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Effect of trehalose on sperm cryopreservation of Acipenser schrenckii and preliminary study on the mechanism of its cryoinjury 2023, 45(1): 1.  Abstract ( 175 )   PDF (2633KB) ( 471 )   Effect of trehalose on sperm cryopreservation  of Acipenser schrenckii and preliminary study  on the mechanism of its cryoinjury CHEN Zhangfan2,3, CHENG Peng2, HU Mou4, WANG Jie2,5,  ZHANG Tingting2,5, HUANG Hongtao1, DU Hejun1, CHEN Songlin2,3 (1. Hubei Key Laboratory of Three Gorges Project for Conservation of Fishes, Chinese Sturgeon Research Institute, China  Three Gorges Corporation, Yichang Hubei443100, China; 2. Laboratory for Marine Science and Food Production  Processes, Qingdao National Laboratory for Marine Fisheries Science and Technology,Yellow Sea Fisheries Research  Institute, Chinese Academy of Fishery Sciences (CAFS),  Qingdao Shandong266237, China; 3. Shandong Key  Laboratory of Marine Fisheries Biotechnology and Genetic Breeding, Qingdao Shandong266071, China; 4. Hangzhou  iandaohu Xunlong Scitech Co., Ltd., Hangzhou311701, China; 5. College of Fisheries and Life Science, Shanghai  Ocean University, Shanghai201306, China) Abstract: Cryopreservation is of importance for the genetic improvement of resources, conservation of species diversity, and breeding of improved varieties in aquaculture industry. The techniques of sperm cryopreservation have been established and optimized in numerous kinds of sturgeons; however, the motility, fast movement, and durations of frozenthawed semen were significantly lower than those of fresh semen.  In this study, we added various concentrations of trehalose or sucrose as cryoprotectants in the extender for sperm cryopreservation of Acipenser schrenckii and evaluated the motility, fast movement, and duration of the treated groups and the control group (fresh sperm). The extender diluted with 10% MeOH was mixed with sperm at a ratio of 1∶2 for sperm cryopreservation.The diluted semen was dispensed into 2 mL cryovials, placed into cloth bags, suspended 15 cm above nitrogen vapor for 10 min, then 5 cm above nitrogen vapor for 5 min, and finally stored in liquid nitrogen. After thawing at 37 ℃, the motility, fast movement and durations of frozenthawed semen was observed and recorded under the microscope, compared with fresh semen.  Results showed that ST5 solution (1 mM NaCl, 20 mM Tris, 60 mM trehalose, pH 8.0) worked most effectively during sperm cryopreservation of A. schrenckii. The motility of frozenthawed spermatozoa was(26.67±3.32)%, significantly lower than that of fresh spermatozoa. The fast movement of fresh spermatozoa could last (93.17 ± 4.34) s, while frozenthawed spermatozoa could last (75.63 ± 6.05) s. The duration of fresh spermatozoa ［(246.61 ± 2.29) s］ had no significant difference with frozenthawed spermatozoa ［(239.35 ± 1.49) s］. To explore the mechanisms of cryoinjury in A. schrenckii semen, we fixed the fresh and frozenthawed spermatozoa with 2.5% glutaraldehyde and observed their ultrastructure by using transmission electron microscope (TEM) and scanning electron microscope (SEM). Meanwhile, enzyme activities were compared between fresh and frozenthawed sperm. Results showed that mature spermatozoa were comprised of acrosome, head, midpiece and flagellum. The length of acrosome, head, midpiece was (0.71 ± 0.08) μm, (0.71 ± 0.08) μm, and (0.87 ± 0.31) μm. The width of acrosome, head, midpiece was (0.76 ± 0.06) μm, (0.71 ± 0.08) μm, and (0.73 ± 0.16) μm. It had an obvious acrosome, which was also observed in other sturgeon species. The mitochondria was located in midpiece for the energy supplement during tail movement. Flagellum was composed of central fibers and peripheral fibers, which formed a typical “9+2” structure of axoneme. Cryopreservation caused the disruption of membrane and organelles, including the disruption of plasmalemma, nuclear membrane, cristae of mitochondria and flagellum membrane, acrosome damage, swelling midpiece, cytoplasmic dispersion, and mitochondria and flagellar fracture. The activities of enzymes involved in energy metabolism, containing total adenosine triphosphatase (total ATPase), creatine kinase (CK), succinate dehydrogenase (SDH), and lactate dehydrogenase (LDH), were measured in A. schrenckii sperm before and after cryopreservation. Results showed that the activities of all four enzymes in spermatozoa significantly dropped (P<0.05). The activities of total ATPase, CK, SDH, LDH in spermatozoa in cryoprotectant group decreased from (7.45±1.98) U·mL-1, (4.98 ± 0.97) U·mL-1, (14.50 ± 2.12) U·mL-1, and (10 850.11±184.82) U·L-1 to (2.33±0.20) U·mL-1, (2.13±0.83) U·mL-1, (3.38±1.04) U·mL-1, and (5 588.09±75.35) U·L-1. At the same time, the activities of enzymes in spermatozoa without cryoprotectant dropped to (0.70 ± 0.02) U·mL-1, (2.72 ± 0.39) U·mL-1, (2.83 ± 1.52) U·mL-1, and (4 030.20±1 093.12) U·L-1. The activities of total ATPase and CK in seminal plasma significantly increased(P<0.05), while the activities of SDH and LDH increased but without significant differences. The activities of total ATPase, CK, SDH, LDH in seminal plasma in cryoprotectant group increased from (0.76 ± 0.05) U·mL-1, (0.33 ± 0.14) U·mL-1, (1.56±0.31) U·mL-1, and (5 469.80±131.19) U·L-1 to (3.85 ± 1.62) U·mL-1, (1.56±0.18) U·mL-1, (4.33±2.17) U·mL-1, and (5 618.09±216.88) U·L-1. Meanwhile, the activities of enzymes in seminal plasma without cryoprotectant dropped to (4.60±1.46) U·mL-1, (3.59±0.51) U·mL-1, (29.30±5.88) U·mL-1, and (9 133.11±1 023.54)U·L-1.  In addition, the antioxidant activities containing catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSHPX), and glutathione reductase (GR) were measured in A. schrenckii sperm before and after cryopreservation. Results showed that GR activity in spermatozoa significantly increased while the activities of the other three antioxidants significantly dropped (P<0.05). The activities of total CAT, SOD, GSHPX, GR in spermatozoa in cryoprotectant group changed from (20.94 ± 0.48) U·mL-1, (129.91 ± 2.77) U·mL-1, (52.35 ± 13.03) U·mL-1, and (38.32 ± 17.71) U·L-1 to (4.96 ± 0.72) U·mL-1, (94.59 ± 5.49) U·mL-1, (13.39 ± 7.12) U·mL-1, and (132.44 ± 17.90) U·L-1. At the same time, the activities of enzymes in spermatozoa without cryoprotectant changed to (0.65 ± 0.27) U·mL-1, (78.77 ± 4.90) U·mL-1, (6.14 ± 4.21) U·mL-1, and (166.801 ± 41.39) U·L-1. The activities of CAT and GR in seminal plasma significantly changed (P<0.05), while the activities of GSHPX and SOD increased but without significant differences. The activities of total CAT, SOD, GSHPX, GR in seminal plasma in cryoprotectant group increased from (0.51 ± 0.34) U·mL-1, (94.74 ± 2.37) U·mL-1, (4.22±1.84) U·mL-1, and (161.58 ± 37.57) U·L-1 to (1.84 ± 0.35) U·mL-1, (96.28±2.69) U·mL-1, (10.89±3.41) U·mL-1, and (86.01±7.90) U·L-1. Meanwhile, the activities of enzymes in seminal plasma without cryoprotectant dropped to (17.09 ± 1.70) U·mL-1, (124.10±1.65) U·mL-1, (45.01 ± 7.19) U·mL-1, and (2.01 ± 1.39) U·L-1.  The activities of enzymes including total ATPase, CK, SDH, LDH, CAT, SOD, GSHPX) significantly decreased in frozenthawed spermatozoa (P<0.05), while GR activity significantly increased (P<0.05). These results indicated the damages in psychological functions, intracellular environment, antioxidative system, and energy supplement, which might affect the motility of A. schrenckii spermatozoa.  Compared with the group supplemented with cryoprotectants, the activities of total ATPase, CK, CAT, SOD and GR in the group without cryoprotectants were significantly changed (P<0.05), suggesting the effective protection of trehalose in cryoprotectants on frozenthawed sperm. The observation of spermatic ultrastructure damage and variations of antioxidants and enzymes involved in energy metabolism in frozenthawed spermatozoa could be used to evaluate the quality of fish semen. Furthermore, the results of this study would provide a theoretic basis for the parametric optimization to improve the quality of frozenthawed sperms, and shed some light on the exploration on mechanism of cryoinjury in fish spermatozoa. Keywords: Acipenser schrenckii; spermatozoa; cryopreservation; trehalose; cyroinjury Related Articles | Metrics

