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Ice-stored farmed barramundi (Lates calcarifer), snubnose pompano (Trachinotus blochii) and sobaity bream (Sparidentex hasta), as well as wild-caught cobia (Rachycentron canadum), coral trout (Plectropomus leopardus), giant trevally (Caranx ignobilis), milkfish (Chanos chanos) and mangrove red snapper (Lutjanus argentimaculatus), were compared for their freshness/spoilage using sensory, chemical and microbiological methods. Quality Index Method schemes were developed to determine alterations in the sensory freshness. The shelf lives ranged from 8 (coral trout) to 18 days (sobaity bream). The farmed species always exhibited a significantly longer shelf life than the wild-caught species. The adenosine triphosphate (ATP) breakdown followed different patterns in the studied species. The K-values at the time of sensory rejection ranged from 30 to 80% depending on the species, while the microbial load reached or exceeded a level of 6 log cfu/g. Although the shelf life duration was dependent on the origin of the fish (wild or farmed), the ATP breakdown scheme, as well as the K-values and microbial loads at the time of rejection, were species-dependent and independent of the origin. [ABSTRACT FROM AUTHOR]

Understanding the behaviour and ecological role of elasmobranchs is essential for their conservation, particularly in regions harbouring threatened and data-deficient species like the Inhambane coastline in southern Mozambique, southwestern Indian Ocean. This study employed long-life remote underwater video cameras (LL-RUV) to observe elasmobranch occurrence and behaviour at a rocky reef near Praia do Tofo known for frequent elasmobranch sightings. Between 2021 and 2024, 524 hours of LL-RUV data were collected, revealing the presence of 14 threatened and data-deficient elasmobranch species. Reef manta rays (Mobula alfredi), small eye stingrays (Megatrygon microps), and oceanic manta rays (Mobula birostris) were identified as the primary elasmobranch users of the studied cleaning stations (n = 81, n = 72 and n = 61 respectively), engaging in mutualistic interactions with cleaner fish and spending significant amounts of time at the studied reef. In contrast, spotted eagle rays (Aetobatus narinari) and blacktip sharks (Carcharhinus limbatus) were solely observed cruising over the reef without engaging in cleaning interactions (n = 40 and n = 27 respectively). In addition, this study provides evidence of intra- and inter-specific interactions between reef and oceanic manta rays, small eye stingrays and bowmouth guitarfish (Rhina ancylostoma) and co-occurrences of both manta ray species and smalleye stingrays with "hitchhiker" species including cobia (Rachycentron canadum) and remoras (Echeneis spp.). The use of LL-RUV cameras represents a significant advancement in marine research. These cameras enable continuous, non-intrusive, long-term monitoring of marine environments, capturing natural behaviours, while minimising disturbances caused by divers. As a result, more accurate observations of elasmobranch behaviour and cleaning station dynamics can be recorded, which might be missed during short-term surveys. This research highlights the potential of LL-RUV cameras as powerful tools for advancing our understanding of elasmobranch occurrence and behaviour and underscores their value in informing targeted and effective conservation strategies. Beyond elasmobranch research, LL-RUVs hold tremendous potential for studying a wide range of marine species and habitats, offering a versatile tool for ecological monitoring and conservation efforts across diverse marine ecosystems. [ABSTRACT FROM AUTHOR]

Introduction: This study explored the effects of increased water temperatures and limited feeding on the growth, feed utilization, and nutrient retention in juvenile cobia (Rachycentron canadum). Methods: Juvenile cobia, approximately 5.0 g in body weight, were distributed across two temperature conditions: 34°C, to mimic a global warming scenario, and 30°C, the current local summer average, as controls. The setup included eighteen 200-liter tanks, with 20 fish per tank. Within each temperature regime, triplicate tanks received one of three feeding levels (55%, 75%, and 95% of satiation as determined at 30°C) over a six-week period. Results: The findings indicated that cobia exhibited the poorest growth performance at the elevated temperature (34°C) and the lowest feeding level (55%). These conditions also correlated with the lowest protein efficiency ratio and feed intake. The feed conversion ratio worsened with increased temperature and feeding levels, while protein production values decreased at higher temperatures. A lower feeding level caused a lower total lipid retention but led to increased retention of whole body essential amino acids. Discussion: After six weeks, a 24-hour post-prandial analysis showed selective retention of some amino acids in muscle and plasma, but significantly higher retention in the liver at the higher temperature. Only a few amino acids' retention was influenced by feeding level. These results suggest that temperature and feeding levels alter the prioritization of amino acid metabolism and retention, as well as the utilization of energy and substrates across different organs of the cobia. [ABSTRACT FROM AUTHOR]

Rachycentron canadum (cobia) is a marine fish species important to fisheries and aquaculture worldwide. The species has gathered scientific attention in the last decades, and today, a considerable body of knowledge exists on it. There are several reviews pertaining to different aspects of research, but a quantitative outlook has been lacking to identify contributors and motives for research on cobia. This study aims to present the first global research performance analysis on R. canadum through scientometrics. We found a total of 446 documents, published in the timespan of 1964–2023, from a variety of countries and sources. Although various countries have published studies on the species, a few countries concentrate the vast majority of research efforts. The most cited articles and the sources with most publications were mainly aquaculture-related. Some countries with high contribution to capture have a significant portion of their scientific production directed to aquaculture-related sources, while others have low scientific production in general. Some countries where the cobia fishery is present have had no research found at all. The boom in publication rate from the 2000s onwards exhibits a similar tendency to the rate of aquaculture production over the years, with aquaculture probably representing the main research driver for R. canadum. We recommend focusing additional scientific endeavors on wild cobia populations in countries where its fishery holds significance. Furthermore, we suggest that the currently existing aquaculture focus on the species may overshadow research interest on its fisheries. [ABSTRACT FROM AUTHOR]

ABSTRACT The cobia (Rachycentron canadum) is important to fisheries in Northeastern Brazil. To restore stocks in Rio Grande do Norte, cobia were stocked and the fishery was monitored over 4 years. We evaluated effects of stocking on cobia size composition in this data‐limited fishery to understand stocking limitations and explore possibilities for future projects. Total length of cobia was significantly shorter after stocking than before stocking, with mostly small fish caught mainly by nets, an unusual pattern for cobia. Total length also varied significantly among bottom types. Most of the cobia harvested were below the size at first maturity, which suggests that stocking increased the catch, but most fish harvested were immature, thereby potentially hindering stock recovery. For future projects, we recommend against the use of plastic tags for tagging hatchery cobia and propose releases that emulate natural spawning dynamics, alongside releasing fish at older ages. Further, we recommend robust post‐stocking fishery monitoring, and management strategies, such as a release of net‐caught cobia in the initial 2 years and incorporating validated fisher knowledge into decision‐making. [ABSTRACT FROM AUTHOR]

Pisciculture encounters an array of intricate challenges that span disease management, preservation of water quality, prevention of genetic hybridization, ensuring the integrity of net systems, sourcing sustainable aquatic feed, and comprehending fish growth and reproductive dynamics. Addressing these multifaceted challenges necessitates a comprehensive research approach. This study employs an innovative synergy of fuzzy logic and deep learning techniques, resulting in a robust strategy to tackle these obstacles effectively. Fuzzy logic excels in assessing stressed fish conditions by handling inherent uncertainties. Simultaneously, YOLOv7 with fuzzy color enhancement (YOLOv7FCE) is used to detect damaged fish nets, thereby mitigating losses and upholding the integrity of the net infrastructure. This approach also leverages YOLOv7FCE for identifying Cobia fish within shoals, streamlining the identification process. Subsequently, DeepLabv3 is implemented to meticulously segment the recognized Cobia fish, facilitating precise measurements of their physical attributes. This comprehensive methodology yields profound insights into growth patterns and feeding tendencies within the confined aquatic environment. By embracing this approach, the research presents a versatile and adaptive framework that not only enhances our comprehension of piscine dynamics but also holds the potential to revolutionize the aquaculture industry. [ABSTRACT FROM AUTHOR]

