Abstract:Insulin-like growth factors 2 (IGF2) plays an important regulatory role in the regulation of growth, differentiation and anabolism in a variety of cells. In this study, the recombinant plasmids pEGFP-IGF2 and PET32a-IGF2 of freshwater pearl mussel Hyriopsis cumingii were successfully constructed, and showed that the protein was localized in the cytoplasm and nucleus by pEGFP-IGF2-cell transfection. The pET32a-IGF2 was transformed into BL21 (DE3) for protein induction expression, and its prokaryotic expression vector was successfully obtained. SDS-PAGE showed a clear band at about 25 ku, which matched the size of the target band (26.27 ku), and was mainly expressed in the supernatant. In order to investigate the effect of recombinant protein IGF2 on the cellular activity of Hyriopsis cumingii, the proliferation activity of Hyriopsis cumingii mantle cells cultured with different mass concentrations of recombinant target protein (0, 2.5, 5.0, 7.5, 12.5, 17.5, 22.5 μg/mL) was further investigated by CCK8 cell activity assay. The results showed that IGF2 significantly promoted the proliferation activity of Hyriopsis cumingii mantle cells (P<0.05), and the best pro-growth effect was achieved at the mass concentration of 12.5 μg/mL, which laid the foundation for the promotion of Hyriopsis cumingii mantle cells and cell line establishment, and also provided the basis for the next investigation of the function of IGF2 in shellfish.

Abstract:The function of zebrafish transcription factor hoxb4a in the heart has not been reported. In order to clarify the role of hoxb4a in heart development, gene silencing and mRNA overexpression were used to knock down and overexpress hoxb4a gene in zebrafish, respectively. It was found that the embryo with inhibition or overexpression of hoxb4a had the phenotype of pericardial enlargement and abnormal cardiac looping at 3 days poster fertilization. Compared with wild-type and hoxb4a knockdown embryos by in situ hybridization, the measurement results showed that the heart looping angle of hoxb4a knockdown embryos increased. Then, using transgenic fish lines, we found abnormal endocardial abnormalities of pharyngeal arch in embryos after knockdown of hoxb4a. Furthermore, qPCR was used to detect the expression changes of heart-related genes after hoxb4a silencing. The results showed that most of the key genes of heart development were significantly down-regulated after hoxb4a knockdown, while the key gene nppa regulating cardiac differentiation was significantly up-regulated. This study shows that silencing of hoxb4a in zebrafish can lead to abnormal cardiac structure and looping, and regulate the changes of early cardiac development genes. In this study, we found that hoxb4a plays a role in the early cardiac development of zebrafish, and preliminarily explored the regulation of hoxb4a on the differentiation of cardiac chambers and cardiac looping through in situ hybridization and qPCR results, which deepened the understanding of the regulatory network of cardiac development.

Abstract:Myrmecia incisa Reisigl is a green coccoid freshwater microalga which is rich in polyunsaturated fatty acid. In the fatty acid synthesis pathway, the fatty acid desaturase was combined with the fatty acid acyl binding carrier to perform fatty acid desaturation. In order to explore the fatty acid acyl binding carrier combined with Δ15 fatty acid desaturase (FAD) of M. incisa Reisigl, Saccharomyces cerevisiae INVSc1 and (Synechococcus sp.) PCC 7942 were selected for verification whether Δ15 FAD bound to acyl-CoA (acyl-CoA) or acyl carrier protein (acyl-ACP) in the desaturation process, respectively. The binary expression vectors of pYES2-Δ15 FAD and pCAMBIA1300-Δ15 FAD were constructed on the basis of the Δ15 FAD gene of M. incisa Reisigl. The recombinant expression plasmids were transferred into INVSc1 and PCC7942 respectively, and the transgenic strains were screened. The similar number of transgenic yeast and transgenic cyanobacteria cells were cultured with addition of the same volume of linoleic acid (LA). After 36-72 h culture, the components of the total fatty acid were analyzed using the gas chromatography-mass (GC-MS) spectrometry system. The results showed that LA and ALA were detected in the transgenic cells, but the corresponding products were not detected in the blank control groups. By calculation, the efficiencies of conversion of LA to ALA were 29.31% and 30.86% in the transgenic yeast and transgenic cyanobacteria, respectively. According to the results, similar conversion efficiencies were obtained whether Δ15 FAD of M. incisa Reisigl combined with acyl-ACP or acyl-CoA, and there was no preference. In conclusion, Δ15 FAD was a fatty acyl binding protein in M. incisa Reisigl.

