Abstract:From 2017 to 2018, through intensive adaptive cultivation, water flow stimulation, and water temperature control, the laws of spawning and fertilization of Alosa sapidissima broodstock cultured in earthen ponds were observed and studied. The results showed:The first sexual maturity age of male and female A. sapidissima broodstocks was 2 years, and the breeding season lasted from May to July; The survival rate of intensive adaptive cultivation of A. sapidissima broodstocks was 69.4%-92.9%, prenatal females(ovaryⅤ stage):body length was (34.62±2.90) cm, body weight was (844.11±134.78) g, the condition factor was 2.07%±0.42%, the average weight of ovary was (232.22±73.42) g, the ovary gonadosomatic index (GSI) was 27.59%±6.47% (17.39%-35.20%), the quantity and weight of free eggs in ovarian cavity were (32.26±27.34) thousand and (114.83±73.42) g, respectively. In 2017 and 2018, the spawning period of female lasted 35 d (from May 17 to June 21) and 89 d (from May 4 to July 31), spawning egg amount were 2 779.6 thousand and 4 714.8 thousand, daily spawning egg amount were 81.8 thousand and 53.0 thousand, fertilized egg amount were 185.8 thousand and 744.7 thousand, the average fertility rates were 6.68% and 15.80%, respectively. There were three stages in spawning of A. sapidissima in 2018:spawning steady stage (0-10 day and 30-60 days), spawning peak stage(10-20 days), and spawning stagnation stage (70-90 days). As time (ten-day) goes on, the ten-day average of the daily spawning egg amount presented earlier-increase and later-decrease trend, the ten-day average of fertility rate presented significant bimodal fluctuation trend, and the ten-day average of the daily fertilized egg amount presented weak bimodal fluctuation trend. On the whole, as time (day) goes on, the daily spawning egg amount, the average fertility rate, and the daily fertilized egg amount showed the parabola of the quadratic function with vertices and openings downwards(P<0.01). The suitable water temperature of mating and spawning of A. sapidissima broodstock is 16-20℃; High nutritive value feed is fed during mating and spawning periods; After broodstock laid eggs for 60 days, the spawning regulation ended.

Abstract:In laboratory, Anodonta woodiana(AW)and Corbicula fluminea (CF)were fed with 3 algal species of Microcystis aeruginosa, Chlorella pyrenoidosa and Scenedesmus obliquus, and the effects of algal specie, shellfish body size and density on the feeding rates were studied at approximately 20℃ of water temperature. Three-way analysis of variance (ANOVA) showed that:There was significant difference among three algae in feeding rate for CF but was not for AW; Shellfish body size and density had effects on feeding rate of them; Interaction of body size and density on feeding rate for CF was found, however not observed for AW; The feeding rate of the two shellfishes both decreased significantly with increasing density; The feeding rates of the small-sized individuals were significantly higher than those of large-sized ones for CF reared at 2 relatively low densities and for AW at all three densities; No significant differences in feeding rate were found for CF reared at 2 relatively high densities; The correlation between feeding rate and dissolved oxygen (DO) concentration for CF was obviously higher than that for AW; Shellfish body size and density rather than feeding with different algae influenced the DO in water container. The results showed that the stress degree by low DO might cause the differences between the two shellfishes in interaction of body size and density on their feeding rate and the large-sized individuals of CF are more tolerant of low DO than the small-sized ones.

Abstract:The grazing characteristics of Radix swinhoei on different kinds of submerged plants were studied. According to the grazing experiments of three sizes of large (0. 78 g/ind), medium (0. 28 g/ind), small (0. 06 g/ind) and different densities of low(40 ind/L), medium(80 ind/L), high(120 ind/L) of Radix swinhoei, grazing rate and selectivity of three submerged plants of Elodea nuttallii, Cabomba caroliniana, and Vallisneria natans by R. swinhoei were studied. The results showed that:The total grazing rate of R. swinhoei was inversely proportional to the snail size; The small-sized snail has the highest total grazing rate for submersed plants, reaching (219.66±47.17) mg/(g·d), and the medium-sized snail is (47.53±9.08) mg/(g·d); The grazing rate of large size is the lowest with only (20. 37±14. 60) mg/(g·d). Different densities had no significant difference for the whole grazing rate on submerged plants. The preference of R. swinhoei for the three submerged plants does not change with the size. R. swinhoei with different sizes will preferentially graze E. nuttallii and V. natans, and do not like C. caroliniana. R. swinhoei with the same size and different density will preferentially graze V. natans. The research results are of great significance for rational allocation of aquatic animals, improvement of aquatic ecosystems and enhancement of ecosystem stability in restoration projects.

