Abstract:In order to explore the expression characteristics and protein function of vstm2a gene in response to bacterial infection in Cynoglossus semilaevis， in this study， the relative expression characteristics of vstm2a in immune tissues （gill， liver， spleen， intestine and kidney） of Cynoglossus semilaevis after infection with Vibrio harveyi， Vibrio anguillarum， Vibrio alginolyticus， Edwardsiella tardaand Streptococcus agalactiae were detected by real-time fluorescence quantitative PCR （RT-qPCR）. The prokaryotic expression recombinant plasmid of vstm2a gene was constructed and the recombinant protein was obtained. The Oxford cup method， bacterial protein binding experiment and siRNA silencing were used to explore the function of vstm2a protein in bacterial invasion. The results showed that the vstm2a protein had a transmembrane domain and an Ig domain， which functions on the cell surface ；The expression of vstm2a gene in related immune tissues was significantly increased at 6 h， 48 h and 72 h after infection with Vibrio harveyi， Vibrio anguillarum， Vibrio alginolyticus， Edwardsiella tarda and Streptococcus agalactiae. After incubation with bacteria， the vstm2a recombinant protein was co-precipitated with bacteria by low-speed centrifugation. Bacteriostatic experiments showed that it significantly inhibited the growth of bacteria， and after siRNA reducing the vstm2a gene， it inhibited the expression of cytokines IL-6 and IL-10. This study demonstrates that vstm2a protein can respond to bacterial invasion， recognize and bind bacteria， and play an immune defense role against pathogen infection by inhibiting bacterial growth and activating pro-inflammatory cytokines. It is an important immune protein. This study is helpful to analyze the mechanism of bacterial adhesion to cells or fish resistance to bacterial invasion， and provides a theoretical basis for the future selection of resistant varieties by molecular means.

Abstract:To investigate the effects of hypoxia-reoxygenation stress on the survival and antioxidant factors of Macrobrachium rosenbergii larvae， this study subjected them to stress in water with dissolved oxygen concentrations of 1.0， 1.2， and 1.4 mg/L. The survival rates and half lethal concentrations （LC₅₀） at 4， 8， 12， 24， 48， and 72 hours after the onset of stress were measured and estimated； Subsequently， the juvenile M.rosenbergii was replaced in water with a dissolved oxygen concentration of 2.2 mg/L for 72 hours of hypoxia stress. The dissolved oxygen concentration was restored to 6.0 mg/L within 4 hours and 8.4 mg/L within 12 hours. The activity of antioxidant enzymes （SOD， CAT， GSH-PX）， phosphate hydrolases （AKP， ACP）， and malondialdehyde （MDA） content in gills， hepatopancreas， and muscle tissues were measured at 0， 4， 8， 12， 24， 48， and 72 hours of hypoxia stress， as well as at 4 and 12 hours after reoxygenation stress. The results showed that the mortality rate and LC₅₀ value of juvenile M.rosenbergii under three types of hypoxia concentration stress gradually increased with the prolongation of stress time， and the mortality rate was significantly higher at the 12th and 24th hours after hypoxia stress than that at the 4th and 8th hours （P<0.05）. Within 0-72 hours of hypoxia stress， the activities of SOD， CAT， and GSH-PX in the gills， hepatopancreas， and muscle tissues of M.rosenbergii larvae showed a trend of first increasing and then significantly decreasing （P<0.05）， and then significantly increasing again after reoxygenation stress （P<0.05）； After 72 hours of hypoxia stress followed by reoxygenation stress， the activities of AKP and ACP in the liver and pancreas were significantly higher than those in gill and muscle tissues， and the activities of AKP and ACP showed a trend of first significant increase （P<0.05） and then gradually decreasing， and then decreasing and then increasing after reoxygenation； The MDA content in the tissues of gills， hepatopancreas， and muscles showed an initial increase followed by a continuous decrease until it rebounded after reoxygenation； At 12-24 hours of hypoxia stress， significant changes were observed in the activities of SOD， CAT， and GSH-PX in gills， hepatopancreas， and muscle tissues （P<0.05）. In summary， this study preliminarily indicates that both hypoxia and hypoxia reoxygenation stress affect the survival and antioxidant capacity of M.rosenbergii larvae. It was found that the 12-24 hours after hypoxia stress are the key time points for the stress response of M.rosenbergii larvae.The research results will provide a basic theoretical reference for revealing the physiological and biochemical response mechanisms of M.rosenbergii under hypoxia-reoxygenation stress.

