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Optimization of thermal sterilization process for low-acid and acidified instant laver
GE Mengmeng, SHEN Jiandong, TANG Xiaohang, XIA Wenshui, XU Yanshun
 doi: 10.12131/20220003
[Abstract](149) [FullText HTML](40) [PDF 1018KB](15)
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In order to optimize the sterilization process of laver (Porphyra spp.) and develop high-quality instant wet laver products, we measured the heat penetration curves during high-pressure heat treatment (110, 115, 121 ℃) and normal pressure heat treatment (85, 90, 95 ℃) for low-acid and acidified lavers (pH≤4.6). Combined with preservation experiment and microbial analysis, we determined the F-value (safe sterilization heating time) corresponding to the two sterilization methods, and explored the effects of different temperature-time combinations on the sensory and nutritional quality of laver with the same F-value. Results show that low-acid laver could reach commercial sterility when F0 was 3 min under high-pressure heat sterilization, and acidified laver could also reach the preservation requirements when \begin{document}$ {F\,}_{93.3}^{8.89} $\end{document} was 5 min under normal pressure heat sterilization. Compared with high-pressure heat sterilization, acidification combined with normal pressure sterilization could obtain better texture and color. The toughness, hardness and sensory score of laver increased with the increase of sterilization temperature with the same F-value. In terms of nutrients, the total soluble sugar and free amino acids decreased with the increase of temperature in the high-pressure group. The highest free amino acids content was obtained at 90 °C in the normal-pressure group. In general, the texture, sensory and nutritional quality were better when the sterilization parameters were 90 °C, 11.5 min (acidified group) and 115 °C, 8 min (low-acid group).
Mathematical analysis of morphometric attributes effects on body mass for four-month-old Plectropomus leopardus
YU Wei, LIN Heizhao, MA Zhenhua, WU Qia'er, CHEN Xueqing, YANG Yukai, HUANG Xiaolin, HUANG Zhong, ZHAO Wang, LI Tao, ZHOU Chuanpeng
 doi: 10.12131/20210253
[Abstract](223) [FullText HTML](52) [PDF 605KB](16)
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In this study, we selected 159 individuals of the same batch of 4-month-old coral trout (Plectropomus leopardus) juveniles as the experimental objects to explore the correlation between the eleven morphological traits and body mass. The results show that there were significnat correlation between snout length (x9) and body mass (P<0.05), and extremely significant correlation between the other ten morphological traits and body mass. The results of path analysis reveals that the standard length (x2), body depth (x4), body width (x5), head height (x7), snout length (x9) were the main decisive morphological traits on body mass. The direct effect coefficient of body depth on body mass was 0.444, indicating that body depth mainly affected body mass through direct action. However, the other morphological traits mainly affected body mass indirectly via body depth. The total decision coefficient of five morphological traits on body mass was 0.853, indicating that these morphological traits were the main factors affecting body mass. After eliminating the morphological traits with insignificant coefficient to body mass, we established the multiple regression equation by multiple regression analysis. The morphological traits retained by the multiple regression analysis were consistent with the results of path analysis.
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2022, 18(4).  
[Abstract](8) [PDF 1010KB](5)
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Research Paper
Fish stock assessment based on abundance index and resilience: a case study of largehead hairtail in Sea of Japan and East China Sea
ZHANG Kui
2022, 18(4): 1-9.   doi: 10.12131/20210213
[Abstract](122) [FullText HTML](31) [PDF 2581KB](18)
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In order to understand the exploitation status of largehead hairtail (Trichiurus japonicus) fisheries in the Sea of Japan and the East China Sea, we used a fishery assessment model based on abundance index (Abundance maximum sustainable yields, AMSY) to assess the two fisheries. The results show that during most of the 1990s and 2000s, the relative biomass levels (B/BMSY) of the largehead hairtail fisheries in the two seas were lower than 1, but the relative fishing mortality levels (F/FMSY) were higher than 1, which indicates an overfished state. The estimated parameters such as relative maximum sustainable yield (MSYq) and relative fishing mortality at MSY level (FMSY) of the AMSY model were more sensitive to different prior distribution ranges of intrinsic rate of increase (r), while the estimated biological reference points (BRPs), i.e., F/FMSY and B/BMSY were more sensitive to the lower limit of different prior distribution ranges of relative biomass level (Bt/k). AMSY can estimate the BRPs of the target fisheries under MSY framework using only catch per unit effort (CPUE) data, prior information of r and relative biomass level for a specific year. AMSY is appropriate for fishery stock assessment in the sea areas where lack statistical data of catches.
A study on spatial-temporal distribution and marine environmental elements of Symplectoteuthis oualaniensis fishing grounds in outer sea of Arabian Sea
XIAO Ge, XU Bo, ZHANG Heng, TANG Fenghua, CHEN Feng, ZHU Wenbin
2022, 18(4): 10-19.   doi: 10.12131/20210217
[Abstract](189) [FullText HTML](29) [PDF 3261KB](8)
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In order to understand the development status of fishery resources in the waters off the Arabian Sea in the high seas of the northwest Indian Ocean, and to explore the fishery distribution of Symplectoteuthis oualaniensis and the impact of fishery environmental factors on its resources, we carried out two surveys in the waters off the Arabian Sea, obtained the data of catch and operating water temperature at each survey site, and used the Generalized Additive Model (GAM) to analyze the impact of various marine environment and tempo-spatial factors on the catch per unit effort (CPUE) of S. oualaniensis in that sea area. The results show that: 1) There are mainly three areas with high CPUE values (60°E−61°E, 16°N; 62°E, 16°E−18°N; 61.50°E−63°E, 17°N−17.75°N). 2) The influencing factors of the best GAM model included latitude and longitude, lunar calendar day, sea surface temperature (SST), chlorophyll a concentration (Chl a) and sea surface temperature anomaly (SSTA). The top three explanatory factors with the highest explained variance were longitude and latitude, lunar calendar day and SSTA. 3) The total number of catch on the no-moonlight night was 1.38 times the number of catch on the bright moonlight night, and the total catch of the no-moonlight night was 108.21% higher than the total catch of the bright moonlight night. 4) According to the GAM model, the optimal SST range was 26.5−27.5°C; the Chl a concentration range was 0.30−0.50 mg·m−3; the SSTA range was 0−0.4°C.
Pattern of fish community and its relationship with environmental factors in Fangchenggang (Qinzhou coastal area of Beibu Gulf)
ZHANG Gongjun, YANG Changping, LIU Yan, ZHOU Wenli, SHAN Binbin, WANG Liangming, WANG Sihan, SUN Dianrong, JIA Chunbin
2022, 18(4): 20-33.   doi: 10.12131/20210255
[Abstract](243) [FullText HTML](49) [PDF 2050KB](17)
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We analyzed the fish assemblage composition and spatio-temporal distribution of fish stocks based on the bottom trawl survey data in Fangchenggang (Qinzhou coastal area of Beibu Gulf) in 2016. Combining with the information of temperature, salinity, dissolved oxygen, pH and depth, we investigated the relationship between fish community structure and environmental factors. A total of 152 fish species belonging to 15 orders, 55 families and 96 genera had been collected, and Parargyrops edita, Secutor Ruconius, Saurida tumbil and Sebastiscus marmoratus were the dominant species. The abundance of fish stocks was the highest in spring. The diversity index was higher in spring and summer, but lower in winter. Four distinct groups were defined by Cluster and non-metric multidimensional scaling (NMDS) analysis, and the average similarity of the groups ranged from 18.27% (Group I) to 32.49% (Group II). The analysis of similarity (ANOSIM) shows that the differences of fish composition among different groups were extremely significant (R=0.703−0.982, P<0.01), with the most sinificant difference of 98.02% between Group I and Group IV. The results of redundancy analysis (RDA) show that the bottom temperature, dissolved oxygen, depth and bottom salinity of bottom were the main environmental factors that affected fish distribution in Fangchenggang.
Relative energy accumulation in soma and gonad tissues of female Dosidicus gigas and relation to environmental effects
LIAN Jinxin, FENG Yixuan, LIN Dongming
2022, 18(4): 34-43.   doi: 10.12131/20210219
[Abstract](192) [FullText HTML](49) [PDF 1577KB](9)
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In order to understand the life history strategy of Dosidicus gigas in terms of energy accumulation, we applied the methodology tissue energy density technique and generalized linear mixed-effects models (GLMM) to investigate the relative energy accumulation in soma and gonad tissues. The specimens of D. gigas were collected from the commercial jigging fisheries during 2017 and 2019. The results show that soma tissue was the largest organ for energy accumulation, accounting for at least 70% of the total energy of D. gigas, while gonad tissues accumulated a small portion of energy. The relative energy accumulation in soma tissue declined significantly from physiologically maturing stage to functionally mature stage, followed by a significant rebound at the spawning stage. In contrast, the relative energy accumulation in gonad tissues showed an increasing trend after the onset of physiologically maturing, reaching a peak at the stage of functionally mature. The relative energy accumulation in soma was not significantly correlated with sea surface temperature, neither was the relative energy accumulation in gonad tissues. However, there was a significant relationship between the relative energy accumulation in both soma and gonad tissues and sea surface chlorophyll-a concentration. There was also a significant relationship between the relative energy accumulation in soma and gonad tissues and sampling longitudes in the East Pacific Ocean. These observations indicate that D. gigas increases energy allocation to gonadal development after the onset of physiologically maturing, and maintains somatic condition during the spawning period. The relative energy accumulation in soma and gonad tissues may be more likely related to marine production, due to larger relative energy accumulation associated with higher chlorophyll-a concentration.
Analysis of bacterial community and diversity in gill tissues of bony fishes in adjacent South China Sea
GUO Yingxiang, YANG Liling, XU Youwei, FANG Yifei, WANG Meng, JIANG Jingzhe
2022, 18(4): 44-53.   doi: 10.12131/20210247
[Abstract](120) [FullText HTML](41) [PDF 1492KB](15)
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Focusing on the abundant fishery resources in the South China Sea, we analyzed the distribution characteristics of the microbial community in the gill tissue of bony fishes in the adjacent South China Sea by using 16S amplicon sequencing technology. In addition, we discussed the differences in the bacterial community structure at different sites. The results show that the sequencing obtained a total of 2 952 366 effective spliced fragments (Clean tags) with an average of 56 776 in each library. The dominant taxa were analyzed at phylum and genus levels. Proteobacteria was the highest (71.3%) at phylum level, and Acinetobacter was the highest at genus level (17.2%). The alpha diversity of different sites was significantly different, and the I9 and H8 sites had the highest species richness (Chao1 index), and the D3 site had the highest diversity (Shannon index). The beta diversity of samples from different sites was significantly different (P<0.05), but there was no significant difference between the host classification (Order level) groups (P>0.05). The composition of bacterial communities in the gill tissues of bony fishes in the South China Sea was abundant. Compared with the classification of the host, the sampling station has more important influence on the community of the bacterial in the gill tissues, and may play an active role in assisting the host's nutrient transport and metabolism.
Cloning and expression profiling of Cyp1a gene in Lutjanus argentimaculatus under 4-bromodiphenyl ether (BDE-3) and decabromodiphenyl ether (BDE-209) exposure
ZHANG Zhe, GONG Xiuyu, LAN Lili, WANG Xuefeng, MA Shengwei, CHEN Haigang, ZHANG Linbao
2022, 18(4): 54-64.   doi: 10.12131/20210271
[Abstract](176) [FullText HTML](26) [PDF 1388KB](6)
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Cytochrome P450 enzymes (CYPs) are encoded by P450 genes, in which cytochrome P450 1A (Cyp1a) genes mainly involve in biotransformation and metabolism of numerous xenobiotics. In this study, we cloned the Cyp1a gene from Lutjanus argentimaculatus, and investigated its tissue expression pattern. In addition, we evaluated different concentrations (10, 50 and 250 μg·L−1) of BDE-3 and BDE-209 on Cyp1a gene profile and 7-ethoxyresorufin-O-deethylase (EROD) activity in liver of L. argentimaculatus. The results show that the full length of Cyp1a cDNA was 2 540 bp with 1 566 open reading frame encoding 521 amino acids. The sequence homology of L. argentimaculatus CYP1A was the highest (92.69%) with that of Lateolabrax maculatus. Phylogenetic analysis results indicate that CYP1A was closely aligned with Sander lucioperca protein. Cyp1a transcripts were most abundant in liver, followed by brain and gill, but lowest in muscle. 10 μg·L−1 of BDE-3 and BDE-209 showed no effects on both Cyp1a expression and EROD activity, while high concentrations (50 and 250 μg·L−1) of BDE-3 down-regulated both of them significantly in a concentration-dependent manner on 7th-15th day. In contrast, exposure to 50 and 250 μg·L−1 of BDE-209 resulted in increasing of hepatic Cyp1a level and EROD activity. Moreover, Cyp1a genes levels and EROD activities showed a good correlation. High concentrations of BDE-3 and BDE-209 can affect Cyp1a gene expression in liver of L. argentimaculatus in different manners.