Increased interest in marine fish farming in the United States has led to a need for fundamental economic information on production of candidate species for commercialization in various production systems. Funding for the project targeted those species with potential for production in southern tier states in the United States. Sufficient technical data were found to develop comprehensive budget analyses to estimate growout production costs for four scales of production for each of 10 species with potential for production in ponds, 13 in recirculating aquaculture systems (RAS), and five in net pens. The choice of species/production system scenarios was based on evidence of successful production on farms or in research. Estimation of production costs with enterprise budgets can provide useful guidance to identify the types of improved efficiencies that have the greatest effect on economic viability even when commercial farm data are not available. Commercial farm data were used where available, but for most species, data were available only from studies conducted under research conditions. Per‐kg costs of production were lowest for net pen production, followed by ponds, with production costs in RAS two to five times greater than in ponds or net pens. Ponds and net pens generally exhibited greater efficiency of use of capital assets across species than did RAS that resulted in lower percentages of fixed costs and lower annual costs per kg of fish produced. All five species evaluated for net pen production were estimated to be profitable, including redfish, Sciaenops ocellatus (also known as red drum), striped bass, Morone saxatilis, cobia, Rachycentron canadum, red snapper, Lutjanus campechanus, and seriolids (generic budget for almaco jack, Seriola rivoliana, California yellowtail, Seriola lalandi, and greater amberjack, Seriola dumerili), four in ponds (redfish, hybrid drum, ♀Pogonias cromis × ♂Sciaenops ocellatus, black sea bass, Centropristis striata, and cobia), but none of the RAS scenarios showed profitability at average yields (kg/cubic meter) reported in the literature. Comprehensive data on growout production of marine finfish species in the United States is generally lacking, and there is a strong need for production trials conducted under near‐commercial conditions with an endpoint of market‐sized fish. Production trials should be conducted in ponds (≥0.1 ha), net pens, and RAS tanks of a size that simulate commercial production conditions. Adequate production trial databases would provide opportunities to develop economic optimization models that would provide useful guidance for prospective producers. Average yields (kg/cubic meter) in RAS will need to be much greater than currently reported in the research literature for RAS production to be economically sustainable. Net pen production appears to be profitable in the United States, but effective permitting procedures are not in place. Providing research support for the US redfish sector that has developed effective production and marketing models could serve as a foundation for developing additional species and offer opportunities for diversification on marine finfish farms. [ABSTRACT FROM AUTHOR]

The current study sought to determine the levels of radioactivity and heavy metal contamination in 22 dried fish samples collected in Chennai, Tamil Nadu. The study found that there were substantial heavy metals concentrations for Pb, Mn, Cr, Co, and Cd. The concentration of heavy metal Pb being alarmingly high (32.85 to 42.09 mg/kg), followed by Cd (2.18 mg/kg to 3.51 mg/kg) than the permissible limit of WHO (2.17 mg/kg) for Pb and (0.05 mg/kg) for Cd. In terms of radioactivity, the gross alpha activity in the dried fish samples ranged 6.25 ± 0.12 to 48.21 ± 0.11 Bg/kg with an average of 20.35 Bg/kg and with a gross beta activity from 6.48 ± 0.02 to 479.47 ± 0.65 Bg/kg, for an average of 136.83 Bg/kg. The study found that the internal radiation dose that people receive upon consuming the fish species Sphyraena obtusata, Rachycentron canadum, Lepidocephalichthys thermalis, Synodontidae, Carangoides malabaricus, Sardina pilchardus, Scomberomorus commerson, Sillago sihama, Gerres subfasciatus, and Amblypharyngodon mola is above the ICRP-recommended limit of less than 1 mSv/year. Annual gonadal dose equivalent (AGDE) and total excessive lifetime cancer risk (ELCR) ranged 0.488 µSv year−1 and 0.004 µSv year−1 respectively, the values of AGDE being higher than the global average value. The findings of the study indicate that the analyzed dried fish samples are contaminated with Pb and Cd, which shall pose cancer risk to the consumers as a result. [ABSTRACT FROM AUTHOR]

Understanding fisheries requires not only traditional modelling approaches but also the incorporation of local ecological knowledge (LEK) which can provide other types of essential contextualizing knowledge.Recreational anglers within the cobia fishery on the east coast of central and northern Florida target cobia by seeking out the manta rays cobia often follow and associate with, and casting at or near them. Results suggest this fishery poses a threat of entanglement, injury and disturbance to mantas in the region, especially associated with the practices and behaviours of inexperienced anglers.Expert angler responses in interviews described changes in manta and cobia habitat use and reductions in cobia abundanceExperienced anglers pointed to social media as a key driver of the expansion of this fishery and as an explanation for their perception of the growing presence of novice anglers engaged in these practices. Respondents proposed best practices and potential management interventions and generally supported conservation action, including through willingness to engage with researchers and support management and enforcement measures related to the fishery. [ABSTRACT FROM AUTHOR]

It is widely believed that a significant portion of the gut microbiota, which play crucial roles in overall health and disease, originates from the food we consume. Sashimi is a type of popular raw seafood cuisine. Its microbiome, however, remained to be thoroughly explored. The objective of this study is to explore the microbiome composition in sashimi at the time when it is served and ready to be eaten. Specifically, our tasks include investigating the diversity and characteristics of microbial profiles in sashimi with respect to the fish types. We utilized the Sanger-sequencing based DNA barcoding technology for fish species authentication and next-generation sequencing for sashimi microbiome profiling. We investigated the microbiome profiles of amberjack, cobia, salmon, tuna and tilapia sashimi, which were all identified using the MT-CO1 DNA sequences regardless of their menu offering names. Chao1 and Shannon indexes, as well as Bray–Curtis dissimilarity index were used to evaluate the alpha and beta diversities of sashimi microbiome. We successfully validated our previous observation that tilapia sashimi has a significantly higher proportions of Pseudomonas compared to other fish sashimi, using independent samples (P = 0.0010). Salmon sashimi exhibited a notably higher Chao1 index in its microbiome in contrast to other fish species (P = 0.0031), indicating a richer and more diverse microbial ecosystem. Non-Metric Multidimensional Scaling (NMDS) based on Bray–Curtis dissimilarity index revealed distinct clusters of microbiome profiles with respect to fish types. Microbiome similarity was notably observed between amberjack and tuna, as well as cobia and salmon. The relationship of microbiome similarity can be depicted as a tree which resembles partly the phylogenetic tree of host species, emphasizing the close relationship between host evolution and microbial composition. Moreover, salmon exhibited a pronounced relative abundance of the Photobacterium genus, significantly surpassing tuna (P = 0.0079), observed consistently across various restaurant sources. In conclusion, microbiome composition of Pseudomonas is significantly higher in tilapia sashimi than in other fish sashimi. Salmon sashimi has the highest diversity of microbiome among all fish sashimi that we analyzed. The level of Photobacterium is significantly higher in salmon than in tuna across all the restaurants we surveyed. These findings provide critical insights into the intricate relationship between the host evolution and the microbial composition. These discoveries deepen our understanding of sashimi microbiota, facilitating our decision in selecting raw seafood. [ABSTRACT FROM AUTHOR]

The present study aims to evaluate methanol-extracted cottonseed meal (CSM) as a potential replacement for fishmeal (FM) in aquafeeds for juvenile cobia Rachycentron canadum. Five isonitrogenous (41% crude protein) and isolipidic (11% crude lipid) diets were formulated with 0 (i.e., the full fishmeal diet, as Control), 25%, 50%, 75% and 100% of the dietary protein from FM replaced by methanol-extracted CSM with L-lysine (L-Lys) and DL-methionine (DL-Met) and supplemented to the established requirement levels for cobia. Diets were fed to triplicate groups of juvenile fish with an average initial weight (±SEM) of 11.35 ± 0.23 g/fish for 9 weeks. Percent weight gain (WG), feed efficiency (FE) and protein efficiency ratio (PER) of fish fed diets with 25% and 50% of FM protein replaced by methanol-extracted CSM were higher or comparable to those of fish fed the Control diet. Those responses were gradually reduced with increasing levels of CSM substitution, resulting in significant (p < 0.05) negative linear trends. Condition factor (CF) and hepatosomatic index (HSI) values significantly decreased with increasing dietary CSM inclusion, as did whole-body protein and lipid composition. Activities of superoxide dismutase (SOD) of fish fed CSM diets were not significantly different compared to that of fish fed the Control diet. The glutathione peroxidase (GSH-Px) and malonaldehyde (MDA) levels, as well as serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities from fish fed diets with 50% or greater of CSM were lower than those of fish fed the Control and CSM25 diets. These results indicated that the inclusion of CSM did not induce any apparent stress on juvenile cobia. Additionally, methanol-extracted CSM with Lys and Met supplementation was able to replace up to 20~30% of crude protein provided by FM in the diet of cobia without drastically affecting the growth performance or body composition. [ABSTRACT FROM AUTHOR]

