• ISSN 1000-0615
  • CN 31-1283/S
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Application advances and prospects of genome editing in molluscs
YU Hong, LIU Xin, LI Qi
In Press  doi: 10.11964/jfc.20210813004
[Abstract](0) [FullText HTML](0) [PDF 1517KB](0)
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Genome editing is an important means of genetic modification of organisms. It has been widely used in a broad spectrum of fields, such as functional genomics, animal model generation, genetic improvement of animals and plants, and gene therapy. In recent years, the emergence of CRISPR/Cas9 technology has sparked a revolution in biological research. Efficient, accurate and low-cost CRISPR technology has become a useful tool to explore gene functions and elucidate life phenomena, and its application in molluscs is emerging rapidly. In this review, we introduced the developmental course and working mechanisms of gene editing technology, and its application and prospects in molluscs, which might promote further application of genome editing in more molluscan researches, and provide information for identification of gene functions, determining genes related to economic trait, genetic improvement.
On strategies and approaches of high-quality development of coastal ecological farm and ranch in the Yellow River Delta
YUAN Xiutang, YU Zhenglin, WANG Qing, LIU Hui, ZHANG Libin, LIN Chenggang, WANG Tianming, LIU Fuxiang, XU Jialei, YANG Hongsheng
In Press  doi: 10.11964/jfc.20220113291
[Abstract](1) [FullText HTML](0) [PDF 0KB](0)
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The Yellow River Delta is rich in natural resources and has a unique ecosystem. The ecological protection and high-quality development in the Yellow River Delta have become a national strategy. Under the severe constraints of resources and environments as well as the serious degradation of ecosystems, the ecological protection and high-quality development of the Yellow River Delta urgently need the guidance and support of scientific and technological innovation. The implementation of coastal ecological farm and ranch is considered to be one of the important ways to achieve high-quality development. In order to create new models of green, low-carbon and circular coastal ecological farm and ranch in the Yellow River Delta, this paper analyzed the existing problems in coastal ecological farm and ranch, and put forward the high-quality developmental concepts and targets. At present, the unoptimized macroscopical planning, the incomplete industrial system, the imperfect innovation system, and the unstrengthened policy support of coastal ecological farm and ranch have restricted the high-quality development of coastal ecological farm and ranch in the Yellow River Delta. Furthermore, multi-driven high quality development approaches were raised as follows. Firstly, optimizing the macroscopical planning driven by water-salt scenario, that is, identify the complexity of the water-salt scenario and plan the layout reasonably; analyze the dynamics of the water-salt scenario and accomplish digital management. Secondly, highlighting the "chip" function driven by seed industry, that is, improve biodiversity based on native species protection; strengthen the cultivation of improved seed to enhance the driving force of industry; promote seed breeding to improve the coverage of seed industry. Thirdly, promoting model innovation driven by farm-aquaculture interaction, that is, connect land and sea to optimize industrial spatial layout; integrate farm and ranch, and establish linkage between Three Industries. Fourthly, realizing the intelligent upgrading of industry driven by equipment development, that is, build non humanized farms in saline and alkaline land; realize less populated farms and ranches on the tidal-flat area; create shallow sea intelligent ranches. Fifthly, innovating the collaborative paradigm driven by research-industry linkage, that is, integrate innovative elements to solve the problem of disconnection between industry and scientific research; financing through multiple channels to enhance innovation vitality. Finally, achieving industrial upgrading driven by governance policy, that is, integrate research and development resources and improve innovation ability; implement integrated development and strengthen the whole industrial chain; forward looking layout of special research projects and innovative development modes. Therefore, stakeholders could construct newly developmental models of coastal ecological farm and ranch in the Yellow River Delta with match of water-salt scenarios, integration of farm and ranch, and linkage of Three Industries, to realize the coordinated development of mechanization, intelligence, digitization and systematization. Our study is helpful to provide a reference for the high-quality development of coastal ecological farm and ranch in the Yellow River Delta.
Protection and utilization status and prospect of large yellow croaker (Larimichthys crocea) germplasm resources
XU Peng, KE Qiaozhen, SU Yongquan, LIU Jiafu, ZHENG Weiqiang
In Press  doi: 10.11964/jfc.20210312688
[Abstract](5) [FullText HTML](3) [PDF 1618KB](0)
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The excavation and utilization of excellent germplasm resources is pivotal in ensuring the supply of China’s high-quality aquatic protein. As Larimichthys crocea owns China’s highest production in marine aquaculture, and its germplasm resources serve as an indispensable material basis for the healthy and sustainable development of the L. crocea breeding industry, it is of great strategic significance to carry out the collection, preservation, identification, evaluation, protection and utilization of L. crocea germplasm resources systematically. This paper has reviewed the history and present situation of germplasm protection and utilization of L. crocea, and analyzed the main problems currently faced from the aspects of scientific research, breeding technology system, industry, and talents. Besides. focusing on the scientific and technological innovation of the L. crocea seed industry and the creation of new varieties, the development direction that creating major new species with such quality as disease resistance, stress resistance, high yield, high quality, and high compound feed conversion rate that has been proposed to substantially expanded the coverage of improved L. crocea and provide a thoroughbred guarantee for the healthy development of the L. crocea industry.
Genomic evolution and virulence-associated genes of the Flavobacterium psychrophilum CH06 isolated from Oncorhynchus mykiss
CHEN Fuguang, LI Shaowu, LU Tongyan
In Press  doi: 10.11964/jfc.20200912406
[Abstract](6) [FullText HTML](3) [PDF 5986KB](0)
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Flavobacterium psychrophilum, the causative agent of bacterial cold-water disease and rainbow trout fry syndrome, is currently an important pathogen causing great economic loss for the salmonid industry worldwide. Recently, the genomic evolution and pathogenic mechanisms of F. psychrophilum have been widely studied in many countries. However, these studies originated from China are still poorly reported. In order to better understand the genomic evolution and pathogenesis of F. psychrophilum in China, the virulent strain CH06 was subjected to whole genome sequencing and analyzed using comparative genomics, and virulence-associated genes were predicted. The result of whole genome sequencing shows that the CH06 genome consists of a single circular chromosome of 2 836 981 base pair (bp) harboring 2 437 protein-coding genes with an overall G+C content of 32.56%. The results of ANI analysis show that ANI values between CH06 and 12 F. psychrophilum strains are higher than 99%, indicating that CH06 belongs to F. psychrophilum. Analysis of the genome sequence reveals that CH06 consists of 5 insertion sequences, 4 genomic islands and 3 prophage sequences, indicating that these mobile genetic elements lead to the genome evolution of CH06. Collinear and phylogenetic analysis shows that CH06 is more closely related to CSF259-93 and FPG101. Secretion system analysis shows that CH06 carries full type I (T1SS) and type IX (T9SS) secretion system. The 2 437 predicted proteins are further examined and 27 proteins are predicted to be secreted by the T9SS. Furthermore, CH06 is predicted to encode 10 histidine kinases (HKs) and 15 response regulators (RRs), revealing that CH06 has evolved sophisticated mechanisms to export various virulence factors across the bacterial cell envelope, and sense and respond to environmental changes. In this study, the genomic evolution and virulence-associated genes of CH06 are analyzed, providing a basis for research on the genomic evolution and diversity and pathogenic mechanisms of this fish pathogen in China.
Distribution and drift trend of Collichthys lucidus larvae and juveniles in the coastal waters of the southern Yellow Sea
ZOU Mingxi, CHEN Yuange, SONG Xiaojing, LI Shengfa, ZHONG Junsheng
Accepted Manuscript  doi: 10.11964/jfc.20201112499
[Abstract](6) [FullText HTML](2) [PDF 5812KB](0)
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Changes in abundance and distribution during the fish larvae and juveniles period can affect the size of fish replenishment groups and, consequently, changes in the size of fish populations.The study of early-stage fish resources has great value to understanding fish stocks recruitment and the assessment of fishery resources. In this study, 47 stations(119°00′-123°00′E, 31°00′-35°00′N) were investigated in the nearshore waters of the southern Yellow Sea from March 2019 to January 2020. Fish larvae were monthly collected using a larval fish net(1.3 m diameter at the mouth, 6.0 m length, 0.5 mm mesh aperture) during the high tide to reveal the spatial-temporal distribution and drifting trends of larval and juvenile Collichthys lucidus. The environmental factors (surface water temperature, surface salinity, water depth) of the surveyed waters were also measured, and the spatial and temporal distribution characteristics and drift trends of the abundance of C. lucidus fish larvae and juveniles were analyzed. The relationship between environmental factors and fish larvae distribution was analyzed by a GAM model. A total of 2385 fish larvae were collected from June to October, with the highest abundance in June (165.15 ind./100 m3) and a decreasing trend month by month. Each month's most dominant developmental stages changed from pre-flexion larvae to juveniles in the order of months, except that only one post-flexion larva was collected in October. The results of the GAM model showed that the deviation of abundance was explained by latitude and longitude with the highest rate of 52.3%, followed by month and surface salinity. We conclude that the inshore waters of the southern Yellow sea were nursery ground for C. lucidus, with its eggs and pre-flexion larvae dispersed passively. Then, the post-flexion larvae and juveniles drift inshore with growth and development under the influence of environmental factors such as surface salinity, surface water temperature, and water depth. Juvenile dominated in September and subsequently disappeared from the samples, implying potential recruitment success.
