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Cloning, sequence characterization analysis and prokaryotic expression of Anguilla anguilla RIG-I gene 2022, 44(5): 513.  Abstract ( 166 )   PDF (2877KB) ( 520 )   Cloning, sequence characterization analysis and prokaryotic  expression of Anguilla anguilla RIG-I gene LI Yingying1,2， CHEN Xi1， YANG Jinxian1， CHEN Qiang1， SONG Tieying1， GE Junqing1 (1. Institute of Biotechnology, Fujian Academy of Agricultural Science, Fuzhou350003, China;  2. Fujian Province Engineering Technology Research Center of Breeding Animal Nutrition and New  Type of Feed Enterprise, Fuzhou350003， China ) Abstract: Retinoic acidinducible gene I (RIGI) is one of RIGI like receptors (RLRs), a member of DExD/H Box RNA helicase family. There are two cascades of caspase enrichment domains (CARD) at its Nterminal, which are cytoplasmic sensors of viral RNA. They can recognize viral mRNA and activate RLRs to bind to specific ligands during viral invasion, inducing the production of interferon (IFN) and inflammatory factors to resist viral invasion. RIGI is inclined to recognize short dsRNA and 5 ′PPP dsRNA, and keeps selfinhibition state without stimulation by dsRNA. RIGI can recognize both RNA virus and DNA virus, thus RIGI and its mediated immune response play an important role in the host antiviral immune response during the infection of DNA viruses. Compared with mammals, the acquired immune system of fish is not fully differentiated, and its resistance to pathogen invasion is more dependent on its natural immune system. A large number of studies have shown that the natural immunity mediated by RIGI plays an important role in the process of fish resisting virus invasion during virus infection. RIGI is activated and specifically mediates the production of type II IFNI of zebrafish during the infection by neuronecrosis virus (NNV); RIGI and regulatory factors in its mediated signaling pathway will be activated in silver crucian carp after carp herpesvirus type II (cyprinid herpesvirus 2, CyHV2) infection. Previous studies have shown that RIGI gene and several genes in the RLRs signaling pathway of eel skin mucus are activated after infection by Anguillid herpesvirus (AngHV). In order to study the characteristics of RIGI gene of Anguilla anguilla, primers were designed to amplify its sequence. Then the target fragment was cloned into pCE2TA/Blunt Zero vector and verified by sequencing. The sequence characteristics of A. anguilla RIGI were analyzed. NCBI BLAST online tool was used to analyze the homology of the amplified sequences. The composition and physicochemical properties of nucleotide and amino acid sequences were analyzed by Protparam. Protein transmembrane domain was predicted by TMHMM2.0 analysis. The protein signal peptide structure was predicted by SignALP5.0. PSORT II was used for subcellular localization prediction. Protein secondary structure was predicted by HNN. The conserved functional domain of gene protein was analyzed by CDD. The ORF sequence fragment of A. anguilla RIGI gene was cloned into vector pET30a and transformed into Escherichia coli BL21(DE3), and then induced by IPTG at 15 ℃ for 16 h for prokaryotic expression. Bacterial bodies were collected by centrifugation, and the cell lysate, lysate supernatant and lysate precipitation were taken for SDSPAGE analysis. The induced lysate supernatant was subjected to western blot validation of RIGI expression, with mouse antiHisTag monoclonal antibody as primary antibody, and HRPlabeled sheep antimouse IgG as secondary antibody. Bioinformatics analysis showed that the ORF sequence of A. anguilla RIGI gene was 2 823 bp and encoded 940 amino acids. The sequence homology of RIGI gene between A. anguilla and A. japonica was 96.71%. RIGI might be an acidic hydrophilic protein with no transmembrane structure, no signal peptide and instability, mainly distributed in the cytoplasm, and had 6 conserved functional regions. The results of SDSPAGE showed that the expected protein bands appeared at the size of about 108 kDa for the cell lysate and precipitation after 16 h of 15 ℃ induction.RIGI protein in cell lysate precipitation was significantly higher than the supernatant, which indicated that the protein was less soluble and mainly distributed in the inclusion body. The western blot analysis showed that inducible bacteria containing the prokaryotic expression plasmid 30aRIGI were specifically detected at the size of 108 kDa by the HisTag monoclonal antibody, consistent with the expected size of the expressed protein, whereas the band for the control was about 40 kDa, indicating the realization of A. anguilla RIGI gene expression in E.coli BL21 (DE3). Two RIGI gene subtypes of A. japonica, AjRIGI and AjRIGIb, were reported. Their homology was only 39%. The RIGI gene of A. anguilla in this research had 96.71% homology with AjRIGIb, and only a few of bases had point mutations, but low homology with AjRIGI. These results provided reference for the study of A. anguilla RIGI gene. The bioinformatics analysis showed that RIGI protein was mainly located in the cytoplasm and relatively unstable, which was consistent with the previously report that RIGI was a cytosolic sensor of viral RNA and was selfinhibition without stimulation by dsRNA. Mammalian RIGI proteins generally had four conserved functional regions, from the Nterminal to the Cterminal: two tandem CARD domains, DEx D/Hbox RNA helicase domain, and Cterminal domain (CTD). According to the CDD prediction result, RIGI protein of A. anguilla had six conserved functional regions. The first two belonged to DD superfamily, and the third and fifth belonged to DEADlike_ helicase_ N superfamily and DEADlike_ helicase_ C superfamily, the fourth and sixth belonged to an alternavtive RIGI_ Family C. DD superfamily was the largest class of protein interaction modules, with a key role in cell apoptosis, necrosis and immune cell signaling pathways. It included four subfamilies: DD, death effector domain (DED), card and pyrin domain (PYD). The two domains, CARD_RIGI_r1 (cd08816) and CARD_RIGI_r2 (cd08817), belonged to the CARD subfamily of DD superfamily, indicating that the RIGI protein of A. anguilla was similar to that of mammalian RIGI protein, and there were also two tandem CARDs at the Nterminus. The Cterminal domain of A. anguilla RIGI protein belonged to RIGI_C family, i.e. CTD domain. The domain between the DEADlike_helicase_Nterminal domain and the DEADlike_helicase_Cterminal domain, belonged to the RIGI_C family which was different from the Cterminal CTD domain. This structure had not been reported in previous studies on RIGI protein, and its effect on the function of RIGI protein in A. anguilla needed to be further verified. The prokaryotic expression of RIGI protein in A. anguilla provided fundamental research on the preparation of RIGI polyclonal antibody and the mechanism of RIGI mediated natural immunity in the process of eel resistance to AngHV infection.  Keywords: Anguilla anguilla; RIGI; cloning; sequence characterization analysis; prokaryotic expression  Related Articles | Metrics

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Study on the function of P-gp protein in florfenicol metabolism of Portunus tritructus  2022, 44(5): 521.  Abstract ( 108 )   PDF (5247KB) ( 457 )   Study on the function of P-gp protein in florfenicol metabolism of Portunus tritructus  XU Yao1,2,3, SHAO Huixin2,3,4, GAO Baoquan2,3,  LI Jian2,3, CAI Yuefeng1, REN Xianyun2,3 (1. Jiangsu Key Laboratory of Bioresources and Environment/Jiangsu Key Laboratory of Marine Biotechnology, College  of Marine Science and Fisheries, Jiangsu Ocean University, Lianyungang Jiangsu222005, China; 2. Key Laboratory of  Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research  Institute, Chinese Academy of Fishery Sciences,  Qingdao Shandong2660712, China;3. Laboratory for Marine  Fisheries Science and Food Production Processes, Pilot National Laboratory for Marine Science and Technology  (Qingdao), Qingdao Shandong266071, China; 4. National Demonstration Center for Experimental Fisheries Science  Education, Shanghai201306, China) Abstract: Portunus trituberculatus is a famous swimming crab with the highest output in the north of China. With the rapid development of aquaculture industry, the environment has become increasingly deteriorated, resulting in the increase of pathogens and high incidence of disease in cultivation environments, which may cause huge economic losses to the mariculture industry and seriously hinder the sustainable and healthy development of mariculture. At present, aquatic drugs are extensively applied as effective measures to prevent and control aquatic animal disease because of their remarkable efficacy, easy production and utilization, and low cost. Florfenicol (FLR) is one of the most commonly used antimicrobial agents in aquaculture. This chemical ingredient is characterized with broad spectrum, easy absorption, wide distribution and low residue in the body after administration. FLR can bind closely to the 50S subunit of 70S ribosome of bacteria, which plays a killing role by effectively inhibitting the proteins’ biosynthesis in bacteria, and is widely used in the prevention and treatment of infections caused by Vibrio. In the actual breeding process, there are unreasonable uses of drug and even abuse of drugs. When entering the breeding environment, the antimicrobial agents will induce the opportunistic pathogens of the breeding organisms themselves; microorganisms in aquatic environments including aquaculture sediment can develop drug resistance; FLR will also remain in the cultured subjects, leading to a series of adverse responses of the body, including the induced oxidative stress, inhibited metabolism and growth process in organisms, disrupted behavior and immune response, altered transcriptional expression of key genes in related metabolic pathways, and destroyed balance of the ecological environment in aquaculture. ATPbinding cassette (ABC) transmembrane transporters (ABC transporters) are primarily involved in the active, ATPdependent transport of biological molecules across plasma membranes. The most toxicologically relevant ABC transporter is Pglycoprotein (Pgp, ABCB1), a membrane detoxification protein that can transport and expel exogenous toxic substances and harmful metabolites from the cell. To study the transport function of Pgp protein in P. trituberculatus, the fulllength sequence of ATP binding cassette transporter subfamily b1 (abcb1) was cloned via race amplification technique, named Ptabcb1. The fulllength cDNA was 4 923 bp, and the open reading frame (ORF) was 3 522 bp, encoding 1 172 amino acids. The predicted molecular weight was 127.96 kDa (GenBank ID: KY487995). Two hydrophobic transmembrane regions (TMD) and two nucleotide binding regions (NBD) were found in the cloned sequence, which were consistent with the basic structural characteristics of ABC transporters. Its primary sequence was highly conserved, displaying a typical phosphatebinding loop: Walker A and two magnesium binding sites: Walker B. In addition to these two regions, three other conserved motifs were present in the ABC cassette: the switch region, which contained a histidine loop, postulated to polarize the attaching water molecule for hydrolysis, the signature conserved motif specific to the ABC transporter, the Qloop, which interacted with γ phosphate through a water bond, the aspartic acidcontaining Dloop, and the Hloop, where the first amino acid was either isoleucine. The Walker A, Walker B, Qloop, Hloop, Dloop and switch region formed the nucleotide binding site. Sequence alignment showed that the homology between Ptabcb1 and abcb1 of Exopalaemon carinicauda was the highest (73.32%), followed by Homo sapiens (51.83%) and Mus musculus (51.31%). Phylogenetic tree analysis revealed that the amino acid sequence of Ptabcb1 was closely clustered with that of E. carinicauda (BP=100), which belonged to the monophyletic group of species clustering of the phylum Arthropoda (BP=97). The results of tissue distribution