Sea Bass Dicentrarchus Labrax Research Articles

Morphological and molecular characterization of Henneguya cardii n. sp. (Cnidaria: Myxosporea) from the bulbus arteriosus of European seabass Dicentrarchus labrax (Teleostei: Moronidae).

A new species of Myxobolidae, Henneguya cardii n. sp., is described infecting the European seabass Dicentrarchus labrax, a fish of high commercial value intensively cultivated in southern Europe. Henneguya cardii n. sp. was found in the bulbus arteriosus and spleen with a prevalence of infection of 13.5%. In the heart, it forms irregular whitish plasmodia measuring 1 mm in size. Mature myxospores are broadly obovoid in frontal view and ellipsoidal in lateral view, with 2 equal caudal appendages. Polar capsules are ovoid and symmetric, with 3–4 polar tubule coils. Myxospores measure 10.2 ± 0.6 (8.8–11.6) μm in length, 8.0 ± 0.7 (5.3–8.8) μm in width and 5.6 ± 0.2 (5.1–6.4) μm in thickness. Caudal appendages are 36.6 ± 3.2 (27.4–42.9) μm long. Total spore length is 47.6 ± 3.2 (41.2–53.2) μm. Polar capsules measure 4.0 ± 0.2 (3.4–4.6) by 2.2 ± 0.1 (1.9–2.6) μm. Small subunit ribosomal RNA-based tree topologies position H. cardii n. sp. within a lineage of marine myxobolids that is mostly comprised of other Henneguya species. Host-relatedness is reinforced as the main evolutionary driver for myxobolids, with the positioning of H. cardii n. sp. further suggesting tissue tropism as another important evolutionary driver for marine heart infecting Henneguya. Nonetheless, the inner complexity of this lineage suggests that identification of the evolutionary patterns driving its phylogeny will require discovery of the true diversity of marine myxobolids.

Fish dispersal from a sabotage-mediated massive escape event

Farm sabotage can cause massive fish escape events with significant ecological and socio-economic risks. This study examined the fate of Mediterranean seabass Dicentrarchus labrax escapees following a large-scale escape event caused by sabotage in the Western Mediterranean Sea. We monitored the escapee density and size structure over 3 mo after the escape at increasing distances from the escape point, up to 45 km away. Fish density adjacent to the escape location 5 d after the sabotage was, on average, 114 ± 44.7 (SE) fish per 100 m2. Our analyses showed that fish density decreased by 17% for every km away from the location, dropping to 2 and 1% after 1 and 2 mo, respectively, following the escape event. As escapee density declined throughout time and space, the size distribution of seabass shifted towards larger sizes. The rapid decrease in fish densities highlights the need for contingency plans focusing on fishing efforts in the coastal areas near the escape location (<20 km) within the first 24 h. These results are paramount to mitigating the risks associated with escape events cost-effectively. We emphasise the importance of sabotage prevention measures, such as security systems that can quickly detect intruders and trigger an immediate response to deter them. Additionally, enforcing appropriate sanctions based on the severity of the damage caused could help to discourage future sabotage attempts.

Molecular characterization of Lernathropus kroyeri from intensive aquaculture and pathophysiology of infested sea bass

The copepod Lernathropus kroyeri constitutes one of the major parasites for the Mediterranean aquaculture, infesting the sea bass Dicentrarchus labrax causing thus disruptions of growth performance and occasionally mortalities. Despite the large spread and the high frequency of this parasite in mariculture farms of Eastern Mediterranean, L. kroyeri genetic profile from aquaculture as well as the pathophysiological response of D. labrax have not been studied so far. Keeping this in mind, in the present study we investigated the L. kroyeri infestation on D. labrax from two farms in Greece, examining both healthy and heavy parasitized individuals. Assays included histopathology, phylogenetic reconstruction of the parasite and physiological response of the fish by the means of antioxidant, inflammatory metabolic and stress related gene expression analysis at both mRNA and protein levels. Genetic analysis indicated that L. kroyeri composes a monophyletic group, highly phylogenetically distant from other congeneric groups. Heavy infested D. labrax witnessed a significantly increased immune response that further led to oxidative stress and metabolic alterations. Overall, our results demonstrate the, seasonally independent, high infestation of this parasitic copepods, which continue to affect Mediterranean intensive aquaculture systems.

