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Isolation of intestinal symbiotic or epiphytic microbes from Gammarus sp. and chemical characterization of  Streptomyces xiamenensis YF008#br# 2023, 45(2): 129.  Abstract ( 243 )   PDF (1556KB) ( 534 )   Isolation of intestinal symbiotic or epiphytic microbes from Gammarus sp. and chemical characterization  of Streptomyces xiamenensis YF008 DAI Ying1， LU Jingrong2， ZHOU Meihong1， YANG Fan2， LIN Houwen2 (1. College of Food Science and Technology， Shanghai Ocean University， Shanghai201306，China； 2. Department of Pharmacy，Renji Hospital，School of Medicine，Shanghai Jiao Tong University，Shanghai200127，China) Abstract: The extreme habitats of the Antarctica have great potential to discover special biologicallyactive natural products. Polar microorganisms have formed survival mechanisms and biosynthetic pathways different from terrestrial strains to adapt to the unique environment of polar regions. Polar actinomycetes have metabolized a series of novel microbial natural products with interesting structures. Polar microbes have greater potential for exploitation as sources of novel active secondary metabolites than terrestrial microbes. The microbiota within the NorthSouth polar circle, a powerful producer of novel natural products, has become the target of scholars in natural product research. Gammarid (Gammarus sp.) is a kind of crustaceans belonging order Amphipoda, suborder Gammaridea, family Gammaridae that can live in the Antarctic deep sea. At present, there are few reports on the intestinal symbiotic or epiphytic microbes of Gammarus sp., and there is large space for innovative development on the isolation of intestinal intestinal symbiotic or epiphytic microbes of Gammarus sp. and the study of their secondary metabolites. This study is aim to discover and identify the intestinal symbiotic or epiphytic microbes from Gammarus sp. 6 000 m deepth in the Antarctic sea, and the chemical structural diversity of metabolites of a valuable actinomycete strain obtained from Gammarus sp. were studied. The strain was isolated by gradient dilution coating method with inverted cultivation under 28 ℃ for 221 days. After the growth of colony, the single colony was obtained by lineation purification. The isolation medium was R2A, SC, M7, SIM2, F, 2216E and M10 solid medium, and the purification medium was Gao’s No.1, SFM and LB solid medium. The isolated strains were cultured on the fresh medium plates and identified by morphological observation and 16S rRNA sequencing. Genomic DNA of the strains was extracted, PCR amplified with bacterial universal primers 27F and 1492R, and the species genera of the strains were identified by 16S rRNA sequencing after agarose electrophoresis showed the target band at 1.5 kb. Strain sequences were submitted to GenBank for blast alignment, and neighborjoining (NJ) method in MEGA 7.0 software was selected to construct a phylogenetic tree for actinomycetes. The selected strains were subjected to fermentation. The comprehensive application of thinlayer chromatography (TLC), silica gel column chromatography, Sephadex LH20 column chromatography, ODS column chromatography and semipreparative high performance liquid chromatography (HPLC) methods were used to separate and purify the compounds. The chemical structure of the compound was identified by spectral data such as proton nuclear magnetic resonance spectroscopy (1HNMR), carbon nuclear magnetic resonance spectroscopy (13CNMR), mass spectrometry (ESIMS) techniques, and combined with the reference data. Seventeen strains were isolated from Gammarus sp. and analysis of 16S rRNA sequences indicated that their taxonomic status was assigned to nine genera, including 11 strains of bacteria and 6 strains of actinomycetes. Among these isolated strains, one strain was Rothia sp., two were Kocuria sp., two were Brachybacterium sp., two were Dietzi sp., one was Carnobacterium sp., two were Psychrobacter sp., one was Staphylococcus sp., one was Streptomyces sp., five were Nocardiopsis sp. The strain YF008 was 100% similar to the model strain Streptomyces sp. ZJ306 (KF954540.1), and in the same evolutionary branch with Streptomyces xiamenensis strain XY111 (MH432665.1), and finally was identified as Streptomyces xiamenensis based on the colony morphological characteristics. The two strains of psychrophilic bacteria (Psychrobacter sp.) isolated in this study were psychrophilic bacteria from polar oceans. The fermentation metabolites of Gao’s No.1 liquid medium from the actinomycete Streptomyces xiamenensis YF008 was of research value, and the whole genome sequencing results of this strain showed that it contained 25 BGCs covering various types of functional gene clusters including PKS, NRPS, terpene, butyrolactone and many others. Among these BGCs, BGC15 had no similar gene cluster, which was speculated to possibly encode a new skeleton type of secondary metabolites. So the strain Streptomyces xiamenensis YF008 was selected for secondary metabolite studies. The strain YF008 was activated on the fresh Gao’s No.1 solid plates. The single colony was put into a 100 mL conical flask containing 25 mL TSBY liquid medium (with stainless steel springs), and shaken for 3 days at 28 ℃, 220 r·min-1 to obtain the seed fluid. Then the seed fluid was inoculated at 5% into a 500 mL conical flask (with stainless steel springs) containing 150 mL of Gao’s No.1 liquid medium and fermented in a 220 r·min-1 oscillating incubator at 28 ℃ for 5 days. 18.5 L fermentation broth of strain Streptomyces xiamenensis YF008 was extracted with equal volume of ethyl acetate (ultrasonic extraction for 2030 min) for 4 times until colorless. 16.537 g crude extract was obtained by combining extraction layers and concentrating under reduced pressure. After several means of separation, eight small molecular secondary metabolites were isolated from the crude extract obtained from the fermentation broth of actinomycete Streptomyces xiamenensis YF008 and identified as: 1(10)E,5Egermacradiene-2,11-diol (1), N［2(4hydroxyphenyl)］ethylacetamide (2), ［cyclo(LPheGly)］(3), ［cyclo(LPheAla)］(4), ［cyclo(DPheLIle)］(5), ［cyclo(LHypLPhe)］(6), ［cyclo(DLeuLPro)］(7), ［cyclo(LPheLPro)］(8). There are mainly one germacranetype sesquiterpene, one tyramine derivative, and six cyclic dipeptides. Compound 1 and compounds 36 were isolated from Streptomyces xiamenensis for the first time, and compound 1 was a special germacranetype sesquiterpene with ten membered ring system. In addition, these compounds have been reported to exhibit various pharmacological activities, such as antiinflammatory, antitumor, and antibacterial activities. Subsequent indepth studies will continue to be carried out on the activity of the isolated compounds. The secondary metabolites isolated from Streptomyces xiamenensis YF008 are known compounds. In order to obtain microbial secondary metabolites with novel structure and activity, it is necessary to further optimize the culture medium and fermentation conditions, and to add metal ions, antibiotics (such as chloramphenicol, tetracycline, kanamycin), inducers (such as arabinose), exogenous small molecules or through microbial coculture, ribosome engineering and other methods are used for fermentation optimization to activate the silent gene of the strain as much as possible and stimulate it to produce more secondary metabolites with rare structure and good activity. We can also try to stimulate the production of novel and special secondary metabolites by heterologous expression of novel BGCs through genome mining. Other separation methods can also be tried. The result of the study contributes to the understanding of the intestinal symbiotic or epiphytic microbes of Gammarus sp. in the deep sea of the Antarctica., enriches the chemical structural diversity of secondary metabolites of polar marine microorganisms, and provides a reference for the comprehensive utilization of Antarctic gammarid and polar actinomycetes. Keywords: Gammarus sp.; actinomycetes; Streptomyces xiamenensis; metabolites; isolation and identification Related Articles | Metrics

