Insights into red sea bream iridovirus pathogenesis: Unveiling host-pathogen interactions using membrane yeast two-hybrid and molecular dynamics.

Effect of replacing fish meal with stalked sea squirt (Styela clava) tunic waste on growth performance, health status, and skin pigmentation in juvenile red sea bream (Pagrus major)

Genomic prediction has been increasingly applied in aquaculture selective breeding; however, systematic evaluations of prediction accuracy across multiple aquaculture species and analytical methods under a unified and comparable framework remain limited. In this study, we conducted a comprehensive comparative assessment of genomic prediction performance across four representative aquaculture species, including Atlantic salmon (Salmo salar), gilthead sea bream (Sparus aurata), common carp (Cyprinus carpio), and rainbow trout (Oncorhynchus mykiss), using ten genomic prediction models including GBLUP, Bayesian and machine learning methods. Prediction accuracy varied widely among species and models, ranging from 0.49 to 0.85, and was strongly associated with trait heritability. High-heritability traits consistently achieved higher prediction accuracies, with rainbow trout and common carp exhibiting the best overall performance (0.75–0.83 and 0.73–0.85, respectively), whereas Atlantic salmon and gilthead sea bream showed lower and more variable accuracies (0.49–0.61 and 0.49–0.66). No single model performed optimally across all species. Machine learning-based approaches achieved the highest prediction accuracy in specific cases but exhibited pronounced species-dependent variability, while GBLUP provided stable and well-calibrated predictions with consistently low bias. Incremental SNP feature selection further improved prediction accuracy by 2.8–4.2% in three species using only 0.54–9.64% of the available markers, whereas no improvement was observed for a low-heritability trait. These results show that genomic prediction performance is highly context-dependent and underscores the importance of jointly considering trait genetic architecture, population characteristics, model choice, and marker selection when optimizing genomic selection strategies in aquaculture breeding programs.

Aquaculture shapes antibiotic resistance in Mediterranean gilthead sea bream farming: From hatcheries to offshore cages

Dietary Paecilomyces variotii single-cell protein supports growth and intestinal health in gilthead sea bream

In fish gut microbiome studies, there are no standardized protocols regarding sampling region or post-feeding time, nor clear consensus on whether analyses should target resident (autochthonous) or transient (allochthonous) bacteria. This study examined the dynamics and interactions of both microbial communities in the anterior and posterior intestine of farmed gilthead sea bream and evaluated the resident microbiome at 24 and 48 h post-feeding. Microbial DNA was sequenced using the Oxford Nanopore Technology platform. Data were analyzed through statistical and discriminant approaches, as well as a Bayesian network framework to assess bacterial interactions. Transient communities showed higher richness and diversity, regardless of intestinal section, suggesting a more specialized and stable microbial environment in the mucus layer. The two communities differed markedly in structure and composition. Variations associated with intestinal region were less pronounced, particularly for autochthonous bacteria, and post-feeding fluctuations in the resident microbiome were minimal. Functionally, results indicated relevant synergies between communities. Protein metabolism pathways were enriched in autochthonous bacteria, whereas allochthonous microorganisms contributed mainly to bile acid and carbohydrate metabolism. Overall, resident and transient bacteria constitute distinct communities in the gut of gilthead sea bream, with numerous genera present in both but most being differentially represented and interconnected.

ABSTRACT Megalocytivirus pagrus 1 is a major viral pathogen that causes high mortality and economic losses in aquaculture worldwide. Although PCR‐based diagnostics are highly sensitive and specific, their equipment dependence and long assay times limit field applicability. In this study, a digital multienzyme isothermal rapid amplification with exonuclease probe (digital MIRA‐EXO) assay was developed and validated for rapid and specific detection of red sea bream iridovirus (RSIV), infectious spleen and kidney necrosis virus (ISKNV), and turbot reddish body iridovirus (TRBIV). The digital MIRA‐EXO assay specifically identified Megalocytivirus pagrus 1 without cross‐reactivity with non‐target samples, including four fish cell lines and 13 different fish pathogens. Analytical sensitivity, expressed as 95% limit of detection, ranged from 146.87 to 201.6 copies/μL across the three viruses. Diagnostic performance evaluation of 180 fish samples showed high sensitivity (92.22%), specificity (100%), and overall accuracy (96.11%), with an area under the receiver operating characteristic (ROC) curve of 0.971. Substantial agreement with reference assays was observed for experimentally infected (κ = 0.786) and field samples (κ = 0.792), and between column‐based and rapid DNA extraction methods (κ = 0.783). Overall, the digital MIRA‐EXO assay provides a rapid, accurate, and field‐deployable diagnostic tool for Megalocytivirus pagrus 1 detection.

