Dicentrarchus Labrax Research Articles

Fermented agar by-product and sunflower cake mixture as feedstuff for European seabass (Dicentrarchus labrax)

Industrial agar production from red seaweeds such as Gelidium sp. generates large quantities of by-products (GBP), often discarded as waste. GBP and sunflower cake (SC) are under-valorized as feedstuff due to their high non-starch polysaccharide (NSP) content. Solid-state fermentation (SSF) may disrupt NSP and improve their nutritional value. This study evaluated the utilization of Aspergillus ibericus and Aspergillus niger for SSF of a GBP and SC mixture (1:1 ratio; Gmix). SSF with A. ibericus decreased neutral detergent fiber (NDF) content (P < 0.05) along with high β-glucosidase activity (P < 0.05). SSF with A. niger increased crude protein, reduced NDF and acid detergent fiber (ADF) content, and produced higher xylanase, cellulase, and protease activities (P < 0.05). A 63-day growth trial with European sea bass (Dicentrarchus labrax) juveniles tested four isoproteic and isolipidic diets (44 % protein; 16 % lipids): a control diet without Gmix and three diets incorporating 10 % Gmix unfermented (diet Gmix), fermented by A. ibericus (diet Gmix-ibericus), or by A. niger (diet Gmix-niger). The Gmix and Gmix-ibericus diets promoted similar growth to the control, but the Gmix-ibericus diet supported higher feed efficiency, nitrogen, and energy utilization than the control diet (P < 0.05). The Gmix-niger diet negatively affected overall growth, feed intake, and utilization. Plasma metabolite levels, hepatic antioxidant enzyme activities, and lipid peroxidation were similar among diets. However, the Gmix-ibericus diet reduced total and oxidized glutathione levels (P < 0.05). Overall, G-mix or Gmix-ibericus diets did not compromise European seabass performance or oxidative status, with the Gmix-ibericus diet enhancing feed utilization efficiency by 25 %. Further studies are needed to understand the negative impact of the Gmix-niger diet on the European seabass.

Dietary Curcumin Nanoparticles Improve Growth Performance, Oxidative Status and Immune Response of European Seabass (Dicentrarchus Labrax)

Abstract A 90 days of feeding trial was employed for evaluating the effects of dietary supplementation with curcumin nanoparticles (CURNPs) on growth performance, hematological and biochemical parameters, immune response, antioxidant status, and intestinal and hepatic architecture in European seabass (Dicentrarchus labrax) fingerlings. Fish (n = 300, initial body weight = 10.02 g ± 0.11 g) received supplementary CURNPs at rates of 0 (control; CURNPs0), 50 (CURNPs50), 100 (CURNPs100) and 150 (CURNPs150) mg/kg diet for 90 days. Growth performance (final body weight (FBW), daily weight gain (DWG), weight gain (WG), relative growth rate (RGR), and protein efficiency ratio (PER)) and feed uptake (feed conversion rate (FCR)) were improved significantly in CURNPs (100 and 150 mg/ kg)-supplemented groups. The hematological parameters red blood corpuscles (RBCs), hemoglobin (Hb), and packed cell volume (PCV) were improved significantly (P&lt;0.001) in CURNPs150 and CURNPs100 groups, while CURNPs150 had the lowest values of monocytes (P = 0.019) and heterophils (P&lt;0.005) when compared with other groups. Glucose was higher and lipid profile (total cholesterol and triglycerides) were lower in all CURNPs-supplemented groups as compared to the control group. Fish fed with CURNPS at various levels exhibited remarkable increase in digestive enzymes (amylase and lipase), immune markers (immunoglobulin G (IgG), lysozyme and phagocytic indices), and antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)). A noticeable decrease (P&lt;0.05) in malondialdehyde (MDA) and considerable upregulation of hepatic insulin-like growth factor 1 (IGF1) and interleukin-1beta (IL-1β) mRNA levels were found in CURNPs-supplemented fish in a dose-dependent manner. The down regulation of hepatic heat shock protein 70 (HSP70) was observed in CURNPs150. Intestinal and hepatic architectures were improved significantly by CURNPs. In conclusion, CURNPs supplementation improved growth performance, feed consumption and digestion, hematological and biochemical markers, immune response, and redox homeostasis in D. labrax. Therefore, CURNPs could be supplemented in the diets of D. labrax as a natural alternative to promote overall performance.