Abstract:In order to explore the response characteristics of Apostichopus japonicus transplanted to the south under high temperature stress,and to determine the expression changes of heat shock protein genes hsp10, hsp60, hsp70 and hsp90 at different temperatures, we studied the activity changes of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), catalase (CAT), acid phosphatase (ACP), alkaline phosphatase (AKP) and lysozyme (LSZ) at different temperature. The results showed that the expressions of heat shock protein genes in the experimental group (20, 24, 28, 32℃) were different from those in the control group (16℃), especially in the high temperature groups of 28 and 32℃. The expression of each gene increased significantly. Hsp70 is more sensitive to heat stress than other genes. Under 28℃ stress, in the comparison of intestinal tissues of southern population (group S) and northern population (group N), the expression of group N decreased gradually with the increase of time, while that of group S increased at first and then decreased. Except for hsp70, the expression of other genes in group S was lower than that in group N at each time point. The activities of SOD and LSZ in S and N groups increased at first and then decreased with the increase of temperature, while the activities of T-AOC, CAT, ACP and AKP decreased with the increase of temperature. Except that the activities of T-AOC and CAT in group S were lower than those in group N at 28℃, the activities of all enzymes in group S were higher than those in group N at other temperature. The results showed that the A. japonicus population that moved south showed higher temperature tolerance after a long period of annual culture in Fujian.

Abstract:Microalgae Isochrysis sp. and Myrmecia incisa have high nutritional value,which are rich in docosahexaenoic acid (DHA) and arachidonic acid (ArA) respectively. In the present study, the heterotrophic/mixotrophic strategies of these two microalgae were investigated. Results showed that when using glucose as the organic carbon source, both Isochrysis sp. and M. incisa were able to be heterotrophic, quickly accumulating biomass under complete darkness. The optimal glucose mass concentrations for Isochrysis sp. and M. incisa were 5 and 1 g/L, respectively. The effects of nitrogen mass in heterotrophic culture were also evaluated. For Isochrysis sp., 300 mg/L of sodium nitrate was the optimal for biomass production as well as for the intracellular accumulation of DHA. For M. incisa, nitrogen mass concentration had minor effect on its growth, but the impact on ArA production was profound, in which the deficiency of nitrogen induced the highest content of ArA. After demonstrating the heterotrophic properties of two algae and the optimal carbon and nitrogen supply level for them, the mixotrophic cultivation was further conducted, which led to significantly increased biomass and target polyunsaturated fatty acids. Finally, the algae obtained from mixotrophic condition were used to feed the Artemia sp.. Results showed that both DHA and ArA can be delivered from the microalgae to the Artemia sp., suggesting the potential as nutrient-enhanced live feed for aquaculture. Findings of the present study provided useful information for the exploitation and utilization of microalgal resources.

Abstract:Black sodier fly larvae meal is a potential high-quality protein source for fish meal replacement in aquaculture, which has attracted much attention in recent years. This experiment, with juvenile Takifugu obscurus with an initial average weight of (16.33±0.34) g, was aimed at evaluating the utilization efficiency of black sodier fly larvae meal in the diet. Four isonitrogenous and isolipid experimental feeds were prepared, with black soldier fly larvae meal as a substitute for fish meal in different proportions(0, 8%, 16% and 24%, designated as HM0, HM8, HM16 and HM24, respectively). Each group was fed to 3 replicate tanks, with 30 fish in each tank. Fish were fed to satiation three times a day. The feeding trial lasted for 56 days. The results showed that the supplementation of black soldier fly larvae meal had no significant effects on the growth, body composition, muscle composition, muscle amino acid composition, muscle texture and serum biochemical indexes of experimental fish. Compared with the control group, the weight gain rate was increased by 19% in group HM16, indicating that the replacement of fish meal with black soldier fly meal at a low level had a potential positive effect on growth performance. Compared with group HM8, HM24 decreased the feed efficiency and tended to increase the HSI and VSI. The high content of C12:0 and C18:2n-6 in black soldier fly larvae meal can meet the energy demand and 18C polyunsaturated fatty acids requirement of fish, which increased the content of C14:0 and n-6 fatty acids in fish. In conclusion, replacement of 24% fish meal in the diet of juvenile Takifugu obscurus by black soldier fly larvae meal did not affect the growth, body composition, muscle texture and health status of obscure puffer. A low replacement level (8%-16%) could have potential positive effects on growth performance and feed utilization of obscure puffer.

