Journal of Dalian Fisheries University

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Occurrence and health risk assessment of organophosphate ester flame retardants in fishery products from Honghai Bay

ZENG Yimei, LIU Qi, KE Changliang, DUAN Xingxing, YANG Hongliang, HUANG Ke, GU Xiaoli, ZHANG Ankai, CHEN Jiewen

Journal of Dalian Ocean University. 2024, 39(1): 83-91. https://doi.org/10.16535/j.cnki.dlhyxb.2023-150

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In order to evaluate the quality and safety of fishery products caused by the contamination of organophosphate esters (OPEs), contents of 10 types of OPEs were determined in fishery products including 7 species of fish cultured in cages and 16 species of wild fish collected from fishing ports in Honghai Bay by Gas Chromatography-Tandem Mass Spectrometry (GC-MS/MS). The results showed that the average contents of ∑10OPEs were (55.8±24.2)ng/g (dry weight) in cultured species, significantly higher than those in wild fish (20.5 ng/g±20.6 ng/g, dry weight) (P<0.05). There was significantly higher content of ∑10OPEs in demersal fish (28.4 ng/g±22.6 ng/g, dry weight) than in pelagic fish (7.4 ng/g±4.3 ng/g, dry weight) in the wild fish (P<0.05). Tris (2-butoxyethyl) phosphate (TBOEP), tri-n-butyl phosphate (TNBP), tris (2-chloroisopropyl) phosphate (TCIPP), tris (2-chloroethyl) phosphate (TCEP), and triphenyl phosphate (TPHP) were the organophosphate compounds with the highest frequency detected in the fishery products of Honghai Bay. The composition profiles of OPEs in cultured species were consistent with that in the demersal species, with the maximal levels of TCEP, TBOEP, and TCIPP, while the main OPEs in captured pelagic fishery products were TBOEP, TCIPP, and TPHP, in that order. The results of the exposure assessment showed that the non-carcinogenic risks and carcinogenic risks of OPEs in fishery products in the Honghai Bay for males and females in different age groups were below the potential risk thresholds and the health risks were acceptable to date. The finding indicates that OPEs is prevalent in farmed and wild caught fishery products, and that the level of health risk posed is still within the safe range. However, as the usage of OPEs continues to increase, it is recommended that the contamination of fish products with OPEs be continuously monitored.

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Effects of substrate material and particle size on survival, growth and microbial community of whelk (Babylonia areolata)

HUANG Ruipin, ZHANG Lei, ZHANG Weixiao, LIU Mingyuan, SUI Changrun, WANG Baolong, LIU Ying, ZHANG Qian

Journal of Dalian Ocean University. 2024, 39(1): 57-65. https://doi.org/10.16535/j.cnki.dlhyxb.2023-168

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To explore the appropriate substrate for outdoor cement pond cultivation of whelk (Babylonia areolata), the whelk with body weight of (4.692±1.033)g were reared in a rectangular culture pond of 3.6 m in length×1.4 m in width×1.0 m in height with 12 cm-high plastic screw frame covered with a 245 μm sieve silk mesh at bottom of the pond at stocking density of 480 individuals/m3 at water temperature of (30.2±2.7)℃. Sea sand (group SS), fine ceramsite with particle size of 1.0-2.0 mm (group FC), coarse ceramsite with particle size of 2.0-4.0 mm (group CC) and sea sand (50%)+ coarse ceramsite (50%)mixture (group SS+CC) were disposed on the 245 μm sieve silk mesh at a thickness of 5 cm in the test ponds to investigate effects of substrate material and particle size on the survival and growth of B.areolata, water quality and substrate microbial community. The results showed that there was over 90% of survival rate in B.areolata under the four sediment conditions, without significant difference among groups(P>0.05). The maximal specific weight growth rate was observed in group FC (1.386 4 %/d±0.219 6 %/d), significantly higher than that in groups CC, SS and SS+CC (P<0.05). The structure and composition of microbial community were varied with different substrates, with the minimal richness and diversity in group SS, and higher richness and diversity in group FC. There were higher relative abundances of Proteobacteria, Planctomycetes, Bacteroidetes and Acidobacteriota in group FC at phylum level, with lower relative abundance of Vibrio and higher relative abundance of Exiguobacterium and Halomonas in both group FC and group SS+CC. The fine ceramsite had positive effect on resisting pathogenic Vibrio and preventing water quality deterioration. The results of microbial function prediction indicated an increase in relative abundance of pathways associated with various microbial substance metabolisms in the group FC. Also, the substrate led to affect the water quality during aquaculture, with lower concentration of

in group CC than that in group FC (P<0.05). The findings indicated that utilization of fine ceramsite as the substrate material in outdoor cement ponds for B.areolata cultivation promoted body weight growth, inhibited the growth of pathogenic microorganisms, and contributed to the water purification in aquaculture ponds at certain level.

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Analysis of phytoplankton community characteristics and influencing factors in the Yangtze River Estuary

SHAO Haiyan, WANG Qing, GAO Chunxia, ZHAO Jing

Journal of Dalian Ocean University. 2024, 39(1): 124-133. https://doi.org/10.16535/j.cnki.dlhyxb.2023-171

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In order to understand the composition and structural characteristics, spatiotemporal distribution pattern and key impact drivers of phytoplankton communities in the Yangtze River Estuary, the characteristics of phytoplankton communities and the relationship between the characteristics of phytoplankton communities and influencing factors were explored based on the survey data of phytoplankton in the Yangtze River Estuary in August (summer) and November (autumn) from 2018 to 2020 by community diversity analysis indicators and generalized additive model (GAM). The results showed that a total of 185 species of phytoplankton were collected in 8 phyla, 99 genera, with the dominant species mainly including Skeletonema costatum, Aulacoseira granulata, Melosira sulcata, Cyclotella sp. and Chlamydomonas sp., and the main phytoplankton groups including Bacillariophyta, Cyanophyta and Chlophyta, in which Skeletonema costatum had long been overwhelming. There were significantly higher abundance and species of phytoplankton in summer than those in autumn (P<0.05). In autumn, however, phytoplankton communities showed higher diversity index and richness index and more evenly distributed. Spatially, the average phytoplankton abundance showed the distribution pattern of East Beach >South Branch >North Branch as a whole. The GAM analysis indicated that water temperature (Tem), pH and total nitrogen to total phosphorus ratio (TN/TP) were the environmental factors (P<0.05) significantly affecting the abundance distribution of phytoplankton in the Yangtze River Estuary in summer, with the maximal contribution rate of 71.86% from TN/TP. Salinity (Sal), dissolved oxygen (DO) and chemical oxygen demand (CODMn) were found to be the environmental factors (P<0.05) significantly affecting the abundance distribution of phytoplankton in the Yangtze River Estuary in autumn, especially the DO contribution up to 48.48%. The findings indicate that there are seasonal differences in the community composition, structure, pattern and influencing factors of phytoplankton in the Yangtze River Estuary, which provides references for understanding of the dynamics of phytoplankton resources in the Yangtze River Estuary.

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A review of harvest strategy approaches in fisheries:theory, applications and future challenges

ZHU Jiangfeng

Journal of Dalian Ocean University. 2024, 39(1): 1-8. https://doi.org/10.16535/j.cnki.dlhyxb.2024-037

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Traditional methods of fisheries stock management decision-making have been developed since the 1950s to collect data and assess the status of stock, make scientific management recommendations and implement management measures through management measures. The disadvantage of traditional methods is that stock assessment often has large uncertainties, resulting in management recommendations that also have large uncertainties. Beginning in the 1980s and 1990s, with the development of computer simulation technology, the application of harvest strategy (management procedure) methodology in fisheries management has continued to develop, and has now evolved into a relatively mature and complete set of quantitative fisheries stock management methodology system, and plays an important role in the protection of marine mammals and the development and conservation of economic fish stocks. Comparatively speaking, the harvest strategy approach has been less applied and studied in China. This paper summarizes the basic process of traditional fishery resource management decision-making, as well as the characteristics, advantages and challenges of the harvest strategy approach, and proposes that the application of the harvest strategy is conducive to the scientific management and long-term sustainable use of fishery resources under the premise that specific management measures can be effectively implemented. With regard to fisheries that are considering the use of management strategy evaluation to establish harvest strategies, recommendations for future development are put forward, such as strengthening the collection of basic data on fisheries and population biology, strengthening research on population simulation techniques and capacity-building, and accelerating the development and application of new harvest strategies applicable to severely declining stocks, with a view to providing a reference for China in applying the harvest strategy approach to fisheries management decision-making.

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Research progress on type Ⅵ secretion system (T6SS) and its hemolysin coregulatory protein from pathogenic bacteria in aquatic animals:a review

WU Shuilong, HUANG Yu, WANG Bei, TANG Jufen, CAI Jia, JIAN Jichang

Journal of Dalian Ocean University. 2024, 39(1): 162-171. https://doi.org/10.16535/j.cnki.dlhyxb.2023-095

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Type Ⅵ secretion system (T6SS) as a protein secretion system exists within varieties of gram-negative bacteria,and plays important roles in virulent factors release, biofilm formation, iron ion uptake, vesicular transport and environmental pressure adaptability, which is crucial for the pathogenesis of aquatic bacterial pathogens such as Vibrio parahaemolyticus, V.alginolyticus, V.harveyi, Aeromonas hydrophila, and Edwardsiella tarda. However, the reports regarding the components and functions of T6SS from aquatic pathogenic bacteria are still rare. The latest research progress on biological functions, regulatory mechanisms of T6SS, as well as the biological roles, evolutionary relationships of the key regulator of T6SS-hemolysin coregulatory protein (Hcp) is summarized from several aquatic bacterial pathogens. Several future key directions are proposed including new biofunctional discoveries of T6SS, correlation between T6SS activity and environmental factors, the regulation between T6SS and virulence-related metabolism. This review will help researchers better understand the roles of aquatic animal pathogens T6SS and provide new ideas for further research on pathogenic mechanism and control of bacterial diseases in aquaculture.