Cause analysis of resources change and reconstruction strategy of Larimichthys crocea Daiqu group in the East China Sea
YU Cungen, YAN Xiaojun, JIANG Qiaoli, ZHANG Yingliang
In Press  doi: 10.11964/jfc.20211013126
[Abstract](34) [FullText HTML](15) [PDF 1356KB](0)
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The Larimichthys crocea Daiqu group in the East China Sea was once one of the most commercially important demersal fishes unique to China's coastal waters. It is now an important target for our country to restore and rebuild the resources of L. crocea. In order to clarify the influencing factors of the decline of its resources, and reveal the selectivity of its habitat and the reasons why the resources of the L. crocea are difficult to recover, this paper took the L. crocea fishing output in Zhejiang Province from 1950 to 2020 as a sample, and analyzed the correlation between the population number changes of the L. crocea Daiqu group and major fishery events, such as knocking operation and rounding up the overwintering group in the central fishing ground, by using index analysis method, which aims to trace the causes of the decline of large yellow croaker resources; The biological characteristics and evolution of L. crocea and its adaptability to habitat were described by comprehensive literature analysis. The results showed that: (1) the main causes of the decline and depletion of L. crocea resources were caused by several unreasonable development and utilization methods, such as knocking operation, catching the incoming fishes and overfishing the wintering grounds; (2) L. crocea has the characteristics of long life span, late sexual maturity, complex population structure, and strong habitat environmental selectivity, among which temperature, salinity, flow rate, substrate and feed organisms are the key environmental factors; (3) Due to overfishing, the life history of L. crocea deviated from the original selection position, but it still belonged to K selection game. (4) In addition to human factors (such as excessive fishing intensity), the main factors affecting the recovery of L. crocea resources may also be related to the k-biased life history and habitat selection of large yellow croaker. What’s more, this study also put forward the future protection and proliferation strategies of L. crocea from the perspective of biological characteristics and habitat environmental selectivity, which provides a decision-making basis for the restoration and reconstruction of L. crocea Daiqu group in the East China Sea.
Effects of tied-up relaying on stress-reduction and storage-stability of live dived Patinopecten yessoensis
LI Yaxuan, LIU Junrong, ZHOU Jin, ZHAO Qian, TIAN Yuanyong, XU Tanye
In Press  doi: 10.11964/jfc.20200912394
[Abstract](40) [FullText HTML](20) [PDF 1682KB](0)
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In order to minimize physiological stress, thus improving live P. yessoensis condition and survival rate, commercia hand-dived P. yessoensis, were tied-up during land base relaying, and the effects of stress reduction on storage stability was investigated. One week supply chain from harvest to market for live scallops were designed including 2-day’s on-land revitalization (i.e., relaying)and subsequent 4-day’s chilled dry-storage. Live P. yessoensis were tied-up individually to enforced shell-valve closure pre-relying as treatment Tb and post-relying as treatment Ta, changes of live P. yessoensis fitness were investigated comparing to the treatment-free control group named C. ATP related substances, nucleotide energy charge AEC, arginine phosphate ArP, pH and glycogen were selected as fitness indicators. Sensory assessment and visual vitality indicated by mantle retraction and mantle response were conducted as well.Results showed that both Tb and Ta had a significant effect on sustaining P. yessoensis fitness in subsequent steps in the supply chain. ① the level of ATP, ArP, glycogen and other biochemical indicators ordered as Tb>Ta>C. On the 6th day, both Tb and Ta present better fitness than the control C. ② tying-up hold a delayed advanced effect on sustaining fitness in the subsequent dry storage. Results analyses showed that, the order of positive effects is Tb>Ta>C, and a positive correlation between mantle retraction and mantle retraction was observed. ③ sensory analysis results also revealed the advantages of delayed effect induced by tying-up in advance. At the relaying stage, tying-up made no difference in flavor profiles between the groups. Sensory quality of all the P. yessoensis tended to decline based on the sensory evaluation. However, it was observed that the Tb has always shown obvious advantages in umami and sweetness than others. In summary, the tied-up closure treatment can effectively suppress the physiological stress accompanied by reduced energy consumption. Thereby, high quality live P. yessoensis can be supplied to the market. Based on the experimental results of this study, several potential improvements to current post-harvest handling and transportation of P. yessoensis are suggested.
Preliminary study on the functions of kinase X gene in Hyriopsis cumingii
CUI Xiaoyu, DONG Saisai, DUAN Shenghua, WANG Guiling, LI Jiale
In Press  doi: 10.11964/jfc.20201012453
[Abstract](43) [FullText HTML](17) [PDF 1607KB](0)
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Hyriopsis cumingii is a unique freshwater breeding pearl mussel in our country. It occupies an important position in the aquaculture industry. In the actual breeding process, male individuals have a more obvious advantage in pearl production than female individuals. Therefore, research on the sex determination of H. cumingii is crucial important. Previous studies have found that Sox9 gene plays a role in male sex determination in many species, kinase X gene is an important gene in the synthesis of protein kinase (PKA), and PKA play a vital role in many physiological and biochemical processes, especially in the process of spermatogenesis. In this process, PKA has a very obvious effect on sperm capacitation. The kinase X gene and Sox9 gene are both located in cAMP-PKA pathway. And the relationship of the kinase X gene and Sox9 gene are upstream and downstream. It is speculated that the Sox9 gene may be regulated by PKA. The results showed that the kinase X gene was 1 652 bp in length, the 3′ UTR is 314 bp, while the length of the 5′ UTR is 45 bp, encoding 430 amino acids, and there was an STKYc structure domain which is located at 381-1179 bp, kinase X gene has a transmembrane domain and the Molecular weight (Mw) of the kinase X protein was 49.00 ku and the theoretical Isoelectric point (pI) was 8.22, among that which Leu(L) was the most abundant amino acid, accounting for 9.8%; the homology analysis showed that H. cumingii had a high similarity with other shellfish such as Mizuhopecten yessoensis, Chlamys farreri. The phylogenetic tree showed that H. cumingii had a close relationship with Crassocras gigas and Crassostrea virginica, but had a long genetic distance with mammals. The fluorescence quantitative PCR results showed that the kinase X gene was expressed in 6 tissues including gonads, gill, adductor muscle, foot, mantle, liver of the 2 year H. cumingii , the kinase X gene was expressed the highest in the male gonads while expressed the lowest in the female liver. And in 1-3 year of H. cumingii, the expression of kinase X gene in male is all higher than that in female, and the difference between male and female is extremely significant. Among them, the expression of kinase X gene in 2 year H. cumingii is highest among 1 ~3 year. Due to the high expression of the kinase X gene of the 2 year H. cumingii near the sexual maturity stage, the sperm occurrence rate is high; after 7 days of interference, the expression of kinase X gene decreased. RNA interference results show that the synthesized 3 interference chains have a certain interference efficiency on the kinase X gene, and the interference rate of the interference chain 1 is the highest. The interference rate is 83.1% in females and 81.9% in males, while interference chain 2 has an interference rate of 76.0% in females and 25.7% in males; interference chain 3 has an interference rate of 24.0% in females and 67.7% in males. At the same time, the Sox9 gene expression decreased by 90.3% in females and 56.6% in males after the interference of interfere chain 1. That improved the synthesis of kinase X gene was positively correlated with the synthesis of Sox9 gene. It is speculated that the two may work together to participate in the sex determination process through the cAMP-PKA-mediated signaling pathway. In this experiment, through preliminary functional exploration of the kinase X gene, it was found that the upstream and downstream relationship between kinase X gene and Sox9 gene and the two were positively correlated, and it effectively interfered with the kinase X gene, which is important in cAPM-PKA of H. cumingii. This study provides a theoretical basis for the study of sex determination and male parthenogenesis of H. cumingii.
Purification and characterization of a prolyl endopeptidase from Haliotis discus hannai
CHEN Shoufeng, YANG Ruqing, CHEN Yulei, SUN Lechang, ZHANG Lingjing, LIU Guangming, CAO Minjie
In Press  doi: 10.11964/jfc.20201212599
[Abstract](42) [FullText HTML](17) [PDF 1978KB](0)
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Prolyl endopeptidase (PEP) is a serine protease which has been implicated in many biological processes, such as learning and memory, cell proliferation and differentiation, and glucose metabolism. A small number of reports have also suggested PEP participates in mammalian reproductive process by specifically degrading peptide hormones and gonadal hormones containing proline residues. Compared with mammals, research on PEP of mollusks is relatively scarce at home and abroad. This observation led us to investigate PEP and whether it is related to reproductive development of mollusk. We analyzed the natural PEP of Haliotis discus hannai and the protein expression level changes during gonad development. Fluorescence quantitative PCR (qRT-PCR) and enzyme activity analysis were used to detect the expression of the PEP in tissues of H. discus hannai. The enzyme activity and the expression level of PEP in H. discus hannai gonad, followed by the muscle. PEP was purified from the gonad by column chromatography with a molecular weight of 82 ku. The isoelectric point of PEP was 5.5 by two dimensional electrophoresis, it is similar to the isoelectric point of predicting PEP of abalone. The 182 peptides were obtained by LC/MS/MS analysis, which were consistent with the H. discus hannai prolyl endopeptidase of NCBI (KY214290). The analysis of enzymatic properties showed that the optimum temperature and pH of PEP are 25 °C and 6.0, respectively, high enzyme activity can be maintained at 15-25 °C and pH 5-8. Circular dichroism was used to analyze the effect of temperature on structure of PEP. The results showed that the secondary structure of PEP changed significantly as the temperature increased. When the temperature increases from 25 °C to 95 °C, the content of α-helix structure decreases from 12.5% to 5.8%, and the random coil increases from 24.4% to 28%, when the temperature was lowered from 95 °C to its optimum temperature (25 °C), the content of α-helical structure decreased by 1%, β-folding decreased by 4.6%, β-turn and random coiling structure increased by 1.5% and 2.4%, respectively, compared with the initial secondary structure at the same temperature. The secondary structure could not be restored, indicating that the thermal denaturing of PEP was irreversible. The fitting thermal denaturation temperature was 51.4±0.2 °C. In order to further analyze the protein and gene expression level of PEP in the development of H. discus hannai gonad, we divide abalone gonad development into different growth stages (preliminary, early, middle and late growth stages), the results of Western blot and qRT-PCR analysis showed that PEP could be detected in all stages of male and female. The expression level is highest in the middle stage of maturity of male gonad and the late stage of maturity of female gonad. These results indicated that the difference of PEP at developmental stages of H. discus hannai gonad demonstrated that it may be involved in the process of gonad development. The current study analyzed PEP of mollusks and speculated that PEP is associated with gonad development in H. discus hannai. It provides a theoretical reference for further research of the function of PEP in H. discus hannai gonad development.