Identification of a novel oyster-related circovirus genome compa-rative genome analysis of oyster-related circoviruses
YANG Liling, GUO Yingxiang, WEI Hongying, WANG Meng, FANG Yifei, ZHU Peng, JIANG Jingzhe
2022, 18(4): 65-75.   doi: 10.12131/20210260
[Abstract](236) [FullText HTML](31) [PDF 1125KB](24)
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The lack of pathogen genome information is one of the main reasons for the slow progress of oyster disease research. In order to identify more oyster-associated viruses, based on the previously obtained viromic data of oysters (Crassostrea hongkongensis) cultured in multiple locations along the coast of the South China Sea, after quality control, assembly, and species annotation of the sequencing data, we selected the putative circovirus genome sequences for the construction of the phylogenetic tree, genome comparison, protein domain analysis, structure prediction and virus abundance analysis, which provides references for the research of oyster disease. The results show that five viral sequences clustered with known circoviruses in a large branch, indicating that they are members of the Circoviridae family. The five viral genome sequences all contained replication protein genes, with the highest similarity to a replication protein sequence of arthropod circovirus. The five sequences and seven other public database sequences formed an independent sub-branch. Viruses on this branch were mostly from animal-related samples. Based on the domain analysis (SMART), replicase conserved domains were identified in most sequences.
Construction and characterization research of essA, essB and essC-deleted mutants in Streptococcus agalactiae from tilapia
MA Yanping, HAO Le, FENG Guoqing, LIANG Zhiling, MA Jiangyao, KE Hao, LIU Zhenxing
2022, 18(4): 76-86.   doi: 10.12131/20210246
[Abstract](132) [FullText HTML](36) [PDF 1284KB](7)
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The membrane proteins are critical to substrate protein secretion in VII secretion system existing in Streptococcus agalactiae. In this study, we constructed the membrane proteins knockout vectors with chloramphenicol tag including pSET4s-ΔessA, pSET4s-ΔessB and pSET4s-ΔessC, and after the homologous recombination, we screened the mutant S. agalactiae ΔessA, ΔessB and ΔessC via PCR assays. Based on the growth curve analysis, S. agalactiae ΔessA, ΔessB and ΔessC strains showed significantly slower growth process than the wild type strain (WT). ΔessA and ΔessB strains had significant difference in early stage of growth compared with WT strain (P<0.01). According to the secretion product analysis of ESAT6 protein, S. agalactiae ΔessA, ΔessB and ΔessC strains showed significantly lower ESAT6 product than WT (P<0.01). According to challenge test analysis, the deletion of essA, essB or essC gene significantly reduced virulence of S. agalactiae ΔessA, ΔessB and ΔessC compared with WT (P<0.01). The results suggest that essA, essB and essC proteins are important component membrane proteins of VII secretion system in S. agalactiae, and these genes deletions cause ESAT6 mRNA expression and virulence decline.
Effects of different C/N ratios on formation of biofloc, water quality and microflora in aquaculture water of Chinemys reevesii
ZHANG Kai, LIN Yijing, LI Chenyang, LIU Fangling, SHEN Minghao, ZHENG Shanjian
2022, 18(4): 87-94.   doi: 10.12131/20200144
[Abstract](189) [FullText HTML](61) [PDF 935KB](12)
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In order to determine the feasibility and the best addition amount of biofloc technology in turtle culture, we studied the formation of biofloc and its effects on water quality and microflora by regulating the C/N ratio in the culture water of Chinemy sreevesii. We carried out an experiment with the addition of sucrose at 10∶1 (CN-10), 15∶1 (CN-15), 20∶1 (CN-20) and the control group for 40 d. The results show that the biofloc volume index of each group of biofloc became stable after 28 d, and the treatment effect of ammonia nitrogen and nitrite was significant with the C/N ratio≥10∶1. Among them, the removal rate of ammonia nitrogen and nitrite after 40 d of the group with a C/N ratio of 15∶1 were 76.7% and 64.4%, respectively, which indicates that the C/N ratio of 15∶1 can promote the formation of biofloc, and reduce the level of ammonia nitrogen and nitrite in the water effectively. The biological flocs of the experimental group (CN-15) and the control group were sequenced by high-throughput sequencing, and the results show that the dominant phyla of biofloc in the two water bodies were Proteobacteria, Bacteroidetes and Actinobacteria, but the proportion of each dominant bacteria phylum was different. In conclusion, the addition of different C/N ratios can affect the formation of biofloc, water quality and microflora of C. reevesii ponds. 15∶1 is the optimal C/N ratio for the formation of biofloc, which can promote the formation of biofloc and has a strong ability to regulate water quality.
Evaluation of genetic parameters for growth and comprehensive stress tolerance traits of Litopenaeus vannamei
WANG Lun, WANG Chongyi, LIU Jianyong
2022, 18(4): 95-102.   doi: 10.12131/20210252
[Abstract](208) [FullText HTML](29) [PDF 2490KB](15)
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To enrich the growth and stress resistance database of Litopenaeus vannamei, and to provide scientific references for the genetic improvement of its growth and comprehensive stress tolerance. We took five L. vannamei populations with different genetic backgrounds as parents, among which "Xinghai 1" (GS-01-007-2017) was the core population and the other four populations were introduced from Thailand and the United States. Eighty full-sib families had been obtained through mating and 38 families finally retained. We then used multi-trait animal model and ASReml 4 software to estimate the variance components and genetic parameters of growth and comprehensive stress tolerance of L. vannamei at 105 age old under the combined stress of high salt (35), low pH (6±0.1), and high ammonia nitrogen (70 mg·L−1). The results show that the heritability of growth traits was high (0.37±0.09)−(0.51±0.10), and the heritability of comprehensive stress tolerance traits was medium (0.21±0.06). The results show that it is feasible to improve the growth traits and comprehensive stress tolerance traits by breeding. The genetic correlation of growth traits (Including body mass, body length, head breastplate length, and full length of the abdomen) was generally high, ranging from (0.54±0.13)−(0.99±0.01) (P<0.01). The extremely significant correlation between growth traits shows that any growth trait could be replaced by other growth traits for indirect selection. The genetic correlation between growth traits and comprehensive stress tolerance traits was low to medium positive correlation (0.11±0.23)−(0.39±0.19), indicating that the comprehensive stress tolerance traits can also be indirectly improved when breeding with growth traits as the main selection target.
Embryonic development and morphological characteristics of larvae and juvenile of Platax teira
LIU Mingjian, GUO Huayang, GAO Jie, ZHU Kecheng, LIU Baosuo, GUO Liang, ZHANG Nan, YANG Jingwen, LIU Bo, ZHANG Dianchang
2022, 18(4): 103-111.   doi: 10.12131/20210251
[Abstract](427) [FullText HTML](46) [PDF 2526KB](34)
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In order to improve the egg hatching rate and fry survival rate of Tiera batfish (Platax teira), and to provide a theoretical basis for artificial spawning and fry breeding, we observed and analyzed the temporal characteristics of embryonic and juvenile development of fertilized eggs of P. teira, and measured the morphological indexes to derive the regression equations for the growth characteristics of juvenile stages. The results show that the eggs were floating, (1.29±0.09) mm in diameter, with a tough, transparent, yellow spherical shell and a single oil globule that was not sticky. At an incubation temperature of (26±0.3) ℃, salinity of 34–36 and pH 7.8±0.5, the embryos underwent seven stages of development for 27 periods, taking 27 h 45 min. The total length of newly hatched larvae were (3.120±0.349) mm, transparent, with a large amount of branched lutein scatterring on the surface of the body, followed by the juvenile stage (0–17 d) and the larval stage (17–25 d). The juvenile stage was 25 d later, when the fin spines and fin ray were fully developed, typically with three black bands on the head, trunk and tail, and a snowy silvery body color. Statistical models show that the early stages of growth were slow, but accelerated after 7 dah. At 8 dah, the juveniles showed cannibalism and aggressive behavior.
Effect of salinity on embryonic development and post-embryonic larval growth of Pramisgurnus dabryanus
CHEN Jianhua, LI Xue, ZHAO Jian, ZHU Honggeng, WANG Haihua, ZHU Ming
2022, 18(4): 112-118.   doi: 10.12131/20210230
[Abstract](182) [FullText HTML](37) [PDF 2016KB](27)
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In order to understand the adaptability of embryo and larvae of Paramisgurnus dableanus to salinity, we bred the gastrula embryos in water at salinity of 0, 2, 4, 6, 8 and 10, then investigate the effect of salinity on the hatching period, hatching rate, abnormality rate, survival rate, specific growth rate (SGR), yolk sac absorption and survival activity index (SAI). The results show that: 1) The incubation period was significantly shorter than that of the control group at salinities of 2 and 4 (P<0.05). The incubation rate was highest at salinity of 4, not significantly different from the control group (P>0.05). 2) The abnormality rate of the newly hatched larvae increased with the increase of salinity, while the survival rate of larvae of 3 dah (Days after hatching) decreased. 3) The total length of newly hatched larvae decreased first and then increased, while that of larvae of 3 dah decreased with the increasing salinity. The SGR and yolk sac absorption rate increased first and then decreased. 4) The survival activity index (SAI) of the larvae increased first and then decreased with the increase of salinity, and reached the maximum at salinity of 4. These results indicate that the optimal salinity for embryo development and larval growth of P. dableanus is 0−4.
Optimization of flow field in dual-drain square aquaculture tank with relative arc to width ratio
ZHANG Qian, GUI Jinsong, REN Xiaozhong, XUE Boru, BI Chunwei, LIU Ying
2022, 18(4): 119-125.   doi: 10.12131/20210044
[Abstract](164) [FullText HTML](40) [PDF 1069KB](13)
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In order to improve the flow field characteristics in dual-drain square aquaculture tank, we combined arc angle and straight edge to optimize the flow field, so as to provide better aquaculture equipment for the recirculating aquaculture industry. We applied computational fluid dynamics technology to simulate the flow field in dual-drain aquaculture tanks, and evaluated the effect of relative arc to width ratio (R/B, R is the radius of arc angle, B is the side length of tank wall) on the flow field characteristics in the tanks by analyzing corrected velocity v0 and uniformity coefficient UC50. The results show a same rule under different conditions of underflow split ratio (The percentage of outflow from the center outlet at the bottom of the tank in the total outflow). The average velocity in the square arc angle aquaculture tanks with 0.2≤R/B<0.4 was about twice than that in the square aquaculture tanks for the same water exchange rate, but there was no significant difference compared with the circular aquaculture tanks. According to the analysis of flow field uniformity, the square arc angle aquaculture tanks with 0.2≤R/B<0.4 had higher uniformity coefficient, and even higher than that of circular aquaculture tanks. The research indicates that the area of lower velocity caused by the right angle in the square aquaculture tanks reduced effectively by the arc angle in the square arc angle aquaculture tanks, and higher space utilization rate was retained. The advantages of the square aquaculture tank and the circular aquaculture tank are fully combined in the square arc angle aquaculture tank, which solves the problem of poor flow pattern in dual-drain square aquaculture tank, with good industrial popularization and application value.
Recognition of Acetes chinensis fishing vessel based on 3-2D integration model behavior
ZHANG Jiaze, ZHANG Shengmao, WANG Shuxian, YANG Yuhao, DAI Yang, XIONG Ying
2022, 18(4): 126-135.   doi: 10.12131/20210263
[Abstract](326) [FullText HTML](86) [PDF 2466KB](18)
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Since the yield of Acetes chinensis has decreased sharply year by year, China has begun to implement quota fishing measures for A. chinensis in offshore waters by using video surveillance technology to assist the fishing management. This paper proposes a method for identifying the behavior of A. chinensis fishing vessels based on the 3-2D fusion model, so as to provide a new solution for quota fishing management. By installing high-definition camera equipment at four fixed positions on the A. chinensis fishing vessel and recording the entire process of fishing operations, we had obtained more than 600 video surveillance data had been as initial data. Secondly, we filtered effective video data from the initial data, and divided and labeled them with five behaviors. In order to improve the efficiency of network training, we preprocessed the video data such as compression and frame number segmentation. Finally, the model was trained by building a 3-2D fusion convolutional neural network to realize the extraction and classification of fishing vessel behavior characteristics. The results show that the classification accuracy of the fishing vessel behavior recognition method was 95.35%; the recall rate was 94.50%; the average accuracy was 96.60%; the overall score of the model could reach 93.32%; and the average detection time was 35.46 ms·frame−1. The method can be used for real-time analysis of the fishing video of A. chinensis fishing boats.