Evaluation of the Environmental Oxidative Stress on Apoptotic Related Genes and DNA Damage in Sparus aurata and Dicentrarchus labrax in Different Areas Along the Mediterranean Sea, Egypt

Evaluation of the Environmental Oxidative Stress on Apoptotic Related Genes and DNA Damage in Sparus aurata and Dicentrarchus labrax in Different Areas Along the Mediterranean Sea, Egypt

Technical specifications for a EU-wide baseline survey of antimicrobial resistance in bacteria from aquaculture animals.

The European Commission requested scientific and technical assistance in the preparation of a EU-wide baseline survey of antimicrobial resistance (AMR) in bacteria from aquaculture animals. It is recommended that the survey would aim at estimating the occurrence of AMR in Aeromonas spp. isolated from Atlantic Salmon (Salmo salar), European seabass (Dicentrarchus labrax) and trout (Salmo trutta, Salvelinus fontinalis, Oncorhynchus mykiss) intended to consumption, at harvesting (at farm/slaughter), at the EU level and in addition, at estimating the occurrence and diversity of AMR of Escherichia coli, Enterococcus faecium, Enterococcus faecalis, Vibrio parahaemolyticus and Vibrio alginolyticus in blue mussel (Mytilus edulis) and Mediterranean mussel (Mytilus galloprovincialis) from production areas and at dispatch centres at the EU level. These technical specifications define the target populations, the sample size for the survey, sample collection requirements, the analytical methods (for isolation, identification, phenotypic susceptibility testing and further genotypic analysis of some of the bacteria targeted) and the data reporting requirements. The data to be reported by the EU Member States to support this baseline survey are presented in three data models. The results of the survey should be reported using the EFSA reporting system.

A Case Study on Economic Analysis of Sea Cage Farms in the Black Sea, Türkiye

The main aim of this research is to understand the value chains of enterprises engaged in aquaculture in sea cages in the Black Sea region of Türkiye, to determine production costs and to make a general analysis of the aquaculture sector. Random sampling method was used to ensure that farmers were equally represented in the survey. Data for the survey were randomly selected from 16 separate farms spread throughout 4 different marine cage locations. Furthermore, fish traders and sector stakeholders were interviewed. The businesses examined within the scope of the study are divided into 3 groups: small (250 -500 tons/year), medium (501-999 tons/year) and large (&gt;1000 tons/year), according to their capacities. The most important expense items of enterprises consist of variable costs. Among the variable costs, the purchase of fry fish, feed purchase, and labor costs constitute the most important expenditure items. Among the fixed costs, the most important expense is depreciation costs. The unit cost of one kg of fish varies between 2.7 and 3.0 euros. Considering that the trout (Oncorhynchus mykiss) and seabass (Dicentrarchus labrax) in the Black Sea are at the level of 3.5 Euro, the profit rate of the enterprises is between these levels. Recently, since trout from the Black Sea has been exported to the Far East Country (particularly Japan), its price has also increased. In 2018, the average retail price (including VAT) and medium selling price of seabass and trout were at a level of 5.24 and 5.34 Euros respectively. Despite all these positive developments, climate change continues to pose a threat in terms of disease outbreak and marketing problems.

Thermal modulation of energy allocation during sex determination in the European sea bass (Dicentrarchus labrax)