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Evaluation of effects of compound oil and low fish meal feed on the cultivation of Trachinotus ovatus  2023, 45(2): 140.  Abstract ( 187 )   PDF (823KB) ( 448 )   Evaluation of effects of compound oil and low fish meal feed on the cultivation of Trachinotus ovatus  ZHENG Jun1, XIE Dizhi1, YE Rukai1, ZHANG Haitao2, WANG Zhaoduo2, XIE Ruitao2, LI Yuanyou1 （1. College of Marine Sciences of South China Agricultural University , Guangzhou〓510642, China;  2.China Key Laboratory of Aquatic, Livestock and Poultry Feed Science and Technology in South China,  Ministry of Agriculture and Rural Affairs, Guangdong Evergreen Feed  Industry Co., Ltd., Zhanjiang Guangdong〓524000, China） Abstract:  Cumulative studies have shown that adequate lipid consumption is beneficial for improving the growth, protein efficiency ratio, and nitrogen and phosphorus retention of fish, as well as saving dietary protein and cost. Golden pompano Trachinotus ovatus, one of the promising candidates for intensive aquaculture in southern China with an annual production of around 240,000 tons, is a carnivorous marine fish. The dietary protein requirement of T. ovatus is relatively high at around 50%. Based on the essential fatty acids (EFA) requirement of T. ovatus［1.241.73% n3 high unsaturated fatty acids (HUFA), ratio of DHA to EPA about 1.4］, the compound oil products (BO, consisting of fish, soybean, rapeseed and perilla oils with proper proportions) were developed by our group. In the previous studies, the growth promoting effects of compound oil and low fish meal diets (6 % fish meal) on Trachinotus ovatus was similar with control diets (fish oil and 20 % fish meal, prepared by smallscale production technology and culture conditions). To further evaluate the largescale application effect of compound oil products and low fish meal diets on the culture of Trachinotus ovatus, four isoproteic (48%) and isolipidic (11%) diets (D1 D4) were formulated by the largescale production process in a local feed company. Based on the commercial feed of Trachinotus ovatus (containing 20% fish meal), D1 contained 10% fish oil, D2 10% compound oil, D3 8% compound oil +4% fat powder. While diet D4 was low fish meal diet (containing 6.6% fish meal) with compound oil + fat powder. Each diet was fed to triplicate groups of Trachinotus ovatus juveniles (initial body weight about 64.75 g) in floating pond cages (2 m×2 m×1.5 m, 100 fish per cage) for 8 weeks. During the 8week feeding trial, the water temperature was 26.532.5 ℃, salinity was 2732 ‰. Fishes were fed to nearly satiation twice a day at 8∶〖KG-*2〗00 and 16∶〖KG-*2〗00. At the end of the feeding trial, all fishs were weighed after being fasted and anesthetized with 0.01% 2phenoxyethanol. Six fishes per treatment were sampled for measuring body proximate composition, six fish were sampled for measuring muscle texture and the remaining six fish per treatment were sampled for collecting serum, liver, dorsal and ventral muscle. All samples were quickly frozen in liquid nitrogen and then stored at -80°C until analysis. The comparative analysis of growth performance, proximate composition of the whole body and muscle, serum biochemical parameters and hepatic antioxidant parameters, muscle fatty acid profiles, edible quality, and texture was studied among the four groups. The results showed that the final weight, weight gain rate (WGR), specific growth rate (SGR), daily intake rate (DFR), condition factor (CF), hepatosomatic index (HSI), viscerosomatic index (VSI) and survival rate (SUR), as well as proximate composition (moisture, crude fat, crude protein, crude ash) of all body displayed no significant difference among the four dietary groups (P>0.05). However, the feed coefficient (FC) of fish in diet D2 was lower than that of fish in the other three diets, and even significantly lower than that of fish in diet D1 (P<0.05). Comparing to D1 and D2 groups, low serum glutamic oxalacetic transaminase (GOT) and glutamicpyruvic transaminase (GPT) activities, and low density lipoprotein (LDL) levels were detected in D3 and D4 groups, and triglyceride (TG) level in D4 group was significantly lower (P<0.05). While serum highdensity lipoprotein (HDL) and total cholesterol levels (TCHO), acid phosphatase (ACP) activities were comparable among four groups (P>0.05). In terms of hepatic antioxidant parameters, there was no statistic difference in hepatic total antioxidant capacity (TAOC), catalase (CAT), superoxide dismutase (SOD) activities among the four groups (P>0.05), while low hepatic malondialdehyde (MDA) levels were observed in fish in diet D3 and D4. In terms of muscle nutrition, the crude protein and moisture content in the dorsal muscle of T. ovatus showed significant differences among four dietary groups (P<0.05). Specifically, the crude protein content of dorsal muscle was significantly higher in fish in D3 and D4 than that of D1 group (P<0.05). In addition, D2 group had lower dorsal muscle moisture content than the D1 group (P<0.05). while there was no difference in dorsal muscle moisture of fish among D1, D3 and D4 groups (P>0.05). The crude protein and moisture content of abdominal muscle showed no significant difference among four dietary groups (P<0.05), while crude lipid content in D4 group was significantly lower than that in D3 group (P<0.05). The fatty acid composition of dorsal and abdominal muscle of fish displayed parallel change pattern with the dietary fatty acid. Comparing to D1 group, the dorsal and abdominal muscle ARA, EPA, DPA DHA, HUFA and n3 polyunsaturated fatty acid (PUFA) content of D2D4 groups were significantly lower, while their monounsaturated fatty acid (MUFA) and n6 PUFA content were significantly higher (P<0.05). High dorsal muscle saturated fatty acid (SFA) levels were detected in D1D3 groups, while high abdominal muscle SFA levels were detected in D2 and D3 groups. Moreover, although the texture properties (tenderness, hardness, springiness, chewiness, gumminess, and cohesiveness) and edible quality (cooked meat rate and water holding capacity) of muscle showed no significant difference among four groups (P>0.05), numeric values of muscle texture in T. ovatus in D4 were higher than those in diet D1. These results indicate that compound oil and lowfish meal diets exhibit the same growthpromoting effect on Trachinotus ovatus as control diets (containing fish oil and 20 % fish meal), and also is beneficial to improving hepatic health, muscle quality, which can be widely applied in the culture of T. ovatus. The results obtained here lay foundation for the application of highefficiency and low fish meal diets in aquaculture.〖HJ〗  Keywords:  Trachinotus ovatus; compound oil; low fish meal feed; growth performance; muscle quality Related Articles | Metrics

