The razor clam Sinonovacula constricta is an economically important bivalve species in China, which inhabits the mudflat of intertidal and estuaries areas and frequently suffers the low salinity stress due to heavy rain events. The present study investigated the effects of hyposalinity stress (salinity 10, 5, 3, and 1) on osmoregulation and haemolymph microbiota in S. constricta after 7 days of exposure. The results showed that the survival rate of razor clams was only significantly reduced in the 1 ppt group compared to the control group (salinity 20) (P 

Cyprinid herpesvirus 2 (CyHV-2), a member of the Alloherpesviridae family belonging to the genus Cyprinivirus, was initially isolated from goldfish (Carassius auratus) and has been recently emerging as a virulent pathogen for cultured prussian carp (Carassius auratus gibelio) world-wide. In this study, a novel and effective method for concentration and quantification of live CyHV-2 virions from water was successfully established through coupling the iron flocculation with real time qPCR assay. Then, the shedding intensity of CyHV-2 in fish-tank water from artificially-challenged goldfish (25 fish/20 L) was monitored continuously for 7 days on a daily basis through quantitating viral genomic copy numbers by qPCR, and the maximum shedding level was determined to be 105 copies/L. Horizontal transmission research system was established by inoculating healthy goldfish in water spiked with serial dilution of CyHV-2 virions ranging from 107 to 103 copies/L. Our results indicated that water-borne CyHV-2 efficiently caused the infection of tested goldfish even in a concentration of 103 copies/L, and the overall transmission efficacy was not linearly correlated with the level of input virus in the fish tank. Commercial disinfectant Composite Sodium Chlorite Powder (CSCP) has been widely applied in aquaculture to control microbial infection through direct spill in the water, and its effect in inactivating the CyHV-2 infectivity remains unknown. We further determined that the EC50 of CSCP against 3.89 TCID50/mL CyHV-2 was close to 15.625 μg/mL in vitro, and application of CSCP in a level as high as 60 μg/mL (the safety concentration of CSCP for goldfish) couldn't protect goldfish from CyHV-2 challenge through immersion. Thus, the disinfectant CSCP was regarded as none-effective for blocking CyHV-2 transmission in water during epidemic. Overall, our data provided quantitative data to demonstrate the shedding intensity of CyHV-2 in water, and CSCP was shown to be not effective in blocking water-borne horizontal transmission of CyHV-2 in goldfish. The virus-concentration protocol and virus-inhibition assay established here also paved the way for evaluating more commercial disinfectants in their effects in blocking water-borne horizontal transmission of CyHV-2.

Hypoxia, a common environmental condition, can affect cell survival and physiological function by triggering oxidative stress. Akt/FoxO pathway has been proven to play a non-negligible role in the regulation of autophagy. However, the role of Akt/FoxO pathway in hypoxia-induced autophagy is unclear in fish. Therefore, in this study, grass carp hepatocyte cells (L8824) were treated by CoCl2 to simulate hypoxia, and the results showed that CoCl2 can increase the expression of Hif-1α protein at different concentrations or different treatment time. Further study found that hypoxia increased intracellular reactive oxygen species (ROS) level, and the expression of autophagy-related genes (LC3-II, pink1, beclin-1 and p62) and foxO1a/1b. The mitochondrial membrane potential (Δψm) was also depolarized, and autophagosomes were intriguingly detected by transmission electron microscope (TEM) after the treatment of hypoxia. Moreover, hypoxia inhibited Akt phosphorylation, while PI3K/Akt pathway inhibitor, LY294002 significantly up-regulated the expression of foxO1a/1b and autophagy-related genes. Additionally, silencing foxo1b also resulted in down-regulation of autophagy-related genes. It was demonstrated that hypoxia induced autophagy via Akt/FoxO1 pathway. These results will provide a new light on further understanding the role of Akt/FoxO pathway in the response to hypoxia in fish.

The study was carried out in Matiranga Upazila, Bandarban district, which is considered one of Bangladesh's major hill tract regions. The study aimed to identify present farming conditions, prospects, and problems and suitable solutions to the problems of fish farming. Different participatory rapid appraisal tools such as focus group discussion, field visits, and farmers' interviews were used to collect relevant fish farming information in the study area. The polyculture method was the most practised aquaculture method. Among the selected farms, eleven fish species were identified as culture species. The transportation cost for seeds purchased from remote areas was high (11% of total seed cost). The average transportation-related mortality of fish fry and fingerlings was 7.2% and 2.8%. Feed cost was found as the major cost (58.4%) in aquaculture. Costs and revenue for fish production per decimal varied from BDT 311 to 3528 and BDT 23 to 1268. Utilization of vacant lake, youth and women engagement, integrated aquaculture, the desire of people to engage in aquaculture, and available human resources were found as significant prospects. The major problems identified were lack of hatchery, high feed cost, lack of stakeholder linkage, lack of capital for fish farming, and lack of proper knowledge, guidelines, and consultancy for fish culture. A community-based aquaculture model was proposed to overcome the present challenges and problems in the study area. The model may help to expand aquaculture and thus improve the livelihood and socio-economic status of the people of the hilly areas of Bangladesh.

