Dicentrarchus Labrax Research Articles

Gastric evacuation in European seabass Dicentrarchus labrax (Linnaeus, 1758), forced-fed on commercial pellets

The effects of meal size and body size on gastric evacuation rates were parameterised for European seabass Dicentrarchus labrax (Linnaeus, 1758). A total of three gastric evacuation experiments were performed on small (15.7±0.8 cm) and large (21.5±0.4) size fish forced-fed with meals of 0.5 and 1.5 g composed of commercial pellets. The stomach contents were then recovered by serial slaughtering the fish at predetermined post-prandial times. The surface-area dependent function adequately describes the gastric evacuation in European seabass independently of meal size. A power function of fish length L was then employed to evaluate the impact of body size, revealing its notable effect on gastric evacuation rates of European seabass. Keywords: Aquaculture, Feeding regimes, General power function, Surface-area dependent

Genetic Variations of Fourth Exon Region of Prolactin Gene and Its Associations with Growth Traits in European Sea Bass Dicentrarchus labrax (Moronidae)

Genetic Variations of Fourth Exon Region of Prolactin Gene and Its Associations with Growth Traits in European Sea Bass Dicentrarchus labrax (Moronidae)

Nutritional innovations in superior European sea bass (Dicentrarchus labrax) genotypes: Implications on fish performance and feed utilization

The sustainable development of the aquaculture industry relies on the use of alternative conventional and emergent raw materials that contributes to a circular economy and to reduce the dependency on fish meals and fish oils coming from oceanic fish populations. Additionally, the genetic selection of farmed fish that can display higher growth and feed utilization when fed alternative feeds, is pointed out to be a complementary valuable tool to facilitate the implementation of circular economy approaches. The main purpose of the present study was to determine the effectiveness of genetic selection for growth in European sea bass, in response to a challenge with an alternative diet that aimed to partially replaced fishmeal (FM) by poultry meal (PM) and totally replace fish oil (FO) by a blend of poultry oil (PO) with a novel microalgae oil. The two families of fish juveniles were obtained by in vitro fertilization of selected for a multi-trait including high growth (genetically selected, GS) or non-selected (wild type, WT) broodstocks and then were nutritionally challenged with a control diet that mirrored a standard commercial diet with fishmeal (20%) and fish oil (7%), or a Future diet that partially replaced the FM by PM and totally replaced the FO by a blend of rapeseed oil, PO, and a novel DHA rich-algal oil. From the second month of feeding until the end of the trial, European sea bass that was selected since for 7 generations performed better in terms of growth than the wild-type genotype, possibly related with an apparent favored feed and nutrient utilization. Furthermore, selection decreased the perivisceral fat and increased the nutritional value of flesh by increasing DHA (in g/ 100 g flesh) and ARA contents. In contrast, the dietary treatment showed little effect on fish growth performance, denoting the successful partial replacement of FM by PM and the total replacement of FO by a blend of poultry oil and an emergent microalgal oil. However, Future diet tended to reduce the ADCs of some amino acids, as well as showed an additive effect to genotype in increasing the n-3 PUFA of flesh. Altogether, our data demonstrate that multi-trait genetic selection of European sea bass improve fish plasticity to cope with the variations of ingredients in alternative feeds with low FM/FO.

Salinity affects the efficiency of a brackish aquaponics system of sea bass (Dicentrarchus labrax) and rock samphire (Crithmum maritimum)

Brackish aquaponics using euryhaline fish and halophyte plants may be a sustainable method of functional food production. In addition, they could have a great potential as high nutritional, commercial and pharmaceutical value. This study investigated the effect of three different salinity levels (8 ppt, 14 ppt and 20 ppt) on the growth performance of sea bass (Dicentrarchus labrax) and rock samphire (Crithmum maritimum), the first-time production of essential oil and the nutrient-removal efficiency of rock samphire in a brackish aquaponic system. A total of 135 sea bass (weight 8.2 ± 0.15 g, length 9.5 ± 0.33 cm) and 54 rock samphire individuals (height 7.7 ± 0.20 cm) were distributed in the nine aquaponics systems (rearing temperature 20 ± 0.2οC). The seabass growth performance was significantly higher (p < 0.05) at 8 and 14 ppt salinity group than in 20 ppt, and FCR was significantly better at 8 and 14 ppt than in the 20 ppt (p < 0.05) salinity group. Rock samphire at 8 ppt showed significantly better growth and survival than those at 20 ppt (p < 0.05). Nitrate and phosphorous removal efficiencies were significantly higher at 8 and 14 ppt than at 20 ppt. Heat shock proteins (HSPs) and mitogen-activated protein kinases (MAPK) were differentially expressed, showing tissue-specific responses. The highest yield of essential oils was obtained at a salinity of 14 ppt (0.31 ± 0.03 mL per 100 g of dry plant weight). Seabass and rock samphire can have satisfactory growth performance in a tailored-made brackish aquaponic system and under the frame of sustainability and usage of saline water.