Abstract:This experiment was conducted to investigate the effects of different yeast products on growth performance, feed efficiency and liver antioxidant capacity of largemouth bass (Micropterus salmoides). Four isonitrogenous and isolipid diets were formulated by adding yeast hydrolysate (SCH), and yeast hydrolysate without β-glucan (SDG) and yeast culture (DV) as experimental group and without yeast products as control group (CON). Largemouth bass with an initial body mass of (16.24 ±0.02) g were randomly divided into 4 groups with 3 replicates per group at a density of 30 individuals per replicate. Each diet was randomly assigned to triplicate tanks, and the feeding trial lasted for 77 days. The results showed that the supplementation of yeast products had no significant effects on the survival rate and specific growth rate of largemouth bass. Compared with the control group, the supplementation of yeast hydrolysate significantly increased the feed efficiency of largemouth bass, and the supplementation of yeast hydrolysate and yeast hydrolysate without β-glucan significantly increased the apparent digestibility of protein. The supplementation of yeast hydrolysate without β-glucan significantly increased the content of essential amino acids in muscle. The antioxidant capacity analysis showed that the supplementation of yeast hydrolysate significantly decreased the liver malondialdehyde content of largemouth bass, and significantly increased the total superoxide dismutase activity and total antioxidant capacity of largemouth bass. Compared with the control group, the supplementation of yeast hydrolysate and yeast culture significantly increased the lysozyme activity. In conclusion, the supplementation of yeast hydrolysate significantly improves the feed efficiency of largemouth bass, and the supplementation of yeast products can improve the antioxidant capacity and lysozyme activity of largemouth bass to different degrees.

Abstract:In order to explore the effects of pond and paddy culture modes on the intestinal microbiota, immunity and muscle flavor of Eriocheir sinensis, the intestinal flora, immune enzyme activity and muscle free amino acids of Eriocheir sinensis from the same batch of ponds and paddy fields were measured in May and October. The results showed that the dominant intestinal flora of Eriocheir sinensis were Firmicutes, Bacteroidetes, Proteobacteria and Firmicutes. In the case that both season and breeding mode had an effect on the intestinal microbiota of crabs, and the seasonal change had a greater effect on the flora change. From May to October, the richness and diversity of intestinal microbiota of Eriocheir sinensis in paddy field culture showed an increasing trend, but there was no significant change in the richness and diversity of intestinal microbiota in pond culture. The enzyme activities of SOD in May were higher than those in October in the two modes. In October, the immune enzyme activities of LZM and ACP in pond mode were significantly higher than those in paddy field mode. The total sweet amino acid content (TSAA)> total bitter amino acid (TBAA)> total umami amino acid (TUAA) was detected in muscle of all groups. The TSAA and total free amino acid TFAA in muscle of Eriocheir sinensis under pond culture were higher than those under paddy field culture. Therefore, compared with the paddy field culture, Eriocheir sinensis cultured in pond culture mode has more stable intestinal microbiota in terms of time, stronger immune enzyme activities, and better muscle flavor.

Abstract:In order to develop herb compound preparation against Aeromonas veronii pathogenic to Eriocheir sinensis, the present study used A. veronii HXH1 as the indicator strain to screen herbs with good inhibitory activities by tube dilution method, and on this basis, the compatibility of these herbs was optimized by orthogonal t design to make Chinese herbal compound preparation, and the in vitro antibacterial effect of the Chinese herbal compound preparation was further evaluated using tube dilution method. The results indicated that Rhizoma coptidis, Caesalpinia sappan, Radix et rhizoma rhei, Fructus mume, Spatholobi caulis, Punica granatum, and Moslae herba showed highly inhibitory activities against A. veronii, with the minimum inhibitory mass concentrations (MICs) ranging from 7.81 to 31.25 mg/mL against A. veronii HXH1. However, R. et rhizoma rhei, C. sappan and F. mume were found to have negative effects. Thus, R. coptidis, M. herba, C. sappan, P. granatum were chosen as main components of the Chinese herbal compound preparation, and the best compatibility proportion was determined as 5:4:1:2, under which the MIC of the compound preparation was 5.21 mg/mL against A. veronii HXH1. In addition, the Chinese herbal compound preparation exhibited good activities against other A. veronii isolates from E. sinensis, showing the MICs of 3.91 to 7.81 mg/mL against strains HXY1, HXY3, J1Y4, J1Y5, J2Y4, J2Y6, WAB1. This study determined the main components and the best compatibility proportion of herb compound preparation against A. veronii pathogenic to E. sinensis, and can provide a basis for the herb control of diseases in E. sinensis.