Kumamoto oysters (Crassostrea sikamea) are important marine aquaculture shellfish because of their taste and round shell shape. Due to its small size, selective breeding is required to improve its market size, but there are no reports on traits suitable for direction selection and reproductive productivity of Kumamoto oysters of different ages. In this study, path analysis and one-way ANOVA were used to explore the influential indices of oyster body weight and fecundity. The results showed that shell height was the main factor affecting the body weight of Kumamoto oysters at one-year-old and two-year-old, followed by shell length. Body weight was the main factor influencing fecundity, and shell height showed a significant correlation with fecundity. Therefore, shell height should be considered the first parameter for selection when selecting Kumamoto oysters for body weight as the direct selection target. When one-year-old and two-year-old Kumamoto oysters were selected as parents from Xiangshan Bay, hatching parameters and growth parameters of F1 generation larvae were measured. The fecundity and egg diameters were 1.72 × 106 and 46.60 ± 3.62 μm, respectively, which were significantly greater than one-aged oysters (5.86 × 105, 40.26 ± 3.52 μm). The hatching parameters (fertilized egg size, fertilization rate, and hatching rate) and larval growth performance (D-stage veliger and veliger) were similar and did not differ significantly (P > 0.05), and after metamorphosis, there was also no significant difference in shell height size at 40 days of age (P > 0.05). Therefore, there was no significant effect of age on reproduction, larval development, and the early growth of Kumamoto oysters. These results could provide a basis for parental sources and proper traits for Kumamoto oyster selection, which is beneficial to developing and utilizing this excellent germplasm resource.

Interleukin-21 (IL-21) is produced mainly by activated CD4+ T cells and promotes the proliferation, survival and differentiation of immune cells. This study characterised a high affinity binding receptor of IL-21 (IL-21 Rα) from grass carp (Ctenopharyngodon idella, Ci) and analyzed the expression of CiIL-21 and CiIL-21 Rα. It has been shown that they were modulated by PAMPs and during infection with bacterial and viral pathogens. Recombinant CiIL-21 protein produced in bacteria was active in inducing the expression of genes involved in Th responses. A monoclonal CiIL-21 antibody was generated against the rCiIL-21 and showed good reactive specificity with the rCiIL-21 proteins expressed in E. coli cells, and HEK293 T cells and the native protein from PHA-stimulated kidney leukocytes. In addition, the IL-21-producing cells detected by the CiIL-21 monoclonal antibody were found to be increased to in the kidney, spleen and hindgut after infection with Flavobacterium columnare. Our data indicate that IL-21 is involved in the regulation of immune response to bacterial and viral infection.

Ethidium bromide (EtBr) is one of the contaminants recorded in aquatic environments whose effects have been investigated; however, there is still limited knowledge about its remediation. This study examined the potential protective effects of Spirulina platensis (SP) against the effects of EtBr toxicity in the Nile tilapia (Oreochromis niloticus) fry. Fry were divided to five groups, viz., a control and four treatment groups of low-dose EtBr (10 μg/L), low-dose EtBr with SP (10 μg/L EtBr + 200 mg/L SP), high-dose EtBr (100 μg/L), and high-dose EtBr with SP (100 μg/L EtBr + 200 mg/L SP); the exposure period was 2 weeks. Low and high doses of EtBr induced alterations in some hematological, biochemical, and histopathological parameters. Necrotic hepatocytes, degenerated area, vacuolated hepatocytes, pyknotic nuclei, constricted and dilated blood sinusoids, and infiltration of inflammatory cells were observed. Lipid peroxidation concentration was not significantly different in groups exposed to low doses of EtBr and EtBr with SP, but it was increased in groups exposed to high doses of EtBr and EtBr with SP, compared with the control group. After feeding with SP, most histological and histochemical parameters restored to normal values. Therefore, SP may possess the ability to preserve the structural integrity of the hepatic and renal membranes.

Moringa oleifera is well known as a highly nutritious plant and a water purifier in fish culture. Tilapia fish has many impressive qualities making them very suitable for aquaculture. Therefore, this study aimed to evaluate the effect of supplementation of Moringa oleifera aqueous extract (MOAE) at varying concentrations (0, 100, 200, and 400 mg/kg diet for 90 days) on growth performance, hematological, and some biochemical parameters of Nile tilapia. Additionally, histological changes and immunohistochemical expression of caspase 3 in gills and livers were evaluated. Significant enhancements (P 

Tilapia culture is one of the largest sectors of global aquaculture. Among the different species of tilapia, Nile tilapia (Oreochromis niloticus) is perhaps the top cultured species. The production of Nile tilapia has been continually increasing throughout the years resulting in genetic deterioration. Several tilapia strains with better growth performance and adaptive capability to survive in different culture conditions have been developed to alleviate the crisis. Increased demand for Nile tilapia implies higher farming cost. Plant-based proteins are utilized as partial or complete fishmeal replacements to reduce feed cost. However, these proteins can adversely affect and alter growth and feed performance, carcass composition and indices, and gut and hepatic health. This review discusses the use of seven plant-based proteins: namely, soybean, copra, pea, corn, palm kernel, microalgae, and seaweed as a Nile tilapia aquafeed. Different processing methods are employed to produce several types of plant-based proteins. Processed plant-protein types, when utilized as an aquafeed ingredient, vary in its effect on the performance, hemato-immunological parameters, and gut and hepatic health of Nile tilapia. Studies have shown that Nile tilapia can effectively maximize plant-based protein diets based on the preparation method, type of plant source, amino acid supplementation, and inclusion levels of the plant proteins. These readily available crops should be considered as primary protein sources for aquaculture. Hindrances to the use of plant-based proteins as a main dietary protein are limiting amino acids, presence of anti-nutritional factors, and the competition between its demand as human food and as animal feed.

