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Introduction: Despite being a bacterial pathogen with devastating consequences, Tenacibaculum maritimum's pathogenesis is not fully understood. The aim of the present study was to elucidate if different inoculation routes (intraperitoneal - i.p - injection and bath challenge - known to induce mortality) can induce tenacibaculosis (i.e., using the same T. maritimum inoculum), as well as evaluate the short-term immune response of European sea bass (D. labrax). Additionally, the host response against i.p. injection of extracellular products (ECPs) was also studied. Methods: Fish were i.p. challenged with 5.5 x 105 CFU mL-1 of T. maritimum cells with or without ECPs (BECPs and BWO, respectively), ECPs alone or marine broth (mock). Another group of fish was bath-challenged with 5.5 x 105 CFU mL-1 to confirm the virulence of the bacterial inoculum. Undisturbed specimens were used as controls. The severity of both challenges was determined by following percentage survival. Blood, liver and head-kidney samples were collected at 0, 3, 6, 24 and 48 h post-challenge for assessing immune parameters, oxidative stress and gene expression. Total and differential peritoneal cell counts were performed. The presence of viable bacteria in the blood and peritoneal cavity was studied. Results: Symptoms of tenacibaculosis, such as skin/fin abrasions, were only observed in the bath-challenged fish, where 0% survival was recorded, whereas 100% survival was observed after i.p. injection of the same bacterial inoculum. An increase in total leukocyte numbers in the peritoneal cavity was observed 3 h post-injection of BECPs when compared to the other treatments. Blood total leukocytes, lymphocytes, and thrombocyte numbers dropped after the challenge, mainly in fish challenged with BECPs. At 48 h post-challenge, bactericidal activity in the plasma increased in fish injected with bacteria (with and without ECPs). The same tendency was seen for some of the oxidative stress parameters. [ABSTRACT FROM AUTHOR]

Extractive fisheries and marine aquaculture share space and target species. Several regional-scale examples exist of escapees entering wild fisheries landings, yet no study has assessed the influence of aquaculture on landings at an ecosystem scale. We examined the effects of farmed fish escapes on fisheries using FAO data and published escape rates for Gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax). Seabream landings were significantly correlated with the estimated biomass of escaped seabream entering the wild. There was a similar pattern for seabass until 2005, but the overall relationship between landings and escapes was not significant due to the dramatic drop in catches in recent years. We argue that seabass escapees' relatively high mortality, lower capturability, and minor 'leaking' from farms may obscure their influence on landings. Significant positive fisheries regime shifts were detected for both species, matching the onset of aquaculture in the Mediterranean and the period when escapees from aquaculture surpassed landings. Our results suggest that fish escapes of these two iconic species may mask wild stock overexploitation, confound stock assessments, alter genetic diversity, increase the risk of spreading pathogens and parasites, and compete with wild conspecifics while boosting fisheries landings. [ABSTRACT FROM AUTHOR]

Estimating tailbeat frequency (TBF) is a crucial component of fish swimming kinematics and performance, particularly because it provides information about energetics and behavioral responses to environmental cues. The most commonly used technique for TBF estimation is based on accelerometers. This paper proposes a novel approach using bioimpedance technology. This is the first time bioimpedance has been measured in a freely moving animal. This was made possible by implanting a flexible electrode in the back muscle of seabasses and having them in a swimming tunnel. The experiment first demonstrates that it is possible to measure bioimpedance in an immersed fish despite the high conductivity of seawater. An agreement analysis was then performed to compare a video-based reference measurement of TBF with the newly proposed approach. Several bioimpedance settings, such as the configuration and the extracted electrical parameters, were considered. Data analysis highlights that a 4-point setup for modulus impedance measurement at frequencies over 10 k Hz provides the best agreement (r > 0.98 and CCC > 0.97) with the video-based approach. These results attest to the significant benefits of integrating bioimpedance sensors in biologgers, especially considering the complementary parameters that can be extracted from bioimpedance measurements, such as length, weight, condition index, and fat content. [ABSTRACT FROM AUTHOR]

Fishmeal and fish oil have been the main sources of protein and fatty acid for aquaculture fish. However, their increasing price and low sustainability have led the aquafeed industry to seek sustainable alternative feedstuffs to meet the nutritional requirements of fish and improve their health and performance. Plant proteins have been successfully used to replace fishery derivatives in aquafeeds, but the presence of anti-nutritional substances is a potential drawback of this approach. Thus, it has been reported that phytate breakdown can be caused by feed supplementation with exogenous phytase. The inclusion of microalgae has been proposed to improve gut functionality in fish fed diets with a high vegetable protein content. The aim of this study was to evaluate the effect on the growth and gut microbiota of European seabass (Dicentrarchus labrax) juveniles of a diet containing a blend of microalgae (Arthrospira platensis and Nannochloropsis gaditana) and different concentrations of phytase. An 83-day feeding trial was conducted, comprising four experimental diets with 2.5% microalgae and 500, 1,000, 2,000, or 10,000 phytase units (FTU)/kg feed and a microalgae- and phytase-free control diet. At the end of the trial, a significantly increased body weight was observed in fish fed the diet with the highest phytase concentration (10,000 FTU/kg) versus controls, although the gut bacterial composition did not differ from controls in alpha or beta diversity with either majority (Weighted UniFrac) or minority bacterial strains (Unweighted UniFrac). In comparison to the control group, the groups fed diets with 1,000 or 2,000 FTU/kg diets had a lower alpha diversity (Shannon's diversity index), while those fed diets with 500 FTU/kg or 1,000 FTU/kg showed distinct clusters in beta diversity (involving minority ASVs). According to these findings, the diet containing the 2.5% microalgae blend with 10,000 FTU/kg may be useful to increase the aquafeed quality and sustain the growth performance of juvenile European seabass. [ABSTRACT FROM AUTHOR]

The length-weight relationship and growth performance of Sparus aurata and Dicentrarchus labrax were calculated at the El Mokretar Aqua fish farm in the Bay of Souahlia on the Algerian coast. During harvest, fish samples were collected from the El Mokretar Aqua fish farm in floating cages C8 and C3. Growth parameters were assessed at the start and end of breeding. The simple fisheries stock Aassessment methods (FSA) package estimated the length-weight relationship as LogWt= -1.18+2.08logLt for D.labrax and Log Wt= - 6.17+3.62logLt for S. aurata. These relationships indicate that the European seabass has a negative allometric growth, while the gilthead seabream has a positive allometric growth. During the rearing period, the zootechnical performance of the gilthead seabream and European seabass indicated favorable growth. Weight gain, specific growth rate, Fulton's condition factor, thermal-unit growth coefficient and feed conversion ratio showed a significant difference. These indicators are useful for planning and managing fish farms rearing these selected species. [ABSTRACT FROM AUTHOR]