Abstract:In order to understand the effects of temperature, light, phosphate and their interactions on the growth and chlorophyll fluorescence characteristics of Skeletonema costatum, each environmental factor was set at three levels[Temperature:17,23,29℃; Illumination:80,120,160 μmol photons/(m²·s); Phosphate:0.1,1,10 μmol/L]. Using L18 (3⁷) orthogonal experimental table and considering interactions between two environmental factors. The changes of the chlorophyll a concentration and photosynthetic activity of Skeletonema costatum were studied by indoor culture experiments. The results showed the chlorophyll a peak value of Skeletonema costatum could reach a higher level at 10 μmol/L phosphate concentration. The optimum combination of environmental factors was 23℃, 120 μmol photons/(m²·s) and 10 μmol/L. Phosphate had a significant effect on the chlorophyll a peak value of Skeletonema costatum (P<0.01). Temperature, light and the interaction between environment factors had no significant effect on chlorophyll a peak value (P>0.05). It was found that Skeletonema costatum had higher photosynthetic activity at 10 μmol/L phosphate concentration. But the photosynthetic efficiency α showed no significant difference with phosphate concentration. Light significantly affected the maximum quantum yield F_v/F_m (P<0.05) at 10 μmol/L and 1 μmol/L phosphate concentrations:The F_v/F_m of Skeletonema costatum was higher at 80 and 120 μmol photons/(m²·s) while the phosphate concentration was 10 μmol/L. The F_v/F_m was lower at 120 μmol photons/(m²·s) while the phosphate concentration was 1 μmol/L.

Abstract:Agricultural waste corncob was used as adsorbent to study its adsorption effect on Cu²⁺ in aquaculture wastewater. The effects of pH, water temperature and initial Cu²⁺ concentration on the removal rate of copper ions were studied by single factor experiments. Box-Behnken response surface methodology was used to optimize the design and experiment of the above three factors in order to obtain the best removal conditions. The results of single factor test showed that the three factors all had great influence on removal of Cu²⁺ by corncob, and the order of influence was initial Cu²⁺ mass concentration > temperature > pH. Response surface design analysis showed that the optimal conditions for adsorption of copper ions from wastewater were pH=7, temperature 18.8℃, initial mass concentration 0.4 mg/L. Under these conditions, the removal rate of copper ions was 86.65%, which was close to the theoretical value (88.11%). The regression model has P<0.000 1 and the P value of lack of fit is 0.583 8, which indicates that the regression equation is extremely significant and can be used to analyze the adsorption of copper ions in the cultivation wastewater by corncob.

Abstract:To understand the role of the tidal reach coastal waters of the Yangtze River in subfamily Gobioninae conservation, a stow net was set up along the Jingjiang section to collect 2 or 3 samples each month from 2003 to 2017. The correlation between the abundance dynamics of Gobioninae and the environmental factors was analyzed. 23 668 fish individuals (65.6 kg) of Gobioninae subfamily were collected from 499 sampling times and categorized into 9 genera and 19 species. The subfamily accounted for 14.6% of the total catch quantity, one of the dominant groups in this watershed. The average weight of the subfamily individual was 2.8 g, and most were the juveniles. The Relative Importance Index (IRI) analysis indicated that Pseudorasbora parva, Abbotina rivularis, Squalidus argentatus, and Saurogobio gymnocheilus were commonly found and species S. nitens, S. dunerili, and S. dabryi were general species in this water area. However, the proportion of the subfamily in the total catch varied with seven fold changes in different years. According to the CCA ranking analysis, the high water temperature and lower air pressure led to the increase of 5 species in the group Ⅰ, and the decrease of two species in the group Ⅱ. Spearman analysis showed a significant negative correlation between the abundance of the subfamily and the air pressure (P=0.046 1<0.05). When the turbidity was less than 100 NTU, the abundance of the subfamily was negatively correlated with the turbidity (P=0.009 2<0.01). Altogether, the waters along Jingjiang section are important habitats for the larvae of Gobioninae, and affect their species diversity and quantity with multiple environmental factors.

