Abstract:Gill is not only an important respiratory organ of teleost, but also a structural foundation for ion exchange, acid-base regulation and nitrogenous waste excretion of fish. Importantly, it is one of peripheral mucosal immune organs of fish. The mucosal immune response of gill is the hot research topic. In this paper, we firstly analyzed the structure and features of gill. Then, we summarized the gene expressions and molecular functions of molecules involved in the innate immunity and adaptive immunity in gill. Antimicrobial peptides (AMPs), including NK-lysins, β-defensins, piscidins and hepcidins, are important innate immune molecules in fish gill, which can directly inhibit or kill a variety of pathogenic microorganisms. Fish type I interferon (IFN) and type II IFN in gill can be up-regulated by bacteria, viruses and parasites, indicating their important roles in gill immune response against pathogens. The interleukin (IL)-1, IL-2, IL-6, IL-10, IL-17 and heterodimer ILs are mainly expressed in gill, but possess distinct time-dependent patterns following pathogen invasion. Toll-like receptors (TLRs) are important pattern recognition receptors of fish. The TLR1-4, TLR7, TLR9, TLR12, TLR18, TLR21-22 are highly expressed in gill and up-regulated by pathogens. Fish possess similar complement molecules as mammals, and these complement molecules are highly expressed in gill and significantly up-regulated during pathogen invasion. T-cell receptors (TCRs) and immunoglobulins are the main adaptive immune molecules in gill. Similar to mammals, fish have four types of TCRs (TCRα, TCRβ, TCRγ and TCRδ). These four TCRs are induced by bacteria or parasites in gill. Three types of immunoglobulins (IgM, IgD, and IgZ/T) exist in gill. IgM and IgD in gill are involved in the recognition and binding of specific antigens, while IgZ/T is responsible for the mucosal immune response. Lastly, the effects of chemical factors (such as heavy metals, pesticides), biotic factor (such as bacteria, virus, parasites), nutriments, and vaccines on the structures of gill were analyzed. Heavy metals (such as copper, arsenic, mercury), pesticides, and pathogens invasion can destroy the normal structure of gills. Nutriments and vaccines have positive regulatory effects on the immune function of fish gill. This study may provide guidance for further study of the functional role and response mechanism of gill in fish mucosal immune response, and provide theoretical basis for the research and development of immune prevention and control strategies for pathogenic diseases of teleost.

Abstract:Red tilapia (Oreochromis spp.) is a valuable fish due to its uniform red skin, the absence of black peritoneum, fast growth and adaptability to any culture system, and it has a huge market in many parts of the world, such as China, Malaysia and Thailand. However, the skin color differentiation in genetic breeding and skin color variation (whole pink to black) during the overwintering period are the main problems limiting the development of commercial red tilapia culture. MicroRNAs (miRNAs) play important roles in biological processes by regulating specific gene expression. Limited microRNA (miRNA) information is available on skin color variation in fish so far. In this study, a high-throughput Illumina sequencing of sRNAs was conducted on two color varieties of red tilapia during the overwintering. The two skin color varieties were normal whole pink (WP) and pink to black color (PB). A mean of 14 748 358 and 12 981 453 raw reads from WP and PB groups, respectively, corresponded to 12 190 544 and 11 891 890 clean reads. We summarized the length distribution of all samples and found that the peak length was 22 nt. A total of 669 mature miRNAs were identified, including 337 known miRNAs and 332 novel miRNAs. Moreover, we identified 26 significant differential expression miRNAs in PB compared with WP group, including 11 up-regulated miRNAs and 15 down-regulated miRNAs. And 12 known miRNAs, i.e. miR-203a, miR-200a, miR-200b, miR-725, miR-10544, miR-204a, miR-429b, miR-129, miR-10581c, miR-10581a, miR-217 and miR-499 may play an important role in the skin color variation of red tilapia during overwintering. Enrichment analysis found many pathways related to metabolic and skin color regulation including oocyte meiosis, Wnt, Notch, calcium, Apelin signaling pathway and so on. These results would provide a basis for exploring the mechanism of skin color variation of red tilapia during overwintering.