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Cloning and expression analysis of HMIT gene in Litopenaeus vannamei 2023, 45(1): 14.  Abstract ( 161 )   PDF (4847KB) ( 495 )   Cloning and expression analysis of HMIT  gene in Litopenaeus vannamei LIU Hongtao, YANG Mingqiu, WANG Kun, HE Yugui (Hainan Provincial Key Laboratory of Tropical Maricultural Technologies,  Hainan Academy of Ocean and Fisheries Sciences, Haikou571126, China) Abstract: The H+/myoinositol transporter (HMIT) gene, also known as solute carrier family 2 member 13 (SLC2A13) or GLUT13, is the only H+coupled transporter in the glucose transporter family. However, it does not transport glucose, but H+ coupling specifically transmembrane transports inositol. It is observed that the addition of moderate amount of inositol can improve the growth performance, nonspecific immune enzyme activity, and antioxidant capacity of Litopenaeus vannamei. Inositol is involved in glucose and lipid metabolism, osmotic pressure regulation, signal transduction, and other physiological processes in living organisms, but its absorption and transport mechanisms are largely unknown. In this study, we obtained the full sequence of HMIT gene from the hepatopancreas of L. vannamei by RACE and performed bioinformatics analysis. We used realtime fluorescence quantitative PCR to determine the distribution of HMIT expression in eight tissues, including blood cells, eye stalk, gills, heart, intestine, stomach, hepatopancreas and muscle. We also determined the expression changes of HMIT gene in each early larval developmental stage of L. vannamei, including nauplius, zoea, mysis, postlarvae, and the expression changes of HMIT in hepatopancreas and gills of L. vannamei  injected with 100 μL of decapod iridescent virus 1 (DIV1) suspension (the infection dose was about 104 viruses per g of shrimp body weight for 24 h）. The results showed that an HMIT gene was cloned from L. vannamei named LvHMIT, it was also the first report of HMIT gene in crustaceans. The open reading frame of LvHMIT was 1 650 bp in length, encoding 549 amino acids, its’ predicted molecular mass was 58 972.42 Da and the theoretical isoelectric point was 5.57. Analysis of physical properties demonstrated that LvHMIT was an unstable hydrophilic protein. A total of 70 phosphorylation sites, 2 O glycosylation sites, and 1 Nglycosylation site were predicted, some of which might affect the structure of the protein and the realization of functions such as plasma membrane localization. The absence of a typical signal peptide at the Nterminal end of LvHMIT protein was predicted. The predicted secondary and tertiary structures of LvHMIT showed that it was mainly composed of many αhelix and random coils(αhelix 43.72%; βturning 5.83%; extended chain 17.49%, and random coil 32.97%). Transmembrane structural analysis revealed the presence of 11 transmembrane helix structures in LvHMIT. The TM7 transmembrane fragment in most HMIT proteins was missing, but the secondary structure prediction at this position revealed that an αhelix that did not meet the transmembrane requirement was still present. In addition, the transmembrane helix length and the distribution of specific amino acids on the helix differed greatly between species, showing the specificity of HMIT genes in different species. Noteworthy, the predicted extracellular amino terminus of LvHMIT and intracellular carboxyl terminus, together with the absence of the above transmembrane fragment, resulted in a change in the loop structure formed between TM6 and TM7 transmembrane structures of LvHMIT (equivalent to that between TM6 and TM8 of glucose transporter proteins) from an intracellular loop to an extracellular loop, showing a difference from the typical HMIT protein structure. The predicted subcellular localization of the LvHMIT protein showed that it was mainly distributed in plasma membrane, endoplasmic reticulum, and mitochondria with percentages of 60.9%, 34.8%, and 4.3%, respectively. A typical MFS_HMIT_like domain was predicted from amino acid residue 22 to 521 in LvHMIT. Multiple sequence alignment revealed that the transmembrane structure and its arrangement in LvHMIT were relatively conserved, as well as the cysteine and glycosylation sites on the extracellular loop, including eight cysteine and CGFC motifs on the extracellular loop and the Nglycosylation site at position 410. The amino acid sequence of LvHMIT showed the highest similarity with the HMIT of Chionoecetes opilio at 69.42%. The phylogenetic tree illustrated that LvHMIT first clustered with the HMIT proteins of arthropods such as C. opilio and Hyalella azteca, and branched off from vertebrates, echinoderms, and mollusks. The tissue expression and functions performed by HMIT varied widely among species. The results of the expression distribution of LvHMIT gene in eight types of tissues using qRTPCR showed that it was most highly expressed in hepatopancreas, followed by gills, and a few expressions in heart, stomach, eyestalk, intestine, muscle and blood cells. The hepatopancreas was an important digestive and immune organ of shrimp, involved in various biological processes such as glucose metabolism and innate immunity, and gill was an important osmoregulatory organ of shrimp, equivalent to the kidney of higher animals. Therefore, LvHMIT might be involved in the biological functions of energy metabolism, immunity and osmoregulation in shrimp. Prawn larval development was metamorphic development, and it had a series of morphologically diverse larval stages, its morphology, structure, behavior, metabolism, and food habits varied with molting and metamorphosis. The result of the expression of LvHMIT in different early larval development stages of L. vannamei showed that its expression could be detected at nauplius, and was upregulated when it metamorphosed to zoea, mysis, and postlarvae, and then it was back down in the middle and late stages of zoea, mysis, and postlarvae, suggesting that it might be associated with the larval development process to some extent. DIV1 has now become a new farming disease for cultured shrimps, including Fenneropenaeus chinensis, Exopalaemon carinicauda, and Macrobrachium rosenbergii, in coastal areas of China and Thailand. The results of the expression changes of LvHMIT in hepatopancreas and gills at 24 h after the artificial infection with DIV1 showed that it was significantly downregulated (P<0.01) in hepatopancreas and upregulated (P<0.01) in gills, indicating that it was involved in the immune response process of shrimp to the virus. Inositol enhances shrimp immunity, and the response of shrimp to DIV1 infection involves inositol phosphate signaling pathways, as metabolism and glycolysis/gluconeogenesis are associated with inositol. In addition, many studies have demonstrated the involvement of HMIT genes in the regulation of phosphatidylinositol signaling pathway. In summary, this study is important for the indepth study of the structural function of HMIT gene and its role in energy metabolism, osmoregulation, larval development, and virus immunity in shrimp. Keywords: Litopenaeus vannamei; HMIT; tissue expression; developmental expression; decapod iridescent virus 1 Related Articles | Metrics

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Stock assessment and sensitivity analysis of Scomber japonicus in the Northwest Pacific Ocean using Catch-MSY method 2023, 45(1): 26.  Abstract ( 163 )   PDF (4224KB) ( 459 )   Stock assessment and sensitivity analysis of Scomber japonicus in  the Northwest Pacific Ocean using Catch-MSY method SHI Yongchuang1,2, CHEN Yunyun3, FAN Wei1,2,  WU Yumei1,2, ZHAO Guoqing1, YANG Chao1 (1. Key Laboratory of Fisheries Remote Sensing, Ministry of Agriculture and Rural Affairs, East China Sea Fisheries  Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China; 2. Key and Open Laboratory of  Remote Sensing Information Technology in Fishing Resource, East China Sea Fisheries Research Institute, Chinese  Academy of Fishery Science, Shanghai200090, China; 3. China Aquatic Products Zhoushan Marine Fisheries  Corporation, Zhoushan Zhejiang316101, China) Abstract: Chub mackerel Scomber japonicus is an important economic and small pelagic species in the Northwest Pacific Ocean. Japanese fisheries initially exploited Scomber japonicus species in this area, and in recent years, the major countries harvesting this species include Japan, China, Russia and Korea. The annual catch of Scomber japonicus recorded in 2019 was about 64 364 tons in China, which accounted for 14.00% of the global production. With the global development of Scomber japonicus fisheries, the number of fishing vessels has been increasing, coupled with the impact of marine environment and climate change, Scomber japonicus resources fluctuate, and fishing production has undergone annual changes. Meanwhile, Scomber japonicus fishery is a typical datalimited fishery in the Northwest Pacific Ocean. It has the biological characteristics of a short life cycle and a long migration route, and the population is extremely sensitive to largescale climatic events and regional environmental changes in the Northwest Pacific Ocean. In 2015, Scomber japonicus has been listed among the priority fish species by North Pacific Fisheries Commission (NPFC). Accurate understanding of its stock status can provide strong guarantee for fishery management and sustainable development. The major global fisheries have been in datapoor/limit condition and the conventional stock assessments are available for stock based on accurate biological and catch data. As attaining high quality fishery statistics in a short period of time can be challenging, regional fisheries management organizations have determined that the datapoor approach is an appropriate research direction for the stock assessment of datalimited fisheries. CatchMSY method can temporarily replace conventional