Red sea bream (Pagrus major) aquaculture represents one of the most economically important marine aquaculture industries in Japan and East Asia. However, viral diseases, particularly those caused by red sea bream iridovirus (RSIV), pose a serious threat to aquaculture production in this region. In this study, we applied high-hydrostatic-pressure (HHP) refolding technology to develop a recombinant vaccine targeting the RSIV major capsid protein (MCP). The recombinant MCP (RSIV-rMCP) expressed in Escherichia coli was insoluble; however, HHP treatment under alkaline (pH 10) conditions in the presence of arginine successfully solubilised the protein while preserving its structural integrity. The solubilised protein (HHP–RSIV-rMCP) induced strong RSIV-specific IgM responses and enhanced disease resistance in red sea bream. In contrast, sera from fish immunised with a commercial formalin-inactivated vaccine exhibited minimal reactivity to HHP–RSIV-rMCP but reacted significantly to formalin-treated HHP–RSIV-rMCP. These results indicate that the HHP–RSIV-rMCP vaccine induces conformation-specific IgM antibodies and that structural preservation is crucial for maintaining antigenicity. Collectively, our findings demonstrate that HHP refolding technology is an effective strategy for preparing structurally preserved antigens.

This study investigated the effectiveness of basil (Ocimum basilicum L.) extract obtained by hydrodistillation (EO) and lipid extract (LE) obtained via supercritical fluid extraction in preserving the quality of ground fish patties during refrigerated storage. Gilthead sea bream (Sparus aurata) patties were formulated with varying concentrations of EO and LE and evaluated over three days at 4 °C. The chemical composition of the extracts, analyzed by GC-MS, revealed linalool, eucalyptol, and τ-cadinol as dominant bioactive compounds, with EO richer in monoterpenes and LE in sesquiterpenes. Both extracts significantly reduced lipid oxidation (TBARS) and protein oxidation (thiol content), with the strongest antioxidative effect observed in patties containing 0.150 µL/g of LE. Color parameters (L*, a*, b*, ΔE) were moderately influenced, without adverse effects on product appearance. pH and water activity values remained stable across treatments, while total volatile basic nitrogen (TVB-N) levels confirmed delayed spoilage in extract-treated patties. Results highlight the potential of basil extracts, especially LE obtained by SFE, as effective natural antioxidants in fish-based products. These findings support the development of clean-label, health-promoting products tailored to individual needs, and show that ground fish porridge has promise as a viable material for the production of innovative seafood products.

Objective Pharmaceuticals are emerging pollutants that have received great interest because of their discharge into aquatic ecosystems through wastewater worldwide. However, studies on the effects of these pollutants on aquatic animals are limited. Dexamethasone is a potent synthetic glucocorticoid with anti-inflammatory and immunosuppressive effects. Understanding how this medicine affects the immune response of fish was the topic of interest in the present study. The present study investigated the effects of dexamethasone on the innate immune response of the spleen and head kidney cells of Acanthopagrus arabicus in vitro. Materials Cultured spleen and head kidney cells were exposed to dexamethasone with various concentrations in vitro. After 48 h, the toxic effects of dexamethasone on innate immune factors were assessed. Results Based on the results, the sensitivity of cultured spleen and head kidney cells to dexamethasone increased in a concentration-dependent manner. Dexamethasone significantly decreased the number of IgM-secreting cells and IgM secretion. It also significantly reduced the C3 content of the cultivated cells but did not significantly alter the C4 and ACH50 contents or lysozyme activity of the cultivated cells. Furthermore, dexamethasone significantly suppressed respiratory burst activity and nitric oxide production in the spleen and head kidney cells. Conclusions In conclusion, the immunosuppressive effect of dexamethasone was due mainly to its suppressive effects on IgM-secreting cells and IgM production, C3 content, burst activity and nitric oxide production in the spleen and head kidney cells.

Upcycling aquaculture side streams: oil recovery from processed sea bass and sea bream.

Trophic transfer of nanoplastics reduces larval survival of marine fish more than waterborne exposure.