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Analysis of denitrification capacity and microbial community of biofilms with different fillers in mariculture wastewater

CHEN Xiaohong, XU Yibin, LIN Yongqing, QIU Denggao, JIANG Shuangcheng, ZHENG Huidong

Journal of Dalian Ocean University. 2024, 39(1): 9-19. https://doi.org/10.16535/j.cnki.dlhyxb.2023-153

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To investigate the nitrogen removal capacity of different filler-biofilms in mariculture tail water, biofilters were constructed by the addition of oyster shells (M), coral stones (S), suspended ball fillers (F), elastic fillers (T), and without any filler as control (C), respectively. The formation speed and the biomass of biofilms as well as the nitrogen removal capacity of the biofilms at 24 hours were compared, while the changes in microbial community structure of the biofilms on biofilters were analyzed using Illumina Miseq high-throughput sequencing technology during biofilms formation period(20th day, 40th day, and 60th day). The different filler-biofilms were found to required 46-50 days for mature, with most rapid formation of the coral stone filler biofilm. Scanning electron microscopy showed that the biofilms on elastic filler and suspended ball filler had more biomasses than the other two fillers, largely consisting of rod-shape bacteria. The analysis of nitrogen removal capacity at 24 hours showed that there was the maximal removal rate of ammonia nitrogen and nitrate nitrogen by suspended ball fillers, and that the maximal removal rate of nitrite nitrogen by coral stone, which were (68.66%±6.27%), (6.73%±3.41%), and (99.99%±0.00%), respectively. The analysis of microbial community diversity revealed that the abundance of bacteria on elastic filler biofilms was increased, while the diversity of bacteria on oyster shell and coral stone biofilms was decreased significantly with the prolongation of biofilms formation time (P<0.05). The dominant microfloras of biofilms with different fillers were shown to be Proteobacteria and Bacteroidetes at the phylum level. The relative abundances of Nitrospirae and Nitrospinae were increased with the extension of biofilms formation time. Nitrosomonas, Nitrospira, Nitrospina and unclassified_Nitrosomonadaceae were the dominant bacteria with nitrification on different filler-biofilms at the genus level. The descending order of relative abundance of nitrifying bacteria at 60th day was described as: suspended ball fillers (42.53%)> oyster shells (30.50%), elastic fillers (29.30%)> coral stones (11.74%)(P<0.05). The relative abundance of denitrification bacteria, such as Pseudomonas, Ralstonia, Chitinophaga and Herbaspirillum, were higher on the biofilms of coral stone than on other filler-biofilms. The findings indicated that coral stone and suspended ball filler as ideal fillers were favorable to enrichment of nitrogen removal bacteria, and had better denitrification ability for mariculture wastewater.

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Analysis of dynamic characteristics of turning movement of juvenile grass golden fish based on PIV technology

ZHANG Juan, ZHANG Ying, HUANG Xiaoshuang, LIU Bilin, CHEN Xinjun, KONG Xianghong, CHEN Jiaqi

Journal of Dalian Ocean University. 2024, 39(1): 92-100. https://doi.org/10.16535/j.cnki.dlhyxb.2023-165

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In order to understand the propulsion mechanism and propulsion performance of ornamental fish in the state of turning motion, the juvenile grass golden fish (Carassius auratus) with body length of 5-8 cm was taken as the research object, and the changes of the fluid flow field of the maneuvering motion were tracked by particle image velocimetry (PIV) and vorticity moment theorem, and the motion characteristics and dynamic characteristics of the tail of the juvenile fish during the turning process were analyzed. The results showed that the morphological structure of the juvenile C-shaped and S+C-shaped mainly changed during the turning process, and the positive and negative vorticities of the flow field around the tail of the juvenile fish appeared alternately during the turning process. When the body morphology of the fish is C-shaped and turned, the average velocity of the juvenile is 0.130 7 m/s, and the positive force of the fluid on the tail of the juvenile fish is 2.06 mN to 133.49 mN, and the negative force is -83.85 mN to -2.15 mN. When the body morphology of the fish is S+C structure, the average velocity of the juvenile is 0.104 4 m/s, and the positive force of the fluid on the tail of the juvenile fish is 24.06 mN to 80.95 mN, and the negative force is -59.60 mN to -5.86 mN. The results show that when turning, the maneuverability of the fish body shape with C-shaped structure change is better than that of fish body shape with S+C structure change, and the time of force peak is different for different turning types.

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Seasonal differences and functional group characteristics of plankton community structure in Cetian Reservoir in Shanxi Province

GENG Zhiyuan, ZHAO Lele, JIA Xin, HU Yafei, LIU Shaozhen, LIU Qing, SONG Jing

Journal of Dalian Ocean University. 2024, 39(1): 101-113. https://doi.org/10.16535/j.cnki.dlhyxb.2023-175

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In order to evaluate the seasonal differences and functional group characteristics of plankton community structure in Cetian Reservoir in Shanxi Province, in the Haihe River, and contribute to reservoir protection and utilization,the characteristics of functional groups of plankton including species composition, biomass, density, spatial and temporal distribution, and their relationships with water environmental factors were investigated and analyzed in samples collected in Cetian Reservoir on October 12, 2020 (autumn), and March 27 (winter), June 21 (spring), and September 2 (summer), 2021. The results showed that 122 species of phytoplankton in 63 genera, 8 phyla, were identified, biomass and density were ranged from 7.31 mg/L to 45.69 mg/L and from 6 500.21 ind./L to 15 183.93 ind./L, with 30 functional groups of phytoplankton, including representative functional groups N, J and W1. A total of 21 species of zooplankton in 13 genera including 4 groups were identified, with biomass ranging from 1.49 mg/L to 25.53 mg/L and density varying from 2 128.90 ind./L to 17 699.72 ind./L. The zooplankton was divided into 9 functional groups, with representative functional groups RF and LCF. The average values of comprehensive trophic status index (TLI) were shown to be 53.45, 40.19, 52.66 and 48.87 in different seasons, with Shannon-Wiener diversity index (H′) of 0.80-1.54 and Pielou evenness index (J) of 0.17-0.32 in phytoplankton and 0.24-1.00 and 0.08-0.32 in zooplankton. There was Margalef index (d) of 12.81-16.18 in phytoplankton and 2.08-2.87 in zooplankton. The Simpson dominance Index (D) was 0.40-0.77 in phytoplankton and 0.10-0.54 in zooplankton. Pearson correlation analysis, Mental correlation analysis and redundancy analysis (RDA) showed that temperature, and contents of dissolved oxygen, phosphorus, nitrogen and chlorophyll a were the most important factors affecting the plankton community structure in Cetian Reservoir. The significant seasonal differences in species composition, functional group structure, biomass and density of plankton were observed in Cetian Reservoir, indicating that the water quality of Cetian Reservoir was in a state of heavy pollution, and that filter-feeding fishes are suggested to be stocked increasingly for control plankton population.

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Research progress on nutritional quality and influencing factors related to nutrients in abalone:a review

WANG Teng, ZHAO Xinnan, LIN Yichen, SONG Dongru, HUO Shanqin, XUE Yong, TAN Zhijun, PENG Jixing

Journal of Dalian Ocean University. 2024, 39(1): 172. https://doi.org/10.16535/j.cnki.dlhyxb.2023-112

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Abalone is a high-quality seafood with high nutritional and economic value, and rich in high-quality protein, amino acids, polysaccharides, polyunsaturated fatty acids, trace elements, and other nutrients and active ingredients. In recent years, with the increasing demand in the consumer market, the abalone industry has developed rapidly, and has become an important pillar of China’s mariculture industry, in addition to a small amount of culture in Liaoning and Guangdong, Fujian and Shandong are the main places of habitat. At this stage, the improvement of nutritional quality and traits has gradually become an important research direction in abalone culture. In this paper, the relevant research on the nutritional quality components of abalone are summarized, including the basic nutrients, flavors, and functional actives, focusing on the effects of factors such as species, origin, sampling season, culture method, diet and exogenous stresses on the nutritional quality of abalone. Due to the large number of factors and indicators of variation, and the lack of standardized criteria for evaluating the nutritional quality of abalone. It is urgent to carry out systematic research on abalone quality evaluation, as well as the control mechanism of abalone quality by diet, environmental factors, culture method, and processing mode, to provide scientific references for abalone culture, cultivation of new varieties, comprehensive evaluation of abalone quality, and mining of characteristic indices.