showed that Ptabcb1 was expressed in all examined tissues, with the highest expression in the hepatopancreas (7.49 folds compared with the heart tissue), followed by the intestine (5.89 folds) and the muscle (3.65 folds). Using fluorescence in situ hybridization, and fluorescence staining, Ptabcb1 was mainly expressed in the cytoplasm of the hepatopancreas. The effects of intramuscular injection of 20 mg·kg-1, 40 mg·kg-1 and 80 mg·kg-1 FLR on the transcriptional expression of Ptabcb1 in P. trituberculatus were studied by realtime fluorescence quantitative PCR. Moreover, P. trituberculatus were treated by the injection of 10 μM verapamil (VER) for 1 h, followed by the injection of 40 mg·kg-1 FLR. The effects of combined injection of VER and FLR on P. trituberculatus were explored by evaluating the transcriptional expression and transport activity of Ptabcb1 in P. trituberculatus. The results showed that FLR significantly promoted the transport activity of PtPgp protein at the transcriptional level by promoting the upregulation of Ptabcb1 in a concentration dependent manner within 24 h. It was also found that the combined injection of 40 mg·kg-1 FLR and VER significantly inhibited the efflux of FLR within 12 h, resulting in the decrease of PtPgp protein transport activity. After 12 h, PtPgp protein transport activity gradually returned to that of the control group. In addition, the transcriptional level of Ptabcb1 in P. trituberculatus was highly expressed in the hepatopancreas of P. trituberculatus. Hepatopancreas was the most important organ for detoxification and metabolism in P. trituberculatus. The high expression of Ptabcb1 in hepatopancreas further suggested that PtPgp could be used as the first line of defense against foreign pollutants, and could directly transport substrates or their metabolic end products out of cells. P. trituberculatus was also found to contain a conservative Pgp protein mediated defense system as the first line of defense against exogenous pollutants, which could directly transport substrates or their metabolic end products out of the cell. Our findings provide a basis for further understanding the molecular defense mechanism of Pgp protein mediated detoxification of crustaceans. Keywords: Portunus trituberculatus; Pglycoprotein; florfenicol; transport activity Related Articles | Metrics

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Analysis on karyotype of Platax teira 2022, 44(5): 535.  Abstract ( 120 )   PDF (1005KB) ( 441 )   Analysis on karyotype of Platax teira GAO Jie1,2, GUO Huayang1,4, LIU Mingjian1, ZHU Kecheng1,4, LIU Baosuo1,4, ZHANG Nan1,4, GUO Liang1,4, LIU Bo1,4, ZHANG Dianchang1,3,4 (1. Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization， Ministry of Agriculture and  Rural Affairs，South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences,  Guangzhou 510300, China; 2. College of Oceanography, Hebei Agricultural University, Qinhuangdao Hebei066003，China;  3. Sanya Tropical Fisheries Research Institute, Sanya Hainan572019, China; 4. Guangdong Provincial Engineer  Technology Research Center of Marine Biological Seed Industry, Guangzhou510300, China) Abstract: As the primary carrier of biological and genetic material information, chromosomes are the archives of natural evolution. The conclusions obtained by karyotype analysis research methods are essential reference materials in fish genetic breeding. The karyotype of chromosome is a significant basis and key for cytogenetic studies. The number and morphology of chromosomes are speciesspecific. Chromosome karyotype can reflect the overall and structural characteristics at the chromosomal level as a crucial theoretical basis and a critical experimental standard in genetic research. Chromosome karyotype analysis has essential reference value and practical significance for understanding the evolutionary history of organisms and exploring the relationship between species. The longfin batfish (Platax teira) is a marine fish that lives nearshore in tropical and temperate regions. It is native to the IndoEastern Pacific, from the Red Sea and East Africa to Papua New Guinea, north to the Ryukyus, and south to Australia, New Zealand, and Melanesia. Juveniles inhabit shallow inner reefs and mangrove areas, while adults inhabit lagoons and coral reefs at 70 m, feeding on algae, zooplankton and benthic invertebrates. P. teira is ornamental, and the adult fish has high nutritional and economic value. As the market demand for adult P.teira increases, the supply of fry does not meet the demand, so there is an urgent need to research the artificial breeding technology of P.teira. The problems of artificial breeding are strengthening the nutrition of parents, cultivating highquality fertilized eggs, improving the hatching rate, increasing the survival rate of the young, and controlling the phenomenon of mutual mutilation of the young. In this study, samples were pretreated with phytohaemagg lutinin (PHA, 0.75% NaCl prepare the concentration of 2.5 mg·mL-1), colchicine (0.75% NaCl prepare the concentration of 125 mg·mL-1) injection, different tissue soaking methods, and 110 metaphase cell karyotype of 8 juvenile fishes were analyzed by Giemsa staining using the cold drop method. The position of the mitotic sites was confirmed, and the relative lengths and arm ratios of each chromosome were measured and calculated, and they were paired. The chromosomes were divided into four groups according to the arm ratios: 1) metacentric chromosomes (m), with arm ratios ranging from 1.0 to 1.70; 2) submetacentric chromosomes (sm), with arm ratios ranging from 1.71 to 3.00; 3) subtelocentric chromosomes (st), with arm ratios ranging from 3.01 to 7.00; 4) telocentric chromosomes (t), with arm ratios ≥7.00. Results showed that there were 48 chromosomes in 95 division items (86.36%), all of which were telocentric chromosomes, and the relative length of chromosomes ranged from (1.90±0.123) to (4.67±0.220). 11 mitotic terms (10%) had less than 48 chromosomes, and 4 mitotic terms (3.64%) had more than 48 chromosomes. Among them, 15 were from group 2 gill and fin tissues, accounting for 13.6%, of which 12 were from gill tissues, accounting for 10.9%; 3 were from fin tissues, accounting for 2.7%. This indicated that the direct injection method of P. teira chromosome preparation was superior to the tissue immersion method under the present experimental conditions. In a given taxonomic order, the fish belonged to the primitive type when the telomeric chromosomes occupied most of the chromosomes, while the fish was said to be the specialized type when it had more central or sub-central chromosomes; and the taxa with fewer chromosome arms were more likely to be primitive than the taxa with more chromosome arms. In this study, we found that all 24 pairs of chromosomes of P.teira were telomeric (ttype), their chromosome numbers were excessively convergent, and the number of chromosome arms was 48, so P.teira belonged to a highly evolved taxon based on the above classification. The chromosome types of fish were speciesspecific, and the evolution level of species was mainly consistent with their chromosome types. Through comparative analysis of experimental data, it was concluded that the evolution of P.teira was consistent with the typical karyotype of high fish, and the polyploid phenomenon was not found in the chromosome of P.teira, nor was the appearance of heteromorphic sex chromosome and satellite. However, caution should be exercised when comparing the number of mitotic chromosomes between or within species studied, as the determination of confidence intervals might depend on the degree of chromosome shrinkage. Successful chromosome production presupposed access to tissues with rapid cell division and high metabolic activity, and the cephalic kidney, as an essential hematopoietic and immune organ of scleractinians, was preferred for production because of its rapid cell division rate. The present experiment showed that filming could also be accomplished by soaking the fin and gill tissues, but the results of filming differed between fin and gill tissues, with gill tissues being slightly better than fin tissues, probably because the fins of P.teira were too large and the cell division was slower, which affected the results of the experiment. A chromosome is all biological heredity, variation and the material basis for the development and evolution, The chromosome karyotype is significant not only for understanding the laws of biological, genetic composition and genetic variation and development mechanism but also for predicting and identifying the result of interspecific hybridization and polyploidy breeding, genetic mechanism, understanding gender. It is also of great reference value to determine the number of genomes of organisms and study the origin of species and their relationship with each other, their evolutionary status, classification, and race relations. Therefore, this study provides essential information and experimental enrichment for the cytogenetic study of P.teira, and reference data and practical integration for germplasm identification of P.teira through a large number of experimental data analyses, also provides a theoretical basis for future research on P.teira. Keywords: Platax teira; chromosome; karyotype Related Articles | Metrics

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Age identification for Larimichthys polyactis based on different sections of sagittal otolith and comparison with result of age backward inferring from growth equation #br# 2022, 44(5): 543.  Abstract ( 125 )   PDF (1471KB) ( 470 )   Age identification for Larimichthys polyactis based on different  sections of sagittal otolith and comparison  with result of age backward inferring from growth equation  KANG Zhongjie1,2, SONG Dade1, 2, LI Gang1, YAN Liping3, ZHONG Xiaming2,  TANG Jianhua2, WANG Yanping2, WU Lei2, XIONG Ying2 (1. College of Marine Sciences, Shanghai Ocean University, Shanghai201306, China;  2. Jiangsu Marine Fisheries Research Institute, Nantong Jiangsu226007, China; 3. Key  and Open Laboratory of Marine and Estuarine Fisheries Resources and Ecology, East China  Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China) Abstract: Fish age is a basic parameter in the study of fish population dynamics. Overestimation or underestimation of fish age undoubtedly can lead to overexploitation or waste of the resources. The clarity of the annual ring of otolith section affects the identification of fish age. At present, the accuracy of age inferred from the fish growth equation by fish growth parameters has not been verified. In this paper, small yellow croaker (Larimichthys polyactis), a model species for fishery resources research in marine economic fish, was taken as the research object. To explore the accuracy of age identification by sagittal otolith and age backward inferring by the growth equations for L. polyactis, we collected 45 individuals in the southern Yellow Sea to analyze three otolith sections, including sagittal section, frontal section and transverse section of sagittal otolith. 