High Pressure Processing under Mild Conditions for Bacterial Mitigation and Shelf Life Extension of European Sea Bass Fillets

High pressure is an industrially established food preservation process applied for the minimal processing or cold pasteurization of chilled, fresh, or ready-to-eat products. This study aimed to quantify the effectiveness of high pressure on the inactivation of spoilage microflora and the shelf life extension of European sea bass (Dicentrarchus labrax) fillets. Fish fillets were subjected to mild, high pressure conditions (100–400 MPa; 3–25 °C; 5–10 min) and then stored at 0.0 ± 0.2 °C. Their shelf life was evaluated in terms of their microbiological, physicochemical, and sensorial quality. The results indicated that a shelf life extension of 1–5 d at 0 °C was achieved when pressures of 100 MPa were applied, whereas higher pressures resulted in an up to 5-fold increase in the shelf life of the fillets, depending on the applied pressure and temperature. A high pressure treatment combined with vacuum packaging showed an additional effect on the shelf life extension of the fillets, increasing the shelf life by 4–12 d when compared to aerobically stored products. Moreover, the high pressure treatment prevented lipid oxidation throughout the storage period, indicating no formation of secondary lipid oxidation products. The estimated shelf life of the fish fillets based on their sensorial quality was in accordance with the estimation based on the microbiological data.

Combined Effects of Temperature and Dietary Lipid Level on Body Composition, Growth, and Freshness Profile in European Seabass, Dicentrarchus labrax.

A fish trial was carried out to evaluate the combined effects of temperature and dietary lipid level on the body composition, growth performance, and freshness profile of the European seabass (Dicentrarchus labrax). Fish were kept for 56 days at 20 °C and 24 °C and fed on two diets, with 16% and 20% lipid. At the end of the trial, fish were euthanized at two temperature conditions (0.6 °C or -0.6 °C) and kept on ice for 10 days at 4 °C to evaluate their freshness condition. Findings demonstrated that fish reared at 24 °C presented a lower lipid level and a higher daily growth index than those at 20 °C. Additionally, sensory analysis (Quality Index Method-QIM) and microbiological analysis revealed that fish reared at 24 °C showed better freshness conditions than those at 20 °C. However, the 16S rRNA metabarcoding analyses revealed a higher proliferation of genera associated with fish-spoiling bacteria in the skin microbiome of fish reared at 24 °C, i.e., Vibrio and Acinetobacter, which was not observed in the skin microbiome of fish reared at 20 °C. Nevertheless, the dietary lipid level did not have any influence on fish freshness. Therefore, our data suggest that the increase in temperature to 24 °C is beneficial for the growth and freshness profile (lower QIM and lower CFUs/cm2) of this particular species. Additionally, the lower euthanasia temperature (-0.6 °C) seems to lead to higher fish freshness than the normal temperature (0.6 °C).

The impact of marine and terrestrial based extracts on the freshness quality of modified atmosphere packed sea bass fillets

