Abstract:Aeromonas hydrophila is a common pathogen in water environment and has strong pathogenicity. In this study, the gene aguA of A. hydrophila was knocked out for the first time. Transcriptome analysis and qRT-PCR indicated that the knockout of aguA down-regulated the bacterial adhesion process, pathogenic process, amine metabolism process and etc. In addition, type Ⅵ secretion system genes, type Ⅱ secretion system genes, flagella synthesis-related genes, fimbriae synthesis-related genes, hemolysis genes, type Ⅰ secretion system genes, enterotoxin genes, and RTX genes were also down-regulated at the transcriptome level. qRT-PCR showed that most of these genes were significantly down-regulated. Compared with the wild strain, the pathogenicity of A. hydrophila aguA-knocked-out strain infected grass goldfish was reduced by 86.6% through infection experiment in vivo, and it was found that the biofilm formation ability of the aguA-knocked-out strain was reduced by 16.6%. The above results show that aguA gene is closely related to the pathogenicity of A. hydrophila.

Abstract:To investigate the molecular mechanism of cilp in the development of vertebrae and intermuscular bones in zebrafish, we established a zebrafish cilp^-/- homozygous mutant strain by CRISPR/Cas9. The bones staining of wild type zebrafish and cilp^-/- strain showed that the loss function of cilp caused abnormal fusion of vertebrae and deficiency of neural spine in mutants, and the number of intermuscular bones in cilp^-/- strain was significantly reduced by 10.27%, while the length of intermuscular bones did not change significantly. Furthermore, we analyzed the expression levels of 14 bone development-related genes in five embryonic development stages and 90 dph (days post hatching) adult fish skeletal tissue. The results showed that the col1a1a, sp7, smad4a, and smad5 genes were significantly differentially expression throughout the embryonic development stages compared to the wild type, the expression levels of bmp2a, bmp2b, smad5, sp7, runx2a, runx2b, and bglap in the skeleton of the 90 dph mutant adult fish were significantly lower than those of the wild type zebrafish, which indicated that the cilp gene knockout down-regulated the expression levels of genes in BMPs and SMADs families which consequentially repressed the expression of genes related to osteoblast development. In summary, dysfunctions of the cilp gene might affect the development of intermuscular bones and skeleton in zebrafish by suppressing the BMPs signaling pathway to affect the development of osteoblasts and bones formation.

Abstract:Tumor Necrosis Factor Superfamily (TNFSF) and Tumor Factor Receptor Superfamily (TNFRSF) regulate cell apoptosis, metabolism and development. To explore the expression and function of TNFSF and TNFRSF in teleosts, we cloned tnfsf10 and tnfrsf10 of the sterlet, Acipenser ruthenus,and analyzed their structure and evolution. Results showed that, Tnfsf10 and Tnfrsf10 of the sterlet were located at the base of actinopterygii branch in phylogenetic tree and have low homology with Tnfsf10 and Tnfrsf10 of the tetrapod, however, their tertiary structure is similar to Tnfsf10 and Tnfrsf10 of the human. Whole-mount in situ hybridization analysis showed that tnfsf10 and tnfrsf10 were mainly expressed in the horizontal muscle septum of the trunk, infraorbital canal of the head, preopercular lateral line, and neuromast of the ventral rostral. After being treated with Tnfrsf10 specific activator Bioymifi, the morphology of sterlet larvae did not change significantly, but the number of hair cells in neuromast increased significantly. The findings suggest that the Tnfsf10 and Tnfrsf10 of the sterlet represent the original form of the teleost homologous protein, which may be specifically involved in the development of hair cells in the lateral line neuromast.