Water temperature governs physiological functions such as growth, energy allocation, and sex determination in ectothermic species. The European sea bass (Dicentrarchus labrax) is a major species in European aquaculture, exhibiting early dimorphic growth favoring females. The species has a polygenic sex determination system that interacts with water temperature to determine an individual’s sex, with two periods during development that are sensitive to temperature. The current study investigated the influence of water temperature on energy allocation and sex-biased genes during sex determination and differentiation periods. RNA-Sequencing and qPCR analyses were conducted in two separate experiments, of either constant water temperatures typical of aquaculture conditions or natural seasonal thermal regimes, respectively. We focused on eight key genes associated with energy allocation, growth regulation, and sex determination and differentiation. In Experiment 1, cold and warm temperature treatments favored female and male proportions, respectively. The RNA-seq analysis highlighted sex-dependent energy allocation transcripts, with higher levels of nucb1 and pomc1 in future females, and increased levels of egfra and spry1 in future males. In Experiment 2, a warm thermal regime favored females, while a cold regime favored males. qPCR analysis in Experiment 2 revealed that ghrelin and nucb1 were down-regulated by warm temperatures. A significant sex-temperature interaction was observed for pank1a with higher and lower expression for males in the cold and warm regimes respectively, compared to females. Notably, spry1 displayed increased expression in future males at the all-fins stage and in males undergoing molecular sex differentiation in both experimental conditions, indicating that it provides a novel, robust, and consistent marker for masculinization. Overall, our findings emphasize the complex interplay of genes involved in feeding, energy allocation, growth, and sex determination in response to temperature variations in the European sea bass.

Fish Welfare – A Case Study: Reviling for the first-time side effects of vaccination in European sea bass (Dicentrarchus labrax) and barramundi (Lates calcarifer) in the Israeli fish farming

Vaccination is an effective way to control many infectious diseases in fish. Israeli fish farming has successfully used two vaccines over the last 30 years and has no problem with the side effects of vaccination. However, after introducing new species, a new problem emerged: these fish, after vaccination, demonstrated peritoneal lesions such as granulomas. At the same time, the fish did not show retarded growth or suffering during the fattening period. This study was conducted to establish the connection between vaccination and the appearance of granulomas. Evidence drawn from this research work and comparing vaccinated and non-vaccinated fish confirms that intraperitoneal granulomas do not impact the growth, performance, or fish fillet quality at harvest.

Recruitment of European sea bass (Dicentrarchus labrax) in northerly UK estuaries indicates a mismatch between spawning and fisheries closure periods.

European sea bass (Dicentrarchus labrax) is a species of high commercial and recreational value, but it exhibits highly variable recruitment rates and has been subject to recent declines. Emergency management measures put in place to protect spawning stocks include the annual closure of commercial and recreational fisheries over a 2-month, February-March, window. Whether this protection measure is having the desired outcome for this data-poor species remains unclear. Otolith microstructural analyses (counts and widths of daily growth rings and check marks indicative of settlement) were used to estimate (1) spawn timing, (2) pelagic larval duration and settlement timing, (3) growth rate and condition, and (4) the otolith-fish size relationship for juvenile European sea bass caught from two estuaries in Wales (Dwyryd, Y Foryd), located at the northern edge of the species range. We observed a significant mismatch between the timing of fisheries closures and the spawning, with 99.2% of recruits having been spawned after the fishery had reopened (back-calculated median spawn date = May 5 ± 17 days SD), suggesting that the closure may be too early to adequately protect this population. Further, we present the first empirically derived estimates of pelagic larval duration for sea bass recruits settling in UK habitats, which showed a strong negative relationship with spawn date. Finally, we found significant differences in fish condition between the two estuaries, suggesting local variation in habitat quality. The results suggest that the timing of current fisheries closures may not be adequately protecting the spawners supplying these northernmost estuaries, which are likely to become increasingly important as sea bass distributions shift northward in our climate future.

Bentonite-supplemented diets improved fish performance ammonia excretion haemato-biochemical analyses immunity antioxidants and histological characteristics of European seabass Dicentrarchus labrax

