue for the industry, as deformed fish are frequently discarded because of their low survival rate and a variety of other disadvantages, including increased costs, consumer distrust of aquaculture products, and ethical concerns. The goal of this article is to propose a method for calculating the direct costs of severe skeletal anomalies in typical Mediterranean seabream and seabass aquaculture hatcheries using a deterministic static model programmed in MATLAB that simulates their annual operation. Our findings suggest that larger hatcheries experience higher direct costs associated with severe skeletal anomalies but have better financial stability and significantly higher expected profits. Mean results indicate that the annual economic losses of severe skeletal anomalies for seabream and seabass Mediterranean aquaculture are 22.88 million euros per year for a scenario of low severe skeletal anomalies, 65.34 million euros per year for a scenario of medium severe skeletal anomalies, and 115.98 million euros per year for a scenario of high severe skeletal anomalies. Furthermore, some options for increasing the financial stability of the hatcheries are to increase the sale price of fingerlings, reduce the feed conversion ratio, and reduce the feed unit cost.

The economic impact of skeletal anomalies in aquaculture farming is a significant issue for the industry, as deformed fish are frequently discarded because of their low survival rate and a variety of other disadvantages, including increased costs, consumer distrust of aquaculture products, and ethical concerns. The goal of this article is to propose a method for calculating the direct costs of severe skeletal anomalies in typical Mediterranean seabream and seabass aquaculture hatcheries using a deterministic static model programmed in MATLAB that simulates their annual operation. Our findings suggest that larger hatcheries experience higher direct costs associated with severe skeletal anomalies but have better financial stability and significantly higher expected profits. Mean results indicate that the annual economic losses of severe skeletal anomalies for seabream and seabass Mediterranean aquaculture are 22.88 million euros per year for a scenario of low severe skeletal anomalies, 65.34 million euros per year for a scenario of medium severe skeletal anomalies, and 115.98 million euros per year for a scenario of high severe skeletal anomalies. Furthermore, some options for increasing the financial stability of the hatcheries are to increase the sale price of fingerlings, reduce the feed conversion ratio, and reduce the feed unit cost. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the growth performance of gilthead sea bream (Sparus aurata) fed with a mixture of a single cell ingredient (SCI) (bacterial protein, yeast protein and algae) for organic aquaculture. Sea bream with an initial mean body weight of 6.87±0.07 g were randomly allocated to 250-litre tanks. Four isonitrogenous, isolipidic and isoenergetic diets were formulated by replacing organic fishmeal trimmings with 0% (control), 12% (SCI12), 15% (SCI15) and 18% (SCI18) of the SCI mixture. Each diet was distributed to the groups in triplicate. The fish were fed three times daily until satiation and the experimental period was 60 days. Survival rates and voluntary feed intake were similar in the fish with the different feed treatments (p > 0.05). Similar (p > 0.05) growth performance (final weight, SGR) and feed conversion ratio (FCR) were observed in fish fed all SCI-based diets, which was superior to the control diet treatment. Apparent protein digestibility was similar among treatments, but lipid digestibility was significantly reduced in the SCI15 and SCI18 groups compared to the SCI12 group. The specific activities of trypsin, total alkaline protease and lipase were increased in fish fed the SCI15 diet (p < 0.05). The protein content in the fillet was significantly increased and the lipid content was decreased in the SCI12 and SCI18 groups compared to the other groups. No adverse effects on liver and intestinal histology were observed in the different groups. The results suggest that organic fishmeal trimmings can be successfully replaced by innovative SCIs based on microbial protein, yeast meal and algae, and that this SCI mixture could be a candidate for organic aqua feed for gilthead sea bream.

The growth of the aquaculture industry requires more sustainable and circular economy-driven aquafeed formulas. Thus, the goal of the present study was to assess in farmed gilthead sea bream (Sparus aurata L.) how different combinations of novel and conventional fish feed ingredients supported proper animal performance in terms of growth and physiological biomarkers of blood/liver/head kidney. A 77-day feeding trial was conducted with three experimental diets (PAP, with terrestrial processed animal protein from animal by-products; NOPAP, without processed animal protein from terrestrial animal by-products; MIX, a combination of alternative ingredients of PAP and NOPAP diets) and a commercial-type formulation (CTRL), and their effects on growth performance and markers of endocrine growth regulation, lipid metabolism, antioxidant defense and inflammatory condition were assessed at circulatory and tissue level (liver, head kidney). Growth performance was similar among all dietary treatments. However, fish fed the PAP diet displayed a lower feed conversion and protein efficiency, with intermediate values in MIX-fed fish. Such gradual variation in growth performance was supported by different biomarker signatures that delineated a lower risk of oxidation and inflammatory condition in NOPAP fish, in concurrence with an enhanced hepatic lipogenesis that did not represent a risk of lipoid liver degeneration.

Fish were kept for six weeks at three different initial stocking densities and water O2 concentrations (low-LD, 8.5 kg/m3 and 95–70% O2 saturation; medium-MD, 17 kg/m3 and 55–75% O2 saturation; high-HD, 25 kg/m3 and 60–45% O2 saturation), with water temperature increasing from 19 °C to 26–27 °C. The improvement in growth performance with the decrease in stocking density was related to changes in skin and intestinal mucosal microbiomes. Changes in microbiome composition were higher in skin, with an increased abundance of Alteromonas and Massilia in HD fish. However, these bacteria genera were mutually exclusive, and Alteromonas abundance was related to a reactive behavior and systemic growth regulation via the liver Gh/Igf system, while Massilia was correlated to a proactive behavior and a growth regulatory transition towards muscle rather than liver. At the intestinal level, microbial abundance showed an opposite trend for two bacteria taxa, rendering in a low abundance of Reyranella and a high abundance of Prauserella in HD fish. This trend was correlated with up-regulated host gene expression, affecting the immune response, epithelial cell turnover, and abiotic stress response. Most of the observed responses are adaptive in nature, and they would serve to infer new welfare indicators for increased stress resilience.

The study combined the use of biometric, behavioral, physiological and external tissue damage scoring systems to better understand how high stocking densities drive schooling behavior and other adaptive features during the finishing growing phase of farmed gilthead sea bream in the Western Mediterranean. Fish were grown at three different final stocking densities (LD, 8.5 kg/m3; MD, 17 kg/m3; HD, 25 kg/m3). Water oxygen concentration varied between 5 and 6 ppm in LD fish to 3-4 ppm in HD fish with the summer rise of water temperature from 19°C to 26°C (May-July). HD fish showed a reduction of feed intake and growth rates, but they also showed a reinforced social cohesion with a well-defined endogenous swimming activity rhythm with feeding time as a main synchronization factor. The monitored decrease of the breathing/swimming activity ratio by means of the AEFishBIT data-logger also indicated a decreased energy partitioning for growth in the HD environment with a limited oxygen availability. Plasma glucose and cortisol levels increased with the rise of stocking density, and the close association of glycaemia with the expression level of antioxidant enzymes (mn-sod, gpx4, prdx5) in liver and molecular chaperones (grp170, grp75) in skeletal muscle highlighted the involvement of glucose in redox processes via rerouting in the pentosephosphate-pathway. Other adaptive features included the depletion of oxidative metabolism that favored lipid storage rather than fatty acid oxidation to decrease the oxygen demand as last electron acceptor in the mitochondrial respiratory chain. This was coincident with the metabolic readjustment of the Gh/Igf endocrine-growth cascade that promoted the regulation of muscle growth at the local level rather than a systemic action via the liver Gh/Igf axis. Moreover, correlation analyses within HD fish displayed negative correlations of hepatic transcripts of igf1 and igf2 with the data-logger measurements of activity and respiration, whereas the opposite was found for muscle igf2, ghr1 and ghr2. This was indicative of a growth-regulatory transition that supported a proactive instead of a reactive behavior in HD fish, which was considered adaptive to preserve an active and synchronized feeding behavior with a minimized risk of oxidative stress and epidermal skin damage. [ABSTRACT FROM AUTHOR]