15 individuals were caught in Apr. 2018 with stow net of double stakes in Lvsi fishing ground and 30 individuals caught in Sep. 2019 with stow net in Dasha fishing ground. Three sections of L. polyactis sagittal otolith were analyzed to compare the effect on age identification as the experimental materials. Simultaneously, the Von Bertalanffy growth equations of L. polyactis during recent 30 years in China were summarized for age backward inferring based on body length of 45 L. polyactis. Taking the clear annual ring pattern and intuitive ring as the highest standard, the results showed that the annual ring clarity was the lowest in sagittal section (53.33%), higher in frontal section (66.67%) and the highest in transverse section (73.33%), respectively. The annual ring of three sections became more distinct after acid etching. L. polyactis sagittal section had the advantage in reflecting the whole life history based on the otolith microchemistry over the frontal section and transverse section because of its large surface area. However, the surrounding area of sagittal section core had many interferential rings, which resulted in misjudging the daily age of larva and juvenile of L. polyactis. Without the pretreatment by etching with 5% EDTA, the frontal section had clearer plane to identify the age more easily than the sagittal section. And the microstructure of frontal section could be used to study daily age identification and growth pattern. The transverse section had a smaller surface area than the aforementioned two sections and less affected by the secondary nuclei of L. polyactis, which was helpful in showing the clear annual ring even in thinner plane. The transverse section was more efficient for age identification of L. polyactis. Comparing the age identification results of three otolith sections with the age backward results of 19 growth equations, the Von Bertalanffy growth equation Lt=366［1-e-0.117 77(t+1.764 29)］ showed the highest similarity levels with 53.33 % for sagittal section, 86.67 % for frontal section and 86.67 % for transverse section, respectively. In sagittal section, the results showed that the two growth equations Lt=366［1-e0.117 77 (t+1.764 29)］ and Lt=230［1-e-0.26 (t+0.367 8)］ had the similarity levels of 53.33% and 66.67%, respectively. In frontal section, the results showed that the growth equations Lt=206.827［1-e-0.454 13 (t+0.353 4)］ and Lt=366［1-e-0.117 77 (t+1.764 29)］ had the higher accuracy of 66.67% and 86.67%, respectively, whereas the other growth equations had less accuracy than 50%. In transverse section, the results showed that the growth equations Lt=206.827［1-e-0.454 13 (t+0.353 4)］ and Lt=366［1-e-0.117 77 (t+1.764 29)］ had 80% and 86.7% accuracy, respectively. To sum up, the growth equation Lt=366［1-e-0.117 77 (t+1.764 29)］ was verified to have the absolute advantage in age identification matched with the results of annual daily of three otolith sections. Three possible reasons accounted for the results of the highest similarity for the growth equation Lt=366［1-e-0.117 77 (t+1.764 29)］. First, the experiment samples of the growth equation were from the Yellow Sea and the East China Sea and the range of research area basically covered the sampling area of this study. Second, the growth equation was fitted by onevariable linear regression method, and the prediction accuracy was higher than that by FordWalford growth transformation method. Third, the growth parameters in the growth equation involved the fish age from the otolith besides the fish body length and weight in experiment, which was one of important reasons for the high accuracy.  Age identification played a key role in fishery resource assessment, fishery management and the rational exploitation of resources. Age identification materials and methods were particularly important for fish age research. This paper revealed that the transverse section of otolith was the preferred methods followed by the frontal section for age identification of L. polyactis. And Lt=366［1-e-0.117 77(t+1.764 29)］ for age backward inferring was the optimal growth equation for L. polyactis population in the Yellow Sea. As a research method for fish age identification and growth research, age backward inferring from growth equation can quickly and accurately reflect the dynamic changes of biological resources and population structure. It is suggested that we should not choose arbitrarily the growth equation to estimate fish age on the basis of growth parameters with fish body length and body weight, but prefer the grow equation with the high similarity verified by age identification under the consideration of the sampling time and area for the fish. The reliability of age identification is crucial to study the population structure and growth characteristics of fish. Although the current trends of miniaturization and younger age of L. polyactis stock have been relieved in China, the simplification of population structure is still serious. This study provides a scientific option for strengthening the basic research of fish age and population dynamics. Keywords: Larimichthys polyactis; otolith; sectional features; age identification; age backward inferring Related Articles | Metrics

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Simulation analyses of abundance estimation of Portunus trituberculatus based on set gillnet for different sampling designs 2022, 44(5): 555.  Abstract ( 98 )   PDF (3833KB) ( 448 )   Simulation analyses of abundance estimation of Portunus trituberculatus  based on set gillnet for different sampling designs WANG Yingbin, LIU Ya, ZHAO Jing (School of Fisheries, Zhejiang Ocean University, Zhoushan Zhejiang316022, China) Abstract: The set gillnet has the characteristics of low cost, high selectivity, being easy to use, clean and environment friendly. It is one of the important fishing gears for fishing Portunus trituberculatus in the East China Sea. It is also the main operation method in the pilot waters of Zhejiang Province’s quota fishing management system. In addition, set gillnet is also used for fishery resource monitoring and estimation of fishery resources. Based on the catch of set gillnet, scientific and reasonable assessment of P. trituberculatus resources can not only reduce the cost of assessment, but also be a useful supplement to the investigation of conventional bottom trawl resources. In order to investigate the effects of different sampling designs of set gillnet on resource estimation of Portunus trituberculatus，an algorithm model is created to estimate the capture probability by different current speeds, moving speed of crab and net length. Based on this algorithm, four sampling survey methods including fixed station sampling, simple random sampling, stratified fixed station sampling and stratified random sampling are simulated. Considering the number of sampling stations of 16 and 25, four seasons, 50, 80 and 150 columns of set gillnet, a total of 72 sets of simulation experiments are performed. The python programming language is used to repeat simulation calculations for each set of experiments 1000 times. The results are as following: 1) In terms of sampling method, fixed station sampling with the increase of the number of set gillnet, the REE and RB values gradually decrease. In the random sampling scheme, the REE and RB values change in a smaller range. When the number of gillnets and the number of sampling stations are the same, the effect of stratified sampling is better than that of nonstratified sampling, and stratified random sampling has the best effect in this resource evaluation simulation experiment; lower resource density and higher ocean current speed make the REE value relatively small, and result in better results. In the case of a certain survey site, stratified sampling is superior to the fixed station and simple random sampling, and the result of resource estimation is more accurate. 2) In terms of the number of sampling stations, for the fixed station sampling and stratified fixed station sampling methods, the results of 25 sampling sites are better than those of the number of 16 sampling sites, showing a trend that the more the number of sites, the more accurate the fishery resource survey results. For the random sampling and stratified random sampling methods, the error values of the scenario of 25 sampling stations are smaller than those of the number of 16 sampling stations, but the error range is not greatly different. It shows that the survey results of random sampling methods tend to be stable, and the influence of the number of sampling stations is not obvious. 3) In terms of the number of set gillnet, besides the scenarios of the spring fixed station sampling, whose REE and RB values decrease with the increase of the number of set gillnet, other sampling scenarios all appear with the trends that the RB value changes from positive to negative with the number increasing, and there is a certain deviation in the estimation results. Therefore, when assessing fishery resources based on set gillnet, larger number of nets may not have better results. It must be comprehensively considered based on the structure and size of the actual sampled species, seasonal temporal and spatial distribution characteristics, as well as the environmental characteristics of sampling sea area. 4) In terms of seasonal characteristics, P. trituberculatus has the characteristics of seasonal temporal and spatial distribution, and seasonal factors have a certain impact on the accuracy of the survey of P. trituberculatus resources. In seasons with high resource density, a stratified sampling design is suitable. The resource density of P. trituberculatus in autumn is high and unevenly distributed, and the ocean current is the slowest among four seasons. Therefore, the error in the estimation results of resources in autumn is also the largest. The resource density of P. trituberculatus in winter is low, and the error in the estimation results of winter resources is smaller than those in other seasons. The estimation results are the closest to the “true value” among all sampling plans. The use of set gillnet for fishery resource surveys can reduce the damage of fishing gears to the ocean bottom, and plays a positive role in maintaining the marine ecosystem and promoting the sustainable development of fishery resources. However, as a passive fishing gear, set gillnet has strong selectivity, and has certain requirements for the selection of sampling methods and the number of sampling stations. It may overestimate or underestimate the abundance of resources. Therefore, it is necessary to comprehensively consider the impact of other possible factors in application.  Keywords: crab; northern East China Sea; station quantity; stock assessment Related Articles | Metrics

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Effects and curve fitting of morphometric traits on body weight at different larval growth stages in Octopus sinensis 2022, 44(5): 568.  Abstract ( 118 )   PDF (735KB) ( 435 )   Effects and curve fitting of morphometric traits on body weight  at different larval growth stages in Octopus sinensis SUN Yikang1,2， LI Meishuai1,2， CHEN Siqing2， ZHANG Yan2，  CHANG Qing2， LI Fenghui2， GE Jianlong2， BIAN Li2 （1.College of Fisheries and Life Science, Shanghai Ocean University, Shanghai201306, China；  2. Laboratory for Marine Fisheries Science and Food Production Processes, Pilot National Laboratory for  Marine Science and Technology (Qingdao),Yellow Sea Fisheries Research Institute,  Chinese Academy of Fishery Sciences,  Qingdao Shandong266071, China） Abstract: As a statistical method to study causality, path analysis has been widely used in the breeding of fish, shrimp, crab, shellfish and other aquatic animals. In order to explore the correlation between body weight and morphological traits of Octopus sinensis at different ages, this experiment took 60,100,140 days old O. sinensis as the research object, and measured their weight (W),total length (TL), arm length (AL), mantle length (ML), mantle width (MW), eyes distance (ED) and other morphological traits. The correlation analysis and path analysis were carried out. The path coefficient and the coefficient of determination between morphological traits and body weight was calculated. In order to establish the optimal regression equation of morphological traits to body weight, the correlation degree of various morphological traits to body weight were determined. In the study of morphological statistics, coefficients of variation of weight at 60, 100, 140 days old were the largest among all traits, which were 11.06%, 7.59%, 8.53%, respectively. The largest coefficient of variation among the morphological characters of O. sinensis at 60 days and 100 days was TL, and the largest coefficient of variation among morphological characters at 140 days was AL. Similar results were also found in other aquatic animal studies. The main characteristics affecting the body weight of Hexagrammos otakii at 6 months of age were head length, full length, body height and body width, while those affecting the body weight of Hexagrammos otakii at 12 months of age were full length, body height, body width and tail stalk height. The main traits affecting body mass of 11monthold Verasper variegatus were full length and body height, full length, head length and body height at 14 months, and full length and body height at 17 months. This indicated that the main morphological traits affecting body weight might change at different growth stages, so attention should be paid to adjust the judgment criteria according to different growth stages in the actual seedling raising process.The correlation coefficients results showed that the correlation coefficients of morphological traits of O. sinensis with different ages reached a very significant level (P<0.01), and the main morphological indicators affecting the weight of O. sinensis were different at different ages. The 60dayold was ML, MW, and ED. Among them, ML had the most significant direct effect, and ED had the least direct effect. The 100dayold were AL, ML, and MW, of which ML had the most significant direct effect, and AL had the least direct effect. 