Lysine-specific demethylase 4A (KDM4A) catalyzes demethylation of histone lysine residues, which regulates chromatin state and transcription. In drosophila and mice, KDM4A plays an important role in multiple biological processes including development, aging, metabolism, and immunity, however the functions of KDM4A in fish are still unclear. There are two copies of the kdm4a gene in zebrafish, namely kdm4aa and kdm4ab, kdm4aa was edited using CRISPR/Cas9 technology in the present study, then homozygous kdm4aa mutants (kdm4aa−/−) were obtained, and loss of kdm4aa was confirmed by sequencing and increased H3K9me3. Whole-mount in situ hybridization showed that kdm4aa is widely expressed during the embryonic development of zebrafish. Compared with WT zebrafish, kdm4aa−/− zebrafish showed no significant difference in gamete formation and fertilization, but the survival rate of kdm4aa−/− embryos dramatically reduced to 21% at 26 hpf. Further observation showed that about 80% of survived kdm4aa−/− zebrafish experienced disruption in stripe formation, and 10% of survived kdm4aa−/− zebrafish underwent vertebral malformation. Alizarin red S staining demonstrated the abnormal spinal development in kdm4aa−/− zebrafish. These results indicated that kdm4aa is required for normal embryonic development of zebrafish, loss of kdm4aa function leads to decreased survival during the early stages of zebrafish development and morphological variation in adult zebrafish.

China has been the top aquaculture producer in the world since 2002. Over 800 species and 240 improved varieties have been used in China's aquaculture, which is the most diverse collection of species on this planet. Species diversification, along with other aquaculture technologies, contributes significantly to the increase of China's aquaculture production, whereas the use of too many species in aquaculture has resulted in some issues related to the environment and sustainability. We provide an updated overview of the species currently used in Chinese aquaculture in this paper. We examine critically the main drivers of species diversification in China with examples. We also introduce Chinese approaches to improve and certify new species and varieties for commercial production. We believe that further species diversification is not a priority in China's aquaculture, while further improvement of aquaculture technologies for major and native species is essential for green, profitable, and sustainable (GPS) aquaculture. The implications of China's experiences with species diversification for global aquaculture species diversification are discussed.

Using the multi-product dual revenue function framework, this paper examines the nature and extent of technical and economic interactions among five demersal species of Al-Batinah demersal fishery, Oman during the 2010–2016 period. The parameters of the system of output supply functions are estimated using Zellner's seemingly unrelated regressions (SUR) technique. The likelihood ratio test in relation to the structure of the multi-output production technology rejects the null-hypothesis of input-output separability and non-jointness in inputs. These results suggest that the underlying production technology is non-separable between the outputs and the quasi-fixed input, and the harvesting level of one species is likely to have spill-over economic effects on the harvesting levels of others. The own-price elasticities of output supply are found to be positive, inelastic, and statistically significant in four out of five cases suggesting that, other things being equal, fishers' supply decisions are influenced by the prevailing market prices of outputs. The estimated values of the cross-price elasticity of supply are negative, inelastic and statistically significant at the 5% level for eight output pairs. The calculated values of the Morishima elasticity of substitution (MES) indicate the presence of substitutability between ten output pairs. The cross-price elasticity estimates are in the range of −0.001 (between Emperor and Catfish) to −0.275 (between Seabream and Grouper) which is lower (in absolute value) than that of the MES estimates. The magnitudes of the cross-price elasticity and the MES estimates indicate the extent of spill-over effects of one species on the other and signal the extent of species targeting by fishers. A statistically significant spatial, seasonal, and inter-annual variability is observed in all species cases. Finally, the implications of the findings are discussed from the perspective of developing effective management approaches, achieving sustainability of fisheries resources and improving fishers' socio-economic conditions stipulated in the Five-Year development plans for the sector.

Paphia textile is an economically important bivalve cultured in southeastern China. The feet, as the main edible part of P. textile, vary in color from white to orange. Previous studies have suggested that the orange feet of P. textile contain higher levels of carotenoids than the white feet, but the kinds of carotenoids are not known. The pigments identified in this study can facilitate further analysis of their underlying molecular mechanism and enable the breeding of P. textile with high carotenoid content. The pigments were extracted from the orange feet of P. textile by an acetone extraction method, and then, the extracted pigments were analyzed by liquid chromatography-mass spectrometry (LC-MS). Moreover, the MS analysis was carried out with an electrospray ionization (ESI) source in the positive (ESI+) and negative (ESI-) ion modes. A total of 47 substances were detected, including 9 terpenoids, 7 amino acids and peptides, 13 lipids, 9 organic acids, 2 types of vitamin A and 7 other substances. Furthermore, Î⊃2;-doradecin (3'-hydroxy-3,4-diketo-Î⊃2;-carotene) was identified as the main pigment in the feet. This is the first report of the presence of Î⊃2;-doradecin, a type of carotenoid, in bivalves.

In triangle sail mussel (Hyriopsis cumingii), shell biomineralization is a complicated process that involves multiple gene products. Shell matrix proteins are involved in the formation of the organic framework and play an important role in the regulation of calcium carbonate deposition. In this study, A new shell matrix protein gene Hc-transgelin was identified in H. cumingii. The full-length cDNA of Hc-transgelin was 1200 bp, including a 501 bp open reading frame, which encoded 166 amino acids. Hc-transgelin is rich in lysine, it accounts for 11.40% of the protein. The predicted transgelin protein contained a conserved calmodulin homologous domain. A tissue-specific expression assay indicated that Hc-transgelin exhibited significantly highest expression in the mantle. Furthermore, Hc-transgelin in situ hybridization detected positive signals at the edge of the mantle outer fold, where nacre and prismatic layer biomineralization occur. An RNA interference assay showed that the shape of aragonite flakes in nacre changed and their growth was inhibited, and cracks appeared in the prismatic layer organic sheath when the expression of Hc-transgelin was suppressed. In a shell repair assay, a higher expression of Hc-transgelin appeared from day 12 to day 25 when the nacre accumulated quickly. These findings indicate that Hc-transgelin may be involved in the formation of aragonite flakes in the nacre and play a role in the formation of the organic sheath in the prismatic layer of the shell. This study provides new insights into the role of the Hc-transgelin gene and also contributes to the molecular understanding of mollusk shell formation.