Analysis of solid-state anaerobic fermentation process of mackerel processing by-products by high-throughput sequencing
WANG Yao, LI Hongyu, QI Xiangming, MAO Xiangzhao, DONG Hao, GUO Xiaohua
2022, 18(4): 136-146.   doi: 10.12131/20210285
[Abstract](136) [FullText HTML](26) [PDF 1053KB](30)
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In order to develop commercial technology for the comprehensive utilization of mackerel (Pneumatophorus japonicus) processing by-product, we carried out the non sterilized solid-state anaerobic fermentation of mackerel by-products to produce a novel protein source for feed with bioactivity. In addition, we monitored the content of histamine, acid-soluble protein and other indexes such as pH, total volatile basic nitrogen and antigenic protein; and investigated the evolution of microbial community during the fermentation by high-throughput sequencing technology, comparing the free amino acids and fatty acids before and after the fermentation. The results show that Lactobacillus plantarum HSCC-LP121 had the best comprehensive effect in increasing acid soluble protein content, reducing histamine accumulation and reducing volatile base nitrogen production. After 30 d of fermentation, the histamine content decreased to 0.629 g·kg−1, which indicates that HSCC-LP121 had the ability to degrade histamine. Moreover, HSCC-LP121 inhibited the growth of potential histamine-producing microorganisms such as Psychrobacter and Pseudomonas. Besides, the strain could also inhibit the growth of potentially harmful fungi such as Aspergillus, and induce the growth of some aroma-producing yeasts.
Effect of carbon dioxide anesthesia on physiology and quality of tilapia
YUAN Yuanyue, CEN Jianwei, LI Laihao, YANG Xianqing, HUANG Hui, WEI Ya, HAO Shuxian, ZHAO Yongqiang, WANG Yueqi, LIN Zhi
2022, 18(4): 147-155.   doi: 10.12131/20210276
[Abstract](180) [FullText HTML](43) [PDF 896KB](38)
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We used carbon dioxide (CO2) to anesthetize tilapia (Oreochromis niloticus) to reduce the stress response caused by operation, and analyzed the changes of physiology and meat quality of tilapia during anesthesia and resuscitation. By studying the anesthetic effects of different treatment temperatures, we found that the optimal temperature for CO2 anesthesia of tilapia was 15 ℃; the duration of anesthesia was (101±18) s; the duration of resuscitation was (134±23) s. The serum indexes of hydrocortisone (COR), blood glucose (GLU), aspartate aminotransferase (AST),  alanine aminotransferase (ALT) and alkaline phosphatase (ALP) increased significantly after anesthesia, but decreased after resuscitation. The glycogen (GLY) content decreased significantly after anesthesia, while the lactic acid (LD) content in liver reached the maximum value after resuscitation. The LD content in muscle increased during anesthesia but decreased when the stress was relieved. High malondialdehyde (MDA) content but low superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and total antioxidant capacity (T-AOC)  activity were observed during anesthesia. The hardness, adhesiveness and chewiness of the fillets were significantly affected by anesthesia, but could recover to the control group's level after 24 h, with stable flexibility. In conclusion, tilapia can be anesthetized effectively and quickly after CO2 anesthesia treatment; anesthesia treatment causes oxidative stress response of tilapia; and the physiological state of tilapia can be restored after stress was relieved.
Study on extraction, identification and stability of UV resistant MAAs from Porphyra haitanensis in cosmetics system
XU Feng, CHEN Deke, CHEN Xiaogang, NIE Jinmei, MA Zhihao, SUN Huili, CHEN Xin
2022, 18(4): 156-162.   doi: 10.12131/20210244
[Abstract](236) [FullText HTML](60) [PDF 767KB](29)
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Taking Porphyra haitanensis as raw material, we extracted the mycosporine-like amino acids (MAAs) and charaterized them by UV Vis spectroscopy and Liquid Chromatograph-Mass Spectrometer (LC-MS), so as to study the effects of various factors in the cosmetic system (pH, light, temperature, preservatives, antioxidants and functional additives) on the stability of MAAs. The results show that Shionrine and Porphyra-334 were the main MAAs in P. haitanensis. MAAs had the highest stability in the weak acid environment with pH=6. UV irradiation for 10 h could decrease the absorbance value by 94.4%. After having been placed at 48 ℃ for 56 d, its absorbance value decreased by 28.3%. At 48 ℃, the addition of small peptide and hyaluronic acid increased the absorbance value of the solution by 82% and 18.6%, respectively, which could improve the stability of MAAs compounds significantly. Other commonly used preservatives, antioxidants and functional additives had no significant effects on the stability of the MAAs.
Research Notes
Comparative analysis of nutritional composition and energy density of muscle in three geographical populations of Megalobrama terminalis
LIU Yaqiu, LIU Mingdian, LI Xinhui, LI Jie
2022, 18(4): 163-169.   doi: 10.12131/20210226
[Abstract](149) [FullText HTML](27) [PDF 619KB](34)
Abstract:
In order to compare the nutritional composition and energy density of Megalobrama terminalis populations in Wangquan River, Moyang River and Xijiang River, we applied the biochemical analysis methods to determine the contents of moisture, crude protein, ash and crude fatty, as well as amino acid and fatty acid composition and energy density of the muscle of three M. terminalis populations. The results indicate that the Xijiang River population had the highest crude protein mass fraction [(20.2±0.5)%], while Wangquan River population had the highest water mass fraction [(79.0±0.5)%]. The energy density of Xijiang River population was significantly higher than that of Wangquan and Moyang River populations (P<0.05). The essential amino acid index (EAAI) of Xijiang River population was higher than that of Wanquan and Moyang River populations. We had detected 23 kinds of common fatty acids in the muscle of three M. terminalis populations. The content of monounsaturated fatty acid (MUFA) in the muscle of Wanquan River population was the lowest, while the content of polyunsaturated fatty acids (PUFA) of Wanquan River populatin was the highest. The DHA content in muscle of Xijiang River population was much higher than that of Wanquan and Moyang populations. Potassium (K) and copper (Cu) had the highest and lowest contents among all the mineral elements in the muscle of three M. terminalis populations, respectively. The contents of ferrum (Fe) and manganese (Mn) of Xijiang River population were significantly higher than those of Moyang and Wanquan River populations, but the content of zinc (Zn) of Xijiang River population was much lower than that of Moyang River population.
Rapid determination of prometryn in aquatic products by QuEChERS combined with gas chromatography mass spectrometry
MA Lisha, YIN Yi, TIAN Fei, XIE Wenping, SHAN Qi, ZHENG Guangming, LI Lichun, LIU Shugui, DAI Xiaoxin, ZHAO Cheng, WEI Linting, LIN Jiawei
2022, 18(4): 170-176.   doi: 10.12131/20210351
[Abstract](144) [FullText HTML](30) [PDF 1620KB](33)
Abstract:
A method was developed for the determination of prometryn in aquatic products by quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction coupled with gas chromatography mass spectrometry. The samples were extracted by acetonitrile-dichloromethane mixture (V:V=8:2) and purified by neutral alumina, zirconium dioxide, PSA and GCB, quantified with internal standard. Good linearity was obtained in the range of 5.00−200 µg·L−1 with the correlation coeficient of 0.9999. The average recoveries were 85.8%−111.8% in Ctenopharyngodon idellus, Siniperca chuatsi, Penaeus chinensis, Holothuria sp. and Meretrix meretrix at four spiked levels of 10, 20, 40 and 200 µg·kg−1 with RSDS of 1.2%−8.8%, which meets the quality control specifications required in the national standard (GB/T 27404−2008 Criterion on Quality Control of Laboratories-Chemical Testing of Food). The limits of detection (S/N≥3) and quantification (S/N≥10) were 5.0 and 10.0 µg·kg−1, respectively. The method is suitable for the rapid determination of the prometryn residues in aquatic products owing to its advantages of simplicity, sensitivity, accuracy and better purification.
Display Method:
Comparison and optimization of total phosphorus determination method in mariculture tailwater
LIU Yan, TONG Fei, CHEN Pimao, YUAN Huarong, FENG Xue
 doi: 10.12131/20220056
[Abstract](0)
Abstract:
In order to improve the efficiency of the determination of total phosphorus (TP) in the mariculture tailwater. we determined the TP content by microplate reader instead of spectrophotometer in mariculture tailwater, and optimized the digestion method of TP, the type of microwell plate and the amount of sample. The results show that there was no significant difference between 60 min of digestion using a temperature-controlled heating plate and 30 min of digestion using an autoclave (P>0.05). The sensitivity of the assay was better than those of the other experimental groups (200 µL for 96-well plate, 200 µL for 96-well quartz plate, 200 µL and 500 µL for 48-well plate, 500 µL and 1 mL for 24-well plate) when using a 48-well plate with 1 mL of sample. The linear correlation between phosphate concentration and absorbance was the best (R2=0.999 9) for the 48-well plate with 1 mL and the 96-well plate spiked with 200 µL. The accuracy and precision validation of TP determination in mariculture tailwater showed that the relative error (RE) and relative standard deviation (RSD) of the 48-well plate spiked with 1 mL were higher than those of the other experimental groups (96-well plate 200 µL, 96-well quartz plate 200 µL, 48-well plate 200 µL and 500 µL, 24-well plate 500 µL and 1 mL). The recoveries of disodium glycerophosphate (β-GLP) and sodium hexametaphosphate (SHMP) were 98.2%−99.6% and 93.4%−97.1%, respectively, and the limit of quantification (LOQ) of TP were 0.25 µmol·L−1; the RE and RSD of 96-well ELISA plate spiked with 200 µL were −14.03%−0.21% and 2.63%−14.23%, respectively, and the recoveries for β-GLP and SHM were 94.7%−99.0% and 88.9%−97.3%, respectively, and the LOQ of TP was 0.55 µmol·L−1. At TP concentration of 0.55−6.4 µmol·L−1, the accuracy and precision of the two optimized methods meet the determination requirements and can be used for the determination of TP in mariculture tailwater.
Protective effect of Xiaochaihu Decoction on D-GalN/ LPS-induced hepatocyte injury in hybrid grouper (Epinephelus lanceolatusy♂× E. fuscoguttatus♀)
ZOU Cuiyun, CHEN Xiaojing, WU Yingxin, HUANG Jinxiong, TAN Xiaohong, HU Xinyue, GAN Songyong, WU Jinhui
 doi: 10.12131/20210362
[Abstract](85)
Abstract:
The study aims to evaluate the protective effect of Xiaochaihu Decoction (XCHD) on chemical hepatocyte injury. Hepatocytes were treated with D-GalN (20 mmol·L–1) and LPS (1 μg·mL–1) for 24 h to build a hybrid grouper (Epinephelus lanceolatus♂×E. fuscoguttatus♀) hepatocyte injury model, then we pretreated the liver cells with different concentrations of XCHD (100, 200 and 400 μg·mL–1) (D-GalN/LPS damage), and measured the hepatocyte viability by the CCK-8 assay. Hepatocyte morphology was visualized by HE staining, and cell supernatants were collected to detect the content of the inflammatory factors INF-, COX-2, and PGE2, as well as the expression of apoptotic and immune-related genes in the cell cryoprecipitate. The results show that XCHD can improve the survival rate of hepatocytes, inhibit INF-γ activity and coX-2 and PGE2 contents in the supernatant of hepatocytes induced by D-GalN/LPS injury to a different extent, reduce LDH, AST and ALT contents and apoptosis rate of hepatocytes. Besides, it had a significant protective effect on the structure of hepatocytes, significantly inhibiting the up-regulation of apoptosis-related genes caspase-3, caspase-9 and P53, and enhanced the up-regulation of immune-related genes TLR3. According to the data from the statistical analysis, the inhibition effect was most obvious in the 200 μg·mL–1 XCHD group. In conclusion, XCHD has a protective effect on the chemical liver injury of Epinephelus lanceolatus♂×E. fuscoguttatus♀, and can prevent the occurrence and development of liver disease, which provides a new insight for the study of liver protection drugs in fish.
Hydrodynamic performance of Argentine shortfin squid (Illex argentinus) bottom trawl based on model experiment
HAO Yuxin, WAN Rong, ZHOU Cheng, YE Xuchang, GUAN Qinglong, ZHANG Xiaoxian
 doi: 10.12131/20210343
[Abstract](154)
Abstract:
Illex argentinus, inhabiting in shallow waters with a short life cycle, is an important economic cephalopod in the high seas fishing ground of the southwest Atlantic Ocean. Squid jigging and bottom trawling are the main fishing patterns to catch this species. However, there are some problems in the bottom trawling, such as high energy consumption, and poor matching between vessel and trawl. Thus, it is necessary to understand the hydrodynamic performance of bottom trawl for I. argentinus. In this paper, we conducted a model experiment in the dynamic water tank to explore the effects of towing speed, horizontal spreading ratio, buoyancy-mass ratio on hydrodynamic performance of height of net opening, resistance, coefficient of energy consumption and power consumption. The model net was designed based on the small mesh six-panel single boat bottom trawl used for the main capture of I. argentinus [Main scale: 200 m×113.8 m (84.6 m)]. According to the Tauti's Law, the model experiment was scaled with the large scale ratio of 1∶30 and the small scale ratio of 1∶5. When the towing speed V was 3 kn and the horizontal spreading ratio L/S was 0.54, the buoyancy-mass ratio increased from 0.6 to 0.7, the height of the net opening increased from 9.66 m to 14.1 m, and the resistance increased from 73.73 kN to 83.48 kN. However, with the increase of towing speed, the influence of the buoyancy-mass ratio on the height of the net opening and resistance decreased. When the sweeping area of trawl opening was less than 200 m2, the energy consumption coefficient was greatly affected by the horizontal expansion ratio, on the contrary, it was greatly affected by the height of trawl opening. The power consumption increased with towing speed and horizontal spreading ratio. It accounted for more than 10% of main engine power for vessel when towing speed was more than 4 kn.