140 days of age were TL and MW, of which TL had the most significant direct effect, and MW had the least direct effect. The total determination coefficients of morphological traits of O. sinensis at 60 days, 100 days and 140 days on body weight were 0.853, 0.972 and 0.941. The synergistic effect of ML and MW at 60 and 100 days was the largest in determining the weight by joint effect, which were 0.322 and 0.317, respectively. The synergistic effect of TL and MW at 140 days was the largest, which was 0.445.In related studies, it was found that shell width was the decisive trait affecting the body weight of Chlamys farreri in Dalian sea, shell height in Qingdao sea, and shell length in Rongcheng sea.The dominant traits affecting body weight and meat weight of Marsupenaeus japonicus were fulllength, while the dominant traits affecting body weight and meat weight of Marsupenaeus japonicus were fulllength and head and thorax length, respectively.The morphological characteristics of male and female Takifugu fasciatus aged 23 months were different. Compared with female Takifugu fasciatus, male individuals had a narrower caudal stalk ratio and shorter body size.In Cynoglossus semilaevis, there were differences in morphological traits between different genders in the early development of the tongue sole.Therefore, for the same species, in addition to different growth stages, morphological traits of different populations under different growth environments would also have different effects on body weight. In the same population, the morphological characters of male and female individuals would also be quite different. Therefore, whether there were differences in the relationship between morphological traits and body weight in different populations and different sexes of Octopus sinensis needed further study.In the optimal regression equation analysis, the multiple regression equations of morphological traits at 60 days, 100 days and 140 days on body weight (Y) were: Y=-0.039+0.006XML+0.009XMW+0.003XED, Y=-0.796+0.013XAL+0.051XML+0.048XMW, Y=-2.878+0.044XTL+0.120XMW. In linear regression analysis, the correlation coefficient indicated the reliability of the prediction using the regression equation. Only when the coefficient of determination alone and the sum of the coefficient of determination of the two characters were greater than or equal to 0.85, it indicated that the main independent variables affecting the dependent variable were determined. In this study, the sum of the coefficient of determination of the morphological characters on body weight of Octopus sinensis at 60, 100, 140 days of age were 0.957, 0.972 and 0.941, respectively, which were all greater than 0.85, indicating that the key morphological characters affecting body weight had been found, while other morphological characters had little effect on body weight.The sum of determination coefficients of morphological traits for three different ages of O. sinensis on body weight were greater than 0.85, indicating that the morphological traits obtained in this study were the key traits affecting the body weight of O. sinensis, which could provide theoretical basis and measurement indicators for the selection and breeding of O. sinensis. Keywords: Octopus sinensis; morphological traits; correlation analysis; path analysis; multiple regression equation Related Articles | Metrics

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On large-scale culturing Ctenopharyngodon idellus cells on a microcarrier to proliferate grass carp reovirus genotype Ⅱ  2022, 44(5): 577.  Abstract ( 93 )   PDF (1838KB) ( 434 )   On large-scale culturing Ctenopharyngodon idellus cells on  a microcarrier to proliferate grass carp reovirus genotype Ⅱ  YANG Yuru1,2， WANG Yingying2， WANG Qing2, ZHOU Wenli1， YIN Jiyuan2， SHI Cunbin2 (1. College of Fisheries, Tianjin Agricultural University, Tianjin300384，China; 2. Key Laboratory  of Fishery Drug Development of Ministry of Agriculture and Rural Affairs, Key Laboratory of Aquatic  Animal Immune Technology of Guangdong Province, Pearl River Fisheries Research Institute,  Chinese Academy of Fishery Sciences, Guangzhou510380， China) Abstract: Grass carp (Ctenopharyngodon idella) is one of the most important cultured fish species in China, it is appreciated by the majority of breeders and consumers for its fast growth rate, diverse feed sources and delicious meat. Grass carp hemorrhagic disease caused by grass carp reovirus genotype Ⅱ (GCRV Ⅱ) has seriously hindered the development of the grass carp farming industry with a long onset season, wide epidemic scope, rapid transmission and high mortality rate. Vaccination is the most effective method for the control of viral diseases. However, viral vaccine production requires a largescale culture of the host cells. In the current race for virus vaccine production, microcarrier and suspension culture systems are amongst the most promising techniques available. As the microcarrier bead has a large surface area for cell attachment, it can produce a larger number of cells than the conventional monolayer culture. The current challenge in GCRV Ⅱonly induces a few fish cells proliferating and does not produce cytopathic effects (CPE), making it difficult to obtain high titers of the virus. Grass carp swim bladder cells (CiSB) are sensitive to GCRV Ⅱ and can be used in the proliferation of GCRV Ⅱ. To optimize the largescale cell culture of grass carp swim bladder cells (CiSB) for improving the antigenic content of GCRV Ⅱ, the Cytodex 1 microcarrier suspension culture system was chosen to cultivate CiSB cells and propagate GCRV Ⅱ. At the same time, the related indicators of proliferation dynamics were determined. The initial distribution of attached cells was recognized as the most critical stage for evaluating attachment efficiency. Suitable intermittent stirring could improve the contact time and also the attachment rate. During the apposition period, a speed of 30 r·min-1 and stirring for 2 min every 30 min were the best parameters for CiSB cell growth, and the cell apposition rate could reach more than 96% after 3 h. Next, in the cell proliferation stage, the conditions such as the initial inoculation density, stirring speed, microcarrier concentration and loading way of CiSB cells were explored and optimized. Results showed that when the cell density was 2×105 cells·mL-1, the cells showed good linear growth, and the highest harvest concentration was reached after 5 days. The cells proliferated quickly and the medium consumption was low when the microcarrier dosage of 2 g·L-1 was used, which provided the coverage rate of cells on the microcarrier of more than 95% and the ratio was about 20 cells per microcarrier. When the concentration of microcarrier increased to 3 g·L-1 or 5 g·L-1 , the cell density increased but more cell metabolites were also produced, leading to faster consumption of medium and harmful growth environment. In addition, a large number of damaged cells appeared later due to the shear force generated by the increased probability of collision between microcarriers. When the stirring speed was set at 30 r·min-1, the cell could obtain a stable flow culture environment, the proliferation rate was fast, and the attachment rate in the later stage of culture was good. When the agitation rate increased, the initial cell rate increased, but the increase of shear force resulted in a large number of cell damage. Adding 5% FBS to the medium and replacing the medium in half on the third day of culture could achieve the maximum yield of cells while maintaining the monolayer growth state of cells, and reduce the production cost while adding nutrients and diluting harmful metabolites. Under the optimal culture conditions, CiSB cells displayed a typical fibroblast morphology with good growth and uniform distribution, and could fully cover the microcarriers after 5 days. The cells could be dissociated from the microcarriers by treatment of preheated 0.5% trypsin containing 0.02% EDTA for 3 min in a 125 mL stirring bottle. The released and welldispersed cells were then used for scaleup culture in a 1 L bioreactor. High cell density (1.71×106 cells·mL-1) could be reached in the bioreactor with the efficient use of microcarriers, which confirmed the data obtained from the 125 mL stirring bottle. Moreover, CiSB cells were cultured under optimized parameters and infected with GCRV Ⅱ. The proliferation dynamics of GCRV were observed by measuring the copy number: the virus infection entered the logarithmic growth phase on the second day and reached a peak value (6.2×105 copy·μL-1) on the 5th day, which was 3 times higher than that in the adherent cell flask, indicating that this process was suitable for amplification of GCRV Ⅱ. Herein, a suspension culture system of grass carp swim bladder cells （CiSB） was developed using Cytodex 1 as microcarrier in a stirred bioreactor. This can could serve as a reference for future studies on the development of largescale production of vaccines against grass carp hemorrhagic disease. Keywords: grass carp swim bladder cells (CiSB); genotype Ⅱ grass carp reovirus; microcarrier culture; technology optimization Related Articles | Metrics