stock assessment models in making management decisions for a datalimited fishery, even when only catch data are available. Further, CatchMSY method requires less data compared to other methods. Consequently, this model may be a good choice for the MSY estimation of Scomber japonicus. CatchMSY model was used in this study to estimate MSY and stock status on the basis of catch data and life history information from the NPFC. CatchMSY model was based on the Schaefer production model, which was developed to calculate annual biomass, and the ranges of the initial and current depletion levels should be specified in CatchMSY model. In this study, we derived default ranges of relative biomass in the first and last years of the time series. For the first year, if the ratio of catch to the maximum catch was below 0.5, the range of B/K(γ1, γ2) was 0.50.9; otherwise, the range of B/K was 0.30.6. For the final year, the range of B/K(γ3, γ4) was 0.010.4 if the ratio of catch to maximum catch was below 0.5; otherwise, it was 0.30.7. What’s more, during the process, 16 scenarios, according to different prior distributions of the intrinsic rate of increase (r) and carrying capacity (K), were set for sensitivity analysis. Moreover, the influence of different catch time series and different process errors were taken into account. The results showed the following: 1) In standard scenario S1A, the estimated MSY of Scomber japonicus was 49.57×104 t (39.55×104 t to 60.58×104 t) and the value was 49.59×104 t (39.58×104 t to 60.62×104 t) in standard scenario S1B; 2) Compared with parameter r, K had a relatively narrow posterior distribution, lnK decreased gradually with the increase of ln r, and the value of MSY was positively correlated with the lower limit of r prior distribution; 3) When using the noninformative priors of parameter r, the posterior distribution of K had a broader range than using informative priors of r. When using the informative priors of parameter r, the lower limit r, the larger mean value of the posterior distribution of K, and the broader distribution of K values were used to maintain those yields. There was no significant difference of the posterior distribution of r when using noninformative priors and informative priors of K. 4) For r, the MSY increased gradually with an increasing lower limit of the prior distribution of r. The MSY was more discrete when the wider range prior distribution of r was given. For K, the upper limit of K only slightly influenced the distribution of MSY. There was a little fluctuation of MSY depending on the dataset, which meant that the time series of catch data had a limited impact on the estimation of MSY, whereas the results of the model were sensitive to the annual catch in the first and last years. The MSY value was sensitive to the time series of catch data, but its impact on the estimation of stock status was limited. 5) Given the uncertainty of the CatchMSY model, maintaining a management target between 50×104 t and 60×104 t was a better management regulation. This study shows that the CatchMSY model is a useful choice for estimating the MSY of datalimited species such as Scomber japonicus. Additionally, more types of fishery data of Scomber japonicus should be collected in future studies; subsequently, stock assessments of Scomber japonicus can be conducted using traditional stock assessment models, which may provide more reasonable suggestions for the development and management of Scomber japonicus. Keywords: CatchMSY model; Scomber japonicas; sensitivity analysis; stock assessment; Northwest Pacific Ocea Related Articles | Metrics

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On habitat changes of Cololabis saira based on carbon and nitrogen stable isotopes technology 2023, 45(1): 39.  Abstract ( 141 )   PDF (1362KB) ( 415 )   On habitat changes of Cololabis saira based on  carbon and nitrogen stable isotopes technology LIANG Jiawei1, HUA Chuanxiang1,3,4,5,6, CHEN Xinjun1,3,4,5,6, YANG Na1,  ZHAO Zhenfang1, HU Guanyu1,2,3,4,5,6, LI Jinhui1 (1. College of Marine Sciences, Shanghai Ocean University, Shanghai201306, China; 2.School of Ocean and  Earth Science, Tongji University, Shanghai200092; 3. Key Laboratory of Sustainable Exploitation of Oceanic  Fisheries Resources, Ministry of Education, Shanghai Ocean University, Shanghai201306, China; 4. National  Engineering Research Center for Oceanic Fisheries, Shanghai Ocean University, Shanghai201306, China;  5. Key Laboratory of Ocean Fisheries Exploitation, Ministry of Agriculture and Rural Affairs, Shanghai201306,  China; 6. Scientific Observing and Experimental Station of Oceanic Fishery Resources, Ministry of Agriculture  and Rural Affairs, Shanghai201306, China) Abstract: Cololabis saira is a highly migratory pelagic coldwater fish. It is a key species in the ecosystem and one of the important fishing targets in the Pacific Ocean. According to Cololabis saira samples collected in open seas of the Northwest Pacific Ocean near 40°28′N48°56′N, 150°08′E164°20′E by the Cololabis saury fishing boat “Lu Peng Yuanyu 027” from July to November 2018, 127 muscle tissues were taken for stable isotope determination, and δ13C (carbon stable isotope ratio) and δ15N (nitrogen stable isotope ratio) of the muscle were analyzed, and the growth process of δ13C and δ15N was discussed. The range of δ13C in muscle of Cololabis saira was between -23.58% and -20.69 ‰, the average was (-21.71±0.69) ‰, the range of δ15N in muscle of Cololabis saira was between 6.49% and 11.11 ‰, the average was (8.51±1.00)‰. Compared with previous results, it was found that δ13C and δ15N values of Cololabis saira in this study were lower than those of previous studies, which might be because the latitude and offshore distance of the sea area where Cololabis saira were located were quite different, leading to differences in the baseline values of δ13C and δ15N, and thus the differences in δ13C and δ15N of Cololabis saira muscles at different sampling points. Analysis of variance (ANOVA) showed that there was no significant difference between male and female saury in δ13C and δ15N (P>0.05). There were significant differences among different body lengths in δ13C and δ15N (P<0.05). The range of body length of Cololabis saira was between 244 mm and 307 mm, the average value of body length was (281±13) mm. In combination with the relationship between body length and age of Cololabis saira , it could be found that the age range of Cololabis saira samples in this study was between 385 d and 473 d, so it could be considered that samples in this study were mainly  1 year old. The changes of δ13C and δ15N between different body length groups were relatively similar, and showed a trend of increasing first and then stabilizing. In 240260 mm, 260280 mm and 280300 mm body length groups, δ13C and δ15N increased with the increase of body length. These results indicated that δ13C increased gradually during individual growth, and the trophic level also increased. The δ13C of marine phytoplankton decrease from equatorial to two poles (low latitude to high latitude). Therefore, 1yearold saury may migrate from north to south near the Oyashio waters along with individual growth and habitat changes. In the range of body length from 280300 mm to >300 mm, δ13C and δ15N almost remained unchanged, and a plateau appeared. For adjacent body length groups, the same δ13C value meant that the primary productivity level (δ13C value of baseline phytoplankton) was similar, and the same δ15N value meant that the trophic level was similar. Therefore, it could be inferred that the body length of Cololabis saira was 280307 mm and they inhabited the same sea area without longdistance migration. To sum up, the results indicated that 1yearold saury inhabited the Oyashio waters, and then migrated south to the KuroshioOyashio mixed waters. Based on the collinearity test results of the prediction variables, a model of fifteen different variable combinations was established for four prediction variables, and the model with the minimum AIC value was selected as the best fitting model. The best fitting model of δ13C was BL+Lat+DSB+chla, and these variables had significant effect on the δ13C of muscle of Cololabis saira (P<0.05), deviation explanation rate of the model was 56.8%. The best fitting model of δ15N was Lat+DSB, and these variables had significant effect on the δ15N of muscle of Cololabis saira (P < 0.05), deviation explanation rate of the model was 45.8%. Based on the generalized additive model (GAM), the relationship between δ13C, δ15N and latitude, body length, distance from shore, and chlorophyll was established respectively based on the generalized additive model (GAM). The variation trend of δ13C and δ15N values with explanatory variables was significant. Based on the results of GAM models, δ13C was negatively correlated with latitude, it increased slightly in the range between 40° and 42°N, but decreased significantly in the range between 42° and 48°N. This was mainly because isotopic fractionation was one of the factors