The Sirtuin (SIRT1-7) family comprises seven evolutionary-conserved enzymes that couple cellular NAD availability with health, nutrition and welfare status in vertebrates. This study re-annotated the sirt3/5 branch in the gilthead sea bream, revealing three paralogues of sirt3 (sirt3.1a/sirt3.1b/sirt3.2) and two of sirt5 (sirt5a/sirt5b) in this Perciform fish. The phylogeny and synteny analyses unveiled that the Sirt3.1/Sirt3.2 dichotomy was retained in teleosts and aquatic-living Sarcopterygian after early vertebrate 2R whole genome duplication (WGD). Additionally, only certain percomorphaceae and gilthead sea bream showed a conserved tandem-duplicated synteny block involving the mammalian-clustered sirt3.1 gene (psmd13-sirt3.1a/b-drd4-cdhr5-ctsd). Conversely, the expansion of the Sirt5 branch was shaped by the teleost-specific 3R WGD. As extensively reviewed in the literature, human-orthologues (sirt3.1/sirt5a) showed a high, conserved expression in skeletal muscle that increased as development advanced. However, recent sirt3.2 and sirt5b suffered an overall muscle transcriptional silencing across life, as well as an enhanced expression on immune-relevant tissues and gills. These findings fill gaps in the ontogeny and differentiation of Sirt genes in the environmentally adaptable gilthead sea bream, becoming a good starting point to advance towards a full understanding of its neo-functionalization. The mechanisms originating from these new paralogs also open new perspectives in the study of cellular energy sensing processes in vertebrates.

Aquaculture is the fastest-growing food production sector and nowadays provides more food than extractive fishing. Studies focused on the understanding of how teleost growth is regulated are essential to improve fish production. Cysteamine (CSH) is a novel feed additive that can improve growth through the modulation of the GH/IGF axis; however, the underlying mechanisms and the interaction between tissues are not well understood. This study aimed to investigate the effects of CSH inclusion in diets at 1.65 g/kg of feed for 9 weeks and 1.65 g/kg or 3.3 g/kg for 9 weeks more, on growth performance and the GH/IGF-1 axis in plasma, liver, stomach, and white muscle in gilthead sea bream (Sparus aurata) fingerlings (1.8 ± 0.03 g) and juveniles (14.46 ± 0.68 g). Additionally, the effects of CSH stimulation in primary cultured muscle cells for 4 days on cell viability and GH/IGF axis relative gene expression were evaluated. Results showed that CSH-1.65 improved growth performance by 16% and 26.7% after 9 and 18 weeks, respectively, while CSH-3.3 improved 32.3% after 18 weeks compared to control diet (0 g/kg). However, no significant differences were found between both experimental doses. CSH reduced the plasma levels of GH after 18 weeks and increased the IGF-1 ones after 9 and 18 weeks. Gene expression analysis revealed a significant upregulation of the ghr-1, different igf-1 splice variants, igf-2 and the downregulation of the igf-1ra and b, depending on the tissue and dose. Myocytes stimulated with 200 µM of CSH showed higher cell viability and mRNA levels of ghr1, igf-1b, igf-2 and igf-1rb compared to control (0 µM) in a similar way to white muscle. Overall, CSH improves growth and modulates the GH/IGF-1 axis in vivo and in vitro toward an anabolic status through different synergic ways, revealing CSH as a feasible candidate to be included in fish feed. [ABSTRACT FROM AUTHOR]

Simple Summary: Nowadays, aquaculture is the main source of fish for consumers, and its demand is constantly increasing. The diet of these fish requires protein for their growth, which is traditionally obtained from natural fish stocks. In recent years, efforts have been made to replace these feed ingredients with insect-derived meals, but it is necessary to investigate their impact on the growth and health status of the fish. In this study, two insect meals of Tenebrio molitor larvae reared in conventional substrates or substrates enriched with medicinal/aromatic plants (MAPs) were supplemented (10%) as fish meal replacements in the diets of gilthead seabream. After 12 weeks of experimental feeding, hematological and biochemical tests were conducted, revealing specific modulations in white blood cell and blood signal transduction patterns in the fish subjected to each experimental diet in relation to the new feed ingredients. This work assesses the dietary use of two insect meals of Tenebrio molitor (TM) larvae reared in conventional (TM-10) or MAP-enriched substrates (MAP-TM-10) as fish meal replacements (10%) in the diets of gilthead seabream (Sparus aurata). Fish (n = 4500; 207.19 ± 1.47 g) were divided into three groups with triplicates: control (fed conventional diet), TM-10, and MAP-TM-10 groups. The fish were reared in floating cages for 12 weeks and the dietary effects on white blood cell activation, heat shock proteins, MAPKs, and apoptosis of the fish were evaluated. The MAP-TM-10 group exhibited the highest eosinophilic induction. Phosphorylated levels of p38 MAPK, p44/42 MAPK, HSP70, and HSP90 increased in the TM-10 and MAP-TM-10 groups. In terms of apoptosis, Bax levels were lower in the TM groups compared to the control, and the MAP-TM-10 group showed even lower levels than the TM-10 group. Bcl-2 levels increased in the TM-10 group compared to the control, and further increased in the MAP-TM-10 group. The Bax/Bcl-2 ratio, an apoptosis indicator, decreased in the TM groups, with the MAP-TM-10 group showing a further decrease compared to TM-10. These findings suggest that insects' breeding substrate being enriched with MAPs modulated the effect of TM on cellular stress and apoptosis. [ABSTRACT FROM AUTHOR]

Gut microbiomes of fish species consist of thousands of bacterial taxa that interact among each other, their environment, and the host. These complex networks of interactions are regulated by a diverse range of factors, yet little is known about the hierarchy of these interactions. Here, we introduce SAMBA (Structure-Learning of Aquaculture Microbiomes using a Bayesian Approach), a computational tool that uses a unified Bayesian network approach to model the network structure of fish gut microbiomes and their interactions with biotic and abiotic variables associated with typical aquaculture systems. SAMBA accepts input data on microbial abundance from 16S rRNA amplicons as well as continuous and categorical information from distinct farming conditions. From this, SAMBA can create and train a network model scenario that can be used to (i) infer information of how specific farming conditions influence the diversity of the gut microbiome or pan-microbiome, and (ii) predict how the diversity and functional profile of that microbiome would change under other variable conditions. SAMBA also allows the user to visualize, manage, edit, and export the acyclic graph of the modelled network. Our study presents examples and test results of Bayesian network scenarios created by SAMBA using data from a microbial synthetic community, and the pan-microbiome of gilthead sea bream (Sparus aurata) in different feeding trials. It is worth noting that the usage of SAMBA is not limited to aquaculture systems as it can be used for modelling microbiome–host network relationships of any vertebrate organism, including humans, in any system and/or ecosystem. [ABSTRACT FROM AUTHOR]