Abstract:Cephalopods are characterized by their short lifespan and semelparous strategy, in which the growth and development are highly correlated with the hatching seasons that highly influence the alternation of generations. Herein, based on statolith daily growth zones and back calculation of the hatching months, the size attainment of sexual mature Illex argentinus, an important world fishery squid species, was investigated and its relation to hatching months was analyzed using statistical methods. The results showed that:mature females were measured an average mantle length (ML) of (246.59±40.36) mm, an average age of (293.79±32.68) days, and a life history average growth rate of (0.84±0.11) mm/d; Mature males were measured a ML of (222.82±28.60) mm,a average age of (299.24±32.97) days and a life history aveage growth rate of (0.75±0.08) mm/d. Both females and males were estimated hatching months from March to August. As the hatching months progressed, both mature female and male I. argentinus showed a significant decrease in days of age, while they had a higher life history average growth rate. There was a significant relationship between maturity size attainment and life history average growth rate. The effects of hatching months on the attainment of maturity size highly consistent for both female and male I. argentinus, in which the earlier hatched individuals showed slower growth rate, while the later hatched ones grew faster to catch up the maturity size, possibly in order to cope with the coming spawning season. These evidences indicate the growth and development in I. argentinus are significantly related to hatching seasons, and individuals of different hatching months reach their sexual maturity size by adjusting their growth rate, in which later-hatched individuals likely appear to grow faster than earlier-hatched ones.

Abstract:There is not only a gradient pigmentation change in the surface of Dosidicus gigas's beak,but also a significant gradient change of its mechanical behavior. From the rostrum to the wing,the mechanical strength gradually becomes lower but the toughness becomes higher. In this paper,we determined the difference of Young's modulus in different parts of Dosidicusgigas's beaks(rostrum,lateral wall,wing),the main chemical component and the internal molecular cross-linking was determind. The electronic microscope was used to observe the physical structure of the surface and section of different beak's parts. The reasons for the gradient change of the mechanical strength of keratin were discussed. Studies showed that the anhydrous beak has a high Young's modulus,the modulus is not significantly different from the rostrum to the wing (P>0.01),while the hydrated beak's Young's modulus is significantly reduced,the modulus has a Significant gradient change from the rostrum to the wing (P<0.01). The main chemical composition of the beak contains protein, catechol, chitosan and water. The mechanical strength increases with the increasing protein and catechol. The mechanical strength influnces from the internal molecular cross-linking structure and the microscopic physical structure on the surface and section. The internal molecules include:phthalic acid,ethylimidazole,histidine and tyrosine,which are cross-linked to Dopa-multi-cross linked multimers. According to the physical structure,the layered structure of the stalk of the squid is very significant. The stratification is more obvious in the organism and the mechanical strength is greater.

Abstract:In order to study an extraction method using the Beidou position data to extract the operational status characteristics of light shield net fishing vessels, the Beidou position data of the four light shield net fishing vessels of Guibei Fishing 36288, 61999, 62666 and 68209 in 2017 were selected.The threshold comprehensive judgment method is used to judge the state of the light shield net fishing vessels operation, and the ship position of the light shield net fishing vessels operational status is determined by the threshold values of the speed, the water depth, and the time interval. The ship's position analysis software (AST) is used to extract the operating days, the operating date, the operating time, and the corresponding operating position information of the fishing vessels, and compare and verify the actual recorded fishing log data.The results show that:the error between the extracted result and the actual recorded result is small, and the monthly difference in the number of operating days is within 0-3 days; the corresponding operation date accuracy rate is above 94.45%;the maximum daily error of operation time is less than 2.4 h, the minimum error is 0 h, the total average error is 1.49 h, there is a significant difference between the extracted operating time and catch rate, the correlation coefficient is r=0.512(P<0.01); the difference in operating distance is small, and the total is within 50 km.Therefore, it can be determined that the method of extracting the operating state characteristics of the light shield net fishing vessels according to the data of the Beidou vessel position is reliable and has great practicality and practical significance.

Abstract:Distant water fisheriesis the Marine fishery that catches fishery resources in exclusive economic zones of other countries, and also an important part of pelagic fishery. Meanwhile, Distant water fisheries is high risk and high investment marine industry, involving resources, fisheries, policies, exchange rates and other factors. In a certain level, Distant water fisheries is essentially risk investment, and risk assessment is an important link of risk investment. Risk assessment is conducive to the smooth progress of projects and the stable development of industries. Therefore, it is necessary to carry out risk assessment research on Distant water fisheries. Based on the analysis of the characteristics of DWF industry and the theory of risk and early-warning, the principles of selecting risk assessment indicators for DWF are proposed, and the risk assessment system initially constructed. The evaluation system mainly includes risk factor identification and index classification, including three first-level indicators, 16 second-level indicators and 16 third-level indicators. The construction of this evaluation system will be conducive to the healthy, stable and sustainable development of China's pelagic fishery.

