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Age, growth, and mortality of European Seabass (Dicentrarchus labrax) were studied from a small-scaled fishery of Bardawil lagoon, (North Sinai, Egypt). 181 specimens (16.6 to 35 cm total Length and 39.8 to 367.2 g total weight). The relationship between length and weight was W = 0.0054L3.1428. Age was determined by otoliths and age groups I to IV years were observed. Growths in length and weight at the end of each year were calculated. The growth parameters of von Bertalanffy equation were calculated as (L∞ = 48.69 cm, K = 0.1677 yr -1 and t0 = -0.447 yr -1). Growth performance index was calculated (φ = 2.60 for length and 1.25 for weight). Mortality rates were 0.867 yr-1, 0.25 yr1and 0.617 yr-1 for total, natural and fishing mortality, respectively. The currently exploitation rate E = 0.712 yr-1 indicating that, the population of this species is being heavily exploited.

The study aims to investigate the monthly changes in the prices of culture fish that were sold in retail fish outlets in Sinop in 2019 and determine the correlations between the prices of the species. The retail outlets were determined using stratified sampling and divided into three groups as I (high), II (medium), and III (low) with respect to their product range and sale amounts. Each sale group was represented by two independent retail outlets. The prices were determined twice a month at the same time of the day during the study. The retail outlets were determined to sell sea bream (Sparus aurata), sea bass (Dicentrarchus labrax), and rainbow trout (Oncorhyncus mykiss) culturing of which are carried out in Turkey. The difference in the monthly prices of the species was not statistically significant. There was a positive and moderate relationship between the prices of sea bream and sea bass (r=0.69), a positive and strong relationship between the prices of sea bass and trout (r=0.85), and a positive and strong relationship between the prices of sea bream and trout (r=0.71).

The purpose of this study was to determine the phylogenetic relationships among the primary betanodavirus strains circulating in Tunisian coastal waters. A survey was conducted to investigate nodavirus infections at 15 European sea bass Dicentrarchus labrax and gilthead sea bream Sparus aurata farming sites located along the northern and eastern coasts of Tunisia. The primary objective of the study was to create epidemiological awareness of these infections by determining phylogenetic relationships between the main betanodavirus strains circulating during the period 2012-2019, using RNA1 and/or RNA2 genome segments. Approximately 40% (118 of 294) tissue pools tested were positive for betanodavirus. Positive pools were distributed across all of the sampling sites. While fish mortalities were always correlated with the presence of virus in sea bass, a severe outbreak was also identified in sea bream larvae in 2019. Phylogenetic analysis revealed that almost all Tunisian strains from both sea bass and sea bream irrespective of outbreaks clustered within the RGNNV genotype. It is noteworthy that samples collected during the 2019 outbreak from sea bream contained both RNA1 and RNA2 fragments belonging to the RGNNV and SJNNV genotype, respectively, an indication of viral genome reassortment. To our knowledge, this is the first report of reassortant betanodavirus in Tunisia.

The European bass (Dicentrarchus labrax) support high value commercial and recreational fisheries, however the Spawning Stock Biomass (SSB) of the northern Atlantic stock (ICES divisions 4.b–c, 7.a, and 7.d–h) has rapidly declined to an unsustainable level. The decline in SSB has been attributed to high fishing pressure combined with poor recruitment. By tracking juvenile fish their spatial ecology can be identified, and appropriate fisheries management policies designed to boost recruitment can be implemented. Using acoustic telemetry 146 sub-adult European bass (25.2–60 cm fork length) were tracked for up to 370 d across three sites in the southwest of the UK. Tagged fish were detected 2 724 548 times (Range: 166–106 393 detections per fish). Linear modelling estimated tagged fish were resident within 2.4–20.1 km of the site where they were first caught for 42.9–75.5% of the year. Some fish were however resident throughout summer and winter. Individual fish were also tracked moving up to 317 km to other coastal sites, 81% of which returned to their original capture site. Fisheries management should account for the high site fidelity displayed by juveniles and sub-adults of this species and coastal nursery sites should be considered essential habitat.

Skeletal abnormalities in farmed fish are one of the main problems that negatively affect the production enterprises in terms of economic, biological and animal health. Fish with skeletal deformities in hatcheries are considered as non-economic individuals and are therefore detected and removed manually from the production tanks, which is a time consuming and laborious work for the facilities. Since the formation of abnormalities in the skeletal structure of the fish during the early growth period cause reduced swimming ability or speed that prevent fish to compete during feeding. Further, since deformed fish has no market value, even the share of a small amount of feed among deformed fish will reduce the feed conversion for the market targeted individuals within the culture tank that in terms may increase the production cost per fish. Therefore, in culture conditions it is important to remove the deformed fish from the tank environment by quickly determining those fellows at the early stage of growth. The present study evaluates the effects of water velocity on swimming behavior of juvenile seabass (Dicentrarchus labrax) and provides a solution for a rapid identification -and mechanical removal of deformed fish from the culture environment by using swimming speed slowdown -and behavioral differences as an indicator of deformation.