Keywords: Aquafeed industry; Alternative remedy; Functional supplements; Feeding strategies; Sustainability

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.

Time series from fisheries often contain multiple missing data. This is a severe limitation that prevents using the data for research on population dynamics, stock assessment, forecasting, and, hence, decision-making around marine resources. Several methods have been proposed to impute missing data in univariate time series. Still, their performances depend not only on the amount of missing data but also on the data structure. This study compares the performance of twelve imputation methods on the time series of marine fishery landings for six species in the Colombian Pacific Ocean. Unlike other studies, we validate the precision of the imputations in the same target time series that include missing data, using the Known Sub-Sequence Algorithm (KSSA), a novelty validation approach that simulates missing data in known sub-sequences of the target time series. The results showed that the best methods for imputation are Seasonal Decomposition with Kalman filters and Structural Models with Kalman filters fitted by maximum likelihood. Results also show that validating the imputation methods with other time series different to the target time series, leads to wrong imputation methods choices. It is noteworthy that these methods and also the validation framework are mainly suited to time series with non-random distribution of missing data, this is, missing data produced systematically in chunks or clusters with predictable frequency, which are common in marine sciences.

Biofouling is a major issue in aquaculture cages and nano materials based antifouling strategies became more prominent in recent years. Polyethylene aquaculture cage net surface which is modified with polyaniline and nano-copper oxide (CuO), reported to have biofouling resistance. Leaching of nano CuO from the net to the aquatic environment and its bioaccumulation in fish is the major concern against the technology adoption. The present study aimed to understand the accumulation of copper in fishes grown in a nano CuO treated aquaculture cage net. Studied the leaching pattern of nano CuO, biofouling inhibition and changes in strength of the cage net due to the nano CuO treatments. Fishes grown in the treated cages exhibited normal growth characteristics with no signs of abnormalities and also copper in their organs were within the prescribed standard limit. The CuO treated cage net exhibited excellent biofouling resistance and the percentage of occlusion of mesh by foulers were 56.77% more efficient than untreated cage net. Rate of nano CuO leached to the aquatic system was less than 8 μg/g·d. The fouling organism assemblage on untreated and treated net was 18 and 11 species, respectively. Major calcareous shelled foulers were absent on treated nets. The study highlighted the potential application of nano CuO treatment to control biofouling in aquaculture cages.

The present study was conducted to determine the effects of dietary phosphorus (P) levels on growth performance, body composition, liver histology and enzymatic activity, and expression of lipid metabolism-related genes in spotted seabass (Lateolabrax maculatus). Seven diets were prepared to contain available P levels of 0.48% (the control group), 0.69%, 0.89%, 1.10%, 1.28%, 1.51% and 1.77% and feed fish (4.26 ± 0.03 g) to satiety twice daily for 10 weeks. Significantly higher weight gain and specific growth rate were recorded at P levels of 0.69%–1.51% compared to the control group. Feed conversion ratio decreased with increasing P levels up to 0.89% and increased thereafter. The lowest liver lipid content, viscerosomatic index and lipid content of whole-body were obtained in the 0.89%-P group among dietary treatments. P and calcium (Ca) contents in whole body were increased, while liver triglyceride and cholesterol contents were decreased with increasing dietary P levels from 0.48% to 1.77%. The highest activity of hepatic lipase was recorded in the 1.10%-P group among dietary treatments. Compared to the control group, 1.10% P enhanced the proportion of HUFA and reduced the proportion of SFA and MUFA. The histological observations showed that P deficiency (0.48%) led to the vacuolization of hepatocytes and increased number of lipid droplets. Meanwhile, overall liver tissue structure was improved when P level increased to 1.28%. Compared to the control group, expression of lipid metabolism-related genes such as FAS, ACC-2 and SREBP-1 was decreased at 0.89%–1.10% P group while an opposite trend was observed in the expression of PPARa2 and CPT-1 genes. The current study showed that 0.89% dietary P levels could promote growth performance of spotted seabass and reduce lipid accumulation in the liver. A broken-line regression analysis based on weight gain showed that the optimum dietary P level (available P) for juvenile spotted seabass reared in freshwater was 0.72%.

Gastrin (gas) is a peptide hormone that stimulates gastric acid secretion by gastric parietal cells and stimulates gastric motility. The cholecystokinin B receptor (cckbr) can act as a receptor for gastrin, conveying regulatory information on gastrin, but there are fewer studies on its function in fish. The Lateolabrax maculatus is one of the marine aquaculture species in China, it widely distribute in coastal areas. In the study, we cloned the genes of Lateolabrax maculatus gastrin (Lm-gas) and Lateolabrax maculatus cholecystokinin B receptor (Lm-cckbr). The results showed that the full-length gene of Lm-gas is 638bp and the carboxy-terminal conserved domain (DFGRR) is the core functional domain of gastrin protein. The Lm-cckbr gene has a total nucleotide sequence of 2066 bp, and the open reading frame encodes a total of 453 amino acids. The result of protein sequence alignment showed that the similarity between Lm-cckbr protein and other different species was 50.11%–89.67%. The PCR results showed that Lm-gas and Lm-cckbr were expressed in brain and stomach. Further localization by immunehistochemical staining showed that Lm-gas protein was located in the mucosal layer of the gastric wall, but the expression signal was weak in the brain. Hunger causeed a significant decrease in these two genes. The results provided basic research data for further study on the function of Lm-gas and its recepter Lm-cckbr in the in the central nervous system and digestive system of Lateolabrax maculatus.