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Kinetics on effect of Kuroshio axis meander on the resource recruitment of neon flying squid (Ommastrephes bartramii) in the Northwest Pacific Ocean

XU Zhixin, LI Yuesong, PAN Lingzhi, YU We, ZHANG Yu

Journal of Dalian Ocean University. 2024, 39(1): 144-152. https://doi.org/10.16535/j.cnki.dlhyxb.2023-106

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In order to evaluate the effect of physical environment changes caused by the meander of the Kuroshio axis on the resource recruitment of neon flying squid (Ommastrephes bartarmii), the transport distribution and resource recruitment of the early life history stage (70 d) of the winter-spring cohorts of O.bartarmii were simulated in the Northwest Pacific Ocean by the physical model (FVCOM-Global ) coupled with the individual model (IBM). The correlation between the large and small meander paths and the resource recruitment of the squid was judged by using the southernmost point of the center of gravity of the Kuroshio main axis of 140°E in March, which was located south of 32°N. The results showed that there was an interannual fluctuation in the recruitment of the squid in the Northwest Pacific Ocean from 2007 to 2016, which was significantly correlated with the Kuroshio axis meander in March (R2=0.71). In other words, in the year of small meander, the larvae and juveniles of the squid were transported northward or northeastward, north of 25°N and east of 145°E. The higher the proportion of the neon flying squid larvae, and juveniles distributed in this sea area were, the higher the relative recruitment was, with a good positive correlation (R2=0.89). The Kuroshio warm current produced in the process was obvious in the sea area north of 25°N. When the flow rate was 0.2-0.6 m/s, the distribution of larvae and juveniles of the neon flying squid in the sea area was denser at average water temperature of 20.2 ℃ and the northerly isotherm. In the vertical distribution, there was a positive correlation between the vertical distribution and recruitment of different years (R2=0.65). The findings indicated that the meander of the Kuroshio axis in March was one of the key factors affecting the recruitment of neon flying squid resources, which also provides a scientific basis for predicting the abundance of the resources in that year.

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Numerical simulation of concentration distribution characteristics of ecological indicators in Liaodong Bay based on Delft3D model

ZHAO Ziyu, ZHU Xiaosen, WANG Zhuo, ZHANG Mingliang

Journal of Dalian Ocean University. 2024, 39(1): 134-143. https://doi.org/10.16535/j.cnki.dlhyxb.2023-133

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In order to explore the temporal and spatial distribution characteristics and interaction mechanism of chlorophyll a and nutrients in the Liaodong Bay, an ecological dynamic model is established including ecological indicators such as chlorophyll a (Chl-a), dissolved oxygen (DO), ammonia nitrogen

based on the numerical simulation method (Delft3D model), in Liaodong Bay based on Delft3D model. The accuracy of the model was verified, and then the spatial-temporal changes and distribution of ecological indicator concentrations including Chl-a in the Liaodong Bay waters were analyzed. The results showed that there were obvious spatial and temporal distribution characteristics of the ecological index concentrations in the Liaodong Bay. A trend of autumn (4.83 μg/L) >summer (4.13 μg/L) >spring (3.39 μg/L) in the concentration of Chl-a was observed, spring (9.41 mg/L) >summer (7.26 mg/L) >autumn (5.84 mg/L) in concentration of

was found, spring (0.76 mg/L) >autumn (0.56 mg/L) >summer (0.50 mg/L) in concentration of DO was occurred, spring (0.039 mg/L) >autumn (0.030 mg/L) >summer (0.026 mg/L) in the concentration of

was found and autumn (0.025 mg/L) >summer (0.020 mg/L) >spring (0.018 mg/L) in concentration of

was observed. In terms of spatial distribution, the high concentration distribution of Chl-a,

(spring and summer) and

(spring and summer) was found in the northeast Liaodong Bay and low in the southwest Liaodong Bay, and the concentration of

was high at the bayhead and baymouth and low in the middle. It was found that the important factors affecting the temporal and spatial distribution of ecological index concentrations were of Liao River and Daliao River at the upper basin of Liaodong Bay, with the relative limitation of phosphorus as nutrient limitation in the Liaodong Bay.

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Complex relation extraction from health aquaculture standards based on an improved BiRTE model

SONG Qishu, YU Hong, QIAO Shihan, LUO Xuan, LI Guangyu, SHAO Liming, ZHANG Sijia

Journal of Dalian Ocean University. 2024, 39(1): 153-161. https://doi.org/10.16535/j.cnki.dlhyxb.2023-201

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A complex relationship extraction method for health aquaculture standards is proposed to address issues such as inaccurate recognition of domain-specific nouns and the complexity of semantics hindering entity relationship extraction based on an improved BiRTE model. The BiRTE model, which reduces error propagation through bidirectional extraction and exhibits strong relationship extraction capabilities, was adopted as the foundational model. To enhance the model’s information-extracting ability from texts of fisheries standard files, RoBERTa was used as the encoder encoding domain-specific nouns in fisheries standard files using whole-word masking and dynamic masking, enriching word vector information and enhancing feature representation. Thus, the Self-Attention is integrated to combine entity features and relationship features, focusing on strengthening the connection between entity extraction and relation prediction, thereby improving the accuracy of relation extraction. It was found that the proposed model achieved precision of 95.9%, recall of 95.4%, and F1 scores of 95.7% from the extraction of complex relationships in fisheries standards, representing an improvement of 4.2%, 3.1%, and 3.8%, respectively, compared to the original model. The finding indicates that the proposed improved BiRTE-based model, as an effective method for extracting complex relationships in fishing standards, can effectively address the problems of inaccurate identification of proper nouns and difficulty in extracting entity relationships due to semantic complexity in the field of fishing standard text relation extraction.

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Correlation between otolith structure and early growth of Gymnocypris przewalskii larvae and juveniles

WANG Yang, FANG Di’an, KUANG Zhen, TAN Longfei, LIANG Yidong, LUO Hui, QI Hongfang, XU Dongpo

Journal of Dalian Ocean University. 2024, 39(1): 20-28. https://doi.org/10.16535/j.cnki.dlhyxb.2023-102

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In order to clarify relationship between structure of otolith and early growth characteristics in larval and juvenile Gymnocypris przewalskii, the microstructural characteristics was observed and the appearance time of the first rings and deposition pattern of the otolith rings were comparatively identified in larval otolith of cultured and wild G.przewalskii from artificial breeding and collected from Shaliu River (37°18′50.93″ N, 100°08′6.86″ E) and Quanji River (37°14′7.10″ N, 99°53′3.78″ E), the migratory spawning tributaries of Qinghai Lake. The otolith deposition was observed in the larvae and juveniles exposed to 10, 15, and 20 ℃ in temperature marking test and the correlations between the otolith daily age, width of otolith marking rings and daily age were fitted. It was found that the deposition of otolith diurnal cycle is daily. The larval fish daily age was calculated by the otolith rings number plus 1 (N+1). The daily age and sampling date revealed that the larvae and juveniles collected in Shaliu River in 2020 were incubated from June 5th to August 14th, peak in mid-July and early August. The larvae and juveniles in Quanji River were incubated from June 27th to August 3rd, the peak period in the mid-July. The results above were basically consistent with the fish larvae appearance time found in field investigation. The total length of larval and juvenile had significant linear, correlated with daily age, the otoliths length had significant linear correlated with fish total length with the maximal correlation coefficient in the artificially cultivated larvae and juveniles at water temperature of 15 ℃. The fitted equation was shown to be LT=0.167 2t+10.377(R2=0.689 0, P<0.001). The otolith growth of the larvae and juvenile was greatly affected by the environmental factors, and the variation of otolith deposition was closely related to the growth and development of larvae and juveniles.

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Effects of bacterium-alga synergism on aquatic environment, growth and immunoenzymatic activities in largemouth bass (Micropterus salmoides) culture

ZENG Tianyu, CHEN Xi, XU Huimin, MENG Shunlong, JIN Yuqin, HU Gengdong, LI Dandan, QIU Liping, SONG Chao, FAN Limin, XU Pao

Journal of Dalian Ocean University. 2024, 39(1): 29-37. https://doi.org/10.16535/j.cnki.dlhyxb.2023-219

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In order to explore the effects of addition of green alga (Chlorella vulgaris), bacterium (Bacillus subtilis) and mixture of C.vulgaris and B.subtilis on aquatic environment, growth performance and related enzyme activities of largemouth bass (Micropterus salmoides), juvenile largemouth bass with body weight of (11.71±0.90)g was reared in a 1 000 L polyethylene barrel filled with 800 L water added with C.vulgaris (density of 1×109 cells/L at 6.25 mL/L)(alga group), B.subtilis (1×1011 CFU/g at 0.75 mg/L) (bacterium group), both C.vulgaris and B.subtilis (bacterium + alga mixture group), and blank (without any bacterium and alga, control group for days). The results showed that there were generally optimised physical and chemical indices in the water environment in the alga group and bacterium group during the experiment, compared with the blank group, with the relatively small differences in the total nitrogen, total phosphorus and dissolved oxygen contents in each experimental group, while there were considerably varied in the contents of ammonia nitrogen, nitrate nitrogen and nitrite nitrogen, especially in the water environment in the bacterium + alga mixed group, with the minimal ammonia nitrogen, nitrate nitrogen and nitrite nitrogen contents in water in most time points (P<0.05). At the end of the experiment, the largemouth bass in all experimental groups had increase in body weight, weight gain rate, and specific growth rate compared with the blank group, with significant differences in only the bacterium + alga mixture group compared with the blank group (P<0.05). The hepatic glutathione (GSH) content, and activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and lysozyme (LZM) in general were shown to be significantly increased (P<0.05), and malondialdehyde (MDA) content to be significantly decreased (P<0.05), especially in the bacterium + alga mixture group compared with the blank group. To sum up, it can be seen that addition of either C.vulgaris or B.subtilis to the water environment can improve the water quality, promote the growth and hepatic antioxidant capacity and immunity in largemouth bass, and addition of both the green alga and bacterium at the same time is more effective.