The purpose of this research was to examine the potential effects of bentonite (BN) supplemented diets on growth, feed utilization, blood biochemistry, and histomorphology of Dicentrarchus labrax. Six treatments in triplicate were tested: B0, B0.5, B1.0, B1.5, B3.0, and B4.5, which represented fish groups fed diets supplemented with 0, 0.5, 1, 1.5, 3, and 4.5% BN, respectively. For 84 days, juveniles’ seabass (initial weight = 32.73 g) were fed diets containing 46% protein, three times daily at 3% of body weight. With a 5% daily water exchange, underground seawater (32 ppt) was used. Findings revealed significant improvements in water quality (TAN and NH3), growth (FW, WG and SGR) and feed utilization (FCR, PER and PPV) in fish fed BN-supplemented diets, with the best values in favor of the B1.5 group. Additional enhancements in kidney function indicators (urea and uric acid) and liver enzymes were observed in fish of the BN-treated groups along with a decrease in cholesterol level in the B1.5 group. Further improvements in fish innate immunity (hemoglobin, red blood cells, glucose, total protein, globulin, and immunoglobulin IgM), antioxidant activity (total antioxidative capacity and catalase), and decreased cortisol levels in fish of the BN-treated groups. Histological examinations of the anterior and posterior intestines and liver in groups B1.5 and B3 revealed the healthiest organs. This study recommends BN at a concentration of 1.5% as a feed additive in the Dicentrarchus labrax diet.

The Dicentrarchus labrax estrogen screen test: A relevant tool to screen estrogen-like endocrine disrupting chemicals in the aquatic environment

In response to the need for the diversification of regulatory bioassays to screen estrogen-like endocrine disrupting chemical (EEDC) in the environment, we propose the use of a reporter gene assay involving all nuclear estrogen receptors from Dicentrarchus labrax (i.e., sbEsr1, sbEsr2a, or sbEsr2b). Named DLES test (D. labrax estrogen screen), it aims at complementing existing standardized in vitro tests by implementing more estrogen receptors notably those that do not originate from humans.Positive responses were obtained with all three estrogen receptors, and—consistently with observations from other species—variations in sensitivity to E2 were measured. Sensitivity and EC50 values could be classified as follows: sbEsr2b < sbEsr2a < sbEsr1. The pharmacological characterization with a human estrogen receptor antagonist (fulvestrant) successfully validated the specific involvement of each sbEsr and evidenced the capacity of the DLES test to highlight antagonist interactions. The DLES test was applied to WWTP contaminant extracts. A positive response was detected in the inflow sample in accordance with the YES test, but not in the outflow sample. Notwithstanding, the DLES test (sbEsr2b) exhibited greater sensitivity for the screening of those samples. This study demonstrates the need for more comprehensive testing including representatives of marine species for a better detection of EEDCs. The DLES test appears as a pertinent tool to predict adverse effects and to widen the scope of screening and hazard assessment of EEDCs in the environment.

Po-210 in plankton and fish from coastal waters (gulf of Trieste, northern Adriatic Sea)

The activity concentrations of Po-210 were determined in seawater (<0.45 μm), suspended particulate matter (0.45–20 μm), fractionated plankton (20–50 μm, 50–200 μm, >200 μm) and tissues from four fish species, namely European seabass (Dicentrarchus labrax), Golden grey mullet (Chelon auratus), Gilt-head bream (Sparus aurata) and Common pandora (Pagellus erythrinus), collected in the Gulf of Trieste (northern Adriatic Sea). The activity concentration of Po-210 in seawater varied from 0.4 to 2.2 mBq/L in the dissolved phase (<0.45 μm) and from 0.4 to 0.8 Bq/L in suspended particulate matter (0.45–20 μm). Plankton fractionation showed the levels of 62–395 Bq/kg Po-210 in the >200 μm mesoplankton fraction, 65–459 Bq/kg in 50–200 μm and 52–537 Bq/kg in 20–50 μm microplankton fractions. No significant differences were found between fractions. The Po-210 distribution trend in fish tissues was in order: liver > stomach with intestine > kidney > spleen > gonads > gills > muscle. Bioaccumulation factors were determined for fish tissues indicating that the amount of Po-210 mostly depends on fish feeding habits. Hence, the main pathway entry of Po-210 is through ingested food. The highest estimated average total annual effective ingestion doses of Po-210 are obtained via the consumption of Common Pandora (7.1 μSv/year to 16.5 μSv/year) while the lowest doses are due to the consumption of European seabass (0.32 μSv/year to 0.76 μSv/year). Comparison with levels reported for other Mediterranean and Atlantic areas showed that only activitiy concentrations of Po-210 in fish appear significantly different, most likely because different fish species were analysed. The human dose exposure via fish consumption in the area is rather low.