In this study, low-cost and eco-friendly hydroxyapatite (FS-HAp) particles were obtained from the raw fish scales of European Seabass (Dicentrarchus labrax), and used as adsorbent material to remove Pb(II) ions from solutions. For this purpose, experiments were carried out in the aqueous solutions prepared at different Pb(II) concentrations to determine optimum pH, adsorbent concentration, reaction time and initial Pb(II) concentration. Optimum removal conditions for Pb(II) adsorption onto FS-HAp were determined as pH 4.0, adsorbent concentration of 7.5 g/L, reaction time of 60 min, and initial Pb(II) concentration of 50 mg/L. Under these experimental conditions, the maximum Pb(II) removal was obtained as 97%. According to results of the study, hydroxyapatite obtained from fish scales was found to be highly efficient material to remove Pb(II) ions from water by adsorption method in order to reach high efficiency values when compared with many adsorbent materials.

Infestation by parasitic copepods is a substantial problem in the cage culture of European sea bass (Dicentrarchus labrax). The Copepoda parasite, Lernanthropus kroyeri (Lernanthropidae), is one of the threats to the mariculture of sea bass. In the present study, we evaluated the data of abundance for L. kroyeri pre-adults and adult males (PAAM) and ovigerous adult females (AFo ) to estimate the internal infection pressure (IIP) in the same cage environment. The sea bass infested by L. kroyeri was collected from grow-out sea cages located in Gulluk Bay (Turkey) in September and October 2019. Mean fish weight and length of sea bass were 75.79 ± 1.66 g and 21.40 ± 0.56 cm, respectively. The fixed lag method was used to predict the abundance of L. kroyeri adult females. The overall prevalence of L. kroyeri was 60%. The mean abundance of PAAM and AFo varied from 0.8 ± 0.24 to 2.5 ± 0.67 and 2.9 ± 0.40 to 4.3 ± 0.55, respectively. The abundance of AF was strongly correlated with PAAM. The pattern of AFo and PAAM was interpreted as an indication of the continuous infestation of L. kroyeri on sea bass. Our results showed that the correlation of AFo abundance for five consecutive weeks was significant, representing the main determinative factor for the continuity of the parasitic load. In our approach, internal infestation pressure is the quantitative estimation of the potential infective copepodids, which are mainly characterized by AF abundance and the prevalence. We predicted that the internal infestation pressure could be high, even exceeding the 50.000 × 106 potential infective copepodids for one sea cage with the fish density of 20 sea bass/m3 .

In this study, the relationship between color and the quality of fish was investigated. Additionally, how the color properties alter as a result of whether the fish is kept in cold water during the...

The microbiota of fish skin, the primary barrier against disease, is highly dynamic and modulated by several factors. In fish aquaculture, disease outbreaks occur mainly during early-life stages, with associated high economic losses. Antibiotic treatments sometimes remain the best option to control bacterial diseases, despite many reported negative impacts of its use on fish and associated microbiota. Notwithstanding, studies monitoring the effects of disease and antibiotic treatment on the microbiota of fingerlings are scarce. We sequenced the bacterial 16S rRNA V4 gene region using a metabarcoding approach to assess the impact of a mixed infection with Photobacterium damselae ssp. piscicida and Vibrio harveyi and subsequent antibiotic treatment with flumequine, on the skin microbiota of farmed seabass (Dicentrarchus labrax) fingerlings. Both infection and antibiotic treatment led to a significant increase in bacterial diversity and core microbial communities and impacted microbiome structure. Dysbiosis was confirmed by changes in the abundance of potential pathogenic and opportunistic bacterial taxa. Skin bacterial metabolic function was also significantly affected by flumequine administration, suggesting a detriment to fish skin health. Our results add to an increasing body of literature, showing how fish microbiome response to infection and antibiotics cannot be easily predicted.

Demand feeder is slightly different with an automatic feeder, it is altered to the appetite of fish because they can prefer which time they activate the feeder, also it triggered to produce a good growth performance and decrease the feed waste. Alternatively, some studies have been carried out for new method of automatic feeding system. Self-feeding system or previously familiar with the name of demand feeding system, is a system based on the learning ability of fish to activate the feeder and utilizing a feeding rhythm that may be controlled by the biological clock. At the past two decades, the development of self-feeding system is growing rapidly, from database, twenty eight studies with the most relevant data have been collected. The peak of paper published was in year 2000 with the most popular fish species was European sea bass (Dicentrarchus labrax, L.).