This study aimed to identify parasitic species infesting marine fish collected from Lake Timsah across different seasons. A total of 480 marine fish of varying species, weights, and lengths (160 Dicentrarchus labrax, 160 Dicentrarchus punctatus, and 160 Sparus aurata) were randomly collected seasonally from September 2020 to August 2021. Most examined fish showed no pathognomonic clinical abnormalities and appeared normal. However, some D. labrax exhibited hemorrhages on the mouth, operculum, around the eyes, and at the bases of their fins, along with abdominal distension and emaciation. Infested D. punctatus showed excessive mucus and a mosaic appearance of the gills. Infested S. aurata displayed no external clinical abnormalities, except for some hemorrhagic lesions and slight abdominal distension. The total prevalence of parasitic infestation among the examined fish was 57.91%. The highest infestation rate was observed in D. punctatus (74.38%), followed by D. labrax (71.25%) and S. aurata (28.13%). The isolated parasites included nematodes (Hysterothylacium aduncum, Anisakis simplex larvae, and Contracaecum spp. larvae), digeneans (Erilepturus hamate and Tangiopsis chinensis), crustacean parasites (Lernanathropus kroyeri, Caligus minimus), and isopods (Livoneca redmanii). The total parasitic infestation rate varied significantly across different seasons (P<0.001), with the highest rate in winter (81.6%), followed by spring (70.8%), autumn (55%), and summer (24%). Several factors, such as season, fish species, and differences in body weight and length, affect the infestation rates. [ABSTRACT FROM AUTHOR]

(1) Background: This study aimed to evaluate the potential of short-chain fatty acids as functional ingredients to improve the immune status and disease resistance of European seabass (Dicentrarchus labrax) juveniles. (2) Methods: For that purpose, triplicate groups of fish with an initial body weight of 15.2 ± 0.03 g were fed isoproteic (43% crude protein) and isolipidic (18% crude lipids) diets supplemented with sodium acetate (SA), sodium propionate (SP), and sodium butyrate (SB) at two inclusion levels: 0.25% and 0.50%. An unsupplemented diet was used as a control. After 56 days of feeding with the experimental diets, fish were intraperitoneally (i.p.) injected with 100 µL of Vibrio anguillarum (1.2 × 107 Colony Forming Units (CFU)/mL) and mortality was recorded for 3 weeks. At the end of the trial, there were no differences in survival between the treatment groups and the control, but survival was higher in fish fed the diet supplemented with SB 0.50 than SP 0.25 (93.3 vs. 66.7%). Compared to the pre-challenge values, and regardless of diet composition, all hematological parameters (hemoglobin, hematocrit, red blood cells, white blood cells) measured decreased after 4 h of bacterial challenge, except for neutrophils which were increased. Independently of diet composition, lysozyme and nitric oxide decreased at 4 and 24 h post infection. Compared to the control, diets supplemented with SA and SP promoted an up-regulation of both pro- and anti-inflammatory cytokines at 4 h after the challenge, while the diets supplemented with SB promoted an up-regulation of pro- and anti-inflammatory cytokines at 24 h after the challenge. (3) Conclusions: Overall, present results suggest that SA and SP provide a fast response to a bacterial challenge in European sea bass juveniles, while SB provides increased survival. [ABSTRACT FROM AUTHOR]

In mariculture facilities, bacterial infections pose significant production challenges, with potentially catastrophic impacts on fish species. Bacterial co-infections are a widespread phenomenon in the natural marine environment, although their impact on aquatic organisms remains poorly investigated. This study aimed to detail the pathological findings associated with a natural bacterial co-infection caused by three different pathogens, namely Photobacterium damselae subsp. piscicida, Tenacibaculum maritimum and Vibrio sp., as the cause of mass mortality in European sea bass. The fish had been reared in open-net cages in Sicily and later transferred for experimental research purposes to a user establishment after immunization with an inactivated vaccine. Macroscopic, cytological and histopathological examinations were performed on 109 animals, and bacterial species were identified by the 16S rRNA gene. Overall, ulcerative skin lesions, necrotizing myositis and tail rot with occasional tail loss were associated with tenacibaculosis and vibriosis, while P. damselae subsp. piscicida mainly caused granulomatous inflammation in the spleen and head kidney. Finally, an injection site reaction due to the oil-adjuvanted vaccine administered intraperitoneally was observed in the abdominal fat. Understanding the impact of bacterial pathogens is essential to manage the health and welfare of farmed fish, and the importance of a good health monitoring program cannot be overstated to avoid outbreaks and the possible emergence of new pathogens due to the intensification of the production systems, antibiotic resistance and climate changes. The study would also highlight the importance of the quarantine period when animals supplied for research come from aquaculture farms and how the main goal in the near future should be to better define the procedures to provide completely pathogen-free animals. [ABSTRACT FROM AUTHOR]

Unraveling the evolutionary mechanisms and consequences of hybridization is a major concern in biology. Many studies have documented the interplay between recombination and selection in modulating the genomic landscape of introgression, but few have considered how associations with phenotype may affect this landscape. Here, we use the European seabass (Dicentrarchus labrax), a key species in marine aquaculture that undergoes natural hybridization, to determine how selection on phenotype modulates the introgression landscape between Atlantic and Mediterranean lineages. We use a high-density single nucleotide polymorphism array to assess individual local ancestry along the genome and improve the mapping of muscle fat content, a polygenic trait that is divergent between lineages. Taking into account variation in recombination rates, we reveal a purging of Atlantic ancestry in the admixed Mediterranean populations. While Atlantic individuals had higher muscle fat content, we observed that genomic regions associated with this trait in Mediterranean populations displayed reduced introgression of Atlantic ancestry. These results emphasize how selection against maladapted alleles shapes the genomic landscape of introgression. [ABSTRACT FROM AUTHOR]

Abstract Extractive fisheries and marine aquaculture share space and target species. Several regional-scale examples exist of escapees entering wild fisheries landings, yet no study has assessed the influence of aquaculture on landings at an ecosystem scale. We examined the effects of farmed fish escapes on fisheries using FAO data and published escape rates for Gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax). Seabream landings were significantly correlated with the estimated biomass of escaped seabream entering the wild. There was a similar pattern for seabass until 2005, but the overall relationship between landings and escapes was not significant due to the dramatic drop in catches in recent years. We argue that seabass escapees’ relatively high mortality, lower capturability, and minor ‘leaking’ from farms may obscure their influence on landings. Significant positive fisheries regime shifts were detected for both species, matching the onset of aquaculture in the Mediterranean and the period when escapees from aquaculture surpassed landings. Our results suggest that fish escapes of these two iconic species may mask wild stock overexploitation, confound stock assessments, alter genetic diversity, increase the risk of spreading pathogens and parasites, and compete with wild conspecifics while boosting fisheries landings.

Abstract This study investigated a disease outbreak characterized by caligid copepod infestations and subsequent secondary bacterial infections in European seabass (Dicentrarchus labrax) and flathead grey mullet (Mugil cephalus) cultivated at a private facility in the Deeba Triangle region of Egypt. Moribund fish displayed brown spots on the skin, tongue, and gills, along with lethargy and excess mucus. The fish suffered severe infections, exhibiting external hemorrhages, ulcers, and ascites. The fish had pale, enlarged livers with hemorrhaging. Comprehensive parasitological, bacteriological, molecular, immunity and histopathological analyses were conducted to identify the etiological agents and pathological changes. Caligid copepod infestation was observed in wet mounts from the buccal and branchial cavities of all examined fish, and the caligids were identified as Caligus clemensi through COI gene sequencing and phylogenetic analysis. Vibrio alginolyticus was confirmed as a secondary bacterial infection through biochemical tests, recA gene sequencing, and phylogenetic analyses. Antibiotic susceptibility testing revealed resistance to β-lactams, aminoglycosides, and trimethoprim-sulfamethoxazole in V. alginolyticus isolates. Upregulation of the inflammatory marker IL-1β in gill and skin tissues indicated a robust cell-mediated immune response against the pathogens. Histopathological examination revealed severe tissue damage, hyperplasia, hemorrhage, and congestion in the gills, along with hepatocellular degeneration and steatosis in the liver, providing initial insights into this outbreak. A comprehensive therapeutic regimen was implemented, comprising prolonged hydrogen peroxide immersion baths, followed by the application of the nature-identical plant-based compound Lice-less and probiotic Sanolife Pro-W supplementation. This integrated approach effectively eliminated C. clemensi infestations, controlled secondary bacterial infections, and restored fish health, reducing morbidity and mortality rates to minimal levels.