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Expression characteristics of CgLOX4 gene in larval development of Pacific oyster (Crassostrea gigas)

HU Yue, LENG Jinyuan, SUN Jiejie, WANG Lingling, SONG Linsheng

Journal of Dalian Ocean University. 2024, 39(1): 38-47. https://doi.org/10.16535/j.cnki.dlhyxb.2023-120

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To analyze the expression characteristics of CgLOX4 during larval development, the full-length cDNA sequence of LOX4 was amplified from Pacific oyster (Crassostrea gigas) by using PCR, and the expression characteristics of CgLOX4 in different stages of larval development were further analyzed by qRT-PCR and whole-mount immunofluorescence experiments. It was found that the CgLOX4 gene had full-length cDNA sequence of 1 862 bp with an open reading frame of 834 bp encoding 277 amino acids, with the isoelectric point of 8.36. The amino acid sequence of CgLOX4 gene contained a conserved HOX domain, and CgLOX4 gene was expressed in all the tested tissues of adult oyster, with significantly higher expression level in the adductor muscle than that in hepatopancreas, gills, hemolymph, gonad and labial palps tissue (P<0.05). CgLOX4 was expressed in all the examined early embryos, with relatively high expression level in fertilized eggs, and four-cells. The whole-mount immunofluorescence assay revealed that the positive signals of LOX4 were mainly distributed in the shell field of trochophore, the visceral mass of D-shape larvae and the digestive gland of umbo larvae. The findings indicate that CgLOX4 gene is one of the transcription factors activated earlier in the early development process of the oyster, and may play an important role in regulating the formation of larval shell and digestive organ.

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SSR, SNP and InDel locus characteristics analysis in Gymnocypris eckloni based on transcriptome sequencing

HE Caixia, LI Changzhong, JIN Wenjie, BAO Changhong, JIAN Shenglong, LI Zhaonan, WANG Linan, YAN Qingchun, WANG Zhenji, WANG Guojie, CHEN Yanxia

Journal of Dalian Ocean University. 2024, 39(1): 48-56. https://doi.org/10.16535/j.cnki.dlhyxb.2023-164

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In order to utilize molecular markers for large-scale development and marker-assisted selection in breeding of Gymnocypris eckloni, the transcriptome was sequenced by Illumina Novaseq 2000 platform, and the SSR, SNP and InDel loci were analyzed using MISA and GATK3 software in gill, kidney, and liver of G.eckloni, after total RNA extraction and cDNA library construction. The results showed that a total of 128 727 SSR were found in 486 221 Unigenes, with a frequency of 26.47% and an average of one SSR per 3.76 kb; There were six repeat types in G.eckloni SSR, among which mononucleotide and dinucleotide were dominant, accounting for 46.53% and 42.45% of the total number of SSR loci, respectively. The total number of repeat motif types was 77, among which the frequency of the two motifs, A/T and AC/GT, were the most frequent, and they were the dominant repeat motifs in the SSRs of G.eckloni; Among all the repeats, the number of repeats between 5 and 15 was the largest, accounting for 87.52% of all SSR loci. In addition, 399 080 SNP loci were obtained by GATK3 software, and the transitions types were more than the transversion types, accounting for 56.29% and 43.71% of the total SNPs, respectively. The distribution frequency of A/G was slightly higher than C/T in the transition type, while the frequency of A/T was the highest and that of C/G was the lowest in the transversion type. The analysis showed that a total of 254 065 InDel loci were identified from the transcriptome of G.eckloni, with an average of one InDel locus per 1 903 bp. The largest number of unigenes was found in both SNP and InDel loci, and the unigenes containing one locus of SNP and InDel were the largest. The SSR, SNP and InDel loci were shown to be abundant in the transcriptome of G.eckloni, and the findings will be of great value for the identification of germplasm resources, population genetics and conservation management of the G.eckloni in the future.

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Isolation, identification and biological characteristics of Bacillus licheniformis from the intestine of Pacific white leg shrimp (Litopenaeus vannamei)

XU Zhenquan, HAN Guowei, REN Jing, ZHANG Zixuan, SUN Jingfeng, HAN Zhuoran

Journal of Dalian Ocean University. 2024, 39(1): 74-82. https://doi.org/10.16535/j.cnki.dlhyxb.2023-137

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In order to screen strains with potential prebiotic effects on Pacific white leg shrimp (Litopenaeus vannamei), a strain (RHVJ) with high temperature (80 ℃) tolerance was isolated from the intestine of healthy Pacific white leg shrimp with body weight of (3.1±0.4)g, and identified by morphological observations, physiological and biochemical determination, and gene sequence alignment. The strain RHVJ was detected for pathogen antagonism, safety, tolerance analysis, and growth characteristics. The results showed that RHVJ was a gram-positive Bacillus, and tentatively identified as a Bacillus based on physiological and biochemical characteristics. The 16S rDNA sequence of RHVJ was found to be completely matched with Bacillus licheniformis strains MH305331.1 and NR074923.1, and its gyrB sequence also showed 100% consistency with CP038186.1 and CP023729.1. The strain RHVJ was identified as Bacillus licheniformis, inhibited the growth of Vibrio parahaemolyticus and Aeromonas veronii, and not pathogenic to Pacific white leg shrimp based on physiological and biochemical identification results. When cultured in environments with bile salt concentrations ranging from 0 to 1.2 g/L and pH levels between 3 and 11, and subjected to water bath treatments at temperatures from 37 to 90 ℃ for either 5 or 15 minutes, the RHVJ strain demonstrated sustained proliferation. It exhibited optimal growth under conditions of 27 ℃, pH 7, and 20 salinity. The B.licheniformis RHVJ from the intestine of Pacific white leg shrimp had good environmental adaptability and safety, as well as some ability to antagonize pathogenic bacteria, and were used as a candidate strain for the development of probiotics. The findings laid the foundation for its application in prawn culture.

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Spatial and temporal distribution of chlorophyll a concentration and eutrophication evaluation in the middle reaches of Huaihe River

HE Licong, WANG Dongwei, ZHANG Minying, ZHOU Yanfeng

Journal of Dalian Ocean University. 2024, 39(1): 114-123. https://doi.org/10.16535/j.cnki.dlhyxb.2023-140

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In order to explore the spatial and temporal distribution characteristics and influencing factors of chlorophyll a (Chl-a) concentration and eutrophication in the middle reaches (from mouth of the Honghe River to the exit of Hongze Lake) of the Huaihe River, water quality was investigated in 28 sampling sections in the middle reaches of the Huaihe River in June 2019, September 2019 and February 2020, and the relationship between the spatial and temporal distribution of Chl-a and environmental factors were analyzed by principal component analysis and multiple linear stepwise regression analysis. The results showed that there was obvious spatial and temporal distribution characteristics of concentration of Chl-a in the middle reaches of the Huaihe River, with the annual mean value of (20.12±7.25)μg/L, with the variation range from 2.97 μg/L to 80.61 μg/L. The descending order of the spatial variation was expressed as Linhuaigang Sluice >from Linhuaigang Sluice to Bengbu Sluice >under Bengbu Sluice. Principal component analysis showed that Chl-a concentrations on Linhuaigang Sluice were positively correlated with transparency and dissolved oxygen level (P<0.05), but negatively correlated with nitrous nitrogen (P<0.05), and Chl-a concentrations from Linhuaigang Sluice to Bengbu sluice were significantly positively correlated with dissolved oxygen concentration and pH value (P<0.05), and Chl-a concentrations under Bengbu Sluice were positively correlated with permanganate index and total phosphorus (P<0.05). The multiple linear stepwise regression analysis revealed that pH, total phosphorus and total nitrogen were the main environmental factors affecting the concentration of Chl-a in the middle reaches of Huaihe River, pH being the passive factor for the change in Chl-a concentrations. There were obvious differences in the correlation between total nitrogen and concentration in different hydrological periods, and total phosphorus concentration was the limiting nutritional factors of phytoplankton in the middle reaches of Huaihe River. The water in the middle reaches of the Huaihe River was dominated by mild eutrophication, and the temporal and spatial variation characteristics of the comprehensive trophic status index (TLI) were similar to the changes in Chl-a concentration. The Linhuaigang Sluice and the confluence of the main stream of the Huaihe River with the Yinghe River and the Wuhe River were the main mutation points of water quality change. It was found that the total nitrogen concentration mainly exceeded the standard in the middle reaches of Huaihe River, and the changes in the hydrological situation of the river caused by dams, tributary inflows and non-point source pollution were the main influencing factors causing the change in the TLI.