Will most suitable spawning grounds for coastal fishes be impacted by climate change? A larval drift modelling approach

For many fishes, their early life stages are transported (passively) by currents between spawning areas and coastal nurseries, but also potential dispersal towards new habitats. Therefore, species have developed strategies to enhance the recruitment success, including the selection of appropriate spawning grounds. However, increased temperature due to climate change may lead to changes in hydrodynamics, shorter larval drifts, and earlier spawning, and consequently the location of the most suitable spawning grounds may change. We investigated whether the location of the most favourable spawning areas (allowing higher rates of larvae reaching coastal nurseries) was stable over time, and if differences could be found between environmentally contrasted years. We used a larval drift model taking into account hydrodynamics, larval characteristics and behaviour for three commercially exploited fish species (sole Solea solea, flounder Platichthys flesus and seabass Dicentrarchus labrax) in the Western Europe (encompassing the Bay of Biscay, the Celtic Sea and the English Channel). According to our model, we conclude that despite contrasting environmental conditions, the location of spawning grounds allowing the best chance of recruitment to nurseries for the offspring was fairly similar. However, even if the location of the main spawning grounds is stable over time, their relative effectiveness varies greatly between years. This would suggest that natural selection may favour the emergence of homing behaviour. This stability in this fish essential habitat location could facilitate protection measures. Going further, it could be interesting to study the variations occurring in spawning grounds (in terms of recruitment success, and retention/dispersion) during the course of a spawning season.

Characterization of a New Toti-like Virus in Sea Bass, Dicentrarchus labrax.

The European sea bass Dicentrarchus labrax is the main species reared in Mediterranean aquaculture. Its larval stage, which is very sensitive and highly affected by sanitary and environmental conditions, is particularly scrutinized in hatcheries. Recently, a Mediterranean sea bass farm had to deal with an abnormal increase in mortality, especially between 20 and 35 days post-hatching (dph). Biological investigations led to the observation of cytopathic effects on three different fish cell lines after almost 3 weeks of culture at 14 °C in contact with homogenized affected larvae, suggesting the presence of a viral agent. High-throughput sequencing revealed a 6818-nucleotide-long RNA genome with six putative ORFs, corresponding to the organization of viruses belonging to the Totiviridae family. This genome clustered with the newly described and suggested Pistolvirus genus, sharing 45.5% to 37.2% nucleotide identity with other piscine toti-like viruses such as Cyclopterus lumpus toti-like virus (CLuTLV) or piscine myocarditis virus (PMCV), respectively. Therefore, we propose to name this new viral agent sea bass toti-like virus (SBTLV). Specific real-time RT-PCR confirmed the presence of the viral genome in the affected larval homogenate from different production batches and the corresponding cell culture supernatant. Experimental infections performed on sea bass fingerlings did not induce mortality, although the virus could be detected in various organs and a specific immune response was developed. Additional studies are needed to understand the exact involvement of this virus in the mortality observed in hatcheries and the potential associated cofactors.