The study combined the use of biometric, behavioral, physiological and external tissue damage scoring systems to better understand how high stocking densities drive schooling behavior and other adaptive features during the finishing growing phase of farmed gilthead sea bream in the Western Mediterranean. Fish were grown at three different final stocking densities (LD, 8.5 kg/m3; MD, 17 kg/m3; HD, 25 kg/m3). Water oxygen concentration varied between 5 and 6 ppm in LD fish to 3–4 ppm in HD fish with the summer rise of water temperature from 19°C to 26°C (May–July). HD fish showed a reduction of feed intake and growth rates, but they also showed a reinforced social cohesion with a well-defined endogenous swimming activity rhythm with feeding time as a main synchronization factor. The monitored decrease of the breathing/swimming activity ratio by means of the AEFishBIT data-logger also indicated a decreased energy partitioning for growth in the HD environment with a limited oxygen availability. Plasma glucose and cortisol levels increased with the rise of stocking density, and the close association of glycaemia with the expression level of antioxidant enzymes (mn-sod, gpx4, prdx5) in liver and molecular chaperones (grp170, grp75) in skeletal muscle highlighted the involvement of glucose in redox processes via rerouting in the pentose-phosphate-pathway. Other adaptive features included the depletion of oxidative metabolism that favored lipid storage rather than fatty acid oxidation to decrease the oxygen demand as last electron acceptor in the mitochondrial respiratory chain. This was coincident with the metabolic readjustment of the Gh/Igf endocrine-growth cascade that promoted the regulation of muscle growth at the local level rather than a systemic action via the liver Gh/Igf axis. Moreover, correlation analyses within HD fish displayed negative correlations of hepatic transcripts of igf1 and igf2 with the data-logger measurements of activity and respiration, whereas the opposite was found for muscle igf2, ghr1 and ghr2. This was indicative of a growth-regulatory transition that supported a proactive instead of a reactive behavior in HD fish, which was considered adaptive to preserve an active and synchronized feeding behavior with a minimized risk of oxidative stress and epidermal skin damage.

Mediterranean finfish aquaculture is mainly represented by the production of the gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) growing in marine cage farms. Despite the numerous benefits of fish farming, the ecological risk potentially caused by fish escapes to the wild populations is occasionally high. In the current study, an integrated review of fish escapes is presented regarding S. aurata and D. labrax escapes and their potential effect on the genetic composition of wild populations. The collected data from the literature are combined and discussed along with recorded escapes in a fish farm located in the Aegean Sea, Greece. According to these records, fish escapes present a generally stable rate, ranging between 0 and 2% in each escape event, which occur 5–8 times per year. Although for other farmed fish species worldwide, the ecological risk may be higher, this risk is probably lower in Mediterranean finfish populations, which are characterized by generally low levels of genetic differentiation. Nevertheless, the risk of genetic introgression still exists. Particularly in sea bream and sea bass farming, genetic structure and differentiation in wild populations seem to be unaffected for now. Nevertheless, suitable management measurements would be a useful strategy to avoid future negative effects of fish escapes. These strategies should be focused on further efforts towards recapture program development, reduced escapees' survival, and proper legislation. Furthermore, more data on escapees' survival percentage, their migration pathways, and the way these pathways relate to mortality, the type of escape event, and the season of release would be also valuable. [ABSTRACT FROM AUTHOR]

Routine monitoring of monogenean loads is a crucial step for infection management in aquaculture facilities. This analysis is usually performed from partial gill analyses and thus, knowledge of parasite distribution and size can be helpful to optimise diagnosis, estimate infection levels and improve management procedures. Gill location preferences and intraspecific size variations relative to parasite age, host factors and parasite abundance are herein determined for the monogenean Sparicotyle chrysophrii, one of the most challenging pathogens in gilthead sea bream aquaculture. Present findings on parasite location show that the life-history stages of S. chrysophrii have distinct location preferences. Analysis of intraspecific size variations of adult stages of S. chrysophrii revealed that the size of most morphological features of S. chrysophrii increased significantly with parasite age and host size. Positive and significant relationships between the size of the posteriormost clamp and host size pointed out the adaptation of the parasite to the gilthead sea bream size from the initial settlement. Host size also seems to restrict the development of parasites after maturity as the oldest specimens were exclusively found in mid-large fish (>18 cm). By contrast, no clear patterns were observed for the relationship between parasite size and location or abundance. Post-maturity size variations of S. chrysophrii should be considered for parasite identification and the clamp pair number should be fixed for accurate taxonomic diagnosis. Based on the site location of S. chrysophrii, the dorsal sections or the outermost holobranches would be suitable for adult detection while the analysis of the central and dorsal sections of the outermost holobranches may be a better option for finding most of the adult, juvenile or post-larval stages.

Aquaculture is the fastest-growing food production sector and nowadays provides more food than extractive fishing. Studies focused on the understanding of how teleost growth is regulated are essential to improve fish production. Cysteamine (CSH) is a novel feed additive that can improve growth through the modulation of the GH/IGF axis; however, the underlying mechanisms and the interaction between tissues are not well understood. This study aimed to investigate the effects of CSH inclusion in diets at 1.65 g/kg of feed for 9 weeks and 1.65 g/kg or 3.3 g/kg for 9 weeks more, on growth performance and the GH/IGF-1 axis in plasma, liver, stomach, and white muscle in gilthead sea bream (Sparus aurata) fingerlings (1.8 ± 0.03 g) and juveniles (14.46 ± 0.68 g). Additionally, the effects of CSH stimulation in primary cultured muscle cells for 4 days on cell viability and GH/IGF axis relative gene expression were evaluated. Results showed that CSH-1.65 improved growth performance by 16% and 26.7% after 9 and 18 weeks, respectively, while CSH-3.3 improved 32.3% after 18 weeks compared to control diet (0 g/kg). However, no significant differences were found between both experimental doses. CSH reduced the plasma levels of GH after 18 weeks and increased the IGF-1 ones after 9 and 18 weeks. Gene expression analysis revealed a significant upregulation of the ghr-1, different igf-1 splice variants, igf-2 and the downregulation of the igf-1ra and b, depending on the tissue and dose. Myocytes stimulated with 200 µM of CSH showed higher cell viability and mRNA levels of ghr1, igf-1b, igf-2 and igf-1rb compared to control (0 µM) in a similar way to white muscle. Overall, CSH improves growth and modulates the GH/IGF-1 axis in vivo and in vitro toward an anabolic status through different synergic ways, revealing CSH as a feasible candidate to be included in fish feed.