Effects of cold stress on black porgy tissue injury and apoptosis gene expression
WEI Mingliang, ZHANG Zhiwei, ZHANG Zhiyong, LIN Zhijie, ZHU Fei, JIA Chaofeng, MENG Qian, XU Dafeng, ZHANG Caojin
 doi: 10.12131/20210372
[Abstract](209)
Abstract:
In order to explore the physiological adaptation mechanism of black porgy (Acanthopagrus schlegelii) under low temperature stress, we designed three temperature gradient groups (15, 10 and 5 ℃). Taking 15 ℃ as the control group and with a low temperature stress for 24 h, we studied the tissue structure changes, physiological, biochemical reactions and the expression of apoptosis genes before and after the cold stress. The results show that with the intensification of low temperature stress, tissue damage such as liver vacuolation, gill lamellae contraction and breakage and muscle fiber breakage were aggravated. The content of triglyceride (TG) in the liver decreased significantly, while the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) as well as the content of total cholesterol (T-CHO) increased significantly, indicating that the black porgy had suffered from liver dysfunction and structural damage under cold stress condition. At 10 ℃, the liver reduced the damage of cold stress by decreasing expression levels of apaf-1, bax and caspase-1 genes, increasing expression of caspase-3 and diablo genes so as to reduce the loss of liver cells. When the temperature reached 5 ℃, the temperature exceeded the black porgy's physiological regulation threshold, so the degree of liver cell damage was aggravated. The expression of apaf-1, bcl-2 and diablo genes were promoted, while the caspase-3 gene expression was inhibited in order to maintain the homeostasis of liver cells to the greatest extent. It is showed that as the temperature decreased, the liver, gills and muscle damages of black porgy increased. The liver regulated the expression of AST, ALT, T-CHO, TG and apoptotic pathway related genes to reduce the damage caused by tissue damage.
Advances on antibiotic resistance genes (ARGs) in aquaculture environment
LI Danyi, WANG Xunuo, ZHANG Guangju, WANG Zenghuan, HUANG Ke
 doi: 10.12131/20210207
[Abstract](253)
Abstract:
Antibiotics play a significant role in the disease control of aquatic organisms and output increase of aquatic products. However, the long-term abuse of antibiotics can result in the occurrence of antibiotic resistant bacteria (ARB) which harbor antibiotics resistance genes (ARGs) in aquatic organisms. The persistent existence, migration and spread of ARGs in aquaculture environment will potentially cause genetic pollution, destroy the ecological balance, and pose risks to human health. Therefore, how to constrain the spread of antibiotic resistance has attracted global attention. In terms of the research advancement of ARGs in aquaculture environment, this review systematically summarizes the status of ARGs pollution coupled with the source, migration and spread behavior of ARGs and their influencing factors, illustrates the correlations between ARGs and antibiotics, microbial communities and environmental factors, as well as discusses the effect of antibiotics, ARGs and ARB on ecological environment and human health. Thus, the paper reviews the management strategies and removal technologies of ARGs, and proposes the future research directions regarding ARGs, so as to provide references in revealing the pollution mechanism of ARGs and reducing the transmission risk of antibiotic resistance.
Effects of salinity stress on oxygen consumption rate, ammonia excretion rate and immune-related enzyme activities of Strombus luhuanus
CHEN Xu, ZHAO Wang, CHEN Mingqiang, TAN Chunming, YU Gang
 doi: 10.12131/20210346
[Abstract](150)
Abstract:
To investigate the adaptability of salinity stress of Strombus luhuanus, we studied the effects of different salinities [17, 22, 27, 32 (control group) and 37] on the oxygen consumption rate, ammonia excretion rate and immune-related enzyme activities of S. luhuanus by hydrostatic method. The results indicate that the oxygen consumption rate and ammonia excretion rate in the control group were significantly higher than those in the other groups (P<0.05). The activity of total superoxide dismutase showed no difference (P>0.05). Compared with the control group, the catalase activity in hepatopancreas groups increased to varying degrees, while the catalase activity in muscle groups was not significantly different (P>0.05). The peroxidase activities of hepatopancreas in the control group, salinity 27 and 37 groups were significantly higher than those in salinity 17 and 22 groups (P<0.05). The peroxidase activities of muscle in the experimental groups were significantly higher than that in the control group (P<0.05). The lysozyme activities of hepatopancreas and muscle in the control group were significantly higher than those in the other experimental groups (P<0.05). In summary, the oxygen consumption rate, ammonia excretion rate and activities of immune-related enzyme have significant effects on S. luhuanus under salinity stress.
Evaluation of scale effect on hydrodynamic force of V-shaped otter board based on CFD
LIU Jingbin, TANG Hao, XU Liuxiong, SUN Qiuyang, LIU Wei, YIN Liqiang, ZHANG Feng
 doi: 10.12131/20210355
[Abstract](151)
Abstract:
The main way to study the hydrodynamic characteristics of the otter board is to build a physical model to measure its hydrodynamic characteristics based on the similarity law. In this study, we analyzed the lift, drag coefficient and flow field distribution of V-type otter board with three scale ratios (1∶2, 1∶3 and 1∶4) and three thickness (2, 5 and 10 mm), and compared them with the corresponding model test results to explore the influence of different physical model scales on hydrodynamic estimation of the otter boards. The results show that: 1) With the increase of the angle of attack, the drag coefficient of otter board with all scales gradually increased, while the lift coefficient first increased and then decreased, and the lift-drag ratio gradually decreased. 2) When the angle of attack reached 30°, the apparent separation vortex appeared at the back of the otter board, resulting in the decrease of simulated lift force. 3) With the increase of the otter board model scale, the separation effect of the boundary layer on the otter board surface and the separation vortex of the flow field in the wake area increased gradually, and the lift, drag and lift-drag ratio of the otter board also showed an increasing tendency. The thickness of the mesh plate had little effect on the flow field, lift and resistance, and the average error of the maximum lift coefficient relative to the model test was 4.97%. As the model scale increased, the prediction error of hydrodynamic force decreased gradually.
Mining of InDel marker and association analysis of hypoxia tolerance traits in Trachinotus ovatus based on resequencing
SAN Lize, LIU Baosuo, ZHANG Nan, GUO Liang, GUO Huayang, ZHU Kecheng, ZHANG Dianchang
 doi: 10.12131/20210347
[Abstract](171)
Abstract:
In this study, the whole genome re-sequencing technology was applied to analyze the InDel differences of Trachinotus ovatus gene excavated the InDel sites that were significantly associated with hypoxia tolerance traits in T. ovatus, and explored the candidate genes related to hypoxia tolerance traits. Altogether 693.48 Gb was obtained by sequencing, and the average value of Q30 was 90.8%. A total of 2 574 178 InDel markers were found by annotation analysis. A total of 249 395 InDel markers were found in the 50 T. ovatus in the tolerance group, of which 2 209 were located in exons. It is found that there were mutated genes in the nucleotide excise repair signaling pathway and cell adhesion molecules. Three InDel markers (InDel 22883061, InDel 24919481 and InDel 14451779) were found to be close to the significance threshold by association analysis between InDel markers and hypoxia tolerance trait. Nine candidate genes were obtained by annotation analysis. The selected InDel markers were of great value for selecting and identifying molecular marker selection breeding. The annotated candidate genes provide abasis and references for the study of the hypoxia tolerance mechanism of T. ovatus.
Ecological health assessment of Cyprinus carpio and Leiocassis longirostris national aquatic germplasm resources reserve in Huaihe River
WANG Dongwei, CHEN Yongjin, FANG Di'an, ZHOU Yanfeng
 doi: 10.12131/20220109
[Abstract](11)
Abstract:
In order to explore the water ecological health status of Cyprinus carpio and Leiocassis longirostris national aquatic germplasm resources reserve in Huaihe River, according to the survey results of phytoplankton community structure in 2020 and combined with the morphological functional group classification, we constructed the ecological health evaluation system of the reserve based on the biological integrity index of phytoplankton. Besides, we carried out the Mann-Whitney non-parametric test and correlation analysis of the candidate parameters to determine the final evaluation parameters, and used the ratio method to determine the grading evaluation standard for the evaluation of the health status of the reserve water. The results show that the evolution trend of dominant functional groups of phytoplankton was III+IV+V(Spring)→III+IV+V+VI (Summer)→V+VI (Autumn)→IV+V+VI (Winter). Except that the dominant functional groups in the core area were III+ IV+V+VI, the dominant functional groups of the experimental area, the Guo river and the Huaihe River were III+IV+V+VI. 68.06% of the sampling sites in the reserve were evaluated as "average" or above, indicating that the overall water ecological health status was good. Specifically, the temporal pattern of winter was better than autumn, followed by summer, and the worst was in spring; the spatial pattern of Huaihe River mainstream was better than Guohe River, and the experimental area was better than the core area.
Evaluation of fisheries ecological environment in adjacent sea areas of Wanshan Archipelago in Pearl River Estuary in spring
WU Peng, LIU Yong, XIAO Yayuan, XIE Yufang, TANG Guanglong, LIN Lin, WANG Teng, LI Chunhou
 doi: 10.12131/20210332
[Abstract](204)
Abstract:
Wanshan Archipelago plays an important role in the conservation of fishery resources in the Pearl River Estuary. However, there is still a lack of sufficient research on the fishery ecological status of the adjacent waters of islands and reefs in this region. Thus, we analyzed the characteristics of the seawater environment and zooplankton community in Wanshan Archipelago in April 2021. The results show that the seawater environment of Wanshan Archipelago was greatly influenced by fresh water input from the Pearl River coastal channels. Consequently, the concentration of dissolved inorganic nitrogen, nutrient quality index and eutrophication index were higher in the adjacent sea areas of Guishan Island and Dong'ao Island which are located in the northwestern Wanshan Archipelago. Eutrophication was observed in this area. Furthermore, the primary production in the seawater of these two islands was also higher, most with medium and low levels. The zooplankton communities of Wanshan Archipelago can be divided into three groups, and one of them affiliated to the adjacent sea areas of Guishan Island had a low Shannon index value, indicating a potentially polluted seawater environment. However, high abundances of spawning and larval fish were observed at Guishan Island (133 and 18 egg·m−3, respectively), suggesting that it is an important fish spawning area. The primary production and Pielou evenness index of zooplankton can reflect the correlation between water environment and zooplankton community in Wanshan Archipelago, and can indicate the state of water eutrophication.
Molecular characterization and expression of MAP2K1 gene in Hyriopsis cumingii
LIU Meiling, SHANGGUAN Xiaozhao, WANG Xiaoqiang, WANG Yayu, WANG Guiling, LI Jiale
 doi: 10.12131/20210328
[Abstract](119)
Abstract:
In order to study the role of the MAP2K1 (MEK1) gene in the sex determination of Hyriopsis cumingii, we applied RACE method to clone the MAP2K1 gene sequence. We used real-time fluorescence quantitative analysis to compare MAP2K1 gene in six tissues (Gonads, adductor muscle, hepatopancreas, gills, mantle, foot), gonads at early developmental stage (1−8 month old) and 1−3 years' level of expression in male and female glands of H. cumingii. We determined the location of MAP2K1 gene in the gonads of 2-year-old H.cumingii by in situ hybridization. The results show that the ORF region of MAP2K1 gene was 1 194 bp in length and encoded 397 amino acids. MAP2K1 gene was highly expressed in the ovary; the expression level was the highest at 2 months of age at early developmental stage; the expression results from 1−3 years of age show that the expression of MAP2K1 gene in the ovary was higher than that in the spermatozoa for the same period (P<0.05). The in situ hybridization results show that the MAP2K1 gene had a significant hybridization signal in the oocytes and eggs of female H. cumingii. RNAi results show that the expression of the downstream gene MAP2K1 gene decreased by 82.31% in females and 73.60% in males after interfering with the upstream gene C-MOS gene of MAP2K1 gene. In conclusion, MAP2K1 gene may be involved in the ovarian development process and is a female-biased gene in H. cumingii, and C-MOS gene affects its expression.
Responses of important virulence factors of Aeromonas veronii to environmental conditions
WANG Qian, DENG Yiqin, LIN Ziyang, SU Wenxiao, LIU Mengyao, CHENG Changhong, GUO Zhixun, FENG Juan
 doi: 10.12131/20210273
[Abstract](160)
Abstract:
As important pathogenic factors of Aeromonas veronii, flagellin, quorum sensing and Type III secretion system (T3SS) are closely related to their pathogenicity and regulated by varieties of environmental conditions. In order to study the effect of variation in external environmental factors on the pathogenic factors of A. veronii, we used the ascF, fliE and luxR factors of A. veronii as objects by real-time PCR method. The response of ascF, fliE and luxR genes to environmental factors such as temperature, pH, rotating speed and ions were explored at the transcription level. The results show that the three genes of A. veronii had a positive response to acidic environment (pH 6.5−7.0), low and medium speed (150−210 r·min−1), Zn2+ and Mg2+. The response patterns of the three genes of the two strains of A. veronii with different molecular typing were different, indicating that the pathogenic mechanisms of A. veronii might be different. Besides, the important virulence factors of A. veronii were regulated by environmental conditions and showed different regular change. The results can provide references for further research on the pathogenesis of A. veronii.