The extracts of Padina pavonica (a macroalgae, ME), Rubus fruticosus (blackberry) leaves (BE), Juniperus oxycedrus waste (JWE) and Juniperus communis needles (JE) were used to evaluate their potential effects on chemical, microbial and organoleptic qualities of sea bass (Dicentrarchus labrax). The sensory assessment showed that fish fillets treated with BE, JE and ME were preferred more by the panellists, and rejected at 18 days of storage compared to the control (12 days). All extracts (except JWE) together with modified atmospheric packaging (MAP) decreased the values of biochemical parameters of sea bass fillets. TVB-N, PV, FFA, TBA values remained lower in treatment groups. Microbiological results were consistent with sensory results. Although microbial growth showed a rapid increase in the control and JWE groups during storage, BE, ME and JE groups significantly inhibited the bacterial growth in fish meat (p < 0.05). Lactic acid bacteria in sea bass fillets under MAP condition increased slightly during storage and reached the highest levels in the control and JWE groups, respectively, with the value of 5.60 and 5.52 log cfu/g at the end of storage. This study showed that all extracts except JWE together with MAP application extended the shelf life of sea bass fillets up to 18 days compared to the control (12 days), exhibiting potential antioxidant and antimicrobial agents in seafood industry.

Effect of Physicochemical Characteristics and Storage Atmosphere on Microbiological Stability and Shelf-Life of Minimally Processed European Sea Bass (Dicentrarchus labrax) Fillets

The aim of the present work was to evaluate the effect of various hurdles such as aw and pH as well as the storage atmosphere on the microbiological and sensory changes of minimally processed (lightly brined or marinated with acetic or citric acid) European sea bass (Dicentrarchus labrax) fillets. The results indicated that the shelf-life of brined fillets stored aerobically was 6 d while that of vacuum and MAP-stored was 12 d, since a reduced growth rate of spoilage bacteria was recorded. The physicochemical characteristics such as aw and water phase salt (WPS) were not considerably changed, while the oxygen levels into the packages ensure the microbiological safety of the product. The fillets marinated with acetic acid exhibited a longer shelf-life at 30 and 40 d under aerobic and reduced oxygen conditions, respectively, while the products marinated with citric acid were at 25 and 35 d respectively. A low pH resulted in reduced or even limited microbial levels, especially for the fillets marinated with acetic acid; something that ensures microbiological safety as well. The low or limited microbial levels in conjugation with the sensory attributes indicated that spoilage may be due to other mechanisms such as autolysis rather than microbial activity. Overall, the present work highlights the potential for further research and development of minimally processed, microbiologically safe and stable with extended shelf-life value added seafood to satisfy the corresponding consumer demands.

Characterization and Vaccine Potential of Outer Membrane Vesicles from Photobacterium damselae subsp. piscicida

Photobacterium damselae subsp. piscicida (Phdp) is a Gram-negative fish pathogen with worldwide distribution and broad host specificity that causes heavy economic losses in aquaculture. Although Phdp was first identified more than 50 years ago, its pathogenicity mechanisms are not completely understood. In this work, we report that Phdp secretes large amounts of outer membrane vesicles (OMVs) when cultured in vitro and during in vivo infection. These OMVs were morphologically characterized and the most abundant vesicle-associated proteins were identified. We also demonstrate that Phdp OMVs protect Phdp cells from the bactericidal activity of fish antimicrobial peptides, suggesting that secretion of OMVs is part of the strategy used by Phdp to evade host defense mechanisms. Importantly, the vaccination of sea bass (Dicentrarchus labrax) with adjuvant-free crude OMVs induced the production of anti-Phdp antibodies and resulted in partial protection against Phdp infection. These findings reveal new aspects of Phdp biology and may provide a basis for developing new vaccines against this pathogen.

Intestinal Fatty Acid Binding Protein Gene Variation in European Sea Bass (Dicentrarchus labrax)

Fatty acid binding proteins (FABPs), which belong to the multigene family, play an important role in homeostasis, lipid uptake and transport in tissues. Intestinal fatty acid binding protein (I-FABP) is a small cytosolic protein and is highly active in intracellular fatty acid metabolism in fish gut. The European Sea bass (Dicentrarchus labrax) is an important commercial marine fish species in the Mediterranean region. In the present study, the partial I-FABP gene region of European sea bass was sequenced for detecting single nucleotide polymorphism (SNP) using DNA sequencing. We identified one SNP (g.2450T&gt;C) in the noncoding region of the I-FABP gene in European sea bass. In this study, the relationship between the g.2450T&gt;C locus of the I-FABP (fabp2) gene and body length, post-anal length, body weight and fillet weight was found significant (PC locus in I-FABP which could affect growth and muscle fat content, can be used for marker-assisted selection (MAS) studies in European sea bass.