The possibility of simultaneous production of halophyte and euryhaline fish creates huge interest in both commercial aquaponics systems and in research. The aim of the present study was to investigate the effect of three different salinities (8, 14, and 20 ppt) on the growth performance and survival rate of sea bream (Sparus aurata) and rock samphire (Crithmum maritimum) in an experimental brackish aquaponic system. Furthermore, induction of heat shock proteins (Hsps) and phosphorylation of mitogen-activated protein kinases (MAPKs) were assessed through the sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot analysis. A total number of 234 sea bream individuals were divided into nine autonomous aquaponic systems. The experiment lasted 45 days. In total, 54 individuals of rock samphire were used and were distributed into groups of six individuals per hydroponic tank using the raft method. Water quality showed stable fluctuation throughout the experiment, strongly supporting fish and plant growth performance and survival in both treatments. The results show that better growth performance for both sea bream and rock samphire (height increase) was evident in salinity 8 ppt compared to salinities 14 ppt and 20 ppt. Minimal or mild histopathological alterations were detected in gills, midgut, and liver for all three salinity groups. Exposure to different salinities modified Hsp60 and MAPKs expression in a tissue- and time-specific manner. During exposure to 8 ppt, constant Hsp60 levels and phosphorylation of MAPKs at 15 days may indicate a prominent protective role in the gills. The results show that sea bream and rock samphire can be used in brackish aquaponics systems with satisfactory growth performances, thus allowing for a range of commercial applications generating interest in their production. [ABSTRACT FROM AUTHOR]

Feed conversion ratio (FCR) is an important trait to target in fish breeding programs, and the aim of the present study is to underline how the genetic improvement of FCR in gilthead sea bream (Sparus aurata) drives to changes in transcriptional and behavioural patterns. Groups of fish with high (FCR+) and low (FCR-) individual FCR were established at the juvenile stage (161–315 dph) by rearing isolated fish on a restricted ration. Fish were then grouped on the basis of their individual FCR and they grew up until behavioural monitoring and gene expression analyses were done at 420 dph. The AEFishBIT datalogger (externally attached to operculum) was used for simultaneous measurements of physical activity and ventilation rates. This allowed discrimination of FCR+ and FCR- groups according to their different behaviour and energy partitioning for growth and locomotor activity. Gene expression profiling of liver and white muscle was made using customized PCR-arrays of 44 and 29 genes, respectively. Up to 15 genes were differentially expressed in liver and muscle tissues highlighting a different metabolic scope of FCR+ and FCR- fish. Hepatic gene expression profile of FCR- fish displayed a lower lipogenic activity that was concurrent with a down-regulation of markers of mitochondrial activity and oxidative stress, as well as a reallocation of body fat depots with an enhanced flux of lipids towards skeletal muscle. Muscle gene expression profile of FCR- fish matched with stimulatory and inhibitory growth signals, and an activation of energy sensors and antioxidant defence as part of the operating mechanisms for a more efficient muscle growth. These new insights contribute to phenotype the genetically mediated differences in fish FCR thanks to the combination of transcriptomic and behavioural approaches that contribute to better understand the mechanisms involved in a reliable FCR improvement of farmed gilthead sea bream.

The immunomodulatory effect of different dietary arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) ratios was evaluated in gilthead sea bream juveniles after intraperitoneal injection (i.p.) with formalin‐killed Photobacterium damselae subsp. piscicida (Phdp). Fish were fed with four isoproteic (47% crude protein) and isolipidic (18% crude lipids) diets with the following long‐chain polyunsaturated fatty acids (LC‐PUFA) ratios: Diet A (2.0% ARA: 0.2% EPA: 0.1% DHA); Diet B (1.0% ARA: 0.4% EPA: 0.4% DHA); Diet C (0% ARA: 0.6% EPA: 0.6% DHA); Diet D (0% ARA: 0.3% EPA: 1.5% DHA). After being fed for 56 days with the experimental diets, fish from each dietary treatment were randomly selected and i.p. injected with 0.2 ml of killed Phdp (1 × 108 CFU ml−1) or phosphate‐buffered saline (control group). Four and twenty‐four hours (i.e., twice) after the i.p., the haematological profile, plasma humoral innate immune parameters, and the intestine expression of immune‐related genes were assessed. Results showed that fish fed diet D (high DHA content) had increased complement activity and higher intestinal expression of cyclooxygenase 2 (cox2) and interleukin 1β (il‐1β) at 4 and 24 hours after i.p., as well as increased intestinal tumour necrosis factor α (tnfα) expression at 4 hours. On the other hand, fish fed with diet A (high ARA content) showed higher plasma bactericidal activity against Phdp than fish fed with diet D. Overall, the results of this study suggest a positive modulatory effect of DHA in response to the pathogenic agent. [ABSTRACT FROM AUTHOR]

Parasitic copepods are common damaging ectoparasites of cultured marine fish that induce high mortalities in fish farms. The present study aimed to identify the cause of mass mortalities of cultured gilthead sea bream (Sparus aurata) as one of the highly valuable cultured marine fish species in Egypt. Parasitological examination demonstrated Ergasilus sieboldin (E. sieboldi) adult females of (1.3 ± 0.01 mm, n = 55) mean body length and (0.53 ± 0.04 mm) body width, lodged in the gill filaments of the forty examined fish with a pair of strong clawed antennae. The detected parasite has six segmented antennules and consists of cephalosome followed by four divided thoracic segments that narrow posteriorly, five pairs of swimming legs, genital segment, abdominal segments followed by furcal rami with unequal caudal setae and two egg sacs at the end of the body. The collected E. sieboldi were confirmed by molecular characterization and phylogenetic analysis based on 28S rDNA sequencing. The obtained sequence in this study was registered in the GenBank with (OM812074) accession number as a first sequence of E. sieboldi from Egypt. Oxidative stress biomarkers in the gills of the parasitized fish were evaluated to describe the host defense mechanisms against E. sieboldi infestation. The current study demonstrated decreasing in reduced glutathione (GSH) content and activity of the anti-oxidant enzyme catalase (CAT), as well as elevation in the level of malondialdehyde (MDA) due to exposure to oxidative damage that might have a role in the tissue damage and dysfunction. [ABSTRACT FROM AUTHOR]

Gut microbiomes of fish species consist of thousands of bacterial taxa that interact among each other, their environment, and the host. These complex networks of interactions are regulated by a diverse range of factors, yet little is known about the hierarchy of these interactions. Here, we introduce SAMBA (Structure-Learning of Aquaculture Microbiomes using a Bayesian Approach), a computational tool that uses a unified Bayesian network approach to model the network structure of fish gut microbiomes and their interactions with biotic and abiotic variables associated with typical aquaculture systems. SAMBA accepts input data on microbial abundance from 16S rRNA amplicons as well as continuous and categorical information from distinct farming conditions. From this, SAMBA can create and train a network model scenario that can be used to (i) infer information of how specific farming conditions influence the diversity of the gut microbiome or pan-microbiome, and (ii) predict how the diversity and functional profile of that microbiome would change under other variable conditions. SAMBA also allows the user to visualize, manage, edit, and export the acyclic graph of the modelled network. Our study presents examples and test results of Bayesian network scenarios created by SAMBA using data from a microbial synthetic community, and the pan-microbiome of gilthead sea bream (Sparus aurata) in different feeding trials. It is worth noting that the usage of SAMBA is not limited to aquaculture systems as it can be used for modelling microbiome–host network relationships of any vertebrate organism, including humans, in any system and/or ecosystem.