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Effects of hypoxia and reoxygenation on antioxidation, respiratory metabolism and tissue structure of Marsupenaeus japonicus 2023, 45(2): 150.  Abstract ( 165 )   PDF (2284KB) ( 429 )   Effects of hypoxia and reoxygenation on antioxidation, respiratory  metabolism and tissue structure of Marsupenaeus japonicus ZHAO Sizhe1,6， HUA Songsong1， LI Yongchuang1， JIANG Haiyi1，  ZHANG Qingqi5， WANG Panpan1,2,3， GAO Huan1,2,3,4， YAN Binlun1,2,3,4 (1. Jiangsu Key Laboratory of Marine Biotechnology, College of Marine Science and Fisheries, Jiangsu Ocean  University, Lianyungang Jiangsu222005, China; 2. CoInnovation Center of Jiangsu Marine Bioindustry Technology,  Huaihai Institute of Technology, Lianyungang Jiangsu222005, China; 3. Jiangsu Provincial Infrastructure for  Conservation and Utilization of Agricultural Germplasm, Nanjing210014, China; 4. Jiangsu Institute of  Marine Resources Development, Lianyungang Jiangsu222005, China; 5. Lianyungang Qiming Aquatic Products Co.,  Ltd., Lianyungang Jiangsu222005, China; 6. Jiangsu Haorun Biological Industry  Group Co., Ltd., Taizhou Jiangsu225300, China) Abstract: As one of the necessary factors for the survival of aquatic animals, dissolved oxygen (DO) plays an important role in growth, development and reproduction. Human activities, global warming, water eutrophication and other phenomena have led to the formation of “low oxygen zones” in the ocean, which have seriously damaged the marine ecological environment and endangered the health of aquatic animals. At the same time, in today’s highdensity breeding mode, excessive breeding density and excessive feed feeding are easy to cause transient or persistent hypoxia in the water body. However, relying on the traditional aeration and aeration methods alone can only solve the problem fundamentally and increase the cost of breeding. And with the development of society and the continuous improvement of human living standards, people’s demand for fresh aquatic products is increasing day by day. In the process of transportation, hypoxia is very likely to occur, which will make aquatic animals have a stress response and eventually lead to death, resulting in serious economic losses. Therefore, studying the effects of hypoxic stress on aquaculture species is very necessary to guide the healthy farming and transportation of aquatic animals. Generally speaking, we refer to the water body with dissolved oxygen content below 2 mg· L-1 as hypoxic water body, and in normal water body, the dissolved oxygen content of lower layer water is often the lowest. Marsupenaeus japonicus is an important economically cultured shrimp in China. Compared with Litopenaeus vannamei, the yield per unit area of M. japonicus has always been at a low level. The reason is that its habits of burrowing sand and other benthic lives restrict its highdensity cultivation. The lower dissolved oxygen content in the bottom water will not only affect the survival rate of its breeding, but also affect the growth rate and breeding density to a certain extent. Therefore, in order to explain the effects of hypoxia reoxygenation process on the physiology of M. japonicus, this study took M. japonicus as the research object, carried out an acute hypoxia reoxygenation stress experiment, measured the changes of antioxidant enzymes(CAT,GSHPX,SOD) and respiratory metabolic enzymes(PK,PFK,SDH,HK) in the hepatopancreas, gills and muscle tissues of M. japonicus at different time points, and observed the changes of body tissue structure. In this experiment, healthy and vigorous M. japonicus with an average body weight of (0.80±0.06) g and an average body length of (4.7±0.2) cm was selected for temporary culture for 3 days at (25.0±0.3) ℃, with a salinity of 28.0±0.5, pH of 8.0 ± 0.2. During the temporary culture, oxygen was continuously charged to maintain the DO content at (6.7 ± 0.2) mg· L-1. After the temporary culture, 100 shrimps with similar size and good vitality were selected and distributed evenly into 5 cultivation tanks (60 L, 50 cm × 40 cm × 30 cm) for experiments. The experiment was conducted in the control group (0 h) and treatment groups. The DO content in the water of the control group was (6.7 ± 0.2) mg· L-1. The treatment group included two stages: hypoxia (024 h) and reoxygenation (2436 h). In the hypoxia stage, DO content was reduced by adding Na2SO3, DO content was reduced to (1.6 ± 0.2) mg· L-1 within 30 min, and was restored to (6.7 ± 0.2) mg· L-1 by continuous aeration in the reoxygenation stage. The safety and stability of the hypoxic treatment with Na2SO3 was proved by preexperiment before the experiment. Na2SO3 was added to the water before the experiment officially started, and the experiment started immediately when the DO content dropped to (1.6 ± 0.2) mg· L-1, and DO content was detected every 30 min, and DO level of water body was maintained by aeration and adding Na2SO3. After the start of the experiment, 9 shrimps were randomly selected at each time point of 0, 3, 6, 9, 12, 24, 36 h, and the hepatopancreas, muscle and gill tissues were collected for antioxidant and respiratory metabolism. The hepatopancreas and gill tissues of 3 shrimps were taken at 0, 24, 36 h for section observation. The results showed that the antioxidant capacity of M. japonicus had significant changes at different time points (P<0.05). CAT, GSHPX, SOD activity and MDA content in hepatopancreas tissues in hypoxia stage showed a trend of first rising and then declining, and their activities decreased to the lowest level in 24 h, while the activities of antioxidant enzymes and MDA content in reoxygenation stage showed an upward trend. In muscle and gill tissue, GSHPX, SOD activity and MDA content increased first and then decreased with continuous hypoxia, while CAT activity continued to decrease. During the reoxygenation stage, the activities of various enzymes and the content of MDA increased significantly (P<0.05). The effect of hypoxiareoxygenation on the respiration and metabolism of M. japonicus was also significant (P<0.05). The activities of PFK and HK in the hepatopancreas and gill tissues first increased and then decreased with the continuous hypoxia, while the activities of SDH decreased significantly. In muscle tissue, the activities of PFK, HK, SDH and PK all showed a downward trend with the continuous hypoxia, and reached the lowest value at 24 h. During the reoxygenation stage, the activities of PFK, HK, SDH and PK in hepatopancreas and gill tissues all showed an upward trend, while PFK in muscle tissue decreased significantly (P<0.05). Under hypoxic stress, LD content increased significantly in all tissues (P<0.05), and decreased significantly in the reoxygenation stage (P<0.05). It can be seen from the results of tissue sections that with the continuous hypoxia, the hepatopancreas basement membrane is damaged, the volume of transport vacuoles significantly increases, the lumen is deformed, the shape is distorted and irregular, and there are significant granular substances in the lumen, the number of storage cells is significantly reduced, and the hepatopancreas structure is further damaged after reoxygenation. At the same time, the gill tissue structure is damaged under hypoxia: the gill filament is bent and swollen, the cuticle is broken, the secondary lamella is swollen, the epithelial cells are partially shed and swollen, and the lymphocytes are arranged loosely and disorderly. The damage of the gill tissue structure is improved after reoxygenation. By exploring the adaptation and regulation mechanism of M. japonicus to hypoxia stress, this study will help in providing some guidance and suggestions for the culture and management strategy of M. japonicus, improving the survival rate and culture density of M. japonicus, and pointing out the direction for breeding new varieties resistant to hypoxia in the future. Keywords: Marsupenaeus japonicus；hypoxia stress；reoxygenation；enzyme activity；tissue structure Related Articles | Metrics