Effects of manna oligosaccharides on flesh quality of Nile tilapia (Oreochromis niloticus) fed with high carbohydrate diet
MA Yingying, JIA Yongyi, GU Tingting, ZHANG Zhiyong, WANG Tong, ZHANG Meiling, DU Zhenyu, QIAO Fang
In Press  doi: 10.11964/jfc.20210712941
[Abstract](44) [FullText HTML](21) [PDF 1860KB](2)
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Mannan oligosaccharide is a new kind of feed additives. However, the effects of manna oligosaccharides on fish flesh quality has not been well studied. In this study, 315 healthy juvenile Oreochromis niloticus with an average body weight of (2.2±0.2) g were randomly divided into three treatment groups: control group (35% carbohydrate), high carbohydrate diet group (HC, 45% carbohydrate) and high carbohydrate diet supplemented with mannan-oligosaccharide (HM, 45% carbohydrate, 0.5% mannan oligosaccharide). Three tanks for each group, and 35 fish reared in each tank. After the feeding trial for 10 weeks, the growth indicator, muscle nutritional composition and flesh texture were determined. Compared with the control group, the hepatosomatic index, muscle cohesiveness, the myofiber number, the content of inosinic acid and triglyceride, the proportion of delicious amino acids, and the relative expression of CAST gene, which could improve muscle growth, in the fish of HC group were significantly increased; the muscle hardness, gumminess and chewiness, myofiber diameter, cooking loss, the proportion of essential amino acids, the contents of fatty acids, diglyceride and phosphatidylinositol, and the relative expression of MyoG gene, which functions in the differentiation of muscle fibers, in the fish of HC group were significantly decreased. Compared with the HC group, muscle springness, the proportion of essential amino acids, contents of fatty acids and diglyceride and the CAST gene relative expression were significantly increased in O. niloticus of HM group; the muscle adhesion, the number of myofiber, the contents of inosinic acid, phosphatidylethanolamine and phosphatidyl choline, and the MyoG gene relative expression in Nile tilapia of HM group were significantly decreased. Compared with the control group, the weight gain rate, muscle cohesion and contents of triglyceride and fatty acids were significantly increased in fish of the HM group; the hepatosomatic index, muscle hardness and chewiness, content of phospholipid in the fish of HM group were significantly decreased. The above results indicated that with the addition of manna oligosaccharides in high carbohydrate diet, the meat yield of O. niloticus was greatly improved, the flesh quality was improved due to the elevated water holding capacity, texture and the nutritional value of amino acids, however the decreased phospholipid content should not be neglected.
Spatial and temporal distribution of fish assemblages and its relationship with environmental factors in Lake Gehu
LI Jingwei, XU Dongpo, LI Wei, KONG Youjia, HUA Shaopeng, LIU Qigen, ZHANG Shun, HU Zhongjun
In Press  doi: 10.11964/jfc.20200812358
[Abstract](39) [FullText HTML](19) [PDF 2398KB](0)
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In order to understand the status and dynamics of fish community in Gehu Lake, the fishes at 16 stations in Lake Gehu were seasonally sampled using multi-mesh gillnets and traps from August, 2017 to May, 2018. Meanwhile, water temperature (WT), water depth (WD), transparency (SD), pH, chlorophyll a (Chl.a), total nitrogen (TN), total phosphorus (TP) were measured. Using these data, fish community structural characteristics, the spatial and temporal distribution pattern and its relationship with environmental factors were analyzed. A total of thirty-six fish species, belonging to 4 orders and 8 families, were collected from Lake Gehu. According to index of relative importance (IRI), Japanese grenadier anchovy (Coilia nasus) was the predominant species, silver carp (Hypophthalmichthys molitrix) and goldfish (Carassius auratus) were the common species. Sedentary fishes (83.3%) predominated in species number among the three ecological groups and omnivorous fishes (47.2%) prevailed among the five feeding functional groups. The fish species composition in Lake Gehu did not differ monthly and spatially. The Two-Way analysis of variance (ANOVA) showed that number per catch effort (NPUE), richness index (R), Shannon-Weaver's diversity index (H´) and evenness index (J) significantly differed but biomass per catch effort (BPUE) did not differ monthly, and all the five structural features except for R did not significantly differ between lake areas. Redundancy analysis revealed that WT and TP were the key factors influencing the spatial and temporal distribution of fish species of Lake Gehu. The results suggested that since 1950S the fish diversity have declined markedly and the species and product composition changed greatly, and which are speculated to be responsible for sharp degradation of macrophyte vegetation, overfishing, disconnection between lake and river, and breeding and enhancement.
Evaluation of genetic parameters of body length, body weight and WSSV resistance of Litopenaeus vannamei based on microsatellite markers
SUN Kun, LI Xupeng, SUI Juan, CAO Jiawang, TAN Jian, LUO Kun, LUAN Sheng, KONG Jie, MENG Xianhong
In Press  doi: 10.11964/jfc.20200512253
[Abstract](44) [FullText HTML](18) [PDF 2032KB](0)
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In order to evaluate the genetic parameters of body length, weight and WSSV resistance of Litopenaeus vannamei more accurately, 8 microsatellite loci were used to genotype mother and offspring of 69 families of L. vannamei, and the pedigree reconstruction and the calculation of the molecular relationship correlation were carried out by using the genotyping information. The reconstructed pedigree, the molecular affinity and the physical pedigree were used to construct the additive genetic correlation matrix. Then, the genetic parameters of body length, body weight and WSSV resistance were evaluated. Finally, through the cross validation method, the prediction ability and accuracy of genetic parameter evaluation were compared. The results of genotyping showed that 166 alleles were detected in 8 microsatellite loci, the number of alleles in each locus was 12-45, the average number of alleles in each locus in parent and offspring population was 9.50 and 18.13, the average observed heterozygosity was 0.618 and 0.709, the average expected heterozygosity was 0.749 and 0.775, the average polymorphism information content was 0.711 and 0.750, respectively, all of loci showed high polymorphism. The heritability of reconstructed pedigree, molecular affinity and physical pedigree analysis showed that the heritability of body length was 0.119±0.031, 0.120±0.032, 0.132±0.030, the heritability of body weight was 0.176±0.039, 0.182±0.040, 0.172±0.034, and the heritability of resistance to WSSV was 0.135±0.033, 0.134±0.033 and 0.098±0.031, respectively. In the heritability of body length, body weight and resistance to WSSV, the standard deviation of molecular affinity was smaller than that of reconstructed pedigree and physical pedigree. Through cross validation, the prediction ability and accuracy of the three genetic parameters evaluation from high to low are molecular affinity, reconstructed pedigree and physical pedigree. The results showed that it was more accurate to evaluate the body length, body weight and WSSV resistance of L. vannamei by using microsatellite molecular markers than using physical pedigree. In the method of evaluating heritability by using microsatellite molecular markers, it was more effective to directly use the genetic correlation of offspring. This study provides a more accurate method for the evaluation of genetic parameters of L. vannamei and a reference for further breeding.