Effects of elevated CO2 and photoperiod on growth and physiological performance inseedlings of Ulva prolifera
ZHOU Wei, WU Hui, HUANG Jingjing, ZHAO Xixing, WANG Jingwen, WANG Jinguo
 doi: 10.12131/20210278
[Abstract](156)
Abstract:
Ulva prolifera seedlings, which are the main component of the natural "seed bank" of green tide algae, play an important role in the occurrence and development of green tide. In this study, both the growth and physiological responses of seedlings were studied after the seedlings being cultured at two different CO2 levels (LC, 400 μatm; HC, 1 000 μatm) in combination with three different photoperiods (LL: 10 L∶14 D; ML: 12 L∶12 D; HL: 14 L∶10 D). The relative growth rate of seedlings were significantly enhanced by elevated CO2 under three light-dark regimes. The seedlings showed an obvious higher growth rate and a lower dark respiration rate (Rd) at HL treatment than at ML treatment, regardless of the CO2 treatment. The photochemical performance was largely unaffected by elevated CO2 and day length. Elevated CO2 and longer day light had negative effects on chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoids (Car) content. The results suggest that the growth and physiological of seedlings are significantly influenced by elevated CO2 and photoperiod. HCHL promotes the growth of its seedlings and increases the possibility of outbreak of green tide caused by U. prolifera. This study provides basic data for in-depth understanding of the causes of green tide algae outbreak.
Research on effect of hypoxia stress on liver tissue of zebrafish (Danio rerio) based on transcriptomics technology
SONG Ruhao, HU Ruiqin, LI Genfang, ZHANG Zhicong, XU Qianghua
 doi: 10.12131/20220038
[Abstract](16)
Abstract:
To explore the regulatory mechanism of fish response to hypoxia stress, we stressed 1-month-old wild zebrafish (Danio rerio) by hypoxia to 1.5 mg·L−1 for 2 months, and then investigated the liver tissues by transcriptome sequencing and comparative analysis. According to the KEGG analysis performed on 3 270 differential genes in normoxia and hypoxia groups, the genes mainly enriched in pathways such as cell proliferation, lipid metabolism, carbohydrate metabolism and amino acid metabolism. Among them, the up-regulated 1 864 genes were mainly related to cell proliferation, and the down-regulated 1 406 genes were mainly involved in lipid metabolism. We performed a GO enrichment analysis on the differential genes, and found that the function of iron ion banding was significantly different. Based on the analysis of expression of iron metabolism-related genes, the iron ion storage related genes fthl28 and fthl31 changed significantly, which suggests that the iron ion content in zebrafish liver (ZFL) tissue changes significantly under hypoxic stress. Moreover, we conducted the in vitro validation experiments by using ZFL cells which were subjected to 0.1% (Volume fraction) O2 hypoxia stress. The results show that with the prolongation of hypoxia stress time, the survival rate of ZFL cells decreased, and the expression of iron metabolism-related genes and ferritin in the cells decreased significantly. In conclusion, iron metabolism regulation is an important response process under hypoxia stress. Hypoxia may lead to disturbance of intracellular iron metabolism, and prolong hypoxia time which will form a new iron homeostasis. The study provides a theoretical basis and references for exploring the hypoxia adaptation mechanism of fish.
Study on relationship between body mass and blood indexes of juvenile Thunnus albacares
LIU Hongyan, FU Zhengyi, YU Gang, MA Zhenhua
 doi: 10.12131/20220077
[Abstract](20)
Abstract:
In order to study the basic blood indexes of cultured yellowfin tuna (Thunnus albacares), we determined the concentrations or activities of albumin, triglyceride, total cholesterol, transaminase, lysozyme and phosphatase in its serum (W1: 400−900 g; W2: 900−1 400 g; W3: 1 400−1 900 g) with different body mass. The results show that there were significant differences among the albumin, triglyceride and aspertate aminotransferase groups (P<0.05). The glutamic pyruvic transaminase activity and total cholesterol concentration in W2 group were significantly lower than those in the other two groups (P<0.05). The ascending order of the concentrations of albumin, triglyceride and total cholesterol was W2<W1<W3. There was no significant difference in the alkaline phosphatase activity between groups (P>0.05). The acid phosphatase activity in W1 group was significantly higher than that in the other two groups (P<0.05), and the lysozyme concentration in W1 group was not significantly different from that in the other two groups (P>0.05). The results reveal that there were differences in the blood indexes among the three groups of different mass; the difference between W2 group and the other two groups was greater, and the difference between W1 group and W3 group was smaller.
Study on tyrosinase inhibitory activity and Cu2+ binding activity of tilapia skin peptides
SONG Yuqiong, HU Xiao, XIANG Huan, CHEN Shengjun, LI Laihao, YANG Xianqing, WU Yanyan, MA Haixia
 doi: 10.12131/20220097
[Abstract](16)
Abstract:
In order to study the mechanism of tilapia (Oreochromis spp.) skin collagen peptides inhibiting melanogenesis activity, we used three kinds of proteases to hydrolyze the tilapia skin, and filtered the tilapia skin tyrosinase (TYR) inhibitory peptides (TSTIP) with the highest inhibitory activity. Then we studied the relevance between TYR inhibitory activity and Cu2+ binding activity. The results show that the product of tilapia skin hydrolyzed by alcalase for 4 h exhibited both the highest TYR inhibitory activity and Cu2+ binding activity, which were significantly positively correlated (R=0.856). When TSTIP was bound to Cu2+ or tyrosinase, the intrinsic fluorescence absorption had a consistent decreasing trend, but the UV absorption increased and the maximum absorption wavelength had a red shift. For FTIR results, TYR and Cu2+ bound to TSTIP mainly by carbonyl and amino groups. Circular dichroism shows that the β-turn and random curl contents of the two conjugates decreased relatively, while the β-fold content increased relatively, which was more obvious for TSTIP-Cu2+. In conclusion, the structural change of TSTIP-TYR is similar with that of TSTIP-Cu2+, which indicates that TSTIP can inhibit TYR's activity by binding to its Cu2+ active site.
Effect of five factors on removing ammonia nitrogen and nitrite by Rhodococcus ruber HDRR2Y fermentation
XU Yu, HU Xiaojuan, ZHANG Song, XU Wujie, SU Haochang, WEN Guoliang, CAO Yucheng
 doi: 10.12131/20220044
[Abstract](19)
Abstract:
The bacteria Rhodococcus ruber is usually used in waste water and sewage treatment, to discuss the effect of environmental factors on R. ruber HDRR2Y removing ammonia nitrogen and nitrite, we added the culture medium of R. ruber strain HDRR2Y to the breeding water containing high concentration of ammonia nitrogen (NH4+-N) and nitrite (NO2-N), and observe the changes of ammonia nitrogen and nitrite concentrations by the national standard method, so as to investigate the effect of the culture medium on the removal of ammonia nitrogen and nitrite. In addition, we carried out the Plackett-Burman experimental design according to five factors: temperature, rotating speed, salinity, inoculum amount, substrate (Ammonia nitrogen and nitrite) concentration, to explore the effect of these factors on the removal of ammonia nitrogen and nitrite by Rhodococcus ruber. The results show that during the fermentation process, the mass concentration of strain HDRR2Y increased from 5×104 CFU · mL−1 to 4.08×109 CFU·mL−1 in the initial 36 h. After adding the culture medium, the mass concentration of ammonia nitrogen decreased from 15 mg·L−1 to 5.56 mg·L−1, with a removal rate of 62.96%, and that of nitrite decreased from 15 mg·L−1 to 6.95 mg·L−1, with a removal rate of 59.37%. Among the five factors, temperature and ammonia nitrogen concentration had the most significant effects on the removal of ammonia nitrogen by strain HDRR2Y (P<0.05) (Temperature>ammonia nitrogen concentration>rotation speed>biomass>salinity). Temperature and rotating speed were the two most significant factors affecting the removal of nitrite (P<0.05) (Temperature>rotating speed>salinity>nitrite concentration>bacterial count). It is showed that the culture medium of strain HDRR2Y is good for removing ammonia nitrogen and nitrite, and temperature is the most significant factor affecting the efficiency of HDRR2Y in removing ammonia nitrogen and nitrite.
Comparative analysis of nutritional composition of muscle from Siganus oramin living in different habitats
YANG Yukai, HUANG Xiaolin, SHU Hu, LIN Heizhao, WANG Lan, XUN Pengwei, YU Wei, HUANG Zhong, LI Tao
 doi: 10.12131/20210345
[Abstract](30)
Abstract:
To provide basic data for the development of Siganus oramin formula feed, we determined the general nutritional composition, amino acids and fatty acids in the muscle of S. oramin from industrial farming, high pond farming and the wild by means of biochemical analysis, investigated the effects of habitat on muscle nutrition and quality of S. oramin. The results show that compared with the wild fish, the contents of crude protein and crude lipid were higher but those of ash and moisture were lower in the muscle of the farmed fish, and the crude fat content in the industrial farmed fish was significantly higher than the other groups (P<0.05). Moreover, there were 17 common amino acids found in the three kinds of fishes. Among them the glutamate content was the highest. Among the essential amino acids (EAA), lysine had the highest content. The essential amino acid index (EAAI) was highest in high-pond farmed fish but lowest in the wild fish. Furthermore, there were 26 species fatty acids found in the two kinds of farmed fish but only 24 species were found in the wild fish. The contents of polyunsaturated fatty acids (PUFA), n-6 series C18:2n6c were highest in the two farmed fishes, while those of the C22:6n3(DHA) and C20:5n3 (EPA) of n-3 series were significantly higher in the wild fish. The ratio of n-3/n-6 and the content of DHA+EPA in the wild fish were significantly different from the two farmed fishes (P<0.05). Thus, it is revealed that the farmed S. oramin's nutrition and flavor are better than the wild ones, but they lack n-3 PUFA including DHA and EPA.
Study on adsorption performance of zinc-based metal-organic framework for trimethylamine
LYU Daofei, LIN Jieling, XU Feng, YUAN Wenbing, ZHANG Yan, CHEN Xin
 doi: 10.12131/20220160
[Abstract](19)
Abstract:
Rich in proteins and other active substances, seafoods have been widely used in the food and cosmetic industries. How to remove fishy substances such as trimethylamine from seafoods with high selectivity is a challenge for the current seafood processing. In this paper, zeolite imidazole framework-8 (ZIF-8), zeolites socony mobil-5 (ZSM-5) and activated alumina were characterized by powder X-ray diffraction and scanning electron microscopy, and their adsorption performance for the typical fishy substance (trimethylamine) was also investigated. Adsorption kinetics tests show that the adsorption saturation of the three adsorbents reached at about 600 min in a 200 mg·L−1 trimethylamine solution. The adsorption isotherms of the three adsorbents at 25 ℃ were tested and their adsorption capacities for trimethylamine followed a descending order of ZIF-8 (517.1 mg·g−1) > activated alumina (401.8 mg·g−1) > ZSM-5 (390.3 mg·g−1). Under the same conditions, the adsorption uptake of trimethylamine on ZIF-8 was 3.2 times higher than that on activated carbon, exceeding those of most materials in the same period. Fourier transform infrared spectroscopy tests and Zeta potential tests show that the adsorption interactions between ZIF-8 and trimethylamine were dominated by C-H···π interaction, C-H···N interaction and electrostati force.
Species identification and morphology of fish eggs from Jiangmen coastal waters in spring using DNA barcoding
CHEN Jing, HUANG Delian, WANG Xuehui, XU Lei, ZHANG Jian, LI Yafang, NING Jiajia, WANG Lianggen, LIU Shuangshuang, LIN Zhaojin, DU Feiyan
 doi: 10.12131/20220028
[Abstract](149)
Abstract:
Jiangmen is located in the southwest of the Pearl River Estuary. It is the spawning ground and nursery ground for a variety of small fish.To identify the species of fish eggs from Jiangmen coastal waters of the Pearl River Estuary in sping based on DNA barcoding analysis, we described and preliminarily classified the morphological characteristics of fish eggs. We acquired a total of 13 taxa, which belonged to three orders and ten families. Four and eight taxa were identified to species and genus levels, respectively (Ambassis gymnocephalus, Gerres limbatus, Sillago sihama, Cynoglossus puncticeps, Sardinella sp., Stolephorus sp., Acanthopagrus sp., Alepes sp., Johnius sp., Sillago sp. and Cynoglossus sp.). One taxon was identified in family's Leiognathidae sp.. The results demonstrate that most fish eggs collected in the survey area can be classified by morphological characteristics such as shape, fish eggs size, perivitelline space, number, and pigment distribution of oil globules. In addition, the colour, amount and distribution of pigments on the embryo are also important in species identification when the embryo is well developed. However, it is difficult to distinguish the closely related species only by the morphological characteristics of a single developmental stage. Further morphological studies should be conducted in the future.