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Effects of salinity stress on survival, antioxidant enzymes and Na+/ K+-ATPase activities of Moerella iridescens 2023, 45(2): 162.  Abstract ( 148 )   PDF (991KB) ( 427 )   Effects of salinity stress on survival, antioxidant enzymes and  Na+/ K+ATPase activities of Moerella iridescens PEI Ruihua1,2, ZHENG Ziyao1,2, ZHANG Nuo1,2, LIU Qigen1,2, CHEN Liping1,2, HU Zhongjun1,2 （1. Key Laboratory of Freshwater Aquatic Genetic Resources of Ministry of Agriculture and  Rural Affairs, Shanghai Ocean University, Shanghai201306, China； 2. Centre for Research on  Environmental Ecology and Fish Nutrition (CREEFN) of the Ministry of Agriculture and  Rural Affairs, Shanghai Ocean University，Shanghai201306, China） Abstract: Salinity is an important ecological factor relative to the survival, reproduction, growth, and development of aquatic life forms through influencing the energy consumption in the process of osmotic regulation and antioxidant enzyme activity of animal’s organism. The salinity of estuary changes drastically, which will exert a great physiological stress on shellfish with limited migration ability. The sodiumpotassium ATP enzyme (Na+/ K+ATPase) is an important dynamic component of sodiumpotassium pump, and its activity is often used as an important indicator of osmotic regulation ability in animals. Free radical scavenger enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSHPx) are important members of the antioxidant enzyme system and are effective indicators to assess the effect of the environment on life form. Rainbow clam (Moerella iridescens) is an intertidal shellfish with high economical value. Historically, it was a dominant species in intertidal zone of the Yangtze River Estuary. Moerella iridescens is required to be protected urgently for its sharp decline in population size and drastic contraction in distribution area under multiple environmental stresses. However, the salinity in estuary fluctuates largely. Shellfishes inhabiting in estuaries often regulate body functions to adapt to environmental changes. Therefore, it has important scientific significance and application value for protection and rearing of Moerella iridescens to reveal its adaptation to salinity variation and its regulation mechanism. In present study, acute stress experiments were carried out to explore the adaptability to salinity and regulation mechanism of Moerella iridescens, in which the mortality rate and activities of Na+/ K+ATPase and three antioxidant enzymes were measured under different salinity gradients and exposure durations. Moerella iridescens was purchased in the aquatic product market of Luchao Port, Pudong New Area, Shanghai. Healthy and vigorous experimental clams, with (17.37±0.36) mm of average shell length, (11.49±0.26) mm of shell height, (5.23±0.12) mm of shell width, and (0.52±0.02) g of wet mass, were selected and kept in a blue plastic box in Shanghai Ocean University with continuous aeration. During temporary culturing, the water, made of sea crystal and aerated tap water, was changed every day and Moerella iridescens was fed Chaetoceros sp. at 1.0×105 cell·mL-1. In the acute salinity stress experiment, the mortality process within 96 h was observed at 24 h interval when they were exposed to water with 10 salinity gradients ranging from 5 to 50 set by the equal logarithmic spacing method, including salinity 50, 39, 30, 23, 18, 14, 11, 8, 6, 5. The activities of SOD, CAT, GSHPx and Na+/ K+ATPase in gill and digestive glands were measured at 0, 24 , 48 , 72, 96 h when they were exposed to water with sanilities of 6, 12, 18, 24, 30. The total protein was determined by Coomasiland method, and the SOD, CAT, GSHPx and Na+/ K+ATPase were determined. The oneway analysis of variance (ANOVA) was used to test the effect of salinity and exposure time on the activities of various enzymes, Duncan’s multiple comparison was used to determine significant differences between the treatment groups, and P<0.05 was used as the significant level of difference. The results showed that the shell color of Moerella iridescens changed to pink in water with salinity of 8 to 18, and they were sensitive to the external stimuli of water pipes and axe feet. However, in the low salinity water with salinity of 5 and high salinity water with salinity of 50, the shell of Moerella iridescens became white, and the water pipes and axe feet responded slowly to external stimuli. The mortality rates followed a Ushaped curve at 96 h of exposure, no death was observed in the experimental groups of salinity 8, 11, 14 and 18; with increasing salinity, the mortality rates declined at salinities below 8(8.3% and 1.7% of mortality rate for salinity 5 and 6, respectively) and increased at salinities above 18(3.3%, 6.7%, 43.3%, and 100% of mortality rate for salinity 23, 30, 39, 50, respectively). Salinity and exposure duration both had significant effects on the activities of SOD, CAT, GSHPx and Na+/ K+ATPase in gills and digestive glands of Moerella iridescens(P<0.05). With the extension of exposure time under the same salinity stress, SOD, CAT, GSHPx and Na+/ K+ATPase in gills and digestive glands of Moerella iridescens increased first, then decreased, and finally tended to be relatively stable. At the same salinity stress, the activities of SOD, CAT and GSHPx reached the peak at 24 h or 48 h, and that of Na+/ K+ATP reached its peak at 48 h or 72 h. This study suggests that the survival salinity of Moerella iridescens ranges from 6 to 30, and its optimal salinity ranges from 8 to 18. The induction of activity of the above four enzymes of gills and digestive glands of Moerella iridescens under salinity stress is characterized by tissue and organ specificity and temporal sequence, and three antioxidant enzymes respond more quickly to salinity stress than Na+/ K+ATPase. The antioxidant defence mechanism will be damaged and osmotic regulation ability might decrease for Moerella iridescens in extremely high or low salinity environment, which finally leads to die. The salinity ranging from 8 to 18 is suggested in farming practices and conservation actions of Moerella iridescens to decrease the stress of unsuitable salinities on it. This study provides a scientific basis for exploring the adaptability and regulation mechanism to salinity and for its farming and conservation. Keywords: Moerella iridescens; salinity; mortality; antioxidant enzymes; Na+/ K+ATPase activity Related Articles | Metrics

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Effects of 5-HT and thermal stimulation on artificial induction of spawning of Ruditapes philippinarum  2023, 45(2): 172.  Abstract ( 107 )   PDF (1808KB) ( 379 )   Effects of 5-HT and thermal stimulation on artificial induction  of spawning of Ruditapes philippinarum  ZHOU Liqing1,2, WU Lei1,2,3, DONG Zhiguo3, ZHANG Tianshi1,2,  LIU Zhihong1,2, WU Biao1,2, WANG Songlin1,2,3, SUN Xiujun1,2 (1.Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs,  Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao Shandong266071,  China; 2.  Laboratory for Marine Fisheries Science and Food Production Processes, Pilot National Laboratory for  Marine Science and Technology (Qingdao), Qingdao Shandong266071, China; 3. College of Marine Science  and Fisheries, Jiangsu Ocean University, Lianyungang Jiangsu222005, China) Abstract: Manila clam Ruditapes philippinarum belongs to veneridae, which is a mudflat shellfish widely cultivated in the north and south coast of China. In recent years, artificial culture of R. philippinarum has gradually increased year by year, with huge economic benefits. In 2020, the total production of clams in China reached 4.21 million tons, of which R. philippinarum accounted for more than 80%. However, the clam breeding industry is faced with many problems, such as lack of improved varieties and low growth rates, which are coupled with the excessive development and utilization of offshore waters and environmental degradation in the north and south coast of China. Efficient family construction is one of the important methods to evaluate the heritability of shellfish and breeding of new varieties during clam genetics and breeding. In clam hatcheries, sperms and eggs from mature gametes can usually be obtained