affecting the variation of δ13C, and fractionation existed in high latitude sea area, resulting in low δ13C value. δ13C was positively correlated with body length. It could be considered that Cololabis saira at this stage migrated and inhabited in different sea areas during their growth. To sum up, we inferred that 1yearold saury in the Oyashio waters migrated southward from high latitude to low latitude with the growth of individual. δ13C first decreased and then increased with the increase of the distance from the shore, a minimum occured at the nearshore distance of 800 km. This might be because the nutrients brought by the Oyashio extension current and other sea currents improved the primary productivity of the sea area, resulting in a higher δ13C level of baseline organisms, which had a positive effect on the δ13C value of Cololabis saira. The variation trend of δ13C with chlorophyll was complex. The δ13C had a positive correlation among 00.5 mg·m3 and among 1.52.5 mg·m3, and a negative correlation among 0.51.5 mg·m3. These results indicate that the δ13C value of baseline organisms is not only related to chlorophyll content, but also may be caused by low sea surface temperature, low inorganic nutrient content or “iron” restriction; δ15N is negatively correlated with latitude; δ15N decreases first, then slowly increases, and then continues to decrease with the increase of the nearshore distance.The variation of δ15N in latitude and offshore distance indicates that 1yearold saury migrates highly and inhibits different sea areas. Keywords: Cololabis saury; habitat; δ13C；δ15N; GAM Related Articles | Metrics

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Feeding ecology of Thunnus obesus in the tropical Western and Central Pacific Ocean 2023, 45(1): 49.  Abstract ( 183 )   PDF (2320KB) ( 466 )   Feeding ecology of Thunnus obesus in  the tropical Western and Central Pacific Ocean SHI Xiaofei1, WU Xiaoci1, WANG Yixi1, WANG Xiao4, SHI Jiangao5, ZHANG Jian1,2,3 (1. College of Marine Sciences, Shanghai Ocean University, Shanghai201306, China; 2. National Engineering  Research Centre for Oceanic Fisheries, Shanghai Ocean University, Shanghai201306, China; 3. Key Laboratory  of Sustainable Exploitation of Oceanic Fisheries Resources, Ministry of Education, Shanghai Ocean University,  Shanghai201306, China; 4. Shanghai Kai Chuang Deep Sea Fisheries Co. Ltd., Shanghai200082, China; 5. East  China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China;) Abstract: Bigeye tuna Thunnus obesus, widely distributed in the tropical and subtropical waters of the Atlantic, Indian and Pacific oceans, is one of major targets of tuna longline fisheries of almost all countries. The Western and Central Pacific Ocean (WCPO) is the largest tuna fishing area in the world. Global climate change aggravates series of changes in the physical and chemical environment and marine ecosystems, as well as alters the abundance and distribution of marine key populations, which profoundly affects marine fisheries globally, especially for fisheries in the Western and Central Pacific. In addition, the increasing management measures for tuna fisheries by the relevant regional fisheries management organizations (RFMOs) have also caused changes in the distribution of fisheries. To understand the feeding ecological characteristics of Thunnus obesus can provide an invaluable reference for further studies on the biology, population structure and resource assessment, as well as scientific basis for conservation and management of Thunnus obesus resources in tropical WCPO. We collected Thunnus obesus from a tuna longline fishery operating in the tropical WCPO (2°03′S11°17′S，163°14′E173°35′E) between May 2018 and February 2019. All samples were dissected and measured for fisheries biology. A visual method was used to observe the gastric fullness of sampled Thunnus obesus to identify and count individual gastric contents, the feeding ecological indicators such as gastric diversity (ShannonWiener diversity index H′ and Pielou evenness index J) of sampled individuals were also analyzed. On this basis, analysis of variance (ANOVA) was used to investigate the effects of biological factors (fork length, sex, gonadosomatic index) and spatiotemporal factors (lunar phase and fishing depth) on the ShannonWiener diversity index H′ and Pielou evenness index J of the stomach contents of both sexes of Thunnus obesus. In addition, the polytomous logistic regression for the ordinal response model was used to analyze the relationship between different biological and spatial factors on the feeding intensity of Thunnus obesus. A total of 1 123 Thunnus obesus samples were obtained during the survey, both sexes of 881 species were identified, and 682 were identified for individual feeding intensity and stomach composition. Results showed that: 1) In sampled Thunnus obesus populations, 309 (35.07%) were females and 572 (64.93%) were males with a ratio of 1∶1.85. Fork length ranged from 81 cm to 195 cm with a mean of 129.2 cm (SD=±23.0 cm) , and the dominant fork length group ranged from 120 cm to 150 cm (120 cm150 cm for males; 120140 cm for females). ANOVA analysis showed that significant differences existed in fork length between the sexes (P<0.001). 2) Analysis of the stomach contents of 509 nonempty individuals showed that Loligo sp., shrimps, Sardina sp. and Hemisalanx prognathous were the frequent species, with a ratio of 40.32%, 39.74%, 30.06% and 26.98%, respectively (Sardina sp. was used as bait). 3) The observation of feeding intensity showed that the empty stomach rate of Thunnus obesus individuals was 25.37%, and the feeding intensity was mainly composed of level 02, accounting for 81.9% of all samples. Male samples were dominated by level 1, accounting for 31.0% of males , followed by level 0, 2 and 3, accounting for 24.0%, 22.4% and 15.4%, respectively. While female samples were dominated by empty stomach, accounting for 27.91% of females, followed by level 1, 2 and 3, accounting for 25.0%, 23.7% and 14.2% of females, respectively. The empty stomach rate of the sample was high due to gastric inversion when Thunnus obesus was dragged to the deck by pressure changes or active evasion behavior of the fish. 4) ANOVA results showed that both sex and fork length had no significant effect on the feeding ecological niche width index (P>0.05).Fishing depths had also no significant effect on ShannonWiener diversity index H′ (P=0.200), but had a significant effect on Pielou evenness index J (P=0.024), with fishing depths increasing, there was few change in bait species richness while a gradual increase exsited in evenness. Temporal factor (including lunar phase and month) had no significant effect on the feeding niche breadth of both sexes of Thunnus obesuss (P>0.05). 5) The polytomous logistic regression for the ordinal response model and the circular statistic fit showed that females with the same fork length had higher feeding intensity than that of males, but had no significant difference (P=0.293). While with the increasing of fork length, individual feeding intensity decreased significantly (P=0.000 4).There was a significant effect of fishing depths on individual feeding intensity (P=0.002). The distribution of individual feeding intensity at different water depths showed that the empty stomach rate decreased with the increasing of fishing depths, which was inconsistent with the high feeding intensity. The vertical movement behavior of Thunnus obesus was to maximize the energy harvesting rate, and larger individuals had a more pronounced vertical movement habit than smaller ones. Lunar phase had a marginally significant effect on individual feeding intensity (P=0.058<0.1, marginally significant). It suggested that individual feeding intensity was relatively high during the full moon phase , while showed relatively low around the new moon. There was also a significant effect of individual gonad development on feeding intensity (P=0.030), indicating that individual feeding intensity decreased with the increased gonadosomatic index.  Keywords: tropical Western and Central Pacific Ocean; Thunnus obesus; feeding intensity; niche breadth; lunar phase; fishing depth Related Articles | Metrics

