Cobia Research Articles

Optimizing the Use of Flexible Retort Pouches for Production of Ready to Eat Cobia (Rachycentron canadum) Fish Chunks in Curry Medium

Cobia fish chunks in curry medium, a famous North Eastern Indian dish, was developed using Cobia (Rachycentron canadum) fish chunks prepared in a traditional culinary style. The present study was aimed to optimize F0 values for Cobia fish chunks in curry medium using flexible retortable pouches. The product underwent thermal processing at two distinct lethality levels and heat penetration rates, demonstrating equivalent cooling and heating lag effects. The fh values were 15 and 18.5 minutes for the product processed at F0 values of 9.29 and 8.42 minutes, respectively. The total process times were 39.79 and 38.80 minutes, respectively, for the F0 values of 8.42 and 9.29 minutes. Cook values for the processed product were 86.60 minutes for the F0 value of 8.42 minutes and 92.57 minutes for the F0 value of 9.29 minutes. Based on sensory characteristics, the product processed at an F0 value of 8.42 minutes was rated better over a storage period of 90 days.

Discovery of two new species of cobia (Pisces; Rachycentridae) inhabiting the makran coast of the northern Arabian Sea with notes on their biology and ecology

Cobia, Rachycentron canadum has long been regarded as the sole species in the family Rachycentridae, and has a wide distribution in tropical and sub-tropical regions of the Atlantic, Indian Ocean and western Pacific. This study describes two newly identified species, Rachycentron blochii sp. nov. and Rachycentron makranesis sp. nov. from Gwadar in the northern Arabian Sea. The newly discovered species differ significantly from their relatives in multiple morphological traits, such as head profile, mouth, pectoral fin, caudal fin, caudal peduncle, dorsal and anal fin bases, gill rakers, and body coloration. Additionally, species delimitation was further supported by examining body scales and otoliths (sagitta, lapillus, and asteriscus), with shapes also delimiting species. The recent finding increases the number of cobia species in the northern Arabian Sea, Pakistan. Moreover, details on the biological and ecological aspects such as feeding habits, age assessment, habitat preferences and fishery-related details are presented.

Global research performance trends and knowledge gaps on cobia (Rachycentron canadum): a scientometric perspective

Global research performance trends and knowledge gaps on cobia (Rachycentron canadum): a scientometric perspective

Francisella salimarina infection in farmed cobia (Rachycentron canadum) and dusky grouper (Epinephelus marginatus) in Brazil: A case report.

This study aimed to identify and characterize isolates of Francisella salimarina associated with an outbreak on a marine fish farm in Brazil and to analyse their genetic variability and antimicrobial susceptibility. In 2021, diseased cobias (Rachycentron canadum, n = 10) and dusky groupers (Epinephelus marginatus, n = 10) were sampled and subjected to bacteriological and pathological examinations. The isolates obtained were morphologically and biochemically characterized and identified by matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) and 16S rRNA gene sequencing. The genetic diversity of these isolates was analysed using repetitive extragenic palindromic-polymerase chain reaction (REP-PCR). Antimicrobial susceptibility was assessed using the disk diffusion technique. Macroscopically, the fish presented skin ulcerations, ocular lesions, hepatomegaly and splenomegaly. A pleomorphic, gram-negative, catalase- and oxidase-positive bacterium was isolated from seven cobias and two groupers. The 16S rRNA gene sequences showed >99% coverage and identity with other deposited sequences of F. salimarina. The results of the biochemical analysis corresponded to these bacterial species. Histologically, granulomas were observed in the spleen, liver and heart of the cobias (n = 6), and necrotizing and fibrinous dermatitis and myositis were identified in some groupers (n = 2). The isolates exhibited the same banding pattern when REP-PCR was performed, indicating that they were clonally related. Finally, the antibiogram test, no inhibition halo was observed for amoxicillin and trimethoprim-sulfamethoxazole. To our knowledge, this is the first report of F. salimarina infection in cobias and dusky groupers.

Estimating growout production costs of commercial‐scale marine finfish production in southern tier US states

AbstractIncreased 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.