Effects of Short-Term Intermittent Fasting on Growth Performance, Fatty Acids Profile, Glycolysis and Cholesterol Synthesis Gene Expression in European Seabass Dicentrarchus labrax

The present study was applied to evaluate the effects of alternate feeding and feed restriction on gene expression, growth, proximate composition and biochemical indices in European seabass, Dicentrarchus labrax. Fish were randomly divided into six indoor tanks with 90 fish per tank in a recirculating aquaculture system. Two feeding strategies were applied, in which the first group was fed daily to satiation and the second was intermittently fed (8 days feeding to satiation–2 days starvation) for 40 days. At the end of the experiment, outlier fish were sorted as fast growers (FG) and slow growers (SG) according to their final body weight. The differential gene expression tested was related to glycolysis (pk, ldha, hk, g3pdh, eno1 and alda), fatty acid metabolism (lpl and acc) and cholesterol synthesis (7dhcr and sqle). In addition, muscle ldha and gpi expressions were positively correlated with fish weight. The concentrations of glucose, triglycerides, cholesterol and non-esterified fatty acids (NEFA) were not affected by the dietary treatments. Glucose and NEFA differed significantly between SG and FG fed groups. Overall, the physiological responses of glucose and fatty acid metabolism in fish, as recorded by gene expression assays, were triggered by minor interventions in feeding rather than the different growth rates. Expression of specific genes and biochemical parameters could be used as potential biomarkers to improve aquaculture practices and benefit fish husbandry through selective breeding, feeding strategies and farm management. The study provides new insights on the impact of intermittent feeding of European seabass, with gene markers and their potential effects, for European seabass aquaculture.

Compositional and metabolic responses of European seabass (Dicentrarchus labrax) to a dietary gradient of long-chain (≥ C20) polyunsaturated fatty acids

Decrease in the inclusion of fish oil (FO) in current aquafeed formulations reduces the availability of omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA) to marine fish like the European seabass Dicentrarchus labrax. Here we investigated the compositional and physiological responses of European seabass to a dietary gradient of n-3 LC-PUFA. Six isoenergetic and isonitrogenous diets (D1-D6) were fed to triplicate groups of juvenile seabass (23 g), containing blends of FO and vegetable oil (VO) that resulted in a gradient of n-3 LC-PUFA varying from 0.23 to 3.40% of diet as fed. Sampling was carried out after four months feeding and biochemical composition, as well as lipid metabolic gene expression in liver and mid-intestine analysed. The only effect of diet on proximate composition was a decrease in hepatic lipid content as dietary n-3 LC-PUFA increase whereas, in contrast, fatty acid (FA) compositions of both tissues were substantially modified by diet. Concentrations of LC-PUFA biosynthesis intermediates decreased in both tissues as dietary n-3 LC-PUFA increased with some preference detected towards n-6 FA. Two genes, namely fads2 and igf1, were moderately influenced by dietary VO in liver while genes involved in lipogenesis (srebp1, srebp2 and fas) and LC-PUFA biosynthesis (fads2 and elovl5) were markedly down-regulated, in mid-intestine of seabass in response to increasing dietary n-3 LC-PUFA. The expression of genes of β-oxidation (ppara, cpt1a and fabp1) did not vary among treatment. Collectively, our data suggest that the nutritional regulation of key lipid metabolic genes in European seabass was more pronounced in mid-intestine than in liver. Overall, when compared to a previous study of similar design in gilthead seabream (Sparus aurata), the European seabass seems less sensitive to a dietary gradient of vegetable oil.

Heterogeneity of otolith chemical composition from two-dimensional mapping: Relationship with biomineralization mechanisms and implications for microchemistry analyses.