Abstract:In this study, we investigated the fish species composition of the Pearl River estuary using environmental DNA (eDNA) metabarcoding. DNA were extracted from water samples collected from 7 sites in Lingding bay of Pearl River estuary and partial sequences of the mitochondrial 12S were amplified. 26 777 effective sequences were obtained in total and the sequences were clustered into 35 OTUs (operational taxonomic units). A total of 35 fish species were identified from 9 orders, 22 families and 29 genera. Among them, 30 species were identified to the species level, and 5 species were only identified to the genus level. 9-31 species were detected separately in 7 sampling sites. Most of the species belongs to Perciformes, with 22 species in total. The vulnerable species (Taeniura meyeni) was detected at sites A and F. By comparing with two similar studies the Pearl River estuary, we found that the difference of the sampling area, sample collection strategy and the molecular marker adopted makes significant differences in the number and composition of the fish species detected. The results show that the environmental DNA metabarcoding technology is suitable for the investigation of fish species composition in Lingding Bay of the Pearl River estuary, which can be used as a supplementary method for the investigation and assessments of fish diversity in the estuary area.

Abstract:The Chongming Island is located at the estuary of the Yangtze River. There are dense rivers and abundant fish resources on the Chongming Island, however, illegal fishing continues despite prohibitions, seriously affecting the level of the fish resources. Besides, fish diversity is an important indicator for aquatic ecology conservation. For evaluating and revealing fish resources and diversity in Chongming Island in Shanghai and reveal fish diversity, a quarterly survey was conducted in 24 sampling sites in the rivers of the Chongming Island from June 2020 to May 2021 which integrated environmental DNA technology and traditional fishing method. In this survey, a total of 78 fish species were detected, covering 13 orders and the Cypriniformes was the dominant species, accounting for 44% of total species found. The annual Shannon-Wiener diversity index calculated based on fish samples was 2.08, and the annual Shannon-Wiener diversity index calculated based on environmental DNA data was 2.96 respectively, indicating that the Chongming Island is rich in fish diversity. The common dominant species identified by the two methods were Parabramis pekinensis, Pseudobrama simoni, Pseudorasbora parva, Rhinogobius giurinus and Acheilognathus macropterus, indicating that the fish community structure in the rivers of Chongming Island is dominated by freshwater fish. The Principal Coordinate Analysis and the PERMANOVA test indicated that there are differences in fish composition between the community of East and West community (R²=0.101 2,P=0.027 6). We suggest that environmental DNA technology should be used as an important supplementary means for the investigation of fish resources and diversity. This study reported the existing status of fish resources and diversity of Chongming Island and provided basic data for rational utilization and conservation of the fish resources on the Chongming Island.