Abstract:The virulence gene vah1 in Vibrio anguillarum was knocked out by gene recombination, and the strain Δvah1 with vah1 deletion was constructed in this study. The hemolytic activity of Δvah1 strain decreased by 89.4% and the biofilm forming ability decreased by 16%. The median lethal dose (LD₅₀) of Δvah1 strain infected Litopenaeus vannamei was (9.77±0.50)×10⁵ cfu/mL, compared with (3.16±0.80)×10⁵ cfu/mL of the LD₅₀ of the wild strain of V. anguillarum,it increased by 2.09 times; the colonization ability of Δvah1 strain in L. vannamei decreased evidently after vah1 deletion. Compared with the wild strain of V. anguillarum, the destruction degree of Δvah1 strain on hepatopancreas cells was significantly smaller. After Δvah1 strain infected L. vannamei, the expression levels of immune related genes CAT, SOD, PO, LZM and ACP in hepatopancreas decreased to some extent. These results showed that the hemolysis and pathogenicity to L. vannamei of the vah1 deficient V. anguillarum strain were reduced in varying degrees, which laid a foundation for the preparation of subsequent attenuated vaccines or specific immune enhancers against V. anguillarum.

Abstract:Janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling pathway is one of the most important ubiquitous cell signaling pathways in animals. In vertebrates, it is mainly involved in regulating the expression and secretion of many cytokines. The members of the suppressor of cytokine signaling (SOCS) family are the important JAK-STAT pathway inhibitory factors. Cytokine-induced SH-2 containing protein (CISH) is one known family members of SOCS, with its main function involved in regulating the signaling of interleukin-2. In this study, the full-length cDNA sequence of Cyprinus carpio CISH with the length of 1 685 bp was cloned. The open reading frame (ORF) was 666 bp in length and encoded 221 amino acids. The molecular weight of the deduced protein was 24.91 ku. C. carpio CISH possesses typical SOCS family structure, with three functional domains including N region, central SH2 domain and C terminal SOCS box domain, the latter two being conservatively present in CISH proteins of other bony fish. The phylogenetic analysis showed that the common carp CISH was the closest to CISHs of grass carp and zebrafish, which also belong to Cyprinidae. The results showed that the mRNA expression level of C. carpio CISH in blood was the highest, and the lowest expression level in liver. After being stimulated by Aeromonas hydrophila, the expression of C. carpio CISH in blood was up-regulated significantly at 24 h, and returned to the normal level at 48 h, suggesting that it may play an important role in the process of the resistance to bacterial infection.

Abstract:The expression patterns of TLR18, MyD88, and corresponding ligand TRAF6, downstream factor IRF5, and P65 in spleen tissues of breeding strain F₄ and German mirror carp were determined by RT-PCR. The difference of related genes in disease resistance mechanism between breeding strain F₄ and German mirror carp was analyzed. The results show:the expression of TLR18, MyD88, TRAF6, and IRF5 showed the same trend between the two groups, which increased first, then decreased and stabilized, and reached the highest at 48 h, while the relative expression of P65 in non-breeding strain increased first, then decreased and recovered to the initial level, and reached the highest at 48 h. In breeding strain, the expression trend decreased and then recovered to the initial level. The relative expression of TLR18 and IRF5 in breeding strain was significantly lower than that in the non-breeding strain without CyHV-3 infection. The relative expression levels of MyD88, TRAF6, and P65 in breeding strain were significantly higher than those in non-breeding strain. At the early stage of CyHV-3 infection, the relative expression levels of TLR18 and P65 in breeding strain were significantly lower than those in non-breeding strain, while the relative expression levels of MyD88, TRAF6, and IRF5 in breeding strain were significantly higher than those in non-breeding strain. It is speculated that during CyHV-3 infection, TLR18 generateed IRF5 by binding to TRAF6 through the MyD88 pathway, which cleared the virus and activated the NF-κB signaling pathway to produce inflammatory factors. In breeding strain, more IRF5 was produced and the NF-κB signaling pathway was not significantly activated to resist the virus. This result may be related to breeding. These results not only verified the improvement of CyHV-3 resistance in breeding strain in the body basic condition and innate immunity but also laid a foundation for further study of the role of fish TLRs in the process of virus infection and related signaling pathways.