This work assesses the dietary use of two insect meals of Tenebrio molitor (TM) larvae reared in conventional (TM-10) or MAP-enriched substrates (MAP-TM-10) as fish meal replacements (10%) in the diets of gilthead seabream (Sparus aurata). Fish (n = 4500; 207.19 ± 1.47 g) were divided into three groups with triplicates: control (fed conventional diet), TM-10, and MAP-TM-10 groups. The fish were reared in floating cages for 12 weeks and the dietary effects on white blood cell activation, heat shock proteins, MAPKs, and apoptosis of the fish were evaluated. The MAP-TM-10 group exhibited the highest eosinophilic induction. Phosphorylated levels of p38 MAPK, p44/42 MAPK, HSP70, and HSP90 increased in the TM-10 and MAP-TM-10 groups. In terms of apoptosis, Bax levels were lower in the TM groups compared to the control, and the MAP-TM-10 group showed even lower levels than the TM-10 group. Bcl-2 levels increased in the TM-10 group compared to the control, and further increased in the MAP-TM-10 group. The Bax/Bcl-2 ratio, an apoptosis indicator, decreased in the TM groups, with the MAP-TM-10 group showing a further decrease compared to TM-10. These findings suggest that insects’ breeding substrate being enriched with MAPs modulated the effect of TM on cellular stress and apoptosis.

Mediterranean finfish aquaculture is mainly represented by the production of the gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) growing in marine cage farms. Despite the numerous benefits of fish farming, the ecological risk potentially caused by fish escapes to the wild populations is occasionally high. In the current study, an integrated review of fish escapes is presented regarding S. aurata and D. labrax escapes and their potential effect on the genetic composition of wild populations. The collected data from the literature are combined and discussed along with recorded escapes in a fish farm located in the Aegean Sea, Greece. According to these records, fish escapes present a generally stable rate, ranging between 0 and 2% in each escape event, which occur 5–8 times per year. Although for other farmed fish species worldwide, the ecological risk may be higher, this risk is probably lower in Mediterranean finfish populations, which are characterized by generally low levels of genetic differentiation. Nevertheless, the risk of genetic introgression still exists. Particularly in sea bream and sea bass farming, genetic structure and differentiation in wild populations seem to be unaffected for now. Nevertheless, suitable management measurements would be a useful strategy to avoid future negative effects of fish escapes. These strategies should be focused on further efforts towards recapture program development, reduced escapees’ survival, and proper legislation. Furthermore, more data on escapees’ survival percentage, their migration pathways, and the way these pathways relate to mortality, the type of escape event, and the season of release would be also valuable.

Viral nervous necrosis (VNN) is now endemic in the Mediterranean basin and the RGNNV genotype betanodavirus has caused frequent epidemics in European sea bass for a long time. Unexpected and increasing VNN epidemics have been reported in gilthead sea bream (GSB) farms in the last few years, from which the RGNNV/SJNNV genotype has been mostly isolated. The aim of this study was to perform a molecular characterization of the betanodavirus isolated from GSB (weighing 90–100 g) in a marine fish farm in the Aegean Sea and also, as an early warning exercise, to investigate the presence/absence of the virus in associated nearby farms (n:20) and in hatcheries (n:3). No virus was detected in any of the nearby farms or two hatcheries. However, in one hatchery, betanodavirus was detected in a 160‐day‐old GSB. The identified betanodavirus was genotyped as reassortant RGNNV/SJNNV and was phylogenetically related to the virus detected in the farm located in the Aegean sea. There have been multiple detections of the RGNNV genotype in Turkish coastal waters; however, the RGNNV/SJNNV genotype has been detected for the first time and it should be an early warning to focus attention on betanodaviruses in Turkish aquaculture. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the replacement of dietary protein sources like fishmeal (FM) and plant proteins (PP) by Brewer’s spent dry yeast (SDY) on the transcriptomic response (RNA-seq, NextSeq500 platform Illumina) in the liver, anterior-mid intestine, and head kidney in juveniles of gilthead sea bream (Sparus aurata). The inclusion of SDY at 30% in the experimental diet (40% crude protein, 16% crude lipid) resulted in a reduction in FM (10%) and PP (31.4%) contents. Using RNA-seq, a total of 19.4 million raw reads per library were obtained, from whose 99.8% of the sequenced data were retained. The alignment efficiency of uniquely mapped reads was 90.3, 89.5, and 89.8% for head kidney, liver, and anterior-mid intestine, respectively. In total, 218 differentially expressed genes (DEGs) were identified among all tissues, out of which, 141 were up- and 77 down-regluated. The enrichment analysis of DEGs revealed that SDY had a modulatory effect on several processes related to host’s immunity, oxygen’s carrier capacity, steroidogenesis, metabolism, and digestion. It is of special relevance the immunomodulatory effects of the tested ingredient as data from RNA-seq showed from the three target tissues analyzed. These results indicated that this ingredient in addition to being considered as a sustainable raw material for replacing conventional protein sources in aquafeeds may also be considered as a functional ingredient due to its content in β-glucans. The overall results of this study coupled with previous nutritional studies on this ingredient indicated the suitability of brewery’s by-products like SDY in aquafeeds for carnivorous species like gilthead seabream, as well as supporting a circular bioeconomy model that reuses, recovers, and recycles resources instead of producing wastes.

The possibility of simultaneous production of halophyte and euryhaline fish creates huge interest in both commercial aquaponics systems and in research. The aim of the present study was to investigate the effect of three different salinities (8, 14, and 20 ppt) on the growth performance and survival rate of sea bream (Sparus aurata) and rock samphire (Crithmum maritimum) in an experimental brackish aquaponic system. Furthermore, induction of heat shock proteins (Hsps) and phosphorylation of mitogen-activated protein kinases (MAPKs) were assessed through the sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot analysis. A total number of 234 sea bream individuals were divided into nine autonomous aquaponic systems. The experiment lasted 45 days. In total, 54 individuals of rock samphire were used and were distributed into groups of six individuals per hydroponic tank using the raft method. Water quality showed stable fluctuation throughout the experiment, strongly supporting fish and plant growth performance and survival in both treatments. The results show that better growth performance for both sea bream and rock samphire (height increase) was evident in salinity 8 ppt compared to salinities 14 ppt and 20 ppt. Minimal or mild histopathological alterations were detected in gills, midgut, and liver for all three salinity groups. Exposure to different salinities modified Hsp60 and MAPKs expression in a tissue- and time-specific manner. During exposure to 8 ppt, constant Hsp60 levels and phosphorylation of MAPKs at 15 days may indicate a prominent protective role in the gills. The results show that sea bream and rock samphire can be used in brackish aquaponics systems with satisfactory growth performances, thus allowing for a range of commercial applications generating interest in their production.