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Ecological characteristics and influencing factors of phytoplankton community in spring and summer in the East China Sea 2022, 44(5): 589.  Abstract ( 96 )   PDF (2594KB) ( 493 )   Ecological characteristics and influencing factors of phytoplankton  community in spring and summer in the East China Sea LUO Minbo1,2, JIAN Tingting1,2， WANG Yunlong1， ZHANG Heng1，  YIN Yan’e1， ZHANG Haiyan1， YANG Jieqing1  (1. East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China;  2. College of Marines Sciences, Shanghai Ocean University, Shanghai201306, China ) Abstract: In order to understand the ecological characteristics of phytoplankton community in the East China Sea in recent years, the structural characteristics of phytoplankton community in the East China Sea and its relationship with typical environmental factors (water temperature, nutrient content and structure, CODMn and suspended solids concentration) were analyzed by investigating the basic elements of phytoplankton and environment in the East China Sea in May and August from 2015 to 2017. Results showed that the nitrogen phosphorus ratio in the study area of the East China Sea in spring was 2035. The dominant species of phytoplankton in spring were mainly composed of Coccinodiscus oculusiridis, Coccinodiscus jonesianus and Skeletonema costatum. The ratio of nitrogen to phosphorus in summer was higher than that in spring and was much higher than 16∶1. The dominant species in summer was Skeletonema costatum. According to the investigation, the number of phytoplankton in the coastal waters was significantly higher than that in the continental shelf of the East China Sea. The redundancy analysis results showed that from spring of 2015 to 2017, the environmental factor that had a great impact on phytoplankton in the investigated sea area was active phosphate. From summer of 2015 to 2017, the environmental factors that had a great impact on phytoplankton in the investigated sea area were inorganic nitrogen, active phosphate and chemical oxygen demand. In S3 and S5 of the fishing ground in the Yangtze River Estuary, the transparency of the water body was high, and the content of inorganic nitrogen and active phosphate in the water body was relatively high, which provided a good nutritional condition for the largescale propagation of phytoplankton. This phenomenon may be related to the thin layer distribution of phytoplankton in the Yangtze Estuary. According to the data from 2015 to 2017, the average abundance of phytoplankton in spring and summer was 3.0 × 104 cell · L-1 and 2.7× 104 cell · L-1. Based on the data collected from the continental shelf survey network of the East China Sea from 1997 to 2000, the phytoplankton abundance in autumn was the highest (211.9 × 104 cell · m-3）, followed by summer (50.4 × 104 cell · m-3） and winter (11.4 × 104 cell · m-3）and the lowest was in spring (2.0 × 104 cell · m-3）. From 1997 to 2000, the average phytoplankton abundance of four seasons was 68.9 × 104 cell · m-3. The coastal area of the East China Sea had a high abundance of phytoplankton due to the impact of the fresh water of the Yangtze Estuary, the Qiantang River and the coastal current of the East China Sea.  The results of redundancy analysis (RDA) using Canoco software showed that in spring of 2015, the environmental factors that had a great impact on the distribution of phytoplankton in the study area were pH, DO and active phosphate. DO, pH and active phosphate environmental variables were positively correlated with RDA1. In summer, the environmental factors that had great influences on the distribution of phytoplankton in the study area were COD and active phosphate. Environmental variables such as COD, active phosphate, DO, inorganic nitrogen and pH were positively correlated with RDA1. In spring of 2016, the environmental factors that had great impacts on phytoplankton were water temperature, DO, inorganic nitrogen and COD. Environmental variables such as water temperature, DO, inorganic nitrogen and COD were positively correlated with RDA1. In summer, water temperature and inorganic nitrogen were the environmental factors that had great negative impacts on Skeletonema costatum. Environmental variables such as water temperature and inorganic nitrogen were negatively correlated with RDA1. In spring of 2017, the environmental factor that had a great negative impact on the dominant species of phytoplankton was active phosphate. The active phosphate environment variable was negatively correlated with RDA1. In summer, inorganic nitrogen was the most important environmental factor affecting Skeletonema costatum. Inorganic nitrogen environmental variables were positively correlated with RDA1. Keywords: East China Sea; phytoplankton community; ecological characteristics; environmental factors; spring and summer Related Articles | Metrics

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Path planning of Antarctic krill targeted fishing net based on analytic hierarchy process#br# 2022, 44(5): 598.  Abstract ( 69 )   PDF (2305KB) ( 449 )   Path planning of Antarctic krill targeted fishing net  based on analytic hierarchy process YAO Yuqing1,2, DAI Yang2, WANG Lumin2， WANG Shuxian2,3，  CHEN Shuai2， YANG Shenglong2， SHI Yongchuang2 (1. College of Information, Shanghai Ocean University, Shanghai 201306, China;2. Key Laboratory  of Fisheries Remote Sensing,Ministry of Agriculture and Rural Affairs, East China Sea Fisheries  Research Institute, Chinese Academy of Fishery Sciences, Shanghai 200090, China; 3.School of  Navigation and Naval Architecture, Dalian Ocean University,Dalian Liaoning116023, China ) Abstract: The exploitation and utilization of Antarctic krill originated in the 1970s. The former Soviet Union adopted the traditional trawl technology for the first trial fishing, followed by Japan, Norway, Poland and other countries to carry out the commercial fishing of Antarctic krill. At present, the commercial fishing of Antarctic krill is all trawling, and the main two kinds of nets are net trawl and truss trawl. The truss trawl has less influence on the horizontal expansion of the net due to the fixed length of the truss, and the fishing efficiency is higher than that of the net trawl. There are single ship operation and mother ship multiship operation in the towing mode. In obtaining the catch, there are artificial collection of the catch through the net and the way of collecting the catch by pumping. In krill fishing in Japan and South Korea, electrohydraulic automatic control of net hoisting and setting has been realized. In the process of trawling, the balance of the trawl and the shape of the net can be adjusted by controlling the acoustic image of the fishing instrument. Norway is the country with the highest level of automation and fishing efficiency in Antarctic krill fishing at present. The SAGA Sea vessel built by Norway adopts underwater continuous pumping fishing technology for the characteristics of strong clustering and wide area. The main core equipment of the technology system is the shrimp suction pump, the supporting power pipeline of the pump and the krill transport hose. The shrimp suction pump is connected with the net capsule. In the process of trawling, the catch of krill in the net capsule is continuously transported to the fishing vessel by the suction pump through the transport hose. This method is called continuous fishing because it does not need to interrupt the fishing operation by picking up the catch of the net. Continuous fishing greatly reduces the number of times of raising and releasing nets, avoids the squeeze on catches, and ensures the quality of krill catches . It is one of the most advanced krill fishing methods at present. From the perspective of fishing efficiency and technological development trend, the continuous pumping technology with truss trawl is the mainstream of krill fishing technology development in the Antarctica. Antarctic krill is a very important strategic resource in China’s marine power strategy and Antarctic krill fishing is an important link in the ocean fishing system. But China still lags behind developed countries in the aspects of domestication of fishing equipment, intellectualization of fishing technology and processing equipment, and innovation and upgrading of equipment.The current fishing mode of krill depends on the image of the fishing instrument observed by the captain of the fishing boat and personal experience to determine the fishing depth. The method of artificial determination of krill water layer has a certain lag in the fishing process. If the krill aggregation layer changes, the depth of the krill aggregation abundance center can not be accurately determined in real time, and the fishing depth of the network port can be controlled by adjusting the length of the trawl to target the water layer with high krill aggregation abundance, which will seriously affect the fishing efficiency of Antarctic krill. Therefore, it is urgent to develop an efficient and intelligent moving path planning algorithm for Antarctic krill fishing stringers. When the Antarctic krill is discovered, the moving route of the truss can be planned timely and efficiently to maximize the economic benefit. In order to overcome the subjectivity of artificial planning and hysteresis, and improve the efficiency of China’s Antarctic krill fishing and automation level. This paper studied the existing route planning algorithm analysis and comparison of the characteristics and applicable scope of various path planning algorithm， comprehensively summarized the domestic and foreign research results about the optimal path planning. This paper also analyzed the technical problems of the moving path planning of krill fishing stringers in the Antarctica. Based on the sonar data collected by the underwater acoustic instrument EK80, this paper proposed a truss moving path planning algorithm for krill fishing operations in the Antarctica. In terms of the determination of fishing depth, the sliding window statistical algorithm was constructed to analyze the data of the fishing instrument, automatically calculate the depth of the largest point of krill cluster abundance, determine the best fishing depth, get rid of the existing method of relying on manual observation of the fishing instrument image, determine the fishing depth of krill, and improve the timeliness of data.The experimental data were collected by underwater acoustic instrument EK80 scientific echo sounder. The data survey time was from 18∶12∶14 on April 18th, 2016 to 18∶31∶53 on April 18th, 2016. The survey area was 63°16′ 46″ S63°18′ 31″ S, 58 °24′ 26″W58 °30′19″W. In addition to krill cluster signals, the echo image data collected also contained a large number of strong and weak interference signals that were higher than krill echo intensity and lower than or close to krill echo intensity. In this paper, the maximum and minimum values of backscattering intensity (Sv, dB) of krill population product collected without interference signal were used as the upper and lower thresholds for eliminating interference signal. The interference signal point after elimination was assigned a value of -999 dB. Echoview software (V8.0.92) was used to preliminarily analyze the water depth range of krill colony distribution from 15 m to 40 m, and the target intensity of krill population product backscattering intensity data was -70 dB and -80 dB, respectively. Firstly, the backscattering intensity data of krill population was analyzed by using sliding window statistical method. The sliding window statistical method needed to design a rectangular data window, and determine the specific position of krill local density center coordinates in the window through calculation. Rectangular fish finder data window was used to simulate artificial observation images, different artificial observation fish finder images were judged in terms of color depth of krill gathered water layer, there would be a certain subjective error and lag. It was more accurate and faster than manual method. In this method, the window sizes were set to 3, 4, 5, 6 and 7 respectively, and 5 groups of local density center coordinate sequences could be obtained. Secondly, in order to make the network port fishing route trajectory executable and reduce the difficulty of calculation, this paper designed a high realtime continuous planning algorithm using cubic Bspline curve as the path planner. Based on the path planning of cubic Bspline curve, the path cluster was constructed by using local density center coordinates. Thirdly, AHP was used to establish a path evaluation model to evaluate the advantages and disadvantages of the path. Taking economy and control ability as criteria, and taking capture rate, path length, curvature and number of inflection points as subcriteria layer, each index was quantified to construct the optimal path system and obtain the optimal path. Finally, the experimental results of real scenes showed that the capture rate of this algorithm was 94.33%, which was 9.8% higher than the traditional method. After many experiments, the average time of path planning was 2.5 s, which could meet the requirements of realtime krill net preplanning. Keywords: Antarctic krill; analytic hierarchy process; cubic Bspline curve; route planning Related Articles | Metrics