Effect of fish meal replacement with guar meal concentrate on growth, food conversion, digestive enzyme activity and intestinal histology of Gilthead sea bream (Spars aurata)

Due to stagnant production and high cost of fish meal (FM), feed nutritionists are seeking reliable and affordable alternatives. However, low‐FM diets often result in poor palatability, reduced feed consumption (FC), and impaired growth. This study investigates the effects of replacing FM with plant proteins in diets with or without jack mackerel meal (JMM) inclusion on the growth performance of juvenile red sea bream (P. major). A three‐way {2 FM replacement sources (corn gluten meal [CGM] and soy protein concentrate [SPC]) × 2 FM replacement levels (20% and 40%) ×2 JMM inclusion (without and with)} ANOVA experimental design was applied. The control (Con) diet contained 60% FM. In the Con diet, 20% and 40% FM were replaced with CGM and SPC without or with 24% JMM inclusion, named the CGM20, CGM40, SPC20, SPC40, CGM20J, CGM40J, SPC20J, and SPC40J diets, respectively. A total of 675 juvenile fish were assigned into 27 tanks. Weight gain (WG), specific growth rate (SGR), and FC of fish fed the CGM‐replaced diets were significantly higher than those of fish fed the SPC‐replaced diets. Furthermore, dietary replacements of 20% FM achieved significantly higher WG, SGR, and FC in fish compared to those of 40% FM. Additionally, WG, SGR, and FC of fish fed the all‐plant‐protein‐replaced diets with JMM inclusion were significantly higher than those without JMM inclusion. WG, SGR, and FC of fish fed the Con diet were significantly higher than those of fish fed the CGM40, SPC20, SPC40, CGM40J, and SPC40J diets. In conclusion, up to 20% of FM can be replaced by CGM, with or without JMM inclusion, or by SPC with JMM inclusion in a 60% FM‐based diet without significantly impairing the growth performance of red sea bream.

This study presents a bibliometric analysis of scientific publications concerning gilthead sea bream (Sparus aurata) and European sea bass (Dicentrarchus labrax) from authors affiliated with institutions in Türkiye between 1984 and 2024, based on the Web of Science (WoS) database. A total of 708 publications were examined to assess annual publication trends, document types, leading authors and institutions, subject categories, journals, keywords, and citation dynamics. The findings indicate a remarkable increase in publication productivity starting in the mid-2000s, with a stabilization observed throughout the 2010s. Over 95% of the documents were identified as original research articles. Among the most prolific authors were: Şahin Saka, Muammer Kürşat Fırat, Yeşim Özoğul, Fatih Özoğul, and Orhan Tufan Eroldoğan. In terms of institutional contributions, Ege University, Çukurova University, and Istanbul University ranked as the top three. Most publications were concentrated in the categories of Fisheries, Marine and Freshwater Biology, and Food Science and Technology. Keyword analysis revealed that the studies were predominantly focused on terms such as “Dicentrarchus labrax”, “Sparus aurata”, “growth,” and “fatty acids.” According to citation analysis, the most cited publication was by Akdoğan et al. (2019), followed by works from Dural et al. (2007), Dimitroglou et al. (2011), and Süzer et al. (2008). In terms of total link strength, the most prominent publications were by Çaklı et al. (2008), Özoğul et al. (2007), Erkan (2007), Özoğul et al. (2013), and Yazgan et al. (2017). Overall, the results demonstrate that scientific research on sea bream and sea bass in Türkiye has evolved significantly over time, generating a substantial body of knowledge that provides a strategic reference framework for future research in the field.

Freshness is a key quality attribute in seafood, yet it is rarely labeled explicitly in the marketplace. This study examined how disclosing objective freshness information influences sensory evaluations and willingness to pay for red sea bream (Pagrus major) sashimi. Using a bioimpedance-based indicator that provides accurate, real-time freshness measurements, we conducted a within-subject tasting experiment structured in three sequential rounds (experimental conditions). In the first round, only basic product information was provided. In the second, participants were introduced to the freshness-measuring device and shown market-level freshness distributions. In the third round, the actual freshness level of each sashimi sample was disclosed. In the first two rounds, participants preferred and were willing to pay more for the less fresh sashimi, presumably due to more umami components. This trend reversed in the third round after disclosure. To interpret this reversal, we introduce two innovations. First, we used a revealed-preference approach by comparing evaluations of samples in the same objective freshness category before and after freshness prompts, identifying assimilation effects without relying on stated expectations. Second, we examined heterogeneity in treatment effects based on participants' connoisseurship-their ability to identify the fresher sample without labeling. Our findings suggest that, within the freshness range used in our experiment, freshness functions as an unperceived intrinsic cue: an objectively measurable attribute that does not influence consumer evaluation unless explicitly disclosed. These findings highlight the value of freshness labeling and the broader role of information in activating hidden quality perceptions, offering insights for improving consumer trust and choices in seafood markets.