Abstract:In order to study the suitable stocking density of out-season E. sinensis marketing in lunar June（Eriocheir sinensis） under pond culture conditions， male juvenile E. sinensis（20.43 ±0.11 g） were divided into three different stocking density groups： 1.5 ind./m² （low density group）， 2.25 ind./m² （medium density group） and 3 ind./m² （high density group）. The growth performance， tissue indices， culture effect and economic profits of out-season E. sinensis marketing in lunar June were compared through a 140-day culture experiment. The results showed that： （1） Since April 15， the average body weight of the low density group was always the highest， the medium density group was the second， and the high density group was the lowest. There were significant differences among the three groups on June 15 and July 5. The total weight gain rate（WGR） of the low density group was slightly higher than that of the medium density group， and both of them were significantly higher than that of the high density group（P<0.05）. The meat yield（MY） of low density group and medium density group was significantly higher than that of high density group（P<0.05）. The total edible yield（TEY） of low density group was significantly higher than that of high density group（P<0.05）. （2） The final average body weight and survival rate（SR） of the low density group were significantly higher than those of the medium and high density groups（P<0.05）， while the yield of the high density group was significantly higher than that of the medium and low density groups（P<0.05）. The feed conversion rate（FCR） and limb loss rate（LLR） of the high density group were significantly higher than those of the low density group（P<0.05）， but there was no significant difference between the high density group and the medium density group（P>0.05）. In terms of size distribution， the proportion of larger-sized male E. sinensis（≥110 g） of low density group was the highest and that of smaller-sized male crab（<100 g） was the lowest. （3） The total cost and total income of the high density group were the highest， the medium density group was the second， and the low density group was the lowest. The differences among them were significant（P<0.05）. The net profit of the high density group was significantly higher than that of the low density group（P<0.05）， and slightly higher than that of the medium density group. The return-on-investment（ROI） is just the opposite. The culture model of out-season E. sinensis marketing in lunar June has the characteristics of short culture cycle， simple production operation， low investment cost and high income. Considering comprehensively， the suitable stocking density of out-season E. sinensis marketing in lunar June is 3 ind./m².

Abstract:To investigate the optimal fishmeal and fish oil replacement levels in grow-out stage snakehead （initial body mass 150 g）， Channa striata， we first explored the optimal fishmeal replacement level by substituting 0%， 17%， 33%， 50%， 67%， and 83% of fishmeal 65 （65%-protein fishmeal） with poultry meal respectively， resulting in six iso-nitrogenous and iso-lipidic experimental diets. The diets were fed to fish to apparent satiation twice daily for 8 weeks. Subsequently， we evaluated the optimal level of fish oil substitution by replacing 0%， 13%， 25%， 38%， 50%， and 63% of fish oil with soy lecithin， resulting in six iso-nitrogenous and iso-lipidic experimental diets. The diets were also fed to fish to apparent satiation twice daily for 8 weeks.Results showed replacing fishmeal 65 with poultry meal had no significant effects on the growth performance， body indices， nutrient apparent digestibility， or body composition of snakehead fish （P>0.05）. Substituting fish oil with soy lecithin did not significantly influence the growth performance， body indices， or body composition of the fish （P>0.05）， nor did it affect the apparent digestibility of dry matter and crude protein （P>0.05）； however， a minor significant reduction in the apparent digestibility of crude lipids （~2%） was observed when fish oil substitution levels reached or exceeded 38% （P<0.05）.Results on growth， feed utilization， and body composition indicate that poultry meal can replace up to 83% of fishmeal 65 and soy lecithin up to 63% of fish oil in diets for grow-out stage snakehead.This study fills the research gap in the substitution of fishmeal and fish oil during the grow-out phase of Channa striata， offering valuable data for optimizing commercial feed composition and reducing costs.