Abstract:To understand the status of biodiversity and community structure of fish assemblage in the Chaohu Lake, fishes were seasonally sampled from July 2017 to December 2018. Sampling was conducted in 9 sites which covered the three main types of fish habitat (estuary, nearshore shallow water area and open water area) in Chaohu Lake. A total of 52 species of fish, belonging to 7 orders and 15 families were collected. Among them, Cyprinidae had the largest number of species, accounting for 63.5%. Compared with historical records, 43 fish species were not captured. A large part of river-sea migratory fishes and river-lake migratory fishes disappeared while the no-native species Taenioides cirratus was newly recorded. Coilia nasus, Neosalanx taihuensis,Hypophthalmichthys molitrix and Aristichthys nobilis were recognized as the dominant species. Cyprinus carpio, Carassius auratus, Culter alburnus and Culter mongolicus were important species, and 22 species, including Paracanthobrama guichenoti and Siniperca chuatsi were rare species. The indicator species of different sampling sites were significantly different. Besides, significant variations of fish composition among sampling seasons and among sampling sites were detected, and fish composition among the sampling sites was more discrete than between the seasons. Analysis of the diversity index indicated that the richness, diversity and evenness of fish community were low. The range of Shannon-Wiener index (H') was 0.56-1.09, Simpson index (D) was 0.25-0.57, Margalef index (d) was 1.45-3.82 and Pielou index (J) was 0.19-0.32. On the temporal scale, the community diversity index in the summer 2018 was higher than that in other seasons. On the spatial scale, the Hangbu River estuary and the nearshore shallow water of east area showed higher community diversity index than other sampling sites. This study supplemented the basic data of fish community in Chaohu Lake and provided the scientific basis for fishery conservation and management.

Abstract:In order to obtain the characteristics of the temporal and spatial distribution of fish in Chenhang Reservoir,Shanghai, dual-frequency identification sonar(DIDSON)was used in fish resource on April 17th, August 15th, and November 13th, 2019. Fish target analysis model for carry out the extraction and counting of fish targets was established by ECHOVIEW underwater acoustic data processing software. To draw the horizontal and vertical distribution maps of fish resources density and further analyze the spatial and temporal distribution of fish quantity in reservoirs.The result showed:The proportion of small and medium-sized fish (length <60 cm) in Chenhang Reservoir was 80.9%; The body length, density, number and total weight of fish in the reservoir increased from spring to autumn; on the horizontal spatial scale, fish mainly gathered in the southern part of the reservoir, with relatively concentrated distribution in summer and relatively scattered in autumn; on the vertical spatial scale, fish in the reservoir area were mainly distributed in water depth between 2-6 m, proportion is 84.85%. The average depth of fish distribution was 3.89 m in spring, 4.34 m in summer, and 5.12 m in autumn,the vertical distribution of fish in the reservoir area tended to move to the bottom with the seasons. The underwater acoustic detection method and fish target analysis model studied provide useful reference for similar fish resource investigation and analysis, and the detection results provide useful assistance for fish stock management.

Abstract:In order to understand the effect of emergency treatment developed by the laboratory on cyanobacteria of bloom in Najiang Reservoir and the water quality changes in the process of treatment, we studied the water quality and phytoplankton structure changes before, during and after the restoration of Nanjiang Reservoir. The results showed that the mass concentration of TN and TP decreased significantly after restoration, and the dominant species changed from the only dominant species Aphanizomenon flos-aquae before restoration to the after restoration:Lyngbya, Aphanizomenon flos-aquae, Oscillatoria princeps, Aphanocapsa and Synedra acus. The density of phytoplankton decreased from (39.2±0.52)×10⁷ cells/L in the early stage to (5.5±0.13)×10⁷ cells/L in the later stage of restoration;the biomass decreased from (24.64±3.25) mg/L before the restoration to (7.97±1.56) mg/L after restoration. Shannon-Wiener diversity index, Pielou evenness index and Margalef richness index were significantly lower in the early stage than in the middle stage (P < 0.05). Redundancy analysis (RDA) showed that water temperature (WT) and total phosphorus (TP) were the main environmental factors affecting phytoplankton, and total phosphorus (TP) was the key factor for outbreak of cyanobacteria bloom. The results above indicate that the emergency treatment can reduce the nutrient salt of nitrogen and phosphorus in water and reduce the chlorophyll content, and the effect of control on cyanobacteria bloom is significant in the short term.

Abstract:Based on fish community monitoring data of 10 sites and water environment monitoring data of 33 sites in the Taihu Lake from 2016 to 2020, the fish community structure and diversity were investigated, as well as their relationship with main water environment factors. A total of 55 fish species were collected in 2020, and the dominant species were Coilia nasus, Carassius auratus and Cyprinus carpio,of which the index of relative importance were 9 219.28, 1698.78 and 1 075.27 respectively. Besides, the proportion of 87.9% fish full length <200 mm, and the proportion of 88.2% fish mass body <50 g. A total of 67 fish species have been collected since 2016, and fish community structure changed greatly although the water quality remains stable. The results showed that there was no significant relationship between fish community diversity index and main water environmental factors and the water discharge of Taihu Lake and the artificial propagation and release were the key factors. Refined fishing program and the artificial propagation and release program of Chinese silver carps and bighead carps should be established based on the water environment situation of Taihu Lake, in order to restore the fish community structure and give play to the potential of the Chinese silver carps and bighead carps in controlling algal bloom.