The escalating global demand for fish protein necessitates the expansion of aquaculture from land to sea, facilitated by floating sea cages. In this study, the National Institute of Ocean Technology (NIOT), Chennai, Tamil nadu conducted a pilot-scale culture of hatchery-reared cobia seeds (Rachycentron canadum) in HDPE collar floating cages (9 m diameter with a cultivable volume of 320 m³). These cages were strategically deployed at Olaikuda (Gulf of Mannar, Tamil Nadu) and Thuplipalem (Andhra Pradesh), representing semi-protected (SP) and open sea (OS) environments respectively. The evaluation focused on growth performance, with cobia seeds stocked in cages at an initial biomass of 150 g/m³ (SP) and 154 g/m³ (OS), featuring an initial average weight of 32.49 ± 1.77 g and a total length of 15.6 ± 0.91 cm during stocking. In SP site, cobia exhibited significant growth, reaching an average weight of 3830 g in 270 days, with a specific growth rate (SGR) of 1.76% with a survival rate of 77%. In contrast, despite the longer culture period of 322 days at the OS site, lower average weight of 2550 g with an SGR of 1.35% with survival rate 62% at SP. Physicochemical and biological parameters at both sites remained within optimal ranges. Notably, the OS site experienced higher wave heights (ranging from 0.56 to 2.28 m); potentially impacting feeding patterns, high energy expenditure due to the exposed weather conditions resulted into reduced growth rate compared to the sheltered bay. This study aims to elucidate the comparative suitability of environmental settings and its economic feasibility for open sea cage farming. [ABSTRACT FROM AUTHOR]

The cobia Rachycentron canadum, mainly distributed in the warm waters of tropical and subtropical regions around the world, remains a fish of considerable economic importance. Detailed diversity and the number of microsatellite sequences in the cobia genome are still unintelligible. The primary aim of this work was to identify and quantify the miscellaneous SSR sequences in the cobia genome. More than 280,000 sequences were sequenced and screened using next‐generation sequencing technology and microsatellite identification. Perfect mononucleotide repeats, dinucleotide microsatellites, and trinucleotide microsatellites contain (A)10/(T)10, (AC)6/(TG)6, and (AAT)5–32 as the largest number of motifs in each type of microsatellite, respectively. The tetranucleotide and pentanucleotide microsatellites (TTM and PTM) consist of the largest number of motifs of both (ATCT)5–32 and (TCAT)5–31 in TTMs, and (CTCTC)5–9 in PTMs, whereas the hexanucleotide microsatellites are rarely observed in the cobia genome. All c. 38000 sequences of composite microsatellites are extremely diverse, including compound (11.71%), interrupted compound (71.77%), complex (0.45%), and interrupted complex (16.07%). In this study, we developed a convenient and useful recording system for writing down and categorizing diverse composite microsatellite types. This system will provide great support for exploring repeat origins, evolutionary mechanisms, and the application of polymorphic microsatellites. [ABSTRACT FROM AUTHOR]

Background Cobia (Rachycentron canadum) is the only member of the Rachycentridae family and exhibits considerable sexual dimorphism in growth rate. Sex determination in teleosts has been a long-standing basic biological question, and the molecular mechanisms of sex determination/differentiation in cobia are completely unknown. Results Here, we reported 2 high-quality, chromosome-level annotated male and female cobia genomes with assembly sizes of 586.51 Mb (contig/scaffold N50: 86.0 kb/24.3 Mb) and 583.88 Mb (79.9 kb/22.5 Mb), respectively. Synteny inference among perciform genomes revealed that cobia and the remora Echeneis naucrates were sister groups. Further, whole-genome resequencing of 31 males and 60 females, genome-wide association study, and sequencing depth analysis identified 3 short male-specific regions within a 10.7-kb continuous genomic region on male chromosome 18, which hinted at an undifferentiated sex chromosome system with a putative XX/XY mode of sex determination in cobia. Importantly, the only 2 genes within/between the male-specific regions, epoxide hydrolase 1 (ephx1 , renamed cephx1y) and transcription factor 24 (tcf24 , renamed ctcf24y), showed testis-specific/biased gene expression, whereas their counterparts cephx1x and ctf24x , located in female chromosome 18, were similarly expressed in both sexes. In addition, male-specific PCR targeting the cephx1y gene revealed that this genomic feature is conserved in cobia populations from Panama, Brazil, Australia, and Japan. Conclusion The first comprehensive genomic survey presented here is a valuable resource for future studies on cobia population structure and dynamics, conservation, and evolutionary history. Furthermore, it establishes evidence of putative male heterogametic regions with 2 genes playing a potential role in the sex determination of the species, and it provides further support for the rapid evolution of sex-determining mechanisms in teleost fish. [ABSTRACT FROM AUTHOR]

Contaminated fungi on dried salted fish of three species including Talang queenfish (TQF, Scomberroides commersonianus), Hamilton's thryssa fish (HTF, Thryssa hamiltonii), and Cobia fish (CF, Rachycentron canadum) were isolated and identified. One hundred and sixty‐nine isolates were obtained from TQF and HTF, respectively, while no fungi were detected in CF. The dominant genera were Aspergillus spp. (n = 79), Penicillium spp. (n = 60), and non‐sporulating fungi (n = 30). The representative groups of Aspergillus spp. (n = 6) and Penicillium spp. (n = 3) based on different morphological characteristics were selected for species identification by molecular methods involving ITS1‐5.8s‐ITS2 region and Matrix‐Assisted Laser Desorption/Ionization Time‐of Flight Mass Spectrometer (MALDI‐TOF MS) analysis. The nine isolates were identified to be Aspergillus versicolor (n = 2), Aspergillus montevidensis (n = 3), Penicillium citrinum (n = 3), and Aspergillus sp. (n = 1). The antifungal activity of chitooligosaccharide‐gallic acid (COS‐GAL) conjugate against A. versicolor F1/10M9, A. montevidensis F1/30M20, and P. citrinum F1/23M14 was examined. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values were in the range of 0.625–2.5 mg/mL and 1.25–10 mg/mL, respectively. COS‐GAL conjugate at the concentration of 5 mg/mL completely inhibited the spore germination of A. versicolor F1/10M9 and P. citrinum F1/23M14 after 72 h of treatment. COS‐GAL conjugate at 4 × MIC mainly affected the mycelium of A. versicolor F1/10M9 and P. citrinum F1/23M14 after treatment with COS‐GAL conjugate for 3 days by coating mycelium surface and reducing the size of mycelium. Therefore, COS‐GAL conjugate could be used as a food additive to inhibit or prevent the growth of fungi contaminated in dried salted fish or other relevant products. Practical Application: During processing, dried salted fish can be contaminated with fungi, which may cause food poisoning and food spoilage. The contaminated fungi are capable of producing mycotoxin that is harmful to consumers. Synthetic food preservatives have long been used to inhibit fungal growth, but the side effects to consumers are of concern. Chitooligosaccharide is a nontoxic chitosan derivative produced from shrimp shell and its conjugate namely chitooligosaccharide‐gallic acid conjugate showed high efficacy in inhibiting the growth of fungi including Aspergillus spp. and Penicillium spp. Therefore, it can serve as a natural alternative preservative for the prevention of fungal growth in dried salted fish. [ABSTRACT FROM AUTHOR]