Recent progress in the germplasm resources conservation and utilization of the Chinese giant salamander (Andrias davidianus)
JIANG Wansheng, LAN Xiangying, WANG Jinxiu, XIANG Hongmei, TIAN He, LUO Qinghua
In Press  doi: 10.11964/jfc.20210812993
[Abstract](83) [FullText HTML](32) [PDF 3478KB](0)
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The Chinese giant salamander (CGS, Andrias davidianus) is the largest extant amphibian species in the world, with significant scientific, ecological and economical values. According to the Chinese law, wild populations of CGS are treated as the class II state protected species, while the second and beyond generations of captive-bred CGS can be utilized as aquatic products or resources for the food and pharmaceutical industry. As one of the endemic and rare animals in China that possessing both conservation and utilization values, the process about germplasm resources of CGS has raised considerable concern. Although with multiple conservative status, the current situation of wild CGS is still unoptimistic. The present practices and effects on the conservation of CGS through in-situ conservation in terms of nature reserves and ex-situ conservation by artificial enhancement and translocation are still to be evaluated. In contrast, with the increasing development of artificial culture and expanding of the husbandry scales, the captive-bred CGS has become one of the new aquaculture species with good market prospects. However, the disease control is still one of the bottleneck problems during the process of captive breeding. CGS is one of the high-valued aquaculture species with high protein and low fat, and additionally, its bioactive substances and efficacies are being revealed gradually. However, by restrictions of the market, industry, and the input of scientific research, the scale of captive CGS is still very limited, thus the scope and depth of its utilization need to be greatly strengthened. Based on the studies from previous papers and the practices from our team, in this study we reviewed the conservation and utilization of the germplasm resources of CGS, from the aspects of basic biology, habitat characteristics, genetic diversity, conservation, captive breeding, disease, nutrition, bioactive substances, industrial utilization, etc. By summarizing the successful experiences and identifying the problems, this paper aims to provide a valuable reference for studying the genetic germplasm resources, planning of the conservation strategies, developing and sustainable utilization, as well as enhancing the public awareness to this precious species in the future.
Effects of marine environment variation on the growth of neon flying squid (Ommastrephes bartramii) in the north Pacific Ocean
WANG Yan, CHEN Xinjun, FANG Zhou
In Press  doi: 10.11964/jfc.20201012455
[Abstract](382) [FullText HTML](171) [PDF 4013KB](23)
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The neon flying squid (Ommastrephes bartramii) is a dominate economic species in the north Pacific Ocean. Marine environment variation has a profound impact on the marine organisms and their growth. As a shortlifespan oceanic cephalopod, O. bartramii is highly susceptible to the climate change in different degrees, such as the Pacific Decadal Oscillation (PDO), El Niño and La Niña. Consequently, investigation on growth of O. bartramii affected by variable marine environment becomes an important and basic part for cephalopod research. Based on 6091 samples of O.bartramii collected in fishing season (from August to October) from 2009 to 2012 and 2015 to 2016 in the north Pacific Ocean, the growth of O. bartramii was studied combined with the marine environmental factors in the present study. The results indicated that significant difference of fishery biological characteristics was found between different gender and marine environment years. Viewed from the difference of the dominated mantle length (ML) and body weight (BW) group, maximum values of both ML and BW occurred in 2016, while minimum values occurred in 2010 and 2015. The b values of ML-BW relationship in all sample years were significantly different with 3, which showed allometric growth. The mature stage of both female and male squids concentrated in stage II, and the proportion of mature female squid was less than that of male squids. The maturation of ML of O. bartramii was positively correlated to the Pacific Decadal Oscillation index with one-year lag. Samples in El Niño years were lager than those in La Niña years, and individuals in El Niño year with very strong intensity were the smallest. The El Niño event with very strong intensity caused low sea surface temperature (SST) and low Chlorophyll a (Chl. a) concentration which was not beneficial to the growth and their gonad development of O. bartramii. Higher SST and Chl. a concentration provided favorable environment for O. bartramii, resulting in a larger body size and early maturation. The present study suggested that the growth and gonad development had significant difference among different marine environment years, and the synthetic influences of PDO, El Niño/La Niña, SST and Chl. a concentration were the dominate factors that affected the growth of O. bartramii.
Developmental status and vision for the future of China’s deep blue fishery
LIU Yongxin, LIU Huang, FANG Hui, XU Hao, WANG Lumin, LIU Yingjie
Accepted Manuscript  doi: 10.11964/jfc.20210512869
[Abstract](107) [FullText HTML](45) [PDF 2408KB](2)
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China has become the powerhouse of aquaculture in the world in the past 40 years. With the rapid development of aquaculture, the different kinds of trouble also keep emerging in China. In particularly, the performance of unbalanced and inadequate aquaculture industry mainly exhibited the adequate supply, low quality and safety of aquatic products. Along with the farming areas of inland waters, land-based and coastal waters constantly being squeezed, the deep blue fishery are the revolutionary transformation of production mode for becoming the blue ocean to blue granary. Deep blue fishery is the aquaculture production system with the integration of whole industry chain including the aquaculture, fishing and aquatic products processing. The deep blue fishery covers marine space which included the near shore and off shore of Bohai Yellow sea, East Sea and South sea as well as open ocean and polar region. As the expansion and extension of blue granary, it combines the different key points including breed, aquaculture, fishing, processing and web with an organic whole, which plays an important role in ensuring the supply of high-quality protein, broadening the new space of culture and supporting the blue economic growth and safeguarding China's maritime rights and interests. With over growing science endeavors and further industrialization practice in recent years, the deep blue fishery has made a rapid development, but it still faces the gradually emerging opportunity and challenge. This paper synthetically analyzes the strategic significance and main production function of developing deep blue fishery and summarize the prominent problems restricting its development. The major production function of deep blue fishery contained offshore industrialized farming, exploitation of biological resources in oceanic and polar regions as well as offshore logistics and information channel. According to summarize the existed main problems and restrict factors, whose focus was mainly put on four aspects. Firstly, the exploitation and utilization of natural resource were not very efficient. Secondly, the overall level of equipment and technology was still relatively backward. There was, in addition, obviously insufficient total production capacity and weaker support ability for scientific research. On the basis of the development goals, the intensive scientific and technical tasks are proposed that involve in analyzing the genetic resources of deep blue biology, building the industrialized green production patterns and high-quality fishing the resources originating from open ocean and polar region, researching the technology and equipment of processing links across land and over sea as well as constructing fishery boats networking system and so on. Relevant measure suggestions are also proposed, such as implementing the technology capability promotion project, introducing industrial development supporting policies, building diversified talents congregate highland and establishing industrial innovation garden for demonstration, which aims to provide the lesson and reference for accelerating the technological advancements of deep blue fishery and promoting the iterative upgrade of industry. In summary, the deep blue fishery is a new rising industry of China. As an efficient way of the adjustment of the industrial structure and transferring the mode of production in aquaculture, it needs strong support of the scientists, government officials and other aspects.
Characteristics of formation related genes (PyMFG) of monospores and analysis of differential expression in Pyropia yezoensis
SONG Shanshan, DING Hongchang, YAN Xinghong
In Press  doi: 10.11964/jfc.20190311710
[Abstract](1773) [FullText HTML](563) [PDF 2804KB](41)
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In our study, a complete open reading frame of PyMFG was obtained by RT-PCR based on the sequence of differentially expressed genes (Contig-21827) screened by transcriptome sequencing of Pyropia yezoensis. Sequence analysis showed that the ORF of the PyMFG was 1 224 bp in length and encoded a polypeptide fragment of 407 amino acids with a molecular weight of 46.24 ku, and theoretical pI of 9.08. Domain analysis revealed that the protein contains a conserved TEA domain and a YAP domain, which belongs to the TEA-ATTS superfamily domain. We found that the protein and fungal conidia forming proteins clustered into one large branch with close genetic relationship through multiple sequence alignment and phylogenetic analysis. In addition, the comparison of the ability of releasing monospores and qRT-PCR analysis between different strains indicated that the expression trend of PyMFG in PY26W and PY26W' was highly consistent with macroscopic statistical results, while the trend in PY26R and PY26R' were exactly existed difference. By inference, the gene type and molecular mechanism regulating the formation and release of monospores in the parental (PY26W) and partial parental strain (PY26W') and the female parental (PY26R) as well as partial female strain (PY26R') existed certain difference, leading to the divergence between the macroscopic statistical results of monospores and the qRT-PCR results.
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2022, 46(3).  
[Abstract](0) [PDF 1633KB](0)
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2022, 46(3): 1-2.  
[Abstract](0) [FullText HTML](0) [PDF 215KB](0)
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Temporal and spatial distribution of Antarctic krill (Euphausia superba) swarms in the Bransfield Strait, Antarctic in autumn 2020
DONG Sisong, KONG Qunqun, ZHU Guoping
2022, 46(3): 337-348.   doi: 10.11964/jfc.20211213260
[Abstract](57) [FullText HTML](29) [PDF 2489KB](1)
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Antarctic krill (Euphausia superba) is a key species in the Antarctic marine ecosystem with important potential for commercial exploitation, however, significant heterogeneity in type and distribution of krill swarms increases the difficulty of biomass estimation and also brings the challenges for at-sea operation and working plan to fishing company. Therefore, using acoustic data collected from fishing vessels, the spatial and temporal distribution characteristics, diel differences, and swarm structures of Antarctic krill swarms in the fishing grounds of the Bransfield Strait were analysed with the aim of improving fishing efficiency. The results indicated that, in the Bransfield Strait, krill swarms were primarily located in the southern shelf waters in autumn 2020, and that the number of krill swarms increased over time in autumn. Most krill swarms can be found in water layers between the surface and the depth of 150 meters, but some swarms also occur close to the bottom. The diel distribution of krill swarms varied, with a general tendency of reversed diel vertical migration that moves up to the surface in the daytime but sinks to the deeper layer at night. The layered type of swarm with a high density is dominant in the daytime, while scattered type of swarm with low density occupies a high proportion at night. The density within swarms is correlated positively with swarm length. In general, the daytime layered type of swarms within the Bransfield Strait are suitable for fishing vessels. Understanding krill swarm distribution is beneficial to understanding their formation characteristics of krill fishing ground as well as enhancing the productivity of fishing vessels.