Abstract:To understand the effect of hypoxia on Chinese mitten crab Eriocheir sinensis, the transcriptomic profiles of hemocytes in the hypoxia (1.5±0.5) mg/L and the normoxia groups [(6.0±0.5) mg/L of DO] were obtained using Nova Seq 6000. Firstly, by splicing, annotating and screening the original data, in total, 128614 transcripts were obtained with an average length of 2634 bp. Meanwhile, using a 1.2-fold change (P<0.05) in expression as a physiologically significant benchmark. A total of 1687 differentially expressed genes were identified, including 899 up-regulated and 788 down-regulated genes. GO and KEGG analysis showed that many processes or pathways are involved in the crab against hypoxia stress, such as tricarboxylic acid cycle (TCA cycle), glycolysis, ECM-receptor interaction, gap junction, cell apoptosis, prophenoloxidase system (proPO), etc. Finally, ten selected genes from these processes or pathways were verified by qRT-PCR analysis. The results showed 6 up-regulated genes (integrin-β1, extracellular Cu/Zn-superoxide dismutase, phosphoinositide-3 kinase, phosphoglycerate mutase 2, PDGF/VEGF-related factor 1, and relish) and 4 down-regulated genes (innexin-7, 90 ku heat shock, mitochondrial ATP synthase subunit α, and aspartate aminotransferase) corresponded with the transcriptome analysis. This study preliminarily elucidated the molecular mechanism of hemolymph response to short-time hypoxic stress, and provided some valuable information for the further analysis of the mechanism under hypoxia stress in crabs.

Abstract:Penaeus monodon (African group) accommodates industrial aquaculture and has promising market prospects. But the deterioration of water quality causes frequent occurrence of diseases. Nitrite is a common pollutant, and the experiment was conducted to observe its effect on oxidative stress, energy metabolism and osmotic regulation. Four gradients of nitrite concentrations (0.1, 5, 10 and 15 mg/L) were set for 4 groups, and three parallels were set for each group. After the acute stress experiment for 72 hours, enzyme activities or substance content were assayed. ① As for oxidative stress factors in gill, activities of SOD, GSH-Px, CAT and NOS increased initially and decreased subsequently. At 24 h, the activities of SOD, GSH-Px and NOS reached maximum. The activities of SOD and GSH-Px in the 10 mg/L group and NOS activity in 15 mg/L group were significantly higher than other groups. On the contrary, MDA content in stress groups was the lowest at 24 h, and the 10 mg/L group was significantly lower than other groups. At 48 h, CAT activity reached the maximum, and the CAT activity of 10 mg/L group was significantly higher than other groups. At 72 h, the NO content reached maximum, and 15 mg/L group was significantly higher than other groups. ②The indicator of serum energy metabolism, LPS, increased at first and decreased then. The activities of HK, PFK, PK or TG content, decreased obviously during stress process. At 48 h, LPS activity reached maximum, and 10 mg/L group was significantly higher than other groups. At 72 h, the activities of HK, PFK, PK and TG content reached minimum, 15 mg/L group were significantly lower than those of other groups. ③The gill osmotic regulation parameters, Na⁺, K⁺ -ATPase, decreased during whole process. At 72 h, the Na⁺, K⁺ -ATPase activity reached the minimum, and the 15 mg/L stress group was significantly lower than other groups. Results showed that P. monodon could improve antioxidant capacity, enhance lipid absorption and utilization, and disturb osmotic balance when exposed to acute nitrite stress. But only within certain concentration or time limits can it come into play. The result will provide data support for the further exploration of molecular mechanisms and also provide theory support for healthy prawn farming.