Abstract:In order to study the function and effect of staphylococcus aureus nitric oxide synthase, the full-length sequence of the gene was cloned, and the nitric oxide synthase overexpressing strain was constructed based on the nitric oxide synthase gene-deficient strain. Type validation was conducted to study the effect of NO on bacterial phenotype. The results showed that:the loss of nitric oxide synthase accelerated the rate of autolysis of bacteria, decreased the ability of anti-oxidation killing and the biofilm formation, both the loss and overexpression of nitric oxide synthase can affect the normal growth cycle and rate of bacteria. The different effects of exogenous NO on the biofilms of wild strains, knockout strains and overexpressing strains indicate that S. aureus nitric oxide synthase is also involved in the regulation of exogenous NO on biofilms. A series of phenotypic results indicate that the endogenous NO action of S. aureus not only blocks the Fenton reaction, enhances catalase activity, but also acts as a signaling molecule to regulate the transcription and expression of bacterial genes.

Abstract:Temperature is a key factor affecting bacterial growth and inactivation, which often used to control the potential risk of pathogenic microorganisms. However, due to individual differences among bacterial strains, bacteria show different inactivation trends under the same temperature, which is called bacterial inactivation variability. The inactivation variability of 19 Vibrio parahaemolyticus was compared at pasteurization temperature (65℃) and cold chain temperature (10℃), data with the Weibull model were fitted, the inactivation parameters (t_R) were received, and the inactivation variability was explored among the different strains. Under the condition of 65℃, the t_R values of 19 Vibrio parahaemolyticus between 22.62-67.23 s, VPC-1 was the most heat resistant strains, VPC-10 was the least heat resistant strains, the optimum probability distribution of heat inactivation t_R values was Normal (44.82, 12.27). Under the cold inactivation condition of 10℃, the t_R values between 113.95-371.38 h, VPC-3 was the cold resistant strains, VPC-2 was the least cold resistant strains, the optimum probability distribution of cold inactivation t_R values was Loglogistic (51.45, 148.88, 4.67). The results showed that there was no significant correlation between thermal inactivation and cold inactivation of Vibrio parahaemolyticus, the inactivation variability of the bacterial strain was widely existed in Vibrio parahaemolyticus, and the present inactivation model was only based on a single strain, so it was difficult to describe the overall inactivation trend. At the same time, a random model of bacterial inactivation variability was preliminarily constructed, and the traditional inactivation parameters were replaced by the probability distribution.

Abstract:The 85 strains of Vibrio parahaemolyticus harboring the Vibrio parahaemolyticus type Ⅵ secretory system (T6SS) related genes were investigated in this study. The T6SS1⁺ and T6SS1^- strains chosen were analysed in mixed culture to explore their intraspecific competition. The qPCR technology was employed to analyze the expression of related genes of T6SS. The results show that:although all Vibrio parahaemolyticus harbored T6SS2, T6SS1 were found in a certain number of strains, 85 strains of Vibrio parahaemolyticus all carried T6SS2, and 62 strains of Vibrio parahaemolyticus carried T6SS1, of which 41 were clinical isolates, accounting for 93.2% of all clinical isolates; there were 21 environmental isolates, accounting for 51.2% of all environmental isolates, T6SS1 gene clusters were different in Vibrio parahaemolyticus from different sources. Some T6SS1⁺ strains had significant intraspecific competitive advantages, which could suppress the growth of other strains in mixed culture. Compared with monoculture strains, the expression levels of T6SS1 and T6SS2 strains were significantly up-regulated in mixed culture. The reason for this phenomenon might be that strains could strengthen the expression of its related T6SS1 and T6SS2 genes to enhance its competitiveness in the species. The influence of Vibrio parahaemolyticus type Ⅵ secretion system on its intraspecies competition was preliminarily explored, providing scientific reference for further revealing Vibrio parahaemolyticus T6SS function.

Abstract:In order to study the functional role of chitinase in the infection of diatoms by Aeromonas salmonidae,Aeromonas salmonicida and its knockout strain were uesd to be co-culture with diatoms and explore the difference of its function.The results showed that:after 48 hours of co-cultivation of Chaetoceros muelleri with wild strains and knockout strains of Aeromonas salmonicida, the wild strains had a killing rate of 9.18% against Chaetoceros muelleri, while the knockout strains had no significant algae killing Activity; by scanning electron microscopy, it was further found that wild strains of bacteria could lyse the cell wall of Chaetoceros muelleri, but the knockout strains could not. The results confirmed that Aeromonas salmonicida has a killing effect on algae due to its chitinase.