The study involved three groups of six broodstock with a 1:1 male-to-female ratio. They were injected with 13 µg/kg LHRHa to stimulate spawning. We fed the broodstock three diets: a control diet without selenium, a diet containing 0.3 mg of nano-selenium /kg (N-Se), and a diet containing 4 mg of organic selenium /kg (O-Se). The broodstock diet consisted of equal parts of dry feed (45% protein), sardines, and squid. After being laid, the eggs were obtained from the collection ponds at the General Authority for Fisheries Development's fish hatchery and incubated until hatching. The larvae were given a micro diet containing 51.7% crude protein and live food (Rotifer and Artemia). Rotifer density increased from 5/ml to 15/ml by day 22 dph, Artemia nauplii increased from 0.2 to 4 ind./ml, from 7 to 35 dph then decreased to 0 at 55 dph, and micro-diets increased from 100-200 µ at 16 dph to 200-400 µ at 23-40 dph to 300-500 µ at 55 dph, and 500-1000 µ until the experiment ended. Three different diets in three replicates were tested: A micro diet free of selenium as a control diet (C), A micro diet with 0.3 mg of nano selenium (N-Se) kg-1, and A micro diet supplemented with organic selenium 4 mg (O-Se). Each group was taken from the three Broodstock groups respectively. Sixteen days after hatching, the three experimental micro diets were introduced to the larvae and continued for 76 days post-hatch. Larvae (260,000 per tank) were placed in fiberglass tanks with 4 m3 of water at a temperature of 19±2°C for optimal conditions. The larvae fed the N-Se diet had significantly better survival rates (75.0 ± 1.2 %), final body weight (240.0 ± 5.8 mg), weight gain (239.00 ± 5.8 mg), average daily gain (3.98±0.1mg), total length (39.0±0.06 mm), specific growth rate (9.133±0.04 %/day), feed intake (471.67±0.01 mg), and better feed conversion ratio (1.97±0.01) than the other groups (P < 0.05). The group provided with N-Se also had the highest levels of glutathione peroxidase enzyme (GPx) content in the whole larval body, whereas the control diet without Se supplementation recorded the lowest value of (14.8 ± 0.1 U/mg protein). The number and length of folds in the stomach and esophagus of sea bass post-larvae fed on diets fortified with selenium in both forms, nanoparticles or organic, showed a significant (P < 0.05) enhancement on the larval gastrointestinal (GI) tract. Moreover, selenium has an anti-inflammatory action in sea bass post-larvae. This study concluded that using N-Se as an antioxidant supports the growth and survival of European seabass D. labrax, gastrointestinal development and antioxidant efficacy during critical weaning. [ABSTRACT FROM AUTHOR]

The use of intensive systems in aquaculture causes an increase in environmental stress agents, reducing water quality and facilitating the appearance of pathologies in individuals. In this context, the selection of ingredients is a key strategy in managing the quality of aquafeed and the cultivation of aquaculture species. Considering this, wine by-products can be a potential functional ingredient due to several particular characteristics, such as their low cost, large volumes produced, and for being a natural source of bioactive compounds with antioxidant activity. The present study developed different experiments focused on evaluating the benefits of feeding juvenile European sea bass during 5 weeks with feeds incorporating 0.4% red wine grape pomace (GP). At the end of the feeding period, potential modifications in metabolism, immunological and oxidative status, and functionality of intestinal microbiota were assessed as well as the potential protective effect against oxidation in fish fillets during 6 days of cold storage (4 °C). In addition, the preservative effect of GP on the feed when stored for a period of 12 weeks at two different temperatures (4 °C and 25 °C) was evaluated. The results demonstrated that the inclusion of GP in feeds for European sea bass prevents oxidation when stored at room temperature. In addition, a general improvement in the physiological and immunological status, as well as fillet quality, was evidenced. [ABSTRACT FROM AUTHOR]

This study is the investigation of Mediterranean aquaculture complete history, from 1950 to 2020. Both functional than geographical expansion of aquaculture is investigated, considering two main complementary aspects of aquaculture: farmed species and farming countries. According to the models proposed in this research, Nile tilapia and Egypt will dominate the future of Mediterranean aquaculture. Malta and Israel are the first producer countries, in relative terms. The most pervasive species are European sea bass and gilthead sea bream that are promising for a future expansion. In several countries, aquaculture has huge potentiality of development and it could grow with a factor of 5 or more, based on the ratio capture vs fishery on country size. Aquaculture total production in 2020 was of 2.8 Mln tons and it is expected to reach from 3.65 Mln tons in 2030. Aquaculture will grow in the countries and species that in this moment are dominant and the future of Mediterranean aquaculture will be characterized by the affirmation of these ones. [ABSTRACT FROM AUTHOR]

Marine pollution caused by heavy metals has emerged as a significant environmental concern, garnering increased attention in recent years. The accumulation of heavy metals in the tissues of marine organisms poses substantial threats to both marine ecosystems and human populations that rely on seafood as a primary food source. Fish and crustaceans are effective biomonitors for assessing heavy metal contamination in aquatic environments. In this study, we determined the concentrations of several heavy metals, including cadmium (Cd), lead (Pb), nickel (Ni), mercury (Hg), and tin (Sn), in four fish species (Mugil cephalus, Mugil capito, L. aurata, and Morone labrax) and five crustacean species (S. rivulatus, Cerastoderma glaucum, Paratapes undulatus, R. decussatus, Callinectes sapidus, and Metapenaeus Stebbingi) from Temsah Lake during both winter and summer seasons. To evaluate the potential ecological and health risks associated with consuming these fish and crustacean species, we calculated the metal pollution index (MPI), weekly intake (EWI), target hazard quotient (THQ), and carcinogenic risk (CR) values. The results revealed a noticeable increase in metal levels during the summer compared to winter in the studied samples. Moreover, the concentration of heavy metals in the muscles of the species generally exceeded those in the liver and gills. The MPI values indicated that Morone labrax exhibited the highest values during winter, while L. aurata showed the highest values during summer. Mugil cephalus demonstrated the lowest MPI values in both seasons. The EWI values for the studied metals were found to be lower than the corresponding tolerable weekly intake (TWI) values. Additionally, under average exposure conditions, the THQ and HI data were generally below one for most study species in the area. The calculated CR values for investigated metals in the studied species indicated acceptable carcinogenic risk levels. Therefore, this suggests that consuming studied species within Temsah lake does not present any potential health hazards for consumers. [ABSTRACT FROM AUTHOR]