Reproduction is one of the most crucial physiological processes for the continuation of the generation of any species. Teleost are one of the most divergent aquatic species. The reproductive neuro-endocrine regulatory studies are limited to only few species. Neuroendocrine regulation is a finely tuned complex mechanistic pathways, involving mainly hypothalamic-pituitary-gonad (HPG) axis. Within the HPG axis, gonadotropin-releasing hormone (GnRH) modulates the synthesis and release of pituitary gonadotropins, which act on the gonads to stimulate steroidogenesis and gametogenesis. Very recently, several novel neuropeptides, associated with reproductive regulation, have been identified. Spexin (SPX), a novel neuropeptide coevolved with the galanin/kisspeptin family, has been identified as a regulator of the species-specific reproductive processes in teleost. Pituitary adenylate cyclase-activating polypeptide (PACAP) is another novel member of the secretin-glucagon peptide family that functions as a hypophysiotropic factor involved in regulating pituitary hormone secretion in fish. These two emerging neuropeptides have pleiotropic functions, but information regarding their exact roles in fish reproduction is very limited. An updated overview of the mechanistic reproductive functions of these two new neuropeptides are highlighted in this review.

Responsible stock enhancement initiatives require baseline data of wild population demographic conditions that can be used in testing management outcomes. This study provides the first fishery-independent assessment of length- and age-based biological characteristics of exploited populations of Platycephalus fuscus in eastern Australia prior to stock enhancement. Sampling was conducted over seven estuaries spanning seven degrees of latitude and the geographical range of proposed stock enhancements. Populations in all estuaries showed evidence of length and age truncation, especially those subject to commercial fisheries where young individuals of both sexes dominated populations. Maximum longevities were 12 and 11 years for females and males respectively, but few females >5 years and males >3 years were generally sampled. Females dominated populations, and on average, the mean lengths and ages of females were greater than males within each estuary and across all age classes. Sexually dimorphic variation in growth was evident across all estuaries, with females attaining greater maximum lengths than males. Estuary-specific differences in individual growth were not identified. On average, over 50% of females sampled in each estuary were > the minimum legal length (MLL), but the opposite was evident for males. In contrast, over 25% of males in each estuary were > the mean length at maturity (L50), whereas in all but one estuary the L50. Stocked male and female P. fuscus should recruit to the fishery in 2 and 3 years, and contribute to the spawning stock in 1.5 and 4.5 years, respectively. This study provides important historical baseline data that can contribute to testing stock enhancement outcomes on populations.

Carnobacterium is a genus of Gram-positive bacteria, within family Carnobacteriaceae, and they are catalase- and oxidase-negative, non-sporing bacteria with properties such as CO2 and L (+)- lactic acid production from glucose, but they are not able to grow on acetate agar. They are ubiquitous lactic acid bacteria and have been isolated from both cold and temperate environments, and they are identified as components of the microbiota in the gastrointestinal (GI) tract of salmonids and several other fish species of which Carnobacterium (piscicola) maltaromaticum, Carnobacterium mobile, Carnobacterium divergens, Carnobacterium alterfunitum, and Carnobacterium inhibens are reported. During the last two decades several studies have revealed that carnobacteria can act as probiotics to promote health benefits of fish, as well as they in ex vivo studies to some extent can out-compete pathogens. In addition to beneficial effects, information is available that some carnobacteria species causing fish disease. The aim of the present review is to present an updated overview of Carnobacterium in fish, with focus on their presence in the GI tract, their use as probiotic supplement and general information on pathogenic carnobacteria.

Crucian carp (Carassius auratus gibelio), an extensively cultivated freshwater fish, was one of the model species for the study of fish immunology. Polyclonal antibodies were advantageous molecular tools for studying teleost immune system. Specifically, polyclonal antibodies reacting with immunoglobulins (Ig) were used successfully in studies of the teleost fishes. In the present study, we produced polyclonal antibody against CH2 domains of crucian carp IgM, and measured the in vivo dynamics of IgM mRNA caused by CyHV-2 infection. The recombinant protein IgM with relative molecular weight about 53 KD was correctly expressed in prokaryotic cells. The specificity of the polyclonal antibody was evaluated by Western blotting and results revealed that the antibody not only specifically recognized crucian carp serum but also cross-reacted with grass carp serum. Quantitative RT-PCR analysis demonstrated the expression of IgM mRNA changed significantly after CyHV-2 infection. The expression of IgM in the kidney increased and reached a maximum at 6 h post-infection (hpi), while dropped to a low level at 5 days post-infection (dpi). In conclusion, the expression of IgM was significantly upregulated in the kidney of crucian carp infected with CyHV-2, indicating that IgM played a potential role in systemic immunity against viral infection. Polyclonal antibody against crucian carp IgM had certain clinical relevance, which might provide insight into the early stage of virus infection and prevention of the disease.

Biomarkers are biological molecules that provide information about the physiological condition of an organism such as early signals of health deterioration. The aim of this study was to compare the relative gene expression of four molecular biomarkers related to oxidative stress, and neuronal damage in Piaractus brachypomus under three different conditions (exposure to chlorpyrifos (CPF), menthol and eugenol anesthesia, and brain injury). Bioinformatic analyses were conducted to design primers for the molecular biomarkers, then, the relative gene expression of COX1, GPX1, BDNF and CALB1 genes was measured by qPCR using brain tissue cDNA from the treated animals as template and 2-ΔΔCT method was performed. EF1a gene was used as reference gene. The results showed a response to chemical stress in the CPF treatment samples where GPX1, BDNF and CALB1 genes were up-regulated. Finally, in menthol/eugenol and brain injury treatments, no alterations in the relative gene expression were observed.