Nutritional, organoleptic and sensory quality of market-sized European sea bass (Dicentrarchus labrax) fed defatted Tenebrio molitor larvae meal as main protein source

Nutritional, organoleptic and sensory quality of market-sized European sea bass (Dicentrarchus labrax) fed defatted Tenebrio molitor larvae meal as main protein source

Micro- and macroalgae blend modulates the mucosal and systemic immune responses of European seabass (Dicentrarchus labrax) upon infection with Tenacibaculum maritimum

Micro- and macroalgae blend modulates the mucosal and systemic immune responses of European seabass (Dicentrarchus labrax) upon infection with Tenacibaculum maritimum

Thermal imprinting during embryogenesis modifies skin repair in juvenile European sea bass (Dicentrarchus labrax)

Fish skin is a multifunctional tissue that develops during embryogenesis, a developmental stage highly susceptible to epigenetic marks. In this study, the impact of egg incubation temperature on the regeneration of a cutaneous wound caused by scale removal in juvenile European sea bass was evaluated. Sea bass eggs were incubated at 11, 13.5 and 16 °C until hatching and then were reared at a common temperature until 9 months when the skin was damaged and sampled at 0, 1 and 3 days after scale removal and compared to the intact skin from the other flank. Skin damage elicited an immediate significant (p < 0.001) up-regulation of pcna in fish from eggs incubated at higher temperatures. In fish from eggs incubated at 11 °C there was a significant (p < 0.001) up-regulation of krt2 compared to fish from higher thermal backgrounds 1 day after skin damage. Damaged epidermis was regenerated after 3 days in all fish irrespective of the thermal background, but in fish from eggs incubated at 11 °C the epidermis was significantly (p < 0.01) thinner compared to other groups, had less goblet cells and less melanomacrophages. The thickness of the dermis increased during regeneration of wounded skin irrespective of the thermal background and by 3 days was significantly (p < 0.01) thicker than the dermis from the intact flank. The expression of genes for ECM remodelling (mmp9, colXα, col1α1, sparc, and angptl2b) and innate immunity (lyg1, lalba, sod1, csf-1r and pparγ) changed during regeneration but were not affected by egg thermal regime. Overall, the results indicate that thermal imprinting of eggs modifies the damage-repair response in juvenile sea bass skin.

Development and Application of a Mechanistic Nutrient-Based Model for Precision Fish Farming

This manuscript describes and evaluates the FEEDNETICS model, a detailed mechanistic nutrient-based model that has been developed to be used as a data interpretation and decision-support tool by fish farmers, aquafeed producers, aquaculture consultants and researchers. The modelling framework comprises two main components: (i) fish model, that simulates at the individual level the fish growth, composition, and nutrient utilization, following basic physical principles and prior information on the organization and control of biochemical/metabolic processes; and (ii) farm model, that upscales all information to the population level. The model was calibrated and validated for five commercially relevant farmed fish species, i.e., gilthead seabream (Sparus aurata), European seabass (Dicentrarchus labrax), Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), and Nile tilapia (Oreochromis niloticus), using data sets covering a wide range of rearing and feeding conditions. The results of the validation of the model for fish growth are consistent between species, presenting a mean absolute percentage error (MAPE) between 11.7 and 13.8%. Several uses cases are presented, illustrating how this tool can be used to complement experimental trial design and interpretation, and to evaluate nutritional and environmental effects at the farm level. FEEDNETICS provides a means of transforming data into useful information, thus contributing to more efficient fish farming.

Oxygenation of European seabass (Dicentrarchus labrax L.) in cages through aeration and effect on lipid metabolism.

Two groups of the same batch of European seabass were used in an industrial-scale trial in sea cages in Vorios Evoikos, Greece. For about one month, one of the two cages was oxygenated by use of compressed air injected in seawater through an AirX frame (Oxyvision A/S, Norway) at 3.5 m depth, while oxygen concentration and temperature were monitored every 30 min. The liver, gut, and pyloric ceca samples were taken from fish of both groups for measurement of gene expression of phospholipase A2 (PLA2) and hormone-sensitive lipase (HSL), and for histological analysis at the middle and end of the experiment. Real-time qPCR was performed with housekeeping genes ACTb, L17, and EF1a. The expression of PLA2 increased in pyloric caeca samples from the oxygenated cage, suggesting that aeration improved the absorption rate of dietary phospholipids (p < 0.05). Expression of HSL increased significantly in liver samples from the control cage, in comparison with the aerated cage (p < 0.05). Histological examination of sea bass samples revealed an increased fat accumulation in the hepatocytes of fish in the oxygenated cage. The results of the present study showed increased lipolysis induced by low DO levels in farmed sea bass in cages.