Abstract:To cope with the increasing decline of offshore fishery resources and to provide essential information for spatial-based fishery management， in this study， the spatial distribution and influencing factors of Larimichthys polyactis in the southern waters of Jiangsu Province were examined using an ensemble species distribution model （ESDM） based on the survey conducted during spring and autumn in 2019-2022. Five biotic and abiotic factors were selected to analyze the distribution characteristics of L. polyactis and its relationship with influencing factors. Results showed that the ensemble species distribution model had higher AUC （spring： 0.995±0.002； autumn： 0.985±0.001） and TSS （spring： 0.935±0.038； autumn： 0.903±0.029） values than those in single species distribution models. Sea bottom temperature （0.40） and sea bottom salinity （0.38） had the highest importance levels in spring， while chlorophyll a and prey had greater influences on the spatial distribution of L. polyactis in autumn with importance levels of 0.53 and 0.46. L. polyactis were mainly distributed in coastal areas in spring with a strip-like distribution； while in autumn， L. polyactis were mainly distributed in the offshore areas， with suitable habitat mostly distributed in the areas of 32.5°N-33.6°N， 122°E-122.5°E with a block-like distribution， and the area of suitable area is larger than that in spring. Furthermore， the distribution of L. polyactis showed obvious interannual differences. For example， the range of suitable habitat for L. polyactis in 2021 was prominently smaller than that in other years and the range of distribution was also limited. The study showed that the ESDM had better performance and could better reflect the spatial distribution and influencing factors of L. polyactis； the suitable areas and influencing factors for L. polyactis varied from season to season. This study can provide a theoretical basis for revealing the spatio-temporal distribution and changing law of L. polyactis in this area， and provide basic information for the implementation of space-based fishery management and optimization of marine protected areas （MPAs）.

Abstract:Predicting the abundance and distribution of deep scattering layer is important to indicate the distribution of marine protected animals，important fishing grounds， and develop fishery resources into the scattering layer. This study used the Nautical Area Scattering Coefficient （NASC） as the resource density indicator of the scattering layer， and used K-means clustering and SSA-XGBoost model to predict the resource density of the scattering layer based on multiple environmental factors in the southwestern Indian Ocean. The results showed that the accuracy of the model prediction is 80.51%， the precision is 76%， and the recall is 78%. The sample data matches the high-density spatial distribution of the predicted data， and the application effect of the model is good. By predicting the density of the scattering layer in different seasons in 2011， it was found that the center of gravity in the high-density area of the scattering layer moved from southeast to northwest， with the latitude of the center of gravity being the largest in spring and the smallest in winter. The dispersion of the center of gravity in the southeast-northwest direction is greater than that in the northeast-southwest direction. This study can provide a new method for elucidating the distribution and resource variation patterns of scattering layers in larger spaces.

Abstract:The combined pollution of heavy metals and organic matter in aquaculture water bodies threatens the quality of aquatic products and human health. In this study， aquatic plants from aquaculture ponds were used as raw materials to prepare biochar for adsorption and removal of heavy metal cadmium （Cd²⁺）， polycyclic aromatic hydrocarbons （PAHs） and enrofloxacin （EFX） in aquaculture wastewater. The adsorption effect was assessed by pollutant removal and risk （RQ） reduction， while the elemental composition， specific surface area， apparent morphology， physical phase structure and functional group composition were characterized by scanning electron microscopy （SEM-EDS）， X-ray diffractometry （XRD）， and Fourier Transform Infrared Spectrometry （FTIR）， respectively， and the preliminary adsorption mechanism was carried out in conjunction with adsorption kinetics and isotherm studies. The results showed that the specific surface area of BC500 was large， and C=C， C=O， -COO and -OH were the main functional groups of BC500.The average removal of Cd²⁺， FLU， PHE， FLT， PYR and EFX by BC500 ranged from 54% to 90%， and the RQ value of ecological risk was also reduced from 0.85 to 0.33， indicating the excellent removal performance of BC500 biochar. The results of adsorption kinetics and isothermal model simulation showed that the adsorption of BC500 biochar on the composite pollutants was dominated by the adsorption of chemical monomolecular layer， and there was a competitive adsorption between heavy metal Cd²⁺ and organic pollutants （PAHs and EFX）. In addition， the adsorption mechanisms of BC500 biochar on composite pollutants included oxygenated functional group complexation （Cd²⁺， PAHs， and EFX）， π-π interactions （Cd²⁺， PAHs， and EFX）， ion exchange （Cd²⁺ and EFX）， hydrogen bonding （PAHs and EFX）， and Cd²⁺-EFX complexation.