Tunas are among the most economically important fish species and play critical roles in food composition and nutrition of humans. As apex predators, they also keep the marine ecosystem healthy and balanced. Both natural and human factors influence the status of this important marine resource and their habitats. There is a large cadre of studies on how tunas are of great significance to the exploitation and management of their fisheries, yet there are few summaries of this research. We aimed to quantitatively and qualitatively synthesize the global knowledge structure and emerging trends in tuna research using bibliometric software. References with "Tuna", "Katsuwonus", or "Thunnus" as the subject in the Web of Science Core Collection Database from 1995 to 2019 were visually analyzed using CiteSpace. Publication rate and output, active countries, institutions, authors, and co-cited references were performed. Results suggested that the number of international tuna research papers increased significantly between 2000 and 2010, as a considerable number of high-impact articles emerged during this period. Researchers paid more attention to 19 main topics during this period, notably "overfishing", "bycatch", "climate change", "marine pollution", and "fish management", which all posed potential risks and challenges to tuna survival. Future research should emphasize resolving these challenges and building international cooperation for the proper management of tuna populations.

The catfishes are a group of economically important freshwater fish in China, which in recent years have suffered heavy losses as a result of bacterial outbreaks. In this study, we examined the diversity of the microbiome of infected skin mucus of yellow catfish (Pelteobagrus fulvidraco) and channel catfish (Ictalurus punctatus) and analyzed the bacterial pathogens. We found several common pathogenic bacteria, such as Aeromonas spp., Vibrio spp., Moraxella spp. and Proteus spp. present in both fish species, but with significantly different bacterial community structures. We isolated and cultured Aeromonas veronii and Proteus mirabilis and validated their infectivity in zebrafish (Danio rerio) and yellow catfish. Intraperitoneal injection of either bacteria into zebrafish, but not immersion, caused 100% mortality and ovary fragmentation. Yellow catfish was more sensitive than zebrafish with 100% mortality in the immersion challenges with A. veronii or P. mirabilis, and with a higher abundance of A. veronii in the P. mirabilis-challenged group compared to control. To our knowledge, this is the first study on the pathogenicity of P. mirabilis in yellow catfish, and the results will help to develop effective strategies for the disease prevention and control in catfish farming.

IGS is abundant in polymorphism, which is widely used in the analysis of intraspecific genetic diversity and phylogenetic relationships among geographical populations. In this study, the 45S rDNA repeat unit of Saccharina japonica was obtained for the first time by BAC clone sequencing. The total length of the 45S rDNA repeat unit of S. japonica was 8 995 bp, including 5 420 bp of 18S-5.8S–25S rDNA, and 3 575 bp of IGS (Intergenic Spacer), with the GC content of 51.4 %. The IGS was composed of a 465 bp of 3â€⊃2;-outer transcribed spacer (ETS), an 874 bp 5â€⊃2;-ETS, and a 2 236 bp non-transcribed spacer (NTS), with the GC content of 50.1 %. Fiber-FISH (fiber-fluorescence in situ hybridization) analysis of the distribution of 45S rDNA repeat units on the bacterial artificial chromosome illustrated that each fiber had at least five continuously moniliform hybridization signal points. This study provided a new candidate molecular marker for detecting intraspecific polymorphisms of S. japonica. In addition, the successful fiber-FISH analysis of the 45S rDNA on BAC molecule would contribute to the construction of the physical map and map-based cloning of this kelp.

The large yellow croaker (Larimichthys crocea) is an economically important marine species with the highest annual production among the farmed marine fishes in China. However, the aquaculture industry of this species is suffering from severe problems that include weakened disease resistance, decreased growth rate, and reduced meat quality due to frequent inbreeding. Genome editing, which has a huge potential for solving those problems by introducing favorable genetic changes, is not yet available for the large yellow croaker. Here, we pioneered the techniques of embryo microinjection and genome editing using the CRISPR/Cas9 system in this species. Recombinant plasmids encoding green fluorescent protein (GFP) were introduced into the fertilized eggs of L. crocea by microinjection before the chorion had hardened. A high survival rate (40%) and GFP-positive larvae rate (81.8%) were achieved, indicating that the microinjection technique in L. crocea was successfully established. On this basis, Cas9 mRNA and sgRNA targeting the tyrosinase a gene in L. crocea (Lc-tyra) were co-injected into fertilized eggs of L. crocea. Mutant individuals with insertion and deletion mutations of Lc-tyra were detected. These results indicated that the CRISPR/Cas9-based genome editing technology established herein could efficiently introduce mutations at a specific site in the L. crocea genome. This method provides the potential for genetic improvement and functional genomic study in this species. This is the first report on effective CRISPR/Cas9-based genome editing in L. crocea.