Exploring tradeoffs in southeast United States marine fisheries management using management strategy evaluation

Recreational fishing is the fastest growing sector in industrialized nations and can have substantial impacts on marine fish populations and ecosystems. Commercial objectives are typically characterized by maximizing yield and fishery stability whereas recreational anglers generally prefer sustained access to fishing and the availability of larger fish. Achieving these objectives while balancing tradeoffs between recreational and commercial fishing is essential to effective recreational and mixed-use fisheries management. Balancing multiple sector objectives is of particular concern in the southeast United States (US), where recreational fishing is the dominant source of mortality for marine fish stocks. We developed and applied a size-structured management strategy evaluation (MSE) tool, individually, to two stocks in southeast US Atlantic waters, black sea bass (Centropristis striata), a sedentary reef fish in overfished condition, and cobia (Rachycentron canadum), a migratory coastal pelagic fish, to evaluate the performance and tradeoffs of mixed management procedures against a variety of objectives. Several recreational and commercial objectives were aligned: fishers sought to conserve the stock and maximize catch, which simplified the evaluation of tradeoffs. We tested management procedures over alternate states of recruitment for black sea bass, and natural mortality for cobia. Management procedures that allowed harvest for black sea bass resulted in or risked an overfished status if the current weak recruitment regime continues, but could rebuild with no fishing regardless of recruitment state. Although results were sensitive to uncertainty in recruitment, no management procedures could achieve historic landings for either sector, and only management procedures that reduced effort consistently resulted in a reduced number of dead discards. No management procedures resulted in an overfished status for cobia. Management procedures for cobia generally achieved objectives and were robust to uncertainty in natural mortality. In both case studies, tradeoffs occurred between maximizing catch and season length and maintaining a stronger size structure in the population. This study resulted in a flexible MSE tool with strong potential utility for scoping management procedures that explicitly consider recreational fishing objectives.

Optimization of cobia fish (Rachycentron canadum) gelatin extraction with response surface methodology

Cobia fish or often called sea cork fish, is a fish that has thick meat which is nutritionally equivalent to salmon meat. Cobia fish is usually sold in the form of fish fillets and the bones becomes solid waste, which has the potential to be a raw material for fish gelatin. Gelatin is a bone and skin collagen hydrolysis product that can be used for food and nonfood industries. The quality of fish gelatin is influenced by the extraction process, such as acid concentration, temperature, and extraction time. This study aims to determine the effect of hydrochloric acid concentration, temperature, extraction time, and the optimal process of making cobia fish bone gelatin using the response surface methodology with the Box Behnken model. The data was processed using Design Expert 11 software. The model suggested by the software was the cubic model. The optimum extraction conditions obtained were using a concentration of 5.53% hydrochloric acid, a temperature of 90oC, and a stirring time of 6.42 mins would produce a yield of 12.38% and gel strength of 229.14 bloom. The verification results by extracting cobia fish gelatin with optimum conditions obtained a yield of 11.22% and gel strength of 227.60 bloom. The proximate analysis of cobia fish gelatin extracted under optimum conditions was found to contain 6.43% water content, 8.27% ash content, 4.65% fat content, 68.47% protein content, and 12.18% carbohydrate by different. Cobia fish gelatin microstructure is in the form of thick strands with a soft sponge.

Stock status indicators for Cobia Rachycentron canadum in the Indian EEZ

Regional fisheries for cobia (Rachycentron canadum) along the Indian coast was assessedusing length-based stock status indicators. Drift gill nets-cum-hook and line fisheries landedbigger sized cobia as bycatch while multi-day mid-water trawls landed juveniles. Dominantsize groups in the landings along the west coast were 40–160 cm and 60-120 cm on theeast coast. Gear selectivity operating at regional levels because of the multi-gear fisheriesand fishing grounds of the Indian EEZ affects the size distribution of fish caught. Comparedto drift gill net-cum-hooks and line units targeting large pelagics in deeper waters, smallersize groups of cobia dominated as bycatch in trawls. The length at first capture (Lc50) beingsmaller than the estimated length at first maturity of about 60 cm, implementing size-basedoutput controls such as Minimum Legal Size (MLS) is suggested. The indicators for fishingmortality rates (Fmax) on the cobia stocks were on the higher side in certain locations only,but being part of the multi-species bycatch mix, there is little scope to introduce fishinggear regulations solely for cobia. However, the option of short-term, targeted spatiotemporaleffort regulations with fishers’ participation can be explored, based on the stockassessments made at local or regional levels. Keywords:Cobia, Fishery indicators, Length-based indicators,Minimum Legal Size, Rachycentron canadum, Stockstatus