Cobia (Rachycentron canadum) is a coastal pelagic migratory fish species of tropical and subtropical waters, where it is an important game fish and it has been commercially expanded in offshore aquaculture systems. Understanding population connectivity is of utmost importance to the sustainable use and conservation of aquatic resources, and information on genetic diversity and structure is key element in unraveling differentiation when no clear physical barriers exist. In the present study, cobia genetic diversity and structure were depicted using mitochondrial DNA cytochrome b sequencing and microsatellite genotyping in samples from the Southwestern Atlantic and showed that a major single population inhabits the southern hemisphere. Cytochrome b sequencing also suggested that the Indian Ocean is the center of origin for this species' diversification. A hierarchical analysis of AMOVA compared sampling locations from the Northwestern Atlantic (from a previous study) with the Southwestern ones using nine shared microsatellite markers. Differentiation among groups (FCT = 0.41), Bayesian clustering analysis, and complementary ordination analyses (by discriminant analysis of principal components [DAPC] and factorial correspondence analysis [3D‐FCA]) presented a clear separation between the two hemispheres, supported by a Lagrangian model that explained the ocean dynamics over larval retention on the Western Atlantic. Another genetic subgroup intermingled with the main Southwestern group may also exist further south, probably associated with the Vitória‐Trindade Ridge and the local current systems. The distribution of this species in metapopulations is of extreme relevance for fisheries and fish hatcheries management in the Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Feed is the main source of material and energy for farmed fish, and its nutritional value and balance are important factors affecting fish's growth rate and physical health. In order to explore the effects of two different feed sources on the growth, serum biochemical indexes, liver antioxidant capacity, and lipid metabolism of young cobia fish, 300 young cobia fish with an initial body weight of 43.14 ± 1.25 g were selected for the experiment and randomly divided into two treatments. Each treatment had five replicates, and each replicate had 30 fish. They were fed with formulated feed and frozen fresh fish, respectively, for 12 weeks. The results showed that the weight gain rate, specific growth rate, and feed conversion rate of juvenile cobia fish fed with formulated diet were extremely significantly lower than those of the frozen fresh fish group (P < 0.01), and condition factor was significantly lower than that of the frozen fresh fish group (P < 0.05). However, protein efficiency rate, hepatosomatic index, and viscerosomatic index were significantly higher than those of frozen fresh fish group (P < 0.05). The content of water, crude protein, and crude ash in the whole fish had no significant difference (P > 0.05), while the content of crude lipid decreased significantly (P < 0.05). The serum aspartate aminotransferase activity and sugar content of cobia in the formulated diet group were significantly higher than those in the frozen fresh fish group (P < 0.05). In contrast, the total cholesterol, triglyceride content, alkaline phosphatase activity, and phosphorus content were significantly lower than those in the frozen fresh fish group (P < 0.05). Compared with the frozen fresh fish group, the antioxidant enzyme activities in the liver of the formulated diet group were significantly decreased (P < 0.05) except malondialdehyde (MDA) and the activity of fatty acid synthase, while there was no significant difference in the malate dehydrogenase. The study showed that under the experimental conditions, frozen fresh fish was more suitable for feeding juvenile cobia, and the formulated diet had adverse effects on the liver of juvenile cobia. Therefore, the nutritional composition of frozen fresh fish and the metabolic characteristics of cobia were used for reference to optimize and adjust the nutritional formula of juvenile cobia. [ABSTRACT FROM AUTHOR]

The bacterial community of the intestinal microbiota influences many host functions, and similar effects have been recently reported for the fungal community (mycobiota). Cobia is a tropical fish that has been studied for its potential in marine aquaculture. However, the study of its bacterial community has been underreported and the mycobiota has not been investigated. We analyzed the gut bacterial and fungal profile present in the intestinal mucosa of reared adult cobias fed two diets (frozen fish pieces (FFPs) and formulated feed (FF)) for 4 months by sequencing the 16S rRNA (V3-V4) and internal transcribed spacer-2 (ITS2) regions using Illumina NovaSeq 6000. No significant differences in the alpha diversity of the bacterial community were observed, which was dominated by the phyla Proteobacteria (~96%) and Firmicutes (~1%). Cobia fed FF showed higher abundance of 10 genera, mainly UCG-002 (Family Oscillospiraceae) and Faecalibacterium, compared to cobia fed FFPs, which showed higher abundance of 7 genera, mainly Methylobacterium-Methylorubrum and Cutibacterium. The inferred bacterial functions were related to metabolism, environmental information processing and cellular processes; and no differences were found between diets. In mycobiota, no differences were observed in the diversity and composition of cobia fed the two diets. The mycobiota was dominated by the phyla Ascomycota (~88%) and Basidiomycota (~11%). This is the first study to describe the gut bacterial and fungal communities in cobia reared under captive conditions and fed on different diets and to identify the genus Ascobulus as a new member of the core fish mycobiota. [ABSTRACT FROM AUTHOR]

This article attempts to spatially envision the chamber, based on descriptions in surveys conducted in mid-16th century Seville. Besides distinguishing the chamber from other spaces, we examine its constitutive features: ceilings, walls and floors. We also analyse the different locations of these spaces within the house and, if mentioned, who made use of them. To this end, in addition to exploring the technical use of words linked to the chamber (ajembrilla, alcatifa, alizar, almojaira, asnado, costanera, cabio, mazarí, olambre or hocino), we include drawings and recreations based on some of the survey descriptions. [ABSTRACT FROM AUTHOR]

This study aimed to determine the impact of elevated temperature combined with different levels of dietary methionine concentrations on feed intake (FI) and brain expression of selected neuropeptides and one receptor involved in appetite control in juvenile cobia (approximately 3.7 g body weight). The genes studies were neuropeptide y, npy; agouti-related protein, agrp; cocaine- and amphetamine-regulated transcript, cart; cholecystokinin, cck and melanocortin 4 receptor; mc4r. The cobia were reared at typical sea water temperature in Vietnam (30 °C) and elevated temperature (34°C; selected as one of the predicted scenarios of climate change). The fish were fed diets with different levels of methionine: deficient (M9; 9.1 g/kg), sufficient (M12; 12.8 g/kg) and surplus (M16, 16.8 g/kg) for 6 weeks (triplicate tanks per treatment). Both dietary methionine concentration and temperature affected FI in cobia. Dietary methionine deficiency (i.e., M9) and elevated temperature reduced FI in cobia. Temperature significantly influenced the mRNA expression of agrp, cart, cck and mc4r. Expression of the orexigenic neuropeptide npy was consistently higher before the meal than after the meal for all diets and at both temperatures. At 30°C, prefeeding levels of npy correlated with both increased methionine levels and FI. The interaction between dietary methionine and temperature on the levels of brain npy expression was significant (P

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Incorporating environmentally sustainable plant-based protein sources into aquafeeds is a priority for the aquaculture industry. Wheat gluten as a plant protein source has been successfully integrated into feeds for several fish species. However, unique nutritional requirements and the potential for intolerances necessitate the evaluation of plant-based diets by species. Previous work by our laboratory indicated that wheat gluten at less than 4% inclusion in a compound feed had a negative impact on growth and survival rate in juvenile cobia (Rachycentron canadum). In the current study, we evaluated the effects of wheat gluten inclusion in a plant-based diet in juvenile European sea bass (Dicentrarchus labrax). No major differences were observed in terms of growth rate, plasma biochemical parameters, detectable induction of plasma IgM, IgT, or factors capable of binding gliadin in response to the inclusion of 4% dietary wheat gluten. However, plasma levels of taurine doubled in the fish fed wheat gluten, and there were considerable changes to the intestinal microbiome. Despite these measurable changes, the data suggest that dietary inclusion of 4% wheat gluten is well tolerated by juvenile European sea bass in a plant-based feed formulation. [ABSTRACT FROM AUTHOR]

Cobia is an important cultured marine fish species in southern China. It is characterised by fast growth. Due to the effects of climate change on water oxygen levels and seawater temperatures, understanding the influence of environmental challenges on cobia culture has become very important. In this study, to explore the stress and adaptability of cobia (Rachycentron canadum) during hypoxia-reoxygenation conditions, the fish were exposed to an oxygen-deficient environment with dissolved oxygen (DO) level of 2.64 ± 0.25 mg/L. Liver tissue transcriptome sequencing was detected in the fish at acute hypoxia stress, after which fish were returned to normal DO levels (6.34 mg/L) for 8, 24, and 48 h. Comparative analysis of liver transcriptomes revealed that there were 1689, 651, 236, and 1150 differential genes in the hypoxia stress group (SC), reoxygenation-8h group (R8), reoxygenation-24h group (R24), and reoxygenation-48h group (R48), respectively. The differentially expressed genes were compared with the GO database. The main aggregated genes were related to gene ontology functional elements such as ribosome structural components, matrix-dependent cell migration, hormone activity, and oxidoreductase activity. The differentially expressed genes were compared with the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, and a total of 43,054 differentially expressed genes were found to be enriched in 212 cases. For the first time, gene expression patterns in the liver of a juvenile's cobia were examined in response to hypoxia. The results of this study contribute to further clarifying hypoxia's effects on the liver of marine fish. [ABSTRACT FROM AUTHOR]