Abstract:Rhopilema esculenta is a common jellyfish with high economic value in the coastal areas of China. In order to explore the effects of changes in environmental factors on oxygen consumption rate (OCR) and ammonia excretion rate (AER), this study was conducted through indoor culture to analyze the change characteristics of OCR and AER of juvenile and adult R. esculenta under different pH, salinity and temperature conditions. The results showed that the diameter and dry weight of R. esculenta umbrella can be expressed by W= 0.002 2 e^{0.124 8D} and R²=0.972 4. The changes of the AER and OCR of juvenile and adult R. esculenta were significant affected by pH, salinity and temperature. The AER and OCR of juvenile and adult R. esculenta increased first and then decreased with the increase of pH. Juvenile and adult R. esculenta reached their two max metabolic rates at pH=7 and pH=7.5 respectively, while the frequency of pulsations was the highest. The AER and OCR of juvenile and adult R. esculenta showed a trend of increasing first and then decreasing with the increase in salinity, reaching their maximum when the salinity was 25 and 20 respectively, which had the strongest contraction force when the salinity was 20. The OCR of R. esculenta with different sizes increased with increasing temperature; while AER increased first and then decreased, reaching its maximum at 25 ℃. R. esculenta moved and fed at the fastest speed when the temperature was 21 ℃, and almost stopped moving when the temperature was lower than 3 ℃ or higher than 35 ℃. The AER Q₁₀ of juvenile R. esculenta was 0.767-4.362, while the OCR Q₁₀ was 1.299-2.201; the AER Q₁₀ of adult R. esculenta was 0.617-4.147, and the OCR Q₁₀ was 0.714-2.519. In this study, the average value of O∶N of R. esculenta under different conditions was 1.392±0.424, indicating that R. esculenta metabolized mainly by consuming protein. This research through the study of the metabolic experiment of R. esculenta under different conditions, explored the effects of different environmental factors on R. esculenta rate of oxygen consumption ammonia excretion rate, to achieve the scientific management of the R. esculenta resources in China and provides the technical support for sustainable development and utilization.

Abstract:In order to improve the accuracy of bigeye tuna (Thunnus obesus) fishing ground forecast model in the tropical waters of Atlantic Ocean, a series of fishery forecast models were established based on the logbook data of 13 Chinese longliners from 2013 to 2019 and the corresponding marine environment data, e.g. sea surface wind speed, chlorophyll a concentration, eddy kinetic energy, upper boundary depth of thermocline, vertical temperature, salinity and dissolved oxygen in 0-500 m water layer. T. obesus CPUE was calculated based on the logbook data. The environmental factors related to T. obesus CPUE were screened out from 29 environmental factors by correlation analysis. The non-collinear environmental factors were selected by collinearity analysis based on the variance expansion factor (VIF) and used to build the bigeye tuna fishing ground prediction models. The Spearman correlation coefficients between non-collinear environmental factors and T. obesus CPUE were calculated and used to analyze the relative importance of the environmental factors to the T. obesus CPUE. These series of prediction models, e g. K-Nearest Neighbor (KNN), Logistic Regression (LR), Classification and Regression Tree (CART), Support Vector Machine (SVM), Artificial Neural Networks (ANN), Random Forest (RF), Gradient Boosting Decision Tree (GBDT), and Stacking ensemble model (developed by KNN, RF and GBDT, STK) were built by using 75% of data and verified by using 25% of data. The time resolution of T. obesus CPUE and marine environment data was one day, and the spatial resolution was 2°×2°. The performance of 8 models were evaluated by the area under the receiver operating characteristic curve (AUC) and prediction accuracy. The maps of the actual fishing ground and the predicted fishing ground were overlapped by ArcGIS and used to evaluate the performance of the best model. The central bigeye tuna fishing ground was determined by the nuclear density analysis tool of ArcGIS. The results show that (1) compared with the single model (KNN, LR, CART, SVM, ANN, RF and GBDT), the forecasting performance of T. obesus fishing ground of STK model was better and relatively stable. The accuracy (AUC) of the STK model, KNN, LR, CART, SVM, ANN, RF and GBDT were 81.62% (0.781), 79.44% (0.778), 72.81% (0.685), 74.84% (0.717), 73.67% (0.702), 67.70% (0.500), 80.96% (0.780), and 78.13% (0.747), respectively; (2) the distribution of central fishing ground predicted by STK model was basically consistent with the actual distribution of central fishing ground, all of them were mainly distributed in the area of 5 °N-10 °N, 33 °W-43 °W; (3) the marine environmental factors that affect the distribution of T. obesus fishing grounds in the Atlantic Ocean mainly included dissolved oxygen of 300 m layer, salinity of 500 m layer, sea surface wind speed and upper boundary depth of thermocline, and the relative importance were 13.24%, 9.12%, 9.12% and 8.81%, respectively. The results suggest that the accuracy of the STK model for T. obesus fishing ground forecast in the Atlantic Ocean is high.