Temporal and spatial distribution characteristics of Antarctic krill (Euphausia superba) aggregations in South Shetland Islands in autumn and winter of 2019
LI Shuai, LI Lingzhi, FENG Chao, YANG Jialiang, ZHANG Gangchen, RAO Xin, HUANG Hongliang
2022, 46(3): 349-358.   doi: 10.11964/jfc.20211013113
[Abstract](50) [FullText HTML](25) [PDF 2259KB](0)
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To further study the temporal and spatial distribution characteristics of Antarctic krill (Euphausia superba) aggregations in the waters near the South Shetland Islands, based on the acoustic surveys of Chinese E. superba production fishing vessels and commercial fishing data in the 2018/2019 fishing seasons, the center depth, water temperature and morphology of E. superba aggregations were analyzed. The results showed that there were significant temporal and spatial differences in the depth of E. superba aggregations center, the temperature at the depth of Antarctic krill aggregations and aggregations morphology in the waters near the South Shetland Islands (P<0.05). The average aggregations center depth, whose variation range was 34.39 to 86.12 m, showed an increasing trend from April to July, the difference between day and night was small (P=0.325), and the peak periods were sun rising (SRS) and night (NIT), which were 64.06 and 65.32 m respectively. The low value range of average aggregations center depth was 62.75°−63.75°S and 58.25°−59.75°W, and the high value range was 61.75°−62.25°S and 60.25°−61.75°W. The average temperature at the depth of E. superba aggregations, whose variation range was −1.71 to −1.50 °C, showed a decreasing trend from April to July. The peak period was NIT and evening twilight (ETW), which were −1.46 °C and −1.40 °C respectively. The low value range of average aggregations water temperature was 62.75°−63.75°S and 61.25°−61.75°W, and the high value range was 61.75°−62.25°S and 58.25°−60.75°W. The cluster shape was mainly stripped from April to May and scattered from June to July. The cluster shape was mainly horizontal band from day to afternoon (AFT), and the cluster shape was mainly scattered from sunset (SST) to morning (MRN). The results showed that there were obvious temporal and spatial differences in the depth of E. superba cluster center, cluster water temperature and cluster shape in the waters near the South Shetland Islands. The difference between months was greater than that between day and night, and had relative consistency in spatial variation.
Scale effect of spatial pattern for Antarctic krill (Euphausia superba) distribution around Antarctic Peninsula based on changepoint analysis
LIU Hui, ZHU Guoping
2022, 46(3): 359-367.   doi: 10.11964/jfc.20211213240
[Abstract](62) [FullText HTML](23) [PDF 2010KB](1)
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As a key species in the Antarctic ecosystem, distribution of Antarctic krill (Euphausia superba) resources demonstrates significant spatial-temporal heterogeneity. Different spatial scales may give different results when analyzing the spatial pattern of Antarctic krill. In order to analyze the influence of different spatial scales on the spatial pattern of Antarctic krill, based on the biomass data of Antarctic krill in the waters near the Antarctic Peninsula from 1996 to 2011, Moran’s I, Geary’s C and Ripley's K value were calculated to analyze the spatial pattern of Antarctic krill resources, and to detect changepoints of various spatial indicators at different spatial scales. The results showed that the value of global Moran’s I decreased as the increasing of spatial scales, the value of Geary’s C increased but then decreased. The results of the generalized estimation equation showed that both spatial scale and distance had a significant impact on the K′ value. In general, Antarctic krill around the Antarctic Peninsula had a high-density cluster distribution. and the aggregation degree of Antarctic krill around Antarctic Peninsula decreased with the increasing of the spatial scales. The changepoint detection showed that 25'×25' was the spatial scale where multiple spatial indicators qualitative change. Therefore, this study suggests 25'×25' can be considered as the scale threshold for comparing the results of such studies within the scale of 1′×1′~60′×60′. This study explored the scale effect of the spatial distribution of Antarctic krill resources, which can provide a scientific basis for further research on the spatial and temporal distribution of local krill resources and the formation mechanism of fishing grounds.
Spatio-temporal evolution characteristics of Antarctic krill (Euphausia superba) fishing ground in the northern waters of Antarctic Peninsula based on spatial autocorrelation model
ZHAO Guoqing, SONG Xuefeng, XU Bo, YANG Jialiang, LI Shuai, RAO Xin, HUANG Hongliang, ZHANG Heng
2022, 46(3): 368-378.   doi: 10.11964/jfc.20210813042
[Abstract](41) [FullText HTML](19) [PDF 11909KB](0)
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Antarctic krill (Euphausia superba) is a key species of Antarctic marine ecosystem and the main fishing object of Antarctic fishery, whose fishing ground has significant temporal and spatial distribution characteristics. In order to clarify the changes of krill fisheries in the northern waters of the Antarctic Peninsula, based on the statistical data of E. superba fisheries in China from 2010 to 2020, this study analyzed the temporal and spatial distribution characteristics of krill fisheries in this water area by using the global Moran's I index and hot spot analysis. The results showed that the spatial distribution of krill catches in the northern waters of the Antarctic Peninsula evolved from dispersion to concentration, and with gradual transition from the north of the South Shetland Islands (SSI) to the Bransfield Strait (BS), with high values distributed along the land. The high value of catch per unit effort (CPUE) mainly occurred in the north of SSI and the side near the Antarctic Peninsula in BS, which was distributed along the land. The krill fisheries in the northern waters of the Antarctic Peninsula showed significant spatial aggregation from 2010 to 2020, and the spatial autocorrelation in 2014, 2015, 2016, 2018 and 2020 was relatively weak. The temporal and spatial evolution characteristics of hot spots and cold spots in the distribution of krill fishing grounds were obvious. The hot spots gradually migrated from the north of SSI to BS, the north of SSI gradually changed from hot spots to cold spots, and the BS gradually changed from cold spots to hot spots. This study discussed the temporal and spatial distribution characteristics of krill fishery, which could not only provide a scientific basis for further research on krill population distribution and fishery formation mechanism, but also provided basic data for improving the production efficiency of krill fishery.
Impact of sea ice and wind field on the suitability of conventional krill fishing operation in the Bransfield Strait, Antarctica
ZHU Yuhang, ZHUO Mengting, ZHU Guoping, DONG Sisong, SHEN Xinyi, ZHANG Chunling, CHENG Lingqiao, HU Song
2022, 46(3): 379-389.   doi: 10.11964/jfc.20211213233
[Abstract](58) [FullText HTML](29) [PDF 3602KB](0)
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Global warming has attracted more and more attention. As the key factors of climate change, Antarctic sea ice and wind field significantly affect the safety and economic efficiency of fishing vessels. Krill fishery is an important part of China's pelagic fishery. China generally uses traditional fishing vessels for krill fishing, which is more vulnerable to the external environment than continuous pumping fishing vessels. The changing environment has a more and more significant impact on Antarctica. However, there has been no regional study on sea ice and wind field in Bransfield Strait. According to the adaptability of krill fishing, based on the sea ice concentration data of the National Snow and Ice Data Center of the United States and the wind field data of the European Centre for Medium-Range Weather Forecasts (ECMWF) from 1989 to 2020, this study obtained the distribution and variation trend of sea ice concentration and wind in the Bransfield Strait, Antarctica within the Subarea 48.1 of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) under climate change. The results show that under the background of global warming, the sea ice and wind speed in Bransfield Strait in Subarea 48.1 showed a decreasing trend, compared with CCAMLR Subarea 48.2, 48.3, and 48.4, Subarea 48.1 was more suitable for krill fishing. According to the distribution of fishing vessels’ operating positions, the fishing operation area was mainly concentrated in central basin (CB) area and eastern basin (EB), and the sea ice concentration was 0.15-0.2 and in areas with large wind force (wind force level reached level 6 and above) for 50-70 days. For the characteristics of sea ice and wind field from 1989 to 2020, the suitable operation days under the influence of sea ice in Bransfield Strait (the days with sea ice density <0.2) increased; the wind direction in this area was mainly to the west, and the number of days with large wind force was less, and the trend was mainly increasing. Due to the low Beaufort scale in the study area, the suitable operation days of traditional fishing boats in the study area were greatly affected by sea ice. Therefore, combined with the changes of sea ice and wind in the Strait in the past 32 years and their impact on traditional fishing operation, our study showed that the suitable operation days of traditional fishing vessels will increase in the future, but the variation in krill resources derived from the change of sea ice and wind needs to be considered in the future study.