Romanian flora includes a high diversity of orchids, any with a high conservationist interest, but many 0f themnot yet sufficiently investigated from an ecological, phytosociological or genetic point of view. Phenotypically analysis is also scarce and only a few data have been published in relation to the effects of site factors on the morphological and anatomical characteristics of the family Orchidaceae. This study analyses the variability of two populations of Anacamptis coriophora, based on their coenological affiliations, morphological observations and biometrical measurements. The data were collected from two grassland areas in Romania Stoenesti, Vâlcea County and Cobia, Dâmbovița County. The results showed that both populations are influenced by temperature, light and humidity and develop normally under optimal conditions. In the most favorable conditions encountered in Vâlcea county, orchids offer the splendor of flowers for a long time. Orchids in our country usually bloom in March, sometimes lasting until August, they have a delicate appearance, varied colors and the most diverse perfumes. The information obtained regarding the morphological diversity of the two populations could be suitable for designing strategies for their conservation in both locations. [ABSTRACT FROM AUTHOR]

In mariculture, often the locations of fish hatcheries and farming are distantly situated, and hence, there is a need to transport the seeds/seedlings to a longer distance with maximum survival rate. In the present study, length and weight of fingerlings, duration of starvation, packing density, water volume, water temperature and oxygen level in the packing bags were standardized to ensure maximum survival during transportation. The cobia fingerlings with mean length and weight of 48±12 mm and 3.0±1.0 g, respectively were transported for a duration 48 h at 25 °C with 100 % survival at a packing density of 2.5 fingerlings per litre (L) (7.5±2.5 g/L). Similarly, silver pompano fingerlings with mean length and weight of 24±0.48 mm and 0.6±0.08 g, respectively were transported for a duration of 48 h at 25 °C with 100 % survival at a packing density of 18.75 fingerlings/L (11.25±1.9 g/L). Experiments on bulk transportation of pompano fingerlings in 1000 litres capacity HDPE tanks containing 600 litres of seawater with continuous aeration using oxygen cylinders fitted in a transportation vessel revealed that the silver pompano fingerlings can be transported for a duration of 48 h at 25 °C and 5 - 6 ppm dissolved oxygen concentration with 100 % survival at a packing density of 8.3 fingerlings/L (4.98±0.8 g/L). [ABSTRACT FROM AUTHOR]

Salinity plays a vital role in fish aquaculture, profoundly influencing the growth and development of fish. Scales, as the protective outer layer of fish, function as a critical defense against external factors. In this study, we employed transcriptome sequencing to analyze the ceRNA expression profiles to reveal the effect of salinity acclimation on transcriptional expression changes in the scales of cobia (Rachycentron canadum). The results revealed that after being exposed to a salinity level of 15 ‰ for just one day (1D), a total of 407 mRNAs/genes were significantly regulated; 66 miRNAs were respectively significantly regulated; and 109 target genes of the differentially expressed miRNAs were significantly regulated; a total of 185 differently expressed lncRNAs and 292 differently expressed target genes (DetGenes) of differently expressed lncRNAs were also identified. After 7 days (7D), a total of 2195 mRNAs/genes were found to be significantly regulated and 82 miRNAs were significantly regulated; among the target genes of the differentially expressed miRNAs, 245 were regulated. Moreover, 438 differently expressed lncRNAs and 681 DetGenes of these lncRNAs were identified. Subsequent analysis through GO, KEGG pathway, in 1D vs. CG (control group), DeGenes, which first respond to changes in salinity, are mainly involved in negative regulation of macrophage differentiation, negative regulation of granulocyte differentiation and negative regulation of phagocytosis, and are mainly related to biological processes related to the immune function of fish. After a 7-day process, DeGenes were enriched in the collagen fibril organization, regulation of nodal signaling pathway and cell recognition biology processes. These biological processes are not only related to the immune function of fish, but more importantly, to the physiological structure of fish. By analyzing the co down-regulated miRNAs of 1D vs. CG, as well as 7D vs. CG, the functions of these miRNAs are mainly related to bone differentiation and development. In addition，ceRNA network uncovered that the effect of salinity is temporal. The first competing lncRNAs mainly regulated genes related to physiological processes and biological development, while target genes related to immunity and body defense were less competitive. On the contrary, after a period of salinity treatment, the types of competing lncRNAs involved changed. [Display omitted] • Effect of hypoosmotic treatment on cobia scales was investigated using transcriptomic analysis. • The DeGenes were enriched in immune-related functions/pathways following a one-day hypoosmotic treatment. • Seven-day hypoosmotic exposure resulted in changes in bone metabolism. • The ceRNA network revealed an inverse correlation between competing lncRNAs and mRNAs. [ABSTRACT FROM AUTHOR]

Background: Cobia (Rachycentron canadum) is a species of fish with high commercial potential particularly due to fast growth rates. The evidence of sexual size dimorphism favoring females indicate potential benefits in having a monosex culture. However, the involvement of genetic factors responsible for sexual development and gonadal maintenance that produces phenotypic sex in cobia is largely unknown.Methods: In the present study, we performed transcriptome sequencing of cobia to identify sex-biased significantly differentially expressed genes (DEGs) in testes and ovaries. The reliability of the gonad transcriptome data was validated by qPCR analysis of eight selected significantly differential expressed sex-related candidate genes.Results: This comparative gonad transcriptomic analysis revealed that 7,120 and 4,628 DEGs are up-regulated in testes or ovaries, respectively. Further functional annotation analyses identified 76 important candidate genes involved in sex determination cascades or sex differentiation, including 42 known testis-biased DEGs (dmrt1, amh and sox9 etc.), and 34 known ovary-biased DEGs (foxl2, sox3 and cyp19a etc.). Moreover, eleven significantly enriched pathways functionally related to sex determination and sex differentiation were identified, including Wnt signaling pathway, oocyte meiosis, the TGF-beta signaling pathway and MAPK signaling pathway.Conclusion: This work represents the first comparative gonad transcriptome study in cobia. The putative sex-associated DEGs and pathways provide an important molecular basis for further investigation of cobia’s sex determination, gonadal development as well as potential control breeding of monosex female populations for a possible aquaculture setting.

Cobia (Rachycentron canadum, Rachycentridae) is one of the prospective species for mariculture. The transcriptome-based study on cobia was hampered by an inadequate reference genome and a lack of full-length cDNAs. We used a long-read based sequencing technology (PacBio Sequel II Iso-Seq3 SMRT) to obtain complete transcriptome sequences from larvae, juveniles, and various tissues of adult cobia, and a single SMRTcell generated 99 gigabytes of data and 51,205,946,694 bases. A total of 8609435, 7441673 and 9140164 subreads were generated from the larval, juvenile, and adult sample pools, with mean sub-read lengths of 2109.9, 1988.2 and 1996.2 bp, respectively. All samples were combined to increase transcript recovery and clustered into 35661 high-quality reads. This is the first report on a full-length transcriptome from R. canadum. Our results illustrate a significant increase in the identified amount of cobia LncRNAs and alternatively spliced transcripts, which will help improve genome annotation. Furthermore, this information will be beneficial for nutrigenomics and functional studies on cobia and other commercially important mariculture species. Measurement(s) Full length transcriptome of Cobia (Rachycentron canadum) Technology Type(s) PacBio Sequel 2 Sample Characteristic - Organism Rachycentron canadum Sample Characteristic - Environment Marine environment Sample Characteristic - Location India [ABSTRACT FROM AUTHOR]

Some yeast strains have been proposed as probiotics to improve the health of cultured fish. Cobia is a tropical benthopelagic fish species with potential for marine aquaculture; however, one of the main limitations to its large-scale production is the high mortality of fish larvae. In this study, we evaluated the probiotic potential of autochthonous yeasts from the intestines of cobia. Thirty-nine yeast isolates were recovered from the intestinal mucosa of 37 adult healthy cobia by culture methods. Yeasts were identified by sequencing of the ITS and D1/D2 regions of the 28S rRNA gene and typed by RAPD-PCR using the M13 primer. Yeast strains with unique RAPD patterns were characterized in terms of their cell biomass production ability; anti-Vibrio, enzymatic, and hemolytic activity; biofilm production; hydrophobicity; autoaggregation; polyamine production; safety; and protection of cobia larvae against saline stress. Candida haemuloni C27 and Debaryomyces hansenii C10 and C28 were selected as potential probiotics. They did not affect the survival of larvae and showed biomass production >1 g L−1, hydrophobicity >41.47%, hemolytic activity γ, and activity in more than 8 hydrolytic enzymes. The results suggest that the selected yeast strains could be considered as potential probiotic candidates and should be evaluated in cobia larvae. [ABSTRACT FROM AUTHOR]