Abstract:The Yarkand River is located on the western edge of the Tarim Basin in southwestern Xinjiang, and the longest source of the Tarim River. Affected by the uplift of the Qinghai-Tibet Plateau at the end of the Tertiary Period, this waters gradually formed a unique fish population structure, with Schizothoracinae as its typical representative species. Typical representatives of Schizothoracinae included Schizothorax irregularis, S. eurystomus, S. biddulphi and S. barbatus. The four common Schizothoracinae are highly similar in appearance, and the countable and measurable traits are mostly crossed. Affected by work experience and cognition, the four species are prone to misjudgment in the identification, and many scholars often question this classification system. This paper intends to establish a discrimination system for Schizothoracinae identification through comparing traditional morphometric and Box-truss data system, and provide reference and information for subsequent research. The differences among the species of Schizothoracinae (4 species, 494 individuals, 48 groups of parameters) were detected through ANOVA, PCA, DFA and Cluster Analysis. The results of ANOVA showed that 9 parameters were significantly different in the 4 species of Schizothoracinae at the same time (P<0.05), and the difference was mainly located in the head, front trunk and rear trunk of the fish. PCA results showed that there was significant difference in PC1 axis between S. barbatus and S. irregularis based on the morphological data, which is mainly represented the head characteristics. However, the results of the Box-truss data showed that the difference between S. biddulphi and S. eurystomus mainly reflected in the rear trunk. The 8 and 6 main parameters were selected to establish the discriminant formulas for two data structures, and the initial discrimination success rates reached 85.7% and 75.7%, respectively. The cluster analysis results showed that the two data systems are divided into two branches, among which S. barbatus is a separate group, the S. biddulphi and S. irregularis are closer in morphology, followed by S. eurystomus. The using of multivariate statistical methods can better distinguish the four Schizothoracinae species in the Yarkand River Basin, and the morphological data performed better than the Box-truss data by contrasting two data systems. However, there is still confused distinguish characteristic in species identification. These findings can be used to quickly verify the Schizothoracinae that are difficult to accurately identify based on the lip characteristics, and would accumulate basic data to provide a reference for follow-up research.

Abstract:After a century of development, marine ranching through the 1.0 stage driven by agro-pastoralism and engineering, the 2.0 stage driven by ecology and information technology, and is moving towards the 3.0 stage driven by digitalization and systematization. From the perspective of aquatic ecology and landscape ecology, aquatic ecological ranching attaches great importance to the connectivity and integrity of ecosystem, which is an essential scene for expanding fishery space and promoting integrated development. In order to achieve healthy and high-quality development of fisheries, ecological and digital economies should jointly promote the model innovation and industrial development of aquatic ecological ranching. This paper reviews the necessity, development concept and response strategy of the construction of aquatic ecological ranching, and demonstrates how digital empowerment promotes the systematic and digital construction of aquatic ecological ranching from three aspects: key technologies, unmanned equipment and intelligent management. In terms of key technologies, we will establish a precise technical system and take a transition to a standardized technical system in all aspects of monitoring and evaluation, site selection and layout, restoration and maintenance, and information management. In terms of unmanned equipment, we will establish a light and simplified equipment system and take a transition to an unmanned technology system, including environmental monitoring equipment, resource detection equipment, ranch construction equipment, information management equipment, industry integration equipment. In terms of intelligent management, we will establish a full-cycle process-oriented management system and take a transition to a full-chain intelligent management system. We also propose the development model of four linked fields, land and sea relay, grazing and breeding interaction, and industry integration, so as to provide a reference for better use of digital technology to build aquatic ecological ranching in a scientific and standardized way.