Serum proteinogram of gilthead seabream (Sparus aurata) and European sea bass (Dicentrarchus labrax) as a new useful approach for detecting loss of haemostasis

Proteinograms, a semiquantitative analytical method that separates proteins into multiple bands, have not been explored in teleosts for diagnostic or prognostic purposes. This study aimed to establish reference values for proteinograms in the serum of gilthead seabream (Sparus aurata) and European sea bass (Dicentrarchus labrax), two important farmed fish species in the Mediterranean region. Serum proteins were studied using SDS-PAGE, electropherogram, and HPLC-mass spectrometry. SDS-PAGE analysis revealed four major bands of proteins around 11, 25, 70, and 100 kDa in the serum of gilthead seabream and European sea bass. Electropherogram results showed that a protein with a molecular weight of 76.8 kDa was the most abundant protein in the serum of gilthead seabream, while a peak of 75.5 kDa was the most abundant in European sea bass. HPLC-mass spectrometry detected 87 proteins and 119 proteins in the serum of gilthead seabream and European sea bass, respectively, including α1-globulins, α2-globulins, β-globulins, and γ-globulins. Notably, the albumin sequence was not detected in either of the two species. These results help to characterize the serum protein profile and to establish reference proteinograms for these two fish species. They also provide a basis for the development of novel approaches for the rapid detection of loss of haemostasis due to stress, health disorders or disease in farmed fish.

Seasonal migrations of the European sea bass (Dicentrarchus labrax L.) in UK and surrounding waters

The movements and behaviour of mature European sea bass (Dicentrarchus labrax L.) in UK waters have not been studied extensively since a series of mark-recapture experiments during the 1970s, 80s and 90s. To better understand the timing and extent of seasonal migrations, 171 mature sea bass > 42 cm were internally tagged with floated electronic tags programmed to record temperature and depth, and released in the English Channel, in the southern North Sea and in the Irish Sea. Among the 48 tags returned to date, sea bass were at liberty for 370 ± 337 days and were recovered 172 ± 200 km from their respective release locations. Most tags were recovered from beaches (54%), or via the fishery (44%). A comparison of the reconstructed tracks from returned electronic tags with the recapture locations of 237 mark-recapture returns (6.5%) from 3615 sea bass released between 1970 and 2020 showed strong overlap. Seasonal movements between shallow areas (Q2–Q3) and deeper spawning areas (Q4–Q1) were accompanied by elevated vertical swimming speeds and average water temperatures of 8.5 °C in the English Channel and Irish Sea, but lower temperatures in the North Sea. Movements between the Celtic Sea/Irish Sea and the North Sea and vice versa demonstrate high levels of connectivity in UK waters. We demonstrate that a proportion of sea bass remained resident within the North Sea throughout the year, with a strong suggestion that spawning might be occurring. These data have significant implications for the future sustainable management of sea bass stocks in UK and surrounding waters.

Elucidating the migrations of European seabass from the southern north sea using mark-recapture data, acoustic telemetry and data storage tags

The movement ecology of European seabass, Dicentrarchus labrax, remains poorly understood, especially in the northern ranges of its distribution. To investigate migration patterns of seabass from the southern North Sea, we combined data from different projects from four countries using various tagging techniques. This resulted in 146 recaptures (out of 5598 externally marked seabass), 138 detected animals (out of 162 seabass fitted with an acoustic transmitter) and 76 archived depth and temperature series (out of 323 seabass with an archival tag). Using geolocation modelling, we distinguished different migration strategies, whereby individual fish migrated to the eastern English Channel (15.1%), the western English Channel (28.3%), the Celtic Sea and the norther part of the Bay of Biscay (17.0%), or stayed in the North Sea (39.6%). A high number of seabass exhibited fidelity to the North Sea (90.5% of recaptures, 55.3% for acoustic transmitters and 44.7% of archival tags). Although seabass are generally considered to migrate southwards in winter, a large number of individuals (n = 62) were observed in the southern North Sea, where spawning might potentially occur in a particular deep location along the coast of Norfolk in the UK. Our results highlight the need to consider fine-scaled population structuring in fisheries assessment, and indicate that current seasonal fisheries closures are not aligned with the ecology of seabass in the North Sea.