by artificially induction of male and female parents. However, it is very difficult to obtain highquality sperms and eggs, which are generally essential to be naturally released by artificial induction. Recently, the traditional artificial induction has now faced the problems of unsynchronized, unstable and low emission rate of gametes in the clam industry. The combination of thermal stimulation and 5HT injection may have the potential to improve the induction rates of gametes, which may further improve the synchronization of parental spawning of sperms and eggs. In this study, the clams were treated with three induction methods: 5HT injection combined with thermal stimulation, single thermal stimulation, and single 5HT injection. R.philippinarum in the control group were injected with clean and filtered seawater. After clam shells opened, we placed tweezers between upper and lower shells for the injection. The mature gonads of R. philippinarum were injected with 0.30.4 ml of 2 mmol·L-1 5HT solution using a disposable sterile syringe (1 ml). For thermal stimulation, temperature of seawater rapidly increased from 20 ℃ to 29 ℃. After the treatment, the time for releasing of sperms and eggs was recorded. The measured data were analyzed by oneway ANOVA on SPSS 26 software, which was followed by Duncan multiple comparison method to compare the differences among groups (P<0.05).  In the combined treatment group, the number of eggs released within 10 minutes after injection accounted for 57.45% of the total clams. The number of spawning clams released eggs after 2060 minutes accounted for 19.15% of the total clams. As indicated, the releasing of eggs for clams mainly appeared within 20 minutes in the combined induction group. For single 5HT injection group, 42.86% of the total clams released eggs in 1020 minutes, and the total spawning period lasted for 80 minutes after injection. In the heat stimulation group, only one female clam spawned in 3040 minutes, while no spawning occurred in other time periods. For male clams, the number of spermiation within 1020 minutes accounted for 67.39%91.3% of the total clams in the combined induction group. In the combined induction group, the induction effects on male clams mainly occurred within 20 minutes. In single 5HT injection group, the spermiation rate of male clams after injection of 5HT accounted for 78.57% within 40 minutes, and the spermiation lasted for 80 minutes after injection. In the heat stimulation induction group, there was one male clam spermiation in 2030 minutes after injection, without spermiation in the rest of time. In the control group, one male clam released sperms within 3040 minutes, but there was no spermiation in the rest of time. One way ANOVA showed that there were significant differences in spawning rates among different groups (P<0.01). The maximum proportion of gametes released by the clams treated with 5HT injection and thermal stimulation reached 75.00%. The total spawning ratios of the heat stimulation group and the control group were both less than 5%. As indicated by oneway ANOVA, a significant difference in the spawning rates of males and females was found between the combined induction group and 5HT injection group (P<0.01). The clams from the combined treatment had spawning rates of 50% in males and females. In contrast, 66.67% and 33.33% of clams injected with 5HT alone released sperms and eggs, respectively.  As a result, when 5HT was injected with a concentration of 2 mmol·L-1 into the gonads of clams, the spawning rates of female and male parents were calculated to be 52.4% and 50.0%, respectively. The spawning time after the induction was more than 60 minutes. In contrast, the spawning rates of clams were 80.9% in females and 91.3 % in males within 20 min, which were induced by the combined effects of 5HT injection and thermal stimulation. However, thermal stimulation alone had little induction effects on spawning rates. There was a significant difference in spawning rates among different groups (P<0.01). After the whole experiments, the highest induction rate (85.19%) was found in the combined induction of 5HT injection and thermal stimulation. For 5HT injection or thermal stimulation alone, the induction rate of 5HT injection was 75.0%, while the induction rate of thermal stimulation alone was less than 5.0%. A significant difference was found in the induction rates between the combined treatment and single injection of 5HT (P<0.01). Therefore, our present findings reveal that the combined treatment of thermal stimulation and 5HT can effectively induce spawning of clams. Thermal stimulation can effectively shorten the induction time of 5HT, which has the advantages of high efficiency and strong synchronization of artificial induction. For male and female parents, 5HT injection induces a relatively high spawning rates of eggs from female parents than those of sperms from male parents. The combined treatment of 5HT injection and thermal stimulation is a good strategy for the rapid and efficient method for clam spawning, which will provide foundational basis and technical support for spawning induction and genetic improvement of clams and other shellfish. Keywords: Ruditapes philippinarum; spawning induction; thermal stimulation; 5hydroxytryptamine Related Articles | Metrics

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Anesthetic effects of eugenol and MS-222 on Trachidermus fasciatus 2023, 45(2): 181.  Abstract ( 130 )   PDF (1537KB) ( 382 )   Anesthetic effects of eugenol and MS-222 on Trachidermus fasciatus HU Wangjiao1,2， WANG Cuihua1,2， FENG Guangpeng1,2， ZHUANG Ping2， ZHENG Yueping3，JI Qiang4 (1. College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China; 2. Shanghai Yangtze  Estuary Fishery Resources Proliferation and Ecological Restoration Engineering Technology Research Center, East China  Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China; 3. Shanghai Aquatic  Wildlife Conservation and Research Center, Shanghai202162, China; 4. Shanghai Songjiang District Aquatic  Technology Promotion Station, Shanghai201669, China) Abstract: The main purpose of this study is to explore the anesthetic effect of eugenol and MS222 on Trachidermus fasciatus. T. fasciatus is a kind of small benthic, carnivorous, wide temperature and wide salinity migratory fish, whose resources have collapsed in recent years since the 1980s. It was listed as an endangered species in China Red Data Book of Endangered Animals in 1998. Enhancement and release are considered to be important and effective measures for ecological restoration and resource conservation. As the secondary protected aquatic wildlife in China, a lot of T. fasciatus enhancement and releasing has been carried out by relevant departments in recent years. However, some activities such as marking and transportation may cause stress response and damage to the fish, which in turn may reduce the survival rate of T. fasciatus in the process of enhancement and releasing. Anaesthesia is one of the most important means to reduce fish stress and improve survival rates in the releasing. The two most commonly used fish anaesthetics in China are eugenol and MS222, which are generally considered to be safe and effective anaesthetics in aquatic animals, and they have been widely used throughout the world. At present, eugenol and MS222 have been used for anesthesia in numerous fish species at home and abroad, but no relevant studies on their anesthetic effects on T. fasciatus have been reported. This study was conducted to compare the anaesthetic effects of different mass concentrations of eugenol and MS222 on T. fasciatus to provide scientific reference for aquaculture production and releasing of T. fasciatus. Three different anesthesia experiments were designed by immersion for this