Activin A receptor, type II (Acvr2) is a member of the transforming growth factor beta receptor family and can function as a negative regulator of skeletal muscle mass. Acvr2 plays an important role in regulating muscle development that can inhibit skeletal muscle growth in mice. However, there is very little research reported on the function of acvr2 in muscle development of teleost. In this study, we analyzed the effect of acvr2aa and acvr2ba on muscle development in zebrafish. Growth rates of WT and acvr2a−/−b−/− were measured from juvenile stage to adult stage. In addition, effects of acvr2 on skeletal muscle were tested in histological, protein and molecular levels. As a result, acvr2a−/−b−/− exhibited a wider body trunk than WT and showed a significant increase in body weight and width from two months old. Histological analysis of skeletal muscle indicated that the size of muscle fiber in acvr2a−/−b−/− (female:1809 ± 123 μm2; male: 2261 ± 130 μm2) was larger than that in WT (709.8 ± 49 μm2; 815 ± 53 μm2). In addition, western blot of fast MyLc protein showed the protein synthesis of acvr2a−/−b−/− are increased. Besides, Histological analysis of heart showed the ventricle area is aslo increased in acvr2a−/−b−/−. Our results demonstrated acvr2 attends the development of muscle fiber and will cause muscle hypertrophy when they were knocked out in zebrafish. In conclusion, acvr2 in zebrafish can control the development of muscle fibers during posthatch growth.

Abstract

In recirculating aquaculture systems, nitrification is usually accelerated by inoculating nitrifier or mature biocarriers. In this study, the performance of the establishment of nitrification in the MBBR according to three different strategies: conventional method (Control group A), inoculation with biofloc recovered from a tilapia biofloc culture system (Group B), and addition with extra nitrite (Group C) in the Moving bed biofilm reactor (MBBR) was compared. Among them, the biofloc-inoculated group considerably accelerated the nitrification process in the MBBR (38 d), which is roughly 18 d faster than the control group (A) (56 d) and 21 d faster than group C (59 d). Less ammonia (8 mg/L NH4+-N, 10 mg/L in other groups) and external nitrite (2 mg/L NO2−-N) in the influent caused effluent ammonia to drop more slowly (5 d slower than the control group, 8 d slower than the B group), which is detrimental to the nitrification process' development. Notably, the influent's hydraulic retention time (HRT) was reduced from 12 h to 6 h following the successful establishment of nitrification. During the adaptation to reduced HRT, the MBBR inoculated with biofloc experienced short-term changes in the water quality index of the effluent water, whereas the other groups did not. The biofilm seeded with biofloc had the highest mean gray value ratio (1.42) of live/dead cell fluorescence, which grew better and could cover the entire groove under multiple microscope observations. However, the other groups did not demonstrate a similar trend. In summary, the research found that seeding biofloc use as nitrification bioaugmentation into the MBBR of the recirculating aquaculture system (RAS) to greatly speed up the nitrification process.

The size selectivity and catch pattern of Trichiurus lepturus in 40 mm diamond and square mesh codends were investigated in this study. A 34 m high opening trawl was used, which is a common design used by fishermen operating along the northwest coast of India, and the cover codend method was employed to determine codend selectivity. Along with the changes in the length at 50% retention rate for Trichiurus lepturus with the usage of the square and diamond mesh codends, indicators to understand the exploitation pattern of this species in the fishery were assessed based on the total number of individuals and on total weight of the catch. The mean selection length increased and discard fraction is reduced when 40 mm square mesh codends are used in place of diamond meshes, however, it is observed that individuals at commercial length are also lost. The results demonstrate that mandatory use of legal mesh sizes alone will be insufficient to aid in the sustainable harvest of this species, given its estimated length at first sexual maturity of 61.2 cm. This is the first study to compare the size selection of this species in 40 mm diamond and square mesh codends along Northwest coast of India. Results of the study will help as a baseline for gear-based regulations in the region.

Seaweed is a promising marine macroalgae of the millennium, providing various ecological, social, and economic benefits. At present, seaweed production reached 35.8 million t from farming, accounting for 97% of global seaweed output, with a world market of US$ 11.8 billion. Seaweeds are an excellent source of nutritious human food because of their low lipid content, high minerals, fibers, polyunsaturated fatty acids, polysaccharides, vitamins, and bioactive compounds. Many seaweed sub-products offer unique properties to develop various functional foods for the food processing industries. In the perspective of climate change mitigation, seaweed farms absorb carbon, serve as a CO2 sink and reduce agricultural emissions by providing raw materials for biofuel production and livestock feed. Seaweed farming system also helps in climate change adaptation by absorbing wave energy, safeguarding shorelines, raising the pH of the surrounding water, and oxygenating the waters to minimize the impacts of ocean acidification and hypoxia on a localized scale. Moreover, it contributes substantially to the sustainable development of the economic condition of coastal women by providing livelihood opportunities and ensuring financial solvency. This review paper highlights the significance of seaweed farming in global food and nutritional security, mitigation and adaptation to global climate change, and women empowerment within a single frame. This review paper also outlined the major issues and challenges of seaweed farming for obtaining maximum benefits in these aspects. The main challenges of making seaweed as a staple diet to millions of people include producing suitable species of seaweeds, making seaweed products accessible, affordable, nutritionally balanced, and attractive to the consumers. Various food products must be developed from seaweeds that may be considered equivalent to the foods consumed by humans today. Lack of effective marine spatial planning to avoid user conflicts is vital for expanding the seaweed farming systems to provide aquatic foods and contribute globally for mitigation and adaptation of climate change impacts. Hence, women's empowerment through seaweed farming is primarily constrained by the lack of technical knowledge and financial resources to establish the coastal farming system. All the information discussed in this paper will help to understand the critical needs for large-scale seaweed farming for climate resilience mariculture, potentials for global food security, and future research on various aspects of seaweed farming and their diverse utilization.