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Research on YOLOv5-based object detection method for shrimp industrial farming 2022, 44(5): 610.  Abstract ( 154 )   PDF (5047KB) ( 485 )   Research on YOLOv5-based object detection  method for shrimp industrial farming CHEN Ziwen1, LI Zhuolu2, YANG Zhipeng2, HE Jiaqi2, CAO Lijie2,3, CAI Kewei2,3, WANG Qihua4 (1. College of Mechanical and Power Engineering, Dalian Ocean University, Dalian Liaoning116023， China;  2. School of Information Engineering, Dalian Ocean University, Dalian Liaoning116023， China; 3. Key  Laboratory of Marine Information Technology of Liaoning Province, Dalian Liaoning116023， China; 4. School  of Medical Information Engineering Jining Medical University, Rizhao Shandong276800，China) Abstract: Shrimp industrial farming system development originated in the 1990s. The Texas Institute of Marine Science developed the runway shrimp farming system in the mainstream of foreign industrial farming systems. China’s industrial farming development is still in its infancy, the degree of automation is low, and there is an urgent need to develop relevant intelligent systems. Currently, shrimp industrial farming is still using manual feeding methods; the amount of bait feeding needs to be determined according to the density of shrimp in the pool. Traditionally, farmed shrimp counting is generally performed by manual random sampling, which is laborintensive, inefficient, and susceptible to shrimp growth and the purification load of the circulating water system.  The computer visionbased farmed shrimpcounting method has the advantages of no contact throughout the process and fast counting speed, which can effectively solve the problems of timeconsuming and laborintensive manual counting and specific damage to shrimp. At present, computer vision technology has been more widely used in aquaculture. With the rapid development of deep convolutional neural networks, target detection based on deep learning has surpassed the traditional methods and has become the mainstream method of target detection and has been widely used in different fields. The main frameworks of deep learningbased target detection algorithms are the RCNN (regionconvolutional neural networks) series, SSD (single shot multibox detector), and YOLO(you only look once) series. Scholars have introduced them to the field of agricultural engineering and achieved good results.  This paper proposes a target detection method for farmed shrimp based on YOLOv5 framework. YOLOv5 is a singlestage target detection algorithm that adds some new improvement ideas to YOLOv4, resulting in a significant performance improvement in speed and accuracy. The main improvement ideas are shown as follows. Input side: in the model training stage, some improvement ideas are proposed, mainly including mosaic data enhancement, adaptive anchor frame calculation, and adaptive image scaling. Benchmark network: incorporating some new ideas from other detection algorithms, mainly including focus structure and CSP structure. The target detection network often inserts some layers between backbone and final head output layer, and the FPN+PAN structure is added in Yolov5. The top output layer: the anchor frame mechanism of the output layer is the same as YOLOv4, and the main improvements are the loss function GIOU loss during training and DIOU_nms for prediction frame screening. The camera is a Hikvision DS2CD3T86FWDV215S camera with a focal length of 2.8 mm and an angle of 114.5 degrees. The captured images are in PNG format, with a height of 3 000 pixels and a width of 4 000 pixels, and are taken at 2minute intervals for 181 images. In this paper, the data set is manually labeled with “LabelImg” labeling tool, and the label information is stored in txt label files. Each label file corresponds to an image file one by one, in which each line stores one target information, and the information is the target category, X and Y axis coordinates of the center point of the detection frame, and target width and height in turn. In this paper, we design an adaptive image cropping preprocessing algorithm for the highresolution image training set, which expands the training data volume by adaptively cropping the training set, reduces the loss of detail features during training the original image, and improves the target detection accuracy. The model uses YOLOv5s pretraining weights under the YOLOv5 framework for migration learning. Among hardware platform parameters, the central processor is Intel i7 7700k, the graphics computing card is Nvidia GeForce GTX 1070 Ti, the number of batches is 16, and the training is 100 rounds with 28 507 iterations. In this paper, mean average precision (mAP), accuracy (precision), and recall (recall) are used as evaluation metrics for training model performance. For classification problem, the samples can be classified into four cases: true positive (TP), false positive (FP), true negative (TN), and false negative (FN), based on the combination of the actual category situation and the category situation predicted by the model. In order to prove the effectiveness of the proposed adaptive cropping algorithm, two sets of comparison experiments are designed: using the original images as the training set and the resulting model 2; and using only the images generated by the adaptive cropping algorithm as the training set and the resulting model 3. The experimental results show that the method proposed in this paper is effective. The experimental results show that the proposed method can achieve accurate recognition and counting of farmed shrimp in a small number of highresolution images, and the detection model obtained by preprocessing the image samples with the algorithm has higher detection accuracy than the original data set under the same computing hardware conditions, with 92.55% recognition accuracy, 98.78% recall rate, and 97.5% average accuracy. This paper proposes an adaptive image cropping algorithm for improving the problem of excessive compression rate of highresolution images and realizing the problem of losing feature information due to the direct input of images taken by highresolution cameras into the neural network in the farming plant in order to automate the statistics of shrimp quantity in the farming process to realize quantitative baiting. From data augmentation of the training images through comparison experiments, it is proved that the accuracy of the trained model processed by the adaptive cropping algorithm can be improved by 3.53%, and the mean accuracy (IoU =0.95) is 2.86% compared with the unprocessed model, which can more effectively improve the accuracy of the target detection algorithm in the shrimp industrial farming process and provide reliable data for the realization of accurate feeding. The algorithm in this paper only conducts some innovative experiments in the data preprocessing part to demonstrate the impact of the data preprocessing algorithm on the target detection algorithm. Is it feasible to migrate the algorithm from this paper to the network detection part? Moreover, how to effectively reduce the feature loss caused by the network structure in the process of highresolution detection and how to balance the relationship between the accuracy of chunking detection and detection time remains to be studied. Keywords: object detection; deep learning; Yolov5; image preprocessing Related Articles | Metrics

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Research on preventing marine biofouling organisms with PTFE film and potential mechanism#br# 2022, 44(5): 621.  Abstract ( 134 )   PDF (2571KB) ( 440 )   Research on preventing marine biofouling organisms  with PTFE film and potential mechanism LIU Jianping1, NI Daojun1, LI Wenwei2, XIANG Xin2, ZHU Yawei3,  WU Jianhua4, LIU Junfeng1, LI Yajing1, QI Zhitao5 (1. China Three Gorges Renewables (Group) Co. Ltd., Beijing101100, China; 2. China Three Gorges  Corporation, Beijing100038, China; 3. College of Textile and Clothing Engineering, Soochow University,  Suzhou Jiangsu215021, China; 4. Nanjing Haohui HighTech Co., Nanjing210006, China; 5. School  of Marine and Bioengineering, Yancheng Institute of Technology, Yancheng Jiangsu224051, China) Abstract: Offshore wind power is an important development direction of wind power generation. However, the monopile steel structures of offshore wind power are immersed and eroded by seawater for a long time and its surface is easily adsorbed, fixated and corroded by marine organisms, leading to thickening of the monopile steel structure diameter and internal corrosion of monopile steel, which can seriously shorten the service life of offshore wind power equipment. How to prevent the corrosion of seawater and marine organism on the offshore wind turbine pile is important for the development of wind power industry. The polytetrafluoroethylene (PTFE), known as “the king of plastic”, is a kind of tetrafluoroethylene monomer polymerization of polymer, which has been widely used in national defense, atomic energy, petroleum, radio, electricity, machinery, chemical industry, etc. In the present study, two kinds of PTFE with low surface energy were prepared by hot extrusion method, named as highdensity PTFE film (HDPTFE) and lowdensity PTFE film (LDPTFE). Results showed that the density of HDPTFE and LDPTFE was 2.3 g·cm-3 and 1.6 g·cm-3, respectively. The crystallinity of HDPTFE and surface energy of HDPTFE was 89.0% and 16.4 mN·m-1, and these of LDPTFE were 79.0% and 22.7 mN·m-1, respectively. The HDPTFE and LDPTFE were treated with nitrogen, and then physically laminated with R4088 tape (3M, USA) to produce PTFE composite films with selfadhesive properties (i.e. HDPTFE film and LDPTFE film). The peeling strength of R4088 tape with HDPTFE, polyester film and epoxy resin were more than 1 000 gf, which had strong bonding strength and could be firmly stuck on the surface of steel pipe pile. After 40 000 wear resistance tests, 14 400 h salt spray test and 1 000 h rain erosion test, the surface of HDPTFE film had no roughness or damage, neither change in the appearance or change in mechanical properties. After 15 h of high and low temperature aging resistance experiments, 5 000 h artificial climate aging resistance and ozone aging resistance experiments, the tensile strength retention rate of HDPTFE remained as 99.9% and the elongation retention rate was more than 99.0%, indicating that HDPTFE had excellent property of weather resistance. In addition, no small molecules were resolved from HDPTFE film, suggesting that HDPTFE had no adversely affects on the seawater environment. Then, HDPTFE and LDPTFE films were immersed in seawater for 3 years. We found that LDPTFE film were swelled and peeled off, while HDPTFE film maintained its original surface morphology structure, which was attributed to the high density, low surface energy and high crystallinity of HDPTFE. The reason for the better resistance of seawater corrosion of HDPTFE than that of LDPTFE might be: 1) The density and crystallinity of HDPTFE were higher than that of LDPTFE; 2) The high density and crystallinity of HDPTFE blocked the swelling that caused by the wetting and penetration of seawater. While, the seawater could penetrate slowly into the inside of LDPTFE that caused the crack between the layers of LDPTFE, which finally led to the rupture and fall off of LDPTFE. Further, HDPTFE film with selfadhesive property was selected to be wrapped on the surface of wind turbine steel pipe pile (monopile), and the results of marine organism adhesion and attachment on the surface of monopile with HDPTFE film (T5 monopile) or without film (T4 monopile) were compared after 9 months of actual operation at sea and subsea photography. We found that the attachment of marine microbial on the surface of T4 monopile was obvious, which mainly were Balanus, Mytilus edulis and calcareous curing hard layerhard layer. In contrast, there were small number of marine microorganisms on the wavefacing surface of T5 monopile and the surface of  HDPTFE remained smooth and flat. For marine microorganism there were 23 Balanus  on the surface of HDPTFE per m2, but no Mytilus edulis on it. The waveback surface of T5 monopile was more suitable for the growth of marine microbial and could also form hard layer that caused by death of fouling organisms. However, the marine organism and hard layer on the waveback surface of T5 monopile were easier to fall off, compared with that