Abstract:Locomotion is considered a fundamental property of most aquatic animals and is crucial for the survival of such animals. To explore the behavioral characteristics of locomotion and their relationships with muscle energy metabolism of Macrobrachium rosenbergii, the experiments of swimming and tail-flipping with four intensities (control, low, medium and high) were conducted. The behavior, energy sources and related metabolic enzyme activities of M. rosenbergii were determined after locomotion. The swimming intensities were obtained by setting different water velocities in a specific time period. The water velocities of control, low, medium and high intensity swimming were 0 (voluntary locomotion), 5 (200 min), 10 (200 min) and 15 cm/s (swimming until fatigue) respectively. The tail-flipping intensities were determined by setting different touch frequencies in a specific time period. The touch frequencies of control, low, medium and high intensity swimming were 0 (voluntary locomotion), 0.033 (5 min), 0.050 (5 min) and 0.067 Hz (tail-flipping until fatigue) respectively. Results showed that the maximum beat frequency (f_max) and maximum beat amplitude (A_max) of pleopods and uropods were significantly higher in each locomotor group than those in the control group. There were no significant differences in muscle protein contents among different locomotor groups. The contents of muscle glycogen were significantly decreased in each locomotor group compared with that in the control group. The lowest contents of triglyceride in pleopods muscles were observed in the low-intensity swimming group. The activities of lactate dehydrogenase (LDH) and lactate contents in pleopods muscles were significantly elevated in medium and high intensity swimming groups compared with those of control group. The activities of pyruvate dehydrogenase, malate dehydrogenase and lipase in pleopods muscles were significantly increased in low-intensity swimming group compared with those of control group. The LDH activities and lactate contents of abdominal muscles were significantly higher in each tail-flipping group than those of control group. Our findings indicate that the energies of locomotion are obtained by increasing the intensity of muscles energy metabolism in M. rosenbergii. The energy metabolism pathways of swimming vary according to swimming intensities. Tail-flipping is powered by anaerobic metabolism. These findings enhanced our understanding of physiology and behavior of locomotion in prawns, providing basic data for the healthy culture of M. rosenbergii.

Abstract:The blood of the horseshoe crab, an ancient marine arthropod, is widely used in the production of tachypleus amebocyte lysate (TAL) for medical testing. The number of horseshoe crab resources in China has declined significantly in the last 30 years. The study of the relationship between morphological traits and body mass of Tachypleus tridentatus and the analysis of anisotropic growth will not only help to understand the growth characteristics of juvenile T. tridentatus, but also reflect the resource allocation strategy and help to conserve horseshoe crab resources. In this study, the cephalothorax length (X₁), cephalothorax width (X₂), opisthosoma length (X₃), opisthosoma width (X₄), telson length(X₅), total length (X₆) and body mass (Y) of 2-4 instars juvenile T. tridentatus were measured, correlation analysis and path analysis were used to explore the effect of morphological traits on body weight. The results showed that the morphological traits with the highest correlation coefficient (r) of body weight of 2-4 instars juvenile T. tridentatus were cephalothorax width (X₂). Path analysis showed that the cephalothorax width (X₂) had the most immediate impact on the body weight of 2 and 3 instars juvenile T. tridentatus, and the opisthosoma width (X₄) had the greatest direct impact on the body weight of 4 instars juvenile T. tridentatus. The determination analysis showed that the cephalothorax width (X₂) had the largest determination coefficient for the body weight of 2 and 3 instars juvenile T. tridentatus, and the opisthosoma width (X₄) had the largest determination coefficient for the body mass of 4 instars juvenile T. tridentatus. The determination analysis was consistent with the path analysis. The cephalothorax width and body weight of 2-4 instars T. tridentatus are processed logarithmically.The allometric growth equation was obtained: y=−1.095+2.746x, and the regression coefficient is 2.746(b > 1). This shows that the growth rate of juvenile horseshoe crab body mass is greater than the growth rate of cephalothorax width at this stage, and it is at the stage of positive growth. The present study shows that the morphological traits of seedling screening of T. tridentatus at different age stages are distinct, and the evaluation of the germplasm of the juvenile T. tridentatus should take into account its allometric growth pattern. The current study also provides a basis for exploring the relationship between growth and traits, structure and physiology of T. tridentatus.