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Effects of air exposure and recovery on antioxidant capacity, apoptosis and immune related gene expression in coelomocytes of sea urchin (Strongylocentrotus intermedius)

LIN Weigang, SUN Qi, HAI Hangyu, LIU Yating, ZHAO Peng, CHANG Yaqing, MA Deyou

Journal of Dalian Ocean University. 2024, 39(1): 66-73. https://doi.org/10.16535/j.cnki.dlhyxb.2023-118

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To evaluate the effect of air exposure transportation on the survival of sea urchin (Strongylocentrotus intermedius), the total superoxide dismutase (T-SOD) activity, malondialdehyde (MDA) content and total antioxidant capacity (T-AOC) were determined during 12, 24 and 36 h air exposure stress and subsequent 12 h recovery, and apoptosis was detected by flow cytometry, and the expression levels of lysozyme gene LYZ, TLR1, Caspase-3 and Caspase-9 in coelomocytes were investigated using real-time quantitative PCR. The main results showed that the T-SOD activity, MDA content, and T-AOC level generally increased first and then decreased during exposure to air, with the maximum values observed at 12 h air exposure stress and no significant differences between control and 12 recovery (P>0.05). Air exposure had significant effects on the expression of immune related genes LYZ and TLR1, reaching the maximum values at 24 and 36 h of air exposure, which were significantly higher than those in other stress groups (P<0.05). Their expression levels after 12 h recovery following exposure times 36 h were also significantly different from those in controls (P<0.05). It was identified that the change trend of apoptosis rates was similar to that of the T-AOC levels, reaching the maximum value at 12 h air exposure. However, the expression levels of Caspase-3 and Caspase-9 genes presented significant differences between control and time intervals (P<0.05), with the maximum values observed at 24 h and 36 h of air exposure, respectively, suggesting response of the two important apoptosis-related Caspases had time cumulative effect. These findings indicated that sea urchins S.intermedius have certain ability on air exposure tolerance, using antioxidant enzyme system to conserve the dynamic balance of reactive oxygen species (ROS). Innate immune molecules such as lysozyme and TLR1, as well as Caspase dependent apoptosis, play important roles in maintaining homeostasis in response to air exposure stress.

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An information extraction method from offshore aquaculture area based on spatial transformation and shuffle attention mechanism

WU Tongren, ZHANG Xian, LIU Pei, WEN Tingting , ZOU Zhenxue

Journal of Dalian Ocean University. 2024, 39(2): 327-336. https://doi.org/10.16535/j.cnki.dlhyxb.2023-230

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In order to solve the problem of low accuracy in extracting aquaculture areas using remote sensing technology due to complex background of onshore aquaculture and offshore cage culture areas and to easily disturbed by factors including houses, vegetation, seawater, and ships, a complex deep learning method that combines shuffle attention mechanisms and spatial transformation network was proposed, and tested in Bamen bay in Wenchang city and Potou Port in Wanning City. With the help of GF-2 high resolution remotely sensed data, the prior knowledge of aquaculture targets was constructed using spectral and texture features. Then, based on the U-Net model, the spatial transformation network (STN) and the shuffle attention (SA) mechanism are combined to enhance the spatial characteristics of the aquaculture area and to reduce the interference of complex backgrounds. The test results showed that the overall accuracy and mean intersection over union of SA-STN-Net model were enhanced by 3.3% and 5.7% compared with the preliminary U-Net model, respectively. Swin-Transformer, Dc-Swin, and F1 score of SA-STN-Net model were found to be increased by 6.7%, 4.2% and 7.2% in the score compared with the most state-of-art deep learn model such as A2fpn, respectively. The findings demonstrate that the proposed SA-STN-Net model is adapted to the complex environmental background of offshore aquaculture, effectively extracts offshore aquaculture targets, and can provide technical support for offshore planning and management departments.

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Revelation of green development of aquaculture industry in China from foreign provision of aquaculture tailwater discharge: a review

MA Xiaona, ZHAI Tangfang, WU Ziheng, LIU Zishuo, YANG Yuxiang, FENG Zhihua, LIU Ying

Journal of Dalian Ocean University. 2024, 39(2): 337-348. https://doi.org/10.16535/j.cnki.dlhyxb.2023-159

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The provision of aquaculture tailwater discharge in some major foreign countries and international organizations at the national level (Global Aquaculture Alliance,United States, European Union, Norway, France, Japan, Australia and World Bank)are summarized, and the current status of aquaculture wastewater discharge standards in China is examined. The requirements for wastewater discharge in aquaculture are analyzed and compared between China and other countries. It is found that foreign countries place more emphasis on process management including BMP management and permit systems, focusing on reducing pollutant emissions at the source. In terms of pollution control modes, foreign countries often adopt a combination of concentration control and total load control, while domestic approaches tend to focus on concentration control alone. In terms of pollution control parameters, in addition to the five main pollutants controlled in China (suspended solids, pH value, COD, nitrogen, and phosphorus nutrients), foreign countries also pay more attention to pollutants such as dissolved oxygen, coliform bacteria, and oil substances. There are also differences in pollutant emission concentration limits between domestic and foreign countries: the primary discharge standard is slightly higher than the standards of most foreign countries, while the secondary standard is lower than international standards. Furthermore, present paper offers insights and recommendations for the development of domestic standards for aquaculture wastewater discharge from three aspects: strengthening source control, improving process monitoring, and innovating end-of-pipe treatment, aiming to provide scientific reference for researchers and management departments and to promote the healthy and sustainable development of aquaculture industry in China.

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Research progress on the interaction between lipid and protein oxidation in aquatic products and its impact on their quality: a review

ZHAO Yangmeijin, LIN Xu, LI Yuxi, ZHANG Bincheng, CUI Wenhao, HE Yuxuan, WU Fangbing, JIANG Yusheng, ZHAO Hui, LU Hang

Journal of Dalian Ocean University. 2024, 39(2): 360. https://doi.org/10.16535/j.cnki.dlhyxb.2023-204

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The fragile structure and high moisture content of aquatic product make them susceptible to quality deterioration, in which oxidation is one of the main causes of aquatic product quality deterioration, during transportation, processing and storage. It has been found that both lipid and protein in aquatic product can be oxidized, and the two interact with each other, but their interaction mechanisms and effects on the quality of aquatic product are unclear. In this paper, the oxidation mechanism of lipid and protein, their interactions and their effects on aquatic product quality are summarized, and suggestions for future development are made for research on the oxidation mechanism of aquatic product, research on the interactions between protein and lipid, and research and development of oxidation control technology, with a view to providing scientific reference for a deeper understanding of the mechanism of changes in the quality of aquatic product and the improvement of aquatic product freshness preservation technology.

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YOLOv8 blood parrot object detection and tracking method with dual-layer routing attention mechanism

LI Penglong, ZHANG Shengmao, SHEN Lie, FAN Wei, GU Jiahui, ZOU Guohua

Journal of Dalian Ocean University. 2024, 39(2): 318-326. https://doi.org/10.16535/j.cnki.dlhyxb.2023-206

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In order to detect the behavior and health status of hybrid ornamental fish (Vieja synspila♀×Amphilophus citrinellus♂), a target detection model called YOLOv8n-BiFormer with a dual-layer routing attention mechanism was designed. In this method a dual-layer routing attention mechanism is added into the YOLOv8n model to reduce computation and memory requirements, and a new visual universal transformer called BiFormer is introduced to the YOLOv8n model for improvement of computational efficiency. The ByteTrack algorithm is employed to track the motion trajectory of the fish blood parrot. The results showed that the YOLOv8n-BiFormer model had a detection accuracy of 99.2%, a recall rate of 93.7%, and an average precision of 99.1% (mAP@0.5) for the blood parrot, increased by 0.8%, 1.4%, and 1.0% compared to the YOLOv8n model, respectively. The model demonstrated good performance in the detection and tracking of the cichlid (Chindongo demasoni) in an aquarium, with a detection accuracy of 97.0%, a recall rate of 93.4%, and an average precision of 96.5%, increase by 1.8% in recall rate and 1.9% in average precision compared to the YOLOv8n model. The finding demonstrates that the designed YOLOv8n-BiFormer model performs excellently in detecting and tracking blood parrot fish and cichlid targets, with fewer computational resources, and that can be deployed in aquarium monitoring systems, providing feasible solution for the automation and intelligence of ornamental fish information recording.

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Research progress on effect of brown alga polysaccharides on regulation mechanism of intestinal microecology: a review

ZHANG Jin, WANG Shangzhi, YANG Mingrui, YAN Bin

Journal of Dalian Ocean University. 2024, 39(2): 349-359. https://doi.org/10.16535/j.cnki.dlhyxb.2023-148

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Intestinal tract as the largest immune organ in a body is used to maintain the health, but the imbalance of intestinal microecology is easy to cause metabolic disorders, immunosuppression, inflammatory bowel disease, viral infection and even tissue canceration. Polysaccharides derived from brown algae can be used as exogenous prebiotics by protecting intestinal barrier, activating intestinal immunity, regulating intestinal flora and changing the composition of metabolites, so as to maintain the health of the body. In this paper, the effects of chemical composition and structural characterization of brown alga polysaccharides on intestinal microecology and mechanism of action were reviewed. Some suggestions for future development were put forward, such as improving the yield and purity of fucoidan, and further research on the structure-activity relationship and mechanism of fucoidan to provide reference for the development and application of brown alga polysaccharides.

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Cloning, expression and role in ovarian development of Spo11 gene in Malaysian prawn (Macrobrachium rosenbergii)

YANG Yanhao, WANG Rui, LI Liping, RUAN Zhide, HUANG Binsheng, LU Zhifa, YANG Mingwei, LIN Yong

Journal of Dalian Ocean University. 2024, 39(2): 193-202. https://doi.org/10.16535/j.cnki.dlhyxb.2024-036

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In order to investigate the regulatory role of meiotic protein covalently bound to DSB homolog (MrSpo11) in ovarian development of Malaysian prawn (Macrobrachium rosenbergii), the molecular characteristics, encoded amino acid, tissue expression, distribution and biological function of MrSpo11 gene were investigated in Malaysian prawn by RACE technique, fluorescence quantitative PCR, in situ hybridization and RNA interference. The results showed that the MrSpo11 cDNA sequence had total length of 2 298 bp, with the 5′end non-coding region of 457 bp, the 3′ end non-coding region of 701 bp, and the open reading frame of 1 140 bp encoding 379 amino acid residues. There was the maximal relative expression level of MrSpo11 gene in gill, higher level in ovary, hepatopancreas and heart, and slightly expression level in brain, eye and muscle. The maximal relative expression level of MrSpo11 gene was observed in stage Ⅰ of ovarian development, followed by stage Ⅲ, and the minimal level in stage Ⅱ and stage Ⅳ. MrSpo11 gene was showed to be expressed in the cytoplasm of pre-vitellogenesis, mid-vitellogenesis and late vitellogenesis oocytes and in the cytoplasm and nucleus of early vitellogenesis oocytes. The expression of MrSpo11 gene was decreased in experimental group by 45.8% and 11.6% on 2nd and 4th day after dsRNA injection, respectively, compared with control group, with slightly lower ovarian development maturity in the experimental group than that in the control group in 4 days of injection, indicating that MrSpo11 gene is involved in the ovarian development. The finding lays a foundation for further research on the molecular regulation mechanism of ovarian development of Malaysian prawn.