Enhancement of aquaculture performance of cobia, Rachycentron canadum (Linnaeus 1766): A review

Cobia, Rachycentron canadum, is a marine fish with recognized potential for aquaculture due to its fast growth rate, high fecundity, disease resistance, and quality flesh. However, much progress has been made to overcome problems associated with aspects of cobia production, including broodstock management, fingerling production, larval-rearing, grow-out, and disease management, though, an effort is needed to ensure its sustainability. Broodstock conditioning protocols for continuous spawning as well as induced spawning via hormonal injection resulted in all-year-round seed production in cobia, but detailed information on the cost-effective dosages of various spawning hormones for maximum fecundity and larval survival needs to be investigated. Selective breeding, the application of genetics in trait selection, and the use of molecular markers could produce more viable strains to mitigate high mortality, particularly in colder climates. In addition, considering the fact cobia are carnivorous fish with a high protein requirement, it will be necessary to investigate fishmeal alternatives to reduce feeding costs. Low salinity pond culture may become a reality in the future if the cobia metabolism-physiology of nutrition at various levels of salinity is well understood. The present paper provides information on some of the options for optimizing the aquaculture performance of Rachycentron canadum.

Establishment of a cobia (Rachycentron canadum) gill cell line: A valuable tool for immune response studies

Cobia (Rachycentron canadum), a commercially important marine fish, has been used to develop a novel gill cell line, designated CG, for the first time. The CG cell line was cultured in Leibovitz's-15 medium with 5% fetal bovine serum (FBS) and successfully sub-cultured more than 110 passages. It underwent verification through sequencing of the mitochondrial cytochrome C oxidase subunit I (COI) gene. Optimal growth rate was achieved when the CG cell line was cultured in a medium supplemented with 5% FBS, 1% Penicillin-Streptomycin (P/S), and 5 parts per thousand (ppt) of coral sea salt water, maintained at a temperature of 27 °C. The addition of 5 ppt of salt in the growth medium suggests that this cell line could be a viable in vitro tool for marine ecosystem toxicological studies or for culturing marine parasitic microorganisms. The CG cell line was also successfully transfected using the pTurbo-GFP plasmids, showing an 18% efficiency, with observable GFP expression. Furthermore, the cell line has been effectively cryopreserved. Gene expression analysis indicated that the CG cell line exhibits responsive regulation of immune gene expression when exposured to various stimulants, highlighting its potential as an in vitro platform for immune response studies. This makes it suitable for exploring dynamic immune signaling pathways and host-pathogen interactions, thereby offering valuable insights for therapeutic development.

Mapping the potential spatial distribution for offshore finfish aquaculture in China under climate change

Offshore aquaculture plays an important role in alleviating the pressure of coastal aquaculture and promoting the sustainable development of fisheries. And changes in ocean conditions caused by climate change will have a huge impact on mariculture. Considering the conditions of climate change, this study took the main mariculture fishes in China as the research object, used a species distribution model (SDM) to predict the potential mariculture areas of each fish under the current and different future (2040–2050) climate scenarios, divided the mariculture areas into three potential levels by natural breaks classification method, and calculated the area of different levels potential areas of each fish through the grid number and grid unit area. Additionally, this paper compares the potential area variation of different fishes under different climate scenarios. The results indicate that: (1)In the current climate, the potential area of Yellowtail kingfish(Seriola lalandi) is the largest among seven fishes, estimated at 1,288,500 km2. And the number of varieties suitable for aquaculture in the East China Sea and the South China Sea is more than that in the Bohai and Yellow Seas. (2)Compared with the high potential area of current and future climate scenarios, Large yellow croaker(Larimichthys crocea) has the largest increase, Yellowtail kingfish(Seriola lalandi) decreases under all four future climate scenarios, and both Cobia(Rachycentron canadum) and Allied Kingfish(Seriola dumerili) has small changes. (3)In the future climate scenarios, the number of species potentially suitable for culturing increases significantly in the Bohai and Yellow Sea area, and in the South China Sea, the suitable areas for cultured Large yellow croaker(Larimichthys crocea), gold pompanos(Trachinotus ovatus), Cobia(Rachycentron canadum) and Allied Kingfish(Seriola dumerili) decrease significantly. Overall, the potential areas of each fish show a northward trend.