Habitat of Antarctic krill (Euphausia superba) in the Bransfield Strait based on ensembled species distribution model
CHEN Xunzi, ZHU Guoping
2022, 46(3): 390-401.   doi: 10.11964/jfc.20211213239
[Abstract](63) [FullText HTML](22) [PDF 3269KB](0)
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Species Distribution Models (SDM) are important tools for exploring future changes in global biodiversity. However, relatively few studies have applied multi-model approaches to assess biogeographic changes globally, especially in marine environments. Antarctic krill (Euphausia superba) is a key species in the Southern Ocean marine ecosystem, but researches on its habitat are still limited, which hampers the understanding of its distribution and resource management. To this end, based on the resource density data of Antarctic krill and five environmental factors including Sea Surface Temperature, Sea Surface Chlorophyll, Sea Surface Height, Net Primary Productivity and Sea Ice Coverage, through ensembled models of 12 algorithms, we analyzed the habitat of Antarctic krill. Our results showed that, of the 8 algorithms, the Support Vector Machines, Random Forests, Multivariate Adaptive Regression Splines, Classification and Regression Trees, Multi-Layer Perceptron, and Recursive Partitioning and Regression Trees consistently outperformed the others; while the Bioclim, Domain, and Maxlike had poor performance, although they also differed among months. Besides, there was a link between inter-annual environmental variability and the spatial and temporal patterns of potential habitat for Antarctic krill. The results showed that the suitable habitat for Antarctic krill is mainly located in the central Bransfield Strait. The prediction of Antarctic krill habitat by ensembled model is helpful for the conservation of Antarctic krill resources, and for the exploration of the best fishing ground for Antarctic krill and the space of important fishing area in the future.
Factors influencing food composition of salp (Salpa thompsoni) in krill fishing ground of the Bransfield Strait, Antarctica
LIAO Danfeng, FANG Qian, ZHU Guoping
2022, 46(3): 402-409.   doi: 10.11964/jfc.20211213242
[Abstract](57) [FullText HTML](28) [PDF 1983KB](0)
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Salpa thompsoni is an important tunica filter feeder in the Southern Ocean, which plays a significant role in the Antarctic marine food web. S. thompsoni and Antarctic krill (Euphausia superba) compete for similar diets. Therefore, in order to study the factor influencing food composition of S. thompsoni in the fishing ground of Antarctic krill fishery, based on the specimens collected from the Bransfield Strait from March to April 2020, this study identified the food composition of this species, and further analyzed the difference in feeding habits between months and life history stages. The results showed that S. thompsoni mainly fed on diatoms and zooplankton, and a small number of ciliates and protozoa. C. pennatum is dominant in the diet of S. thompsoni. Seasonal differences occurred in diet of S. thompsoni. Specifically, the feeding quantity of diatom, i.e., C. pennatum, which is dominant in March, decreased significantly at the end of April. The diet composition of S. thompsoni changed significantly between solitary and aggregating stages. This study is expected to provide a reference for the study of feeding habits of S. thompsoni in the Southern Ocean, and to provide basic information for clarifying the trophic relationship between S. thompsoni and Euphausia superba.
Effects of replacement of fish meal by Antarctic krill meal on growth performance, immune indexes and muscle quality of Pelteobagrus fulvidraco
XIE Kai, SHI Yong, HE Hui, MA Xuekun, LI Zhaolin, ZHONG Lei, WU Tongqiang, ZHANG Junzhi, HU Yi
2022, 46(3): 410-419.   doi: 10.11964/jfc.20211113183
[Abstract](58) [FullText HTML](31) [PDF 1626KB](0)
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An 8-week feeding experiment was conducted to evaluate the effects of replacing fish meal (FM) with krill meal (KM) on the growth performance, serum immune indexes and muscle quality of Pelteobagrus fulvidraco [initial body weight (10.51±0.13) g]. Five experimental diets consisted of different proportions of FM that were replaced with KM, corresponding to dietary inclusion levels of 0% (KM0), 2.5% (KM2.5), 5% (KM5), 7.5% (KM7.5), and 10% (KM10). The results showed that there was no significant difference in growth performance, survival rate, intestinal amylase and lipase activities with the increase of the substitution proportion of krill meal. Compared with KM0 group, trypsin activity in each substitution group decreased significantly. Compared with KM0 group, the content of serum complement 3 in each substitution group increased significantly, and immunoglobulin M in KM5 group increased significantly. When the substitution level exceeded 5%, the activity of serum alkaline phosphatase decreased significantly. With the increase of the substitution ratio of krill meal, the muscle adhesiveness, springiness and gumminess decreased, the cohesiveness increased, and the hardness and chewiness increased first and then decreased. Compared with KM0 group, muscle adhesiveness, springiness and gumminess in KM10 group decreased significantly, and cohesiveness increased significantly. With the increase of the proportion of KM instead of FM, the content of total delicious amino acids and total non-essential amino acids in muscle hydrolyzed amino acids increased first and then decreased. In conclusion, the substitution of KM for FM has no negative effect on the growth performance, which can enhance immune function to a certain extent, and affect the muscle textural parameters and total delicious amino acids in the appropriate ratio.
Astaxanthin content, structure and antioxidant activity in the processing of Antarctic krill (Euphausia superba) meal
OUYANG Jie, ZHAO Xinyuan, MA Tiantian
2022, 46(3): 420-429.   doi: 10.11964/JFC.20220113277
[Abstract](43) [FullText HTML](18) [PDF 2331KB](0)
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Euphausia superba is rich in astaxanthin, which is a good source of natural astaxanthin. Shrimp meal is one of the most important processed products of E. superba. In the shrimp meal processing, the cooking and drying processes involve heat treatment. Astaxanthin is a heat-sensitive substance with poor structural stability, and it is easy to be degraded and isomerized at high temperature, which results in the changes of astaxanthin content and antioxidant capacity. In order to understand the changes of astaxanthin content, structure and antioxidation ability during the processing of E. superba meal, the content and structure of astaxanthin in each stage were determined by high-performance liquid chromatography, the antioxidant activity of astaxanthin in different processing stages was compared, and the correlation between astaxanthin structure and its functional activity was analyzed. The results showed that the content of astaxanthin in E. superba was 110.6 mg/kg, of which the content of all-trans astaxanthin was 90.7% , the content of 13-cis astaxanthin and 9-cis astaxanthin were 4.7% and 4.6% respectively, and after cooking and drying, the content of astaxanthin was 88.7 and 52.1 mg/kg, the proportion of trans astaxanthin was 76.2% and 72.2% , the proportion of 13-cis astaxanthin was 19.9% and 21.9%, and the proportion of 9-cis astaxanthin was 3.9% and 5.9%. The content of three optical isomers such as 3S, 3’S, 3S, 3’R, 3R, 3’R in astaxanthin of E. superba were 16.8, 17.9 and 72.1 mg/kg respectively, the content were 12.0, 25.5 and 55.3 mg/kg after cooking, and were 2.8, 8.1 and 12.4 mg/kg after drying. The scavenging capacity of astaxanthin to DPPH free radical was stronger than Vc. In the scavenging experiment of hydroxyl free radical, the antioxidation ability of astaxanthin after cooking and drying was better than krill material. In FRAP iron reduction experiment, the antioxidation after cooking and drying also showed greater reduction ability. The results showed that the geometric isomerization of astaxanthin mainly took place in the cooking stage, and the optical isomerization mainly took place in the drying stage. This study can provide a theoretical basis and technical reference for the optimization of the processing technology of E. superba meal and the extraction and utilization of astaxanthin.
A method for the determination of astaxanthin ester in Antarctic krill (Euphausia superba) by enzymatic hydrolysis at room temperature
GAO Yan, XING Lihong, SUN Weihong, SUN Xiaojie, ZU Lu, LI Zhaoxin
2022, 46(3): 430-438.   doi: 10.11964/jfc.20211213261
[Abstract](51) [FullText HTML](22) [PDF 2210KB](0)
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It’s difficult for accurate quantification of astaxanthin esters because of their multiple forms, and hydrolysis of astaxanthin esters to free astaxanthin is the key to solve the problem.In this work, Antarctic krill (Euphausia superba) was used as a representative specie for the study of astaxanthins. The mono- and di-esters of astaxanthin were prepared from Antarctic krill by column chromatography, and the composition and content of them were clarified using high-resolution mass spectrometry with ultraviolet detection. The astaxanthin monoesters and the astaxanthin diesters were then taken as the typical research samples, the enzymatic hydrolysis conditions of which were optimized through single factor and orthogonal experiments, and the accuracy and applicability of the method were evaluated. Results showed that: (1) 8 astaxanthin monoesters and 13 astaxanthin diesters were prepared and identified as typical characteristic compounds from krill. (2) For the astaxanthin monoesters, as the substrate concentration was 0.5 μg/mL, the enzyme concentration of the reaction system was 1.14 U/mL, the reaction temperature was 25 °C, and the reaction time was 75 mins, the yield of free astaxanthin could reach (94.56±1.24)%; And for the astaxanthin diesters, as the substrate concentration was 1.0 μg/mL, the enzyme concentration of the reaction system was 0.92 U/mL, the reaction temperature was 25 °C, and the reaction time was 75 minutes, the free astaxanthin yield reached (98.28±0.84)%. (3) Enzymatic hydrolysis at room temperature was applied to the analysis of actual samples, the astaxanthin content was (265.09±20.35) mg/kg in Antarctic krill oil, and the content was (21759.36±90.19) mg/kg in Haematococcus pluvialis. In order to verify the accuracy, the enzymatic hydrolysis method was compared with the standard methods from SC/T 3053—2019 and GB/T 31520—2015. The determination results were 260.42±11.57 mg/kg and 21752.54±100.00 mg/kg respectively, and the deviations of the results were all less than 10%. Then the results were further verified by adding a standard solution of all-trans astaxanthin to the sample matrix was tested, the recovery rate of free astaxanthin was 95.24% in Antarctic krill and 98.56% in Haematococcus pluvialis, RSD was 2.03% and 0.75%, respectively. It proved that the enzymatic hydrolysis method has good accuracy and precision. Studies have shown that the enzymatic hydrolysis method has good stability and high repeatability, reduces the oxidation of astaxanthin in the reaction process, and maximizes the conversion of ester astaxanthin into free form, which is suitable for accurate quantification of esterified astaxanthin. Therefore, the scientific basis for the comprehensive utilization of astaxanthin resources could be provided from this study.