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Trophic structure and energy flows in the radial sand ridges and adjacent waters off the coast of Jiangsu Province 2023, 45(1): 60.  Abstract ( 135 )   PDF (2971KB) ( 438 )   Trophic structure and energy flows in the radial sand ridges  and adjacent waters off the coast of Jiangsu Province ZHANG Hu1， BEN Chengkai1， ZU Kaiwei1， SONG Yehui2， XUE Ying2，  YUAN Jianmei1， HU Haisheng1， XIAO Yueyue1， ZHU Chaowen1 （1. Jiangsu Marine Fisheries Research Institute, Nantong Jiangsu226007, China; 2. Fisheries College, Ocean University of China, Qingdao Shandong266003, China） Abstract: The radial sand ridge group in Jiangsu coastal area, located in the southern Yellow Sea, is a unique combination of large sand bodies in the shallow waters of the continental shelf of China. It becomes a special ecological function area due to the influence of multiple factors such as land runoff, sea current and seabed topography, with unique ecological environment. However, fishery resources in this area have declined due to multiple pressures such as overfishing and environmental degradation. At present, studies on this area mainly focus on species diversity, community structure, environmental evolution and simulation, and ecosystem service, while studies on the trophic structure and energy flows in this ecosystem are few. This study analyzed the state of the ecosystem in the area by using Ecopath model, which defined the ecosystem as consisting of a series of functional groups with ecologically similar characteristics, all of which could basically cover the whole process of energy flow in the ecosystem. The model was based on the principle of nutrient balance, which described the balance of energy input and output of the system at a specific time. Subsequently, a massbalance model was constructed by Ecopath with Ecosim software based on the comprehensive survey data collected from the radial sand ridge areas of Jiangsu Province from 2018 to 2019. And the trophic structure, mixed trophic impact and overall characteristics of this ecosystem were analyzed. The ecosystem condition of this area was also evaluated to provide technical support for the protection and restoration of the ecosystem of the radial sand ridge group off Jiangsu, as well as to provide a theoretical basis for protection, management and rational use of the biological resources in this area. The results showed that trophic levels of functional groups in this ecosystem varied from 1.00 to 4.31, consisting of 27 functional groups. The food web of this marine ecosystem was mainly composed of grazing food chain and detritus food chain. The trophic levels of the main fishery species and dominant species in this area ranged from 3.0 to 4.0, and the trophic levels of top predators such as Miichthys miiuy and Harpadon nehereus were above 4.0. Mixed trophic effects analysis (MTI) showed that zooplanktivores, Erisphex potti, other shrimps, Echinodermata, other mollusks and zooplankton played key roles in energy transfer. Within this ecosystem, the energy conversion efficiency of lower trophic levels was low mainly due to the large number of terrestrial organic detritus and phytoplankton, and insufficient utilization by the primary and secondary consumers in this ecosystem. In recent years, the coastal waters of Jiangsu Province have been continuously affected by human disturbances such as reclamation projects and deepwater channel management in the Yangtze River Estuary, which have affected the habitats of filterfeeding organisms (e.g., shellfish, small shrimp and crab species) that use detritus and phytoplankton as their main food sources, resulting in lower utilization of low trophic level prey organisms. The energy conversion efficiency was significantly higher at high trophic levels, which might be due to the fact that the main fishery organisms in this ecosystem were mostly located between trophic levels Ⅲ and Ⅳ, and they played a key role in the energy conversion process of the ecosystem because of their more efficient use of lower trophic level bait organisms. The total ecological conversion efficiency of the ecosystem was 14.93 %, which was slightly higher than that in the other adjacent sea areas. This indicated that the overall utilization of energy in this ecosystem was higher, which might be due to the fact that the radial sand ridge group sea area was crisscrossed by harbors and branches, densely covered with sand hones, and was in a complex tidal dynamic environment. And it was also subject to the transport, remodeling and accumulation of strong tides, which was conducive to maintaining the diversity and high productivity of the biological community. The main nutrient sources of this ecosystem were detritus and phytoplankton, and the energy flows between trophic levels in the grazing food chain were higher than that in the detrital food chain. The total flow (TST) of this ecosystem was higher (8 950 t·km-2·a-1), indicating that the overall scale of the ecosystem was relatively large, which was conducive to maintaining the ecosystem health. The total primary production (TPP) value of the ecosystem in the radial sand ridge areas of Jiangsu Province was 4 135 t·km-2·a-1, which was higher than that in the adjacent areas, but lower than that in the Gouqi kelp bed. However, the ratio of total primary production to total respiration (TPP/TR) in this ecosystem was 6.97, which was significantly higher than that in the adjacent areas. The connection index (CI) and system omnivorous index (SOI) were 0.34 and 0.28, respectively. The connectivity index was at a high level compared with the neighboring areas, while the system omnivorous index was at an intermediate level, which indicated that this ecosystem was in an unstable state and was susceptible to external disturbances. This paper will contribute to the understanding of trophic structure and overall condition of the ecosystem in the radial sand ridge areas of Jiangsu Province, which can provide technical support for the protection and restoration of this ecosystem and theoretical guidance for the sustainable use and management of fishery resources. In the future, we should strengthen the protection and restoration of the ecosystem in this sea area, reduce the impact of anthropogenic disturbance on the ecosystem, and make full use of the high primary productivity of the ecosystem in this sea area through measures such as stocking and releasing. At the same time, it should be combined with the construction of marine protected areas, control of fishing intensity and other measures to strengthen the conservation of fishery resources and ecosystem restoration, increase the stability of the ecosystem in this sea area, and give full play to the resource and environmental advantages of the ecosystem of the radial sand ridge group, which will be of great practical significance for promoting the highquality development of marine fisheries in Jiangsu Province, and the construction of marine ecological civilization. Keywords: radial sand ridges; Ecopath model; trophic structure; energy flow Related Articles | Metrics

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Spatio-temporal and spatial distribution and biological characteristics of Larimichthys polyactis in Jiangsu sea area 2023, 45(1): 73.  Abstract ( 146 )   PDF (4453KB) ( 450 )   Spatio-temporal and spatial distribution and biological characteristics  of Larimichthys polyactis in Jiangsu sea area LI Zidong1， WANG Yanping2， ZHONG Xiaming2， YANG Jiaxin1， GE Hui2， SHI Jinjin2，  XIONG Ying2， TANG Jianhua2， WU Lei2， YAN Xin2， WANG Chuqing2 （1. College of Marine Science and Engineering, Nanjing Normal University, Nanjing 210023, China; 2. Jiangsu Marine Fisheries Research Institute, Nantong Jiangsu226007, China） Abstract: In order to further understand the temporal and spatial distribution characteristics and related patterns of Larimichthys polyactis in Jiangsu sea area timely and to manage the biological resource properly, data collected from four seasonal fishery resource surveys in Jiangsu sea area (31°45′N35°00′N,119°30′E125°00′E) from 2017 to 2018 were analyzed. The results showed that: 1) In spring, the average body length and average body weight of Larimichthys polyactis were at low values (78.96mm, 13.68g), while in autumn and winter, average body length (103.04mm in autumn, 96.20 mm in winter) and average body weight (19.62g in autumn, 16.35 g in winter) reached high values throughout the year after baited in summer. Sex maturity was the highest in spring, with 36.1% of samples still in the spawning stage, winter was the next. Sex maturity was the lowest in summer, all samples were at stage II. Feeding intensity was higher in spring and autumn than in summer and winter, it was mainly because parent fishes needed to replenish the energy loss after spawning in spring. The average feeding level of fishes reached the highest in autumn as the later stage of Larimichthys polyactis’s feeding stage. In summer, Larimichthys polyactis entered the feeding stage, the behavior of feeding just started, and the proportion of individuals with high feeding level was small. In winter, the temperature of Jiangsu sea area fell drastically, fishes were affected by the change of environment to reduce even stop feeding, then finding appropriate overwintering grounds became an urgent need. In terms of sex ratios, the ratio of male number to female number did not vary seriously over the four seasons and years, and there were more males than females, which was related to the recession of Larimichthys polyactis resources. 