Dietary Fishmeal Replacement by Methanol-Extracted Cottonseed Meal with Amino Acid Supplementation for Juvenile Cobia Rachycentron canadum

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.

Exploring the cobia (Rachycentron canadum) genome: unveiling putative male heterogametic regions and identification of sex-specific markers.

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. Here, we reported 2 high-quality, chromosome-level annotated male and female cobia genomes with assembly sizes of 586.51 Mb (contig/scaffold N50: 86.0kb/24.3 Mb) and 583.88 Mb (79.9kb/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. 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.

Optimization of packing and transportation of the fingerlings of cobia (Rachycentron Canadum (Linnaeus, 1766)) and silver pompano (Trachinotus blochii (Lacepède, 1801))

Optimization of packing and transportation of the fingerlings of cobia (Rachycentron Canadum (Linnaeus, 1766)) and silver pompano (Trachinotus blochii (Lacepède, 1801))

Studies of Serrasentis sagittifer (Linton, 1889) Van Cleave, 1923 from cobia Rachycentron canadum (Linn.) in the Arabian Gulf; with Molecular Analysis and Optical Microscopy

The finding of a population of Serrasentis sagittifer (Linton, 1889) Van Cleave, 1923 in Cobia Rachycentron canadum (Linn.) in the Arabian Gulf off Iranian waters prompted the study of its molecular parameters known previously only from a population of adults from the same host species, and of immatures from northern Australian waters and from other hosts in the Red Sea. We have previously described S. sagittifer from Cobia and from paratenic hosts in the same Gulf waters off Kuwait and Qatar and detailed its worldwide morphological variability and geographical distribution. We have processed and sampled a few specimens from the Arabian Gulf off Iran for morphological verification of their diagnosis and offered a few light microscopical images that accentuate their identity in Iranian waters for the first time. We document additional diagnostic features of S. sagittifer using optical microscopy. We determine that the distribution of S. sagittifer runs parallel that of its primary adult host, R. canadum, worldwide. We have used the 18S and 28S gene regions of ribosomal RNA, including the mitochondrial cox1 gene, for molecular analysis of an Arabian Gulf population for the first time. Maximum likelihood and Bayesian inference methods were used for phylogenetic reconstructions, the sequences of S. sagittifer from Iran were grouped within the genus Serrasentis and placed as a sister group to S. nadakali George and Nadakal, 1978. Due to the lack of molecular data for other species of this group of Rhadinorhynchidae, the present phylogenetic inferences are required to continue exploring the genetic diversity of this group of species to infer their phylogeny. The cox 1 haplotype network inferred with 14 sequences of S. sagittifer revealed 13 haplotypes separated from each other by a few substitutions. Our ocular microscopy accentuated morphological details of S. Sagittifer and the haplotype network genealogy produced in this study based on mt cox1 sequences from S. sagitiffer show a phylogeographic structure for the first time; therefore, the haplotypes grouped into their own geographic clusters.

Effect of extenders, cryoprotectants and dilution ratios on the spermatological properties of cryopreserved milt of cobia Rachycentron canadum

Cobia (Rachycentron canadum) culture depends on the availability of seeds which isaffected by asynchronous spawning and brooders availability. The possible solution forthese problems is the use of cryopreserved, high quality gametes from selected individuals.Therefore, in the present study, the effect of different extenders, different concentrationsof cryoprotectants and dilution ratios on the spermatological properties of cryopreservedcobia milt was analysed. Milt was collected from R. canadum brooders and diluted withMarine Fish Ringer’s Solution (MFRS) and 0.85% physiological saline (PS) as extendersand dimethyl sulphoxide (DMSO) as cryoprotectant at three different concentrations(5, 10 and 15%) at three dilution ratios such as 1:5, 1:10 and 1:15. Motility duration, motilitypattern, motility score and percentage of live and dead cells were analysed. The milt wasrapidly frozen employing liquid nitrogen vapour for 10 min. The milt sample diluted with PSand 10% DMSO at 1:5 dilution ratio exhibited highest post-thaw motility parameters. Keywords:Cryoprotectants, Cryopreservation, Dilution ratios, Extenders, Spermatological properties, Rachycentron canadum