In this study, a feeding experiment was conducted using different rations (25%, 50%, 75%, and 100%) of wheat flour protein instead of fishmeal in fry fish (Dicentrarchus labrax) feeds. In the experiment, an average weight of 2.33±0.2 g juvenile seabass was used. Seabass fries were fed with the experimental feeds for 60 days. The experiment was designed in triplicates. At the end of the experiment, the growth parameters and fatty acid composition of fish fries were examined. As a result, it was statistically determined that the use of wheat flour protein at a high rate had a negative effect on the growth parameters of the fish. Significant changes in fatty acid composition were also observed.

In this study, Fe and Zn contents in the muscle of different fish species (Engraulis encrasicolus, Trachurus trachurus, Mullus barbatus, Mugil cephalus, Pomatomus saltatrix, Dicentrarchus labrax, Scomber scombrus, Sparus aurata) were determined using flame atomic absorption spectrometry (FAAS). The highest Fe and Zn contents among studied fish species were found in Engraulis encrasicolus (7.13 ± 0.19 mg/kg) and Sparus aurata (11.00 ± 0.28 mg/kg). The lowest Fe and Zn contents were determined in Dicentrarchus labrax (3.12 ± 0.09 mg/kg) and Pomatomus saltatrix (5.50 ± 0.05 mg/kg). Moreover, the results were evaluated considering the estimated daily intakes (EDI) of these elements for adults. The estimated daily intakes were varied from 0.0101 to 0.0231 mg/kg bw/day for Fe and 0.0178 to 0.0357 mg/kg bw/day for Zn in fish species. In addition, the hazard quotient (HQ) and the hazard index (HI) values were calculated for risk assessment, and it was determined that these values were below 1 for fish species.

The present work was done to elucidate the impact of water quality in private fish farm in Suez Canal area and agricultural drainage water supply source (sectors A and B), Samples of three different fish species: seabream (Sparus aurata), Seabass (Dicentrarchus labrax), and Meagre (Argyrosomus regius) (sectors C, D and E), on the fish physiology, blood picture, biochemistry and accumulation of heavy metals in flesh and gills of the reared fishes. It was found that, water temperature in the different fish farm sectors around the year were significantly different, however, the pH was slightly basic. In spite of the water dissolved oxygen was around the suitable limits, its minimum value was recorded in the fish farm sector (C). Nonetheless, in this fish farm the maximum levels of salinity and total dissolved salts were recorded. Similarly, the ammonia, nitrite and nitrate concentrations were revealed in this fish farm. The relative dominance of heavy metals in the pond's water of the three investigated fish farm sectors all over the period of the study was Fe, Cu, Pb and Cd. However, heavy metals are highly accumulated in fish flesh of all fish farm sectors than in its water column. The muscle content of the detected heavy metals which accumulate in all examined fish species muscle and gills not exceeded the permitted value suggested by FAO/WHO. Metal pollution index realized its minimum levels in water and fish tissue. It is obvious that, the levels of all heavy metals detected in water samples and S. aurata, D. labrax and A. regius muscle tissues (the edible portion of fish) were under the notified permissible limits. Some of the measured parameters slightly exceeded the permissible limits recommended by regulatory agencies

Black soldier fly larvae meal (BSFLM) has been successfully demonstrated as a promising fish meal (FM) replacer in diets of several fish species including European seabass (Dicentrarchus labrax). However, its impacts on antioxidant capacity, and immune responses of treated fish are still poorly understood. A 60-day feeding trial was carried out to evaluate the effects of partial substitution of FM with different levels of dry BSFLM on the antioxidative status, non-specific immunity, transcriptomic responses, and resistance of European seabass to the challenge with Vibrio alginolyticus. Four isoproteic (45%) and isolipidic diets were formulated by replacing 0.0%, 25%, 35%, and 50% of the dietary FM. Each diet was randomly assigned to four fish groups (in triplicates) (initial mean body weight, 12.1 ± 0.21 g) (20 fish per aquarium) (n = 240). Fish were fed three times daily to the apparent satiation. At the end of the feeding trial, serum antioxidant biomarkers such as malondialdehyde levels, and catalase, superoxide dismutase, and glutathione peroxidase enzyme activities were significantly increased in all BSFLM groups in a dose-dependent manner compared to the control group (P 0.05). The non-specific immune indices, including phagocytic activity, phagocytic index, serum lysozyme and respiratory burst activities were significantly elevated in BSFLM groups compared to those in the control group (P 0.05). Significant upregulation of the mRNA expression levels of hepatic heat shock protein 70, interleukin-1beta and interleukin-10 genes were observed in all BSFLM groups compared to the control group (P 0.05). Additionally, after the challenge with V. alginolyticus, the relative percent of survival was significantly elevated in fish groups fed on diets containing graded levels of BSFLM over the control group (P 0.05). Conclusively, the present study suggests the potential efficacy of partial replacement of dietary FM protein for up to 50% by BSFLM without negative effects on fish health with possible potentiation of the antioxidative status, and the immune responses of the European seabass.