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Development and application of a real-time fluorescence recombinase- aided amplification method for detection of Anguillid herpesvirus

CHEN Xi, YANG Jinxian, GE Junqing

Journal of Dalian Ocean University. 2024, 39(2): 234-240. https://doi.org/10.16535/j.cnki.dlhyxb.2023-216

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In order to establish a real-time fluorescence recombinase-aided amplification (RAA) method for detection of Anguillid herpesvirus (AngHV), a primer pair and probe targeting ORF95 sequence of AngHV was designed, followed by optimizing the reaction temperature and fixing the reaction time. The results showed that the established real-time fluorescence RAA had optimal reaction temperature of 39 ℃, with the reaction time of 20 min. The further evaluation of sensitivity, specificity, and repeatability showed that the detection method had the minimum AngHV detection concentration of 1×102 copies/μL and had high specificity on AngHV, and showed no cross amplification reaction with American eel adomavirus(AEAdoV), Rana grylio virus(RGV), Koi herpesvirus(KHV), and White spot syndrome virus (WSSV). There was less than 5% of co-efficiency of variation within and between groups for the method which was then applied to analyse 25 collected samples. It was found that the detection rate of the real-time fluorescence RAA was consistent with that by qPCR of 92%, but much higer than PCR with the detection rate of 76%. These results revealed that the established RAA method for detection of AngHV was rapid, sensitive, reliable, and accurate, which is used for rapid clinical detection and conducting epidemiological investigations on AngHV.

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Analysis of fish community structure and ecological niche changes in Miyun Reservoir based on environmental DNA technology

QU Jiangqi, HAO Tongfeng, LI Yonggang, LIU Lumin, HAO Dongsheng, JIA Chengxia, ZHANG Qingjing

Journal of Dalian Ocean University. 2024, 39(2): 298-307. https://doi.org/10.16535/j.cnki.dlhyxb.2023-132

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In order to investigate the impact of the newly-formed aquatic environment after South-to-North water storage on fish communities, the spatio-temporal changes in fish community structure and diversity were analyzed in fish samples collected in the Miyun Reservoir Conservation Area in May and September 2022 by environmental DNA metabarcoding technology for the first time. The response process of the interaction, coexistence, and niche differentiation of fish populations was investigated by Shannon-Winner ecological niche width and Pianka niche overlap indices. The results showed that a total of 86 fish OTUs belonging to 14 orders, 21 families, and 68 genera were detected in the reservoir, with 3 fish species only annotated at the genus level. Fish mainly inhabited the bottom of the water column (61.63%), with dominant carnivorous (43.02%) and omnivorous (26.74%) feeding types. The PCoA results showed that there were no significant differences in fish community structure and in various indices of alpha diversity among the sampling points (P>0.05). The main ecological niche width of fish species was found to be ranged from 1.15 to 9.25, and all intermediate and broad niche species. There were 517 pairs of species with an ecological niche overlap index (Qik) of >0.6, accounting for 14.15% of the total pairs. Comparison of historical data revealed that silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), crucian carp (Carassius auratus), bluntnose black bream (Megalobrama amblycephala), and common carp (Cyprinus carpio) were still dominant species in the reservoir. After water storage, fish species that lived mainly on the bottom, with a carnivorous or herbivorous diet, had weaker adaptation to the environment, and there was obvious competition between them.

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Analysis of genetic diversity and genetic structure of Portuguese oyster (Crassostrea angulata ) from the coast of Fujian Province

ZHANG Yuting, WU Zhen, LI Cong, CHEN Huorong, HUANG Zekun, HE Shuiqing, ZHANG Zhi, MU Jingli

Journal of Dalian Ocean University. 2024, 39(2): 275-280. https://doi.org/10.16535/j.cnki.dlhyxb.2023-214

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In order to investigate genetic diversity and genetic structure of Portuguese oyster (Crassostrea angulata) from the coast of Fujian Province, China, 373 samples of the Portuguese oyster were collected from the coastal areas of Fuqing, Putian, Quanzhou and Dongshan in Fujian Province were sampled, and 62 out of the 373 oyster was identified as C.angulata based on their mitochondrial COⅠ sequences, accounting for 16.6%. Then, the genetic diversity, variation and population structure of these C.angulata were analyzed by the genotyping-by-sequencing (GBS) technology. Results showed that the heterozygosity (Ho) value ranged from 0.243 to 0.271, with the maximal Ho value of 0.271 in the Dongshan population, and the minimal Ho value of 0.243 in the Fuqing population. The Fst value among the 4 populations ranged from 0.021 0 to 0.036 8 with the maximal Fst value of 0.036 8 between the Dongshan and Quanzhou populations. In addition, the result of the genetic structure analysis showed that samples from the Dongshan population were separated from others (the Fuqing, Putian and Quanzhou populations), indicating that there was a low genetic diversity and potential germplasm recession of C.angulata in the coast of Fujian Province and a geographic isolation between the Dongshan population and the other three populations.

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Digging the chemokine receptors-encoding genes and analyzing the relative protein sequences of a Halomonas strain

XU Shuang, LI Chen, JIANG Jialin, XIE Xiaochen, WANG Bo, HUO Zhongming, FANG Lei

Journal of Dalian Ocean University. 2024, 39(2): 203-214. https://doi.org/10.16535/j.cnki.dlhyxb.2023-222

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With an attempt to understand the chemotaxis of Halomonas sp.7T, a pathogenic bacterium to Pacific oyster (Crassostrea gigas), its chemotaxis was investigated by capillary tube method and the holo-genome sequencing data were utilized to analyze its chemosensory signaling pathway. Genes involved in chemotaxis were predicted and the chemosensory pathway of 7T was analyzed using KEGG Pathway. The chemokine receptors-encoding genes were dug out and sequences of the relative proteins were analyzed. The chemokine receptors were further grouped via aligning and comparing with the homologues, and structures of MCPs (methyl-accepting chemotaxis proteins) were analyzed through incorporating MeMe database and TMHMM analysis. The results showed that chemotaxis was observed in Halomonas sp.7T. Across its genome, complete signaling pathways existed and there were 22 MCPs-encoding genes, covering the 5 kinds of most conventioal MCPs. Signal transduction domains were predicted in the 22 MCPs. Additionally, 19 MCPs harbored the trans-membrane domain whereas 3 did not. Based on the differences in the heptapeptide repetitive sequences, the 22 MCPs were further classified into different groups. Seventeen MCPs belonged to the group of 36H and 1 MCP was in the groups of 40H, whereas the other 4 MCPs were not categorized into any known group. Additionally, 20 of the 22 MCPs harbored trans-membrane domains conforming to topology, among which 10 were grouped to Class Ⅰ, 4 to Class Ⅱ, 3 to Class Ⅲ, and 3 to Class Ⅳ. The results showed that chemotaxis was observed in Halomonas sp.7T, a bacterial strain pathogenic to Crossostrea gigas. Complete chemosensory signaling pathways existed in its genome. In total, 22 genes encoded methyl-accepting chemotaxis proteins, which were of specific structural characteristics and might be involved in mediating chemotactic behaviours crucial to the existence as well as responses to environmental stresses of the bacterial strain.

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Effects of acute low salt stress on survival, gill structure and hepatic antioxidant capacity of juvenile bluefin leatherjacket (Thamnaconus septentrionalis)

CHEN Ying, LI Fenghui, ZHANG Guangming, BIAN Li, CHEN Siqing, ZHANG Ziyang, ZHANG Yuao, YAN Junli

Journal of Dalian Ocean University. 2024, 39(2): 250-258. https://doi.org/10.16535/j.cnki.dlhyxb.2023-205

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To probe into the physiological and biochemical response mechanisms of juvenile bluefin leatherjacket (Thamnaconus septentrionalis) under low-salt stress, survival, gill histological structure, gill filament Na+/K+-ATPase activity, and hepatic antioxidant capacity were determined in juvenile bluefin leatherjacket with body weight of (20±5)g exposed to acute salinity of 15, 20, 25 and 30 (control group 30) for 24, 48, 72, and 96 h. The results showed that the survival of the juveniles was significantly affected by salinity below 20 (P<0.05), without significant effect at salinity of 25 and 30. The juvenile bluefin leatherjacket had median lethal salinity (LC50 ) of 5.649 for 24 h, 7.058 for 48 h, 10.041 for 72 h, and 10.260 for 96 h. Compared to control group 30, the gill of the juvenile in salinity 25 group was shown to be slight lamellae curvature, terminal expansion, and cell vacuolization, while gill in salinity 20 and 15 groups showed varying degrees of gill lamellae curvature and coarseness, irregular arrangement, basal hyperplasia and fusion, as well as increase in number of mitochondria-rich cells, cell vacuolization, and rupture of epithelial cells. There were significantly higher Na+/K+-ATPase activity and hepatic antioxidant capacity in salinity 20 and 15 groups than those in control group (P<0.05), with the maximal points in most of the biochemical indices of enzyme activities at 72 h and decrease at 96 h, without significant difference in other enzyme activities in salinity 25 group at 96 h compared to control group, except for GSH-PX activity, anti-superoxide anion capacity and inhibition of hydroxyl radical capacity (P>0.05). The findings indicated that the salinity of 25-30 was suitable for the juvenile, and that the juvenile experienced a series of stress reactions at salinity of below 25, with different extents of adaptive changes including activity of gill filament Na+/K+-ATPase, and the antioxidant capacity in liver.