The objective of the present study was the evaluation of the effect of slurry ice, as an alternative cooling medium during harvesting and transportation, on the quality parameters (e.g., microbiological stability, sensory attributes, physicochemical changes) and shelf life of fish. The effect of seasonal variability of seawater temperature on fish preservation using the tested cooling media was also investigated. Gilthead sea bream (Sparus aurata) was slaughtered and transported in different mixtures of conventional flake ice and slurry ice for 24 h. Three mixtures of ice were tested as T: slaughtered in flake ice and transported in flake ice (control), TC: slaughtered in slurry ice and transported in flake ice, T50: slaughtered and transported in slurry ice 50%–flake ice 50%. Samples were subsequently stored isothermally at 0 °C for shelf-life evaluation. Three independent experiments were performed at three different periods, i.e., January, April, and September, referring to a sea water temperature range of 13.3–26.8 °C. Higher sea water temperatures at catching led to lower microbial growth rates and proteolytic enzyme activities and longer shelf life of refrigerated whole fish. The partial replacement of conventional flake ice with slurry ice improved the quality and extended the shelf life of fish at 0 °C by 2–7 days. The results of the study support that the use of slurry ice may enable better quality maintenance and significant shelf-life extension of whole gilthead sea bream. [ABSTRACT FROM AUTHOR]

However, fish species of major importance in the Mediterranean mariculture, namely gilthead sea bream ( I Sparus aurata i ) and red sea bream ( I Pagrus major i ), also suffer from gaping, and consequently, economic losses burden their industry. Keywords: assessors; gapping; Gilthead sea bream; image analysis; red sea bream; scale EN assessors gapping Gilthead sea bream image analysis red sea bream scale 689 693 5 01/07/22 20220201 NES 220201 A number of commercially important farmed fish species are marketed as fillets, primarily to satisfy consumer demands. These indicate that the proposed method for evaluating gaping in Sparidae species is easy to apply in practice, allowing the scoring procedure to be accessible to all commercial gilthead sea bream and/or red sea bream farms. [Extracted from the article]

The age and growth of gilthead sea bream (Sparus aurata Linnaeus, 1758) were studied in the present study. A total of 126 specimens were collected from commercial fishmongers during the period between January 2015 and December 2015 from the northern Aegean coasts of Turkey. Fork length and the total weight of aged specimens ranged from 29.5 to 48.0 cm and from 425.00 to 2100.00 g, with a mean of 38.5 cm and 101.23 g, respectively. The length-weight relationship was estimated as W = 0.0053FL3.03 (R² = 0.95). The von Bertalanffy growth equations were computed as L∞ = 52.8 cm, k = 0.29 year-1, t0 = -1.25 year for all samples. The growth performance index (Φ') was found as 2.91. There is no study on the biology of the species for the northern Aegean Sea. Therefore, this study provides valuable information for the species in this area. [ABSTRACT FROM AUTHOR]

Abstract Background In the animal production sector, enteritis is responsible for serious economic losses, and intestinal parasitism is a major stress factor leading to malnutrition and lowered performance and animal production efficiency. The effect of enteric parasites on the gut function of teleost fish, which represent the most ancient bony vertebrates, is far from being understood. The intestinal myxozoan parasite Enteromyxum leei dwells between gut epithelial cells and causes severe enteritis in gilthead sea bream (Sparus aurata), anorexia, cachexia, growth impairment, reduced marketability and increased mortality. Methods This study aimed to outline the gut failure in this fish-parasite model using a multifaceted approach and to find and validate non-lethal serum markers of gut barrier dysfunction. Intestinal integrity was studied in parasitized and non-parasitized fish by immunohistochemistry with specific markers for cellular adhesion (E-cadherin) and tight junctions (Tjp1 and Cldn3) and by functional studies of permeability (oral administration of FITC-dextran) and electrophysiology (Ussing chambers). Serum samples from parasitized and non-parasitized fish were analyzed using non-targeted metabolomics and some significantly altered metabolites were selected to be validated using commercial kits. Results The immunodetection of Tjp1 and Cldn3 was significantly lower in the intestine of parasitized fish, while no strong differences were found in E-cadherin. Parasitized fish showed a significant increase in paracellular uptake measured by FITC-dextran detection in serum. Electrophysiology showed a decrease in transepithelial resistance in infected animals, which showed a diarrheic profile. Serum metabolomics revealed 3702 ions, from which the differential expression of 20 identified compounds significantly separated control from infected groups in multivariate analyses. Of these compounds, serum inosine (decreased) and creatine (increased) were identified as relevant and validated with commercial kits. Conclusions The results demonstrate the disruption of tight junctions and the loss of gut barrier function, a metabolomic profile of absorption dysfunction and anorexia, which further outline the pathophysiological effects of E. leei.

The present research tested the effects of dietary nisin-producing Lactococcus lactis on growth performance, feed utilization, intestinal morphology, transcriptional response, and microbiota in gilthead sea bream (Sparus aurata). A feeding trial was conducted with fish weighting 70–90 g. Fish were tagged with passive, integrated transponders and distributed in nine 500 L tanks with 40 fish each. Fish were fed for 12 weeks with either a control (diet A) or experimental diets (diets B and C) in triplicate (3 tanks/diet). Extruded pellets of diets B and C were supplemented with a low (2 × 109 CFU/kg) and a high (5 × 109 CFU/kg) dose of probiotic, respectively. No significant differences were found between groups for the feed conversion ratio or specific growth rates. However, the final body weight of fish fed diet C was significantly higher than the control group with intermediate values for fish fed diet B. Histological analysis conducted using a semi-quantitative scoring system showed that probiotic did not alter the morphology of the intestine and did not trigger inflammation. With regard to the transcriptomic response, a customized PCR array layout was designed to simultaneously profile a panel of 44 selected genes. Significant differences in the expression of key genes involved in innate and acquired immunity were detected between fish fed probiotic and control diets. To analyze the microbiota associated to the feeds and the gut autochthonous microbial communities, we used the Illumina MiSeq platform for sequencing the 16S rRNA gene and a metagenomics pipeline based on VSEARCH and RDP databases. The analysis of gut microbiota revealed a lack of colonization of the probiotic in the host’s intestinal mucosa. However, probiotic did modulate the fish gut microbiota, confirming that colonization is not always necessary to induce host modification. In fact, diets B and C were enriched with Actinomycetales, as compared to diet A, which instead showed a higher percentage of Pseudomonas, Sphyngomonas, and Lactobacillus genera. These results were confirmed by the clear separation of gut bacterial community of fish fed with the probiotic from the bacterial community of control fish group in the beta-diversity and PLS-DA (supervised partial least-squares discriminant analysis) analyses.