A little knowledge still available for fish digenean, although some of them have pathogenic and economic importance. Fish morbidity and mortalities were reported in two fish farms culturing D. labrax fingerling with the primarily isolated parasites belonged to fish digenean trematodes. Therefore, this study was directed mainly to investigate the main causative digenean parasites. Additionally, the ecological water parameters were reported, and the anthelmintic efficacy using levamisole was evaluated. The prevalent digenean parasite was identified Digenean, Transversotrema haasi, an extra-intestinal digenean that was mainly isolated from gill and skin. The infected D. labrax exhibited abnormal external, and internal lesions indicative of deteriorating health status. The recorded infection rates were 48.67 and 38.67%, parasitic intensities, 6.14 and 2.4 and mortalities rates 28 and 19.33% in Manzala, and Wadi-mariot respectively. The recoded ecological parameters were ranged from 14.22 - 29.7 oC temperature, 7.49 - 8.36 pH, and 13.54 - 34.36 ppt for salinity. Besides, the in vitro therapeutic baths with levamisole were dose-dependent, with the highest anthelmintic efficacy at higher doses effective against digenean T. hassi. Higher anthelmintic efficacy was obtained at 70 µg/l levamisole concentration, the lowest mean viability 0.33, the highest parasitic mortality rate 81.81% occurred at the lowest exposure time. Although the anthelmintic efficacy of the levamisole bath has been proven, other friendly environmental agents of plant origin should be taken under consideration to avoiding potential environmental and human hazards.

The consumption of inadequately thermally treated fish is a public health risk due to the possible propagation of Anisakis larvae and their antigenic proteins, the causative agent of the zoonotic disease anisakidosis. The present study demonstrated the physiological and histopathological changes that accompanied an oral inoculation of crude extracts from fresh and thermally treated Anisakis Type II (L3) in Wistar albino rats. Nematode worms were isolated from the marine fish Dicentrarchus labrax. They were examined and taxonomically identified using light and scanning electron microscopy. The study was performed in 6 rat groups: a control group (I), a garlic oil (GO) inoculated group (II), a fresh L3 inoculated group (III), a thermally treated L3 inoculated group (IV), a fresh L3 + GO inoculated group (V), and a thermally treated L3 + GO inoculated group (VI). It was observed that rats inoculated with fresh and thermally treated L3 crude extracts showed abnormal oxidative stress markers associated with the destruction of normal architecture of spleen and thymus. GO produced a protective effect in rat groups inoculated with L3 extracts + GO administration via the amelioration of oxidative stress markers, which was confirmed by the marked normal structure of the organs’ histology. Cooking of L3 infected fish induced severe physiological and histopathological alterations compared to uncooked infected fish. The administration of garlic before and after fish eating is recommended to avoid the dangerous effect of anisakids, even if they are cooked.

A healthy gastrointestinal microbiota is essential for host fitness, and strongly modulated by host diet. In aquaculture, a current challenge is to feed carnivorous fish with plant-feedstuffs in substitution of fish meal, an unsustainable commodity. Plants have a limited nutritive value due to the presence of non-starch polysaccharides (NSP) which are not metabolized by fish. In this work we assessed the effects of NSP-enriched diets on European seabass gut microbiota and evaluate the selective pressure of plant feedstuffs towards gut microbes with NSP-hydrolytic potential, i.e. capable to convert indigestible dietary constituents in fish metabolites. Triplicate groups of European seabass juveniles were fed a fish meal-based diet (control) or three plant-based diets (SBM, soybean meal; RSM, rapeseed meal; SFM, sunflower meal) for 6 weeks, before recovering intestinal samples for microbiota analysis, using the Illumina’s MiSeq platform. Plant-based diets impacted differently digesta and mucosal microbiota. A decrease (p = 0.020) on species richness, accompanied by a decline on the relative abundance of specific phyla such as Acidobacteria (p = 0.030), was observed in digesta samples of SBM and RSM experimental fish, but no effects were seen in mucosa-associated microbiota. Plant-based diets favored the Firmicutes (p = 0.01), in particular the Bacillaceae (p = 0.017) and Clostridiaceae (p = 0.007), two bacterial families known to harbor carbohydrate active enzymes and thus putatively more prone to grow in high NSP environments. Overall, bacterial gut communities of European seabass respond to plant-feedstuffs with adjustments in the presence of transient microorganisms (allochthonous) with carbohydrolytic potential, while maintaining a balanced core (autochthonous) microbiota.