Water temperature explains part of the variation in basal plasma cortisol level within and between fish species.

Within the thermal tolerance range of fish, metabolism is known to escalate with warming. Rapid thermic changes also trigger a series of physiological responses, including activation of the stress axis, producing cortisol. Fish have adapted to their environment by producing a low level of plasmatic cortisol when unstressed (basal), so that thriving in their natural temperature should not impact their basal cortisol levels. Yet, surprisingly, little is known on how temperature affects cortisol within and between fish species. Here, we conducted a phylogenetic meta-analysis to (1) test whether temperature can explain the differences in basal cortisol between species and (2) evaluate the role of temperature on differences in cortisol levels between individuals of a same species. To do this, we retrieved basal plasma cortisol data from 126 studies, investigating 33 marine and freshwater fish species, and correlated it to water temperature. Intra-species variability in basal plasma cortisol levels was further investigated in two species: the European sea bass Dicentrarchus labrax and the Nile tilapia Oreochromis niloticus. Factors such as life stage, sex and weight were also considered in the analyses. Overall, our phylogenetic analysis revealed a clear positive correlation between basal cortisol level and the temperature at which the fish live. The role of temperature has also been confirmed within D. labrax, while it failed to be significant in O. niloticus. In this paper, the influence of habitat, life stage, sex and weight on basal plasma cortisol levels is also discussed. Since some abiotic parameters were not included in the analysis, our study is a call to encourage scientists to systematically report other key factors such as dissolved oxygen or salinity to fully depict the temperature-cortisol relationship in fishes.

Feasibility of using bio-mimicking fish scale textures in LPBF for water drag-reducing surfaces

In this work, bio-mimicking fish scale textures are produced by LPBF and AlSi7Mg0.6 powder to reduce drag forces on nautical components. For this purpose, a surface texture inspired by the European bass skin was modelled and parametrized. Textures were applied over the external surface of purpose-designed specimens. Additive manufacturing quality of textures was assessed using focus variation microscopy to examine surface roughness as well as geometrical errors. Once the feasibility of producing the desired bio-mimicking surfaces was confirmed, the designed surface patterns were analysed in the computation fluid dynamics modelling environment. The behaviour of the surfaces was characterized in terms of drag force generated over a fixed dimension plate model. The most promising configuration was further investigated in a sensitivity analysis where variations in main stream velocity and in surface roughness are applied. Drag reduction was related to the lowering of the viscous component and was found to be in the order of 1–2%, with respect to a smooth surface, for free stream velocity of 2.5–5 m s−1 and average roughness smaller than the as-built condition. The results confirm that the modelled surfaces can be reproduced with sufficient geometrical fidelity, showing great promise for drag-reducing metallic components produced by additive manufacturing.

Effects of 17α-ethinylestradiol on the neuroendocrine gonadotropic system and behavior of European sea bass larvae (Dicentrarchus labrax)

ABSTRACT The widespread use of 17α-ethinylestradiol (EE2), and other estrogenic endocrine disruptors, results in a continuous release of estrogenic compounds into aquatic environments. Xenoestrogens may interfere with the neuroendocrine system of aquatic organisms and may produce various adverse effects. The aim of the present study was to expose European sea bass larvae (Dicentrarchus labrax) to EE2 (0.5 and 50 nM) for 8 d and determine the expression levels of brain aromatase (cyp19a1b), gonadotropin-releasing hormones (gnrh1, gnrh2, gnrh3), kisspeptins (kiss1, kiss2) and estrogen receptors (esr1, esr2a, esr2b, gpera, gperb). Growth and behavior of larvae as evidenced by locomotor activity and anxiety-like behaviors were measured 8 d after EE2 treatment and a depuration period of 20 d. Exposure to 0.5 nM EE2 induced a significant increase in cyp19a1b expression levels, while upregulation of gnrh2, kiss1, and cyp19a1b expression was noted after 8 d at 50 nM EE2. Standard length at the end of the exposure phase was significantly lower in larvae exposed to 50 nM EE2 than in control; however, this effect was no longer observed after the depuration phase. The upregulation of gnrh2, kiss1, and cyp19a1b expression levels was found in conjunction with elevation in locomotor activity and anxiety-like behaviors in larvae. Behavioral alterations were still detected at the end of the depuration phase. Evidence indicates that the long-lasting effects of EE2 on behavior might impact normal development and subsequent fitness of exposed fish.