Abstract:Off-flavor problem commonly exists in traditional aquaculture systems, and it has been reported that a temporary rearing model with clean water could remove the off-flavor in fish effectively. In order to study the effect of temporary rearing on off-flavor depuration and fish quality improvement of largemouth bass (Micropterus salmoides), we have cultured fish in pond with Vallisneria spiralis for different time (0, 1, 4, 7, 10, 13, 16 d). The results showed that:(1) The concentration of 2-methylisoborneol (2-MIB) and geosmin (GSM) decreased from (0.42±0.01) μg/kg and (0.54±0.06) μg/kg to (0.33±0.05) μg/kg and (0.35±0.06) μg/kg, respectively (10th day). (2) Moisture of fish muscle was decreased significantly to (74.90±2.40)% (7th day), and ash content was increased significantly to (1.27±0.17)% (7th day). The total sugar content firstly decreased and then recovered to the initial level of (0.49±0.03) g/100 g (13th day). (3) Three kinds of unsaturated fatty acids (C20:3n3, C20:4n3 and C22:4n6) were increased, and 23 kinds of total fatty acids were detected in fish (10th day); there were 16 kinds of free amino acids, and the taste active values (TAV) of amino acids were significantly different through the extension of rearing time (P<0.05), including glutamate (TAV>1) with umami taste and histidine (TAV<1) with bitter taste. (4) After 10 days of temporary rearing, the hardness and chewiness of fish were significantly increased. In conclusion, the temporary rearing in clear water pond planted with Vallisneria spiralis could significantly depurate off-flavor and improve the quality of largemouth bass, and a 10-day temporary rearing is beneficial to both quality and economic value enhancement.

Abstract:The growth, cellular biochemical composition, and α-Linolenic acid content of Chlorella pyrenoidosa SHOU-1002 treated with streptomycin sulfate(STRS) at mass concentrations of 0 (CK), 20, 60, 180 and 540 μg/mL were examined. The results showed that the microalgal cell density in the CK group was significantly higher than those in STRS treated groups in the first 6 days. The biomass and single cell weight of the CK group on the 10th day were significantly higher than those of STRS treated groups. The biomass of STRS treated group decreased continuously with the increasing of STRS mass concentration in medium. The contents of Chlorophyll a, Chlorophyll b, and carotenoids in microalgae of CK, 20, 60, and 180 μg/mL STRS groups, firstly decreased then increased with prolongation of the culture time. The contents of Chlorophyll a and Chlorophyll b continuously declined while carotenoids sharply decreased in the first 4 days then stabilized in the treatments of 540 μg/mL STRS group. During the whole culture period, α-Linolenic acid was the dominant in the fatty acid profiles of C. pyrenoidosa SHOU-1002. The α-Linolenic acid contents (%) in STRS treated groups were significantly higher than that in the CK group since the 4th day. On the 10th day, the microalgae in 180 μg/mL STRS group had the highest content of α-Linolenic acid (52.09 mg/g), which increased by 108.19% as compared to that of the CK group. Moreover, the microalgae in 180 μg STRS/mL group also had the highest α-Linolenic acid yield (35.34 mg/L). The correlation analysis illustrated that α-Linolenic acid content and chlorophyll a content of the microalgae were negatively, highly, and significantly correlated. It is therefore suggested that STRS in culture medium decreased the chlorophyll a content and biomass, but promoted the accumulation of α-Linolenic acid in C. pyrenoidosa SHOU-1002.