Abstract:The intestinal microbial composition of fish is closely related to their living environment. In order to investigate the origin of of Coilia nasus and Coilia brachygnathus in Poyang Lake， samples were collected from the the main stream of the Yangtze River， Poyang Lake， the Qingcaosha Reservoir in the Yangtze Estuary and the sea area of Shengsi in different months. The intestinal microorganisms of the samples were comparatively analyzed using 16S rRNA high-throughput sequencing technology.The results showed：（1） among the different sampling groups of C. nasus， the abundance of intestinal microorganisms of the samples from the section of Pengze in March was significantly higher than that of the samples from Poyang Lake， Qingcaosha and Shengsi. The richness of intestinal microorganisms of one group from the in Poyang Lake （PC-4） in April and one group from Qingcaosha had a high similarity with those of the samples from Shengsi （SC-3） through PCoA， suggesting that they may migrate from Shengsi. （2） The intestinal flora of Coilia brachygnathus varied greatly in different regions， while the differences between different months in the same region were smaller. But the intestinal flora in Poyang Lake in May was significantly different from the other sampling groups， indicating that they might have migrated from different places. （3） The average abundance and diversity of the intestinal flora of Coilia brachygnathus in Poyang Lake were higher than those of Coilia nasus in Poyang Lake. The above results demanstrated that there may be migratory populations of both Coilia nasus and Coilia brachygnathus in Poyang Lake.

Abstract:To investigate the effects of light color on the behavior and physiology of juvenile Sebastes schlegelii， the behavioral responses of individuals and populations of Sebastes schlegeliiwere studied under five different light colors. Five color light zones， including white， red， yellow， green， and blue， were set up in the experimental water tank to record the behavioral responses of individuals and populations.At the same time， samples were taken and analyzed for plasma cortisol （COR） concentration， glucose （GLU） content， aspartate aminotransferase （AST） and alanine aminotransferase （ALT） activity at 2， 4， 8， and 12 hours after the start of the experiment.The results showed that Sebastes schlegelii had a certain preference for light color. The proportion of residence time of individual Sebastes schlegelii under different light colors was blue light 22.08%， green light 20.55%， white light 17.59%， yellow light 15.04%， and red light 15.03%， respectively. Blue light was significantly higher than yellow and red light， and there was no significant difference between green light， white light， yellow light， and red light. The aggregation rate of Sebastes schlegeliiin the group was blue light 57.33%， yellow light 15.05%， white light 13.10%， green light 8.49%， and red light 3.89%， respectively. Blue light was significantly higher than the other four light colors， while red light was significantly lower than yellow and white light， and there was no significant difference compared to green light.Both individuals and groups showed a preference （positive trend） for blue light and an avoidance （negative trend） for red light， while their preference for yellow， white， and green light was not significant.There was a significant difference in plasma cortisol concentration among the 5 different light color conditions， with blue light being the lowest， followed by yellow light， white light， and green light， and red light being the highest. There was no significant difference in glucose content in plasma under blue， yellow， and green light conditions， while glucose content was higher under red light conditions. The effects of the five light colors on AST and ALT activity in plasma were not significant.Research showed that the color of light had a certain impact on the behavior and physiology of Sebastes schlegelii， and there was a significant negative correlation between preference selection behavior and stress physiology and metabolic levels. The Sebastes schlegeliiexhibited a preference for blue light in behavior， lower plasma cortisol and glucose levels in physiology， avoidance of red light， and higher plasma cortisol and glucose levels in physiology.

Abstract:To gain a comprehensive understanding of the distribution patterns and physical mechanisms of tidal currents in the adjacent area of Sri Lanka， this study utilized the Finite-volume community ocean model （FVCOM） to establish a detailed three-dimensional barotropic tidal dynamics model. The model was used to simulate and analyze the tidal characteristics of the four major tidal constituents （M₂， S₂， K₁， O₁） within the study area. By comparing the numerical simulation results with tidal gauge data and satellite altimeter harmonic constants， the model's reliability and the feasibility of the simulation scheme were confirmed. Based on the computational results， distribution maps of tides， tidal currents， and tidal energy fluxes for the four major tidal constituents in the adjacent area of Sri Lanka were produced. The study also explored the influence of tidal generating forces on tidal distribution and compared the structural differences between semidiurnal and diurnal tidal systems. The results indicate that the study area is predominantly characterized by regular and irregular semidiurnal tides， with significant contributions from tidal generating forces to the diurnal tides. Systematic differences were observed between semidiurnal and diurnal tides： semidiurnal tides form two counter-rotating tidal wave systems， while diurnal tides form a single counterclockwise tidal wave system； semidiurnal tidal currents are primarily rotational， whereas diurnal tidal currents exhibit reciprocating flow patterns. The mean tidal energy flux showed a distribution trend of higher values in the west and lower values in the east， with semidiurnal tidal energy concentrated on the east and west sides of the Maldives reefs and diurnal tidal energy concentrated near the equator. This study enhances the understanding of tidal characteristics in the Sri Lankan area and， for the first time， examines the impact of tidal generating forceson tidal distribution in this region.