Although otoliths are widely used as archives to infer life-history traits and habitat use in fishes, their biomineralization process remains poorly understood. This lack of knowledge is problematic as it can lead to misinterpretation of the different types of signals (e.g., optical or chemical) that provide basic data for research in fish ecology, fisheries management, and species conservation. Otolith calcification relies on a complex system involving a pericrystalline fluid, the endolymph, whose organic and inorganic compositions are spatially heterogeneous for some constituents. This property stems from the particular structure of the calcifying saccular epithelium. In this study, we explored the spatial heterogeneity of elemental incorporation in otoliths for two species of high economic interest, European hake Merluccius merluccius (L. 1758) and European sea bass Dicentrarchus labrax (L. 1758). Two-dimensional mappings of chemical elements were obtained using UV high-repetition-rate femtosecond laser ablation (fs-LA) system coupled to a high-resolution inductively coupled plasma sector field mass spectrometer analyses on transverse sections of sagittae. Results highlighted a clear asymmetry between proximal (sulcus) and distal (antisulcus) concentrations for elements such as magnesium (Mg), phosphorus (P), manganese (Mn), and potassium (K) with concentration gradient directions that varied depending on the element. Strontium (Sr) and barium (Ba) did not show a proximo-distal gradient. These results are discussed in light of current knowledge on the endolymph composition and the mechanisms that lead to its compartmentalization, highlighting the need for further research on otolith biomineralization. Operational implications for studies based on otolith chemical composition are also discussed with emphasis on advice for sampling strategies to avoid analytical biases and the need for in-depth analyses of analytical settings before comparing otolith signatures between species or geographical areas.

Effect of Female Weight on Reproductive Performance of European Seabass Dicentrarchus Labrax

Effect of Female Weight on Reproductive Performance of European Seabass Dicentrarchus Labrax

Physiological stress responses of European seabass Dicentrarchus labrax related to changing operations of floating net cages in intensive farming conditions at the Moroccan M'diq bay.

The present study purposed to quantify and compare in-situ the primary and secondary physiological stress responses, related to the operation of floating net-cages changing, in both sub-adults (523 days post hatching) and adults (916 dph) European sea bass Dicentrarchus labrax, under intensive farming conditions in the Moroccan M'diq Bay. Levels of cortisol, glucose, total cholesterol, total protein and lactate, as well as the percentage of hematocrit were measured before and after stress. The results showed significantly elevated levels of cortisol and blood glucose in both age groups, while total cholesterol and protein levels were unaffected. In fact, blood lactate was significantly reduced in sub-adults, while in adults this parameter was not affected by the operation. However, the hematocrit percentages measured after the operation were significantly higher than those found before the operation in both groups of fish, which is linked to the increased rate of oxygen renewal by the new net cages and the lower water temperature inside the cages. With regard to the age-specific response during this essential operation - before and after the operation - plasma cortisol, blood glucose and lactate concentrations, as well as plasma total protein levels, were significantly higher in sub-adults than in adults. It is concluded that aquaculture practices such as changing the aquaculture net-cage could have repercussions in terms of the classic physiological responses to stress in D. labrax. This article is protected by copyright. All rights reserved.

Residency, home range and inter-annual fidelity of three coastal fish species in a Mediterranean coastal lagoon

In the Gulf of Lion (NW Mediterranean), fish species such as gilthead sea bream Sparus aurata, European seabass Dicentrarchus labrax, and salema Sarpa salpa show seasonal occupation of coastal lagoons, presumably as feeding grounds during their adult life stage. The role of the lagoons in these species' life cycles remains unknown, particularly with respect to their residency, space-use, and inter-annual fidelity. Using acoustic telemetry, the movements of 72 seabream, 58 seabass, and 81 salema were monitored over four years within Prévost Lagoon (Hérault Department, Occitania Region), to characterize (1) the main seasonal patterns of space use inside the lagoon and (2) their annual migrations between the lagoon and the sea. Overall, all three species were highly resident in the lagoon during the spring/summer foraging season; seabass was the only species that also displayed high residency to the lagoon throughout the winter breeding season. The three species showed differences in their space use, although they all mainly inhabited the deep lagoon centre and adjacent shellfish farms, with very small individual home ranges (mean ± SD, 0.12 ± 0.06 km2 over all species). All species showed some inter-annual fidelity to the lagoon (>43% at minimum for seabream) although these fidelity rates were probably underestimated due to fishing mortality, which is probably high during the winter breeding season. Overall, this study reveals that coastal lagoons are key foraging habitats for these species in the Gulf of Lion. The high residency and inter-annual fidelity suggest that any increase of anthropogenic pressure within the lagoon could negatively impact these fish populations. Therefore, protection of such productive habitats could be beneficial for long-term management of emblematic coastal species and the fisheries that they support.