An essential aspect of product quality of aquatic foods is the rapid and accurate identification of bacterial species. From this perspective omics technologies prove to be very useful in the assessment of the quality and safety of seafood products. Such technologies can identify and detect low levels of contamination by pathogenic and spoilage bacteria and can be used to study the effects caused by processing and storage of seafood products. The integration of food processing with the monitoring of the microbial characteristics using conventional microbiological assays, coupled to molecular techniques may establish the baseline for the development of quicker and more sensitive and reliable methods for seafood safety screening. The use of combined omics technologies, including metagenomics, proteomics and metabolomics, coupled to conventional quality indices such as colour, texture and flavour offer a new tool for novel processing optimization to ensure seafood quality. The aim of this brief review is to outline how omics technologies can generate novel tools for integration into seafood processing and quality control. Considering that the main aspect of the review is the improvement of safety and quality of the final product, from production to consumption, emphasis is given to microbial identification and metabolite detection, the evaluation of the allergenic capacity of fish and seafood and optimization of postharvest processing. Deployment of omics for identification of potential microalgal products of relevance to seafood quality and safety is also considered.

The average values of the seasonal flesh biochemical composition (%) of the pearl oyster Pinctada imbricata radiata originated form 2 sampling sites, the gulfs of Evoikos (E) and Saronikos (S) in the Western Aegean Sea, showed that is rich in proteins (64.00 ± 1.86 -(E), 64.67 ± 2.95-(S)) with low fat content (10.96 ± 1.04-(E), 11.86 ± 1.13-(S)) and carbohydrates (13.29 ± 2.48- (E), 9.94 ± 4.32 (S)). The condition index ranged from 26.16% ± 5.04 in the autumn in (E), to 44.73% ± 7.50 in the summer in (S). The meat yield varied from 20.49% ± 3.20% in the summer in (E) to 30.73% ± 3.47% in the summer in (S). Both results demonstrate the high nutritional profile of the pearl oyster, supporting its suitability as a potential new Mediterranean seafood source for human consumption.

Reliable, nondestructive fish freshness evaluation applicable during fish commercialization has been continuously pursued by scientists and industry. Taking into account that fish texture is primarily affected even at early stages of post-mortem storage, a relevant nondestructive testing framework for rapid textural assessment of fish freshness was developed in the past. Herein, an algorithm operating within the aforementioned framework and optimized for use in industrial environments is proposed. Sea bass (Dicentrarchus labrax) both freshly killed and stored on ice for 6 days have been used for comparative testing. The fish is part of a system, which is vibration-tested via a new testing protocol designed for easy implementation and robustness to noise. At the same time, a new closed-form analytical expression for the system response to the specific testing is computed and used along with experimental data, for obtaining specific mechanical (thus muscle-structural) characteristics of fish flesh. This computation is designed to only require readily available routines found in most relevant software. The algorithmic operational framework has been used in two different test setups (a custom-built test rig and a prototype device), with results following remarkably similar trends, clearly discriminating different textural (thus freshness) characteristics, and consequently validating the proposed approach.

Mediterranean mussel farming in Greece developed considerably during the last 40 years reaching a gross commodity product up to the limits of the country's production capacity (35–40,000 tonnes/year). Despite the achievements in the sector's growth, little or no effort has been attributed yet to risk assessment and moreover to risk management of the activity. The present effort aims at developing a working framework for the shellfish aquaculture of Greece to be used as a tool by the sector's decision makers to advance strategies for risk elimination or avoidance. The work was based on a generic risk management standard tool, the Joint Australian and New Zealand Risk Management Standard AS/NZS ISO 31000:2009 that has been adapted to the specific national characteristics of all levels of the mussel farming business -activities and the industry function. The framework supported by data sets regarding development, production, profits and losses, retrieved by surveys through distributed questionnaires or interviews during site-visits, as well as by collecting data from national and international authorities. Data input covered technology, farm size, farmer risk-attitude, risk-management strategies, risk-perceptions and socioeconomic profiles. Major risks and risk management options were identified providing aid for remediation risk policies to the stakeholders.

Pangasius hypophthalmus is the most cultured freshwater fish by smallholder farmers in Indonesia. One of the main challenges in the production is the highly weathered and infertile soils on the bottom of a pond that influences aquaculture productivity. This work investigated the effects of pond age on soil quality, water quality, benthic algae population, and P. hypophthalmus production. We carried out a field experiment in a randomized design with pond age of 4 levels: Ponds aged 0–5 years (P1), 6–10 years (P2), 11–15 years (P3), and 16–20 years (P4). The soil is a Typic Palaeudult (Ultisol), and fish were grown for three months. The results showed that the chemical soil quality parameters and soil organic matter content increased linearly with pond age, resulting in the enhancement of water quality parameters. The increase in nitrate and phosphate directly affected benthic algae richness. These, in turn, in the highest fish production in P3, 6.4 kg/m2, specific growth rate was 3.76 %/d, survival rate of 66.7%, and feed conversion ratio of 1.8%. Linear correlation coefficients indicated that the contents of total N, total P, and organic carbon in the bottom soil of the pond were related to the increase in phosphate, nitrate, and organic matter content in pond water. Total N content, total P, carbon organic matter, C/N ratio, and CEC value in pond bottom soil significantly correlated to Pangus fish production. C/N ratio, CEC value in pond bottom soil, and CO2 concentration in pond water significantly correlated to fish survival rate. Multiple linear regression indicated that fish production was significantly related to the pond age, water NH3, total alkalinity, and soil total P and C/N ratio (R2 = 0.99, P 

Coilia nasus is an endangered fish species in the Yangtze River, and there is urgent need to know the genes related to its reproduction and fertility. The DAZ family including boule, daz and dazl, plays an important role in germ cells development. In this study, the cDNA sequence of boule (Cnbol) and dazl (Cndazl) genes were cloned and their expression patterns were characterized in Coilia nasus. RT-PCR showed that the expression of Cnbol and Cndazl mRNAs was restricted in adult gonads. The section in situ hybridization indicated that the temporospatial expression patterns of Cnbol and Cndazl were significantly different. In the testis, Cnbol was mainly detected in spermatocytes and spermatids, while Cndazl was prominently expressed in s permatogonia. In the ovary, Cnbol and Cndazl were highly expressed in the early stages of oocytes. Interestingly, Cndazl was also concentrated in perinuclear speckle and then localized to the Balbiani body in late stages of oocytes. In addition, Cnbol and Cndazl 3â€⊃2; UTR can specifically label medaka Primordial Germ Cells (PGCs). According to our results, Cnbol and Cndazl are marker genes of germ cells and may play a vital role in the development and differentiation of germ cells in Coilia nasus.