Phthalates or phthalate esters (PAEs) have become a serious concern due to their toxicity and risks of migration from contact materials to food matrices and the environment. The aim of this study is to monitor the possible migration potential of PAEs in pelagic fish stored in vacuum packaging depending on the storage time and to determine the polyethylene polymers. In order to achieve this goal, sea bass (Dicentrarchus labrax) and anchovy fish (Engraulis encrasicolus) were randomly packaged in vacuum bags and then stored for 90 days. Phthalate content was determined by GC/MS technique in the muscle tissue of each fish species at certain periods (0, 30, and 90 days) of storage, and on the first day in the packaging material and fish meat. As a result of the analysis performed in µ-Raman spectroscopy, no microplastics were detected in both fish species' meats. FTIR spectroscopy results of the packaging material determined nylon in the chemical content of the packaging material before processing. It has been determined that the chemical composition of the packaging used in the vacuum packaging process is affected by the temperature, depending on the storage period, and different polymer types are formed in the processed package material. It was determined that the dominant PAE homologues were Di-n-pentyl phthalate (DPENP) in both fish meat and Di-(2-ethylhexyl)-phthalate (DEHP) in the package. However, during storage, Dibutylphthalate (DBP) became dominant in anchovies and DPENP became dominant in sea bass, differing according to fish species and storage time. [ABSTRACT FROM AUTHOR]

In many countries, increasing concern for animal welfare is driving retailer commitments and government legislation that aim to improve the lives of farmed fish. One aspect of fish welfare involves stunning fish prior to slaughter. The feasibility of stunning depends on the species of fish and physical farm characteristics. In this article, we provide an overview of stunning before slaughter in European sea bass and sea bream aquaculture, one of the largest finfish farming industries in the developed world that does not yet stun most of its production. Sea bass and sea bream stunning necessitates the use of electrical stunning equipment aboard harvest vessels, often a significant distance from the shoreline; this presents an interesting engineering and policy challenge. Together, Türkiye, Greece, Spain, and Italy produced over 400,000 t of sea bass and sea bream in 2020. In Türkiye and Greece, farms are numerous and located very close to the shoreline. In Spain and Italy, farms are few and located far from the shoreline. The highest average production is found in farms from Türkiye (1,000 t) and Spain (1,300 t, and lower average production is found in Greece (300 t) and Italy (350 t). Producer progress towards the installation of electrical stunning appears comparatively well-developed for Türkiye, Spain, and Greece, though we emphasise that producers and other stakeholders require continued support to realise this opportunity. Producers in Italy appear slower to make progress on this aspect of animal welfare and may require additional support. [ABSTRACT FROM AUTHOR]

Understanding of risk factors for parasite introduction and amplification within fish farms is crucial to design effective biosecurity and control management strategies but currently, quantitative data on the relevance of such risk factors is largely absent. We have designed the questionnaires for stakeholders to characterize the risk factors and estimate their relevance for infections causing major economic burden on gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax) production: the myxozoan Enteromyxum leei, the monogenean Sparicotyle chrysophrii, the crustacean Ceratothoa oestroides and the dinoflagellate Amyloodinium ocellatum. Twenty-two experts (Belgium, Croatia, Greece, Italy, Norway, and Spain) were invited to participate in an online questionnaire, followed by a physical meeting to discuss the most probable values for parameter estimates. Quantitative estimates were obtained for the relevance of risk routes of parasite spread (e.g., the likelihood of parasite transmission from an infected to an uninfected net cage 5 m away was estimated to be 90% for E. leei), and the relevance of management procedures and environmental factors that may have an impact on the probability of infection to lead to disease (e.g., where mortalities are removed at > 5-day intervals, the likelihood that infection will lead to disease was 30% for S. chrysophrii). These quantitative estimates were appraised, including the delay in reaching harvest size, or cumulative mortality during phases of production, being essential for calculation of the burden of these diseases in aquaculture. The data presented are highly valuable to the development of economically viable biosecurity and specific integrated pest management strategies. [ABSTRACT FROM AUTHOR]

To investigate the presence of Pseudomonas anguilliseptica, one hundred specimens of sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) were collected alongside water samples during episodes of widespread fish mortality in marine fish farms located in the northern region of Egypt. This study documented the clinical and postmortem manifestations observed in moribund sea bream and sea bass, thus providing evidence for the occurrence of a septicemic-hemorrhagic bacterial disease. Fourteen strains of P. anguilliseptica were isolated and characterized from both sea bream and sea bass specimens. The conventional bacteriology methods were employed to retrieve the causative bacterial agent and subsequently evaluate its phenotypic traits. Moreover, sequencing of the 16 S rRNA was conducted to characterize the identified microorganism. Furthermore, multilocus sequence analysis (MLSA) was employed to confirm the identity of P. anguilliseptica and elucidate the phylogenetic interrelationship among various strains. Regardless of their source or the fish species from which the strains were obtained, these isolates showed a high level of phenotypic homogeneity. MLSA displayed a genetic homogeneity among isolates despite their different geographic origins. Antibiogram revealed the sensitivity of some P. anguilliseptica strains for antibiotics (florfenicol, trimethoprim, sulfamethoxazole, cefotaxime, and ciprofloxacin). Isolated strains were harboring some antibiotic-resistant genes, with the most prevalent being tetA gene, followed by ermB gene. Water physico-chemical parameters (low temperature and salinity fluctuation) were convenient for bacterial growth. In addition, P. anguilliseptica strains could resist several antibiotics and harbored antibiotic-resistant genes, resulting in difficulties in fish treatment. [ABSTRACT FROM AUTHOR]

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

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

This study addressed the urgent need for sustainable protein sources in aquaculture due to the depletion of marine resources and rising costs. Animal protein sources, particularly poultry by-product meal (PBM) and insect exuviae meal, were investigated as viable alternatives to fishmeal (FM). The research study confirmed the successful replacement of FM with a combination of PBM and insect exuviae meal (up to 50%) in the diet of European seabass without compromising growth, feed conversion, gut health, and liver fat content. In particular, growth was robust with both PBM formulations, with the 25% PBM diet showing better results. Histological examinations showed good gut and liver health, contradicting the concerns of previous studies. This paper emphasizes the importance of holistic analyzes that go beyond growth parameters and include histomorphological investigations. The results show that PBM in combination with insect/exuviae meal is well tolerated by seabass, which is consistent with reports in the literature of it mitigating negative effects on gut health. A detailed analysis of the microbiota revealed a decrease in the Firmicutes/Proteobacteria ratio due to an increase in potentially pathogenic bacteria. However, the formulation containing insect exuviae partially counteracted this effect by preserving the beneficial Lactobacillus and promoting the synthesis of short-chain fatty acids (SCFAs), particularly butyrate. Chitin-rich components from insect exuviae were associated with improved gut health, which was supported by the increased production of SCFAs, which are known for their anti-inflammatory properties. This paper concludes that a combination of PBM and insect/exuviae meal can replace up to 50% of FM in the diet of seabass, supporting sustainable aquaculture practices. Despite some changes in the microbiota, the negative effects are mitigated by the addition of insect exuviae, highlighting their potential as a prebiotic to increase fish productivity and contribute to a circular economy in aquaculture. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of starvation and refeeding on the growth and food intake of gilthead seabream (Sparus aurata) and seabass (Dicentrarchus labrax) and on the growth and nitrogen uptake of glasswort (Salicornia europaea) in a polyculture aquaponic system under 12 ppt salinity for 75 days. Nine small-scale autonomous aquaponic systems were used, each containing 10 gilthead seabreams (average weight of 6.33 ± 0.73 g and average length of 5.73 ± 0.72 cm) and 10 seabasses (5.82 ± 0.77 g and 6.35 ± 0.45 cm), as well as five glasswort plants. Three fish feeding treatments were performed, a control (A), in which fish were fed daily until satiation, and two fasting treatments for 4 (B) and 7 days (C). Fish growth performance was significantly lower (p < 0.05) in the C treatment for both species compared to treatments A and B. Food consumption (FC) and feed conversion ratio (FCR) were significantly higher (p < 0.05) in treatment C. Glasswort growth performance was significantly higher in treatment C (p < 0.05). The results showed that the 4-day food-deprived fish were similar to the control fish by achieving partial compensatory growth. The more extended fasting period (7 days) resulted in significantly lower growth performance. The lipid and nitrogen retention levels in both species were significantly lower in food-deprived fish than in the control fish both before and during compensatory growth. The results suggest that a feeding schedule involving starvation–refeeding cycles is a promising feed management option for these species in polyculture aquaponic systems. The effect of food deprivation was also significantly beneficial (p < 0.05) for the growth performance of glasswort compared to the control treatment. [ABSTRACT FROM AUTHOR]