Optimal concentrations of three anesthetics for use with juvenile cobia (Rachycentron canadum) were determined using time-to-recovery and hematological datasets. Buffered MS-222, clove oil and 2-phenoxyethanol (2-PE) were examined. Juvenile cobia were exposed to three concentrations of each anesthetic at 24 °C. Based on time to recovery, optimal doses for MS-222 was determined as 120-mg L−1, that for 2-PE, 0.4-mL L−1 and, for clove oil, 5-mL L−1. The hematological response of cobia to anesthesia included quantification of whole blood pH, pCO2, pO2, and Ca2+, K+, Na+, Cl−, hematocrit and glucose. Irrespective of anesthetic employed, cobia expressed metabolic acidosis, with changes in blood pH (p < 0.001) being matched by increases (p < 0.001) in pCO2. Anesthesia tended to increase blood Na+, hematocrit, pO2, Ca2+, and K+ although differential responses between anesthetics were recorded, suggesting different modes of action. A combination of recovery and hematological data indicated that when anesthesia is necessary, MS-222 represents the sedative of choice. [ABSTRACT FROM AUTHOR]

Aquacultural foods represent a valuable source of nutrition with high nutritional value and numerous health benefits. They are widely consumed as a palatable and easily digestible source of protein. However, they are highly susceptible to spoilage after harvesting and subsequent processing and storage. Natural and green biological methods for inhibiting or reducing the growth of microorganisms and controlling the quality of products during storage are of particular commercial importance. In this study, black king fish (BKF) fillets treated with calcined oyster shell powder (COSP) exhibited the dual benefits of extended shelf life and natural safety and nontoxicity. In particular, COSP inhibited acid‐producing microorganisms and aerobic bacteria by regulating pH throughout the refrigerated storage of BFK fillets. TVB‐N levels in BFK fillets were maintained below 20 mg/100 g, while peroxide values (PV), thiobarbituric acid reactive substances (TBARS), and trimethylamine (TMA) levels were all within acceptable ranges, all of which were significantly different (p < 0.05) compared to the control group. In addition, the hardness and overall acceptability performance showed significantly favorable results compared to the control group. The results of this study may be widely applicable to aquatic food products. Minimizing postharvest and financial losses in large‐scale aquatic products production by extending shelf life will provide additional economic benefits. Novelty impact statement: COSP treatment can inhibit the growth of microorganisms.COSP treatment can control the quality of products during frozen storage.Fish fillets treated with COSP exhibited the benefits extended shelf life and natural safety and nontoxicity. [ABSTRACT FROM AUTHOR]

Since 1995, the Virginia Game Fish Tagging Program (VGFTP) has collected data for recreationally important marine fishes in cooperation with skilled volunteers. These trained anglers tagged more than 380,000 fishes since 1995 and contributed data regarding fish movement and site fidelity patterns of species captured and released in the Chesapeake Bay and Atlantic coastal waters. Over time, the VGFTP has become an important source of data for fishery managers and program data are included in stock assessments for species such as Cobia Rachycentron canadum. Best management practices from the VGFTP show that cooperative science programs that collect data for management should have mandatory hands‐on training with quality control mechanisms in place for submitted data. Further, fishery managers, statisticians, and stakeholders should work together to identify the data needs for statistical viability before volunteers start collecting information. Finally, data objectives and project results should be shared with the stakeholders who collected the data, in addition to fishery managers. [ABSTRACT FROM AUTHOR]

The fish immune system is a topic or subject that offers a unique understanding of defensive system evolution in vertebrate heredity. While gut microbiota plays several roles in fish: well-being, promoting health and growth, resistance to bacterial invasion, regulation of energy absorption, and lipid metabolism. However, studies on fish gut microbiota face practical challenges due to the large number of fish varieties, fluctuating environmental conditions, and differences in feeding habits. This study was carried out to evaluate the impacts of supplemented three autochthonous strains, Bacillus sp. RCS1, Pantoeaagglomerans RCS2, and Bacilluscereus RCS3 mixture diet on cobia fish (Rachycentroncanadum). Also, chromatography, mass spectrometry and high throughput sequencing were combined to explore composition and metabolite profile of gut microbiota in juvenile cobia fed with supplemented diet. In the trial group, juvenile cobia received diets supplemented with 1 × 1012 CFU mL−1 autochthonous strains for ten weeks and a control diet without supplementation. Juvenile cobia receiving diets supplementation exhibited significantly improved growth than those without additives (control). Haematological indices, such as red blood cells, white blood cells, corpuscular haemoglobin concentration, mean corpuscular volume, haemoglobin, and mean corpuscular haemoglobin, were higher in the supplemented group. Similarly, digestive enzymes (trypsin, lipase, amylase, pepsin and cellulose, activities) activities were higher in supplemented diet with an indigenous isolates mixture. Serum biochemical parameters albumin, globulin, and total protein were significantly higher, while triglyceride, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and cholesterol showed no significant difference. On the other hand, glucose was significantly (P < 0.05) higher in the group without supplementation. On gene expression in the midgut, Immunoglobulin, Colony-stimulating factor receptor 1, major histocompatibility complex 1 were up-regulated by native isolates while T cell receptor beta, and Major histocompatibility complex 2 showed no significant difference. Gut bacterial composition was altered in fish receiving supplemented diet with autochthonous strains. Metabolomics also revealed that some metabolic pathways were considerably enriched in fish fed with supplemented diet; pathway analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment revealed that differentially expressed metabolites were involved in galactose metabolism, tryptophan metabolism, carbohydrate digestion and absorption, purine metabolism, and ABC transporters. Functional analysis of bacterial community showed that differences in enriched metabolic pathways generally comprised carbohydrate and its metabolites, nucleotide and its metabolites, amino acid and its metabolites, heterocyclic compounds, and tryptamines, cholines, pigments. The current investigation results showed that autochthonous strains mixture has significantly enhanced the growth, survival, and innate and adaptive immunities of juvenile cobia. [ABSTRACT FROM AUTHOR]

Stated and revealed preferences for fish and attributes of fish products important to consumers and prospective aquaculture development in the United Arab Emirates (UAE) were evaluated by consumer surveys, focus groups, key informant interviews, and sensory evaluation (taste, texture and overall liking). Consumers of seafood in the UAE prefer hamour (Epinephelus coiodes) and kanaad (Scomberomorus commerson) above all other species commonly offered at UAE retail outlets. These preferences, which guide consumer-appropriate aquaculture in the UAE, were similar among nationalities (Emiratis and other nationalities), purchasers of fish at seafood retailers, and consumers of fish at restaurants throughout the UAE. Fresh whole fish are preferred over fillets or frozen product because consumers can assess freshness and they consider whole fish to be better value for money. Among other product attributes shown to be important elsewhere, country of origin, wild vs cultured fish, and eco-labels were considered relatively unimportant by UAE respondents. Five prospective species for aquaculture were evaluated through sensory evaluation. Differing from stated preferences, barramundi (Lates calcarifer) (also marketed as Asian seabass) was clearly preferred as having superior taste, texture, and overall liking (over hamour; shaeri, Lethrinus nebulosus ; safi, Siganus canaliculatus ; and cobia, Rachycentron canadum). Of the candidate species, only hamour is successfully grown in the UAE albeit on a relatively small scale (< 1000 t annually). Prospects for increasing aquaculture production of fish in the UAE will most likely depend on recirculating aquaculture systems (RAS) effectiveness as the harsh environmental conditions prohibit other grow out systems (e.g. pond culture). • Consumer preference in the UAE guides aquaculture development. • Sensory analyses favoured Lates calcarifer over other candidate (high-value) species. • RAS offer prospects for high value niche seafood production in the UAE. [ABSTRACT FROM AUTHOR]

The bacterial community of the intestinal microbiota influences many host functions, and similar effects have been recently reported for the fungal community (mycobiota). Cobia is a tropical fish that has been studied for its potential in marine aquaculture. However, the study of its bacterial community has been underreported and the mycobiota has not been investigated. We analyzed the gut bacterial and fungal profile present in the intestinal mucosa of reared adult cobias fed two diets (frozen fish pieces (FFPs) and formulated feed (FF)) for 4 months by sequencing the 16S rRNA (V3-V4) and internal transcribed spacer-2 (ITS2) regions using Illumina NovaSeq 6000. No significant differences in the alpha diversity of the bacterial community were observed, which was dominated by the phyla Proteobacteria (~96%) and Firmicutes (~1%). Cobia fed FF showed higher abundance of 10 genera, mainly UCG-002 (Family Oscillospiraceae) and Faecalibacterium, compared to cobia fed FFPs, which showed higher abundance of 7 genera, mainly Methylobacterium-Methylorubrum and Cutibacterium. The inferred bacterial functions were related to metabolism, environmental information processing and cellular processes; and no differences were found between diets. In mycobiota, no differences were observed in the diversity and composition of cobia fed the two diets. The mycobiota was dominated by the phyla Ascomycota (~88%) and Basidiomycota (~11%). This is the first study to describe the gut bacterial and fungal communities in cobia reared under captive conditions and fed on different diets and to identify the genus Ascobulus as a new member of the core fish mycobiota.

