Evaluation of the nutritional value of processed lupin meal (Lupinus albus) with exogenous enzymes, as feed ingredient in European sea bass (Dicentrarchus labrax) aquafeeds

Commercial sea cage farming assessment of sustainable diets on growth performance and fillet quality of gilthead sea bream and European sea bass

This study presents the first description and characterisation of Lactococcus garvieae isolated from diseased European sea bass (Dicentrarchus labrax) farmed in Spain. During autumn 2023, two fish farms were affected by infectious outbreaks causing moderate cumulative fish mortality (5%-10%). Diseased fish showed clinical signs of haemorrhagic septicaemia, compatible with lactococcosis. Standardised screening tests revealed the presence of Gram-positive cocci in the kidney, spleen and brain of the diseased fish, and negative results for parasites and viruses. Bacterial cultures recovered from the internal organs of all diseased fish were identified as Lactococcus garvieae by phenotypic, genetic, immunological and proteomic analyses. Strains were sensitive to oxytetracycline, florfenicol and erythromycin and resistant to trimethoprim sulfamethoxazole. In addition, representative isolates were virulent to juvenile sea bass and Senegalese sole (Solea senegalensis) after intracoelomic challenge with doses ranging from 106 to 107 CFU/fish. SDS-PAGE and immunoblotting analyses, using rabbit serum anti L. garvieae CECT 5274 and serum from trout immunised with a bivalent oil-based vaccine against L. garvieae-Yersinia ruckeri, showed that the current strains of sea bass shared some antigenic proteins with strains of L. garvieae from other hosts and with the reference strain of L. petauri DSM104842. Our overall results confirm the presence of this emerging pathogen in Spanish marine aquaculture and suggest that commercially available lactococcosis vaccines could confer some protection to sea bass, helping to prevent this new threat.

Stress significantly impacts fish welfare, and for a comprehensive evaluation, welfare assessment requires an integrative approach. The objective of this study is to gain insight into the physiological and behavioural responses of European sea bass subjected to swimming and crowding stress tests through biologging. Individuals implanted with biologgers were subjected to swim tunnel and crowding tests, measuring locomotion, oxygen consumption, heart rate, acceleration and QRS-wave amplitude. During swimming stress tests, oxygen consumption correlated positively with heart rate (R2 = 0.56, p < 0.001) and acceleration (R2 = 0.76, p < 0.001). Acceleration values recorded by biologgers were strongly correlated with head and tail beat frequency (R2 = 0.69 and R2 = 0.70 respectively; p < 0.001), validating heart rate and acceleration as reliable proxies for energy expenditure in sea bass. During the crowding challenge, heart rate increased progressively with each stressing event, while QRS-wave amplitude and acceleration peaked with stress but decreased in-between stressors. The assessment of physiological and behavioural responses of sea bass to swimming and crowding stress tests with biologgers allows the characterization of four welfare states, and therefore, highlights the potential of biologging for fish stress response and welfare monitoring.

The suitability of using electronic nose (e-nose) on vacuum packed gutted descaled sea bass (Dicentrarchus labrax) during 18 days in refrigeration (0-4°C) was investigated. Microbiological (total viable count, psychrophilic bacteria, aerobic bacteria) chemical (TVB-N, TMA, TBARS) and sensory quality were also determined in this study. Viable counts and psychrophilic bacteria counts risen through the storage period of European sea bass that was packed with vacuum and gutted. Total viable counts, psychrophilic bacteria count surpassed the shelf life limit (7 log cfu/g) at day 18. Upon completion of the 18th day of the storage period; TVB-N, TBARS, TMA-N were concluded as 22.42±2.87 mg/100 g, 0.37±0.12 µmol/100g, 4.12±0.41 mg/100 g, respectively. Sensory score was determined as 14.43±0.14 on the 18th days of storage. The findings of this study reveal that the microbiological data indicates the using by date of vacuum-packed sea bass at 4°C is 15th day of the storage. In electronic nose measurements, the sensor results of days 1st, 4th, 6th and 8th, when the freshness of the fish was assumed to continue, gave values close to each other, while the distributions of day 8th were more scattered than the others, which was accepted as an indication that changes in the odour had begun. The values belonging to the 11th, 13th and 15th days of storage were close to each other and sometimes gave the same distribution. In future studies integration of e-nose technology with traditional sensory evaluation methods may be a suitable method for determining fish quality.