Abstract:In order to improve the survival rate of Litopenaeus vannamei during transportation with water after carbon dioxide (CO₂) anesthesia, the effects of CO₂ flow rates (anesthesia stage), soaking time (soaking stage), water type and salinity (recovery stage) on the survival rate were studied. The experiment set four factors:CO₂ flow rates (3 L/min, 5 L/min and 7 L/min), soaking time (0 min, 1 min and 5 min), water type (tap water, supernatant of aquaculture water and aquaculture water) and salinity (3, 7 and 11). The single factor experiment was carried out, and the L₉(3⁴) orthogonal experiment and verification experiment were carried out based on the single factor experimental results. The results showed that in the single factor experiment, the best CO₂ flow rates was 7 L/min, the best soaking time was 0 min, the best water type was tap water and the best salinity was 7. The results of orthogonal experiment of transportation within 2 hours showed that the primary and secondary relationship of the four factors was:soaking time > water type > salinity > CO₂ flow rates, and the best combination was CO₂ flow rates of 8 L/min, the water type of tap water, the salinity of 7 and the soaking time of 0 min. The results of orthogonal experiment of transportation within 4 hours showed that the primary and secondary relationship of the four factors was soaking time > CO₂ flow rates > water type > salinity, and the best combination was CO₂ flow rates of 7 L/min, the water type of tap water, the salinity of 7 and the soaking time of 0 min. The results of orthogonal experiment of transportation within 6 hours showed that the primary and secondary relationship of the four factors was soaking time > CO₂ flow rates > salinity > water type, and the best combination was CO₂ flow rates of 6 L/min, the water type of tap water, the salinity of 7 and the soaking time of 0 min. The experimental results show that the recovery rate of Litopenaeus vannamei under different transportation time conditions can be improved by adjusting the levels of four factors:CO₂ flow rates, soaking time, water type and salinity, which provides a new idea for shrimp keep-alive transportation.

Abstract:Zacco tiaoxiensis, a new species of cyprinid fish from Tiaoxi river system in Zhejiang Province, southern China, is described. With morphological comparison, the new species is similar to Z. acanthogenys, which is widely distributed in Zhejiang Province. However, the new species could be distinguished from Z. acanthogenys by the following combination of characters:lateral- line scales comprising 41-44 (vs. 44-47), scales above lateral-line 8 (vs. 8-10), scales below lateral-line 3-4 (vs. 4-5), scales surrounding caudal peduncle 12-15 (vs. 14-17), for mature male individuals, the ventral fin reaching (vs. exceeding) the anus, etc. The morphological differences among the new species and the allopatric congener species of Z. sinensis and Z. platypus are mainly in the number of scales under the lateral line, comparable characters such as the ratio of head length to body length, and the color of the upper edge of the eyes when living. Moreover, the genetic analysis based on mitochondrial cytochrome b gene also supports that Zacco tiaoxiensis sp. nov. is a valid species.

Abstract:The Pacific oyster Crassostrea gigas is a mollusc with calcium carbonate shell, while the brachiopod Lingula anatina is with calcium phosphate biominerals. Here, we compared ultrastructure observations of the marginal region and the central region of mantles between C. gigas and L. anatina using histology and transmission electron microscopy (TEM) approaches. Our results found both species have similar cell types including the columnar epidermis cell, electron-dense granules cell and electron-transparent granules cell. However, the ultrastructure of the columnar epidermal subtype cells and the inclusion contents of secretory cells in those two species were different. The columnar epidermal cells of C. gigas consists of subtype A that mainly concentrated on the marginal region of mantle, subtype B mainly concentrated on the central region of mantle and subtype C was not common. The sizes of those cells were 7-15 μm. Meanwhile, columnar epidermal cells of L. anatina consist of subtypes A', B' and C'. Their sizes are 10-15 μm. As for secretory cells, both species had electron-dense granules cell and electron-transparent granules cell. However, L. anatina also contained a special class of secretory cells containing lamellar bodies. Those results can partially explain the difference of shell composition between brachiopods and mollusc, and provide reference for the study of shell formation mechanism and mineralization of brachiopods and mollusc.