Abstract:Based on the distinct characteristics of sediment particles in South American white shrimp pond tailwater， a hydraulic cyclone separator was devised. Employing Computational Fluid Dynamics （CFD） alongside the Discrete Phase Model （DPM） and the Reynolds Stress Turbulence Model （RSM）， a numerical model for the cyclone separator's three-dimensional two-phase internal flow field was established. Design variables， including overflow port diameter， underflow port diameter， cone angle， overflow pipe insertion depth， and column length， were optimized using an L₁₆（4⁵） parameterized orthogonal optimization experimental model. This model assessed their impact on flow field characteristics and solid particle separation efficiency. Through range analysis， optimal parameter combinations were identified， achieving a balance between reducing pressure drop and enhancing particle separation efficiency. For example， parameters such as an overflow port diameter of 120 mm， an underflow port diameter of 32 mm， a cone angle of 18°， an overflow pipe insertion depth of 160 mm， and a column length of 390 mm resulted in a significant reduction in pressure drop by 9 842 Pa and a 12% increase in separation efficiency. Physical prototypes were fabricated and field-tested， confirming the effectiveness of the proposed methodology. Comparison of water quality characteristics at the cyclone separator's inlet， underflow， and overflow ports revealed negligible relative errors between simulated and experimental particle separation efficiencies， not exceeding 5%. These findings provide a solid basis for optimizing cyclone separators and their application in tailwater treatment in pond aquaculture.

Abstract:The current fishery aquaculture monitoring equipment is low in endurance， high in cost and difficult to be widely used. An autonomous underwater vehicle AUV for fishery moving and fixed-point monitoring is proposed and designed. The AUV adopts a three-body modular structure design， with three Myring shaped cabins distributed in a balanced three-cabin shape to facilitate bottom stabilityand connected by T-brackets to reduce resistance. Considering the resistance interference between the three cabins of the three-body structure， the resistance calculation and design of different cabin spacing are carried out based on the computational fluid dynamics method. With the optimization objective of minimizing the direct navigation resistance， the parametric models of three cabins and the T-shaped bracket are established. The control of the AUV shape is realized by changing the parameters of the bow and stern curve equations of the cabin and the cross-section curve equation of the T-shaped bracket， which in turn leads to the shape optimization design of the AUV. The results show that the T-shaped bracket reduces the direct navigation resistance value by 26.28% compared to the traditional triangular bracket， and the AUV shape optimization reduces the direct navigation resistance value by 24.05%， which improves the endurance. The results of the study provide a new equipment in the field of fishery aquaculture monitoring， as well as a reference for the optimized design of other three-body structure AUVs.

Abstract:In this study， microwave-assisted extraction was used for the isolation of Phragmites rhizoma polysaccharide， its structure was characterized and its immunosuppressive effects in vitro were evaluated. The response surface method was used to optimize the extraction of polysaccharide. The optimal separation conditions of Phragmites rhizoma polysaccharide were microwave power 572 W， microwave time 22 min， liquid-solid ratio 15 mL/g， and the yield of Phragmites rhizoma polysaccharide was 1.61%. The monosaccharide composition of Phragmites rhizomapolysaccharide was arabinose， galactose and glucose， with a molar ratio of 3.03∶0.52∶6.46. Infrared analysis showed that Phragmites rhizoma polysaccharide may contain uronic acid and sulfuric acid groups. Phragmites rhizomapolysaccharide solution is colorless and transparent liquid. Scanning electron microscopy showed that Phragmites rhizoma polysaccharide was smooth and compact， with irregular sheet structure and uneven thickness. Cell analysis showed that 25-300 µg/mLPhragmites rhizoma polysaccharide could significantly improve the cell activity of macrophages and there was no significant difference between the polysaccharide groups and the blank group. 5-200 µg/mLPhragmites rhizoma polysaccharide significantly inhibited nitric oxide production in lipopolysaccharide-stimulated macrophages. 100 µg/mL Phragmites rhizomapolysaccharide significantly inhibited the production of inflammatory cytokines tumor necrosis factor α and interleukin 6 in macrophages stimulated by lipopolysaccharide. Therefore， Phragmites rhizoma polysaccharide may have good immunosuppressive effects.