Seawater (SW)-acclimated Nile tilapia, Oreochromis niloticus, reared under a salinity 30 environment had lower growth and survival than the freshwater (FW)-acclimated fish. It was hypothesized that cells of the SW-acclimated fish had not been able to synthesize an adequate level of a compatible osmolyte, myo-inositol (MI), in adjusting to the salinity 30 environment. In this study, MI supplements, at 250, 500, and 750 mg/kg pellets, were provided to the fish through top-dressing. After the 30-day feeding trial, the following parameters were determined: final body weights; survival; biomass increase; feed conversion ratio (FCR); plasma osmolality and ions; and two transcripts in the gills mips250 and mipa1 encoding enzymes responsible for MI biosynthesis. The SW-acclimated O. niloticus receiving 500-mg MI supplement had significantly higher survival, biomass increase, and lower FCR than those of the SW-acclimated fish receiving no supplement. At 500-mg MI supplemental level, the increasing values of plasma osmolality and Na+ observed in SW-acclimated fish were significantly attenuated. The transcript mipa1, but not mips250, was markedly up-regulated in the SW-acclimated O. niloticus, compared with that of the FW-acclimated fish. Again, MI at 500-mg supplement attenuated the up-regulation significantly. This study suggests that MI supplement at the optimum level enhanced the performance of SW-acclimated O. niloticus, and through yet unknown mechanisms, attenuated some of their physiological responses to the osmotic stress.

White spot syndrome virus (WSSV), the causative agent of White spot disease (WSD), not only caused huge economic losses, but also greatly limited the development of crustacean breeding industry. Chinese herbs are widely used and have great application potential in antiviral research. In thist study, the antiviral effects of 11 Chinese herb extracts were evaluated in Procambarus clarkii (crayfish) model of WSSV infection, among which Cimicifuga foetida L. extract showed the highest inhibition rate (88.22%) against WSSV replication. On this basis, the anti-WSSV effect of Isoferulic acid (IFA), a major bioactive component of Cimicifuga foetida L., was further investigated. The results showed that IFA significantly inhibited WSSV replication (96.57%, 50 mg/kg) in a dose-dependent manner and significantly improved the survival of WSSV-challenged crayfish. IFA had the potential preventive and therapeutic effect against WSSV infection, and the preventive effect was better than the therapeutic effect. Mechanistically, IFA suppressed the expression of the immediate early gene ie1, the DNA polymerase gene DNApol and envelope protein gene Vp28 to inhibit WSSV replication, activated TLR, CTL and ProPo genes expression to block ie1 transcription, and suppressed BAF, STAT, NF-κb and Crustin 1 genes expression to elevate innate immunity against WSSV infection. Besides, IFA upregulated the cMnSOD, mMnSOD, CAT and GST genes expression, and downregulated the COX-1 and COX-2 genes expression to balance the oxidative stress and inflammatory damage caused by WSSV infection. This study provides a theoretical basis and meaningful reference for the development of IFA as a highly effective and practical anti-WSSV drug.

Among vertebrate species, fishes are considered to be the most developmentally diverse taxa exhibiting remarkable gonadal plasticity with capacity of sex reversal. Sex determination in teleost fishes is governed via a complex regulatory network involving multiple genetic, environmental (temperature, population density, pH), social interaction/stress factors. Piscine germ-line originates as Primordial germ cells (PGC) from cleavage blastomeres/endoderm and gets specified by maternal inheritance of Vasa, Nanos, Tdrds, Dnd, Dazl etc and subsequently migrates to reach the embryonic gonadal primordium. Post-hatching, mitotically active germ cells (Gc) continue to proliferate via two distinct pathways-firstly, stem cell-like mode followed by meiosis-committed cystic division. In Japanese rice fish medaka, Oryzias latipes sex gets determined on the chromosomal basis, where XY becomes a male because of testicular Dmy transcription and XX develops as female owing to Gc restricted Foxl3 expression. Sex specific germ-line stem cell systems also have been found in adult O. latipes. Intriguingly in teleost fishes, the developmental fate of transplanted Gc do not depend on the sex of the donor rather solely relies upon the sex of the recipient. Furthermore, sexually mature piscine gonads remain developmentally plastic showing extensive responsiveness towards sex steroids. The critical regulation of gonadal differentiation is directed by female specific 17Î⊃2;-estradiol (E2) and bio-active male androgen 11-keto-testosretone (11-kT). Various transcription factors (TFs) e.g.- Dmrt1, DAX1, Ad4BP/SF-1, Foxl2 regulate the bio-conversion rate of testosterone (T) to either E2 or 11-kT. Similarly, multiple endocrine factors (EFs) e.g.- LH, FSH, E2, 11-kT and growth factors (GFs) e.g- AMH, GSDF, IGF-1/3, GDF-9/BMP-15 critically induce Gc differentiation to regulate the gametogenic output. In this article we have precisely discussed the endocrine regulation of Gc development during gonadal maturation of teleosts.

Gonadal soma-derived factor (Gsdf) is a member of the transforming growth factor beta (TGF-Î⊃2;) superfamily and a teleost-specific gene. Early studies suggested that Gsdf promotes spermatogonial proliferation; however recent reports have shed light on its role in sex differentiation based on expression profiles and gain- and loss-of-function studies. This paper discusses the involvement of Gsdf in gonadal sex differentiation and sex changes in teleosts.