Transcriptional profiling of receptor-transporting protein 3 variants in European sea bass and gilthead seabream suggests divergent roles.

Environmental changes can induce epigenetic modifications, influencing gene expression, phenotype, and species adaptation. This study investigates how temperature affects genome-wide DNA methylation patterns, particularly in genes crucial for sex development and whether these modifications can be transmitted across generations. Using the European sea bass —a fish model with both genetic and environmental sex determination— we analyzed DNA methylation at single nucleotide resolution using reduced representation bisulfite sequencing in 64 individuals from five families across two generations (F0 and F1). Parental fish (F0) were exposed to either control (16 °C, C) or elevated (21 °C, T) temperatures from 12 to 60 days post-fertilization. Their offspring (F1) were then subjected to four thermal regimes: control (CC), ancestral exposure via sires (TC), developmental exposure in offspring (CT), and dual exposure (TT). We determined the length of differentially methylated regions (DMRs) using a conservative, reproducible, and species-specific method adapted from plant epigenetics. To disentangle ancestral and developmental temperature effects, DMRs were classified according to their association with F0, F1, or F0 x F1 interaction effects. This allowed us to quantify the relative contribution of each treatment, separately for testes and ovaries in the F1 generation. While the proportion of additive DMRs showing cumulative temperature effects (e.g., 2.1% in testes, 1.4% in ovaries) was relatively rare, a substantial proportion of DMRs (37% in testes, 31.1% in ovaries), exhibited opposing methylation changes with F0 and F1 treatments, indicative of compensatory epigenetic interactions. These interactions were also reflected at the phenotypic level: TT individuals showed body weights comparable to CC, and the sex ratio in TT approached statistical significance when compared to CC (P = 0.051), suggesting a link between epigenetic regulation and phenotypic plasticity under elevated temperatures. Finally, we also investigated the inheritance of epimarks from sires to offspring. While most epimarks remained stable across generations, ~ 5% of all DMRs were both temperature-induced and inherited, offering direct evidence for environmentally responsive multigenerational epigenetic inheritance. This study demonstrates the role of temperature in shaping the epigenome and highlights the potential of epigenetic plasticity and inheritance in species adaptation and conservation amid global warming.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13072-025-00630-5.

This study presents, for the first time, the occurrence and community structure of wild fish inside marine aquaculture cages of gilthead seabream (Sparus aurata), European sea bass (Dicentrarchus labrax), greater amberjack (Seriola dumerili), meagre (Argyrosomus regius), and common dentex (Dentex dentex). Coexistence of farmed and wild fish was observed only in cages of gilthead seabream and European sea bass, with wild fish constituting 0.08% of the total sampled fish biomass. Twelve wild fish species from five families were recorded: Carangidae, Clupeidae, Mugilidae, Moronidae, and Sparidae. Bogue (Boops boops) and jack mackerel (Trachurus sp.) were the most abundant. Multivariate analysis indicated that location significantly influenced the wild fish community composition, while reared species and farming duration, along with their interaction, had no significant effect. Descriptive comparisons suggested potential differences in biometric traits of bogue and jack mackerel between reared species and farming duration. The findings highlight the need for further research on wild fish in cages to better understand the potential health and biosecurity risks they may pose.

Intestinal microbiota populations are constantly shaped by both intrinsic and extrinsic factors, including diet, environment, and host genetics. As a result, understanding how to assess, monitor, and exploit microbiome-host interplay remains an active area of investigation, especially in aquaculture. In this study, we analyzed the taxonomic structure and functional potential of the intestinal microbiota of European sea bass and rainbow trout, incorporating gilthead sea bream as a final reference. The results showed that the identified core microbiota (40 taxa for sea bass and 20 for trout) held a central role in community organization, despite taxonomic variability, and exhibited a predominant number of positive connections (>60% for both species) with the rest of the microbial community in a Bayesian network. From a functional perspective, core-associated bacterial clusters (75% for sea bass and 81% for sea bream) accounted for the majority of predicted metabolic pathways (core contribution: >75% in sea bass and >87% in trout), particularly those involved in carbohydrate, amino acid, and vitamin metabolism. Comparative analysis across ecological phenotypes highlighted distinct microbial biomarkers, with genera such as Vibrio, Pseudoalteromonas, and Paracoccus enriched in saltwater species (Dicentrarchus labrax and Sparus aurata) and Mycoplasma and Clostridium in freshwater (Oncorhynchus mykiss). Overall, this study underscores the value of integrating taxonomic, functional, and network-based approaches as practical tools to monitor intestinal health status, assess welfare, and guide the development of more sustainable production strategies in aquaculture.