of T4 monopile. We concluded that: 1) With large impact of seawater on the wavefacing surface of HDPTFE film, the marine organism could only adhere and temporarily immobilize on the surface of HDPTFE, but no calcification layer was formed; 2) With small impact of seawater on the wave back surface of HDPTFE film, the marine organisms could adhere, immobilize, grow, reproduce, die and calcify on the surface of HDPTFE. However, due to the excellent corrosion resistance and low surface energy of HDPTFE, the adhesion between marine organisms and HDPTFE was weak, and the HDPTFE could not be corroded, directly resulting in the falling off of the calcification layer of marine organisms; 3) The falling of the calcification layer on the HDPTFE was random and the area of calcification layer on the HDPTFE deceased as time extended; 4) The marine organisms could normally adhere, grow, reproduce, die and calcify on the surface of monopile without HDPTFE and the calcification layer did not fall off and increased with time extended, finally leading to more and more marine organism accumulate on the surface of monopile. Thus, the mechanism of HDPTFE material against marine fouling organisms was proposed to be a repeated cycle of “adsorption, temporary fixation, shedding, secondary adsorption (reagglomeration)”, and there was no permanent fixation of marine fouling organisms. Although HDPTFE material did not inhibit the adsorption, growth and proliferation of adhesive marine organisms, the fouled marine organism calcification layer would be actively peeled off and shed due to the low surface energy and excellent corrosion resistance of HDPTFE, and the selfshedding of marine fouled organisms was more obvious under the impact of seawater. In conclusion, the HDPTFE has excellent weather resistance and can be used as a protective material against marine life fouling for offshore wind power steel pipe piles, which provides a new method for antimarine life adhesion and fouling of static and mobile platforms at sea, with extremely important theoretical and experimental guidance. Keywords: polytetrafluoroethylene (PTFE); membrane materials; marine biofouling organisms; bioadhesion Related Articles | Metrics

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A review of data-limited assessment methods and their applications in fishery resource conservation 2022, 44(5): 631.  Abstract ( 150 )   PDF (802KB) ( 476 )   A review of data-limited assessment methods and  their applications in fishery resource conservation WANG Yang1,2， GENG Zhe1,2， ZHU Jiangfeng1,2， DAI Xiaojie1,2 (1. College of Marine Sciences, Shanghai Ocean University, Shanghai201306, China; (2. Key Laboratory  of Sustainable Exploitation of Oceanic Fisheries Resources, Ministry of Education, Shanghai201306, China) Abstract: Scientific stock assessments are the key for fishery management. They support sustainable fisheries by providing fisheries managers with the information necessary to make sound decisions. However, due to the high cost of data collection, the majority of the world’s fisheries are datalimited which lack sufficient data to carry out full stock assessment. In the United States, 59% of stocks are datalimited; 165 out of 262 stocks in Europe have varying degrees of data deficiency; in China, most catches data are counted by the aquatic products categories which are not specific single species. Based on these situations, scientists have been seeking simple and lowcost methods to achieve stock assessment. Therefore, datalimited methods (DLMs) have developed rapidly in the last two decades. Many fisheries that are difficult to carry out traditional stock assessment are now able to be scientifically managed. The domestic researches about DLMs are still finite, and few of them has reviewed how the results of these models can be used to help managers to develop conservation strategies. Model structures of DLMs are generally simple, and their results are therefore different from those obtained by traditional stock assessment methods. Appropriate interpretation and rational use of the results from DLMs are crucial to the determination of management measures. In this study, we divide DLMs into three categories according to data requirements: catchbased models, lengthbased models, and multispecies models. And we briefly summarize and review the model data requirements, model output, and the advantages and disadvantages. Then, we mainly discuss the appropriate application of DLMs into fisheries resource conservation and highlight the issues that need to be focused on in practice. Catch data are the most common fishery data. Therefore, catchbased models are the most explored and developed models. Widely used models are depletioncorrected average catch (DCAC), depletionbased stock reduction analysis (DBSRA), an extension of catchMSY(CMSY), catch only modelsampling importance resampling model (COMSIR), statespace catch only model (SSCOM), simple stock synthesis (SSS). All of these models need catch data and some simple biological information. CMSY model can estimate the maximum sustainable yield (MSY), BMSY, and FMSY. COMSIR and SSCOM have higher ability on forecasting stock status. DCAC and DBSRA include biological parameters such as natural mortality, growth, and recruitment. The results are more reliable, but the models are sensitive to stock depletion. The main outputs of catchbased models are MSY and MSYbased reference points. Therefore, fishery management applies the outputcontrol management to set catch limits. Reference points include overfishing limit (OFL), acceptable biological catch (ABC), annual catch limit (ACL), and annual catch target (ACT). An OFL is an estimate of the catch level above which overfishing is occurring. The ABC is lower than OFL which accounts for scientific uncertainty. The ACL is normally smaller than ABC to ensure that the stock is not overfished. The ACT is a level of catch set to account for management uncertainty which is lower than the ABC. Generally, selecting ACL as the catch limit is relatively safe. Length frequency data have the advantage of being relatively cheap, straightforward, and quick to collect from landing sites and markets. Therefore, lengthbased models have developed rapidly in recent years. The lengthbased models include lengthbased spawning potential ratio (LBSPR), lengthbased integrated mixed effects(LIME), lengthbased risk analysis (LBRA), and lengthbased Bayesian approach (LBB). The LBSPR model is based on the assumption of stock equilibrium and assumes that the length frequency data is representative of the exploited population at a steady state. The LIME model is an extension of the LBSPR that accounts for timevarying recruitment and fishing mortality. The LBRA extends the lengthbased model to a risk analysis context which could define sustainability risks in terms of probability distributions. The LBB model can estimate the currently exploited biomass relative to unexploited biomass (B/B0). Therefore, based on the outputs of LBB, the limit and target reference points are usually set as the values of B/B0 equal to 0.2 and 0.4, respectively. Except for LBB, spawning potential ratio (SPR) is used as the biological reference point for other lengthbased models which is defined as the proportion of the unfished reproductive potential left at any given level of fishing pressure. The values of SPR equal to 30% and 40% are often used as limit and target reference points in practice, respectively. Fisheries resource conservation could also apply the inputcontrol management which constrains the fishing effort (e.g., location, gear type, mesh size). Many species are caught at the same time in some fisheries, which are called multispecies fisheries. In these fisheries, the singlespecies assessment method can not be used in management. There have two general approaches. To reduce research costs, one of the methods is to assign datalimited stocks to assemblages according to similar life history, trophic behavior, home range, etc. The stocks can be managed as units in this way. Ideally, each assemblage would include at least one datarich species as a status indicator for the management unit. Managers then can make conservation measures for the entire unit based on the status of the indicator species. The other category of methods is based on the ecosystem. Mainly models have multispecies virtual population analysis (MSVPA), multispecies statistical catch at age model (MSCAA), impact assessment model (IMA), and productivity and susceptibility analyses (PSA). The MSVPA model can quantify the predatorprey interactions and estimate the rates of predation mortality for exploited fish populations. The MSCAA includes the influence of climate change. The IMA is combined with economic dynamics. The PSA is a method for assessing the vulnerability of a fishery species which is based on the attributes of productivity and susceptibility. Ecosystembased models still require extensive biological data. Finally, in addition to strengthening data collection, we suggest two measures that can be used to improve the robustness and effectiveness of management objectives. The first one is to use the hierarchical Bayesian framework to integrate the collected available information as the information prior. Peerreviewed publications and publicly available databases (e.g., Fishbase) are common sources of information collection. Secondly, we recommend that management strategy evaluation (MSE) and harvest control rules (HCRs) can be added in future work. Keywords: datalimited; stock assessment; fishery resource conservation; sustainable yield; biological reference point Related Articles | Metrics

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Research progress of fish video tracking application based on computer vision 2022, 44(5): 640.  Abstract ( 220 )   PDF (825KB) ( 505 )   Research progress of fish video  tracking application based on computer vision PEI Kaiyang1,2, ZHANG Shengmao1, FAN Wei1, WANG Fei1, ZOU Guohua3, ZHENG Hanfeng1 (1. Key Laboratory of  Fisheries Remote Seasing, Ministry of Agriculture and Rural Affairs;  East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090,  China; 2. College of Information, Shanghai Ocean University, Shanghai201306, China;3. Shanghai  Junding Fishery Technology Co., Ltd., Shanghai200090, China) Abstract: Object tracking technology is an important research direction in the field of computer vision. The introduction of computer vision technology in the fields of marine environment detection and aquaculture monitoring can realize the tracking of fish video targets, which can save unnecessary manpower and material resources, in aquaculture, marine environment monitoring and other fields, it can reduce costs and improve efficiency. At present, there has been a lot of research in the field of underwater image vision, but there is a lack of general summary of the research status of video tracking technology for fish targets. Therefore, a comprehensive review of fish video tracking methods based on computer vision techniques is of great significance. Fish video tracking is mainly divided into four parts: underwater image acquisition, image sharpening, fish tracking and trajectory output. Among them, the image sharpening part and the fish target tracking part are the most critical links in the overall process. This article makes a comprehensive review of these two parts.Underwater images captured in natural conditions are affected by the refraction of light in water, and different wavelengths of light exhibit different degrees of exponential decay underwater, resulting in blurring, color cast, and reduced visibility in the captured underwater images. Underwater image sharpening technology can be used to solve these problems. The research directions in this field are mainly divided into image enhancement, image restoration and deep learning. The image enhancement technology realizes the sharpening of the image by adjusting the color of the underwater photographed image. There are mainly methods based on the histogram stretching