Abstract:Cod and bullfrog scraps were selected as protein sources to prepare fish protein hydrolysate and bullfrog protein hydrolysate, and four isonitrogenous and isolipidic diets were formulated. Scophthalmus maximus with an initial body weight of (8.00±0.01) g was fed for a period of 56 d in order to explore the utilization efficiency of protein hydrolysates from different sources by S. maximus. The experimental designed two control groups with no protein hydrolysate, the positive control group contained 35% fish meal and the negative control group including 26.5% fish meal. Two experimental groups had different sources of protein hydrolysates, the FPH group contained 26.5% fish meal and 8.0% fish protein hydrolysate, and the BPH group contained 26.5% fish meal and 9.5% bullfrog protein hydrolysate. The results showed as follows: the final body weight, weight gain rate and special growth rate of the FPH group were significantly higher than those of the BPH and NC groups (P<0.05), but there was no significant difference between the FPH and PC groups (P>0.05). The concentrations of essential amino acids in chyme including lysine, arginine, threonine and valine in the BPH group were significantly higher than those in the PC group (P<0.05). There was no significant difference in the contents of other non-essential amino acids except for taurine and tyrosine, and the concentrations of most amino acids were the highest in the BPH group. The mRNA levels of proton-coupled amino acid transporter PAT1 and small peptide transporter PepT1 in the FPH and BPH groups were significantly higher than those in the PC and NC groups (P<0.05). There was no significant difference in the mRNA levels between cationic amino acid transporter CAT1 and Y⁺L-type amino acid transporter Y⁺LAT2 among all treatment groups (P>0.05). In conclusion, the addition of protein hydrolysates in the feed could promote growth performance of S. maximus, and fish protein hydrolysate showed more beneficial effects on the growth than that of bullfrog protein hydrolysate. The responses of amino acid concentrations in chyme and the expressions of amino acid and small peptide transporters also indicated that the feed utilization efficiency of S. maximus supplemented with fish protein hydrolysate was higher than that with bullfrog protein hydrolysate.

Abstract:In order to explore the optimal carbohydrate addition types in the dietary of juvenile Onychostoma macrolepis, five diets were prepared with glucose, maltose, dextrin, corn starch and cellulose as carbohydrate sources and the fish was cultured for 56 days. The results showed that, ① The terminal weight, specific growth rate, feed coefficient rate and protein efficiency rate were the best in the maltose group (P<0.05), while those in the cellulose group were the worst (P<0.05). ② The crude fat of whole fish in the cellulose group was the lowest (P<0.05), the crude ash content was significantly higher than that in the maltose group (P<0.05), the muscle glycogen content in the maltose and cellulose groups was the lowest (P<0.05), and liver glycogen in the dextrin group was the lowest (P<0.05). ③ Principal component analysis showed that the ratios of C16:0, SFA, MUFA and PUFA had a major effect on the overall fatty acid ratio of the liver. Among them, the ratios of C16:0 and SFA were significantly increased in the maltose group (P<0.05), while the ratio of MUFA in the dextrin group (P<0.05), and the ratio of PUFA in the cellulose group were also significantly increased (P<0.05). The proportions of C18:1n-9 and MUFA had the main effect on the overall fatty acid composition of muscle and adipose tissues, and the proportions of the two were significantly increased in the maltose group (P<0.05). ④ Glutamic pyruvic transaminase in serum of maltose and cellulose groups is the highest (P<0.05), while that of aspartate aminotransferase was the highest in maltose group (P<0.05). Alkaline phosphatase activity and globulin content of glucose and cellulose group were the highest, while that of blood glucose was the reverse (P<0.05). ⑤ The contents of catalase, total superoxide dismutase, glutathione peroxidase in the liver of the maltose group were the highest (P<0.05), while the malondialdehyde content in the cellulose group was the highest (P<0.05). In conclusion, maltose was the most suitable carbohydrate source for juvenile O. macrolepis, followed by dextrin and corn starch, and cellulose and glucose were not the suitable carbohydrate source for the fish; corn starch is recommended as a carbohydrate source in practical production, which will provide an important reference for research and development of its specific compound feed.