Study on habitat of Coilia mystus in Pearl River Estuary, China
XIE Yufang, WU Peng, LIU Yong, XIAO Yayuan, TANG Guanglong, WANG Teng, LIN Lin, LI Chunhou
 doi: 10.12131/20220029
[Abstract](26)
Abstract:
Based on the date collected by bottom-trawl in the Pearl River Estuary during winter in 2019 and summer in 2020, we constructed the habitat suitability index (HSI) model of Coilia mystus, taking the water depth, bottom water salinity, bottom water temperature, as well as bottom dissolved oxygen as indicator environment indicators. The analytic hierarchy process (AHP) was used to calculate the weight of the indicators. The arithmetic mean (AMM) and the geometric mean (GMM) were used to build model. Then a suitability curve was developed and the HSI of Coilia mystus was calculated. Results show that the optimal bottom water salinities for C. mystus in the Pearl River Estuary in winter and summer were 21.03−30.55 and 20.25−25.82, respectively; the mass concentrations of suitable dissolved oxygen were 6.79–7.28 and 3.85–4.01 mg·L−1, respectively; the suitable water depths were 11.69–20.10 and 7.80–9.23 m, respectively; the suitable bottom water temperatures were 19.84–19.95 and 28.36–9.44 ℃, respectively. The sites with the HSI value greater than 0.5 accounted for 17.39% of the total survey sites. The study shows that the suitability of C. mystus was low, and its suitable habitats in the Pearl River Estuary are mainly located in the Sousa chinensis Nature Reserve in the Neilingding sea area.
Effects of dietary supplementation with powder of Antarctic krill (Euphausia superba) on growth performance, body composition and color of Litopenaeus vannamei
LI Wenheng, WANG Haitao, SHAN Hongwei, GAO Chang, LI Jiqing
 doi: 10.12131/20220074
[Abstract](39)
Abstract:
To determine the application effect of Euphausia superba powder (PE) in shrimp culture, we designed five groups [S0 group (no PE supplementation), S5 group, S10 group, S15 group, and S20 group (5%, 10%, 15% and 20% PE supplemented to the feed, respectively)] for a 35-day experiment on the Litopenaeus vannamei [Body mass of (7.27 ± 0.88) g]. The effect of dietary supplementation with PE on the growth performance, body composition and color of L. vannamei were evaluated. The results show that: 1) PE supplementation improved the survival rate (SR) of L. vannamei significantly (P<0.05), and the final body mass (FBW), weight gain rate (WGR) and specific growth rate (SGR) of L. vannamei in S15 group were significantly higher compared with the other groups (P<0.05). 2) With the increase of PE supplementation, the crude fat content of L. vannamei increased gradually, and those in S10 group, S15 group and S20 group were significantly higher than that in the S0 group (P<0.05). Additionally, the brightness (L*) of the cephalothorax and the yellowness (b*) of the carapace of L. vannamei decreased gradually, which were significantly lower than those in S0 group (P<0.05). 3) PE supplementation to the feed increased the astaxanthin content in the hepatopancreas and crustacean of L. vannamei significantly (P<0.05), and the effect was positively associated with PE supplementation. The expression level of the LVPBP75 related to body color was also positively correlated with PE supplementation. The results indicate that dietary supplementation with PE, especially the supplementation with 15% PE, can improve the growth, astaxanthin content, body color as well as expression level of LVPBP75 of L. vannamei.
Heavy metal enrichment characteristics and risk assessment of typical fishes in tropical seagrass beds
JIANG Rui, WU Yunchao, Huang Xiaoping, Lui Songlin, CHEN Qiming
 doi: 10.12131/20220118
[Abstract](30)
Abstract:
The ingestion of seagrass by herbivorous fish will affect the transfer process of metal elements in seagrass beds, and the accumulation of heavy metals will cause human ingestion risks. Taking two typical fish species (Siganus guttatus and S. fuscessens) eating seagrasses in two tropical seagrass beds as main research objects, we verified the enrichment of heavy metals and their contamination and dietary exposure risk in seagrass bed environment and fishes. Then we further explored the transfer characteristics of heavy metals in seagrass bed ecosystems. The results show that the contents of Cu, Cd, Zn and Pb in fish muscles were at a low level. The Cu and Pb, Zn and CD showed significant positive correlation. The enrichment effect of Zn and Cu was greater than that of Cd and Pb, but only Zn showed potential enrichment effect in these two fish muscles. The Zn contents in fishes showed serious pollution risk, while Pb contents showed slight pollution, but the contents of Cu and Cd were at a normal risk level. The health risk of eating these two typical fish is extremely low. Due to the different growth rate and food sources, the content, pollution and enrichment of heavy metals in S. fuscessens are slightly higher than those in S. guttatus. The contents and enrichment of heavy metals in seagrass beds environment are generally higher than those in fishes. The accumulation of heavy metals mainly occurs in seagrass, and the heavy metal content in fish decreases with higher trophic levels.
Study on lipid accumulation and contribution to reproductive energy in female Illex argentinus
SONG Wei, ZANG Na, FENG Yixuan, LIN Dongming
 doi: 10.12131/20210348
[Abstract](46)
Abstract:
In order to better understand the accumulation of tissue fat and its contribution to reproductive energy during gonadal development of Illex argentinus, by using tissue energy density measurement technology and fat extraction technology, we measured and analyzed the energy density of mantle soma, digestive gland, ovary and oviduct eggs of female I. argentinus before and after degreasing, as well as the fat content per unit mass, fat energy and proportion of each tissue. Results indicate that the energy density of all tissues decreased significantly after lipid extraction. During the course of maturation, female I. argentinus maintained a relative stable level of the lipid content and percentage of lipid energy in mantle soma and oviduct eggs. However, there was a significant decreasing trend in the lipid content and percentage of lipid energy in the digestive gland but an increasing trend in the ovary (maximum in Phase IV) along with maturation. Furthermore, Pearson's r analyse indicates that there was significantly negative relationship in the lipid content, lipid energy and percentage of lipid energy between gonadal tissues (combination of ovary and oviduct eggs) and digestive gland, but no significant relationship between gonadal tissues and mantle soma. In summary, female I. argentinus exhibits tissue-specific lipid content and lipid energy accumulation. The lipid content has significant contribution to the reproductive energy, and lipids in the gonadal tissues are apparently derived from concurrent food intake, which further supports the argument that energy allocation to reproduction in I. argentinus mainly depends on the income resources.
Effects of nanometer selenium on the immune protection and antioxidant ability of Eriocheir sinensis under hypoxia stress
JIA Huining, SHI Miaomiao, BIAN Yongle, SHI Chongjing, LIU Hengwei, SONG Xuehong, QIN Fenju
 doi: 10.12131/20220106
[Abstract](25)
Abstract:
In order to investigate the effects of nanometer selenium (nano-Se) on immune protection and antioxidant capacity of Eriocheir sinensis under hypoxia stress, we fed E. sinensis with different doses of nano-Se (0, 0.1, 0.2, 0.4, 0.8 and 1.6 mg·kg−1) in basic diets for 90 d. After the feeding, we conducted a hypoxia stress test and injected Aeromonas hydrophila under hypoxia stress. The results show that: 1) The mortality of E. sinensis under hypoxia stress and E. sinensis infected with A. hydrophila under hypoxia stress reached 62.45% and 100%, respectively. The levels of hemocyanin and the hemocyte count in crab hemolymph, and the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in crab tissues increased significantly under hypoxia stress for 12 h (P<0.05), and there was a downward trend under stress to 24 h. The contents of lactic acid (LD) and malondialdehyde (MDA) continued to rise from 12 to 24 h under hypoxia stress. 2) Appropriate addition amount (0.1−0.4 mg·kg−1) of nano-Se reduced the mortality of E. sinensis significantly under hypoxia stress and the lethality of A. hydrophila under hypoxia stress (P<0.05), increasing the levels of hemocyanin and the hemocyte count and the activities of antioxidant enzymes (SOD, CAT, GSH-Px) under hypoxia stress significantly, but decreasing the contents of LD and MDA (P<0.05). The addition of 0.8−1.6 mg·kg−1 nano-Se had aggravated hypoxia stress injury. These results indicate that appropriate addition of nano-Se to the diets can improve the decrease of immune response and antioxidant ability of E. sinensis under hypoxia stress, and the optimal dose of nano-Se in basal diets is 0.2 mg·kg−1.
Effects of Bacillus on growth and survival, immunity and digestive enzyme activities of Babylonia areolata
ZHANG Yuwei, ZHAO Wang, DENG Zhenghua, HUANG Xingmei, WEN Weigeng, SUN Jingfeng, WANG Ruixuan
 doi: 10.12131/20220060
[Abstract](44)
Abstract:
During the growth and development of Babylonia areolata from early veliger larva to juvenile, we used bacillus (Bacillus coagulans, B. licheniformis) and antibiotics (sulfamethoxazole) for artificial regulation to study their effects on the growth, survival, immune and digestive enzyme activities of B. areolata. The results show that bacillus and sulfamethoxazole promoted the growth of each trait index of B. areolata, and the difference among them was not significant (P>0.05). The survival rate of the bacillus group was significantly higher than that of the control group and the sulfamethoxazole group in the later veliger larva stage (P<0.05). The activities of AKP, ACP, CAT, POD, MDA, GSH-Px, TAOC, SOD, LPS and AMS in bacillus group were higher than those in the control group and the sulfamethoxazole group.The results show that appropriate use of bacillus (B. coagulans and B. licheniformis) during the seedling breeding of B. areolata can improve the immunity and disease resistance of the body, increase the activity of digestive enzymes, promote the growth of larvae and improve the survival rate, and the effect is better than that of sulfamethoxazole.
Response of caspase genes to Streptococcus agalactiae in cells of spleen of golden pompano (Trachinotus ovatus)
GAO Jie, GUO Huayang, LIU Mingjian, LIU Baosuo, ZHU Kecheng, ZHANG Nan, GUO Liang, ZHANG Dianchang
 doi: 10.12131/20220099
[Abstract](55)
Abstract:
In order to explore the response of apoptosis related genes in the spleen of Trachinotus ovatus infected by Streptococcus agalactiae, we infected the spleen tissues of T. ovatus by S. agalactiae for a pathological observation. The blood routine indexes of the fish before and after infection, as well as different times (0 h, 6 h,12 h, 24 h, 48 h, 72 h, 96 h, 120 h) after infection, the serum lactate dehydrogenase (LDH), spleen alkaline phosphatase (ALP), and acid phosphatase (ACP) and quantitative analysis of Caspase-3, Caspase-8, and Caspase-9 genes. The results reveal that after artificial infection with S. agalactiae, the body of T. ovatus showed obvious pathological changes, mainly manifested as protruding eyes, turbidity and bleeding. Histopathological observation shows that the spleen tissue had inflammatory lesions. Compared with the control group, the number of red blood cells (RBC), hemoglobin concentration (Hgb) and hematocrit (HCT) in the infected group decreased significantly, while the number of white blood cells (WBC), neutrophils (NE) and lymphocytes (lym) increased, and the mean red blood cell volume (MCV) increased. The activities of serum LDH, spleen ALP and ACP were up-regulated with time. The expressions of Caspase-3, Caspase-8 and Caspase-9 were significantly up-regulated in spleen. The results show that the body of T. ovatus infected by S. agalactiae had obvious immune response.
Characteristics of feeding acoustic signals of Litopenaeus vannamei fed with pellets of different sizes
CAO Zhengliang, SHEN Mengting, LI Zhaocheng, WANG Zihao, WANG Xiuxiu
 doi: 10.12131/20220080
[Abstract](73)
Abstract:
With passive acoustic method, we recorded the acoustic signals of Litopenaeus vannamei (Body length of 9−10 cm) feeding pellets of different sizes (0.4, 0.8 and 1.2 mm) in the laboratory. The results of the waveform, spectrogram and spectrum map reveal that the characteristics of feeding acoustic signals by feeding pellets of different sizes were similar, and the frequencies were 5−45 kHz. The spectral frequency peak of acoustic signals of the shrimps fed with pellets of 0.4 and 0.8 mm was about 17 kHz, and that of shrimps fed with pellets of 1.2 mm was about 10 kHz. In addition, there were obvious differences in the acoustic signals between feeding Nereis succinea and pellets. The frequency range of acoustic signals of feeding Nereis succinea was 5−45 kHz, and the spectral frequency peak was about 7 kHz. Finally, compared with the feeding acoustic signals of L. vannamei in farming pond, it is found that the signal characteristics collected in the pond were similar with those in the laboratory, and the only difference is that there was no secondary peak in the high frequency region of signals in the pond-cultured shrimp.