E3 ubiquitin ligases, key components of the ubiquitin proteasome system, orchestrate protein degradation through ubiquitylation and profoundly impact cellular biology. Small HERC E3 ligases (HERC3-6) have diverse functions in mammals, including roles in spermatogenesis, protein degradation, and immunity. Until now, only mammals' HERC3, HERC5, and HERC6 are known to participate in immune responses, with major involvement in the antiviral response. Interestingly, an exclusive HERC7 has been characterized in fish showing great molecular conservation and antiviral roles. Thus, this study identifies and characterizes the herc7 gene in the European sea bass teleost. The European sea bass herc7 gene and the putative protein show good conservation of the promoter binding sites for interferons and the RCC1 and HECT domains characteristic of HERC proteins, respectively. The phylogenetic analysis shows a unique cluster with the fish-exclusive HERC7 orthologues. During ontogeny, the herc7 gene is expressed from 3 days post-fertilization onwards, being constitutively and widely distributed in adult tissues. In vitro, stimulated leucocytes up-regulate the herc7 gene in response to mitogens and viruses, pointing to a role in the immune response. Furthermore, sea bass herc7 expression is related to the interferon response intensity and viral load in different tissues upon in vivo infection with red-grouper betanodavirus (RGNNV), suggesting the potential involvement of fish HERC7 in ISGylation-based antiviral activity, similarly to mammalian HERC5. This study broadens the understanding of small HERC proteins in fish species and highlights HERC7 as a potential contributor to the immune response in European sea bass, with implications for antiviral defense mechanisms. Future research is needed to unravel the precise actions and functions of HERC7 in teleost fish immunity, providing insights into direct antiviral activity and viral evasion. [ABSTRACT FROM AUTHOR]

The interplay between environmental, biological, and physical factors often leads to the deterioration of dead fish in marine cages prior to their removal. Depending on the weight of the dead fish and the frequency of their removal, deterioration can progress to a stage where visual identification by divers becomes challenging, thereby disrupting accurate counting of dead fish. This study presents a practical precision tool for monitoring the number of dead fish during the pregrowth and growth phases of caged European sea bass (Dicentrarchus labrax). To improve the assessment of collected mortality, experiments were conducted in farming cages with various fish weights. Identifiable fish rates (I, %) were calculated every 24 hr and classified into four weight classes: WC1 (4–15 g), WC2 (15–30 g), WC3 (30–80 g), and WC4 (>80 g). The corrected number of dead fish (M) was calculated by dividing the collected number (C) by a correction factor (McR), which was determined based on the adopted removal frequency. The possible mortality removal frequencies per week (Fn) included operations such as F7 (daily), F3 (3 times), F2 (2 times), and F1 (once). The smallest correction denominator was 22% for WC1 at a frequency of once per week, whereas the maximum was 100% for WC3 and WC4 daily. The results revealed a high negative significant correlation between Fn and uncollected degraded fish rate (UR) (r = –0.841, p < 0.05). Applying corrections to mortality collected in three finished batches (B2, B3, and B7) led to an increase in the mortality rate by 3.9% ± 1.5%, 5.5% ± 0.7%, and 5.0% ± 0.5%, respectively. This explained 16.8% ± 4.7%, 65.5% ± 26.7%, and 30.3% ± 3.7% of fish disappearances in B2, B3, and B7, respectively. The significance of this study lies in its practical applicability to fish farms as a precise tool for monitoring fish raised in marine cages. [ABSTRACT FROM AUTHOR]

Aquaculture has become the largest source of seafood consumption, leading to increased research in aqua-nutrition. A survey of publications on aqua-nutrition topics was conducted, revealing that feed additives are the most studied area due to the need for alternatives to antibiotics. Plant extracts and microbial agents are popular feed additives, with a focus on natural and green options. Research on alternative protein and lipid sources, such as insects and microalgae, is also prominent. The study emphasizes the importance of considering the demands of the aquaculture industry and market in aqua-nutrition research. [Extracted from the article]

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

The European Commission requested scientific and technical assistance in the preparation of a EU‐wide baseline survey of antimicrobial resistance (AMR) in bacteria from aquaculture animals. It is recommended that the survey would aim at estimating the occurrence of AMR in Aeromonas spp. isolated from Atlantic Salmon (Salmo salar), European seabass (Dicentrarchus labrax) and trout (Salmo trutta, Salvelinus fontinalis, Oncorhynchus mykiss) intended to consumption, at harvesting (at farm/slaughter), at the EU level and in addition, at estimating the occurrence and diversity of AMR of Escherichia coli, Enterococcus faecium, Enterococcus faecalis, Vibrio parahaemolyticus and Vibrio alginolyticus in blue mussel (Mytilus edulis) and Mediterranean mussel (Mytilus galloprovincialis) from production areas and at dispatch centres at the EU level. These technical specifications define the target populations, the sample size for the survey, sample collection requirements, the analytical methods (for isolation, identification, phenotypic susceptibility testing and further genotypic analysis of some of the bacteria targeted) and the data reporting requirements. The data to be reported by the EU Member States to support this baseline survey are presented in three data models. The results of the survey should be reported using the EFSA reporting system. This publication is linked to the following EFSA Journal article: http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2024.8896/full [ABSTRACT FROM AUTHOR]

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

Aquafeed's contamination by microplastics can pose a risk to fish health and quality since they can be absorbed by the gastrointestinal tract and translocate to different tissues. The liver acts as a retaining organ with the consequent triggering of oxidative stress response. The present study aimed to combine the use of natural astaxanthin with natural-based microcapsules to counteract these negative side effects. European seabass juveniles were fed diets containing commercially available fluorescent microplastic microbeads (1–5 μm; 50 mg/kg feed) alone or combined with microencapsulated astaxanthin (AX) (7 g/kg feed; tested for half or whole feeding trial—30 or 60 days, respectively). Fish from the different dietary treatments did not evidence variations in survival and growth performance and did not show pathological alterations at the intestinal level. However, the microplastics were absorbed at the intestinal level with a consequent translocation to the liver, leading, when provided solely, to sod1, sod2, and cat upregulation. Interestingly, the dietary implementation of microencapsulated AX led to a mitigation of oxidative stress. In addition, the microcapsules, due to their composition, promoted microplastic coagulation in the fish gut, limiting their absorption and accumulation in all the tissues analyzed. These results were supported by in vitro tests, which demonstrated that the microcapsules promoted microplastic coagula formation too large to be absorbed at the intestinal level and by the fact that the coagulated microplastics were released through the fish feces. [ABSTRACT FROM AUTHOR]