Optimization and application of the method for determination of the fatty acid content in phospholipid from krill oil
WANG Shimiao, YANG Chunyu, ZHAO Qi, LI Jian
2022, 46(3): 439-444.   doi: 10.11964/jfc.20211113202
[Abstract](61) [FullText HTML](27) [PDF 2102KB](0)
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Due to richness in essential amino acids, phospholipids, astaxanthin and omega-3 polyunsaturated fatty acids (PUFAs), Antarctic krill (Euphausia superba) which was abundant and had high nutritional value was considered to have great development value. At present, the analysis of fatty acid contents in Antarctic krill and its products mainly focused on the determination of total fatty acid contents. Owing to the effect of bioavailability for PUFAs in different esters, it was necessary to accurately quantify the content of fatty acid in different types of esters in Antarctic krill and its products. In order to clarify the content of phospholipids (PL) fatty acids in Antarctic krill oil, a gas chromatography analysis method for the content of fatty acids in PL in Antarctic krill oil was established based on solid phase extraction. After optimizing the various conditions of the impact analysis, under the optimal conditions, the recoveries of the standard addition measured by this method were between 84.22%-94.45%, and the intra-day and inter-day precision were between 0.79%-6.09%. This method was applied to measure the changes in the content of various PL fatty acids of Antarctic krill oil during storage. The results showed that the content of PL fatty acids decreased during the 21-day storage process, and the degradation rate increased with increasing temperature. The present study provided methodological support for the study of lipids in Antarctic krill.
Isolation, purification and properties of Antarctic krill (Euphausia superba) major allergens
LIN Na, MA Derong, LIU Zhidong, NI Ling, DUAN Rui, ZHANG Junjie
2022, 46(3): 445-456.   doi: 10.11964/jfc.20211213227
[Abstract](53) [FullText HTML](21) [PDF 4766KB](1)
Abstract:
Antarctic krill (Euphausia superba) is a type of crustacean living in Antarctic waters and is an important strategic marine living resource. Currently, the research on the safety of Antarctic krill is mainly focused on fluorine and arsenic, while the study on Antarctic krill sensitization is rarely reported. How to prevent and control the food allergy caused by Antarctic krill has become urgent work. In order to explore the sensitization problem of Antarctic krill, the main allergens were screened, identified, isolated and purified from Antarctic krill, and the properties of major allergens were studied. Antarctic krill proteins were extracted by salt buffer; Allergens were screened by SDS-PAGE and Western blot (WB); The primary structure of these allergic proteins were identified using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS); Major allergens were separated and purified by isoelectric precipitation, ammonium sulfate salting out and anion exchange column chromatography. The heat resistance and the digestive stability of Antarctic krill major allergens to simulated gastrointestinal fluid were analyzed by SDS-PAGE and WB. Results showed that the protein bands of sarcoplasmic protein (SP) and myofibrillar protein (MF) extracted from Antarctic krill were rich and the range of the molecular weight (MW) was wide. Antarctic krill proteins could react with the serum IgE of shrimps/crabs allergic patients, and at least four proteins had positive reactions. The protein with the strongest immune reaction had a MW of about 35 ku and could be recognized by the serum of all allergic patients. This allergic protein was identified as Antarctic krill tropomyosin (TM) by LC-MS/MS. The optimum saturation of ammonium sulfate was 50% for the salting out Antarctic krill TM. After separation and purification, TM with high purity was obtained, which could have a strong immunoreactivity with the serum IgE of shrimps/crabs allergic patients. The measured isoelectric point of Antarctic krill TM was 4.4, and it had good thermal stability. With the extension of digestion time of simulated gastric fluid (SGF), MW of TM gradually decreased and finally stabilized at about 33 ku, and the abundance of degradation fragments with MW of 15 ku and 12 ku gradually increased and existed stably. These degradation bands could still have strong immunoreactivity with the serum IgE of allergic patients. With the extension of digestion time of simulated intestinal fluid (SIF), the original band of TM gradually decreased until disappeared, and finally completely degraded into smaller polypeptide. The immunoreactivity of TM degradation products was greatly reduced after digestion by SIF. The results obtained above indicate that there are allergens in Antarctic krill, and TM is the main allergen with immunoreactivity. TM also has the general characteristics of allergens, such as high temperature resistance, pepsin digestion resistance and partial stability of trypsin digestion.
Fractional preparation of Antarctic krill oil and its quality analysis
LIU Yunhang, LIN Wei, XU Yafu, LIU Yuxin, ZHOU Dayong, SONG Liang
2022, 46(3): 457-465.   doi: 10.11964/20211113187
[Abstract](72) [FullText HTML](27) [PDF 1662KB](0)
Abstract:
Antarctic krill oil (AKO) refers to the lipid extracted from Euphausia superba. Recently, it has attracted great concerns from academia and industry due to its unique composition. However, the lack of standards, complex composition and differences in processing methods can easily lead to unstable quality of AKO products, which would further limit the in-depth research on its functional properties and restrict the development of the AKO industry. Thus, the fractional preparation of AKO and its quality analysis were conducted in this study. Firstly, the whole E. superba meal was used as the raw material, and soybean oil or medium chain triglycerides was used as the co-solvent carrier in conjunction with supercritical CO2 extraction technology to prepare triglyceride-enriched oil (first grade oil). And then, the extracted E. superba meal was subjected to alcohol extraction to prepare a phospholipid-enriched oil (second grade oil). Considering the lipid composition, and content of phosphatidylcholine and phosphatidylethanolamine as the inspection indicators, 30% soybean oil was selected as the co-solvent carrier in conjunction with supercritical CO2 extraction technology to prepare AKO. The results showed that, compared with the non-cosolvent group and the ethanol cosolvent group, the co-solvent carrier (30% soybean oil) group had the highest extraction rate of primary oil, suggesting the phospholipids of the first and second grade oils were effectively separated, and its polyene index, atherosclerosis index and thrombosis index were relatively low. The phospholipid content of AKO prepared by fractionation in the present study was significantly different, which not only enriched the types of AKO products, but also provided theoretical guidance for the selection and formulation of subsequent AKO extraction technology. It is suggested that the research of AKO in the future should focus on the influence of typical processes on the composition, structure and functional properties of AKO and their related mechanisms, which would be helpful to achieve precise regulation and efficient production of AKO with target functionalities.
Preparation of Antarctic krill Pickering emulsion stabilized by β-cyclodextrin and its stability
ZHU Kai, XU Xuejiao, YANG Huicheng, SHEN Qing, DAI Zhiyuan, ZHENG Zhenxiao
2022, 46(3): 466-474.   doi: 10.11964/jfc.20211213226
[Abstract](59) [FullText HTML](25) [PDF 1848KB](1)
Abstract:
Pickering emulsion is a new type of emulsion system that uses solid particles to achieve the stability. Compared with traditional emulsions, Pickering emulsion has not only the basic characteristics of classic emulsions, but also better stability, higher safety and a wider range of applications. As a result, Pickering emulsion has received widespread attention. However, most researchers used inorganic particles or organic polymers to prepare Pickering emulsions. These particles have shortcomings such as low biocompatibility and poor degradability, which limit their use in the food industry. Therefore, seeking food-grade natural stabilizers has become a development trend. β-cyclodextrin is a cyclic oligosaccharide composed of seven glucose molecules. It has a unique structure of hydrophobic internal and hydrophilic external, and has good emulsifying properties. In the water-oil system, β-cyclodextrin can embed the oil phase in the inner cavity and adsorb the water phase on the outer wall, forming an interfacial film at the oil-water interface in the form of clathrate particles, thereby forming a stable emulsion system. In order to make the Antarctic krill oil Pickering emulsion stabilized by β-cyclodextrin and study its stability, the effects of different emulsification methods (ultrasonic, high-speed shearing, high pressure microfluidics), different oil phase volume fractions (30%, 40%, 50%, 60%, 70%), and different β-cyclodextrin mass fraction (1%, 2%, 3%, 4%, 5%) on the emulsion system (turbidity, centrifugal stability, particle size, ζ-potential) were studied and the preparation process of β-cyclodextrin stabilized Antarctic krill oil Pikering emulsion was determined. Then, the thermal sterilization stability, freeze-thaw stability and storage stability of the emulsion were investigated through the appearance, microscopic changes of the emulsion and the characteristic indexes. The results showed that a stable Antarctic krill oil Pickering emulsion was prepared with 60% oil volume fraction, 3% β-cyclodextrin mass fraction and high-speed shear emulsification. The turbidity, centrifugal stability, particle size and ζ-potential of the emulsion were 1.83, 85.12%, 110.5 nm and -28.39 mV, respectively. Thermal sterilization had no significant effect on the appearance and microstructure of the emulsion, and the characteristic index of the emulsion. Freezing and thawing process had a significant impact on the emulsion. After the freezing and thawing, serious precipitation and emulsification took place in the emulsion, and the emulsion was no longer in a uniform and stable state. After the emulsion was stored for 16 days, although the appearance structure, microstructure and characteristic indexes of the emulsion had changed, the emulsion still showed a uniform and stable state. In short, β-cyclodextrin as a stabilizer could be used to prepare Antarctic krill oil Pickering emulsion, which could have good thermal sterilization and storage stability (within 16 days), but no freeze-thaw stability.