Abstract:In recent years, impact of human activities has led to the destruction of balance of the water ecosystem, sharp reduction of biodiversity of aquatic organisms and degradation of water ecological health. Rapid and effective monitoring aquatic organisms is a prerequisite for evaluating water ecological health and carrying out protection and management of water ecological environment. Environmental DNA (eDNA) technology is a technology that uses molecular biology methods to extract DNA from environmental samples, sequence and analyze it to infer species information. Because this technology can obtain a large amount of species information only by collecting environmental samples (water, soil, sediment, etc.), with the characteristics of non-invasive, high sensitivity and low cost, it has attracted much attention in recent years. However, existing research practice shows that the current eDNA technology still faces some challenges, hindering it from becoming a standard and routine application. In this review, applications of the eDNA technology in aquatic organism monitoring are illustrated from different aspects:biodiversity investigation, invasive and endangered species monitoring, diet analyses, etc. The problems and challenges faced by eDNA technology are summarized in five aspects, including sampling efficiency, false positive and false negative, uncertainty of eDNA source, missing data in database and unsatisfying quantitative methods. The solutions and technical breakthroughs to these problems are further discussed. Finally, future perspectives of the eDNA technology are discussed, in order to provide inspiration for future work using eDNA technology.

Abstract:Microorganism is an important part of freshwater ecosystem and its community composition is closely related to water environment. Five experimental groups were set up in the laboratory to simulate the population structure of the ecosystem by planting the evergreen submersible plant Vallisneria natans and introducing Bellamya aeruginosa, Hyriopsis cumingii and Carassius auratus. In this paper, the effects of different aquatic organisms on bacterial community structure were explored by constructing a multi-trophic freshwater ecosystem. The results showed that the dominant bacteria groups in the freshwater ecosystem were Proteobacteria, Actinobacteriota, Bacteroidota and Cyanobacteria. The existence of snails, mussels and fish greatly reduced the number of Cyanobacteria in the water, which could effectively control the overreproduction of Cyanobacteria. The bacterial Shannon index was higher in Vallisneria natans and Vallisneria natans-Bellamya aeruginosa-Hyriopsis cumingii, but lower in Vallisneria natans-Bellamya aeruginosa and Vallisneria natans-Bellamya aeruginosa-Hyriopsis cumingii-Carassius auratus. RDA results showed that there were significant differences in the abundance of microbial communities among different systems. The introduction of different aquatic organisms and the content of DO are the direct factors affecting the change of microbial community, and the change of nutrient concentration is mainly dependent on the interaction between aquatic organisms and microorganisms, which is an indirect factor affecting the change of microbial community. In conclusion, the construction of multi-trophic ecosystem can not only improve the water quality, but also increase the diversity of bacteria in the water, change the community structure of bacteria in the water, and make it more healthy and stable.

Abstract:The effects on structure, morphology, composition and characteristics of reverse osmosis membrane fouling were investigated by an effluent with different Ca/Al ratios of membrane bioreactor in a biopharmaceutical enterprise.The results demonstrated that calcium and aluminum combined with organic matter formed a composite fouling layer on the membrane surface,and the change of Ca/Al ratio resulted in significantly different membrane fouling characteristics.The form of Al-O-H in the solution was preferentially combined with the organic functional groups by polar force,and it was co-deposited with the coagulation of the hydrophobic organic components under the condition of low aluminum content and high Ca/Al ratio.It had a far greater effect on the formation of membrane fouling than the Ca component. According to the extended Young's equation,the total surface tension of the system was calculated as:53.0 mJ/m² (low Ca low Al),69.5 mJ/m² (low Ca high Al),70.4 mJ/m² (high Ca high Al).It showed that the change of aluminum content mainly affected the polar force between the solution and the membrane material, and the change of the calcium content had almost no corresponding effect.The results of membrane cleaning indicated that the membrane fouling caused by calcium-aluminum components were stratified in spatial structure,and aluminum was tightly bound to the bottom layer of membrane fouling by the polar force between the molecules on the membrane surface, forming irreversible fouling.Calcium mainly existed in the contaminated filter cake layer which can be easily recovered by chemical cleaning.Therefore,it is of great significance to accurately control the dosage of aluminum salt in the coagulation pretreatment stage to prevent membrane fouling.