An integrative study of morphological and molecular characterization of Diplectanum aequans (Diplectanidae: Monogenea) infecting European sea bass Dicentrarchus labrax (Linnaeus, 1758) from Turkish coasts

The diplectanid monogenean Diplectanum aequans (D. aequans) (Wegener, 1857) is one of the most important ectoparasites in the wild and cultured European sea bass Dicentrarchus labrax (Dic. labrax) (Linnaeus, 1758) worldwide. Presently, there is no information on the molecular data of D. aequans from Turkish coasts. In the present study, diplectanid monogeneans were collected from wild and cultured Dic. labrax in the Black Sea (FAO area 37.4.2) and Aegean Sea (FAO area 37.1.3) coasts of Türkiye, morphologically identified, and genetically characterized by sequencing of 28S rRNA and 18S rRNA fragments. The collected diplectanids were unambiguously identified as D. aequans based on detailed morphological features and sequence characterization of partial 28S rRNA and 18S rRNA genes. The overall prevalence and mean intensity of D. aequans were 100% and 15.1, respectively. This study reports first information of molecular (28S and 18S rRNA) evidence of D. aequans from Dic. labrax in the Turkish coasts. The new 18S and 28S rRNA sequences for D. aequans isolated from the Black Sea and Aegean Sea are genetically characterized. The 28S and 18S rRNA sequences of D. aequans can be used to resolve the phylogenetic positions of species found in the family Diplectanidae from the Black and Mediterranean Sea.

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

European sea bass Dicentrarchus labrax (Moronidae), which has a high commercial value, is mainly produced in the Mediterranean region. Prolactin (PRL) is a member of the helix bundle protein family that is secreted in the anterior pituitary gland and has a significant role in osmoregulation and growth in teleost fish. In this study, we investigated the genetic variation of the partial sequence of 3rd, 4th introns, and 4th exon regions of the PRL gene in Dicentrarchus labrax and its association with growth traits that were reared in cage conditions. Two SNPs (g.484 A C, g.529 T C) and one 15 bp indel (insertion/deletion) have been found in the 3rd intron region of the PRL gene of Dicentrarchus labrax. A significant association has been identified between the total body weight and the genotypes for PRL g.529 T C locus (р 0.05). The heterozygote genotype of the PRL g.529 T C locus has a significantly higher total body weight than the other genotypes in the population (p 0.05). Association analysis indicated that this SNP in the PRL gene is correlated with growth traits and could be used for genomic selection programs in Dicentrarchus labrax breeding.

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)

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.

Effects of phthalates on marine organisms: cytotoxicity and genotoxicity of mono-(2-ethylhexyl)-phthalate (MEHP) on European sea bass (Dicentrarchus labrax) embryonic cell line.

Mono-(2-ethylhexyl) phthalate (MEHP) represents a toxicological risk for marine organisms due to its widespread presence in aquatic environments. MEHP effects on cell viability, cell death and genotoxicity were investigated on the DLEC cell line, derived from early embryos of the European sea bass Dicentrarchus labrax L. A dose-dependent cytotoxic effect, with no induction of necrotic process, except at its highest concentration, was observed. Moreover, chromosomal instability was detected, both in binucleated and mononucleated cells, coupled with a minor inhibition of cell proliferation, whereas genomic instability was not revealed. To our knowledge, the overall results suggest the first evidence of a possible aneugenic effect of this compound in the DLEC cell line, that is the induction of chromosomal loss events without the induction of primary DNA damage. MEHP should be considered more harmful than its parent compound DEHP, because it induces genomic instability in the DLEC cell line without triggering cell death.

A simulated marine heatwave impacts European sea bass sperm quantity, but not quality.