experiment. The specific experimental approaches were as follows: 1) Record the final anesthesia degree and recovery status of the fish under different concentrations of eugenol and MS222 anesthesia; 2) Observe and record the time when T. fasciatus entered each anesthesia stage and the time of the recovery stage during the recovery process under two different anaesthetics, with different concentration gradients; 3) The highdefinition shooting was used to measure the respiratory rate of T. fasciatus at different concentrations of two anaesthetics for 30 s, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min and 7 min. 4) The oxygen consumption rate of T. fasciatus was determined by closed hydrostatic respirometry at 5 mg·L-1 and 10 mg·L-1eugenol concentrations and 40 mg·L-1and 50 mg·L-1 MS222 concentrations. The hydrostatic test was used to analyze the anesthetic effect of two commonly used fishery anesthetics, eugenol (5, 10, 20, 40, 80, 120 mg·L-1) and MS222 (40, 50, 60, 75, 100, 200 mg·L-1), on T. fasciatus with body weight of (13.78 ± 3.15) g. The results were as follows: 1) With the increase of the concentrations of two anesthetics, the anesthesia time of T. fasciatus was gradually shortened and the recovery time was prolonged; 2) Under the experimental conditions, the optimum anesthetic concentration of eugenol and MS222 were 4080 mg·L-1 and 60 mg·L-1, respectively; 3) At low concentration of anesthetics, the oxygen consumption rate of T. fasciatus in 10 mg·L-1 eugenol was significantly lower than that of the control group (P<0.05), suggesting that 10 mg·L-1 eugenol might be a suitable transport concentration for T. fasciatus; 4) Compared with the survival rate, the time of entering anesthesia and resuscitation, eugenol was more suitable for T. fasciatus, and 4080 mg·L-1 eugenol was recommended to use for the anesthetic of T. fasciatus. In this study, both anesthetics could make T. fasciatus enter different levels of anesthesia. By comparing the anaesthesia time, recovery time and mortality of T. fasciatus, it was found that the effective concentration of eugenol ranged from 20  mg·L-1 to 80 mg·L-1 and the optimum concentration of MS222 was 60 mg·L-1 at water temperature of (15 ± 3) ℃, which was different from many fishes reported in the literature. It showed that the anesthetic effect was not only related to factors such as the type and concentration of anesthetic and the size of the test fish, but there were also significant differences in the sensitivity of different fish species to the anesthetic. In this study, eugenol showed a wider range of safe concentrations and greater tolerance to anaesthesia than MS222. In addition, it was found that the respiratory rate of the fish decreased gradually as the anaesthetic level increased until the respiration stopped. The difference in the effect of two anaesthetics on the respiratory rate of T. fasciatus might be due to different sensitivities of the fish to different anaesthetics, and the exact mechanism of action needed to be further investigated. In the present study, the oxygen consumption rate of T. fasciatus decreased as the concentration of two anesthetics increased, and the oxygen consumption decreased. In 510 mg·L-1 eugenol treatment, T. fasciatus could enter and remain in sedation or light anaesthesia with slower gill opening and closing, lower respiratory rate and lower oxygen consumption rate. The difference in oxygen consumption rate was significant compared to the control group (P<0.05), which might have some significance in guiding the transport process of T. fasciatus especially at 10 mg·L-1 eugenol. However, the oxygen consumption rate of the fish at 4050 mg·L-1 MS222 concentrations did not differ significantly from the control group. Therefore, 10 mg·L-1 eugenol was recommended for prolonged handling or transport of T. fasciatus, but this still needed to be justified by further transport practice. Eugenol is cheap and readily available, and has advantages such as fast anesthesia, high recovery rate and wide safety boundaries, which can be used as a suitable anesthetic for T. fasciatus. In this study, the effective anesthetic concentration of eugenol for T. fasciatus is 2080 mg·L-1, and it is recommended to use 4080 mg·L-1 for shortterm operation in production, and should not exceed 80 mg·L-1. 60 mg·L-1 MS222 can make T. fasciatus enter anaesthesia, but the time to enter anaesthesia is longer; 75100 mg·L-1 MS222 can enter anesthesia in a shorter period of time, but the mortality rate is higher and the safety boundary is narrow. Therefore, 4080 mg·L-1 eugenol is recommended for the anesthesia of T. fasciatus in practice, and MS222 may not be suitable as an anesthetic agent for T. fasciatus compared to eugenol. Keywords: anesthetic; eugenol; MS222; Trachidermus fasciatus; oxygen consumption rate Related Articles | Metrics

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Pharmacokinetics and tissue elimination of enrofloxacin in Penaeus monodon after oral administration 2023, 45(2): 191.  Abstract ( 114 )   PDF (1830KB) ( 486 )   Pharmacokinetics and tissue elimination of enrofloxacin in  Penaeus monodon after oral administration FAN Peili1，2，WANG Yuan2，ZHAO Shu2，LI Xinshu1， WANG Hongbin1，LING Hai2, LI Chuanbu2, FANG Wenhong2 （1. School of Marine Science and Fisheries, Jiangsu Ocean University， Lianyungang Jiangsu222005, China;  2. Key Laboratory of East China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural  Affairs; East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China） Abstract: Shrimp is extensively farmed all over the world and provides highquality animal protein in human diet. But like most other farmed aquatic animals, diseases, especially caused by bacteria, frequently break out in Penaeus monodon culture industry with the development of intensive aquaculture, and antimicrobial drugs play the most effective and direct role. Enrofloxacin (ENR) is a quinolone carboxylic acid derivative with antimicrobial action, which is bactericidal through inhibition of DNAgyrase. Enrofloxacin is effective against gramnegative and grampositive bacteria. Enrofloxacin is a special drug for animals and is widely used in the prevention and treatment of animal infectious diseases. The main metabolite of enrofloxacin in animals is ciprofloxacin, which is also allowed to be used in aquaculture in China. At present, enrofloxacin has been studied in aquatic animals such as fish, shrimp and crab, but there are species differences in drug metabolism in different animals. At present, there are only studies on the effects of enrofloxacin on the oxidative stress of hepatopancreas and gills of Penaeus monodon, but the metabolism and elimination of enrofloxacin and ciprofloxacin in vivo have not been reported. In order to guide the rational application of enrofloxacin for the prevention and control of bacterial diseases in Penaeus monodon, high performance liquid chromatography (HPLC) was used to study the pharmacokinetics and tissue distribution of enrofloxacin and its metabolite ciprofloxacin in Penaeus monodon. The dosage of enrofloxacin (30 mg·kg -1) was orally administrated to Penaeus monodon in seawater (salinity of 33) at temperature (28.0 ± 1.0) ℃. Pharmacokinetic noncompartmental modeling of drug concentrationtime data were performed using Drug and Statistics Software DAS Version 2.0. The pharmacokinetic parameters were analyzed based on statistical moment theory for the hemolymph and tissues concentrationtime data of enrofloxacin and its active metabolite ciprofloxacin. This is the first study on the pharmacokinetics and tissue disposition of enrofloxacin and its metabolite ciprofloxacin in Penaeus monodon. The concentrationtime curve of enrofloxacin in the hemolymph of Penaeus monodon was best fitted to twocompartment open model with