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Role of Asb14a gene in intermuscular bone development in zebrafish (Danio rerio)

NIU Minghui, WANG Huamin, HU Ruiqin, HU Peng, WU Zhichao, CHEN Liangbiao

Journal of Dalian Ocean University. 2024, 39(2): 259-265. https://doi.org/10.16535/j.cnki.dlhyxb.2023-173

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In order to further probe the molecular mechanism of intermuscular bone development, the development of intermuscular bone was investigated in zebrafish (Danio rerio) in which Asb14a gene was knockouted by CRISPR/Cas9 targeting technology, alizarin red staining and real-time fluorescence quantitative PCR. The results showed that the homozygous zebrafish lines with 2 bp insertion and 50 bp deletion of Asb14a gene were successfully constructed in present study. Alizarin red staining test indicated that the number of intermuscular bones in adult Asb14a-/- mutants was found to be decreased by 35% compared with wild zebrafish (P<0.000 1), implying that the knockout of Asb14a gene affected the formation of intermuscular bones in zebrafish. Real-time PCR analysis revealed that the expression levels of most bone development-related genes (bmp6, sp7, sox6, alpl, collala, sox6 and smad1) in Asb14a-/-mutants were changed significantly, verifying the association between Asb14a gene and intermuscular bone development from a molecular perspective. The findings indicate that Asb14a gene plays an important role in the development of intermuscular bone in zebrafish. This discovery provides crucial clues for further investigating the molecular mechanisms underlying the development of intermuscular bones.

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Response of intestinal microbiome of Gymnocypris przewalskiito different salinity stresses

ZHAO Zifeng, JIN Wenjie, ZHAO Jing, WANG Rong, QI Hongfang, LI Jin, BAI Peng, LI Changzhong

Journal of Dalian Ocean University. 2024, 39(2): 225-233. https://doi.org/10.16535/j.cnki.dlhyxb.2023-213

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In order to explore the effect of salinity stress on the structure of the intestinal flora of Gymnocypris przewalskii, microbial sequencing and information analysis of the intestinal contents of G.przewalskii at different salinity (0, 5, 10, 15) were based on the three-generation full-length 16S amplicon sequencing technology. The relative abundance of the intestinal flora of G.przewalskii differed in different salinity groups, with higher relative abundance of Fusobacteria and Proteobacteria, followed by Firmicutes and Bacteroidetes, in the intestinal flora in the control group (salinity 0) and in the low-salinity group (salinity 5, 10). Verrucomicrobia, Actinobacteria and Planctomycetes were also represented. Proteobacteria, Bacteroidetes, Planctomycetes and Verrucomicrobia were the dominant flora in the high-salinity group (salinity 15). At genus level, the relative abundance of Cetobacterium and Aeromonas followed by Vibrio and Shewanella was higher in the intestinal flora in the control and low-salinity groups, while Vibrio, Pseudorhodobacter and Haloferula were the dominant flora in the high-salinity group. The findings indicated that low-salinity (salinity ≤10) stress had little effect on the structure of the intestinal flora of G.przewalskii, whereas high-salinity (salinity≥15) stress inhibited and had a greater effect on the growth of the intestinal flora and dominant flora of G.przewalskii.

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Structural differences in intestinal microbiota of Chinese sea bass (Lateolabrax maculatus) in different growth stages

LIANG Zuluan, ZHAO Jichen, LIAO Minze, SUN Chengbo

Journal of Dalian Ocean University. 2024, 39(2): 215-224. https://doi.org/10.16535/j.cnki.dlhyxb.2023-186

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In order to investigate the microbial composition of intestine and aquaculture environment of Chinese sea bass (Lateolabrax maculatus) at different growth stages, 16S rDNA gene sequence data were analyzed for microbiota in intestine of 3-month-old with body weight of (79.89±14.97)g (small size group), 6-month-old with body weight of (212.67±30.32)g (middle size group), and 9-month-old with body weight of (427.56±69.56)g (large size group) Chinese sea bass and aquaculture water and pond sediments. The results showed that there were significant differences in the structure of intestinal microbial and environmental microbial communities in Chinese sea bass at different ages, while there was no significant difference in environmental microorganisms community structure at different growth stages (P>0.05). Cyanobium_PCC-6307 as a differential species in environmental microorganisms showed a negatively correlation with nitrate nitrogen levels. Analysis of intestinal microbiota revealed that the abundance of Firmicutes was lower in the intestines of 3-month-old and 6-month-old Chinese sea bass than that in 9-month-old Chinese sea bass at the phylum level. At the genus level, there was higher abundance of Cetobacterium promoting sugar utilization in the intestines of 3-month-old and 6-month-old Chinese sea bass than that in 9-month-old Chinese sea bass. There was the maximal differences contribution in Romboutsia at the genus level. The findings indicated that there is no significant difference in the microbial community structure of the environment at different breeding stages, but there was significant difference in the intestinal microbial community structure among Chinese sea bass at different months of age, the intestinal microbiota of Chinese sea bass was influenced by aquaculture environmental.

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Comparison of feeding habits of jumbo flying squid (Dosidicus gigas) under different climate conditions in the eastern equatorial Pacific Ocean

ZHU Ting, GONG Yi, LI Yunkai, GAO Xiaodi, ZHANG Jiaxu

Journal of Dalian Ocean University. 2024, 39(2): 308-317. https://doi.org/10.16535/j.cnki.dlhyxb.2023-183

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In order to comprehend the potential effects of abnormal climate changes on feeding behavior of jumbo flying squid, Dosidicus gigas, items and amounts of stomach content were determined in jumbo flying squid D.gigas collected in June and July of 2017 Normal period and July and August of 2020 La Ni

a period in the eastern equatorial Pacific Ocean by morphological methods and DNA barcoding technology. The results showed that Vinciguerria lucetia, Diogenichthys laternatus, Pteropods and Cephalopods were the main dominant preys of jumbo flying squid in the two climate modes. During the normal climatic period, Sternoptyx diaphana and Dosinia spp. were also consumed by jumbo flying squid, while during the La Ni

a period, Triphoturus mexicanus and Clio pyramidata were included. The Amundsen’s Diagram revealed that the jumbo flying squid has extensive feeding, exhibiting a high within-phenotype component (WPC) type. The Shannon diversity index indicated a higher diversity level in the diet composition of jumbo flying squid during Normal period compared to the La Ni

a period. Non-Metric Multidimensional Scale (NMDS) analysis indicated the significant differences in the feeding habits of jumbo flying squid between the two periods and the preys in La Ni

a period were more generalized. The GII chord diagram and SIMPER similarity results highlighted the S.diaphana and Dosinia spp. as the main contributors to the feeding differences under different climate modes. The significance of constructing a detailed food web was emphasized in the eastern equatorial Pacific Ocean and significance of investigating its energy flow pathway. The findings highlighted that La Ni

a event can significantly impact the feeding behavior of feeding habits of jumbo flying squid under different climate change.

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Establishment and application of a method for rapid detection ofCitrobacter freundii by recombinase polymerase amplification (RPA) combined with lateral flow strips (LFD)

WANG Shuran, FAN Houyong, XU Jianan, ZHOU Tianqi, XU Dan, ZHENG Yueping

Journal of Dalian Ocean University. 2024, 39(2): 241-249. https://doi.org/10.16535/j.cnki.dlhyxb.2023-200

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In order to establish a rapid detection method for Citrobacter freundii based on recombinase polymerase amplification (RPA) technology, the specific RPA primers were designed based on the conserved sequence of the cfa gene of C.freundii, the reaction conditions were optimized, and the specificity and sensitivity were evaluated by recombinase polymerase amplification (RPA) combined with agarose gel electrophoresis (AGE) and lateral flow chromatography (LFD). The results showed that C. freundii was detected within 20 min of amplification at 38 ℃ by the established RPA-LFD rapid detection method, with the minimum limit of detection (LOD) of the C.freundii pure culture and genomic DNA of 1.5×102 CFU/mL and 200 fg/μL by RPA-LFD method, 100 times higher sensitivity than that by conventional PCR (cfa primer). The consistent results were observed when sturgeon hybrid infected with C.freundii clinical samples was simultaneously detected using both the established RPA-LFD and conventional PCR methods. The research indicated that the RPA-LFD method for C.freundii established in this study is simple, rapid, specific and sensitive, and does not require expensive instrumentation, which can provide more effective technical support for the early diagnosis of bacterial diseases caused by C.freundii in the future.