Abstract:In order to understand the fish community structure in Baiyangdian Lake and its relationship with the environmental factors. 30 sampling stations in Baiyangdian Lake were surveyed in May, August and October, 2019 and August and October, 2020. A total of 30 species of fish were collected, belonging to 12 families and 4 orders, among which Cypriniformes had the most, accounting for 56.67%, and 9 species had Index of relative importance IRI ≥ 500. Carassius auratus, Pseudorasbora parva, and Chanodichthys erythropterus were the dominant species. One-way analysis of variance (ANOVA) showed that the number of individuals, species, Margalef richness index (D), Shannon-Wiener diversity index (H') and Pielou evenness index (J') were significantly different in different months (P<0.05), and except for Pielou evenness index (J'), the other indexex were all the highest in May 2019 based on the SNK-q multiple comparison test. Non-metric multidimensional scaling (NMS) and one-way analysis of similarity (ANOSIM) showed that the composition of fish community overlapped and separated in different seasons (Global R=0.524). Abundance biomass comparison curve (ABC) showed that the fish community in May, August and October 2019 was slightly disturbed, and the fish community in August and October 2020 was moderately disturbed. Redundancy analysis (RDA) showed that water temperature, DO and chlorophyll a were the main environmental factors affecting the fish community in Baiyangdian Lake.

Abstract:The Caizihu Lake line, one of the important water delivery lines of the leading water project from Yangtze River to Huaihe River, was selected as the research object. The pollution level, distribution characteristics and ecological environment risk of 12 kinds of organophosphorus pesticides (organophosphorus pesticides, OPPs) in the water and sediments along the line were tested and analyzed. The results showed that the total concentration of OPPs ranged from 112.8 to 1 781.4 ng/L in the water, mainly in bromophos, carbophenothion, and ethoprophos; and ranged from 290.33 to 13 105.25 ng/g in the sediments, mainly in ethoprophos, sulfotep and chlorfenvinphos. Compared with those in water and sediments from other areas in China, the main types of OPPs pollutants in the Caizihu Lake line are quite different. The results of the ecological risk assessment of OPPs in the water showed that bromophos, carbophenothion, and chlorfenvinphos showed high ecological risks (RQ > 1) in the entire ofCaizihu Lake line, much higher RQ of OPPs risks appeared at C, D, H, and K these four sites (RQ > 10 000), and dichlorvos and sulfotep in most observed sites showed mediμm (0.1 < RQ < 1) or low ecological risk (RQ < 1). The results of this study will not only provide the necessary basic data for the long-term tracking and evaluation of the ecological quality of the water environment along the Yangtze River to the Huaihe River, but also provide a scientific basis for assessing the health risks.

Abstract:In order to understand the factors influencing feeding habit of walleye pollock (Gadus chalcogrammus) in the Western Bering Sea, the stomach contents composition of walleye pollock collected from the western Shelf of the Bering Sea in summer 2019 was analyzed, and the factors influencing stomach contents composition were analyzed using the generalized Dirichlet multiple distribution model (GDM). A total of five zooplankton taxa, i.e. Euphausiacea, Amphipods, Copepods, Chaeteognths, and Crustacean larvae, were identified in the stomach contents of walleye pollock, of which Euphausiacea and Copepods accounted for 85% of the zooplankton. Cannibalism was prevalent in 29% walleye pollock, in which the number of zooplankton in the stomach reduced with increasing of cannibalism, and walleye pollock with standard length over 50 cm almost only preyed on walleye pollock. The results of GDM showed that gonadosomatic index (GSI)and stomach contents weight of walleye pollock had a significant effect on the stomach contents composition. The proportion of Amphipods, Copepods and Euphausiacea in stomach contents of walleye pollock decreased with the increasing of GSI, while it increased with the increasing of stomach contents weight. The results of this study can provide basic data for further study of the food web structure in the Bering Sea.