Interactions between micro(nano)plastics and natural organic matter: implications for toxicity mitigation in aquatic species.

Nutritional enhancement of lupin meal (Lupinus albus), through fermentation with Saccharomyces cerevisiae, as plant protein ingredient in aquafeeds for the European sea bass (Dicentrarchus labrax).

Impact of dietary protein levels and feeding regimes on growth performance and biochemical profile of European sea bass (Dicentrarchus labrax) reared in a brackish water recirculating aquaculture system

Over the past years, with the growing interest in sustainable biomaterials, marine collagen has been emerging as an interesting alternative to bovine collagen. It is more easily absorbed by the body and has higher bioavailability. In this study, collagen was extracted from Dicentrarchus labrax (sea bass) skin, a fishery by-product, thus valorizing waste streams while reducing environmental impact. To overcome the intrinsic weak mechanical of collagen, it was combined with chitosan to produce composite scaffolds for skin tissue engineering. The incorporation of collagen proved crucial for scaffold performance: (i) it promoted the formation of an open-pore architecture, favorable for cell infiltration and proliferation; (ii) it enhanced swelling behavior suitable for exudate absorption and maintenance of a moist wound environment; (iii) by tuning the chitosan/collagen ratio, it enabled us to control the degradation rate; (iv) it conferred antioxidant properties; and (iv) by adjusting collagen/chitosan concentrations, it allowed fine-tuning of mechanical properties, ensuring sufficient strength to resist stresses encountered during wound healing. In vitro assays demonstrated that the scaffolds were non-cytotoxic and effectively supported mouse adipose tissue fibroblasts’ adhesion and proliferation. Finally, all formulations exhibited marked bactericidal activity against the human pathogen Staphylococcus aureus and the methicillin-resistant Staphylococcus aureus, with a Log reduction greater than 3 (a reduction of at least 99.9% in bacterial growth) compared to the control. Collectively, these findings highlight collagen not only as a sustainable resource but also as a functional component that drives the structural, physicochemical, biological, and antimicrobial performance of chitosan/collagen scaffolds for skin tissue engineering.

Viral nervous necrosis, caused by the nervous necrosis virus (NNV), is an important threat to aquaculture, causing great economic losses and a high environmental burden. European sea bass (Dicentrarchus labrax) is highly affected by NNV, and selective breeding programs for disease resistance have been established in order to achieve a sustainable aquaculture and minimize the need for vaccines, drugs and antibiotics. Resistant and susceptible European sea bass were experimentally challenged with NNV and their head kidney transcriptomes were analyzed at three time points, i.e., 3 hpi, 2 dpi and 14 dpi. Numerous differentially expressed genes (DEGs) were identified in the head kidneys of resistant and susceptible infected vs. non-infected sea bass. Gene ontology enrichment, pathway, and protein–protein interaction analyses revealed that the NNV-resistant fish control their response to viral infection more efficiently, utilizing different mechanisms compared to the susceptible fish. Resistant fish displayed higher levels of interferon-related elements, cytokines, antigen presentation, T-cell activity, apoptosis, and programmed cell death combined with a controlled inflammatory response and more active proteasome and lysosome functions. The susceptible fish appeared to have high immune responses at the early infection stages, accompanied by high expressions of inflammatory, complement and coagulation pathways. Insulin metabolism was better regulated in the resistant fish and the control of lipid metabolism was less effective in the susceptible family. The cytoskeleton- and cell adhesion-related pathways were mostly down-regulated in the susceptible fish, and the intracellular transport and motor proteins were utilized more efficiently by the resistant fish. The present study represents a thorough transcriptomic analysis of NNV infection effects on a resistant and a susceptible European sea bass head kidney. The obtained results provide valuable information on the mechanisms that offers pathogen resistance to a host, with many aspects that can be exploited to develop more efficient approaches to fighting viral diseases in aquaculture.