Abstract:In order to make full use of Tetrodontiformes fasciatus resources and enhance the added value, Tetrodontiformes fasciatus skin was used as raw material, through the process of hot water extraction, to prepare fish jelly from the skin of T.fasciatus, and determine the processing parameters of the fish jelly. Base on single-factor experiments of extraction temperature,time and solid-liquid ratio, the collagen recovery and gel strength as indicators, applying response surface methodology to fish jelly rich in collagen and with good gel properties were optimized, and the amino acid composition and content were analyzed. The results showed that time, temperature and solid-liquid ratio had significant effects. Based on the collagen recovery and gel strength, two regression equations were obtained. The determination coefficients R² were 0.959 7 and 0.886 3, respectively. The P value of the missing term was greater than 0.05, indicating that both models were valid. The optimal process conditions were extraction temperature 81℃, solid-liquid ratio 1:3.5 and extraction time 2 h. Results showed collagen recovery 47.62% and gel strength 175.25 g, the composition and content of fish jelly amino acids were consistent with skin, rich in glycine and characteristic amino acid, which could effectively utilize fish skin and retain nutrients. Fish jelly was rich in collagen having good gel properties initially obtained, which provided a theoretical reference for the further development of products from the skin of Tetrodontiformes fasciatus.

Abstract:In order to explore the variation of sea bass quality characteristics and to monitor their shelf life in the logistics process timely during storage at different temperatures, sea bass was stored at -3, 0, 4, 10 and 15℃, respectively. Sensory evaluation, water holding capacity, low-field nuclear magnetic resonance (LF-NMR),texture, microanalysis of back muscle structure, thiobarbituric acid(TBA) value, volatile base nitrogen (TVB-N) value and total colony count (TVC) were examined to verify the relationship between the shelf life and storage temperature. The results showed that the lower the storage temperature, the slower the rate of quality degradation and the longer the shelf life. The sea bass stored at 0℃ could maintain the best quality and structure of tissue fiber, and the flowing water of sea bass stored at various temperatures decreased continuously with the prolongation of storage time. The non-flowing water was gradually transferred from the inside of cells to the clearance between cells and muscle fibers, resulting in an increase of the content of flowing water. The change of water distribution of sea bass meat corresponded to its quality deterioration. The predictive models of TVB-N value and TVC with respect to temperature and storage time were developed based on Arrhenius equation. The model could be used to predict the shelf life of sea bass between -3 and 15℃.

Abstract:Aquatic products, important components in dietary guidelines for Chinese residents, are well known for their multiple amino acids, unsaturated fatty acids, minerals and other nutrients as well as lower fat content. Due to the rich content of water, protein and other components, it is easy to degrade or oxidize proteins and fats in aquatic products under the action of microorganisms and endogenous enzymes, thus reducing the shelf life and commercial value. The modified atmosphere packaging technology, which refers to the technology to improve the storage quality of food and extend its shelf life by using composite packaging materials with high barrier performance and adjusting the gas composition in the food storage environment, is widely used in the field of aquatic products preservation due to its safety and efficiency. This article summarized the application of modified atmosphere packaging technology combined with other preservative methods (low temperature, ultraviolet sterilization, ozone processing, ultra-high pressure, chemical and biological preservatives) and provided theoretical basis for the further application of the combination methods in aquatic products. These methods can effectively extend the shelf life of aquatic products because of reducing of the microbiological and physicochemical indicators such as the total viable counts, total volatile basic nitrogen, trimethylamine nitrogen, and the maintenance of sensory score, water-holding capacity and freshness. In addition, various research directions in further study were prospected especially on the aspects of bacteriostatic mechanism, changing mechanism of physicochemical indexes, packaging materials and models.

Abstract:Remote sensing technology has been widely applied in island identification in recent years, but the automatic identification method for island identification has several problems, such as low precision and poor timeliness. Because of these problems, a method for rapid identification of island by improving deep convolutional neural network (DCNN) was proposed. The improved method contains two aspects. Firstly, adding a 1×1 convolution kernel as the bottleneck unit in the convolutional layer, it reduced the dimension of remote sensing images. Secondly, a resampling method has introduced in the pooling layer to perform feature compression on the target features. Taking 300 scenes of Landsat-8 remote sensing image as an example data, the improved method was compared with CNN model and RCNN model by identifying the islands. The results showed that the improved method reduced the computational time of island identification and improved the accuracy of island identification. Based on the experimental results, the model is more suitable for automatic island identification of remote sensing images.