The purpose of this study is to analyze a possible substitution relationship between farmed gilthead seabream (Sparus aurata) and farmed European seabass (Dicentrarchus labrax) in Mediterranean markets. Seabream and seabass are the two most important aquaculture species in the Mediterranean area. Greece and Turkey are the main producing and exporting countries, while the main consumer markets are in Spain and Italy. Despite the fact that both species are produced by the same companies and use the same international logistics chains, there are no previous analysis regarding a potential competitive relationship between the two species. This work performs a cointegration analysis and tests for market integration between the two species in the frame of the competition across Greece and Turkey in the international market, considering Spanish and Italian seabream imports prices in the period 2009–2021. Results indicates that the substitution between seabass and seabream only takes place in a context of competition between producing and exporting countries, in which species from one country can indistinctly substitute any species from the competing country. On the contrary, when the supply of a given country is differentiated from the rest of the market, the two species will have a differentiated behavior. [ABSTRACT FROM AUTHOR]

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

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

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

A long-term feeding trial (90 days) was conducted to investigate the effects of dietary supplementation with lavender oil (LO) on the growth performance, innate immunity, antioxidant status, and histomorphometry of different organs of juvenile European seabass (Dicentrarchus labrax). Four groups in triplicate were fed increasing levels of LO (0, 1, 2, and 3 kg−1 diet, expressed as F0, F1, F2, and F3, respectively). Fish weighing 76.87 ± 0.14 g/fish were stocked in 1000-L tanks at an initial stocking density of 25 fish. The results revealed that growth performance and feed utilization indices were significantly improved in the LO-treated groups compared to the control, with the highest values in favor of the F2 group. According to the polynomial second-order regression, the optimal dietary level of LO averaged 2.15–2.24 g/kg diet. Whole body protein and digestive enzyme activities were increased with increasing LO supplementation levels up to 2 mL kg−1. Fish-fed F2 diet exhibited a significant decrease in serum liver function enzymes. A considerable increase in total protein, albumin, and total immunoglobulin was reported in LO-supplemented groups over the control. Dietary LO significantly modulated antioxidant status by increasing antioxidant enzyme activities and decreasing malondialdehyde levels. Microscopic investigation of the gills, liver, and mid-intestine revealed that LO-treated fish had healthier histological features, with normal gill lamella and hepatocytes, and a positive effect of LO on intestinal villi length and goblet cell count. The LO could be used as a dietary supplement in the diet of seabass at the recommended level of 2 g kg−1 to improve growth, feed conversion, physiological status, and organ histomorphometry. [ABSTRACT FROM AUTHOR]

The implementation of a system to assess the risk of Amyloodinium ocellatum occurrence in rearing ponds in fish farms located in southern Spain is a fundamental aspect to ensure the economic viability of these facilities. For this purpose, a computer program (called Amy) for Windows PCs and an application for mobile devices (AmyAPP), based on the Android operating system, were developed integrating transformation functions and weightings associated with environmental parameters and fish behavioural factors from which it is possible to estimate the level of risk of occurrence of A. ocellatum. The weights for each of the environmental parameters and behavioural factors were estimated from the responses of a panel of experts (the fish farmers) using a Delphi methodology. The results indicate that, under operational validation, Amy/AmyAPP responses were statistically sensitive to the occurrence of A. ocellatum outbreaks in sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) rearing ponds. [ABSTRACT FROM AUTHOR]

Otolith shape is often used as a tool in fish stock identification. The goal of this study was to experimentally assess the influence of changing temperature and ontogenic evolution on the shape component of the European seabass (Dicentrarchus labrax) otolith during early‐life stages. A total of 1079 individuals were reared in a water temperature of 16°C up to 232 days post hatch (dph). During this experiment, several specimens were transferred into tanks with a water temperature of 21°C to obtain at the end of this study four different temperature treatments, each with varying ratios between the number of days at 16 and 21°C. To evaluate the otolith morphogenesis, samples were examined at 43, 72, 86 and 100 dph. The evolution of normalized otolith shape from hatching up to 100 dph showed that there were two main successive changes. First, faster growth in the antero‐posterior axis than in the dorso‐ventral axis changed the circular‐shaped otolith from that observed at hatching and, second, increasing the complexity relating to the area between the rostrum and the anti‐rostrum. To test the effect of changing temperature, growing degree‐day was used in three linear mixed‐effect models. Otolith morphogenesis was positively correlated to growing degree‐day, but was also dependent on temperature level. Otolith shape is influenced by environmental factors, particularly temperature, making it an efficient tool for fish stock identification. [ABSTRACT FROM AUTHOR]

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

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

The replacement of fish oil with plant oils is a common practice in aquaculture to compensate for the shortage of fish oil supply and has been thoroughly studied. However, because the experimental conditions vary in many aspects, the results are usually inconsistent quantitatively. Therefore, a meta‐analysis was conducted based on a dataset containing 328 articles to systematically model the influence of plant oils on the main aquaculture fish. In addition to demonstrating the species‐specific dose‐dependent impact of plant oils on fish growth, feed utilization efficiency, lipid deposition and health parameters, we have also investigated the role of other factors in this process. We found that the adverse effects caused by plant oils worsen as the experimental duration extends for Atlantic salmon, while Gilthead seabream and European seabass gradually adapt to the change. Further, water temperature could be a decisive factor for Rainbow trout, and early adaptation to plant oils would be helpful for Gilthead seabream. Moreover, sufficient fishmeal supply could alleviate the adverse effects caused by plant oils for most species, but for Gilthead seabream and European seabass, the growth suppression effect of plant oil was larger when fed high‐fishmeal diets. Besides, by comprehensively considering the effects of plant oils, we matched the potential optimal plant oil for each fish species. Our article quantitatively modelled the adverse effects of replacing fish oil with plant oils, investigated the influences of assistant factors and offered a panorama of the research status with emphasis on potential breakthrough orientations. [ABSTRACT FROM AUTHOR]

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

Marine aquaculture, particularly in the Mediterranean region, faces the challenge of minimizing growth dispersion, which has a direct impact on the production cycle, market value and sustainability of the sector. Conventional grading methods are resource intensive and potentially detrimental to fish health. The current study presented an innovative approach in predicting fish weight dispersion in European seabass (Dicentrarchus labrax) aquaculture. Seabass is one of the two major fish species cultivated on the Mediterranean coast, with a fattening cycle of 18–24 months. During this period, several grading operations are carried out to minimize growth dispersion. The intricate feed-fish-water system, characterized by complex interactions among feeding regimes, fish behavior, individual metabolism and environmental factors, is the focus of the study. The comprehensive, five-step methodology addresses this complexity. The process begins with a Discrete Event System (DES) model that simulates the feed-fish-water dynamics, taking into account individual fish metabolism. This is followed by the development of a surrogate machine learning (ML) regressor model, which is trained on DES simulation data to efficiently predict growth distribution. The model is then calibrated and customized for specific fish stocks and production tanks. The preliminary results from 21 tanks in two trials with European seabass (D. labrax) showed the effectiveness of the method. The results from the simulation models achieved a R2 of 99.9 % and a Mean Absolute Percentage Error (MAPE) of 1.1 % for the prediction of mean final weight and a R2 of 90.3 % with a MAPE of 8.1 % for the standard deviation of final weight. In summary, this study represents a significant advance in the planning and management of seabass aquaculture. Given the lack of effective prediction tools in the aquaculture industry, the proposed methodology has the potential to reduce risks and inefficiencies, thus possibly optimizing aquaculture practices by increasing sustainability and profitability.