Abstract:The data weighting for catch per unit effort (CPUE) is essential for integrated fisheries stock assessments. An Age-Structured Assessment Program (ASAP) was developed using fishery-dependent and fishery-independent data of Indian Ocean albacore (Thunnus alalunga). An operating model (OM) was developed to mimic the population dynamics and fishing operations, and estimation models (EMs) based on the Statistical-Catch-At-Age model were used to compare the effect of different CPUE weighting scenarios on the estimation of population attributes.To investigate the confounding impact of misspecification of key model parameters with the CPUE weighting, nine combinations of natural mortality (M) and the steepness (h) of the Beverton-Holt stock-recruit relationship were considered in the EMs. The results showed that when M and h were correctly specified in the EMs, assigning higher weightings on CPUE indices with higher precision or longer time series would lead to better model performance in terms of both median relative errors (REs) and relative root mean square error (RMSE). Meanwhile, putting more weighting on the CPUE indices with higher uncertainty world lead to significantly over-estimated fishing mortality and a low accuracy in spawning stock biomass.Therefore, when using multiple sets of CPUE time series, assigning higher weights to CPUE indices with higher precision or longer time series may improve the accuracy of stock status indicators. Furthermore, the reliability and uncertainty of some key parameters (e.g., M and h) should also be taken into account when weighting CPUE; at least a sensitivity analysis should be conducted to cover possible uncertainty of the model or parameter misspecification and its associated CPUE weighting.

Abstract:This research was aimed to analyze the structural characteristics of the pelagic food web in the tropical eastern Pacific Ocean(14°03'N-30°22'S,179°36'E-114°29'W) using 12 network indices based on the composition of the stomach contents collected from June 2017 to February 2019 by the six Chinese Longline Fisheries Observer Programmes.The results showed that the number of species(S)in the food network was 83, the number of connections (L) was 542, and the mean trophic level (M_T) was 2.4. The proportions of top species, intermediate species,foundation species were 10.85%, 83.13% and 6.02%, respectively. Analysis of the proportion of species at different trophic levels, the omnivory index (O=92.77%), the connectivity complexity index (C_SC=13.22) and the characteristic path length (P=1.85) showed that this food web was in a stable state.The clustering coefficient (C_C=0.242) indicated that closely connected sub-network structures can be formed among species in the food web. Linkage density (D=6.53) and connectivity (C_l=0.08) indicate that the complexity of the food web was at a normal level and it was robust to anthropogenic disturbances and environmental changes.The study can provide scientific reference for further studies on ecosystem dynamics and the ecosystem-based fishery management in the tropical oceanic Pacific Ocean.

Abstract:In order to realize the standardized formulation and application of fishery thematic electronic chart, based on the IHO S-57 international electronic chart standard, this paper analyzes the chart data model and data structure, and according to the main contents and characteristics of fishery thematic information, extends the data set identification field in the data set information record, defines the coding rules of marine fishery thematic electronic chart products. In the category of objects and attributes, fishery thematic objects and thematic attributes are added, and some thematic attribute items (values) are added, so as to design the data structure of fishery thematic electronic chart. The research results will facilitate the integration, sharing and application of marine fishery information, promote the development and production of fishery thematic electronic chart products, and provide standardized information service support for the research and utilization of fishery biological resources, fishery production and management, and marine fishery economic development.

Abstract:The hydrodynamic influence due to large scale suspended aquaculture farm off Gouqi Island, China, was studied, using a 3-dimensional numerical Model (Estuarine Coastal Ocean Model, semi-implicit, Ecom-si). A momentum sink method was used in the model to represent the retarding effect caused by the resistance of aquaculture sleeves. The numerical model was then validated with observed data of tides and flow speed. The model results showed that the existence of suspended mussel sleeves in water reduced the flow speeds, the surfaces currents were reduced by about 80%. At the same time, it increased the tidal current velocity at the edge of the farm throughout the water column.The simulation results of Lagrange particle tracking module showed that it took about 600 hours for the particles to reach the settlement rate of 36.79% (e^-1) when the detritus particles were in suspension state. The particles were distributed in the region of 9.0-10.5 km away from the center of the farm zone without the retarding effect, and that were distributed in the region of 7.5-8.5 km away from the farm center with the retarding effect. When w was greater than 0 m/s, there was little difference between 3 kinds of detritus settlement velocities, and the particle settlement rate reached 99% in about 80 hours. The particle settlement area was within a range of 10.0-13.5 km from the center of the culture area without retarding effect and the particle settlement area was within a range of 6.8-12.0 km from the farm area with the retarding effect. The settlement range of the released particles during the spring tide showed a wider ecological radiation range of detritus than neap tides released. The tidal residual current was the main dynamic factor that determined the detritus transport path and settlement position without considering the drive of wind stress.