Pampus argenteus and Pampus chinensis form the high-value demersal Pomfret fishery of Bangladesh. But, due to a monotonic decline in catches over the last five years, it is essential to explore the current stock status concerning the removal rate to ensure the sustainability of this fishery. Therefore, given the reliability and minimal data requirements, this study employed an extended Bayesian State-Space Surplus Production Model, JABBA (Just Another Bayesian Biomass Assessment), to assess the stock rigorously. The results revealed that the stock biomass of the Pomfret fishery in the final year of the time series is significantly lower than BMSY, the biomass required to produce MSY. Consequently, this study recommends a yearly catch limit (TAC) of 10,000 metric tons to prevent further depletion of the stock biomass. Furthermore, to avoid growth overfishing by allowing all immature fishes to reproduce at least once before being caught, this study also calculated the optimum length (Lopt) for catch for both species at which biologically maximum yield and revenue can be obtained. The estimated Lopt is 25 cm for P. argenteus and 30 cm for P. chinensis, and not to capture fishes with lengths lower than these limits, this study further calculated the minimum mesh size limits for gill and set bag nets is 7.5 cm. Though the mesh size regulation was estimated using length-based reference points derived from an empirical equation, this regulation can be used as an associate reference point when TAC is applied to assure the sustainability of this fishery.

Miiuy croaker, Miichthys miiuy is an ecologically important teleost species which is widely distributed in southeast coast of China. In this study, we present a chromosomal-scale genome assembly of the miiuy croaker which is an important Sciaenidae fish and economical species. We adopted Oxford Nanopore and Hi-C sequencing techniques to achieve an assembly with high accuracy and completeness. The investigation of genome characteristic and functional features may provide insights into the study of phylogenetic diversity of miiuy croaker. This study can also be beneficial to improve molecular assisted breeding techniques. Moreover, it can be a great resource to better conduct further study of other sciaenids.

This review summarizes the current knowledge on immune defence activities of the European sea bass Dicentrarchus labrax by reporting the consistent amount of work done on this economically-important species. A draft genome sequence is available for this species, together with whole transcriptomes from lymphoid and non-lymphoid tissues. Available full-length coding sequences of many immunoregulatory and immune-related genes allow for targeted quantitative PCR analysis, nowadays needed for -omics data verification, ex vivo and in vitro. The first anti-T cells monoclonal antibody teleost-wise was obtained in sea bass, followed by several monoclonal and polyclonal markers of lymphocyte populations, namely T cells (pan-T, CD3ε, TcRÎ⊃3;, CD45), and B cells (IgM, IgT, IgD). The combined use of molecular and biochemical tools enabled investigations on innate and acquired immune responses of sea bass in unstimulated/stimulated fish, along the development and under variable environmental conditions and food regimes. An overview of sea bass viral and bacterial pathogens and available vaccines against these microorganisms is also provided. The knowledge accumulated in the past 25 years validates the European sea bass as a reference marine model in the field of fish immunology.

Intensive aquaculture-induced oxidative stress is detrimental to fish health and yield. Medicinal plants show promise as natural health boosters and antioxidants in the aquaculture industry. Therefore, this work investigated the effects of turmeric aqueous extract (TAE) on the growth performance, antioxidant status, and hydrogen peroxide (H2O2)-induced oxidative stress in spotted seabass (Lateolabrax maculatus). Fish were fed diets supplemented with 0 (Con), 2 (TAE2), or 4 (TAE4) g/kg TAE for eight weeks, then were injected with H2O2. The results showed that dietary supplementation of TAE did not affect fish growth, feed utilization, or body composition. TAE treatment increased liver antioxidant enzyme activities and decreased liver malondialdehyde content and serum levels of glutamate oxalate transaminase, glutamate pyruvate transaminase, and lactate dehydrogenase. Furthermore, the increases in mortality, liver malondialdehyde content, and serum biomarkers of liver injury in the H2O2-treated fish were inhibited as a consequence of the TAE treatment. In addition, TAE treatment activated the Nrf2/Keap1 pathway in the liver, supported by the up-regulated expression of nrf2, ho-1, and gclc, and down-regulated keap1 expression. Overall, dietary incorporation of TAE protected against H2O2-induced oxidative stress in spotted seabass probably by enhancing antioxidant capacity through the Nrf2/Keap1 pathway.

A 56-day feeding period was performed to investigate the possible impacts of dietary nano curcumin (0, 50, 100, 150, and 200 ppm) on the growth, nutrient utilization, non-specific immune parameters, antioxidants in Nile tilapia under chronic low temperature (21.02 ± 0.11 °C). Fishes (n = 225; Initial weight = 4.39 ± 0.08 g/fish) were randomly stocked at 15 fish/tank for five experimental groups in triplicates. Under low-temperature circumstances, dietary curcumin in nano form showed no notable alteration in growth variable, nutrient efficiency, digestive enzymes efficiency, biometric indices, survival rates, and hematological components. Meanwhile, the serum of fishes with nano curcumin diets under low-temperature stress displayed higher total protein as well as lower glucose, cortisol, and total cholesterol compared with the control group. Moreover, fish fed nano curcumin diets displayed higher lysozyme and bactericidal activities compared to the control group and the best performance was found at dietary nano curcumin level of ≥100 ppm. Also, groups fed the basal diet demonstrated the poorest antioxidant capacity, and the best superoxide dismutase (SOD) and glutathione peroxidase (GPx) existed in fish with nano curcumin diets while the best catalase (CAT) efficiency occurred at higher nano curcumin levels ≥100 ppm. In addition, higher counts of intestinal microbiota in terms of total bacterial count (TBC), total yeast and molds count (TYMC), and coliform were noticed in fish consumed the basal diet compared to groups fed on nano curcumin diets. In conclusion, incorporating nano curcumin at a level of ≥100 mg/kg diet (particularly at 150 mg/kg) improved a non-specific immune response, antioxidant, and healthier gastrointestinal microbiota in Nile tilapia under chronic low-temperature stress.