Simple Summary: After a decade of research about the use of insects as fish feed, this paper reports the results of a large-scale trial on European sea bass (Dicentrarchus labrax) farmed under commercial conditions. Fish were fed an experimental diet containing 10% Hermetia illucens larva meal, 30% poultry by-product meal, and <5.5 g/100 g of feed of marine proteins. The results highlight that fish growth performances and the flesh quality of sea bass fed the experimental diet were similar to those of fish fed a commercial diet containing fish meal and fish oil. This study suggests that a diet rich in plant proteins, in which H. illucens and poultry by-products are also included, may be a viable alternative to existing aquafeeds for marine species. Protein meals from insects in combination with poultry by-product meal appear to be promising ingredients for replacing conventional proteins in the diets of carnivorous fish. The present study explored the effects on growth performance, hepatic enzymatic activity, and fillet physical and nutritional characteristics during a 66-day feeding trial performed on European seabass. A total of 3000 fish were distributed into three tanks, where the control group was fed with a commercial diet (CG) and a second group was fed in duplicate with the experimental diet (SSH) containing 10% Hermetia illucens larva meal, 30% poultry by-product meal, and <5.5 g/100 g of feed of marine origin proteins. All fish showed good growth performance. Glucose-6-phosphate dehydrogenase, aspartate aminotransferase, and 3-hydroxyacyl-CoA dehydrogenase activities were higher in the SSH group than in the CG group. The fillet fatty acid profile was largely unaffected by diet, except for a few fatty acids. Fish fed the SSH diet had a lower C22:1n-11 content than CG, thus suggesting an increased β-oxidation. The oxidative status of muscle lipids was not affected by the diet. In conclusion, the present study showed that European seabass can be successfully fed the SSH diet for two months in a commercial setting. [ABSTRACT FROM AUTHOR]

Numerous studies have reported the disadvantages of using plant protein in aquafeeds owing to the presence of antinutritional factors. Particularly, phytate can be overcome by dietary supplementation with exogenous phytase. On the other hand, the use of microalgae has been proven to be a valuable strategy for enhancing the digestive functionality in fish fed diets with high plant protein content. It was hypothesized that the simultaneous inclusion of phytase with microalgae can be useful to improve growth performance and digestive functionality in fish fed diets with high content of plant protein. In this study, the effects of feeds supplemented with different levels of exogenous phytase (FTU) and 2.5% of a blend of Arthrospira platensis and Nannochloropsis gaditana were evaluated on growth performance, metabolism, and gut functionality in European seabass (Dicentrarchus labrax) juveniles. Fish were fed ad libitum for 83 days with five diets containing different enzyme ratios (FTU), in triplicate: (i) control (0 FTU); (ii) 500 FTU; (iii) 1,000 FTU; (iv) 2,000 FTU; and (v) 10,000 FTU. At the end of the feeding period, zootechnical indexes were estimated, and biological samples were withdrawn for physiological determinations. The results obtained showed an overall improvement in the productive efficiency, general metabolism, and intestinal functionality in fish fed the highest phytase inclusion (2,000 and 10,000 FTU). Final weight (75.51 ± 1.01 g vs. 66.76 ± 1.26 g, p = 0.005), SGR (1.15 ± 0.02 vs. 1.00 ± 0.02, p = 0.006). and feed efficiency (0.80 ± 0.02% day−1 vs. 0.67 ± 0.01% day−1, p = 0.012) were higher in fish fed 10,000 FTU. The chemical composition of muscle and plasma metabolites did not vary among dietary treatments, except for the high glucose and low glycogen content in the liver with 2,000 FTU group. Focusing on gut functionality, enzyme activities tended to be higher in fish fed diets supplemented with phytase and microalgae, and significant differences were found for trypsin, chymotrypsin, and alkaline phosphatase with 1,000, 2,000, and 10,000 FTU, and leucine aminopeptidase with 2,000 and 10,000 FTU (p < 0.0001). Analysis of intestinal morphology revealed that 2,000 and 10,000 FTU combined with microalgae increased villi height and decreased villi diameter and enterocyte height. The presence of microalgae at low phytase supplementation level seems to lack of influence on the different parameters evaluated whereas only increased dietary phytase levels impacted on growth, nutrient utilization, and intestinal functionality. In addition, faecal samples were obtained by stripping the final portion of the intestines, from which the phosphorus and nitrogen were quantified. Apparent digestibility coefficient of phosphorus with 2,000 FTU and 10,000 FTU were higher, 74.3% and 77.8%, respectively, compared to control (52.4%). The results revealed a decrease in the amount of P shed with the excreta from the animals supplemented with phytase, a fact that evidenced an increased intestinal absorption of this element. Overall, the results obtained pointed out that phytase can be used at 10,000, and even 2,000, FTU in combination with microalgae as an approach to reducing feed costs and boost fish growth and digestive functionality of fish, while minimizing the environmental impacts of juvenile European seabass farms. [ABSTRACT FROM AUTHOR]

Various commercial fish species utilize different coastal habitats as nurseries in their juvenile stages, with surf zones being particularly crucial due to the protection and abundant food resources they offer. Among the species that rely on these areas are the spotted seabass (Dicentrarchus punctatus) and the European seabass (Dicentrarchus labrax). This study aimed to investigate the age and feeding habits of surf zone specimens of these species and explore their environmental adaptations. The average size for D. punctatus was 16.94 ± 4.05 cm, and for D. labrax, it was 23.23 ± 6.30 cm. The length–weight relationship for D. punctatus was TW = 0.013*TL2.885 (parameter a: 95% CI: 0.012–0.014; parameter b: 95% CI: 2.854–2.917), and for D. labrax, it was TW = 0.008*TL3.095 (parameter a: 95% CI: 0.006–0.009; parameter b: 95% CI: 3.040–3.151). In both D. punctatus (79.20%) and D. labrax (75.92%), the predominant age classes were 1+ and 2+. Significant variations in age class abundance were observed in D. punctatus based on the time of day, lunar phase, and season, while D. labrax showed variations only by season. A diet analysis revealed that both species primarily consume mysids and fish, with D. punctatus showing dietary variations related to the time of day, lunar phase, and season, and D. labrax showing variations with the time of day and season. [ABSTRACT FROM AUTHOR]