Growth performance and quality indicators of European seabass (Dicentrarchus labrax) fed diets including refined glycerol

Glycerol is a by-product of the biodiesel industry with growing availability and applicability in animal feeds. However, its use as a source of energy in aquafeeds has only been investigated in a small number of fish species. The effects of dietary refined glycerol inclusion rate on growth performance, nitrogen and energy balances, and fish quality were investigated in juvenile European seabass. Twelve fish were assigned to each of the nine tanks and used to test the experimental diets in triplicate. The diets comprised 0, 25, or 50 g kg−1 of refined glycerol (G0, G25, and G50, respectively), being not isoenergetic, although having similar digestible protein-to-energy ratios (22 mg kJ−1). Fish were fed twice a day to apparent satiation for 90 days. The G25 group displayed a higher absolute feed intake and a higher weight gain than the G0 or G50 groups, although feed efficiency and the use of protein as an energy source were similar between the three groups. Seabass fed the G25 diet also displayed a higher specific growth rate than fish fed the G50 diet. Higher hepato-somatic and visceral lipid-somatic indices of seabass were observed with increased levels of dietary glycerol, although proximal body composition remained similar across groups. The apparent digestibility coefficients for dry matter, crude protein, and energy increased with increasing dietary glycerol inclusion rate, whereas the apparent lipid digestibility coefficient was highest for the G25 group. No differences in the energy retained as protein, nitrogen efficiency, and total ammonia excretion rate were detected between seabass fed the different diets. At the end of the growth trial, physical and microbiological quality parameters of the skin and gill surfaces were assessed after 1 and 10 days of storage on ice. Fish quality decreased with storage time but was not affected by the dietary glycerol inclusion rate. In summary, the inclusion of refined glycerol in seabass diets may have economic benefits for feed manufacture and a positive effect on growth performance but does not change the efficiency of protein utilization in this carnivorous species.

Maximising performance and phosphorus utilisation of warm water fish through phytase supplementation

Phosphorus (P) is a critical mineral nutrient for fish but its availability in plant-based aquafeeds is usually low. To avoid its over-supplementation and the consequent increase of feed cost, excretion and, ultimately, environmental pollution, phytase supplementation has been used as a strategy to improve the bio-availability of P present in plant-based feeds as well as overall nutrient digestibility. This study assessed the efficacy of a new generation bioengineered microbial phytase (HiPhorius™) on the growth performance, whole-body nutrient retention, nutrient digestibility, and P excretion of Nile tilapia (Oreochromis niloticus), European seabass (Dicentrarchus labrax), and gilthead seabream (Sparus aurata). In the trial, the fish were fed diets enriched with plant-protein rich diets. Five dietary treatments were tested over 94 days: a control diet (CTRL), three diets supplemented with phytase at graded doses (500, 1000, and 2000 FTY/kg feed), and a diet supplemented with either dicalcium or monocalcium phosphate (DCP/MCP). Results showed that feeds supplemented with the phytase led to a significant dose-dependent increase of final body weight, specific growth rate, and protein efficiency ratio (FBW, SGR, PER), and a significant reduction of FCR, in comparison to the CTRL treatment. Supplementation with the phytase also notably reduced P excretion down to 23.37 ± 1.69, 28.46 ± 4.07, and 18.86 ± 1.05 mg/kg/day of P excretion for Nile tilapia, European seabass, and gilthead seabream, respectively, as compared to the treatment with inorganic P supplementation (118.82 ± 3.87, 127.81 ± 2.58, and 117.09 ± 8.15 mg/kg/day of P excretion for Nile tilapia, European seabass, and gilthead seabream, respectively). Overall, results show that the phytase tested here is an effective strategy to contribute to the economic and environmental sustainability of aquaculture production in different fish species.