Abstract:We investigated the temporal variations of periphyton communities at three sampling sites in coastal river with different contamination levels in the Shanghai Pudong New Area using High Throughput Sequencing (V4 region of 18S rDNA). A total of 36 samples were collected, and 30 phyla and 681 genera of periphyton were identified including Pentatrocha, Philodina, Vorticella, Physocypria, etc. The composition of periphyton communities in rivers varied significantly with different contamination levels. The community structure of the periphyton communities changed significantly during the survey period, and the community succession in the river sections with different levels of contamination showed differences. The abundance of arthropods at site H decreased rapidly after a sudden increase, while the ciliate dominance decreased dramatically and the chlorophyta became dominant at both sites H and Y during the late sampling period. RDA analysis showed that salinity significantly affected the periphyton communities. Different dominant groups responded differently to environmental changes, such as Pentatrocha, Philodina and Vorticella. This study will provide basic data to further understand the diversity and spatial and temporal succession of periphyton in coastal river and to conduct ecological health assessment of periphyton in damaged water bodies.

Abstract:After comparing the removal effect of Vallisneria natans on Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and the responses of chlorophyll fluorescence parameters at low, medium and high concentration levels, our results showed that:(1) Among the four heavy metals, Vallisneria natans has the best removal effect on Cu²⁺ and the highest absorption of Zn²⁺. The maximum absorption of Cu²⁺, Zn²⁺,Cd²⁺ and Pb²⁺ by bitter grass were 4.21, 25.3, 0.231 and 0.509 μg/g respectively, the attenuation ratio of the medium mass concentration group of Cu²⁺ was the highest (47.33%),and that of the low mass concentration group of Zn²⁺, Cd²⁺, Pb²⁺ was the highest (33.13%, 29.2%, 45.7%);(2) Under heavy metal stress, the chlorophyll a content of Vallisneria natans in the Cu²⁺ and Zn²⁺ high mass concentration groups decreased less than that in the Cd²⁺ and Pb²⁺ high mass concentration groups, and the order of the decrease in chlorophyll b content was Zn²⁺ >Cu²⁺ >Cd²⁺ >Pb²⁺, and the high mass concentration group decreased significantly. (3) The maximum photochemical efficiency (F_v/F_m) and potential photochemical efficiency (F_v/F₀) of Vallisneria natans increased in different degrees under Cu²⁺ and Zn²⁺ stress, but decreased significantly under Cd²⁺ and Pb²⁺ stress. The photochemical quenching coefficient (Q_p), non-photochemical quenching efficiency (Q_n) and the quantum yield of regulatory energy dissipation (Y_NPQ) all decreased with the increase of heavy metal mass concentration, in which the decrease of Q_p in Zn²⁺, Cu²⁺, Cd²⁺, Pb²⁺ mass concentration groups decreased in turn, while the effective quantum yield (Y_Ⅱ) increased with the increase of heavy metal mass concentration. In general, Vallisneria natans is more suitable for removing Cu²⁺ and Zn²⁺ in water. The research results may lay a foundation for the ecological restoration of heavy metal polluted rivers.