In this review, we summarize and discuss the trends and supporting findings in scientific literature on the gut mucosa immune role in European sea bass (Dicentrarchus labrax L.). Overall, the purpose is to provide an updated overview of the gastrointestinal tract functional regionalization and defence barriers. A description of the available information regarding immune cells found in two immunologically-relevant intestinal compartments, namely epithelium and lamina propria, is provided. Attention has been also paid to mucosal immunoglobulins and to the latest research investigating gut microbiota and dietary manipulation impacts. Finally, we review oral vaccination strategies, as a safe method for sea bass vaccine delivery.

The pharmacokinetic properties and residue elimination of florfenicol (FLO) and its amine were investigated in European seabass Dicentrarchus labrax at 24°C. The trial mainly included analysis of FLO in plasma after a single dose dietary administration of 10 mg/kg and in muscle plus skin following a multiple dosing (10 mg kg−1 day−1 for 7 days) to estimate pharmacokinetics and residue depletion, respectively. The maximum plasma concentration of FLO was measured to be 1.64 μg/ml, 4 hr post administration. The elimination half‐life (t 1/2b) and the area under the concentration‐time curve extrapolated to infinity (AUC0‐∞) were calculated to be 13.0 hr and 34.7 μg h−1 ml−1, respectively. Withdrawal times of FLO and its amine were calculated to be 46.3 degree‐days, indicating a fast removal from the edible tissues of treated European seabass. Overall, FLO can be considered as a potentially efficient antibacterial agent for farmed European seabass provided that additional efforts will be devoted towards its in vitro and clinical efficacy., First pharmacokinetic study of florfenicol in European seabass providing insights to enhance treatment schedule of a promising “off label” antibacterial compound. Information is also provided regarding consumer's safety.

Background and objective In Egypt, Nile tilapia represents the main cultured type due to its economical price, palatability and easy culturing. This study was aimed to elucidate the pathogenicity of V. alginolyticus isolated from diseased sea bass and experimentally infected healthy Nile tilapia fish. Materials and methods Healthy Nile tilapia fish were injected I/P with V. alginolyticus isolated from diseased sea bass. Symptoms and mortality rates of infected Nile tilapia fish were recorded during the experimental period. Re-isolation of V. alginolyticus was done from infected tilapia fish by bacteriological methods. For confirmation the pathogenicity of Vibrio isolated either from marine fish or tilapia fish, PCR test was done using tdh and bla gens. Liver and kidney function tests with histopathological examinations of some organs were performed. Treatment trial was done according to the antibiotic sensitivity test. Results The isolated Vibrio is highly pathogenic to Nile tilapia fish causing deterioration in all parameters which finished by severe mortalities. Treatment with florfenicol, enrofloxacin, or oxytetracycline reduced the mortality rate and improved liver and kidney function parameters of infected Nile tilapia fish. Conclusion V. alginolyticus can infect both marine and fresh water fish inducing a high mortality rate. Treatment of infected fish with florfenicol, enrofloxacin, or oxytetracycline reduces the mortality rate.

The current study investigated the role of selenium (Se) nanoparticles on the growth performance, hemato-biochemical indices, antioxidative, and immune-related genes of European seabass (Dicentrarchus labrax). Therefore, fish with initial weight of 20.53 ± 0.10 g/fish were fed diets with 0, 0.25, 0.5, and 1 mg Se nanoparticles/kg diet for 90 days. The final body weight, weight gain, and specific growth rate of fish fed dietary nano-Se varying levels were significantly higher than the control with the highest performances and lowest FCR in the group of fish fed nano-Se at 0.5 mg/kg. The values of Hb, PCV, RBCs, and WBCs were significantly higher in fish fed varying levels of Se nanoparticles than fish fed the basal diets. The values of total serum protein and globulin were significantly higher in fish fed varying levels of Se nanoparticles than fish fed the basal diets. Additionally, globulin had higher value in the group of fish fed 0.25 and 0.5 mg nano-Se/kg than fish fed 1 mg nano-Se/kg (P 0.05). Phagocytic index, phagocytic, lysozyme activities were significantly higher in fish fed varying levels of Se nanoparticles than fish fed the basal diets in a dose dependent manner (P

International audience; Regulatory assessment of the effects of chemicals requires the availability of validated tests representing different environments and organisms. In this context, developing new tests is particularly needed for marine species from temperate environments. It is also important to evaluate effects that are generally poorly characterized and seldom included in regulatory tests. In this study, we designed an exposure protocol using European sea bass (Dicentrarchus labrax) larvae. We examined classical toxicological values (LCx) as well as behavioral responses. By comparing different hatching and breeding strategies, we defined the optimal conditions of exposure as non-agitated conditions in 24- or 48-well microplates. Our exposure protocol was then tested with 3,4-dichloroaniline (3,4-DCA), a recommended reference molecule. Based on our results, the 96 h LC50 for 3,4-DCA corresponded to 2.04 mg/L while the 168 h LC50 to 0.79 mg/L. Behavioral analyses showed no effect of 3,4-DCA at low concentration (0.25 mg/L). In conclusion, the present work established the basis for a new test which includes behavioral analysis and shows that the use of sea bass is suitable to early-life stage toxicity tests.