Abstract:Cadmium (Cd) is one of the heavy metal contamination sources and can be released into the aquatic environment through agriculture, industry and other human activities. In most contaminated aquatic environments, the fish are often threatened by excessive accumulation of Cd, which may cause oxidative stress, immune damage, growth inhibition and even death of fish. In addition, Cd exposure can promote the metal bioaccumulation in fish, thereby continuously affecting human health through the food chain. Thus, identifying a safe and effective natural substance against Cd toxicity is of great importance for the effective management of aquatic animal health and alleviaton of the pressure on food safety. The use of probiotics to protect the humam body from the toxicity of heavy metals has become a hot research topic in recent years. The purpose of this test is to explore the effects of Bacillus coagulans SCC-19 on the cadmium content, antioxidant capacity and inflammatory response in the liver of Cyprinus carpio under cadmium exposure. The 450 C. carpio with an average weight of (34.00±1.16 g) were selected and randomly divided into 5 groups (control group, 0.5 mg/L Cd²⁺ group, 0.5 mg/L Cd²⁺+10⁷ CFU/g B. coagulans group, 0.5 mg/L Cd²⁺+10⁸ CFU/g B. coagulans group and 0.5 mg/L Cd²⁺+10⁹ CFU/g B. coagulans group), with 3 replicates in each group and 30 fish in each replicate. The results indicated that compared with the cadmium exposure group, B. coagulans SCC-19 could effectively reduce the cadmium content in the liver of C. carpio, and reduce the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, and significantly increase the level of metallothionein (MT) in the liver of C. carpio. In addition, the total antioxidant capacity (T-AOC), anti-superoxide anion free radical activity (ASA) and anti-free radical hydroxyl ability (AHA) of in the liver of C. carpio in the B. coagulans SCC-19 groups were significantly higher than the those in control group, while the levels of reactive oxygen species (ROS), malonaldehyde (MDA) and hydrogen peroxide (H₂O₂) in the B. coagulans SCC-19 groups were significantly lower than those in the control group. Moreover, the results showed that B. coagulans SCC-19 could alleviate the genes of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and transforming growth factor-β (TGF-β) abnormal expression. The results of the study show that B. coagulans SCC-19 can reduce the cadmium content, relieve oxidative stress, and inhibit inflammation in the liver of C. carpio under cadmium exposure.