Abstract:An indoor simulation test system with a mud (sediment) water mass ratio of about 1:1 and a period of 56 days was adopted. Six concentration gradient test groups, including the control group, were set up to study the change characteristics of total organic carbon (TOC) content in sediments caused by different levels of exogenous phosphorus input. At the same time, UV-Vis absorption spectroscopy was used to study the effect of phosphorus containing substances on the structural changes of dissolved organic matter in sediments. The experimental results showed that the TOC content in the sediment of each experimental group decreased by 3.60%, 7.08%, 8.09%, 9.33% and 11.80% respectively compared with the control group on the 56th day, indicating that the decomposition of TOC in the sediment of the Yangtze Estuary accelerated with the increase of exogenous phosphorus input. During the test period, the maximum humification degree and aromatization degree of dissolved organic matter in sediments were positively correlated with the input of phosphorus. The molecular weight and aromatic ring structure of dissolved organic matter were positively correlated with the input of exogenous phosphorus, indicating that the increase of exogenous phosphorus input could accelerate the change of dissolved organic matter in sediments. With the increase of test time, the humification degree and aromatization degree of dissolved organic matter with different phosphorus levels increased first, and then began to decline; The molecular weight of dissolved organic matter gradually decreased with the increase of time, and the substituents on its aromatic ring substituents were gradually replaced by more active functional groups. It shows that humus is formed during the reduction of organic carbon content in sediments. As humus continues to decompose, the degree of humification decreases, and the degree of humification is the same as that of aromatization.

Abstract:Chinese sturgeon Acipenser sinensis is an anadromous migratory fish species, which inhabits the Chinese coastal continental shelf areas and breeds in the Yangtze River Basin. The Yangtze River Estuary is an important migration passage of Chinese sturgeon. The Chinese sturgeon population is endangered, which has been listed as a top-level protected animal in List of key protected wild animals in China and a critically endangered species in IUCN Red List of Threatened Species. Since 2013, the abnormal interruption of natural spawning behavior of wild Chinese sturgeon has brought great challenges to the protection and restoration of Chinese sturgeon population. Based on the survey data of juvenile Chinese sturgeon resources in the Yangtze River estuary from 2004 to 2020, this study analyzed the population characteristics and migration habits of juvenile Chinese sturgeon in the Yangtze River estuary following the abnormal natural spawning behavior. The results show that:(1) Since natural spawning behavioral interruption of Chinese sturgeon, juvenile Chinese sturgeon was not detected in the Yangtze River estuary in 2014, 2016,2018, 2019 and 2020. The recruitment of juvenile Chinese sturgeon population in the Yangtze River estuary showed an interannual continuous fracture. (2) The migration habits of juvenile Chinese sturgeon changed significantly, it showed that the first occurrence time was advanced to mid-April, and the final occurrence time was delayed to late October, and the occurrence time span was extended by 118 days. (3) The biological indexes of juvenile Chinese sturgeon were lower than the same period in history; Their minimum body length and minimum body weight were 7.0 cm and 4.9 g respectively. To sum up, the juvenile Chinese sturgeon recruitment decreased year by year. The migration habit shows that the earlier the first occurrence time, the later the final occurrence time in the Yangtze River estuary.The results of this study will provide an important scientific reference for the protection of rare and endangered species of Chinese sturgeon.

Abstract:Mastering the migration and distribution of large nekton is the basis for analyzing their population dynamics, and carrying out population conservation and management. However, large nekton has strong swimming ability, wide range of activities and difficulty in recapture, so the traditional tagging technology has great limitations. Satellite Archival Tags technique has become one of the effective technical means to study the population changes and behavioral habits of deep-sea large nekton because of its features of not relying on retrieval, large data collection volume and high accuracy. Currently, mainstream Satellite Archival Tags are developed based on the Argos satellite system and transmitted via satellite channels, which has significant advantages over traditional tags that rely on sign recovery. This paper reviews the working principle, development history and main types of Satellite Archival Tags, introduces the main application progress, summarizes the problems and presents the research outlook, aiming to provide reference for the study of population dynamics and behavioral habits of large nekton.