firstorder absorption. Tmax and Cmax represented the extent of drug absorption. The former corresponded to the absorption rate, while the latter corresponded to the absorption magnitude. The peak time (Tmax) of enrofloxacin in hemolymph, muscle and hepatopancreas were 1 h, 2 h and 2 h, respectively, Cmax were 17.82 mg·L -1, 5.02 mg·kg -1 and 96.75 mg·kg -1, respectively. The AUC0-t and Vz represented the extent of drug distribution. It was generally believed that the higher the AUC value was, the more drugs penetrated into the tissue and the more widely distributed they were. The critical value was usually (0.81.0) L·kg-1: when Vz was close to (0.81.0) L·kg-1, it indicated that the drug was widely and evenly distributed in vivo. When Vz was greater than 1 L·kg-1, it showed that the drug was widely distributed in vivo or histone was highly bound to the drug. The AUC0-t of enrofloxacin in hemolymph, muscle and hepatopancreas were 187.34 mg·(L·h)-1, 132.15 mg·(kg·h)-1 and 1298.32 mg·(kg·h)-1, respectively, and the Vz of enrofloxacin in hemolymph was 2.63 L·kg-1. The t1/2z and CLz were the most important pharmacological parameters and were related to drug elimination. The t1/2z of enrofloxacin in hemolymph, muscle and hepatopancreas were 17.12 h, 72.31 h and 37.78 h, respectively, and the CLz were 0.11 L·(h·kg)-1, 0.21 kg·(h·kg)-1 and 0.023 kg·(h·kg)-1, respectively. It was obvious that enrofloxacin was rapidly absorbed, distributed and eliminated in Penaeus monodon. Ciprofloxacin, the metabolite of enrofloxacin, was detected in hemolymph, muscle and hepatopancreas, but the levels were low. The Cmax of ciprofloxacin in hemolymph, muscle and hepatopancreas were 1.07 mg·L-1, 0.77 mg·kg -1 and 1.40 mg·kg-1, respectively, which were about 6.00%, 15.30% and 1.45% of enrofloxacin in all three tissues, respectively. The AUC0-t of ciprofloxacin in hemolymph, muscle and hepatopancreas were 18.81 mg·(L·h)-1, 27.40 mg·(kg·h)-1 and 36.53 mg·(kg·h)-1, respectively. The ratios of the area under the curve of ciprofloxacin and enrofloxacin (AUCCIP/AUCENR) were 10.04 %, 20.73 % and 2.81 %, respectively, which was higher than that of Scylla serrata, Fenneropenaeus chinensis, and Paralichthys olivaceus, but significantly less than that of llamas, pigs and horses. It showed that that an intraspecies variability existed in the metabolite pathway among aquatic animals. In the present study enrofloxacin played the main role in Penaeus monodon. PKPD modeling was a significant strategy for providing an optimal dose regimen to prevent resistance problems. The model could establish the relationship between drug concentration, antimicrobial effect and time. Based on the scientific calculation, the model could provide the optimal dose regimen and dose interval. The most commonly used PKPD indices for enrofloxacin were the area under the concentrationversus time curve (AUC)/minimum inhibitory concentration (MIC) and peak plasma concentration (Cmax)/MIC. For concentrationdependent quinolone drugs enrofloxacin, Cmax/MIC=810, AUC/MIC=100, which could achieve good clinical treatment effect. Vibrio parahaemolyticus is an important pathogenic bacterium in mariculture animals and also an important pathogenic pathogen to shrimp. Referring to MIC of 36 strains of Vibrio parahemolyticus isolated from shrimp by Wei Wenjuan, the MIC90 was 2 mg·L-1, enrofloxacin was orally administered to Penaeus monodon at the dosage of 30 mg·kg -1, the estimated Cmax/MIC90 and AUC0-t/MIC90 were 8.91 and 93.67, respectively, which had good efficacy on bacterial diseases caused by Vibrio. As consumers pay more attention to food safety, drug residues in animalderived food have attracted much attention. Drug withdrawal period is the basis of scientific and rational drug use and has become an important means to control drug residues. According to the guidance published by China and European Union, the marker residue of ENR in fish is the sum of ENR and CIP with an MRL of 100 μg·kg -1, and the related tissue is muscle and adherent skin. The withdrawal time of enrofloxacin in Penaeus monodon was estimated to be 372.5 h (about 16 d) by WT1.4 software. The results can provide reference for scientific and rational use of enrofloxacin in Penaeus monodon. Keywords: Penaeus monodon; enrofloxacin; pharmacokinetics; withdrawal time; oral administration Related Articles | Metrics

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Niche and interspecies association of shrimps in spring and autumn in the east area of Zhoushan Islands 2023, 45(2): 202.  Abstract ( 124 )   PDF (1989KB) ( 427 )   Niche and interspecies association of shrimps in spring and  autumn in the east area of Zhoushan Islands JIANG Xinqin, NIU Weizhen, ZHENG Ji, XU Yongjiu,  ZHANG Peiyi, LIU Kun, YU Nanjing, YU Cungen （College of Fisheries, Zhejiang Ocean University, Zhoushan Zhejiang316022, China） Abstract: In order to understand the competitiveness and utilization status of major shrimps for habitat resources in Zhoushan sea area, this study analyzed shrimp data obtained from the bottom trawl survey of fishery resources conducted in April (spring) and October (autumn) 2018 in waters east of Zhoushan Islands. Niche width, niche overlap, cluster analysis, Pearson correlation test, Spearman rank correlation test, Ochiai index, Dice index and other measures were used to analyze the niche and interspecies relationship among major shrimp species. In this survey, shrimp species occurring in both two voyages were defined as major shrimp species. Pinkas index relative importance(IRI) was used to determine dominant species of major shrimps. Shrimps with IRI≥1 000 were defined as dominant species, and IRI<100<1000 were defined as important species. The results showed that: A total of 32 shrimp species were captured and identified, belonging to 21 genera and 10 families. The dominant species were Metapenaeopsis Barbata, Metapenaeopsis Dalei, Parapenaeopsis hardwickii and Solenocera crassicornis and their IRI were 2 547.26, 2 835.16, 4 507.25 and 1 753.93, respectively. A total of 19 shrimp species were found in both voyages. The top 3 shrimp species were Penaeus chinensis, Parapenaeopsis tenella and Penaeus harteni, with niche widths of 2.41, 2.38 and 2.25, respectively. Aegaeon rathbuni had the lowest niche width, which was 0.53. According to niche width cluster analysis, the main shrimp species could be divided into 3 groups: wide niche species (niche width value was between 2.00 and 2.50), middle niche species (niche width value between 1.00 and 2.00) and narrow niche species (niche width value less than 1.00). The similarity test was carried out by results of the cluster analysis. The results showed that R=0.943,P=0.001<1%, indicating that the grouping results were reasonable. Main shrimp species niche overlap value ranged from 0 to 0.99, 11 shrimps with overlap value of 0, 6 higher than 0.90, The highest overlap value was 0.99, and the niche overlap value between Aegaeon rathbuni and Processa japonica was significantly different, indicating that there were differences in similarity degree of species in resource utilization. VR (variance ratio) method was used to calculate the overall correlation between the main shrimp species. VR value was 2.23>1, indicating that there was a positive correlation between the main shrimp species. After analysis by Pearson correlation test and Spearman rank correlation test, the results of the two correlation tests were not completely equal, but both showed significant positive correlation among populations of main shrimps, which was consistent with the results of the overall correlation test.Ochiai index and Dice index were used to measure the degree of interspecific association of major shrimp species. 