Barriers in the estuaries of the rivers prevent the immigration of glass eels (Anguilla anguilla) arriving on the European coast every spring. This leads to an unnatural accumulation of migrating glass eels below the barriers, and this may lead to additional losses in glass eels by piscivorous fish. The proportion of predation losses can be estimated using mark-recapture techniques and abundance estimates in combination with stomach content analysis of piscivorous fish. Nonetheless, whether tagging transparent glass eels increases predation risk and what the digestion rate of glass eel is in piscivorous fish are unknown. This study aimed to determine whether there is an increased predation risk for tagged glass eel; it also studies glass eel digestion status in piscivorous fish after appointed time frames. A laboratory experiment with 48 trials was conducted. Tagged (visible implanted elastomer, VIE) and untagged glass eels were exposed to small (19.1-24.4 cm) and large (31.9-43.5 cm) sea bass (Dicentrarchus labrax) during a 2 h trial. In 48% of the trials, successful predation was present and 13% showed clear predation attempts in which bass did not capture glass eels. No significant difference was found in predation rate between tagged and untagged glass eels and between red and blue tagged glass eels. Large sea bass predated more, but all sizes consumed glass eel under laboratory conditions. Stomach content analysis showed intact glass eel bodies 4-6 h after ending the 2 h trial and parts of glass eel bodies up to 16-18 h. This study showed that tagging does not increase predation in mark-recapture studies using VIE-tags in transparent glass eel. It also shows that the proportion of predation in relation to local glass eel abundance can be estimated if stomach content analysis is conducted within 4-6 h after predation.

Plastic pollution has become a global problem for marine ecosystems. Microplastics (MPs) are consumed by several marine organisms, including benthic and pelagic fish species that confuse them with food sources, thus contributing to bioaccumulation along the food chain. In addition to structural intestinal damage, ingestion of MPs represents a pathway for fish exposure to potentially hazardous chemicals, too. Most of them are endocrine disrupters, genotoxic or induce immune depression in fish. Accordingly, we assessed the combined toxicological effects of microplastics (MPs) and adsorbed pollutants by adding them to marine fish diet. European sea bass (Dicentrarchus labrax) juveniles were fed for 60 days with feeds containing polypropylene MPs, either virgin or contaminated with chemical pollutants (a blend of dichlorodiphenyldichloroethylene, chlorpyrifos, and benzophenone-3). The data demonstrated a synergic action of MPs and chemical pollutants to induce an inflammatory-like response in distal intestine of sea bass as shown by the up regulation of cytokine il-6 and tnf-α expression. Morphological analysis detected the presence of a focus of lymphocytes in anterior and posterior intestinal segments of fish fed with contaminants in the diet. With regard to microbiota, significant changes in bacterial species richness, beta diversity, and composition of gut microbiota were observed as a consequence of both pollutants and polluted MPs ingestion. These perturbations in gut microbial communities, including the reduction of beneficial lactic acid bacteria and the increase in potential pathogenic microorganism (Proteobacteria and Vibrionales), were undeniable signs of intestinal dysbiosis, which in turn confirmed the signs of inflammation caused by pollutants, especially when combined with MPs. The results obtained in this study provide, therefore, new insights into the potential risks of ingesting MPs as pollutant carriers in marine fish.

European sea bass (Dicentrarchus labrax) migrate towards habitats where salinity can reach levels over 60‰, notably in Mediterranean lagoons. D. labrax are genetically subdivided in Atlantic and Mediterranean lineages and have evolved in slightly different salinities. We compared Atlantic and West-Mediterranean populations regarding their capacity to tolerate hypersalinity with a focus on the involvement of the intestine in solute-driven water reabsorption. Fish were analyzed following a two-week transfer from seawater (SW, 36‰) to either SW or hypersaline water (HW, 55‰). Differences among lineages were observed in posterior intestines of fish maintained in SW regarding NKA activities and mRNA expressions of nkaα1a, aqp8b, aqp1a and aqp1b with systematic higher levels in Mediterranean sea bass. High salinity transfer triggered similar responses in both lineages but at different magnitudes which may indicate slight different physiological strategies between lineages. High salinity transfer did not significantly affect the phenotypic traits measured in the anterior intestine. In the posterior intestine however, the size of enterocytes and NKA activity were higher in HW compared to SW. In this tissue, nka-α1a, nkcc2, aqp8ab and aqp8aa mRNA levels were higher in HW compared to SW as well as relative protein expression of AQP8ab. For aqp1a, 1b, 8aa and 8b, an opposite trend was observed. The sub-apical localization of AQP8ab in enterocytes suggests its role in transepithelial water reabsorption. Strong apical NKCC2/NCC staining indicates an increased Na+ and Cl- reuptake by enterocytes which could contribute to solute-coupled water reuptake in cells where AQP8ab is expressed.