2)The spring spawning grounds of Larimichthys polyactis in Jiangsu sea area were mainly located in the adjacent waters north of the mouth of the Yangtze River (32°00′N33°15′N, 121°30′E122°15′E), the excellent location, rich food organism and good ecological environment were important reasons to attract parent fishes to spawn here; the summer feeding grounds were mainly located in the southern part of Dasha fishing ground (32°00′N33°00′N, 123°00′E124°30′E) and the northern outer waters of Lyusi fishing ground (33°30′N34°00′N, 121°30′E122°00′E). At this time, the feeding groups became disperse, the distribution range became wide and the stock density became significantly smaller than that in spring. In addition, the intensity of fish feeding became larger and the growth rate of fishes were significantly accelerated. The autumn feeding ground was located in the sea southeast of Lianqingshi sishing ground (34°00′N35°00′N, 122°30′E124°00′E), the size of fishes continued to increase, the feeding groups migrated to deep water area, the distribution range became more disperse than before, and the central area of resource density moved eastward to the deep water area in the northeastern Yellow Sea. Combined with environmental factors, it was found that the distribution of Larimichthys polyactis feeding grounds in Jiangsu sea area was more influenced by temperature factors and less influenced by salinity; the overwintering ground was located in the sea northeast of Dasha fishing ground (33°00′N35°00′N, 123°30′E124°30′E), with the fall of water temperature in Jiangsu sea area, Larimichthys polyactis migrated to the overwintering grounds off the southcentral Yellow Sea and off the northern East China Sea. Considering biological characteristics and resource density distribution together ,we inferred that: the center of Larimichthys polyactis overwintering grounds was not located in Jiangsu sea area(31°45′N35°00′N,119°30′E125°00′E). In addition, we found that the overwintering grounds shifted about one latitude to the northwest than before; 3)In spring, parent fishes with high sex maturity gathered to spawn and reared their young in waters near the Lyusi fishing ground, which located in the north of the Yangtze River mouth and along the offshore areas of Jiangsu Province, forming a high density area of Larimichthys polyactis; in summer and autumn, fish larvae with juveniles and adult fishes tended to disperse to bait, which were widely disperse in the research area with a clear tendency to move eastwards; the distribution of bait field was greatly affected by water temperature and less affected by salinity. In winter, Larimichthys polyactis migrated from the feeding grounds to the deep water of the outer wintering grounds(water depth range 36.435 m80.675 m); 4)Combined with the analysis of biological characteristics and resource density of Larimichthys polyactis samples, it was found that Larimichthys polyactis in Jiangsu sea area had the attributes of spawning, baiting and overwintering in deep water with seasonal changes, and the outline of reproduction and growth development system was relatively complete, so it could be inferred that there was a relatively stable dependence relationship between Larimichthys polyactis population and Jiangsu waters, which provided a theoretical basis for the conservation and rational exploitation of Larimichthys polyactis resources in Jiangsu sea area. Keywords: Larimichthys polyactis； density index of resources； Jiangsu sea area； temporal and spatial distribution； biological characteristics Related Articles | Metrics

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Spatial distribution of Larimichthys polyactis juveniles in the southern Yellow Sea and northern East China Sea in summer 2023, 45(1): 86.  Abstract ( 128 )   PDF (1506KB) ( 426 )   Spatial distribution of Larimichthys polyactis juveniles in the southern  Yellow Sea and northern East China Sea in summer GAO Yang1,2,3，ZHANG Yi2,3，ZHANG Hui2,3， LIU Zunlei2,3，LI Shengfa2,3，CHENG Jiahua2,3 (1. College of Marine Sciences, Shanghai Ocean University, Shanghai201306, China； 2. East China Sea Fisheries  Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China； 3. Key Laboratory of East China  Sea Fishery Resources Development and Exploitation, Ministry of Agriculture and Rural Affairs, Shanghai200090, China) Abstract: Small yellow croaker Larimichthys polyactis is an economically important species in Chinese offshore ecosystem. Juvenile is in an important period of transition from larvae to adult. This stage is not only different from the characteristics of high natural mortality and fluctuating abundance in the early life history period, but also different from the higher feeding capacity and environmental adaptation of adults. Juveniles have different preferences for the choice of living environment.The abundance and spatial distribution of the juvenile are crucial to the population dynamics and they are sensitive to environmental factors. Therefore, studying the geographic distribution pattern of juvenile populations and their dominant factors will help to clarify their selection patterns for the living environment. Larimichthys polyactis has obvious cluster habit and migration characteristics. It does seasonal migration throughout the year between spawning grounds, feeding grounds and wintering grounds. During feeding periods, it is mainly distributed in warm water control areas or marginal areas of warm water areas. The western part of Dasha fishery is the largest feeding ground for Larimichthys polyactis in the east Yellow Sea. At present, the research on Larimichthys polyactis populations at home and abroad mainly focuses on juveniles and juvenile populations, mixed feeding populations, and adult overwintering populations. There are few related studies on juvenile feeding populations alone. Generalized additive model (GAM) is a nonparametric generalized multiple linear regression method proposed by HASTIE. It can flexibly describe the response of species to environmental factors and predict the relationship between multiple independent variables and dependent variables, and can well analyze the relationship between fishery resources and multiple environmental factors in fisheries.In order to understand the spatial distribution characteristics of Larimichthys polyactis juveniles ，a survey was conducted in the southern Yellow Sea and northern East China Sea (30°30′N35°00′N, 120°00′E127°00′E) in August 2019 to explore the relationship between the quantity distribution of Larimichthys polyactis juveniles and related environmental factors. Three generalized additive models (GAM) were compared. The fitting effect and predictive ability of Delta GammaGAM were better than that of TweedieGAM and Delta LognormalGAM. For Delta GammaGAM, the root mean square error was 12 014.43, the Pearson correlation coefficient was 0.461, and Spearman’s rank correlation coefficient was 0.699. The distribution of Larimichthys polyactis showed a high degree of autocorrelation in space, and was concentrated in the area of 32°N34°N and 122°E124°E, and diminishingly diffused from the center. According to the models, the distribution of Larimichthys polyactis juveniles was only significantly related to water depth with a negative linear relationship, which explained the nearshore distribution preference of Larimichthys polyactis juveniles. Keywords: Larimichthys polyactis juveniles; generalized additive model; environmental factors; southern Yellow Sea Related Articles | Metrics

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Morphological variation analysis of different geographical populations of Mactra chinensis 2023, 45(1): 95.  Abstract ( 156 )   PDF (1083KB) ( 422 )   Morphological variation analysis of different geographical  populations of Mactra chinensis JING Yuanyuan, HU Fanguang, LIU Guangbin, WU Haiyi, SUN Ming, CHEN Qun, ZHANG Tianwen (Marine Science Institute of Shandong Province,Qingdao Shandong266104,China) Abstract: From the perspective of breeding, the genetic background of parent shellfish without artificial system breeding or improvement is not clear, and there is a risk of inbreeding, which reduces the genetic diversity of the population and leads to the degradation of economic traits.Morphological traits and body mass traits are important basis for evaluating the genetic information of shellfish, however, there has been no report on the morphological differences of different geographical populations of Mactra chinensis. Therefore, it is necessary to conduct a comprehensive and systematic investigation and analysis of the current situation of Mactra chinensis population resources through morphological difference analysis, which can provide an important basis for the identification of geographical populations and protection and utilization of genetic resources of Mactra chinensis.The multivariate analysis method is suitable for the analysis of morphological differences of aquatic animal groups. The results can objectively reflect Morphological differences and have been widely used in shellfish. The multivariate morphometrics methods were used to explore the morpholobical variation of different geographical populations of Mactra chinensis along the coastal areas of Shandong Province. Researchers collected wild Mactra chinensis populations