Onshore farming for premium aquaculture is under scrutiny and criticism partially due to possible causes of adverse environmental impacts on other resource users and the surrounding environment. The best alternative to preventing or minimizing these impacts is to utilize open seawater by large submersible cage culture. The current operation in Taiwan has demonstrated that the culture operation is technically feasible but economically demanding because of high capital and operating costs. Therefore, this study conducted an economic analysis of the expansion of large submersible cage culture by selecting two premium species of snubnose pompano (Trachinotus anak) and cobia (Rachycentron canadum) and examined the profitability of large submersible cage culture investment. This study found that the current operation of four-unit cages highlighted a negative net present value and internal rate of return with a payback period of over ten and six years, respectively. Large submersible cage culture can be financially profitable when its operation unit expands from 8 to 24 units. Increasing unit cages to eight incurred a gross margin of 17.09%, BCR 1.21, with a payback period of 5.36 years. Expanding the operation to 24-unit cages was a potentially lucrative investment with a gross margin of 18.51%, BCR 1.23, PI 2.15, internal rate of return of 20.84%, and a payback period of 3.55 years. Sensitivity analyses revealed that market price and survival rate significantly impact the profitability of large submersible cage culture. Finally, it is suggested that producers could invest in 8-unit cages and maintaining the survival rate of snubnose pompano and cobia at 80% and 40%, respectively. [ABSTRACT FROM AUTHOR]

The aim was to evaluate the sensory quality by electronic nose (EN) and tongue (ET) of bread added by cobia minced protein in differents times of storage. Two samples were elaborated: (a) control (FF—traditional bread); (b) added by 10% Cobia minced protein (FPN). The two samples of bread were analyzed from time "zero" (1 hr after being baked) to time "five" (120 hr). A Portable EN (PEN2) composed of 10 sensors was used. Operating conditions: flow rate 300 ml/min, injection time 60 min, flush time 180 min. To ET (Taste‐Sensing System SA402B) 5 sensors were used. All samples were analyzed twice and the average was analyzed by Principal Component Analysis, showing the relationship among the samples and the variables. The greatest differences between the odors were observed after 120 hr of storage. In the first 48 h, the EN was unable to differentiate the samples. The biggest differences of taste were observed at t0. In the other evaluation times, the samples reduced their differences. The use of electronic sensory methods showed promising. Confer greater specificity in the determination of odors and taste of products. Therefore, these tools can be used to improve the sensory characteristics of the new products, as enriched foods. Practical Applications: Bread is a basic food of the world population, but it does not present a big quantity/quality protein content. Using fish protein concentrate in bread improves the nutritional quality of this product, however, in function of the physico‐chemical composition, fish and derivates may present a strong characteristic odor/taste, rejected by a large part of the population. The sensory characteristics of a product are determining factors for the choice and purchase by the consumers. Maintaining a permanent panel of trained evaluators takes high time and continuous costs, and is not entirely accurate. The use of technologies used by the electronic nose and tongue can assist in a greater standardization of food, especially when it involves the development of new products, ingredients, or differentiated raw ingredients, as made in this study. [ABSTRACT FROM AUTHOR]

In intensive aquaculture systems, dissolved oxygen (DO) is the most critical and limiting factor for the development and health of aquatic organisms. Hypoxia is a common phenomenon in aquaculture. Its effects on fish’s growth and immune system have been widely reported, but the molecular mechanisms of hypoxic stress on damage to the fish gut are not fully understood. Additionally, studies on the effects of hypoxic stress on the intestinal metabolism of cobia (Rachycentron canadum) are still limited. Therefore, this study used cobia to explore the effects of hypoxic stress on intestinal metabolism. In this study, the combination of high-throughput RNA sequencing (RNA-Seq) and non-targeted liquid chromatography-mass spectrometry (LC-MS) based metabolomics analyses were used to investigate changes in key genes and metabolites in the intestinal tract of juvenile cobia after 28 days of hypoxic stress (DO: 3.15 ± 0.21 mg/L). Transcriptomics analysis revealed the significant enrichment of 62 metabolic pathways, including glutathione metabolism, fat digestion and absorption, bile secretion, glycerolipid metabolism, tricarboxylic acid cycle, glycolysis/gluconeogenesis, and other pathways. Metabolomics analysis revealed that most of the significantly differential metabolites were related to the metabolism of amino acids and lipids. The combined transcriptomics and metabolomics analyses showed that the sustained hypoxic stress could cause some degree of oxidative damage to the gut of cobia, thereby interfering with its digestive absorption and physiological and metabolic processes, such as abnormalities in antioxidant and detoxification functions, disturbances in the metabolisms of amino acids, lipids, and carbohydrates, and reduction of ion transport capacity. These findings might help understand the molecular mechanisms of the intestinal tract under hypoxic stress in cobia, thereby reducing the damage caused by hypoxic stress to farmed fish.

Carnivorous fish, such as cobia Rachycentron canadum, tend not to have a specific requirement for dietary carbohydrates (CBH). However, if CBH is not provided in the diet, other energy-yielding nutrients, such as protein and lipids, are catabolized to produce energy. Therefore, knowing the optimum level of dietary CBH would be useful for cobia aquaculture. In the present study, four isonitrogenous and isolipidic diets were prepared to investigate the effects of dietary CBH level (4.8–22.5 %) on growth performance and body composition of, and feed utilization, by juvenile cobia (initially weighing 22.2 ± 0.27 g/fish). Each diet was given to triplicate groups of cobia for 8 weeks. Both the final body weight and specific growth rate increased with increasing dietary CBH levels. Feed intake decreased with increasing dietary CBH levels (P 0.05). Activities of hepatic glucokinase increased with increasing dietary CBH levels, being significantly higher in fish fed a 22.5 % CBH diet compared with other groups (P

Applications of microbiome research through metagenomics promise to generate microbiome manipulation strategies for improved larval survival in aquaculture. However, existing lacunae on the effects of sample preservation methods in metagenome profiles hinder the successful application of this technique. In this context, four preservation methods were scrutinized to identify reliable methods for fish larval microbiome research. The results showed that a total of ten metagenomics metrics, including DNA yield, taxonomic and functional microbiome profiles, and diversity measures, were significantly (P < 0.05) influenced by the preservation method. Activity ranking based on the performance and reproducibility showed that three methods, namely immediate direct freezing, room temperature preservation in absolute ethanol, and preservation at − 20 °C in lysis, storage, and transportation buffer, could be recommended for larval microbiome research. Furthermore, as there was an apparent deviation of the microbiome profiles of ethanol preserved samples at room temperature, the other methods are preferred. Detailed analysis showed that this deviation was due to the bias towards Vibrionales and Rhodobacterales. The microbial taxa responsible for the dissimilarity across different methods were identified. Altogether, the paper sheds light on the preservation protocols of fish larval microbiome research for the first time. The results can help in cross-comparison of future and past larval microbiome studies. Furthermore, this is the first report on the activity ranking of preservation methods based on metagenomics metrics. Apart from methodological perspectives, the paper provides for the first time certain insights into larval microbial profiles of Rachycentron canadum, a potential marine aquaculture species. Key points: • First report on effects of preservation methods on fish larval microbiome profiles. • First report on activity ranking of preservation methods based on metagenomics metrics. • Storage methods influenced DNA yield, taxonomic and functional microbiome profiles. [ABSTRACT FROM AUTHOR]