method and the method based on the Retinex theory. The method based on histogram stretching has high operating efficiency, but the application range is narrow and noise is easily introduced; the method based on Retinex theory has better effect on image color correction and edge sharpening, but the operation is more complicated and the execution efficiency of the algorithm is relatively low. Image restoration technology achieves image clarity processing by establishing a degradation model of underwater images. This method has a significant effect in certain situations, but has poor applicability in complex scenes. The deep learning method realizes the clear processing of underwater images by learning the features between blurred underwater images and clear images. This method has strong applicability, and the effect of color restoration is remarkable, but the phenomenon of blurred details and unclear edges will occur.Underwater fish video tracking is mainly affected by the uncertainty of the motion state of fish target and the uncertainty of observation data. In the field of fish target tracking, according to different types of observation models, it is mainly divided into generative methods and discriminative methods. The generative method realizes the tracking task of the target by analyzing the target features in the first frame of the video image, generating a tracking template, and searching for the target closest to the template in the subsequent image frames. The generative method is relatively simple to implement and has high computational efficiency, but the tracking accuracy decreases when the shape of the fish target changes or is occluded by obstacles. The discriminative method transforms the target tracking problem into a classification problem, and uses the classifier to distinguish the fish target and the background, so as to further realize the tracking of fish target. The main research directions of discriminative methods are divided into correlationbased filtering methods and deep learning methods. The basic idea of the target tracking method based on correlation filtering is to use a preset filtering template to perform convolution operation on the template in the next frame of image and calculate the response value. The area with the largest response value is where the fish target is located. In recent years, deep learning methods have outstanding performance in the field of object classification and are suitable as classifiers in discriminative tracking methods. In contrast, the correlationbased filtering method has the effect of antideformation and antiocclusion, and has high operating efficiency, but requires a preset filtering template and has poor applicability; the deep learning method has relatively high accuracy for target detection and tracking, but a large amount of image and video data is required for model training, and the efficiency of model training is low.To summarize the full text, the development of computer vision technology provides a new observational approach for underwater fish behavior analysis and ecosystem monitoring. Through underwater monitoring, images of fish behavior can be obtained in real time, which can intuitively reflect the survival status of fish and the richness of ecosystems. Using computer vision technology to process underwater surveillance video can efficiently and cheaply obtain fish and ecological environment information, and provide a reference for the management and assessment of marine fishery resources. However, computer vision technology still has certain deficiencies and limitations in underwater fish video tracking scenarios. For example, due to the influence of illumination and hydrological conditions, the phenomenon of light scattering under water is serious, and the observation coverage of video surveillance equipment is limited. Better image enhancement or image restoration methods are needed to clarify underwater images to improve the detection efficiency and tracking accuracy of underwater fish targets. Among the many methods for realizing fish video tracking, traditional methods have complete theory and mature algorithms, but their adaptability is limited in special environments; on the one hand, deep learning methods have wider applicability and higher accuracy, but the model training time is longer, and more resources are occupied. On the other hand, the model is relatively complex, and it is necessary to compress the model to reduce the occupancy of hardware resources by the model, so that it can be easily transplanted into embedded devices. The method of tracking underwater fish targets with computer vision technology has more and more prominent advantages under the general trend of fishery resource survey and automatic processing of marine ecosystem monitoring, and is becoming the main development direction in the future. Keywords: computer vision; fish video; underwater image sharpening; fish tracking Related Articles | Metrics

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Research progress on the effect of light reduction on seagrass 2022, 44(5): 648.  Abstract ( 147 )   PDF (745KB) ( 466 )   Research progress on the effect of light reduction on seagrass FU Miao1, LIAO Liguo1, LIU Yingshuai1, MAO Wei1, CHEN Shiquan2, ZHANG Xiang1 (1. College of Ecology and Environment, Hainan University, Haikou570228, China; 2. Hainan Academy of Ocean and Fisheries Sciences，Haikou570125，China) Abstract: Seagrass meadow is one of the most important blue carbon ecosystems and contributes towards climate change mitigation through carbon sequestration and storage. Compared with terrestrial ecosystem, the pronounced capacity for carbon sequestration in blue carbon ecosystem is mainly due to the large range and longterm stable carbon sequestration. In addition, this is enhanced by coastal vegetation which is characterized by its high primary productivity and efficient water column filtration. Although seagrass covers less than 0.2% of the total area of the world’s oceans, the annual carbon storage of seagrass ecosystem is equivalent to 10% to 15% of its total carbon storage. It is estimated that the annual primary productivity of global seagrass ecosystem is about 1 012 g·DW·m-2, and the annual carbon burial amount approximately exceeds 27.4 TgC, which is equivalent to the sum of carbon storage in global tidal salt marshes and mangroves. Therefore, seagrass ecosystem can effectively alleviate the increase of carbon dioxide concentration. Other important ecosystem services include providing habitats, foraging and breeding places for many marine organisms, serving as an attachment base to provide adequate living space and nutrients for epiphytes. Furthermore, seagrass ecosystem can also effectively absorb suspended particulate matter, reduce wave energy, eliminate pollution, improve water quality and maintain the coast. However, since the 20th century, seagrass ecosystem has been declining at a rate of 7% of its total area annually, and its growth and distribution have been seriously threatened. Climate change and anthropogenic disturbances are considered to be the main factors causing the degradation and disappearance of seagrass ecosystem. To be specific, the reduction of water light transmittance caused by anthropogenic activities is considered one of the main reasons leading to the degradation of seagrass ecosystem. Light is the main environmental factor limiting the growth and distribution of seagrass. Solar energy is affected by many factors before reaching seagrass leaves, resulting in light energy loss. For example, loss of light energy may occur at the interface of air and water; the increase of suspended particulate matter and water depth can also cause the rapid attenuation of solar energy. Research on seagrass ecosystem in China has started relatively late. Besides, most of the studies on the impact of anthropogenic activities on seagrass ecosystem focus on the aspects of temperature stress, heavy metal pollution and water eutrophication; effects of water light transmission changes are unclear. Studying the effects of light reduction on the growth and physiological characteristics of seagrass ecosystem is helpful for the protection and restoration of seagrass ecosystem. Based on a series of studies on the effects of light reduction on seagrass ecosystems worldwide in recent years, this paper critically summarized and analyzed the minimum light requirements for seagrass growth and the factors of light reduction, and discussed the response mode of seagrass ecosystem to light reduction based on the growth and physiological changes of seagrass under light reduction. The results provided insight for understanding the decrease of water transmittance caused by anthropogenic disturbances and the impact of environmental changes on seagrass ecosystem. The study showes that the theoretical minimum light requirements for normal growth and development of seagrass is estimated at 11% of surface irradiance. In different light environments, seagrass has certain morphological plasticity, and the morphological characteristics of seagrass will change when the light changes. Seagrass can reduce its respiration requirement under light reduction by reducing leaf area and maintaining low plant density. Simultaneously, the decrease of photosynthetic rate will reduce the biomass of seagrass. Biomass is an important form of synthesis of organic matter by photosynthesis; thus, changes of photosynthetic rate will affect the accumulation of plant biomass. In addition, changes of light will also affect the allocation and utilization of biomass resources of plants. Seagrass can maintain its survival under environmental stress by changing the allocation strategy of biomass. Generally, the aboveground biomass of seagrass is greatly affected by light reduction, leading to the increased proportion of underground biomass. By promoting the growth of rhizome, the survival needs in low light environment are well balanced. However, other studies have shown that seagrass can enhance its light capture in low light environment by increasing the biomass of aboveground. The difference of biomass allocation to different tissues and organs is the effective utilization of limited resources by seagrass, which adapts to different environmental conditions through its own regulation mechanism. Photosynthetic pigment content is a good indicator of the photosynthetic physiology of plants, which can reflect the growth of plants. Generally, light reduction can promote the increase of chlorophyll content of seagrass, so as to effectively absorb limited light energy. In different light environments, the difference of chlorophyll content of seagrass may be related to the time and intensity of light stress, and the interspecific difference of seagrass species may also lead to different responses of chlorophyll content to light change. The longterm reduction of light may lead to the degradation or loss of seagrass ecosystem, resulting in the reduction of carbon storage. It may also cause the carbon stored to be unstable in sediment, because of the loss of seagrass shelter. Finally, it will reduce the carbon sequestration capacity of seagrass ecosystem, and even change it from carbon sink to carbon source. Currently, a large number of manipulation experiments have been conducted to investigate the effects of light reduction on seagrass ecosystem, but the results from these studies are inconsistent. Such inconsistent results might be affected by multiple factors, including biological, environmental and experimental variables. Then, the paper summarizes the current studies, and points out some aspects that are urgently needed to provide further insights in future studies, including expanding research scope and enriching research objects, improving research methods, strengthening research on the interaction of various factors, broadening research direction, strengthening and deepening mechanism research. Keywords: seagrass；light reduction；growth characteristic；physiological response Related Articles | Metrics