Abstract:In China, Procambarus clarkii is the most widely cultivated freshwater crayfish now, the breeding area and output are increasing every year and the culture models have also been constantly innovated. In recent years, the area of rice-P. clarkii co-culture has been increasing explosively, and its output has accounted for more than 80% of the national total output, so the rice-P. clarkii co-culture has become the basis for the rapid development of crayfish industry. With the expansion of aquaculture scale and deterioration of aquaculture environment, various diseases occur frequently which seriously affect the yield and quality of P. clarkii. In order to find out the death cause of P. clarkii cultured in paddy field, the pathogenic bacteria were isolated from stomach and intestine of these dying crayfish with obvious pathological characteristics, and were identified through physiological and biochemical testing, sequence alignment of 16S rDNA gene and phylogenetic analysis. At the same time the virulence and drug sensitivity of pathogenic bacteria were evaluated by artificial infection and drug sensitivity test, the pathogenic mechanism of pathogenic bacteria was studied by analyzing the variations of serum immune related enzymes activities of P. clarkii injected with pathogenic bacteria. Research results showed that a dominant strain named PCW-01 was obtained and identified as Aeromonas veronii which could cause the healthy P. clarkii to have these same pathological symptoms as the natural disease, such as less exercise, effusion in stomach, excessive intestinal mucus in the regression experiment, and its median lethal dose was 0.60×10⁵ CFU/g to P. clarkii. The analysis of antimicrobial susceptibility test showed that A. veronii (PCW-01) was highly sensitive to furantoin, tobramycin, ceftazidime and other seven antibiotics. The results of serum immune enzyme test showed that in the body of P. clarkii injected with pathogenic bacteria, the activity of lysozyme (LZM) and alanine arninotransferase (ALT) increased considerably (P<0.01), the activity of total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) decreased notably (P<0.01), and the concentration of MDA increased slightly (P>0.05). The conclusion was that the strain PCW-01 was the pathogen of the death of P. clarkii, which could inactivate antioxidant factors, destroy cell membrane structure and function, subsequently the pathological phenomena of tissues and organs or death appeared. In the study, these results revealed immune response law of P. clarkii to pathogenic bacteria and will provide scientific support for the prevention and control of the bacterial diseases of P. clarkii in future.

Abstract:In order to regulate the drug use behavior of aquaculture producers and promote the green development of aquaculture industry in China, based on the survey data of mariculture producers in 11 provinces and cities along the coast of China, this paper used logit model, linear regression model and intermediary effect model to empirically analyze the influence of industrial organization pattern on the drug use behavior of mariculture producers and its mechanism. The results showed that (1) the compact industrial organization had a significant positive effect on the safe drug use behavior of producers; (2) The drug consumption of the producers who joined the compact industry organization decreased significantly; (3) Different types of compact industrial organizations had different influences on the drug use behavior of producers. The "cooperative (association) + producer" mode is significantly better than the "enterprise-led production base + producer" mode. (4) Breeding training had a mediating effect on the influence of compact industrial organization mode on drug use behavior of producers, which could further reduce drug use by training knowledge and skills and providing problem-solving measures. Based on this, the paper puts forward suggestions on attaching importance to the role of compact industrial organizations, especially cooperatives (associations), carrying out training on green aquaculture for producers, and developing aquaculture insurance, so as to accelerate the green development of Chinese aquaculture industry.

Abstract:The effects of metmyoglobin (MMb) on the quality of cured fish were studied by adding different concentrations of MMb into the cured grass carp to construct the sample reaction system. Based on the carbonyl compounds, lipid content, fatty acid composition and volatile flavor compounds, the mechanism of MMb promoting lipid oxidation in traditional processing of cured grass carp was studied. As a result, the contents of three carbonyl compounds increased gradually, and the increasing trend was "4-hydroxyhexenal > 4-hydroxynonenal > malondialdehyde" with the increase of MMb concentration. Compared with the control group, the contents of total lipids, triglycerides and phospholipids in the 0.8 mg/g MMb group decreased the most (18.95%, 18.72% and 31.83%, respectively). However, the content of free fatty acids showed a completely opposite trend (increased by 6.74%). The higher the concentration of MMb, the easier the oxidative degradation of polyunsaturated fatty acids (PUFA) in fish samples, especially linoleic acid and arachidonic acid (the relative content decreased by 12.37% and 16.27%, respectively). Six categories and 41 kinds of volatile flavor components were detected, and 13 kinds of odor active compounds such as pentanal were identified. All the odor active compounds except decanal were significantly negatively correlated with the relative content of PUFA. It indicated that MMb-mediated lipid photooxidation may be the main mechanism of traditional cured fish aroma.