Insects, particularly black soldier fly larvae (BSFM), Hermetia illucens, have been regarded as promising protein and lipid sources in animal feed, including fish. Digestibility is the key factor that affects nutrient utilization, feeding physiology and efficiency. In the present work, the effect of BSFM on the digestibility of red hybrid tilapia (RHT) compared to fish meal (FM) was ultimately unveiled. A 56-day growth trial was performed with 60 RHT (∼30 g) randomly distributed into six tanks and fed two experimental diets containing FM as a reference diet and BSFM as a test diet. In addition, faeces were collected to determine their chromium concentration and proximate composition. The apparent digestibility coefficient (ADC) of dry matter, crude protein and energy in the BSFM diet were observed to be significantly higher than those in the FM diet. Besides, the growth performance of fish fed with the BSFM diet exhibited significantly higher (P 

Orange spotted grouper (Epinephelus coioides) is an important mariculture fish, and genomic breeding of this grouper species has been hindered due to lack of efficient genotyping tools. Here, we developed a single nucleotide polymorphism (SNP) genotyping technology based on multiplex PCR enrichment capture sequencing, which mainly aims at target area for high-throughput sequencing, and 741 SNPs were designed for genomic selection (GS) of growth and ammonia tolerance traits at the same time. The multiplex PCR enrichment capture sequencing assay showed that the genotyping efficiency was more than 99% in the orange-spotted grouper and the predictive accuracy of body weight and ammonia tolerance traits was 82% and 96%, respectively. More importantly, the average identity of the sequences with these SNPs aligned to the genomes of giant grouper (E. lanceolatus) and brown-marbled grouper (E. fuscoguttatus) were both over 96%. Test data showed that the SNP genotyping efficiency was more than 94% in both giant grouper and brown-marbled grouper. In summary, these results indicated that the development of SNP loci and genotyping approach based on the multiple PCR enrichment capture sequencing are suitable for GS of growth and ammonia tolerance traits in various grouper species, and it would provide technical support for practical grouper breeding.

Numerical simulation is an important method for calculating the hydrodynamic performance of otter boards used in sea floor trawling. Although such simulations have been explored in prior studies, the effects of the proximity of the otter boards to the seafloor and the plume of upward-drawn sediment during bottom trawling have largely been ignored. In this study, we assessed these factors. The results show that within the angles of attack used during normal operations, the effect of the seafloor bottom boundary of the flow field on the hydrodynamic performance of an otter board is obvious. We found that when the ratio of the distance between the bottom of an otter board and the surface boundary of the flow field to the chord length of the board exceeds 0.4, the influence of the bottom boundary of the flow field on the hydrodynamic performance of the board is negligible. For values of less than 0.4, the seafloor bottom boundary has an increasingly obvious impact on the hydrodynamic performance as this ratio decreases. We also found that the turbid plume of ocean floor sediment raised during bottom trawling has an obvious effect on the lift and resistance coefficients of an otter board at high angles of attack. At low angles, this effect on the lift-to-drag ratio is reversed and less obvious. The simulation results show that the optimal lift-to-drag ratio decreases with an increase in the sediment concentration; however, beyond a certain threshold, an increasing concentration of sediments was not found to have an obvious impact on the lift-to-drag ratio.

Fishing with artificial light has become one of the most advanced, efficient, and common methods for the night-time purse seining in Vietnam. This study evaluated the radiation spectrum, CIE chromaticity coordinates, correlated color temperature (CCT), catch rate, fuel consumption, and CO2 emissions when using Light emitting diode (LED) lamps (0.196 kW) in comparison with the use of metal halide (MH) lights (1 kW) in the offshore purse seine fishery in Quang Tri province, Vietnam. The fishing efficiency of the purse seine fishing boats using LED lamps has increased 1.58 times in catch rate than MH lights, although the energy consumption of LED lamp is 4 times smaller. Fuel consumption of boats per trip using LED lamps was one third of that using MH lights. The use of LED reduced the radiation spectrum, especially the intense UV radiation which negatively affects the health of fishermen. This study also showed the potential of CO2 emission reduction up to 1.09 tons of CO2 per trip per boat from the use of LED lamps in the offshore purse seine fishing boats.

Transport is an essential part of the aquaculture and research of the main freshwater aquaculture crayfish Procambarus clarkii in China. However, transport is often accompanied by a low survival rate. Assessing the physiological state of P. clarkii before and after transport may discover the cause of this high mortality rate. In this study, ice-cold and exposed-to-air transport methods were compared using an array of parameters, including relative expression level of heat shock protein 70 (HSP70), content of serum glucose and cortisol, immune parameters (enzyme and immune-related genes), and white spot syndrome virus (WSSV) concentration were investigated to understand the physiological state of P. clarkii before and after transport, as well as the cause of dying crayfish on days 5 and 7 after transport stress. Histological sections of hepatopancreas, gills, and intestines reflected pathological changes. The survival rate of crayfish with ice-cold transport was significantly higher than that with exposed-to-air transport, and mortality peaked at 3–9 days after transport stress. A prolonged response to oxidative stress and short-term immunosuppression was present after transport, and the trend of the WSSV concentration in the hepatopancreas was similar to the mortality rate of P. clarkii. The contents of serum glucose and cortisol, antioxidant enzymes and immune-related indexes, and the concentration of WSSV in hepatopancreas of dying crayfish were significantly higher than those of vibrant crayfish on the 5th and 7th days after transport. The hepatopancreas, intestines, and gills of dying crayfish had varying degrees of damage, and the hepatopancreas and intestines were severely damaged. The results suggested that the death of P. clarkii after transport stress is caused by oxidative stress, the imbalance of reactive oxygen species regulation, and decreased WSSV resistance, which eventually led to irreversible tissue damage. The increase of WSSV in the body of crayfish might be the direct cause of crayfish death.