The quantitative and qualitative characteristics of faecal waste was studied in European seabass (Dicentrarchus labrax) fed diets with high inclusion of different feed ingredients (field peas, PEA; feather meal, FeM; sunflower cake meal, SFM; wheat dried distillers grain with soluble, WDG; corn gluten meal, CGM and soya protein concentrate, SPC), in two different experimental trials, in order to evaluate if different ingredients affect waste production. Each of the test ingredients was partially replaced with the basal mixture used in the control diet (CON). The ingredients were chosen for their varying levels of starch, protein, soluble and insoluble non-starch polysaccharide contents. Fish having an initial body weight of 120 g were used (20 fish/tank in triplicate groups) in both trials and were fed at 1.0% in trial I and 1.5% in trial II of their body weight for 40 days. Apparent digestibility coefficients (ADC) of dry matter (DM), nutrients (protein, fat, carbohydrate, and phosphorus) of the test diets were significantly altered between groups in trial I, with SFM showing the least ADC for DM, carbohydrate and phosphorus; starch ADC was the least in PEA but only DM digestibility and phosphorus availability were different in trial II. The quantity, recovery percentage, physical characteristics, appearance and chemical composition of the faeces were affected by the test ingredients. Carbohydrate fraction of the diet was the most influential in affecting the quantity and chemical composition of faeces produced. Increased inclusion of NSP rich ingredients (WDG, soluble or SFM, insoluble) resulted in higher faecal recovery percentage, despite higher faeces load. Overall, high inclusion of alternate ingredients affected quantitative and qualitative characters of the faecal waste in European seabass, which has implications for environmental sustainability of European seabass aquaculture.

The purpose of this study was to assess the acute and chronic effects of the macrolide azithromycin (AZI) on the European sea bass (Dicentrarchus labrax) early life stages. Azithromycin is a semi-s...

Viral encephalopathy and retinopathy (VER) is a serious neuropathological fish disease affecting in the Mediterranean aquaculture mainly European sea bass, Dicentrarchus labrax. It is well known that betanodaviruses are neurotropic viruses that replicate in nerve tissues, preferentially brain and retina. However, routes of entry and progression of the virus in the central nervous system (CNS) remain unclear. The role of four tissues-eye, oesophagus, gills and skin-as possible gateways of a betanodavirus, the redspotted grouper nervous necrosis virus (RGNNV), was investigated after experimental challenges performed on European seabass juveniles. The dispersal pattern of Betanodavirus at primarily stages of the disease was also assessed, using a real-time qPCR assay. The development of typical clinical signs of VER, the presence of characteristic histopathological lesions in the brain and retina and the detection of viral RNA in the tissues of all experimental groups ascertained that successful invasion of RGNNV under all experimental routes was achieved. Transneuronal spread along pathways known to be connected to the initial site of entry seems to be the predominant scenario of viral progression in the CNS. Furthermore, viraemia appeared only after the installation of the infection in the brain.

Cymothoid isopods cause serious infestations in fish that may adversely affect the aquaculture. Current study targeted investigating the enormous infestation of European sea bass Dicentrarchus labrax with cymothoid isopod, Nerocila species in a marine fish farm at Kafr El Sheikh Governorate, Egypt; accompanied with trials for treatment with malathion 57% at 0.15 and 0.30 mg/L concentrations and evaluation of the immune and antioxidants responses. For this purpose, 450 D. labrax were randomly collected alive during April 2020 and thoroughly examined for detection of external parasites. Malathion 57% treatment trial was carried out. Blood and tissue samples were collected from infested fish at zero-day (before malathion treatment) and at 24hrs, 48hrs, 3rd day, 4th day and 5th day (after malathion treatment). Isopods collected from infested fish were identified as N. orbigny and fish's external body surface and gills were the predilection sites. Both malathion concentrations were effective in eradicating N. orbigny and decreasing the isopod prevalence from 100 to 0% at the 5th day sampling point. Infested fish revealed improved hematological parameters (Erythrocyte counts, hemoglobin, and hematocrit readings), however leucocyte and differential cells counts showed significant decrease in infested fish. Immunological parameters (Lysozyme and IgM activities) decreased, but nitric oxide increased by time after malathion application. Nerocila is considered serious parasite in aquaculture that negatively affects fish's immune and antioxidative responses; and malathion denoted as a promising treatment to control N. orbigny in infested D. labrax.