In Amazonia, small-oriented family businesses or communities cultivate freshwater organisms as a source of income. Although effective management is fundamental for optimizing cultivated stocks, Amazonian aquaculture belittles the importance of genetic diversity, relying primarily on phenotypical characteristics during breeders’ selection. To provide a “proof of concept” built on the premise that implementing modern technologies is crucial to optimizing fish stocks in rural Amazonian fish farms, we conducted a pilot study assessing genetic diversity on cultivated Piaractus brachypomus from Caquetá, Colombia. We used mitochondrial control region (CR) sequences to evaluate heterogeneity. Our data revealed low genetic diversity and suggested that most sampled individuals probably originated from a single maternal lineage. Haplotype diversification resulted from discrete point mutations not associated with geographical location. Polymorphisms accumulate in non-conserved CR regions, yet the most divergent haplotypes display mutations in conserved CR sequences with roles in mitochondrial metabolisms and proliferation. Overall, our results indicate a need in the local industry to design breeding strategies to enhance diversity to avoid deleterious effects caused by inbreeding and domestication.

Changes in protein quality during ice storage affects the muscle structure, the textural quality, functional properties and the eating quality. Dynamic viscoelastic behaviour and gelling properties ofmeat proteinsin relation to histological changes in white leg shrimp muscles were assessed for 14 days in ice storage. Reduction in Ca2+ ATPase activity of fresh myofibrillar protein (MFP), fading of myosin banding pattern and increased gapping in myofibrils were clearly observed with progress of storage. The quality indices of the shrimp muscle were well correlated with histological and functional properties as a function of ice storage. Solubility of fresh MFP was 86.76% which decreased to 77.06% on the 14th day of storage period. Emulsion capacity found to increase during storage period. Gel strength of white leg shrimp meat was low (81 ± 14 g cm) and further, reduced nearly 60% compared to fresh sample at the end of storage. The considerable reductions (from 535.77 kPa to 246.56 kPa) in storage modulus values were evident of diminishing elasticity and gelling ability of the meat due to ice storage.Therefore, this study usherd that the histological deterioration in myofibrils may be used as an indication of diminishing biochemical quality and gelling behaviour of the proteins.

The peritoneum is mainly composed of mesothelial cells, fiber cells, and fibers, with many free cells that come from tissue capillaries. Siniperca chuatsi is a valuable fish commodity and important freshwater aquaculture species in China. With the increase in the scale of its breeding, bacterial and viral disease of the S. chuatsi has become increasingly rampant in recent years. This study analyzed the peritoneal gene expression profile using transcriptome technology for the first time. The results showed that 95,711 unigenes were expressed in the peritoneum with an average length of 920.72 bp. In addition to the housekeeping genes, the genes of extracellular matrix protein 1a (ecm1), Angiopoietin-related protein 4-like (angptl4) and cysteine-rich protein 1 (crip1) were highly expressed genes in the peritoneum, and they are key factors in peritoneal development and the maintenance of morphology. Meanwhile, many immune genes were also expressed in the peritoneum, including beta-2-microglobulin (b2m), MHC II invariant chain (cd74), prostate stem cell antigen-like protein (psca), claudin (cldn), heat shock protein 90 (hsp90), complement component 4 (c4), radical S-adenosyl methionine domain-containing protein 2 (rsad2), and cathepsin S (ctss). The RT-PCR results showed that different genes exhibited different expression profiles. The transcriptome data indicated that b2m, cldn, hsp90, c4, and rsad2 were highly expressed in the peritoneum. b2m, cd74, psca, c4, and ctss were highly expressed after embryonic hatching, whereas cldn, hsp90, and rsad2 were expressed at early embryonic stages. Quantitative PCR demonstrated that b2m, cd74, cldn, hsp90, c4, and ctss genes were highly expressed after immunostimulation. This study provides significant data for studying the morphological and functional diversity of fish peritoneum and lays a foundation for research on mandarin fish immunity.

The blood clam (Tegillarca granosa) is an economically important marine shellfish in the southeast coastal area of China. In T. granosa breeding practice, growth-related traits are most important phenotypic selection index. In order to increase the breeding efficiency, we used a previously published genetic linkage map of T. granosa to map quantitative trait loci (QTL) for growth-related traits in a single full sibling F1 family. Eight growth-related traits including shell length (SL), shell height (SH), shell width (SW), shell weight (Swi), shell umbo width (SUW), as well as outer ligament length (OLL), meat weight (MW) and total weight (TW) of T. granosa were measured for QTL mapping. The estimated phenotypic correlations between any 2 of the 8 growth-related traits were significant (P 

Spawning performance -relative fecundity and fertilization success- was studied in two hatchery-reared broodstocks of gilthead seabream (Sparus aurata) held under relatively constant well-water temperature (18–20 °C) and simulated natural photoperiod, for five consecutive spawning seasons, between 3 and 7 years of age. The spawning season lasted between 4 and 6 months each year, and the total number of eggs produced annually ranged between 1 480 000 and 3 100 000 eggs/kg female body weight, being the highest during the first and second spawning season. No difference was observed in monthly relative fecundity between years -although high variation existed within years, whereas fertilization success was the highest during the second and third reproductive season, and dropped significantly during the last year of the study. The male percentage of the broodstocks was 35% during the first spawning season of the females, and thereafter it decreased further and remained stable at around 15%–20% for the second and third spawning season. Substitution of older females with smaller males to readjust male percentage to 50% in the fourth spawning season, was followed by sex change of larger males to females and a drop of the male percentage to 18% in the following spawning season. The present study demonstrated the long spawning season of gilthead seabream -especially under constant water temperature, the high fecundity and fertilization success, and the stabilization of male percentage to ∼20% after the first spawning season or when a broodstock is modified to increase male percentage. These results are useful to the aquaculture industry, demonstrating that there is no need to add males to gilthead seabream broodstocks over the years, as the sex ratio is stabilized and egg production and fertilization success remain high with a relatively low male:female sex ratio.