Possible application of non-invasive tools to characterise European sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) from two different farming systems

Rearing conditions can affect fish morphology, physiology, and welfare in several manners, for instance given the different hydrodynamic conditions or stocking densities. This preliminary study aimed to evaluate non-invasive tools to understand if and how the farming system can influence external shape, skin pigmentation, and freshness evolution during refrigerated storage of European sea bass and gilthead sea bream. A total of 100 individuals (50 sea bass and 50 sea bream) were obtained from a fish farm (located in Piombino, Italy) equipped with floating cages and inland tanks. Fishes were photographed in lateral aspect to analyse shape, while skin colour was analysed with a colorimeter. Freshness and Rigor Index were observed during 7 days of refrigerated storage. Results showed that shape and colour analyses can be useful tools to discriminate fish farmed under different conditions, i.e., marine sea cages and inland tanks. Moreover, farming conditions significantly affected rigor resolution and fish freshness, especially in European sea bass.

Comparative Analysis of Immune Gene Transcription in Sea Bream (Sparus aurata) Challenged with RGNNV or RGNNV/SJNNV Betanodaviruses.

Gilthead sea bream and European sea bass display different resistance-susceptibility patterns during infection with different nervous necrosis virus (NNV) species, which may derive from differences in the triggered immune response. Based on this premise, we analysed the transcription of several selected immune-related genes in sea bream experimentally infected with NNV isolates obtained from sea bass (DlNNV, RGNNV) or sea bream (SaNNV, RGNNV/SJNNV). Viral replication only occurred in SaNNV-inoculated fish; therefore, the differences between the immune response elicited by both viruses may be the key to understanding the mechanism behind the inhibition of DlNNV replication. Principal component analysis clustered samples according to the viral isolate from 1 day post infection onwards and evidenced differences in the immune response against both viruses, even though no mortalities or symptoms were recorded. The response against DlNNV is characterized by higher rtp3 transcription early after the infection, longer-lasting il-10 transcription and stronger induction of casp1 and hsp70. These genes should be targets for future studies in order to elucidate their role in hampering NNV replication in sea bream, which is essential for developing effective prophylactic measures.

What makes a habitat a home? Habitat associations of juvenile European sea bass, Dicentrarchus labrax, in estuarine nurseries.

Selection of nursery habitats by marine fish, such as European sea bass (Dicentrarchus labrax), is poorly understood. Identifying and protecting the full range of juvenile nursery habitats is vital to supporting resilient fish populations and economically important fisheries. We examined how the condition, stomach fullness, and diet of juvenile European sea bass, along with their abundance, differ at high or low tide between the following estuarine habitats: saltmarsh, oyster reefs, shingle, sand, and mud edge habitats. Using a combination of fyke and seine netting we found no difference in sea bass abundance or condition across high-tide habitats, suggesting that rather than differentially selecting between them, juvenile sea bass use all available shallow habitats at high tide. Stomach fullness was significantly higher on saltmarsh and sand compared to mud, and thus these habitats may support better foraging. Dietary DNA metabarcoding revealed that sand and saltmarsh diets mostly comprised Hediste polychaetes, whereas zooplanktonic taxa dominated diets over mud. At low tide, sea bass abundance was highest in shingle and oyster reefs, where stomach fullness and condition were lowest. This may indicate a potential trade-off between using habitats for foraging and refuge. Although sea bass abundance alone does not capture productivity, the high abundance across all estuarine habitats at high tide suggests that it is important to consider the protection of a mosaic of interconnected habitats to support nursery functions rather than focus on individual habitat types.

Bioaccumulation of Organic and Inorganic Pollutants in Fish from Thermaikos Gulf: Preliminary Human Health Risk Assessment Assisted by a Computational Approach.