Occurrence of biogenic amines in fresh fish and fishery products constitute a significant safety concern. Ingestion of histamine is identified as the causative agent of several food poisoning incidences on an annual basis. In addition, cadaverine, putrescine and tyramine have been recognized as potentiators of histamine poisoning. Accumulation of biogenic amines in fresh fish and fishery products has been mainly attributed to growth of bacteria possessing amino acid decarboxylase activity, which is facilitated by lack of hygienic conditions and strict temperature control during their storage. To this end, the effectiveness of traditional and modern approaches to control biogenic amine accumulation has been in the epicenter of intensive study. The aim of the present review article is to update and integrate current knowledge regarding the biogenic amine content of fresh fish and fishery products as well as the capacity of traditional and emerging control strategies.

The objective of this study was to evaluate the effect of modified atmosphere packaging (MAP) on fish skin, gills and intestines bacterial microbiome. Whole gilthead seabream was packed aerobically or under modified atmospheres (60% CO2, 30% N2, 10% O2) and stored isothermally at 0 °C. Next Generation Sequencing (NGS) analysis was applied for the characterization of fish microbiome on fish skin, gills, and intestines initially (time of packaging, 1 day after harvesting) and after 10 days of isothermal storage at 0 °C. NGS results indicated statistically significant differences in families’ richness and diversity in the tested fish tissues between aerobic and MAP packaging during storage at 0 °C. The most persistent bacteria were Proteobacteria for both packaging types. For fish skin microbiota, the initially prevailing families were Comamonadaceae, Enterobacteriaceae and Moraxellaceae while in the intestines Comamonadaceae, Anaplasmataceae, Bacillaceae and Enterobacteriaceae were the dominant bacteria. At the end of storage period, the fish microbiota was dominated by psychotropic and psychrophilic families (Pseudoalteromonadaceae, Psychromonadaceae, and Shewanellaceae), while families such as Comamonadaceae were persistent under MAP conditions. By 8 days of fish storage at 0 °C, ΜΑΡ samples exhibited higher sensory scorings than the respective aerobically stored fish, indicating better retention of fish freshness and fish quality attributes under MAP. Based on the results of the study, MAP modified significantly the microbiological status and extended the shelf life of fish. NGS was a powerful tool that provided a more complete assessment compared to a culture-based analysis.

There has been an increasing emphasis on reducing the environmental impacts of penaeid trawls by modifying their anterior sections. In one Australian estuary, this approach has culminated in a new generic trawl comprising a slightly smaller mesh size, and steeper and shorter side panels than traditional trawls, combined with a top panel extending forwards of the bottom panel (termed ‘lead-ahead’) and no headline floats. This study sought to investigate if an additional simple, cumulative modification (tickler chain) might help promote adoption of the new trawl, via improved penaeid catches. Six volunteer fishers towing pairs of either the traditional or new trawls in double rigs were asked if an observer could accompany fishing trips, and alternately attach a light tickler chain (∼3 kg) anterior to the ground gear of one trawl. Regardless of the trawl design, the tickler chains significantly increased the catch weights of penaeids, but relatively more so in the new trawls (by 1.11 × vs 1.08 × ). The tickler chains also significantly increased the number and weight of total bycatch in the traditional trawls (by up to 1.22 × ), but not in the new trawls—although there were variable species-specific effects. In terms of total effects, the data support using tickler chains to increase the efficiency of the new trawls and their cumulative benefits, and could be promoted to facilitate broader inter- and intra-fleet adoption.

An 8-week feeding trial investigated the optimum dietary vitamin K3 requirements of largemouth bass. A total of 600 healthy fish (12.96 ± 0.07 g) were fed diets containing varying levels of vitamin K3 at 0.78 (K0), 5.80 (K5), 10.82 (K10), 15.84 (K15), and 20.85 (K20) mg/kg with four replicates per level. Results showed that dietary vitamin K3 enhanced growth, with weight gain rate and specific growth rate in K15 trials significantly higher than K0 trials (P  0.05). However, the supplementation of vitamin K3 significantly contributed to calcium accumulation in muscle tissues and vertebrae (P  0.05). The antioxidant capacity was improved with the addition of vitamin K3, which was inconsistent with the changes in malondialdehyde and MK-4 (a form of menaquinone) within liver and serum, suggesting that the toxicity of excessive artificial vitamin K3 may account for this difference. Using regression analysis, the appropriate dietary vitamin K3 levels within a largemouth bass diet was determined to be in the range of 9.93–15.22 mg/kg, which will provide a reference for the preparation of vitamin premix and artificial diet for largemouth bass.