Preparation and antioxidant properties of soluble Antarctic krill protein-rutin complexes
LI Yufeng, WANG Jingjing, TAN Lijun, PENG Zhiyun, ZHAO Cheng, LIU Haiquan, ZHAO Yong
2022, 46(3): 475-485.   doi: 10.11964/jfc.20211113146
[Abstract](69) [FullText HTML](38) [PDF 2402KB](1)
Abstract:
In order to improve the antioxidant activity of Antarctic krill protein, a new polyphenol-protein complex (SAKP-rutin complex) was successfully prepared by grafting rutin onto soluble Antarctic krill proteins (SAKP). The antioxidant capacity of SAKP-rutin complexes was evaluated by measuring its ability to scavenge DPPH- and hydroxyl radicals. Meanwhile, the protective ability of SAKP-rutin complexes against oxidative damage of HepG-2 cells was determined by using an H2O2 induced oxidative damage model. The results showed that the combination of rutin greatly enhanced the ability of SAKP to scavenge free radicals. Compared with natural SAKP, the SAKP-rutin complexes significantly increased the activity of cellular antioxidant enzymes (CAT, SOD and GSH-Px), decreased the production of lipid peroxidation products (MDA) in cells caused by oxidative stress, and finally reduced the damage of oxidative stress to cells. These findings suggest that SAKP-rutin complex is a novel protein resource which will hopefully be applied to developing functional protein food.
Key technology of the proportioning process of Euphausia superba and seawater in Euphausia superba deshelling processing in a standardized shipborne processing mode
NI Jin, TAN Jiayu, ZHENG Xiaowei, SHEN Jian
2022, 46(3): 486-493.   doi: 10.11964/jfc.20211213235
[Abstract](55) [FullText HTML](26) [PDF 2080KB](1)
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In order to meet the needs of Antarctic resource development, in order to solve the problems of the disorderly development of the deshelling processing mode in the current shipborne processing of Euphausia superba, and the lack of key technology for proportioning process of E. superba and seawater, which results in poor operation stability of the deshelling processing equipment, in this study, according to industrial development needs of E. superba processing and E. superba deshelling production line on a domestic E. superba professional fishing and processing ship, a standardized processing mode has been established by using mechanism analysis method. Using mechanism analysis method, the law of conservation of mass, Dixon's criterion and data fusion filtering algorithm, etc., the data processing method of the acquisition signal of the feeding system in E. superba deshelling process , the mathematical model of the feeding system’s dynamic proportioning process of E. superba and seawater, the control model and workflow of E. superba to seawater were established, and using the E. superba deshelling processing equipment on a domestic E. superba professional fishing and processing ship, the research on the application effect of the key technology of proportioning process of E. superba and seawater was carried out. The results showed that based on the process parameters set in the experiment, the value of proportioning process of E. superba and seawater fluctuated around the preset value, and the maximum change was controlled within ±2%. Among them, in the starting state, the regulation time of seawater flow and E. superba’s mass rate was about 119 seconds, and both can operate stably according to the preset parameters. In the running state, the regulation time of seawater flow and E. superba’ s mass rate was about 32 seconds, and then it showed periodic and stable changes with the change of liquid level. The deviation of seawater flow rate was –0.48 to 0.42 m3/h, and the deviation of shrimp mass rate is –0.48 to 0.42 m3/h., meat yield increased by 0.7%. The results indicated that the key technology of proportioning process of E. superba and seawater for E. superba deshelling processing in the standardized shipborne processing mode of this study can ensure the stable value of proportioning process of E. superba and seawater. The maximum change of the proportioning process of E. superba and seawater in this research was controlled within ±2%, meat yield increased by 0.7%. This technology can ensure the stable operation of proportioning process of E. superba and seawater deshelling processing, and meet the needs of E. superba deshelling process development.
Effect analysis of gear structure and sinker on the performance of Antarctic krill beam trawl
FENG Chao, LI Lingzhi, ZHANG Gangchen, LIU Jian, YANG Jialiang, RAO Xin, HUANG Hongliang
2022, 46(3): 494-504.   doi: 10.11964/jfc.20211013111
[Abstract](49) [FullText HTML](26) [PDF 2526KB](0)
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Beam trawl is an important part of Antarctic krll (Euphausia superba) continuous fishing system. In order to further understanding the gear performance under different conditions, a series of model test were designed to study the effect of gear structure and sinker on gear performance. The gear structures include 3 kinds of belly width and 2 types of knitting for each belly width, represented by A, B, C, AA, BB and CC respectively. Modified Tauti’s law was used to designed beam trawl models. The full scale was 20, mesh size or twine diameter scale was 10. Based on the energy efficiency coefficient, vertical opening and resistance, the performance of different gear structure were compared. The result showed that: the performance of different gear structure was in the order of BB>CC>C>A>B> AA, but the difference was not obvious (P>0.05). Less total line area of net can effectively improve the vertical opening of the beam trawl and reduce the energy efficiency coefficient, especially under the high trawling speed. Sinker weight was significantly correlate with gear resistance and vertical opening, and not significantly correlate with energy efficiency coefficient. In order to keep good performance in vertical opening of test nets, heavier sinker were needed under higher trawling speed. According to the model test, sinker weight should not be less than 3.05 t at the trawling speed of 1.5 m/s for test nets; a power function was observed between net resistance and trawling speed, and the index ranged from 1.49 to 1.64. These conclusions can be used as reference for the performance optimization of E. superba beam trawl and promote the development of E. superba fishery.
Effect of vessel speed on the effective range detection limit of scientific echo sounder onboard an Antarctic krill (Euphausia superba) fishing vessel
WANG Xinliang, YU Xiaotao, ZHANG Jichang, LI Xiansen, ZHAO Xianyong
2022, 46(3): 505-512.   doi: 10.11964/jfc.20211013116
[Abstract](58) [FullText HTML](28) [PDF 2168KB](0)
Abstract:
Recently the fishing vessel has been widely used to collect acoustic data to provide information on the distribution and abundance of Antarctic krill (Euphausia superba). One basic assumption of the acoustic survey is that the effective range detection limit (RDL) of the echo sounder could cover the major distribution layer of Antarctic krill. However, due to the lack of noise mitigation design, the background noise levels of fishing vessel are usually higher than the research vessels, which may seriously degrade the RDL of the echo sounder system. In order to facilitate the use of fishing-vessel-based acoustic data, in the present study, a method was introduced to estimate the RDL of scientific echo sounder based on the background noise estimates obtained using post-processing technique. Furthermore, taking the Antarctic krill fishing vessel “Fu Rong Hai” as a case study, the background noise levels and RDLs of the Simrad EK 60 echo sounder system (38, 70 and 120 kHz) onboard were estimated at various vessel speeds. Results indicated that the RDL was not only related to echo sounder specifications and backscattering strength of the survey target, but also to the background noise level and the vessel speed. For “Fu Rong Hai”, the background noise levels of the acoustic data collected by the EK60 system increased markedly with increasing vessel speed and resulted in decreased RDLs for all the three frequencies. At a vessel speed of 8 kn and a signal-to-noise ratio (SNR) of 10 dB, the RDLs for all the three frequencies were estimated to be larger than 300 m for the Antarctic krill with a Sv threshold of −70 dB , while the RDL decreased to be around 100 m at 70 kHz which could not meet the requirement of depth coverage (250 m) for Antarctic krill acoustic survey when the vessel speed was increased to 12 kn. The results proved that the vessel speed may have significant impact on the performance of effective range detection limit of echo sounder system, and this study may provide valuable reference for the use of fishing vessels to conduct acoustic survey particularly the vessel speed and data processing.
On the role and function of non-governmental organizations in Antarctic governance from the perspectives of Antarctic marine protected areas and Antarctic krill fishery
WEI Xiangyun, ZHU Guoping
2022, 46(3): 513-523.   doi: 10.11964/jfc.20211213241
[Abstract](59) [FullText HTML](25) [PDF 2106KB](0)
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Since the promotion of Antarctic governance, particularly the establishment of Antarctic Marine Protection Areas (AMPAs), involves diverse factors, the roles and functioning of parties are differed in those processes. Non-governmental organizations (NGOs), as multiple actors in Antarctic governance, have significant effected on the promotion of AMPAs with their ability in providing scientific data, active participation and public attention. The role of NGOs in Antarctic governance has influenced, to some extent, the promotion of AMPAs and the effective management of Antarctic krill fishery. By analyzing the works of four NGOs, including the Antarctic and Southern Ocean Coalition (ASOC), the Association of Responsible Krill Harvesting Companies (ARK), the Pew Charitable Trusts (PEW) and the Oceanites, to explore their roles in the promotion of AMPAs and Antarctic krill fishery management. At present, China can enrich China Antarctic scientific research database by using multi-party data, use NGOs to tell China's stories within its legal framework. The government and NGOs interact to form a virtuous cycle to improve the scientific nature of AMPAs research and Antarctic krill fishery management, thus improving the overall level of Antarctic governance and contributing China wisdom to the protection of the Antarctic ecological environment.

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