Physiological responses of Arctic and Baltic Sea populations of toxigenic Alexandrium ostenfeldii (Dinophyceae) to different climate change stressors.

Lactococcus garvieae is an emerging pathogen responsible for lactococcosis, a haemorrhagic septicemia affecting fish associated with high mortality and widespread distribution. The disease primarily affects rainbow trout ( Oncorhynchus mykiss ), but L. garvieae has also been reportedin various freshwater and marine fish species, as well as in mammals, including humans. This study describes the first documented outbreaks of L. garvieae in gilthead sea bream ( Sparus aurata ), occurring in the Gulf of Follonica (Tuscany, Italy), following a previous episode in European sea bass ( Dicentrarchus labrax ) in the same area in 2023. Affected fish showed erratic and uncoordinated swimming. Macroscopic lesions included ocular and skin lesions, pericarditis, splenomegaly and haemorrhages in internal organs. Histopatological findings revealed severe fibrinous-necrotic pericarditis and epicarditis associated with bacterial aggregates and widespread granulomatous inflammation in the liver and spleen. Identification of L. garvieae was achieved employing multiple techniques: biochemical tests, miniaturized Analytical Profile Index (API rapid ID 32 strep, Biomerieux), MALDI-TOF MS (MicroFlex LT, Bruker), and molecular methods, including two independent end-point PCR assays followed by sequencing of the 16S–23S ITS region and DNA gyrase subunit B (gyrB) gene. Antimicrobial susceptibility testing of selected isolates was carried out using disk diffusion and minimum inhibitory concentration (MIC) methods, following standardised guidelines. This study presents new data on the characteristics of lactococcosis in gilthead sea bream ( Sparus aurata ), confirming Lactococcus garvieae as a primary pathogen and highlighting its potential impact on Mediterranean aquaculture, as well as the importance of implementing preventive strategies, including vaccination.

The objective of the present study was to ascertain the effect of diverse organic feeds (25ECO, 30ECO, and 35ECO) containing varying levels of fishmeal (25%, 30%, and 35%) on the growth and fillet quality of juvenile sea bass. The ECO diets were composed of a blend of organic vegetable proteins. The control diet contained 30% fishmeal without any organic ingredients. The experimental period spanned 196 days, during which the fish were fed twice daily, with an initial mean weight of 40 g. The results indicated that reducing fishmeal to 25% in the 25ECO diet negatively affected growth and increased feed consumption. The 30ECO diet, which contains 30% fishmeal, exhibited no adverse effects; however, its biometric outcomes diverged from those of the control diet. The 25ECO diet demonstrated superior Met retention levels, and certain free amino acids that enhance flavour (SER, ALA, ASP, and GLU) exhibited higher concentrations in fillets from fish fed ECO diets (35ECO and 30ECO). No substantial disparities were observed in the fatty acid profile or fillet nutritional indexes, which were deemed to be satisfactory and conducive to good health. From an economic perspective, the 30 ECO diet was deemed optimal and exhibited the greatest inclination towards purchase.

The Anti-Müllerian hormone (AMH) is widely recognized for promoting Müllerian duct regression in higher vertebrates and regulating key reproductive functions like steroidogenesis, folliculogenesis, and Leydig cell development. In teleost fish, which lack Müllerian ducts, Amh primarily influences male reproductive functions, including sex determination, testis differentiation, and germ cell proliferation. In adult fish, Amh supports gonad development and spermatogenesis, but its role in teleost gonadal physiology remains largely underexplored. This study reveals a novel steroidogenic function in the European sea bass (Dicentrarchus labrax) using in vitro testis culture, in vivo plasmid injection, and cell-based transactivation assays. The Amh-induced significant increase in androgen levels was also confirmed in Japanese medaka (Oryzias latipes) treated with recombinant sea bass Amh. Beyond activating the canonical Smad pathway, Amh also triggered the cAMP/PKA signalling pathway via its cognate type II receptor, Amhr2. Inhibitors of these pathways independently and synergistically counteracted Amh-induced CRE-Luc activity, indicating pathway crosstalk. Moreover, inhibition of the cAMP pathway suppressed Amh-induced androgen production in testis cultures, emphasizing the crucial role of protein kinase A in mediating Amh steroidogenic action. These findings uncover a novel steroidogenic function of Amh in teleosts and highlight its broader role in male reproductive physiology.