Development of vertebral column and appendicular skeleton in larval and juvenile of Platax teira
GUO Huayang, LIU Mingjian, GAO Jie, ZHU Kecheng, LIU Baosuo, GUO Liang, ZHANG Nan, SUN Jinhui, ZENG Chen, YANG Jingwen, LIU Bo, ZHANG Dianchang
 doi: 10.12131/20220058
[Abstract](54)
Abstract:
In order to understand the developmental time sequence characteristics of the spine and appendage skeletal system of Platax teira, we stained and analyzed the spine, pectoral fin, pelvic fin, anal fin and caudal fin of P. teira larvae (0–30 dah) by the method of cartilaginous and bony staining. The results show that there were twenty four vertebrae, and the tail bone was composed of 5 subcaudal bones and 2 upper caudal bones. The development sequence of appendage branch fin bones was pectoral fin, abdominal fin, caudal fin, anal fin and dorsal fin. The first hatched fish already had pectoral branch fin bone primordium and notochord. At 4 dah, the pectoral fin and pelvic fin developed first; at 7 dah, medullary arch and vein arch appeared; at 13 dah, the morphology and number of larval bones were basically stable; at about 26 dah, ossification began in juvenile fish, and the spine and spine were the first to complete ossification; at 30 dah, the larvae entered the juvenile stage, and their appearance has been fixed. The typical characteristics were three black bands on the head, trunk and tail, and the body was white silver. When stimulated or stressed by external stimulation, the body color changed to black instantly, and the shape had no difference from that of the juvenile. The developmental sequence of the spine and appendage bones was basically the same with that of other sea fish, but the time nodes and number of the development of bone were different. The results have important guiding significance for the development, environmental adaptation and classification of P. teira larvae.
Molecular cloning, expression profile and subcellular localization of nanos1 gene (Macrobrachium rosenbergii)
ZHOU Nan, WANG Yakun, HONG Kunhao, WEI Jie, YU Lingyun, ZHU Xinping
 doi: 10.12131/20220067
[Abstract](43)
Abstract:
To investigate the function of the nanos1 gene in the reproductive development of Macrobrachium rosenbergii, we cloned its nanos1 gene and the cDNA sequence was 2 811 bp, encoding 243 amino acids. Phylogenetic analysis shows that it had the highest homology with Eriocheir sinensis, higher homology with nanos1 in fish but lower homology with mammals. We detected the expression level of the gene at different embryonic developmental stages and in larvae by real-time fluorescence quantitative PCR. The results show that the expression level of nanso1 mRNA was the highest at unfertilized stage, which was significantly higher than that at fertilized stage and other embryonic developmental stages (P<0.05). During embryonic development, the expression was the highest at fertilization stage, significantly higher than that at cleavage stage and very significantly higher than that at late embryonic development (P<0.01). The expression level of this gene at cleavage stage was significantly higher than that from blastocyst stage to larval stage. The expression level from blastocyst stage to larval stage was low and there was no difference. In situ hybridization shows that nanos1 mRNA was expressed in the cytoplasm of oocytes and primary oocytes (Oc1, Oc2, Oc3 and Oc4). The results show that nanos1 is closely related to the development of female germ cells of M. rosenbergii.
Molecular cloning and characterization in immune response of two C-type lectin genes (SaCD302 and SaMBL) from Symphysodon aequifasciatus
MA Tengfei, WEN Bin, LIU Xin, MIAO Lin, GAO Jianzhong, CHEN Zaizhong
 doi: 10.12131/20220018
[Abstract](63)
Abstract:
Symphysodon aequifasciatus has a unique parental rearing behavior. In the previous study, two C-type lectins (CTLs) were found to be highly expressed in the skin of the parent fish, but with different expression patterns. In order to investigate the difference in the potential immune functions of the specific CTLs, we cloned two CTL genes (SaCD302 and SaMBL), then simulated and analyzed their immune esponse patterns under pathological infection. The results show that the ORF region of SaCD302 and SaMBL were 741 and 795 bp in length, encoding 246 and 264 amino acids (aa), respectively. The SaCD302 sequence contained a signal peptide (aa 1–29), a C-type lectin-like domain (CTLD) (aa 32–169) and a transmembrane domain (aa 184–206). Two low complexity regions (aa 32–92 and aa 104–121) and a CTLD (aa 137–263) were expressed in SaMBL sequence. Moreover, SaCD302 and SaMBL shared the highest similarity with that of Archocentrus centrarchus. SaCD302 was highly expressed in the head kidney, followed by the liver and gill. Compared with the intestine, liver, spleen and gonads, the skin had the higher expression of SaMBL. After Aeromonas hydrophila infection, SaCD302 expression was significantly upregulated in the spleen, head kidney, intestine and skin, while SaMBL was only upregulated in the head kidney, intestine and skin, and these two genes were expressed in different temporal manners, indicating that they might play different roles in the immune defense of S. aequifasciatus.
Geostatistics-based study on spatial-temporal distribution of Auxis thazard in South China Sea
ZHOU Xingxing, FAN Jiangtao, YU Jie, XU Shannan, CAI Yancong, CHEN Zuozhi
 doi: 10.12131/20210327
[Abstract](107)
Abstract:
In this study, we analyzed the spatial-temporal distribution characteristics and ecological dynamics of Auxis thazard by geostatistical methods based on the data from the light mask fishery survey conducted in the South China Sea from 2016 to 2017. The results show that the distribution of A. thazard in the South China Sea was mainly low-density, and there were few high-density sea areas. The seasonal aggregation characteristics of A. thazard in offshore shallow waters were obvious, and the resource density index followed a descending order of summer>spring>autumn. The spatial distribution of A. thazard fishery had strong spatial heterogeneity, with the proportion of spatial structure over 75% in four voyages. The spherical model was the main variation model, and the average main variation range was 1.861 0°. The A. thazard in the South China Sea was obviously characterized by southwest-northeast migration, and its spatial layout had a patch-like spatial distribution. The results can better reflect the spatial-temporal distribution characteristics of the A. thazard fishery in the South China Sea, which provides scientific basis for its fishery analysis and management.
An investigation of large-size light falling-net fishing vessels operating in South China Sea based on Beidou VMS data
QIAN Jing, LI Jiajun, CHEN Zuozhi, MA Shengwei, ZHANG Peng, QIU Yongsong, CAI YanCong
 doi: 10.12131/20220001
[Abstract](106)
Abstract:
Beidou vessel monitoring system (VMS), which can be used to monitor fishing operations of the vessels, has the potential to provide scientific foundation for management of the fishery. We explored the large-size light falling-net fishery in the South China Sea based on VMS data in 2018. The Beidou VMS obtained a total of 8 821 681 records of 121 vessels from Guangdong, Guangxi and Hainan Provinces, with an average of 406 records per vessel per day. There is difference in the frequency of Beidou VMS transmission among the vessels from different provinces, and VMS signals were more frequently transmitted when a vessel was operating in the open South China Sea than when it was fishing along the coast. The vessels mainly operated fishing in the Nansha Islands in spring, off the Pearl River mouth in summer, and in the Beibu Gulf and Zhongsha and Xisha Islands waters in autumn and winter. In 2018, the vessels operated 19 986 fishing days in the South China Sea, decreasing from 7 768 d (38.87%) in spring, 4 738 d (23.71%) in autumn, 4 406 d (22.05%) in winter to 3 074 d (15.38%) in summer. Moreover, we discussed the advantages and disadvantages of Beidou VMS in monitoring the large-size light falling-net vessels. It is showed that using Beidou VMS to study the large-scale light falling-net vessel in the South China Sea can monitor their spatial distribution and dynamic changes quickly and comprehensively.
Effect of low-temperature acclimation on survival, non-specific immune and antioxidant indexes of Epinephelus fuscoguttatus ♀×E. lanceolatus
YUAN Zhongjin, CEN Jianwei, LI Laihao, YANG Xianqing, HUANG Hui, WEI Ya, HAO Shuxian, ZHAO Yongqiang, WANG Yueqi
 doi: 10.12131/20220042
[Abstract](107)
Abstract:
In order to obtain the best acclimation temperature conditions for Epinephelus fuscoguttatus ♀×E. lanceolatus ♂, we decreased the water temperature to 24, 20, 18 and 16 ℃ at the rate of 0.5−1 ℃·h−1, then recorded the physiological responses and survival time, as well as the changes of water quality, non-specific immune index and antioxidant indicator. The results show that the survival time of the grouper increased with the decrease of temperature within the range of 24−16 ℃. When the water temperature was maintained at 16 ℃, the concentration of total ammonia nitrogen (TAN) increased slowly, and the survival time was the longest, up to 109 h. The non-specific immune and antioxidant parameters changed after the grouper being cultured at different temperatures for 48 h. Compared with control group, the contents of complement protein 3 (C3), globulin (GLB) and total protein (TP) increased in 16 ℃ group significantly, while the other indexes had no significant changes. The activities of superoxide dismutase (SOD) and catalase (CAT) in the liver tissue in 16 ℃ group increased significantly. However, the activity of glutathione peroxidase (GPX) decreased significantly, but higher than that of the other temperature groups. Compared with other temperature treated groups, the content of malondialdehyde (MDA) decreased significantly. Thus, 16 ℃ temporary culture can not only maintain good water quality, but also reduce the metabolic level of fish and maintain the homeostasis of internal environment, so as to reduce the damage caused by oxidative stress reaction. It is suitable for temporary culture and transportation of Epinephelus fuscoguttatus ♀×E. lanceolatus ♂.
Genetic structure analysis of Ochetobius elongatus between Yangtze River and Pearl River using multiple loci
CHEN Weitao, DUAN Xinbin, GAO Lei, LI Xinhui, YANG Jiping, WANG Dengqiang
 doi: 10.12131/20220007
[Abstract](112)
Abstract:
Taking seven Ochetobius elongatus individuals collected from the Yangtze River during field sampling as samples, we sequenced two mitochondrial genes (Cytb and ND2) and two nuclear genes (mhy6 and RAG2) for the seven samples using Sanger sequencing technique. Combined with the published four gene sequences of 52 O. elongatus samples in the Pearl River, we explored the genetic structure of O. elongatus between the Pearl River and the Yangtze River, so as to provide scientific support for its conservation. We appled phylogenetic analyse, haplotype networks and divergence time estimation in the study. Phylogenetic analyse and haplotype networks reveal that O. elongatus populations in the two rivers generated two deep and independent lineages and formed private alleles at the nuclear gene level. The results suggeste that O. elongatus populations in the two rivers evolved independently without gene flow. The rapid lifting of the Qinghai-Xizang Plateau during the middle Pleistocene might be an important factor that triggered the splitting of O. elongatus populations in the two rivers before 0.38−0.76 million years ago (Ma). Given that strictly geographical division of O. elongatus populations between the two rivers at both mitochondrial and nuclear gene levels, we suggest that these two populations should be regarded as two evolutionary significant units, and targeted strategies should be urgently put forward to manage and protect its resources.
A preliminary study on reproduction and feeding habits of Lutjanus gibbus from Meiji Reef of Nansha
WANG Teng, LIU Yong, LI Chunran, LI Chunhou, TANG Guanglong, XIAO Yayuan, LIN Lin, WU Peng
 doi: 10.12131/20210379
[Abstract](112)
Abstract:
Lutjanus gibbus, a kind of coral reef fish with delicious meat and high economic value, whose spawning aggregation can easily lead to overfishing. Based on 67 individuals of L. gibbus collected by diving fishing in the waters of Mischief Reef in July 2020, we investigated its basic biological characteristics, including sex ratio, sexual maturity body length, egg diameter characteristics, fecundity and feeding habits. The results show that the ratio of female to male of L. gibbus was 2:1; the 50% sexually mature body lengths of males and females were 204.757 and 201.623 mm, respectively; the egg diameter of stage IV gonadal was 0.176–0.419 mm with an average of 0.296 mm; the frequency distribution of egg diameter was unimodal. The fecundity of L. gibbus was 51 858–276 205 eggs with an average of 139 145 eggs. Its fecundity had a significant power function relationship with body length and body mass. The preys of L. gibbus from Meiji Reef were crabs, fish, snails, shellfish and shrimps. The stable isotope study shows that the average trophic level of L. gibbus was 3.33, and its feeding habits changed significantly with individual development (the niche width was narrower and the trophic level was higher).
Effect of trichloroisocyanouracic acid on antibiotic resistance genes in aquaculture water of shrimp
XIA Taotao, SU Haochang, HU Xiaojuan, XU Yu, WEN Guoliang, CAO Yucheng, YU Zhaolong
 doi: 10.12131/20210361
[Abstract](122)
Abstract:
In order to explore the feasibility of removing and controlling the spread of antibiotic resistant genes (ARGs) by the fishing oxidant trichloroisocyanuric acid (C3Cl3N3O3) in the aquaculture water environment, we applied real-time quantitative PCR to monitor and determine the ARGs concentrations in the offshore source water, storage water of sedimentation tank and reserved water after oxidation and disinfection for 29 d. The final concentration of trichloroisocyanuric acid used for oxidation and disinfection was 40 mg·L-1. The target ARGs were commonly found in the aquaculture environments, including sul1, sul2, tetX, tetM, floR, cmlA and qnrA. The results show that sul1, sul2, floR and tetX were the dominant ARGs among the above mentioned water samples. The number of types and total concentration of ARGs were the highest in offshore source water. The total concentrations of ARGs in the storage water of sedimentation tank were lower than those in the offshore source water, especially the concentrations of sul2 and floR were 0.86 log and 0.34 log lower than those in the offshore source water, respectively. After oxidation and disinfection by trichloroisocyanuric acid, the total concentrations of ARGs in the reserved water decreased, and compared with the offshore source water, the concentrations of sul2 and floR decreased by 1.58 log and 1.30 log, respectively. The results indicate that offshore source water is the main source of ARGs in the aquaculture environment. Oxidation and disinfection treatment on offshore source water with trichloroisocyanuric acid can reduce the concentrations of common ARGs in the aquaculture water significantly, which is helpful to prevent and control the spread of ARGs in the aquaculture environments.