Rapid environmental changes will be the major challenge that most biota will have to deal with in the near future. Extreme events, such as marine heatwaves, are becoming more frequent and could be spatially uniform at a regional scale for a relatively long period of time. To date, most research studies on heatwaves have focused on sessile organisms, but these extreme events can also impact mobile species. Here, a 3-week marine heatwave was simulated to investigate its effects on the male reproductive performance of a Mediterranean Sea emblematic species, the European sea bass Dicentrarchus labrax. Males from the control condition (c. 13°C) produced significantly more sperm than those exposed to a relatively warm thermal treatment (c. 16°C). Nonetheless, neither the percentage of motile spermatozoa nor most of the other sperm motility parameters were significantly affected by the rearing temperature over the whole period. Overall, the results of this study suggest only moderated effects of a potential winter heatwave on the reproductive performance of male European sea bass.

Diseases problems in cluttered sea bass Dicentrarchus Labrax reared in cages from Fingerlings until marketing size in Mariout Valley at King Mariout in Alexandria province

This study aimed to determine and identify the common bacterial infection in different stages of cultured sea bass during the different season. In addition Eexperimentally infected the sea bass with the Vibrio alginolyticus and Vibrio parahemolyticus. The aquarium trial was carried out with European seabass (Dicentrarchus labrax) in private fish farm at Borg El-Arab, Alexandria governorate Egypt. At total 50 of seabass was used during the study. The study lasted 10 weeks, starting with 50 ± 5 gram /fish. Prior to the start of the trial, the fish were fed with a commercial diet (45 percent CP, crude protein). Water quality parameters were monitored during fish acclimatization and throughout the trial. Water temperature, pH and dissolved oxygen remained within acceptable ranges for marine production during the trial. Our study concluded that, Vibrio alginolyticus and Vibrio parahemolyticus causes a great losses in cluttered sea bass Dicentrarchus Labrax reared in cages The presence of histopathological lesions in the internal organs clearly explained the septicemic nature of Vibrio infection. Altogether, the full confirmation of Vibrio infection ought to incorporate, examination of fishes for the visible clinical signs, postmortem examination, isolation of the causative agent using specific media and biochemical tests, and histopathological examination of the internal organs as a proof of septicemic nature of the Vibrio infection. The sensitivity test revealed sensitive to ciprofloxacin (Cipro 5μg), novobiocine (NV 30 μg), intermediate sensitivity was found to Oxytetracycline (OT 30 μg) while, the resistance was observed to amoxicillin (Aml 10 μg) and colisitine sulphate (CT 10 μg)

Primary and Secondary Physiological Stress Responses of European Sea Bass (Dicentrarchus labrax) Due to Rearing Practices under Aquaculture Farming Conditions in M'diq Bay, Moroccan Mediterranean: The Case of Sampling Operation for Size and Weight Measurement.

Globally, aquaculture contributes to sustainable food and nutritional stability. However, stress conditions constitute a major threat affecting farmed-fish welfare and fish farms’ performances. In this regard, the present study was aimed at measuring and comparing in-situ (offshore) the physiological stress responses caused by recurrent sampling operations for length−weight measurement. Studied fish were European sea bass Dicentrarchus labrax sub-adults and adults reared in intensive farming conditions in M’diq Bay, on the Moroccan Mediterranean coast. The physiological stress response was evaluated by measuring blood biomarkers, including cortisol, glucose, lactate, total cholesterol and total proteins levels, and hematocrit percentage. The hypercortisolemia, hyperglycemia, hyperlactatemia and hypoproteinemia detected in the post-sampling state in both age groups of D. labrax indicated stress tendencies and a high sensitivity to aquaculture practice-related stress factors, with major and minor responses detected in the same age and same stress conditions. It is also interesting to note that the fish age and the time-course of the sampling operation had a statistically significant effect in terms of the physiological response (with p < 0.01 and p < 0.001, respectively). In conclusion, the present study showed that sea bass subjected to various stressful situations in intensive farming conditions displayed a physiological stress response specific to its age, to the individual status, as well as to the duration of stressor.