Abstract:The antibacterial mechanism of ε-polylysine hydrochloride (ε-PLH) against Shewanella putrefaciens was investigated at the cellular level. The inhibitory effects of ε-PLH against S. putrefaciens were determined by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and microbial growth curve. The permeability and integrity of cell structure were determined by electrical conductivity, propidium iodide (PI)intake, alkaline phosphatase (AKPase), lactate dehydrogenase (LDHase) and adenosine triphosphatase (ATPase) activity, and scanning electron microscope (SEM) was used to evaluate the effect of ε-PLH on the cell structure of S. putrefaciens. The results showed that the MIC and MBC of ε-PLH against S. putrefaciens were 1.0 mg/mL and 2.0 mg/mL respectively. The growth of bacteria was inhibited, the extracellular AKPase and LDHase activities were increased significantly, while the ATPase activity in the cell membrane was decreased. The results of PI intake and electrical conductivity were greatly positively correlated with the concentration of ε-PLH. The results of SEM showed that after ε-PLH treatment, the bacteria presented depression, holes and other phenomena, and the appearance had changed. In conclusion, after ε-PLH treatment, the bacterial cell structure was seriously damaged, the contents leaked, and the bacterial cell shape greatly changed, and led to cell apoptosis finally. The research on the mechanism of ε-PLH against S. putrefaciens can provide the theoretical reference for the application of ε-PLH in aquatic products preservation.

Abstract:Listeria monocytogenes is a psychrophilic bacterium that can grow at low temperatures. The growth of L. monocytogenes in refrigerated ready-to-eat food and frozen food processing equipment is a major food safety issue. Acidic electrolyzed water (AEW) is a new type of high-efficiency, safe and no-residue non-heat sterilization technology. AEW is used to inactivate L. monocytogenes in planktonic state, biofilm state, and frozen Flammulina velutipes samples under low temperature conditions. By detecting changes in the total number of colonies after AEW treatment, biofilm, biofilm structural parameters, and virulence gene expression, we made further analysis of sample tests, etc.. The results showed that when the electrolyte concentration was 0.10% and the treatment time was 1 min and 30 min, the total number of Listeria monocytogenes colonies and the biofilm clearance rate at 4℃ and 37℃ were extremely different. That was, with the same treatment time, AEW was more difficult to inactivate L. monocytogenes cultured at 4℃. Our findings may provide a theoretical basis for evaluating the safety of food and refrigerated food and food processing equipment in the cold chain. The use of antibacterial agents is more demanding.

Abstract:First, this paper defines the definition and classification of recreational fishery.Second, the paper analyzes the present situation of recreational fishery from production scale, growth rate, proportion of annual output value of fishery and industrial structure,then discusses the development opportunities of recreational fishery in terms of policy, economy, culture and technology.Third, the paper analyzes the problem of recreational fishery in terms of the talent, the ability to bear risk, the influence of COVID-19.Finally, the paper discusses the high quality development mode of recreational fishery in China against the background of industrial integration.The research showed:the production scale of recreational fishery increased, the growth rate of recreational fishery declined but higher than the annual output growth rate of the total annual output of the fishery, proportion of annual output value of fishery increased steadily,and the structure of recreational fishery developed steadily, guided by recreational fishing and collecting industry and tourism-oriented recreational fishery, supplemented by fishing tackle, bait ornamental fish, fishery medicine, aquatic equipment, other related industries, ornamental fish industry developed rapidly. At present, recreational fisheries has a series of opportunities such as self-advantages,government policy support, good external economic environment and cultural environment, good facilities and technology. At the same time,recreational fishery facing a series of challenges such as shortage of talents,the ability to bear risk is limited and the shock of COVID-19.Finally, The paper proposes the three-dimensional mode of recreational fishery developing in high quality based on industrial convergence to promote the long-term, steady and high-quality development of recreational fishery.