Cobias (Rachycentron canadum) are large fish that live in all the tropical oceans of the world, except for the Eastern Pacific Ocean (EPO). During 2015, a cobia cage culture was initiated in the EPO off Ecuador. Thousands of cobia individuals escaped from the culture, and the location of the escapees is unknown. In this paper, we used a Maximum Entropy (MaxEnt) model to assess the preferential habitat of cobia in a portion of its natural occurrence range and used the model to predict the potential invasion zones of cobia in the EPO. The model performance was satisfactory (75–93% accuracy). Mixed Layer Depth (MLD) was the most important environmental variable. Cobia inhabits waters near the continental shelf, with a shallow MLD. Five important zones of high probability of invasion were detected in the EPO: one in the southern California Current, one in the Central Mexican Pacific, one off Guatemala/El Salvador, one in a latitudinal band that detaches from the coastline of Central America, and one off Northern Chile. There is an important seasonal variation of the zones of high probability of cobia invasion, variation that is apparently related to the seasonal cycle of different large-scale and mesoscale systems. [ABSTRACT FROM AUTHOR]

The diseased cage-cultured cobia (Rachycentron canadum) displayed clinical signs, haemorrhagic eyes, dorsal darkness and gross pathological lesions, enlargement of spleen and liver. Haemorrhages were found in brain, heart and liver with cumulative mortality rates ranging from 20% to 50%. Extensive congestion in the heart, liver, spleen, kidney and brain was observed histopathologically. Epicarditis and meningitis were also revealed in diseased cobia. All isolates recovered from the organs (liver, spleen, head kidney, posterior kidney, brain and muscle) of cobia were found to be gram-positive, non-motile, ovoid cocci, short-chain-forming (diplococci) and a-haemolytic. The API 32 strep system together with the polymerase chain reaction assay for species-specific primers (pLG1 and pLG2) and the internal transcribed spacer (ITS) region (G1 and L1 primers) confirmed all four selected isolates as Lactococcus garvieae. Partial 16S rDNA nucleotide sequence (~1,100 bp) of one representative L. garvieae isolate AOD109191 (GenBank accession number, MW328528.1) shared 99.9% identities with the 16S rDNA nucleotide sequence of L. garvieae (GenBank accession numbers: MT604790.1). Transmission electron microscopy (TEM) evaluation of one representative L. garvieae isolate (AOD109191) and the results of multiplex PCR did not reveal the presence of the capsular gene cluster (CGC), thus categorizing the isolate as the KG+ phenotype. Capsule staining and TEM observations confirmed the presence of a hyaluronic acid-like capsule, a possible virulence factor in KG+ phenotype L. garvieae isolates. The pathogenic potential of the representative isolate (AOD109191) was assessed through intraperitoneal injection challenges in cobia. The gross lesions and histopathological changes found in experimentally infected cobia were similar to those seen in naturally infected fish. This is the first report that confirms L. garvieae-induced 'warm water lactococcsis' can cause outbreaks of diseases in cage-cultured cobia. [ABSTRACT FROM AUTHOR]

The present study investigates the response of the marine fish cobia, Rachycentron canadum, to stressors as measured by phosphorylation of the α-subunit of the translational initiation factor, eIF2. eIF2α is the target of phosphorylation by a family of kinases that respond to a range of physiological stressors. Phosphorylation of eIF2α inhibits overall protein synthesis, but also facilitates the reprogramming of gene expression to adapt to, and recover from, stress. The deduced coding sequence of cobia eIF2α has 94% identity to both zebrafish (Danio rerio) and human eIF2α sequences with identical phosphorylation and kinase docking sites. Here we use cobia larvae and a cobia cell line derived from muscle (Cm cells) to investigate the response of cobia eIF2α to various stressors. In Cm cells, phosphorylation of eIF2α is increased by nutrient deficiency and endoplasmic reticulum stress (ER stress), consistent with the activation of the eIF2 kinases, GCN2, and PERK. In cobia juveniles, diet and water temperature affect the phosphorylation state of eIF2α. We conclude that evaluation of eIF2α phosphorylation could function as an early marker to evaluate diet, environmental stressors, and disease in cobia and may be of particular use in optimizing conditions for rearing cobia larvae and juveniles. [ABSTRACT FROM AUTHOR]

The vasa gene is essential for germ cell development and gametogenesis both in vertebrates and in invertebrates. In the present study, vasa (Rcvasa) cDNA was cloned from cobia (Rachycentron canadum) using the RACE amplification method. We found that the full-length cDNA sequence of Rcvasa comprises 2571 bp, containing a 5′-UTR of 145 bp, a 3′-UTR of 341 bp, and an open reading frame (ORF) of 2085 bp, encoding a protein of 694 aa. The deduced amino acid sequence contains 8 conserved motifs of the DEAD-box protein family, 7 RGG repeats, and 10 RG repeats in the N-terminal region. Comparisons of the deduced amino acid sequence with those of other teleosts revealed the highest percentage identity (86.0%) with Seriola quinqueradiata. By using semiquantitative RT-PCR, Rcvasa appeared to be specifically expressed in the testis and ovary, among 13 tissues analyzed. In addition, annual changes in Rcvasa expression levels were examined in the gonads by quantitative real-time PCR (qRT-PCR). The expression of Rcvasa in the testis first increased significantly at 120 dph (stage II–III), then stabilized as the testis developed from 185 dph (stage III) to 360 dph (stage V). During the development of the ovary (stage I to II), the expression of Rcvasa first increased and reached the highest level at 210 dph (stage II), then decreased. Furthermore, the results of chromogenic in situ hybridization (CISH) revealed that Rcvasa mRNA was mainly expressed in germ cells and barely detected in somatic cells. In the testis, Rcvasa mRNA signal was concentrated in the periphery of spermatogonia, primary spermatocytes, and secondary spermatocytes and was significantly weaker in spermatids and spermatozoa. In the ovary, Rcvasa mRNA signal was uniformly distributed in the perinuclear cytoplasm and was intense in early primary oocytes (stage I and II). These findings could provide a reference for understanding the regulatory mechanisms of vasa expression during the development of germ cells in cobia. [ABSTRACT FROM AUTHOR]

Hypoxia is a lack of required oxygen to meet the metabolic demands of living organisms. Cellular hypoxia occurs when the molecular oxygen, essential to maintain sufficient adenosine triphosphate (ATP) levels for normal physiological function, surpasses the vascular supply. Tissue hypoxia can arise during a range of diseases. As molecular oxygen is a crucial metabolic energy source for all living organisms, animals manage the intracellular oxygen levels to sustain homeostasis, with the upregulation of genes that improve tissue perfusion and anaerobic ATP creation via glycolysis. This is facilitated by the hypoxia-inducible factors (HIFs). Hypoxia-inducible factor 1α (hif-1a) is the core regulator of the hypoxia response and plays a crucial role in the cellular/molecular response to hypoxic stress by regulating the transcription of target genes. In the present study, hif-1a cDNA was identified and cloned from cobia (Rachycentron canadum), using rapid amplification of cDNA ends (RACE). The hif-1a and downstream mRNA expression levels in various tissues were then determined. The full length of hif-1a cDNA is 3642 bp, with a 2292 bp open reading frame (ORF), a 5′ non-coding region (5′-UTR) of 293 bp, 3′ non-coding region (3′-UTR) of 1057 bp, and encoding 764 amino acids. The encoded protein contains the basic helix-loop-helix domain (amino acid 22–77), PER-Arnt-SIM domain (amino acid 88–154 and 230–296), and the PAS-associated C-terminal domain (amino acid 302–345). hif-1a mRNA expression was detected in nine tissues, with the highest expression observed in the liver, and the lowest expression in the intestine and spleen. hif-1a, erythropoietin (epo), and vascular endothelial growth factor (vegf) gene expressions were analyzed in the gill, intestine, liver, and muscle under hypoxic stress. In the gills, hif-1a expression was significantly increased at all hypoxia time points as well as in the liver. Erythropoietin (epo) and vascular endothelial growth factor (vegf) showed similar trends, with a significant decrease followed by a significant increase. In the muscle, the expression of all three genes was higher than the control group after hypoxic stress. These results indicate that the expression patterns of hif-1a and related genes after hypoxic stress are tissue-specific and play an essential role in cobia's response to hypoxia. [ABSTRACT FROM AUTHOR]