This experimental studies investigated the protective efficiencies and the potential immune mechanisms of vibrio monovalent and polyvalent autogenous formalin-inactivated whole-cell bacterins (FKC) in Gilthead sea bream (Sparus aurata) cultured in Egypt. Two months post-vaccination, the relative percentage survival (RPS) was estimated after challenge with the vaccine's homologues pathogenic strains. The survival values were 100% and 83.3% in groups immunized with monovalent V. alginolyticus or V. parahaemolyticus FKC bacterins, respectively. On the other hand, survival values were 91.75% and 75% in fish groups subjected to polyvalent (V. parahaemolyticus O11: K40 & V. alginolyticus) and (V. parahaemolyticus O3: K6 & V. alginolyticus) FKC bacterins, respectively. Overall, the tested vaccine preparations were significantly increased (P < 0.05) the agglutination antibody titer, phagocytic activity, respiratory burst activity, when compared to the non-immunized control group. The current results conclude that, autogenous Vibrio vaccines provoked a promising protection against vibriosis in Gilthead sea bream cultured in Egypt, it was superior in monovalent FKC V. alginolyticus vaccine and polyvalent FKC of V. parahaemolyticus O11: K40 with V. alginolyticus vaccine that could be useful means of prevention and control of vibriosis. • Autogenous formalin killed bacterins against V. alginolyticus and V. parahaemolyticus were experimented. • The RPS values of Gilthead sea bream vaccinated with monovalent V. alginolyticus or V. parahaemolyticus FKC bacterins, were 100% & 83.3%, respectively. • The RPS values of Gilthead sea bream vaccinated with polyvalent V. parahaemolyticus O11: K40 & V. alginolyticus and V. parahaemolyticus O3: K6 & V. alginolyticus FKC bacterins were 91.75% & 75%, respectively. • The monovalent and polyvalent vibrio FKC could stimulate innate and adaptive immune responses in Gilthead sea bream. [ABSTRACT FROM AUTHOR]

The effects of dietary Hermetia illucens (HI) larvae meal on growth, plasma biochemistry and gut microbiota was tested in gilthead sea bream. Four isonitrogenous and isolipidic extruded diets (50% protein; 14% lipid) with different levels of HI larva meal (0% CTRL, 5% HI5, 10% HI10, and 15% HI15) in partial substitution to fish meal (FM) were administered to triplicate fish groups over 113 days. Diets were designed to partially replace FM, using FM level for practical application. No significant differences (p > 0.05) were observed in terms of final body weight, specific growth rate (SGR), feed intake (FI), feed conversion rate (FCR) as well as feed efficiency parameters such as protein efficiency ratio (PER), gross protein efficiency (GPE), gross lipid efficiency (GLE). At the end of the trial there were not significant differences on growth, feed intake, feed conversion rate and protein efficiency. Among over 20 plasma parameters analyzed, HI inclusion level reduced iron (Fe), potassium (K), creatinine (CREA), aspartate aminotransferase (AST), alanine amino transferase (ALT), creatine kinase (CK), alkaline phosphatase (ALP), lactate dehydrogenase (LDH). The reduction of AST, ALT and ALP might suggest a potential beneficial role of HI for liver integrity and functionality. Concerning gut microbiome (GM) layout, HI was able to induce a shift in the GM structure at any inclusion level considered compared to the control diet increasing the abundance of Bacillaceae (mainly Bacillus and Oceanobacillus) and Paenibacillaceae (Paenibacillus). Taxa that can be involved in chitin degradation and has been recently recognized as novel probiotics for aquaculture. In conclusion, the results of feed intake, growth, feed utilization and plasma biochemistry indicate that HI larvae meal can be successfully incorporated up to 15% in practical aquafeed diets to partially replace FM without any negative effects on growth and feed efficiency. Beyond being a valid alternative protein source for fish meal replacement in this species, it displays gut health functional properties already at low inclusion level. • Partial replacement of FM with HI larvae meal did not affect growth and feed utilization. • HI was able to induce a shift in the GM structure at any inclusion level. • HI increased the abundance of Bacillus and Paenibacillus. [ABSTRACT FROM AUTHOR]

Genetic selection and novel raw materials for aquafeeds are current key tools in the ongoing effort to increase the productivity, efficiency, and sustainability of the aquaculture sector. Selective breeding could also improve the utilization of novel dietary formulations with emergent ingredients. Gilthead sea bream juveniles, either coming from a selective breeding program based on growth traits, or a non-selected population, were nutritionally challenged with two novel dietary formulations that were compared with a Control diet based on 15% FM and 6% FO dietary commercial levels for this species. The novel formulations included an insect meal diet (INS) at 5% of the diet to replace 33.3% of the dietary FM, or a single-cell protein diet (SCP) at 10% of the diet and to replace 66.7% of the dietary FM. Fish oil was also totally replaced in these diets by a blend of poultry oil and Veramaris algal oil. Better growth and feed utilization of the selected genotype compared to non-selected fish was observed, at any of the diets assayed. INS and SCP novel diets reduced general performance of fish by reducing feed intake. However, selected fish fed novel diets showed very similar growth and lower feed conversion ratio compared with non-selected fish fed a control diet. The novel formulations increased n-3 LC-PUFA in fish tissues, particularly DHA, irrespective of the genotype, as a result of the dietary inclusion of the DHA-rich microalgal oil. Neither genetic selection nor the use of novel raw materials affected fillet proximate composition and consequently, sea bream fillet quality in terms of texture and sensorial perception of consumers. Overall, the results reaffirm the positive effects of selective breeding programs in improving sea bream key productive indicators, as well as support the use of novel dietary formulations, using insect meal from H. illucens, single-cell protein from M. capsulatus as partial replacers of FM in diets for gilthead sea bream (33 and 66% of replacement, respectively), and a blend of DHA-rich microalgal and poultry oils as total replacer of FO. • Selected fish showed better growth and feed utilization compared with non-selected fish. • Selected fish fed novel diets showed similar growth and lower FCR compared with non-selected fish fed FM based diet. • Selected fish are more able to utilize novel diets. • Successful concomitant replacement of FM and FO by insect and single cell proteins and microalgae oil, respectively. [ABSTRACT FROM AUTHOR]

In this study, a disease case caused with 15% mortality on gilthead sea bream (Sparus aurata) which was cultured in the Antalya Bay in the Mediterranean coast of Turkey was investigated in July 2015. Lethargy, loss of equilibrium, petechae on the operculums and the dorsal part of the body, pillar of the gills were recorded in the diseased fish. Internally, ascites, splenomegaly and hemorrhages on the intestinal tissue and muscle were observed. Occurrence of parasite was not detected. According to the results of phenotypical test and 16S rDNA sequencing analysis, the isolated bacterial species was identified as Staphylococcus hominis. Histopathologically, hyperplasia of primary lamellae, lamellar telangiectasia, edema and hemorrhages on the gill arch, numerous melanomacrophage centers (MMCs) in the spleen tissue, vacuoler degeneration, necrose and hemorrhages in the liver, multifocal necrosis, and numerous MMC in the kidney were determined and hemorrhages in the tunica propria region of the intestine were observed. It was determined that he isolates showed different susceptibility against antimicrobial agents.