Abstract:As a significant component of the national economy， the marine fishing industry exerts a certain influence on high-quality economic development， with its excessive carbon emissions impeding resource sustainability and sustained economic growth. Given its substantial impact on global warming and environmental sustainability through notable carbon emissions， the marine fishing industry is inherently linked to the green， low-carbon， circular， and sustainable development model being advanced in the context of high-quality economic development. This paper thus aims to investigate the interrelationship between carbon emission efficiency in China's marine fishing industry and high-quality economic development， providing a foundation for their synergistic advancement. Utilizing panel data from 2010 to 2019 across 11 coastal provinces （municipalities） in China， the study employs the Slack-Based Measure-Data Envelopment Analysis （SBM-DEA） model to analyze carbon emission efficiency， assesses overall economic development quality through an integrated evaluation model， constructs a coupling coordination model to reveal the degree of coupling coordination and regional disparities between the two， and identifies key constraining factors via a barrier degree model. The findings reveal that carbon emission efficiency in the marine fishing industry falls below the DEA efficiency frontier in most coastal regions； there exists uneven development among the primary indicators of high-quality economic development； although the coupling coordination between the marine fishing industry and high-quality economic development has improved， it remains at an intermediate stage overall； major barriers include irrational growth in the industry's output value， insufficient numbers of fisheries extension institutions， inadequate innovation investment， and low technological market activity. The study recommends optimizing resource allocation and technological upgrading， promoting balanced regional development， and comprehensively planning for the synergetic advancement of the marine fishing industry and high-quality economic development， with a particular focus on addressing the four principal challenges of irrational output structure， shortages in fisheries extension institutions， insufficient innovation investment， and lack of technological market vitality.

Abstract:In order to investigate the carbon sink mechanism of marine aquaculture， the carbon sink of shellfish and algae aquaculture was taken as the research object， and four efficiency analysis models were applied to evaluate the carbon sink efficiency of shellfish and algae aquaculture in the coastal areas of China. The results of the study show that among the coastal areas， the shellfish and algae farming process in Liaoning Province not only pays attention to the efficiency value of practical production， but also pays more attention to the realistic degree of the effect of the actual input and output process than other regions， which can bring the "ecological-economic-social" benefits of removable carbon sinks into full play， and has a certain demonstration effect for other regions； In Guangxi， there is a serious imbalance between the scale of labor input and the scale of land input， which corresponds to the input and output of shellfish aquaculture with "high efficiency and low effectiveness"， and the management of its professional practitioners is inefficient； in Hainan Province， the output rate of shellfish carbon sinks is very limited， and the function of carbon sinks generated by shellfish aquaculture makes very little economic， social and ecological contribution to Hainan Province. The economic， social and ecological contribution of shellfish aquaculture to Hainan Province is negligible. In addition， based on the public weighting method of input-output scale， the allocation scheme of the initial CO₂ absorption credit in shellfish aquaculture in China is proposed. The marginal contributions of this paper lie in the following. Firstly， applying the performance-based integrated efficiency model to the measurement of shellfish aquaculture carbon sinks for the first time makes the value of carbon sinks can take account into both efficiency and effectiveness. Secondly， it proposes the carbon absorption quota of shellfish aquaculture carbon sinks from the perspective of input-output scale based on the public weighting approach. Thirdly， it incorporates the efficiency factor into the carbon absorption quota by means of the public weighting approach， and allocates carbon absorption quota with the combination of input-output scale and efficiency. it supplements the new allocation method based on DEA. The research has certain policy significance for the development of fishery carbon sinks in China's coastal areas and the improvement of the carbon trading market mechanism.