Abstract This study evaluated POET CFP, a corn‐fermented protein derived from dry‐mill bioethanol production, as a potential candidate for use in European seabass aquafeeds. The apparent digestibility coefficients (ADC) of POET CFP were evaluated and compared to soybean meal. The ADC of POET CFP protein was higher than that of soybean meal (92.7% vs. 83.9%), and the neutral detergent fiber (NDF) of POET CFP was partially digested (26%), while that of soybean meal was completely undigestible. However, the ADC of energy was similar between the two feedstuffs (70%). Two growth trials were performed to evaluate the effect on growth performance and feed utilization of European seabass for total or partial replacement of corn gluten meal (CGM) (Trial 1) or CGM and soybean meal (CGM + SBM) (trial 2) with POET CFP. For that purpose, a practical diet with 48% protein and 18% lipids was formulated to include 20% fish meal, 15% CGM, and 15% SBM (control diet). For trial 1, four diets similar to the control were formulated with POET CFP replacing CGM at 25%, 50%, 75%, and 100%. For trial 2, three other diets similar to the control were formulated, but POET CFP replaced CGM + SBM at 33%, 66%, and 100%. Triplicate groups of European seabass juveniles with 26 g were fed these diets for 85 days. Results of Trial 1 showed that total dietary replacement of CGM with CFP did not affect growth performance, feed intake, feed utilization, and whole‐body composition. N retention (% N intake) was also unaffected, but energy retention (% energy intake) linearly increased with dietary CFP inclusion. Further, the histomorphological appearance of the posterior intestine was unaffected by dietary CFP inclusion. Results of trial 2 showed that total dietary replacement of CGM + SBM with CFP did not affect growth performance, feed intake, feed utilization, and N and energy retention (% intake). However, polynomial contrasts showed a significant linear trend for increased growth performance and feed efficiency with the dietary inclusion of CFP. Whole‐body dry matter and lipid content linearly decreased with the dietary increase of CFP. No differences were observed between groups in the histomorphological appearance of the distal intestine. This study showed that CFP could completely replace CGM and SBM in diets for European seabass juveniles without affecting growth performance and feed utilization or adversely affecting posterior intestine morphology.

The present study investigates the impact of refrigeration storage on the freshness and shelf life of European sea bass (Dicentrarchus labrax). This investigation utilises computer vision systems and artificial neural networks (ANNs) to analyse the dynamics of the process. A non-destructive assessment approach was established by analysing the eye colour characteristics (RGB, Lab*, and HSI values) of fish stored at +4 °C for 15 days, with sampling occurring every three days. There were considerable changes in the colour range throughout the time, particularly a reduction of brightness (L*), which can be one indicator of the progressive deterioration of the fish›s freshness. The neural network multilayer perceptron was optimised with 20 neurons in the hidden layer and demonstrated a high correlation coefficient (R² = 0.98) between predicted and experimental shelf life values. The data indicates that the values of rack life, which were initially determined to be cautious, exhibited a high degree of correlation with the estimated values. The R2 value was determined to be 0.98. The technique offers a rapid and reliable non-destructive method for determining the freshness of fish, with potential applications in relevant areas such as quality control and natural security examination for aquaculture products. The present study investigates the impact of refrigeration storage on the freshness and shelf life of European sea bass (Dicentrarchus labrax). This investigation utilises computer vision systems and artificial neural networks (ANNs) to analyse the dynamics of the process. A non-destructive assessment approach was established by analysing the eye colour characteristics (RGB, Lab*, and HSI values) of fish stored at +4 °C for 15 days, with sampling occurring every three days. There were considerable changes in the colour range throughout the time, particularly a reduction of brightness (L*), which can be one indicator of the progressive deterioration of the fish›s freshness. The neural network multilayer perceptron was optimised with 20 neurons in the hidden layer and demonstrated a high correlation coefficient (R² = 0.98) between predicted and experimental shelf life values. The data indicates that the values of rack life, which were initially determined to be cautious, exhibited a high degree of correlation with the estimated values. The R2 value was determined to be 0.98. The technique offers a rapid and reliable non-destructive method for determining the freshness of fish, with potential applications in relevant areas such as quality control and natural security examination for aquaculture products.