Simple Summary: Where teleost fish are concerned, the effects of a dietary tryptophan surplus are mostly immunosuppressive, making it a potential dietary anti-inflammatory strategy. The goal of the present work was to evaluate the effects of tryptophan dietary supplementation on immune and neuroendocrine responses of the European seabass, Dicentrarchus labrax, undergoing chronic inflammation. Juvenile European seabass were intraperitoneally injected with an inflammatory agent (inflamed group) or a saline solution (control group). Within each group, fish were fed a control and a control-based diet supplemented with tryptophan for 4 weeks. Different tissues were sampled every week for the assessment of immune-related parameters. When tryptophan was provided to fish undergoing inflammation, the gene expression of a macrophage marker increased sooner and remained high until the end of the experiment. The same fish showed a concurrent increase in peripheral monocyte counts. After one week, molecular patterns of anti-inflammatory processes seemed to be favoured by tryptophan. Altogether, results show that a short administration period seems to be critical where tryptophan supplementation is concerned since at later inflammatory stages—and longer feeding periods—fish fed this diet displayed a molecular profile similar to that of fish fed a control diet. Where teleost fish are concerned, studies in tryptophan immunomodulation generally point to immunosuppressive properties, thus presenting a potential anti-inflammatory dietary strategy. The goal of the present work was to evaluate the effects of tryptophan dietary supplementation on immune and neuroendocrine responses of the European seabass, Dicentrarchus labrax, undergoing chronic inflammation. Juvenile European seabass were intraperitoneally injected with either Freund's Incomplete Adjuvant (FIA, inflamed group) or a saline solution (control group). Within each group, fish were fed a control (CTRL) and a CTRL-based diet supplemented with tryptophan (0.3% DM basis; TRP) for 4 weeks. Different tissues were sampled every week for the assessment of immune-related parameters. When TRP was provided to FIA-injected fish, mcsfr gene expression increased from 1 to 2 weeks and remained high until the end of the experiment. The same fish showed a concurrent increase in peripheral monocyte counts. Moreover, il34 expression at 1 week post-FIA injection was higher in TRP-fed than in CTRL-fed fish. After one week, molecular patterns of anti-inflammatory processes seemed to be favoured by TRP (mcsfr, gr1, il34 and tgfβ). Altogether, the results show that the feeding period seems to be critical where tryptophan supplementation is concerned since at later inflammatory stages—and longer feeding periods—fish fed TRP displayed a molecular profile similar to that of the CTRL group. In contrast, shorter administration periods might accelerate immune regulatory pathways. [ABSTRACT FROM AUTHOR]

Simple Summary: SCFAs are considered functional ingredients as they promote the growth and health of fish. This work aimed to assess the effect of short-chain fatty acids (SCFAs) on the immune status of the European sea bass gut through the ex vivo use of intestinal explants. The ex vivo technique significantly reduces the number of animals to be used, according to the guidelines of the 3Rs. The present results are important to understand how European sea bass respond to a bacterial infection after the administration of SCFAs and for the evaluation of functional ingredients used in aquaculture. This study aimed to evaluate the intestinal interactions between three short-chain fatty acids (SCFA), namely, acetate, propionate, and butyrate, and pathogenic bacteria (Vibrio anguillarum) in intestinal explants of European sea bass (Dicentrarchus labrax) juveniles. The anterior intestine of 12 fish with an average weight of 100 g (killed by excess anesthesia with 2-phenoxyethanol) were sampled and placed in 24-well plates. The experimental treatments consisted of a control medium and a control plus 1 mM or 10 mM of sodium acetate (SA), sodium butyrate (SB), and sodium propionate (SP). After 2 h of incubation, the explants were challenged with Vibrio anguillarum at 1 × 107 CFU/mL for 2 h. After the bacterial challenge, and regardless of the SCFA treatment, the oxidative stress-related genus catalase (cat) and superoxide dismutase (sod) were down-regulated and glutathione peroxidase (gpx) was up-regulated. Furthermore, the immune-related genes, i.e., the tumor necrosis factor (TNF-α), interleukin 8 (IL-8), transforming growth factor (TGF-β), and nuclear factor (NF-Kβ) were also up-regulated, and interleukin 10 (IL-10) was down-regulated. During the pre-challenge, sodium propionate and sodium butyrate seemed to bind the G-protein coupled receptor (grp40L), increasing its expression. During the challenge, citrate synthase (cs) was down-regulated, indicating that the SCFAs were used as an energy source to increase the immune and oxidative responses. Overall, our results suggest that sodium propionate and sodium butyrate may boost European sea bass immune response at the intestine level. [ABSTRACT FROM AUTHOR]

This study aimed to explore the effect of FM substitution by defatted Tenebrio molitor larvae meal (dTM) on the response of European seabass to an acute stress challenge. An FM-based diet was used as a control and two other isoproteic/isoenergetic diets were formulated to replace 50 and 100% of FM by dTM. Each diet was tested in quadruplicate groups of 15 fish (69 ± 5 g) fed until visual satiety for 16 weeks. After the feeding trial, fish were subjected to 1 min air exposure followed by 1 h of recovery before sampling. The haematological profile, plasma metabolites, and humoral immunity biomarkers, as well as hepatic oxidative stress and antioxidant capacity, were analysed. A clear response to acute stress was observed by a significant increase in haemoglobin, haematocrit, red blood cells, and almost all evaluated plasma metabolites and humoral parameters, regardless of dietary treatment. The obtained results demonstrated that partial substitution of FM by IM did not affect the stress response of seabass. However, total FM replacement increased the hepatic activity of total peroxidase and superoxide dismutase in fish fed TM100. [ABSTRACT FROM AUTHOR]

Anthropogenic activities lead to the spread of chemicals and biological materials, including plastic waste, toxic metals, and pharmaceuticals, of which the impact on the Mediterranean Sea is of high concern. In this context, the EU Interreg Italy-Albania-Montenegro Project "ADRINET (Adriatic Network for Marine Ecosystem) _244" (2018–2020) arises. It aims to carry out biomonitoring campaigns in the main commercial interest of fish and cephalopod species, such as Sparus aurata, Dicentrarchus labrax, Sepia spp., and Loligo spp. sampled in three different subregions of the Mediterranean Sea. The presence of the main environmental contaminants, such as cadmium, microplastics, and antibiotics was investigated in these seafood samples. Contamination by cadmium and antibiotics in the seafood investigated in our study was negligible. However, a high value of microplastics was detected in the stomach and gut of Sparus aurata and Dicentrarchus labrax. Overall, even though the presence of microplastics needs to be investigated by further studies, the results confirmed that the environmental conditions of the three bays investigated by the ADRINET project partners (Italy, Albania, Montenegro) are positive and not affected by intensive anthropogenic activity. [ABSTRACT FROM AUTHOR]

The present study aims to investigate the influence of zeolite usage and stocking densities on various parameters, including ammonia removal from water, accumulation of heavy metals in fish organs, water quality, growth performance, feed efficiency, muscle composition, as well as hematological and biochemical parameters in European seabass (Dicentrarchus labrax) over a 90-day duration. A total of 2400 D. labrax with an initial weight of 9.83 ± 2.02 g and initial length of 9.37 ± 0.32 cm were distributed among 24 tanks. The research involved six distinct treatment groups, with two different zeolite levels (0 and 15 ppt) and three stocking density levels (50, 100, and 150 fish/m3), each replicated four times. The results of the research demonstrate a statistically significant improvement (p < 0.05) in water quality measures with the introduction of zeolite. The successful implementation of this amendment mitigated the adverse effects of fish density on water quality parameters. Higher stocking density negatively impacted European sea bass growth, feed utilization, and hemato-biochemical indicators. Zeolite use effectively alleviated these adverse effects, particularly on performance, feed utilization, hematological, and biochemical parameters. The study's results indicate that the utilization of zeolite has shown to be efficacious in mitigating the accumulation of heavy metals in both water and fish organs, while concurrently augmenting fish attributes. However, the increase in density led to a significant decrease in the accumulation of heavy metals in both water and fish organs. The present study highlights the capacity of natural zeolites to mitigate the negative consequences associated with water quality concerns. The efficiency of these zeolites in limiting the accessibility of heavy metals in polluted water is shown, hence minimizing their accumulation in fish organs. In addition, the improvement of fish performance has the capacity to have a beneficial influence on both the well-being and efficiency of fish in aquaculture. Additional research is essential to fully understand the complex molecular pathways involved in utilizing natural zeolite under different fish densities. [ABSTRACT FROM AUTHOR]