in Donggang（DG) in Rizhao ,Haiyang(HY) in Yantai , Huangdao（HD) in Qingdao,Wendeng（WD) in Weihai and Kenli（KL）in Dongying sea areas, respectively. Five Mactra chinensis populations were 2 years old, which were transported to the laboratory in batches at low temperature.A total of 50 Mactra chinensis were randomly selected from each group, morphological indexes were measured by vernier caliper, and body quality indexes were measured by electronic balance. The growth indexes of different groups of Mactra chinensis were calculated by Excel, including shell weight index and condition factor. Multivariate morphometric methods were used to analyze the morphological data of five wild populations of Mactra chinensis by variance analysis, principal component analysis, cluster analysis and discriminant analysis. The growth trait indices showed that WD population had the thickest shell, followed by HY population , KL population, DG population and HD population;there was no significant difference in ISW among WD population, KL population and HY population, and they were significantly higher than DG and HD populations ( P<0.05 ), HD population had the thinnest shell and the lowest condition factor and the condition factor of HY population was maximal, there was no significant difference in condition factor among 5 populations; the cofficient difference(C.D) between five geographical populations was 0.5151.245, less than 1.28, showing that the morphological differences among 5 groups were still intragroup differences, the morphological variation was characterized with undersubspecies; three principal components were constructed, of which the contributory ratio, from high to low, the principal component 1 was 33.71%, the loading value of body mass traits was the maximum, showing that the principal component 1 represented the influence of condition factor, shell thickness and width of shell on the shell shape; the principal component 2 was 27.16% , the shell height and the distance from the front end to the ventral margin had the greatest influence, with loading values of 0.700 and 0.686, respectively, it represented the influence of shell height and growth bias on shell shape,the principal component 3 was 14.42%, summing up to 75.29%, the three principal components explained 75.29% of the morphological differences among the five populations; cluster analysis of the average correction values of morphological indexes of five populations revealed that four populations clustered into two branches, HY population,WD population and KL population, DG population and HD population were grouped into one group respectively, it showed that morphological characters were rather similar between HY population and WD population, from which KL population was quite different; different geographical groups of Mactra chinensis were predicted and classified by discriminant function, four discriminant functions of five populations were established, the discriminant accuracy rate was 70.0%94.0%, with a total of 80.0%, the discriminant result was good, showing that the established discriminant function could be used to determine the attribution of a single Mactra chinensis individual in DG, HY, HD, WD and KL geographical groups.Studies showed that there were some differences in the morphology of five geographical populations of Mactra chinensis, the difference of population plumpness was related to seawater temperature and food abundance when samples were taken back. The size and shape of the shell, such as shell thickness, shell width, shell height and growth bias, determined the morphological differences among different geographic populations of Mactra chinensis, which was similar to the results of other shellfish studies. Mactra chinensis was strongly dependent on the environment, different ecological environments might have a certain impact on the morphology of Mactra chinensis, in the same or similar geographical or ecological environment, the morphology was consistent. In this study, KL population was quite different from the other populations, the morphological differences between HY population and WD population were small, and the morphology was the closest. the morphological differences between DG population and HD population were small, and the morphology was relatively close. This difference might be caused by geographical differences that resulted in different habitats. These environmental differences were likely to affect the growth and development speed of Mactra chinensis, which was reflected in the differences in shape measurement characteristics.The morphological characteristics of five geographical populations showed consistency with the geographical environment, which proved that the morphological differences of Mactra chinensis population were related to the geographical distance, the closer the distance, the more similar the ecological environment, and the smaller the morphological differences. WANG pointed out that the morphology of Monodonta labio was consistent in similar geographical or ecological environments, which was similar to the results of this study. However, in the study of CHEN and LIU  on the morphological differences of different populations of other shellfish, it was found that the clustering of population morphological indicators was inconsistent with the geographical location. The reason might be that the length of the planktonic period of different shellfish larvae was different, and the larvae with longer planktonic period would spread with the current. In addition, there were activities such as introduction of aquatic products and proliferation and release between different sea areas, which increased the probability of gene exchange between different groups and made it difficult to form effective geographical isolation. It also showed that the phenotypic variation of shellfish morphological characteristics was affected by genetic factors and environmental factors, morphological indicators could only reflect the combined effects of genetic and environmental factors among populations. Keywords: Mactra chinensis; geographical population; morpholobical variation analysis Related Articles | Metrics

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Study on secondary metabolites of Antarctic fungus Aspergillus sp. NJ49 2023, 45(1): 105.  Abstract ( 99 )   PDF (1094KB) ( 407 )   Study on secondary metabolites of  Antarctic fungus Aspergillus sp. NJ49 CHEN Sha1,2, TIAN Xiaoqing1,2, FAN Chengqi2, LI Chongbin1,2, LU Yanan2 (1. College of Food Science, Shanghai Ocean University, Shanghai201306,China; 2. East China Sea  Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090,China) Abstract: The polar region is a special ecosystem harboring a variety of fauna and microorganisms including bacteria, actinomycetes and fungi. To survive in conditions of low temperature, strong wind, low nutrient and high UV radiation, polar organisms require a wide range of biochemical and physiological adaptations that are essential for survival. Organisms from the polar regions are rich sources of various chemical scaffolds and novel natural products with good biological activity. In recent years, a large number of novel natural biological compounds with various activities such as antibacterial, antitumor and antiviral have been isolated from microorganisms, mollusks and other polar organisms. Aspergillus fungi have been reported as one of the most productive and potential resources for the production of structurally diverse secondary metabolites, mainly including alkaloids, polypeptides, terpenoids and polyketides. Researchers have discovered many different kinds of secondary metabolites from Antarctic fungi with novel structures and biological activities. Antarctic krill is an important species in the Antarctic ecosystem and is one of the most abundant single biological resources on the earth. At present, studies on the intestinal microbes of Antarctic marine organisms are relatively limited, especially for Antarctic krill, mainly focusing on their distribution, abundance, growth status and krill oil. The research on the intestinal microbes of Antarctic krill is still in the exploratory stage, and few studies involve the secondary metabolites of Aspergillus fungi in the intestinal microbes of Antarctic krill. Isolating microorganisms from Antarctic krill and obtaining natural products is an important way to enrich natural product research. To continue exploring the application potential of valuable Antarctic fungal resources, molecular identification, isolation of secondary metabolite and structural identification of an Antarctic krill symbiotic fungal strain were carried out in this study. The fungal DNA was extracted using Takara kit, amplified by PCR, and the amplified product was sequenced. The ITS rDNA sequences obtained from the sequencing were subjected to BLAST analysis. The phylogenetic tree was constructed through comparative analysis. ITS rDNA sequence analysis showed that the ITS rDNA sequence of the strain NJ49 and A. niger MK457457 had high similarity. According