The monitoring of contaminants in fish species is pivotal for fishes' health and reproduction, as well as for human health. In the specific work, three major categories of contaminants, pesticides, pharmaceuticals, and macro and trace elements, were investigated in two major fish species, Dicentrarchus labrax and Solea solea, collected from Thermaikos Gulf, in Greece. To achieve this goal, three analytical methods using LC-MS/MS, GC-MS/MS, and ICP-MS were developed, validated, and applied to the collected fish samples. The results indicated a very low prevalence of caffeine and acetaminophen, both not exceeding 3.8 μg/kg fish. Similarly, thiabendazole, cypermethrin, and tricyclazole (pesticides) were found in a concentration range of 0.9 to 13.7 μg/kg fish, while in one D. labrax sample, traces of the metabolite of organochlorine pesticide DDT, o,p'-DDE were detected. Al, Mn, Fe, Zn, and Sr were the predominant trace elements in a concentration range of 500-20,000 μg/kg fish. Macro elements levels varied from 280 to 5405 mg/kg fish. Health risk assessment did not unveil an unacceptable risk for the human health of adults, apart from one sample presenting Hg above the regulatory levels. On the contrary, for children, the calculated hazard quotient values for Hg in all cases and for two As detections were higher than the threshold value of 1, indicating a potential risk.

Effect of solid-state fermentation of Brewer's spent grain on digestibility and digestive function of european seabass (Dicentrarchus labrax) juveniles

This study assessed the effects of dietary inclusion of solid-state fermented (SSF) brewer’s spent grain (BSG) with Aspergillus ibericus on nutrient and energy digestibility, digestive enzyme activity, and intestinal histomorphology of juvenile European seabass (Dicentrarchus labrax). Five diets (18 % crude lipids and 45 % crude protein) were formulated, including a control diet (without BSG), two diets with 10 % and 20 % unfermented BSG (10BSG and 20BSG), and two other diets with 10 % and 20 % fermented BSG (10BSG-SSF and 20BSG-SSF). SSF affected the BSG's nutritional composition, including a 21 % increase in protein content and reductions in lipid (49 %), cellulose (30 %), hemicellulose (34 %), and lignin (7.3 %) content. Antioxidant activity and total phenolic compounds were minimal before SSF but significantly increased after SSF. Dietary incorporation of 20 % BSG-SSF increased the digestibility of dry matter (p<0.01), protein (p=0.03), isoleucine (p=0.03), glutamate (p=0.02), lipids (p=0.04) and energy (p=0.04) compared to the 20BSG diet. Moreover, SSF also modulated digestive enzyme activity, reducing total protease (p=0.03) and trypsin (p=0.01) activities in fish fed the 10BSG-SSF diet compared to the control diet. Fish fed the 20BSG diet showed changes in intestinal histomorphology compared to those fed the control diet, and SSF of BSG appeared to mitigate these effects.Overall, these results indicate that SSF is a promising technique for enhancing the nutritional quality of low-value agro-industrial by-products, such as BSG, increasing their potential use as feed ingredients and contributing to reducing the climate and environmental footprint of aquaculture production.

Temporal and Spatial Dynamics of Vibrio harveyi: An Environmental Parameter Correlation Investigation in a 4-Metre-Deep Dicentrarchus labrax Aquaculture Tank.

Nowadays, European seabass (Dicentrarchus labrax) aquaculture is undergoing a significant expansion. Nevertheless, the aquaculture industry is plagued by vibriosis. The spatial and temporal dynamics of Vibrio harveyi were studied on a European seabass farm in northern France during seven months of 2022. Concrete specimens were suspended and water was pumped from different depths (0.3 m, 2.15 m and 4 m deep), providing insights into the biofilm and planktonic V. harveyi dynamics. The abundances of V. harveyi, in the biofilm and free-living forms, were positively correlated. The water parameters revealed seasonal fluctuations in temperature, pH, and salinity, with no significant differences observed across the water column. Quantification of V. harveyi revealed no significant differences between depths, but seasonality, with peak abundances observed in August, correlated with temperature increases. Principal component analysis identified temperature as a primary driver, but also additional parameters, such as salinity and pH. Vibriosis occurred during the sampling period, providing valuable insights into the conditions before, during, and after the outbreaks. This study underscores the importance of understanding V. harveyi behaviour in aquaculture, particularly in the context of global warming, for effective disease management and sustainable practices.