Estimation of genetic parameters and its breeding progress for body mass and body length of Cyprinus carpio
DU Xuesong, CHEN Zhong, WEN Luting, PAN Xianhui, HUANG Yin, ZHOU Kangqi, LIN Yong, LI Zhe, LUO Hui, QIN Junqi
 doi: 10.12131/20210353
[Abstract](89)
Abstract:
In order to improve the growth rate of the cultured population of Cyprinus carpio in Quanzhou, two generations of breeding were carried out by family breeding method. The body mass and body length indexes of 3 699 individuals in 121 families of G0, G1 and G2 generations of C. carpio were measured. The heritability, phenotypic correlation and genetic correlation of body mass and body length traits were estimated by mixed linear model. The selection progress of G0 ~ G2 generations was evaluated by the method of breeding value and least square value estimation based on target traits. The results show that the variable coefficient, heritability estimates, correlation value between heredity and phenotype in body mass were 0.50 0.72, 0.132 (P<0.01) and 0.921 (P<0.01), respectively. The variable coefficient, heritability estimates, correlation value between heredity and phenotype in body length was 0.18 0.22, 0.122 (P<0.01) and 0.995 (P<0.01), respectively. The value of selective reaction in body mass estimated by breeding value based on target traits and least square estimation was 12.82% and 15.45%, respectively, while 2.76% and 6.60% in body length, respectively, which indicates that the evenness of body mass was low, and it did not participate in breeding production, but had high breeding and improvement potential. In general, this population of C. carpio obtained effective genetic progress after two successive generations by the family breeding, but with a modest progress. In is suggested that molecular-assisted selection (MAS) and marker-assisted large-scale mixed families' selection should be adopted in the future breeding so as to improve the breeding efficiency.
A preliminary study on community structure of mesopelagic fish in cold seep of Xisha Islands
TIAN Han, JIANG Yan'e, ZHANG Jun, CHEN Zuozhi, XU Shannan, ZHU Jiangfeng
 doi: 10.12131/20210370
[Abstract](158)
Abstract:
We used the midwater trawl to investigate the mesopelagic fish resources inside and outside the cold seep in the Xisha Islands. A total of 106 species of mesopelagic fish had been identified which belong to 62 Genera, 31 Families and 12 Orders, with the dominant groups being Myctophiformes and Stomiiformes. Among them, 84 species of fish belonging to 54 Genera, 30 Families, 11 Orders were collected inside the cold seep; while 60 species of fish belonging to 32 Genera, 13 Families and 6 Orders were collected outside the cold seep. There were 38 shared species of mesopelagic fishes belonging to 22 Genera, 9 Families, 5 Orders inside and outside the cold seep, and the main shared species were Chauliodus sloani, Ceratoscopelus warmingii and Diaphus garmani. The Jaccard species similarity index shows that the species similarity of mesopelagic fish was moderately different inside and outside the cold seep (I=35.8%). The average taxonomic distinctness (Δ+) of mesopelagic fish was significantly higher inside the cold seep than that outside (P<0.01), but the variation in the taxonomic distinctness (Λ+) of mesopelagic fish community was inverse (P<0.01). From the perspective of pelagic distribution, there were significant differences in the species composition of the mesopelagic fish communities inside and outside the cold seep (P<0.01). In the surface waters, the mesopelagic fish diversity inside the cold seep was lower than outside, while it’s the opposite in the deeper water layers. There was a correlation between the fish communities at different stations inside and outside the cold seep in terms of water stratigraphy and timing, with higher similarity between the deeper layers inside the cold seep; and higher similarity between the nocturnal surface layers inside the cold seep area and the nocturnal surface layers outside the cold seep. The results show that there are differences in the mesopelagic fish communities inside and outside the cold seep, with more species of mesopelagic fish inside the cold seep and a higher diversity of species in the deeper water layers. Eight key species that distinguish the mesopelagic fish communities in the waters inside and outside the cold seep include Bolinichthys longipes and Vinciguerria nimbara, having a cumulative contribution of 56.06%.
Effects of cbpD gene on virulence and related biological characteristics of Vibrio alginolyticus
SU Wenxiao, DENG Yiqin, ZANG Shujun, WANG Qian, LIN Ziyang, FENG Juan
 doi: 10.12131/20220025
[Abstract](123)
Abstract:
In order to study the virulence and related biological characteristics of Vibrio alginolyticus after the absence of Chitin-binding protein D (CbpD) gene, the cbpD gene deletion mutant strain of V. alginolyticus ZJ-T was constructed by the homologous recombination technique. Moreover, the virulence to Danio rerio and other related physiological processes were compared between the wild type strain and the cbpD gene mutant strain, including the growth ability, bacterial colony morphology, motility, extracellular protease secretion activity, hemolytic activity and antibiotic sensitivity, biofilm formation, hydrogen peroxide and copper ion resistance as well as ion absorption capacity. The results show that due to the absence of cbpD gene, the swimming motility, swarming motility and extracellular protease activity all reduced, the resistance to copper ion of the mutant strain strengthened, and its virulence to D. rerio was weakened. However, the deletion of cbpD gene did not affect the growth of the strain in nutrient-rich medium, biofilm formation, hemolytic activity, stress response to H2O2, uptake and utilization of iron and sensitivity to most antibiotics. In conclusion, the results indicate that cbpD may promote the virulence by positively regulating the motility, extracellular protease secretion activity of V. alginolyticus.
Effect of Haematococcus pluvialis on growth performance, antioxidant capacity and immune responses of Lates calcarifer
YU Wei, CHEN Xueqing, YANG Yukai, HUANG Xiaolin, HUANG Zhong, LI Tao, MA Zhenhua, WU Qia'er, YU Gang, ZHOU Chuanpeng, LIN Heizhao
 doi: 10.12131/20220002
[Abstract](150)
Abstract:
To investigate the effects of Haematococcus pluvialis on the growth performance, antioxidant capacity, haematological indexes and immune responses of Lates calcarifer, we had fed L. calcarifer by six diets containing 0 (C), 0.2% (H1), 0.4% (H2), 0.6% (H3), 0.8% (H4) and 1.0% (H5) H. pluvialis for eight weeks. The results show that the specific growth rate (SGR) and weight gain rate (WGR) in H2, H3, H4 and H5 groups were significantly higher than those of the control group (P<0.05). Compared with the control group, the whole-body lipid protein content decreased significantly in the treatment groups (P<0.05). The dietary H. pluvialis improved the total antioxidant capacity (T-AOC) significantly (P<0.05), while the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) activities and malondialdehyde (MDA) content were significantly lower than those of the control group (P<0.05). Compared with the control group, in H3, H4 and H5 groups, the levels of red blood cell (RBC) and hemoglobin (Hb) increased (P<0.05), but the levels of triglyceride (TG), cholesterol (TCHO) and low-density lipoprotein cholesterol (LDL-C) decreased significantly (P<0.05). The complement 4 (C4) and immunoglobulin (Ig) contents and lysozyme (LYZ) activities improved significantly in the treatment groups than in the control group (P<0.05). The regression analysis on the WGR indicates that the recommended optimum dietary H. pluvialis level for the optimal growth of L. calcarifer is 0.66%.
Seasonal variatons of digestive tract index, histology characteristics and enzyme activity of Holothuria edulis
TAN Chunming, ZHAO Wang, MA Zhenhua, YU Gang
 doi: 10.12131/20210356
[Abstract](144)
Abstract:
To reveal the environmental regulation mechanism and aquaculture of tropical sea cucumber, and provide scientific basis for its artificial breeding, we studied the seasonal variations of physiological and biochemical conditions of Holothuria edulis, monitored the changes of the digestive tract index, histology characteristics and enzyme activities of H. edulis. Results show that the feeding state of H. edulis was relatively vigorous in spring and summer, and exhibited similar characteristics to Stichopus japonicus's aestivation in winter, which is characterized by the decline of body mass, the atrophy of digestive tract tissue, the emergence of a large number of cavities due to cell apoptosis, the decrease of the thickness of transverse folds and the decrease of the density of columnar epithelium in the intestinal wall structure. The digestive enzymes and immune enzymes activities of the digestive tract tissues were the highest in March and June, respectively. In December, except for the alkaline phosphatase activity that regulates metabolism, all the others were at low values. Therefore, it is preliminarily judged that H. edulis have hibernation phenomenon.
Preparation of active peptide from Pinctada martensii adductor muscle and evaluation of its auxiliary hypoglycemic effect
LIAO Jin, LIN Haisheng, WU Bin, QIN Xiaoming, CAO Wenhong, GAO Jialong, ZHENG Huina, ZHANG Chaohua, TAN Qiqing
 doi: 10.12131/20210377
[Abstract](168)
Abstract:
To explore the potential nutritional value of shellfish active peptides, we hydrolyzed the adductor muscles of Pinctada martensii, Chlamys nobilis and Atrina pectinate by compound protease and flavor protease, and investigate the effects of protease types, enzymolysis time, pH, temperature and enzyme dosage of the enzymatic hydrolysate on the inhibitory activity on α-glucosidase, so as to screen out the optimal enzymatic hydrolysate and further verify its auxiliary hypoglycemic activity through animal experiments. Results show that the hydrolysate of three kinds of adductor muscle had α-glucosidase inhibitory activity. The enzymatic hydrolysate of Pinctada martensii adductor (EHPA) muscle was most active at enzymolysis time of 3 h, pH of 7.0, enzymolysis temperature of 50 ℃ and enzyme dosage of 5 000 U·g−1. Under these conditions, the inhibitory activity of α-glucosidase was 24.54%, which was related to the short chain polypeptide content. The animal experiments indicate that EHPA had the activity of auxiliary hypoglycemia. In summary, EHPA has potential application value in developing functional food for auxiliary hypoglycemic function.
Optimization on calculation method of horizontal illuminance for metal halide fish lamp around fishing boats
WANG Weijie, WAN Rong, KONG Xianghong, XIAO Yuchen
 doi: 10.12131/20210320
[Abstract](101)
Abstract:
Monte Carlo simulation is an effective numerical simulation approach to calculate illuminance at target region by discretizing beam into photons and calculating illuminance based on tracking photon path. In order to calculate the horizontal illumination distribution of the fish lamp accurately, taking the metal halide fish lamp as an example, we analyzed and optimized the photon number and photon emission model within Monte Carlo (MC) simulation. For the photon number, we carried out numerical simulation by setting different photon numbers to analyze its influence on the stability of simulation results. Meanwhile, we presented a photon emission optimization model based on the luminosity distribution data of fish lamp and verified by the measured data. The results show that: 1) The larger the number of the simulated photon, the better the stability of the simulation result. Taking the calculation point with a horizontal distance of 5m from the lamp as an example, when the value exceeded 108, the coefficient variance (CV) was 0.07% and when the value exceeded 1010, the CV was 0.05%. 2) By using the optimization model, the mean relative error (MRE) between the simulated and measured data reduced from 0.051 2 to 0.045 3. In addition, the light field illumination of fishing boats in the actual working environment was calculated by using the optimization model. The average error between the calculated value and measured value was about 0.052 3.
Site selection of marine ranching in Wailingding Island sea area of Zhuhai
XIE Xiaoyan, CHEN Pimao, TONG Fei, YUAN Huarong, FENG Xue, YU Jing, YU Jie, SHU Liming
 doi: 10.12131/20210241
[Abstract](236)
Abstract:
Site selection of marine ranching plays a key role in the construction of marine ranching. Appropriate location is the precondition of a successful marine ranching construction. In this study, we selected 34 indicators as factors for marine ranching suitability evaluation (Coastline stability, marine functional zoning, marine ecological red lines, aquaculture water tidal flat planning, marine engineering and facilities), and established an index system of marine ranching location. On this basis, according to the actual situation of Wailingding Island of Zhuhai, we selected eight indexes including length and area change intensity of island coastline, marine functional zoning, marine ecological red line, beach planning of aquaculture waters, ports, anchorages, navigable areas and submarine pipelines, to evaluate the suitability of marine ranching site selection in that sea area by using the spatial analysis method of GIS. The results show that there was no most suitable and more suitable area for marine ranching construction, and the areas of generally suitable and unsuitable areas for marine pasture construction were 33.09 and 45.59 km2, respectively. The suitable area for marine ranching construction was similar to the existing artificial reefs and planned marine ranching areas in Zhuhai.