In the present study, the start codon targeted (SCoT) technique was used for measuring the genetic variability between two fish species of family Moronidae (Dicentrarchus punctus and Dicentrarchus labrax), these species were collected from the Mediterranean Sea, Port Said, Egypt. Eleven SCoT primers were used in the study of generating different lengths of amplicons that ranged from 150bp to 1800bp (SCoT-2, SCoT-3, SCoT-4, SCoT-6, SCoT-7, SCoT-8, SCoT-9, SCoT-10, SCoT-28, SCoT-35 and SCoT-46). The polymorphism percent ranged from 18% with SCOT-28 primer to 75% with SCOT-6. The genetic similarity between the two species was 75.5%. Protein analysis using Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was also performed in this study producing a total of 22 bands that ranged in size from 19KD to 200KD. Each of the two species produced 22 bands.

There are many worries about the food safety of seafood contaminated with antibiotic residues. These residues can be potentially dangerous for public health owing to the causation of allergic reactions, toxic effects, and serious health problems. This study was planned to search the occurrence of chloramphenicol (CAP) and sulfonamide residue in sea bream and sea bass. A total of 82 fish samples were collected from 14 different sales points in Afyonkarahisar. The samples were analyzed for CAP and sulfonamide residues using the ELISA method. Results showed that up to 18.3% of the samples were contaminated with CAP. In the positive fish meat samples, the CAP residue concentrations ranged within 0.54–10.6 ng kg−1. The mean CAP residue concentration in positive samples was 4.25 ± 2.78 ng kg−1. No sulfonamide residue was detected from the samples. Despite the prohibition of CAP application in aquaculture, detectable CAP residues in fish meat samples indicate an illegal use of this antibiotic. Therefore, the results obtained in the study are negative signs for food safety. Official controls must be performed rigorously in accordance with the national residue monitoring plan especially for the illegal antibiotics.

Background Telemetry applied to aquatic organisms has recently developed greatly. Physiological sensors have been increasingly used as tools for fish welfare monitoring. However, for the technology to be used as a reliable welfare indicator, it is important that the tagging procedure does not disrupt fish physiology, behaviour and performance. In this communication, we share our medium-term data on stress physiological profile and growth performance after surgical tag implantation in two important marine fish species for European aquaculture, the sea bream (Sparus aurata) and the European sea bass (Dicentrarchus labrax). Results Blood samples after surgical tag implantation (46 days for the sea bream and 95 days for the sea bass) revealed no differences between tagged and untagged fish in cortisol, glucose and lactate levels, suggesting that the tag implantation does not induce prolonged stress in these species. Moreover, the specific growth rates were similar in the tagged and untagged fish of both species. Conclusion Surgical tag implantation does not have medium-term consequences for the stress physiology and growth performance of these two marine fish species in a controlled environment. These observations support the use of accelerometer tags as valuable tools for welfare monitoring in aquaculture conditions. This study also shows that tagged fish can be sampled during experiments and considered a representative portion of the population, as they display growth and physiological parameters comparable to those of untagged fish.

Methionine is a limiting amino acid (AA) in fish diets, particularly in those containing high levels of plant protein (PP), and is key in the immune system. Accordingly, outcome on the fish immune mechanisms of methionine-deficient and methionine-supplemented diets within the context of 0 % fishmeal formulation, after a short and prolonged feeding period, was studied in European seabass (Dicentrarchus labrax). For this, seabass juveniles were fed a (i) fishmeal-free diet, meeting AA requirements, but deficient in methionine (MET0·65); (ii) as control, the MET0·65 supplemented with l-methionine at 0·22 % of feed weight (CTRL); (iii) two diets, identical to MET0·65 but supplemented at 0·63 and 0·88 % of feed weight of l-methionine (MET1·25 and MET1·5, respectively); and (iv) a fishmeal-based diet (FM), as positive control. After 2 and 12 weeks of feeding, blood and plasma were sampled for leucocyte counting and humoral parameter assays and head-kidney collected for gene expression. After 2 weeks of feeding, a fishmeal-free diet supplemented with methionine led to changes in the expression of methionine- and leucocyte-related genes. A methionine immune-enhancer role was more evident after 12 weeks with an increased neutrophil percentage and a decreased expression of apoptotic genes, possibly indicating an enhancement of fish immunity by methionine dietary supplementation. Furthermore, even though CTRL and FM present similar methionine content, CTRL presented a reduced expression of several immune-related genes indicating that in a practical PP-based diet scenario, the requirement level of methionine for an optimal immune status could be higher.