This review highlights the recent developments regarding neuroendocrine mechanisms controlling teleost reproduction. In teleosts, the pituitary gland receives major neuronal innervations from Gnrh neurons as well as minor innervations from small population of neurons that will secrete neurotransmitters and/or neuropeptides. The diversity of Kiss/Kissr system in various teleost species and their actions in the context of HPG axis and reproduction has been extensively covered. In teleost model systems, zebrafish and medaka, mutant lines for key components of the HPG axis have been generated through targeted mutagenesis but surprisingly most of the mutants developed normally without major defects in reproduction; these mutant phenotypes are described. In the last decade, complex role of diverse neuropeptides in teleost reproduction is being revealed. A brief overview about the reproductive functions of neuropeptides is presented. Finally, the effects of environmental factors namely photoperiodism and temperature on the functions of HPG axis is summarised.

Wastewater treatment plants release complex mixtures of chemicals into the aquatic environment as wastewater effluent (WWE); however, the effects of these mixtures are still poorly understood. Chinook salmon (Oncorhynchus tshawytscha) are a culturally important species in the Pacific Northwest and are a vital food resource for southern resident killer whales (Orcinus orca) that are listed as ‘critically endangered’ under the U.S. Endangered Species Act (ESA). Chinook populations have declined drastically in this region and have failed to show significant recovery despite regional-to-federal efforts, resulting in many populations being listed as threatened under the ESA. One source of stress to juvenile Chinook is chemical pollution from WWE during their outmigration along river corridors and residency in estuaries. In this study, we investigated effects of WWE on juvenile Chinook health in a ten-day exposure to dilutions of WWE from 0.1% to 20%. At the end of the exposure, we measured endpoints associated with endocrine disruption, brain function, osmoregulation, stress, and metabolism. Exposure to WWE significantly (α = 0.1 for all analyses) induced vitellogenesis, indicating endocrine system disruption. We saw significant reductions in plasma glucose, an indication of stress, and brain Na+/K+-ATPase (NKA) activity, an enzyme essential for neuronal signaling. Lastly, metabolism was affected as evidenced by altered total protein, cholesterol, and albumin in plasma, a drastic decrease in whole body lipid content, and a significant increase in visible liver anomalies. We compared contaminant concentrations in exposure water with effects concentrations from the literature for chemicals known to induce vitellogenin or inhibit brain NKA. For most contaminants, concentrations in exposure waters were several orders of magnitude below effects concentrations in the literature. The exception was estrogenic hormones, which were detected at similar concentrations in this study compared to concentrations in other studies that induced vitellogenin. Based on comparisons to the literature, contaminants measured in this study could not explain the inhibition of brain NKA; however, WWE mixtures contain many quantified and undetected compounds that are likely acting together to cause harmful effects in Chinook. This research highlights the need for improved wastewater treatment to improve aquatic health and mitigate effects to threatened species like Puget Sound Chinook salmon.

A cell line, termed ZFIN, was established from the caudal fin of zebrafish and was shown to be susceptible to spring viremia of carp virus (SVCV). The ZFIN cells are epithelial like cells and have a moderate plasmid transfection efficiency of 13.9%. Using an RNA-seq approach, differentially expressed genes (DEGs) regulated by SVCV were identified. Infection of SVCV gave rise to 3931 DEGs and up-regulated DEGs were mostly enriched into the biological regulation and cellular processes, among which pathways for the type I interferon signaling and the response to exogenous dsRNA were the top two GO terms. Several KEGG signaling pathways including TLR signaling pathway, RLR receptor signaling pathway, cytosolic DNA-sensing pathway, NLR signaling pathway, cytokine-cytokine receptor interaction and ferroptosis were significantly enriched. Antiviral genes including ifnφ1, isg15 and mx were significantly up-regulated. In addition, key DEGs involved in autophagy were identified. The results indicate that the ZFIN cell line provides a useful in vitro tool for study on the gene functions and cellular responses to viral infection in fish.

Genetic breeding is an important approach to improve the economic traits of aquaculture animals. Unfortunately, the genetic basis for important economic traits of red swamp crayfish, including growth-related traits, has not yet been reported. In the present study, two full-sib families and two natural populations were employed to identify quantitative trait loci (QTLs) for growth-related traits of red swamp crayfish. In total, 28 QTLs for five growth-related traits, including body weight, body length, carapace length, carapace width, and abdomen length, were repeatedly identified in more than two families/populations, by means of association analysis; nine of these displayed a heterosis effect. The phenotypic variations of the five investigated traits explained by the 28 QTLs ranged from 4.2% to 19.0%. Eight additive and three heterosis QTLs were further successfully validated using comparative analysis of favoured alleles between the small and big size crayfish groups in the natural population. In conclusion, this study investigated the genetic basis of growth-related traits in red swamp crayfish, which is of great significance for their application in the future molecular breeding of the species.

Crisp Nile tilapia (Oreochromis niloticus) is a kind of valuable fish product with high muscle firmness and crispiness texture. However, with the change of physicochemical in crisp Nile tilapia, the frozen storage parameters and quality would be different comparing to normal Nile tilapia. Thus, the aim of this study was to analyze the changes in texture, chemical quality indices and volatile compounds of Nile tilapia fillets during frozen storage. The remaining storage time of the crisp Nile tilapia fillets could be estimated within 120 days. During frozen storage, fillets resulted in softer started at 90-day, and 36.75%, 45.74%, 48.81% and 20.37% reduction of hardness, springiness, gumminess and chewiness were observed at 120-day. Thiobarbituric acid reactive substances (TBARS) for frozen samples showed similar with fresh fillets within 60 days, while the TBARS was 1.97 folds higher than fresh one at 120-day. Low-field nuclear magnetic resonance (LF-NMR) indicated that the water loss of Nile tilapia fillets was significant changed at 120-day, which reduced more than 12.5% water out of weight. The volatile compound analysis showed that more free fatty acid will be detected at 120-day comparing to the fresh fillets. The combined results demonstrated that the crisp Nile tilapia fillets had the best quality before 60 days frozen storage then loss of some quality properties in longer freezing. Thus, these results identified the ideal storage strategy for the preservation of crisp Nile tilapia without affecting sensory appeal and commercial value.