Abstract:Eriocheir sinensis is a unique freshwater farmed crab in our country and has a high nutritional value due to its richness in cholesterol and various fatty acids. To better evaluate the effects of cooking treatments on the changes in cholesterol and fatty acid content of Eriocheir sinensis, the cholesterol and fatty acid contents of the three edible parts of Eriocheir sinensis were analyzed in both steamed and boiled versions of the crab yolk/roe, abdominal meat and leg meat. The results showed that the cholesterol contents of the three edible parts were similar in both male and female Eriocheir sinensis, and the cholesterol contents of each part were reduced by steaming and boiling, but the differences were not significant. Among the three edible parts, ∑MUFA was the highest in crab roe and crab paste, and ∑PUFA was the highest in abdominal meat and leg meat; steaming and boiling basically had no effect on fatty acids in crab roe, while boiling had a greater effect on fatty acids in crab paste than steaming, with a significant decrease; after steaming and boiling, the main saturated fatty acids in Eriocheir sinensis were still palmitic acid and stearic acid, monounsaturated fatty acids were mainly oleic acid, and polyunsaturated fatty acids were mainly oleic acid. After steaming and boiling, the main saturated fatty acids in Eriocheir sinensis were still palmitic acid and stearic acid, the monounsaturated fatty acids were mainly oleic acid and the polyunsaturated fatty acids were mainly linoleic acid, EPA and DHA. Therefore, compared to boiling, steaming reduces the loss of cholesterol and major fatty acids from edible parts, which is more beneficial to retaining the nutritional value of Eriocheir sinensis and is a guideline for the culinary treatment of Eriocheir sinensis.

Abstract:Vibrio parahaemolyticus(VP) is a common gram-negative bacterium, mainly distributed in marine, estuary and estuarine sediments, which can cause acute gastroenteritis, wound infection and sepsis in humans, and endanger aquatic product aquaculture. Food poisoning incidents caused by this bacterium occur frequently all over the world, and this bacterium is considered to be one of the main pathogens of microbial food poisoning. The virulence factors that affect the pathogenicity of VP include hemolysin, adhesion factor, secretion system, etc., especially in the secretion systems, Type Ⅲ Secretion Systems (T3SS) and Type Ⅵ Secretion Systems (T6SS). It is closely related to the pathogenicity of VP. T3SS is a multi-subunit needle-like structure that injects secreted proteins directly into the recipient cytoplasm through the donor cytoplasm; T6SS is a contact-dependent protein secretion apparatus that injects toxins directly into target cells. By sorting out the research progress of T3SS and T6SS, starting from the structure of these two secretion systems, and analyzing and comparing their functions and regulatory mechanisms, it was pointed out that the two are involved in effector proteins and regulatory mechanisms. The difference in the production of toxins, the relationship between the two and the colonization of VP were found out, in order to further understand the pathogenic mechanism of VP through the connection between the two, and provide scientific guidance for the prevention and treatment of the bacteria.

Abstract:Significant Wave Heights (SWH) is an important attribute to describe ocean waves, and SWH prediction is of great significance for ensuring the design of offshore engineering and the safety of offshore operations. In recent years, deep learning methods have been used to predict SWH, but the existing methods cannot effectively capture the long-term correlation of SWH, thus ignoring the local associations between multiple elements of the ocean. To this end, this paper proposes a SWH prediction model (Multi-elements Local and Global Correlation for Wave height Prediction, MLG-SWH) that combines local and global features of marine multi-elements. First, using multiple factors such as significant wave height, wind speed and period as input, a Local-Global Embedding (LGE) module is designed to embed local correlation and time information of ocean multi-elements. Then, an encoder-decoder structure is used to extract the features of ocean wave height, where a casual dilated convolution self-attention module is designed to effectively capture the global long-term correlation of ocean multi-element sequences and the generative prediction method in the decoder is adopted to avoid errors accumulated in the single-step iterative prediction. Finally, the data of two stations with different characteristics of SWH variation in the North Atlantic are selected for experimental evaluations. Compared with classical time-series forecasting models and mainstream deep learning methods, the MLG-SWH model achieves the lowest mean square error and mean absolute error in 24 and 48 hours SWH forecasting, having a greater advantage in long-term time series prediction.