The present study evaluated, in an 18-month gilthead sea bream trial, the time course effects of genetics on individual size variation and growth compensation processes in families selected by heritable growth in the PROGENSA® breeding program. Families categorized as fast, intermediate, and slow growing had different growth trajectories with a more continuous growth in fast growth families. This feature was coincident with a reduced size variation at the beginning of the trial that clustered together the half-sib families sharing the same father. Regression analysis evidenced that the magnitude of compensatory growth was proportional to the initial size variation with no rescaling of families at this stage. By contrast, the finishing growth depensation process can mask, at least partially, the previous size convergence. This reflects the different contribution across the production cycle of genetics in growth. How early-life experiences affect growth compensation at juvenile stages was also evaluated in a separate cohort, and intriguingly, a first mild-hypoxia pulse at 60–81 days post-hatching (dph) increased survival rates by 10%, preventing growth impairment when fish were exposed to a second hypoxia episode (112–127 dph). The early hypoxia experience did not have a negative impact on growth compensatory processes at juvenile stages. By contrast, a diminished capacity for growth compensation was found with repeated or late hypoxia experiences. All this reinforces the use of size variation as a main criterion for improving intensive fish farming and selective breeding. [ABSTRACT FROM AUTHOR]

The objective of the present study was the evaluation of the effect of slurry ice, as an alternative cooling medium during harvesting and transportation, on the quality parameters (e.g., microbiological stability, sensory attributes, physicochemical changes) and shelf life of fish. The effect of seasonal variability of seawater temperature on fish preservation using the tested cooling media was also investigated. Gilthead sea bream (Sparus aurata) was slaughtered and transported in different mixtures of conventional flake ice and slurry ice for 24 h. Three mixtures of ice were tested as T: slaughtered in flake ice and transported in flake ice (control), TC: slaughtered in slurry ice and transported in flake ice, T50: slaughtered and transported in slurry ice 50%–flake ice 50%. Samples were subsequently stored isothermally at 0 °C for shelf-life evaluation. Three independent experiments were performed at three different periods, i.e., January, April, and September, referring to a sea water temperature range of 13.3–26.8 °C. Higher sea water temperatures at catching led to lower microbial growth rates and proteolytic enzyme activities and longer shelf life of refrigerated whole fish. The partial replacement of conventional flake ice with slurry ice improved the quality and extended the shelf life of fish at 0 °C by 2–7 days. The results of the study support that the use of slurry ice may enable better quality maintenance and significant shelf-life extension of whole gilthead sea bream.

Long non-coding RNAs (lncRNAs) are an emerging group of ncRNAs that can modulate gene expression at the transcriptional or translational levels. In the present work, previously published transcriptomic data were used to identify lncRNAs expressed in gilthead sea bream skeletal muscle, and their transcription levels were studied under different physiological conditions. Two hundred and ninety lncRNAs were identified and, based on transcriptomic differences between juveniles and adults, a total of seven lncRNAs showed potential to be important for muscle development. Our data suggest that the downregulation of most of the studied lncRNAs might be linked to increased myoblast proliferation, while their upregulation might be necessary for differentiation. However, with these data, as it is not possible to propose a formal mechanism to explain their effect, bioinformatic analysis suggests two possible mechanisms. First, the lncRNAs may act as sponges of myoblast proliferation inducers microRNAs (miRNAs) such as miR-206, miR-208, and miR-133 (binding energy MEF < −25.0 kcal). Secondly, lncRNA20194 had a strong predicted interaction towards the myod1 mRNA (ndG = −0.17) that, based on the positive correlation between the two genes, might promote its function. Our study represents the first characterization of lncRNAs in gilthead sea bream fast skeletal muscle and provides evidence regarding their involvement in muscle development.

The aquaculture sector has experienced rapid and important growth with the subsequent increase of feeding and nutritional issues for sustaining this activity, mainly related to the use of high quality, safe and environmentally friendly feed ingredients. The use of additives in aquafeeds has proven to be a suitable option to improve different productive indicators in farmed fish. In the present study, the effect of adding the GHRP-6 peptide, a ghrelin analog, to a commercial diet of gilthead sea bream (Sparus aurata) was studied at two proportions (100 or 500 μg/kg of feed). Both experimental diets show an increase in growth performance, as well as in feed efficiency after 97 days of experiment. The lower inclusion of GHRP-6 (100 μg/kg) results in a better aerobic metabolism, while the higher inclusion significantly increased plasma GH levels in agreement with the GH secretagogue effects of ghrelin. Similar growth outcome and differences between GHRP-6 levels in aerobic metabolism and GH stimulation suggest that improvements in culture performance by this peptide may occur through different mechanisms. Taken together, this compound can be considered as a viable dietary supplement for increasing production efficiency of sea bream aquaculture, although a better understanding of its dose-specific effects is still required.

Camelina and chia oils are among the vegetable oils (VOs) with high content of α‐linolenic acid (ALA) and a combination of antioxidants, giving them nutritional advantage over other VOs used in aquafeeds. The present study evaluated the effects of dietary substitution of fish oil with oils from camelina or chia on the growth performance, fatty acid (FA) composition, gene expression and blood haematology in gilthead sea bream after a 90‐day feeding trial. Five isoproteic and isolipidic diets were formulated in which fish oil was 100% (camelina oil, CSO diet; and chia oil, CO diet) or 60% (MIX1 and MIX2 diets containing camelina and chia oils, respectively) replaced with camelina or chia oils. Growth performance and FA profiles of fish were significantly affected by the dietary treatments (p <.05). Contents of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (ARA) decreased, whereas n‐3 polyunsaturated fatty acid (PUFA) and n‐3/n‐6 ratio increased in fish fed diets containing oils from camelina or chia. An up‐regulation in the expression of genes involved in PUFA metabolism and the subsequent in vivo bioconversion of precursor FAs into highly unsaturated fatty acid (HUFA, C ≥ 20 and n ≥ 3) were recorded in fish fed VO‐based diets. Red blood cells (RBC), white blood cells (WBC), haemoglobin and haematocrit did not differ among fish fed the experimental diets. Our overall results suggested that replacement of fish oil with camelina or chia oil did not adversely affect growth performance in gilthead sea bream, except for those fed CSO diet. Our results also demonstrate that fatty acid profile of fish can be modified by the dietary inclusion level of camelina or chia oils. [ABSTRACT FROM AUTHOR]

In previous studies, combined inclusion of Zn, Mn and Se in early weaning diets improved larval growth, but suggested a potential toxicity by one of these elements. The present study aimed to determine the effect of the single inclusion of Zn, Mn, Se or Cu, their combination (Control+) or their absence (Control−) on larval diets. At the end of the trial, survival was significantly (p <.05) lowest in fish fed C+ diet (17.16 ± 7% mean ± SD), followed by that of larvae fed Mn diet (21.91 ± 7%). The highest survival was obtained by Cu diet (35.27 ± 15%), followed by C− diet (34.58 ± 9%). Cu and Se supplementation significantly improved total length and body weight, in comparison with the C− fish. On the contrary, fish fed Mn and C+ showed the lowest growth. Supplementation with Zn or Cu significantly increased CuZnsod, whereas gpx was significantly upregulated in fish fed Se and C+ diets. ARA/EPA level was significantly highest and DHA/EPA lowest in larvae fed the Cu diet in fish fed C+ diet. The results pointed out the importance of supplementation with Cu, as well as Se and Zn, on early weaning diets for gilthead sea bream, and the potential toxic effect of Mn. [ABSTRACT FROM AUTHOR]