Aquaculture largely contributes to aquatic products and consequential dietary protein for many households. Aquaculture, just like every other food sector, is faced with enormous challenges such as unfavorable climatic events, environmental stressors and contaminants. Microplastics (MP) are emerging contaminants in aquaculture following their perturbing occurrence in cultured fish, fishmeal and aquafeed. Several MPs pathways into aquaculture facilities include wastewater, pipe-borne water, dilapidated aquaculture facilities, fish gears, and aquafeed stuff (fishmeal). Techniques for the digestion, identification and characterization of MPs are critical to understanding their pathways, bioavailability and bioaccumulation patterns in aquaculture species. The impacts of MPs on cultured fish species are identified as impaired growth, oxidative stress, neurotoxicity, reproductive toxicity, immunotoxicity, embryotoxicity, and histopathology. Bioaccumulation of MPs in tissues and biological systems have been evidenced in several cultured fishes. Mitigation efforts cum strategies such as upgrade of wastewater treatment facilities, screening of inlet pond water, screening of aquafeed stuff, regular maintenance and repair of culture facilities, could be effective to eradicate MP contamination in aquaculture. Additionally, regulatory policy on the use of plastics is key to mitigating the impact of MPs and ensure cleaner and sustainable aquaculture.

The Malaysian mahseer (Tor tambroides), one of the most valuable freshwater fish in the world, is mainly targeted for human consumption. The mitogenomic data of this species is available to date, but the genomic information is still lacking. For the first time, we sequenced the whole genome of an adult fish on both Illumina and Nanopore platforms. The hybrid genome assembly had resulted in a sum of 1.23 Gb genomic sequence from the 44,726 contigs found with 44 kb N50 length and BUSCO genome completeness of 87.6%. Four types of SSRs had been detected and identified within the genome with a greater AT abundance than that of GC. Predicted protein sequences had been functionally annotated to public databases, namely GO, KEGG and COG. A maximum likelihood phylogenomic tree containing 52 Actinopterygii species and one Sarcopterygii species as outgroup was constructed, providing first insights into the genome-based evolutionary relationship of T. tambroides with other ray-finned fish. These data are crucial in facilitating the study of population genomics, species identification, morphological variations, and evolutionary biology, which are helpful in the conservation of this species.

The objective of the study was to investigate the efficiency of slurry ice during harvesting and transportation of European sea bass (Dicentrarchus labrax) to retain flesh quality and extend shelf life, compared with conventional flake ice. Fish was slaughtered and transported in different mixtures of slurry ice and conventional flake ice (C: slaughtered and transported in 100% flake ice-Control samples, SC: slaughtered in 100% slurry ice and transported in 100% flake ice, S50: slaughtered and transported in 50% slurry ice-50% flake ice, S100: slaughtered and transported in 100% slurry ice) and subsequently stored under controlled isothermal conditions at 0 °C for shelf life modelling and flesh quality evaluation (proteolytic enzymes). The replacement of conventional flake ice with slurry ice as a slaughtering method led to improved quality stability during subsequent refrigerated storage and shelf life extension, in terms of microbial growth, flesh quality and sensory degradation of fish. Based on microbial growth, the shelf life of C samples was found to be 19 days, whereas the shelf life of S50/S100 and SC was 21 and 25 days, respectively, showing that the replacement of flake ice with slurry ice resulted in 2–6 days shelf life extension of whole sea bass stored at 0 °C. The use of slurry ice at slaughter and flake ice in transportation was accompanied by low activities and late peaks of all four enzymes that is expected to lead to delayed proteolytic degradation and extended freshness.

Fish constitute important high protein products to meet the demands of an increasing global population. However, the continued depletion of wild fish stocks is leading to increased strain on the aquaculture sector in terms of sustaining the supply of fish and seafood to global markets. Despite the fact that aquaculture is more diversified than other agriculture sectors, there are significant pressures on the industry to continue innovating in order to enable sustainability including increased fish production, improved appropriate selection of species, disease mitigation, reduced wastage, preventing environmental pollution and generating more employment globally. This viewpoint article addresses how digital transformation can help support and meet expansion needs of the fisheries/aquaculture industries that includes exploiting and harnessing ICT, IoT, Cloud-edge computing, AI, machine learning, immersive technologies and blockchain. Digital technologies are bringing significant operational benefits for global food chain, improving efficiencies and productivity, reducing waste, contamination and food fraud. The focus on digital technologies has recently evolved to Industry 5.0 where AI and robotics are coupled with the human mind in order to advance human-centric solutions. This viewpoint describes the role of Quadruple helix Hub (academic-industry-government and society) in delivering a convergent holistic approach to meeting the diversity of fishery industry needs by connecting and placing fisheries centrally in a defined ecosystem of stakeholders. This includes specialist training, testing technologies, providing access to finance and fostering disruption through aquaculture accelerator initiatives such as that provided by Hatch Blue. Connecting digital Innovation Hubs trans-regionally, nationally and internationally will also help mitigate against significant risks for the fisheries and aquaculture industry including climate change, global pandemics and conflicts that can jeopardize fish and seafood production and supply chains. There is also a commensurate need to avail of digital technologies in order to increase awareness of key industry issues across the value chain, such as through social marketing. Thus, addressing key challenges by way of the global digital transformation of fishery and aquaculture industry will meet several sustainable development goals of the United Nations catered around the application of disruptive technology.