Deciphering the microbial landscapes in the early life stages of a high-value marine fish, cobia (Rachycentron canadum, Rachycentridae) through high-resolution profiling by PacBio SMRT sequencing

Microbial dynamics across multiple ontogenetic stages represent one confounding feature in teleost microbiome research. The present study recorded the dynamics in the whole microbiome of early life stages and the juvenile gut microbiome of a high-value mariculture species, cobia (Rachycentron canadum), during standard culturing practices. This is the first report on using the PacBio system targeting full-length 16S rRNA sequences, for deciphering fish microbiomes. The results highlighted a temporal shift in the whole microbiome compositions along the host's ontogenetic development. There was a significant decrease in Cyanobacteria and Firmicutes to Bacteroidetes ratio with a corresponding increase in Plactomycetacea and Bacteriodata in the whole microbiome profiles of the post-metamorphosis samples. The gut microbiome data suggested an adaptive mechanism toward establishing beneficial strains (Bacilli and Actinobacteria) alongside the ontogenetic progression. Nevertheless, a small, abundant core bacterial community occupied ∼50% and ∼ 64% of total abundance in the whole microbiome and gut microbiome, respectively. The results revealed high-dimensional microbial biomarkers for various ontogenetic stages of cobia during standard culturing practices. The composite dataset generated offers several possible sustainable means of microbiome manipulations to improve the low survival encountered in the early life stages of cobia.

Evaluation of the green development efficiency of marine fish culture in China

Green development efficiency (GDE) is an important criterion for measuring the level of green development. GDE considers not only economic development efficiency but also environmental costs. In China, marine fish culture, as one of the pillar industries of mariculture, promotes green development and industrial transformation and upgradation. Based on data from the field surveys of marine fish farmers (2017–2019) and the China Fishery Statistical Yearbook (2018–2020), this study establishes an evaluation index system and uses the super-slack-based measure model (Super-SBM) to evaluate the GDE of marine fish culture. The results show that the average GDE of marine fish culture in China was 0.9529, which was in an inefficient state. As for culture species, golden pompano (Trachinotus ovatus) and cobia (Rachycentron canadum) were the two species farmed in an efficient state, with a GDE of 1.2107 and 1.0659, respectively. Regarding culture modes, green modes (offshore cage aquaculture, industrial recirculating aquaculture, and engineering pond aquaculture) were in an efficient state, with a GDE of 1.2310, 1.0827, and 1.0401, respectively. Traditional modes (industrial flow-through aquaculture, ordinary cage aquaculture, and ordinary pond aquaculture) were in an inefficient state, with their GDE being 0.9884, 0.8746, and 0.8248, respectively. Green modes have higher GDE than traditional modes. In contrast, the production and culture areas of green modes were less than those of traditional modes because the profits of the same species in green modes were lower than those in traditional modes. The results of this study present an objective assessment of the GDE of marine fish culture in China and provide valuable insights for analyzing the mechanisms to improve the GDE of marine fish culture.

Contaminated fungi in dried salted fishes: Isolation, identification, and their inhibition by chitooligosaccharide-gallic acid conjugate.

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 0.625-2.5mg/mL and 1.25-10mg/mL, respectively. COS-GAL conjugate at the concentration of 5mg/mL completely inhibited the spore germination of A. versicolor F1/10M9 and P. citrinum F1/23M14 after 72h 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.

Opportunities and challenges for cobia, Rachycentron canadum aquaculture in the United Arab Emirates

Among the many candidate local species identified for development of aquaculture in the United Arab Emirates (UAE), cobia (Rachycentron canadum) has the great potential for farming in floating cage systems. Successful spawning and rearing of larvae and juveniles was first achieved by the Aquaculture and Marine studies Center, Abu Al Abyad Island, Abu Dhabi in 2008. The first trial to grow cobia in near shore cages of 55 m³was done in 2009 when the stocked fish reached an average weight of 2.87 kg in 12 months rearing period. Subsequently two more attempts were carried out in larger 15 meter diameter (636 m³) cages in 2022, the results of which were not encouraging. There are many challenges for the development of cobia farming in UAE. This article highlights the current technological challenges, sustainability issues, marketing strategies and policy matters that confront the development of commercial cobia aquaculture in the UAE and offers some recommendations.