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Analysis of immune priming phenomenon in sea urchin (Strongylocentrotus intermedius) induced by Vibrio echinoideorum

YIN Weijun, LIU Yansong, TIAN Wenzhuo, OU Fanjiang, LIU Lei, DING Jun, ZHANG Weijie, CHANG Yaqing

Journal of Dalian Ocean University. 2024, 39(2): 266-274. https://doi.org/10.16535/j.cnki.dlhyxb.2023-196

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To investigate whether immune priming exists in sea urchin (Strongylocentrotus intermedius), twice infection with Vibrio echinoideorum was conducted. Differences in immune parameters such as phagocytic amoebocyte density, red spherule cell density, phagocytic rate, phagocytic index, acid phosphatase activity (ACP), reactive oxygen species (ROS) content, and total antioxidant capacity (T-AOC) between the two time infections were compared. Difference in survival rate post challenge between immune priming group and control group were also compared. The results showed that the total coelomocytes cell density, phagocyte density, ACP, ROS and T-AOC in the induced immune priming group increased significantly after the second infections (P<0.05), and the response time to the maximum was 36, 36, 84, 12 and 36 h earlier respectively, and the peak values were significantly higher than those in the first infection (P<0.05). The phagocytosis rate was significantly higher in the induced priming group (45.41%±6.39%) than that in the control group (33.17%±1.94%) at 6 h post infection. The survival rate was significantly higher in the induced immune priming group (43.33%±10.00%) than that in the uninduced positive control group (7.78%±10.71%) (P<0.05). The findings indicate that low concentrations of V.echinoideorum can induce immune priming in the sea urchin, which provides new ideas for prevention and control of diseases in sea urchin.

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Characteristics of flow field in a large-scale circular aquaculture tank under action of submersible thrusters

WU Yanfei, FENG Dejun, QU Jiangqi, JIA Chengxia, GUI Fukun, ZHANG Qingjing

Journal of Dalian Ocean University. 2024, 39(2): 289-297. https://doi.org/10.16535/j.cnki.dlhyxb.2023-207

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In order to investigate the hydrodynamic characteristics of a large-scale circular aquaculture tank under the action of submersible thrusters, the effects of number submersible thrusters (n=2, 4) on the flow field distributions in different water layers (h=1.5, 2.0, 2.5 m) of a large-scale circular tank were determined in situ by using the acoustic doppler current profiler (ADCP) system developed for unmanned vessels. The results showed that the flow velocities at the edge of the tanks in the 1.5, 2.0, and 2.5 m water layers were about 0.4, 0.3, and 0.1 m/s, respectively, the flow velocities at the edge of the tanks in the 1.5, 2.0, and 2.5 m water layers were about 0.6, 0.4, and 0.3 m/s in the tank with 4 thruster, respectively, with gradual decrease in the flow velocities with the distance of the edge of the tanks from the tank centre in the horizontal direction, and the flow velocities in gradual decrease with the increase in the water layer depth in the vertical direction. The average flow velocity distributions characteristics of flow field distribution showed that rotational flows were generated in the aquaculture tanks regardless of two or four thrusters were disposed, but the high flow velocities were only found at the edge of the tanks, with gradual decrease in the flow velocity with the increase in water layer depth. The mean flow velocity distribution showed that no matter two or four thrusters to push the flow, rotating flow was generated in the aquaculture tank, with the high flow velocity only near the edge of the tank and close to 0 of the flow velocity near the centre of the tank, thus resulting in difficulty of the pollutants removal outfall in the centre of the tank. It was shown that the number of thrusters was closely involved in the flow field distribution characteristics of different water layers, with increase in the average flow velocity of different water layers in the aquaculture tank with the increase in the number of thrusters from n=2 to n=4. More obvious flow field zoning phenomenon from the centre to the wall of the tanks was observed in the circular aquaculture tanks, and the high flow velocity area was distributed near the wall of the aquaculture tanks’ surface layer. There were circulating currents only in the edge of the large circular aquaculture tanks and smaller circulating currents in the middle tanks under the initial hydrodynamic conditions and certain number of thrusters. The results of this study can provide a reference basis for the improvement of submersible thruster deployments in large-scale circular tanks.

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Photodegradation of microcystin-LR (MC-LR) by fulvic acid (FA) and effect of environmental factors

WANG Yanzhao, ZHANG Jingjing, ZHANG Dajuan, DAI Wei, BI Xiangdong

Journal of Dalian Ocean University. 2024, 39(2): 281-288. https://doi.org/10.16535/j.cnki.dlhyxb.2023-220

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To investigate the photodegradation of microcystin-LR (MC-LR) by dissolved organic matter (DOM) in natural aquatic environments, the photolysis patterns and products of MC-LR in the main photosensitizer of DOM fulvic acid (FA) solutions with different concentrations of 2.5, 5.0, 7.5 and 10.0 mg/L were compared under simulated solar irradiation, and the effects of different pH values and light intensities on FA photodegradation of MC-LR were investigated. The results showed that the direct photolysis of MC-LR was found in deionized water. Different concentrations of FA led to promote the photolysis of MC-LR, with the best photodegradation at 7.5 mg/L of FA. There was degradation rate of 52.65% in 180 min. The photodegradation of MC-LR by FA was shown to be conformed to the second-order reaction kinetics, with the same photodegradation products as the direct photolysis products in deionized water. The descending order of photodegradation effects of FA on MC-LR were described as pH 6 >pH 7 >pH 8 >pH 9 and 39.8 μmol/(s·m2)> 56.9 μmol/(s·m2)> 22.8 μmol/(s·m2), indicating that both pH value and light intensity affected the photodegradation of FA on MC-LR. The best promoting effect of FA on the MC-LR photodegradation was observed at pH 6 and light intensity of 39.8 μmol/(s·m2).

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Analysis of environment of Dafeng River in Beihai, Guangxi and health status of cultivated Hong Kong oyster (Crassostrea hongkongensis)

LIU Ranyang, GAO Lei, ZHANG Xingzhi, YANG Wenwen, ZHAO Junyan, ZHAO Bao, YU Haijie, XU Jixiang, LIU Lu, PENG Jinxia, WANG Lingling, SONG Linsheng

Journal of Dalian Fisheries University. 2024, 39(4): 551-558. https://doi.org/10.16535/j.cnki.dlhyxb.2023-275

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To elucidate the impacts of water environment of Dafeng River in Beihai, Guangxi, on health status of Hong Kong oyster(Crassostrea hongkongensis) cultured therein, the physicochemical factors in water quality, planktonic microalgae, bacterial abundance, and energy reserve and oxidative stress of Hong Kong oysters were surveyed in the main Hong Kong oyster farming area of Beihai Sea of Guangzhou, the mouth of the Dafeng River and the upper waters(108°52′49″E, 21°38′26″N; 108°51′30″E, 21°46′22″N) in September and October 2023. The results showed that, the estuarine water temperature was 28.1 ℃, with a salinity of 20.89, total bacterial abundance of 7.22×108 cells/L and Vibrio abundance of 1.49×107 cells/L in September. Diatom abundance was found to be approximately 1.3×107 cells/L, with the dominant species of Skeletonema costatum. The malondialdehyde (MDA) content of 9.60 nmol/mg protein was observed in the gill of cultivated Hong Kong oysters, with glycogen content of 6.18 mg/g and glucose content of 2.59 μmol/g in the adductor muscle. In October,however, the estuarine water temperature was decreased to 25.7 ℃, accompanied by an increase in salinity to 25.50, with bacterial abundance decreased to 4.97×107 cells/L and Vibrio abundance to 1.40×104 cells/L and diatom abundance decreased to 4.3×105 cells/L in the water. MDA content was 1.02 nmol/mg protein in the gill of cultivated Hong Kong oyster, and glycogen and glucose content in the adductor muscle was decreased to 2.49 mg/g and 1.94 μmol/g, respectively. The water temperature and total bacterial abundance were similar to those in the estuarine waters in the upstream waters in October. However, salinity and Vibrio abundance were relatively low, with high diatom abundance. The glycogen and glucose contents in adductor muscle were increased in cultivated Hong Kong oysters. In summary, Hong Kong oysters cultured in the Dafeng River estuary faced multiple environmental stressors, including high temperature, elevated bacterial and Vibrio abundances in September, leading to increased oxidative stress. In October, these oysters primarily encountered a single environmental pressure, high salinity, and improved oxidative stress status. The decrease in algal food led to decline in glycogen content and resistance to environmental changes in October, and there were lower salinity, higher diatom abundance, and relatively healthier conditions for Hong Kong oyster cultivation in upstream waters in the Dafeng River.

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Innovative applications and prospects of large models in disease prevention and control for aquaculture:a review

ZHANG Sijia, YU Hong

Journal of Dalian Fisheries University. 2024, 39(3): 369-382. https://doi.org/10.16535/j.cnki.dlhyxb.2024-120

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Large models, characterized by their extensive parameters and complex structures, are foundational to machine learning and are increasingly becoming a significant direction for future technological development.This paper elucidates the core technologies employed in large models and discusses the basic conditions necessary for their operation.It also explores the utilization of large models in assisting with disease prevention and control in aquaculture, including disease prevention and management, collaborative monitoring of aquaculture environments, aquatic drug research and development, and the application of genomics techniques in breeding disease resistance in aquatic species.Future prospects encompass data acquisition, processing, model adaptability, generalization, computational needs, training costs, privacy &security, model interpretability, multi-task learning, priority management, cross-regional data sharing, and knowledge graph-enhanced large model integration.The aim is to provide robust support for further applications of large models in the field of disease prevention and control in aquaculture, thereby promoting the development of the aquaculture industry towards greater efficiency and sustainability.

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