China's 13th Five-Year Plan elevated the national mandate for environmental sustainability. Chinese fisheries are characterized by full retention of high diversity catch harvested using unselective gears, creating ecological risks. Therefore, China launched pilot projects in management by Total Allowable Catch (TAC) in five coastal provinces in 2017 and 2018 to build experience with output controls. Fujian province launched an important pilot in its swimming crab fishery, the first to adopt a multispecies approach. To guide Fujian and other provinces in multispecies management, a workshop in April 2018 shared international experience. The workshop considered 13 case studies spanning a wide range of underlying scientific models and types of harvest controls. Multispecies harvest controls based on simple survey- or index-based models that aggregate trends for many species are typically operationally easier for managers and fishers. However, inadequate management can cause declines of individual species, sometimes leading to adoption of species-specific models and then species-specific harvest controls. This transition often incurs economic costs through scientific and management demands, and constraints on harvest of co-occurring species. The lessons revealed by the case studies suggest multispecies TACs might be effective in the Fujian swimming crab fishery given the modest number of species with similar and productive life history traits, and the market demand for all species. Continued experimentation with different management approaches through pilot projects can enable China to maintain progress toward sustainable fisheries goals under the 14th Five-Year Plan.

The study aims to afford a deeper knowledge on reproductive biology of Mystus bleekeri from Surma River, Bangladesh in a multidisciplinary way. Though, the species is in demand as food and ornamental fish in Bangladesh but still now comprehensive details on reproductive biology of this species is scanty. Total 600 fish samples were derived from commercial catches from July 2018 to June 2019. Periodic differences in sex ratio, size distribution, condition factor (Kn), fecundity, gonadosomatic index and gonadal maturation cycle were assessed. The results showed 384 (64%) female and 216 (36%) male with an overall sex ratio of 1.77: 1 (female: male). Mean total length (TL) and body weight (BW) of all fish studied were 14.85 ± 3.38 cm TL and 27.54 ± 15.76 g, respectively. The Kn varied with length groups, the highest (1.45 ± 0.23) and lowest (0.89 ± 0.18) values obtained in 16.0–16.9 and 10.0–10.9 cm TL groups, respectively. The highest Kn was documented in October while the lowest was in January. Monthly GSI values showed two peaks in July and November for both the sexes. The fecundity was found to vary from 1120 to 14790 eggs with average value of 4968 ± 3047 with 14.4–18.3 cm in TL and 19.97–34.7g in BW. The relationship of fecundity with TL and BW was F = 1.385TL13.405, r2 = 0.885 and F = 5.201BW4.827, r2 = 0.944. Partial behavior of spawning together with allochronic oocytes development has also been found through histology. The results of this study could be used for predicting the response of populations of fish in Surma River and/or other where to human interferences and environmental change.

MiR-202-5p is identified as the maker microRNA (miRNA) of germplasm in fish. However, the role of miR-202-5p in gonadal development is still unclear. Here we investigated the expression patterns of miR-202-5p in Japanese flounder (Paralichthys olivaceus). Real-time PCR displayed that miR-202-5p was specifically expressed in bisexual gonads, and its transcription in the testis was relatively abundant than that in the ovary. Moreover, it was gradually increased in testis from stage II to stage IV. Fluorescent in situ hybridization (FISH) illustrated that miR-202-5p was co-localized with vasa (a marker gene of germ cells) in testis, and it was predominately expressed in spermatogonia and spermatocytes, implying that miR-202-5p might participate in spermatogenesis. Considering the important role of retinoic acid (RA) on regulating meiosis during spermatogenesis, we treated Japanese flounders by injecting all-trans retinoic acid (ATRA). MiR-202-5p in testis was shown to be up-regulated, and ccnd1, a key cell cycle regulator, was found to be down-regulated after ATRA treatment. Furthermore, ccnd1 was demonstrated to be a direct regulatory target of miR-202-5p using Dual-luciferase assay. In the primary testis cell from Japanese flounder, we further confirmed that ccnd1 was down-regulated by miR-202-5p. The results suggest that miR-202-5p exerts a crucial role in gonadal development by inhibiting ccnd1 in Japanese flounder.

Spatial management of fishing effort can be used to avoid catching undesirable size classes for target species, and improve yield-per-recruit for the exploited stock. Adaptive closure management has been proposed as a means to more effectively utilise spatial management, however these management provisions often lack quantitative evaluation which constrains the information available to inform decisions. We demonstrate the use of a spatially and size structured population dynamics model to evaluate the potential impact of spatial management on a multijurisdictional fishery for a highly migratory species (eastern king prawn, Penaeus [Melicertus] plebejus). Under current conditions in the fishery, the overall effect of closures on harvest was estimated to be comparatively minor, regardless of assumptions about how effort or fisher behavior are affected by spatial management. Alternative assumptions about the movement patterns of eastern king prawn had little influence on the impact of closures on overall harvest. However, when effort was increased to historic levels similar to those observed when the closures were implemented, a much greater impact on overall harvest was observed. The approach taken and simulation outcomes are discussed in the context of spatial management for both eastern king prawn, and penaeid fisheries more broadly.

As an important seedling source, monospores closely associate with yields in nori farming. However, the molecular mechanism underlying differences in monospore production for different strains remains unknown. Comparative transcriptome analysis was performed to examine gene expression differences between the spore abundant wild-type strain (WT) and spore deficient mutant (Y1) of Pyropia chauhanii. The WT strain that produces monospores in abundance exhibited more differentially expressed genes (DEGs) in both number and higher fold-changes than the Y1 strain incapable of producing monospores, indicating that the specific regulation of genes is involved in monospore production. Three lists of DEGs were obtained between the two strains using intersection and displayed in Venn diagram: one expressed only in WT strain, another expressed only in Y1 strain, and the third shared in both strains. DEGs annotated as homologous genes of Arabidopsis thaliana in these 3 lists were curated for online functional enrichment analysis on Metascape website. Gene regulatory networks of WT were functionally enriched in the processing, proteolysis, and transport of proteins, especially within the small GTPase protein family, which might be account for the monospore production ability, whereas Y1 were functionally enriched in the metabolism of essential substance and utilization of indispensable energy, which might be account for the rapid growth of blades. We found the differentially enriched gene regulatory networks between strains might be the intrinsic mechanisms of the different monospore production traits. These findings provide novel insights into the genes and regulatory networks associated with monospore production abilities, which are essential for developing accurate breeding technologies for optimal release of monospores and increase of total nori production.