to the constructed phylogenetic tree, strains NJ49 and A. niger were on the same branch with the highest similarity. Combined with morphological methods, the strain was identified as A. niger NJ49. For strain NJ49, we used the original medium, Rose Bengal Agar Medium, for activation. The seed solution was first cultured and mass fermentation was carried out using Martin’s liquid medium as fermentation medium. A total of 54 L fermentation liquid was obtained by shaking culture. The fermentation liquid was filtered to obtain mycelium and fungal fermentation filtrate, and the mycelium was extracted with ethanol ultrasonic to obtain the extraction liquid, and the fermentation broth and the fungal fermentation filtrate were combined to obtain the ethyl acetate and aqueous phases. After the extraction liquid and mycorrhiza were combined, the ethyl acetate phase and water phase were extracted. The ethyl acetate fraction was separated by Sephadex LH20 gel column and high performance liquid chromatography (HPLC). And the mobile phase prepared by HPLC was acetonitrile water mixed system, gradient elution, flow rate of 2.5ml·min-1, UV detection wavelength of 214 nm, 234 nm, and 254 nm. Compounds 2, 5, 6 were obtained from ethyl acetate. The water part was roughly divided into four parts by macroporous adsorption resin: NJ49MeI, NJ49MeII, NJ49MeIII and NJ49MeIV. NJ49MeI was separated by G25 gel column and HPLC to obtain compounds 3, 4, 8, 10, 12. NJ49MeII was separated by G25 gel column and HPLC to obtain compounds 1, 2, 7, 9, 11. And the structures were identified by modern spectroscopic analysis methods, such as high performance liquid chromatography time of flight mass spectrometry (HPLCTOFMS), nuclear magnetic resonance spectrum (NMR) (1HNMR and 13CNMR) and other analytical methods. A total of 12 compounds were isolated and identified from A. niger NJ49, including TrpValVal(1), PheValVal(2), cyclo(His, Leu)(3), cyclo(Pro, Arg)(4), (3S,12aS)3(Isopropyl)2,3,6,7,12,12ahexahydropyrazino［1′,2′∶1,6］pyrido［3,4b］indole1,4dione(5), cyclo(Pro, Phe) (6), cyclo (Val, Phe) (7), cyclo(Pro, Tyr) (8), cyclo(Pro, Val) (9), PheVal (10), sclerin (11)and phydroxyphenylethylamine (12). 10 peptide compounds were subdivided into chainlike tripeptides (1, 2), dipeptide (10) and cyclic dipeptide (39). According to the chemical structure types of the secondary metabolites of NJ49, the secondary metabolites of the fungi of Aspergillus Antarctica were mainly polyketones, alkaloids and peptides. Compounds 3, 6, 9, 11 had a variety of antibacterial activity. The results showed that strain NJ49 might have a good application prospect in antibacterial activity, and the production of these active compounds could be increased by expanding the fermentation yield.  Compounds 3, 9, and 11 were firstly isolated from Antarctic fungi Aspergillus. The results of the study provide a basis for deepening the understanding of Antarctic marine microbial resources and enriching the secondary metabolite pool of Antarctic fungi Aspergillus. The findings are useful for further understanding the structural types of secondary metabolites and the discovery of active natural products of Aspergillus Antarctica fungi reference significance. Comparatively speaking, marine natural products are mainly studied in temperate and tropical organisms. The research on the active natural products of Aspergillus Antarctica is still in its infancy at present, which may be limited by the extreme environment and scientific research conditions in Antarctica. The resources of Aspergillus Antarctica can continue to be excavated in the future and the medicinal potential of Aspergillus antarctica fungi can be fully utilized. In the systematic isolation study of this strain, it was found that the metabolites of this symbiotic fungal strain were limited under the conditions in this paper, and no terpenoids and alkaloids reported in the literature were isolated. The structural novelty of the secondary metabolites isolated from the NJ49 ferment is still lacking. This may be due to different culture conditions. In the subsequent experiments, we will try to use rice medium to optimize the existing culture conditions, and combine with LCMS analytical guidance, and screen suitable culture conditions before carrying out LCMS guided separations to isolate structurally novel active compounds and improve the efficiency of isolation and identification of secondary metabolites with complex or novel structures. Keywords: Antarctic fungi; Aspergillus; secondary metabolites; structure identification Related Articles | Metrics

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Research progress of Antarctic fishery resources based on bibliometrics analysis  2023, 45(1): 114.  Abstract ( 194 )   PDF (5644KB) ( 473 )   Research progress of Antarctic fishery resources based on bibliometrics analysis  FAN Jiayu, LIU Yang, DUAN Mi, LIU Chunlin, TIAN Yongjun （Laboratory of Fisheries Oceanography, College of Fisheries,  Ocean University of China, Qingdao Shandong266003, China） Abstract: In order to have an objective and comprehensive understanding of the research status and hotspots of Antarctic fishery resources at home and abroad, relevant literatures on Antarctic fishery resources included in Web of Science Core Collection, CNKI, and WANFANG DATA from 1990 to 2020 were used as statistical sources, including 3 369 English literatures and 515 Chinese literatures. All selected articles were reviewed and analyzed comprehensively, referencing the sustainable development of Antarctic fisheries and future research trends. Bibliometrics summarizes the dynamic development trends of literature and the research progress of different disciplines through visual and quantitative analysis. Statistical analysis was conducted on the growth law, citation situation, and journal distribution of relevant literature by bibliometric method. Keywords, authors, and countries/regions were analyzed by VOSviewer software, and scientific visualization was made. The results showed that the annual growth rate of Chinese literatures was nearly twice that of English literatures. The number of articles published and the total citation frequency of Antarctic fishery resources research showed a good and stable trend. Regarding journal distribution, it conformed to Bradford′s law of literature dispersion, and the top 20 Chinese and English journals were of high quality and had great academic influence. Marine Fisheries and Polar Biology were the most popular journals in Chinese and English literatures. There was a high degree of overlap between highly cited and published journals. In research hotspots and future research trends, research focused on English literatures mainly concentrated on the Antarctic krill and climate change, Antarctic fish and evolution, important geographical study areas in the Antarctic, etc. The future research direction will be Antarctic biological resources conservation and management, biodiversity and Ross Sea area, etc. The research focused on Chinese literature mainly centered on the Antarctic krill and the exploitation of Antarctic fishery resources and food processing. Regarding author collaboration network analysis, EASTMAN J T from Ohio University published most literatures in English. The connections within and between the clusters of the English author collaboration network visualization map were more intensive, indicating close cooperation and frequent communication among authors. Professor Zhu G P of Shanghai Ocean University published the most Chinese literatures, and a certain intensity and scale of cooperative communication networks were formed into the Chinese author cooperative network visualization map clustering. Regarding national/regional cooperation networks, countries in North America and Europe had close cooperation. The United States had the highest number of documents and occupied a dominant position in the cooperation network, while China had the closest cooperation with the United States. Based on the bibliometric analysis of the literature in this field, the following suggestions are put forward for the research and development of the Antarctic fishery field in China:1) Objectively understand the shortcomings of the research in the Antarctic fishery field in China, pay close attention to the research hotspots and scientific frontiers of relevant research institutions at home and abroad, and increase the scientific research investment and financial support. 2) Improve the degree of scientific data sharing, entirely use international open data, and establish an innovative cooperation platform for scientific openness and sharing. 3) Promote interdisciplinary research, expand global vision, enhance international influence and competitiveness, cultivate the interdisciplinary cooperation ability of young scholars, and provide new ideas and technologies for Antarctic fishery research.  Keywords: bibliometrics; Antarctic fisheries; Antarctic fishes; Antarctic krill; scientific knowledge map; research hotspots  Related Articles | Metrics