Reports of learned behavioural adaptations of wild Cape stumpnose Rhabdosargus holubi (family Sparidae) were investigated in two estuarine systems in the Eastern Cape Province, South Africa. Underwater observational trials using video cameras demonstrated that fish rapidly responded to bait collection activities in the East Kleinemonde Estuary but not in the West Kleinemonde Estuary. By simulating the visual and auditory cues associated with the activity alone, evidence suggested that fish in the East Kleinemonde Estuary have learnt to associate these cues with the activity, likely allowing individuals to identify and respond to this novel foraging opportunity. It is suggested that historical rates of bait collection within these estuaries is likely the cause for differences in the fish behaviour between estuaries; furthermore, social learning in fish may play a role both in perpetuating learned behaviours in the systems where they occur, and learned behaviour may potentially be shared to new systems via fish migration. This study presents a rare example of natural behaviour conditioning of wild fish to an anthropogenic niche. Further investigations into the cognitive and behavioural processes that allow wild animals to respond to human disturbance should be expanded to better account for and manage the wide-ranging impacts of human disturbance.

Oceanographic features such as upwelling cells and currents contribute to shaping the evolutionary history of marine fishes, including species that may be important socio-economic resources. However, the impacts of these barriers are often cryptic and may change, particularly in a rapidly changing climate. Hence, sustainable fisheries management strategies need to take into consideration the influence of oceanographic barriers to the genetic structure of populations. Here, we evaluated the influence of the Benguela Upwelling System, a known barrier for warm-temperate fishes, on the evolutionary history of the blacktail seabream Diplodus capensis (family Sparidae), using eight microsatellite loci in conjunction with DNA barcoding of the cytochrome c oxidase 1 gene. Diplodus capensis is an important recreational and small-scale fishery species, distributed across southern Africa. Overall, there was significant genetic differentiation across the region, but the level of divergence varied with the genetic marker. Our results identified two isolated populations—in the northern and southern subsystems of the Benguela Upwelling System—with limited contemporary gene flow, and no sub-structuring detected within the subsystems. Because the species is vulnerable to exploitation, with declines in South Africa, our results suggest that management policies should aim at regional levels for the northern population (off Angola and Namibia), whereas the southern population (off South Africa) was identified as an isolated and highly connected population.

Along the south coast of South Africa, extreme upwelling events lead to rapid temperature declines and prolonged marine cold-spells, which have, on occasion, led to large-scale mortalities of coastal fishes. In a somewhat antagonistic process, fishing exploitation has been shown to target specific phenotypes, potentially selecting for higher physiological diversity within exploited populations, reducing resilience to adverse environmental conditions. This study investigated the effects of thermal stress and exploitation in two populations (exploited and unexploited) of the commercially and recreationally targeted red roman Chysoblephus laticeps (family Sparidae) during an intense upwelling and a marine cold-spell event, using acoustic telemetry data. The results show that the acceleration of tagged fish (a proxy for fish activity) during the upwelling event differed significantly between the two populations (p < 0.05), with fish in the unexploited population maintaining their activity, and fish in the exploited population exhibiting reduced activity. The activity of the fish was also significantly different between the populations during the marine cold-spell, with those in the exploited population exhibiting reduced activity over time compared with the unexploited population. These findings highlight the impact of thermal extremes on fish activity and suggest that exploitation may selectively remove individuals that are tolerant to these events, which might consequently reduce resilience of the fish population. Based on these findings, it is concluded that networks of marine protected areas can promote fish populations that are resilient to future climatic conditions.

The Megalocytivirus pagrus1 causes serious disease in aquaculture and is classified into three clades: infectious spleen and kidney necrosis virus (ISKNV), turbot reddish body iridovirus (TRBIV), and red sea bream iridovirus (RSIV), further classified as genotype I or II. Several recent studies have reported RSIV strains designated as mixed genotype I/II because they were assigned to different subtypes depending on the gene used for phylogenetic analysis. In 2024, three RSIV samples were collected in Japan, one of which (GT1-Oita2024) was PCR-positive but tested negative using an immune fluorescent antibody test (IFAT) with M10 antibodies. Thus, we performed whole genome sequencing and phylogenetic analysis of the IFAT-negative sample and the two other RSIV samples (GT2-Oita2024 and Ehime2024). In GT1-Oita2024, LEGFD, a known antigen of the M10 antibody, was found to harbour several mutations. Based on average nucleotide identity, GT2-Oita2024 and Ehime2024 were classified as genotype II, showing high homology with KagYT-96 and RIE12-1. GT1-Oita2024 was classified as the intermediate type, showing high homology with SBIV-VP13 and 17SbTy. GT1-Oita2024 also contained regions showing homology with genotype I, genotype II and TRBIV. This is the first detection of this genotype in Japan. Further monitoring is warranted to determine the extent of its spread.