115 pairs with OI correlation index greater than 0.5, accounting for 67.3% of species logarithms, and 95 pairs with DI correlation index greater than 0.5, accounting for 55.6% of species logarithms. The species logarithms with both indices greater than 0.5 were far more than 50%. The overall results tended to be positively correlated, indicating strong interspecific association. The niche width of shrimp in the study area was segmented obviously. The high niche width was typical in Solenocera crassicornis and Parapenaeopsis tenella. Both Solenocera crassicornis and Parapenaeopsis tenella were dominant species, indicating that they were evenly distributed and had a large range of activities, and had strong ability to use resources and adapt to environment. The low niche width values might be related to the location of survey stations, the abundance and occurrence of species, and might also be closely related to marine environmental degradation. The results of this survey showed that there were great differences in the overlap value and degree among main shrimps. The niche width values of Solenocera crassicornis (2.41) and Parapenaeopsis tenella (2.38) were large and had a high degree of overlap with each other, indicating that these species pairs were similar in their ability to utilize habitat resources and occupied similar resource sites.In general, species with smaller niche width values also had smaller niche overlap values with other species, which might be due to their low utilization ability of habitat resources and relatively weak competition between species pairs. Meanwhile, among shrimps obtained in this survey, shrimps with narrow niche width did not necessarily have low overlap value with shrimps. For example, shrimps with the smallest niche width had high overlap value with other species, especially shrimps with Aegaeon rathbuni, which reached 0.99, it might be caused by the high station overlap rate between them.There was a significant positive correlation between the overall association(VR) of major shrimp species, which indicated that there was a phenomenon of interdependence among shrimp species and they had the same or similar needs for habitat resources. Meanwhile, the community structure in this area was stable and showed a positive succession trend. This might be due to the similarity of adaptation or utilization of nonrestrictive factors in the habitat (water temperature, salinity, ocean current, etc.), or to the strong association between the dominant species.Spearman rank correlation test was relatively higher than Pearson correlation test in significant and extremely significant logarithms of shrimp species. The reason may be that Pearson correlation test is a parameter test method, which requires that species must follow a continuous normal distribution, while shrimps in the sea area are distributed in clusters. Spearman rank correlation coefficient test is a nonparametric test method, and there is no requirement for the distribution form of penaeus. Therefore, Spearman rank correlation coefficient test has higher reliability and sensitivity. The results of this study showed that shrimp species pairs with significant and extremely significant positive correlation in correlation test also had larger niche width overlap value and stronger interspecies association. However, niche overlap and linkage analysis could not fully reveal the internal mechanism of the association between species in a community. In order to fully reflect the relationship between niche overlap and interspecific linkage, it is necessary to select appropriate measurement methods in subsequent investigations and comprehensively consider the changes of niche overlap in multiple dimensions. Keywords: shrimps; niche breadth; niche overlap; interspecific association; sea area to the east of Zhoushan Islands Related Articles | Metrics

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On the influential factors in the operation form of bottom-set gillnet based on model tests 2023, 45(2): 214.  Abstract ( 153 )   PDF (5798KB) ( 456 )   On the influential factors in the operation form  of bottom-set gillnet based on model tests GUO Shaojian1, XU Zimu1, YE Xuchang1, 2, 3,  ZHANG Jian1, 2, 3, WANG Yucheng1, ZHOU Cheng1, 2, 3 （1.College of Marine Sciences, Shanghai Ocean University, Shanghai201306, China; 2. National Engineering  Research Center for Oceanic Fisheries, Shanghai201306, China; 3. Key Laboratory of Sustainable Exploitation  of Oceanic Fisheries Resources, Ministry of Education, Shanghai201306, China） Abstract: Bottomset gillnet has the characteristics of harvesting a variety of species, high economic benefits, high sizeselectivity and poor speciesselectivity. The hydrodynamic behavior of bottomset gillnet under fishing operation are dynamically changed in response to combined effects of external forces from wave and current, and catch impact etc., which results in reduced fishing efficiency, fishing gear selectivity and security, and subsequently the remnant netting forms “ghost fishing”. The main internal factors affecting the fishing efficiency and selectivity of gillnet gear include mesh and twine size, working height of gillnet, twine material and hanging ratio, In addition, in the working process, due to the influence of external forces such as waves and streams and the interaction with fish behavior, the form and structure of gillnets change, fishing performance decreases, and selectivity changes. For the intention of further understanding the hydrodynamic behavior and geometry deformation under fishing operation, this study, on the basis of hydrodynamic experiment of polyethylene (PE) and nylon (PA) gillnets in the uniform current, investigated the effect of current velocity, solidity ratio and 90° turned mesh on the working height and shape characteristics of bottomget gillnet, and developed the empirical formulas of deformation degree (k) of PE and PA gillnets. The results showed that the working height of gillnet was negatively correlated with the current velocity, and 96.5%, 69.3%, 43.9% and 29.9% of the initial height under the still water were achieved under current velocity of 0.2, 0.4, 0.6， 0.8 m·s-1, respectively; hanging angle in the lowerhalf part of the gillnet increased with the current velocity.When V= 0 m·s-1, the gillnet was stretched vertically in the water, the gillnet mesh was in the form of a high middle and low on both sides, the headline was inverted catenatelike. With the increase of current velocity, the gillnet gradually shifted backwards and downwards, the projection area of the gillnet in the YZ plane gradually became smaller, the projection area in the XY plane gradually increased, the projection area of the mesh in the YZ plane decreased, the curvature of the left and right siderope got larger and larger, and more folds appeared with it. When the current velocity reached 0.8 m·s-1, the lower part of the gillnet was close to the bottom surface of the tank. The twine material had little influence on the working height of gillnet, but had a significant impact on the expansion form of the bar. The height of the two kinds of twine materials (PE and PA) gillnets was almost the same under the same current velocity, but PA gillnets at different current velocities had a larger projection area in the XY plane, the overall form was more uniform, the lower part of the netting was not wrinkled, and the mesh was always maintained more uniform expansion. Under T0 and T90 assembly, the working height and uniformity of gillnets at different current velocities varied greatly. In still water and when V= 0.2 m·s-1, the working height of T0 gillnet was significantly higher than that of T90 gillnet, and the M4 Zaxis coordinates of T0 gillnet tracer point were 5.1 cm and 9.0 cm higher than those of T90 gillnet, respectively, while the M3 Zaxis coordinates of the center point of T90 gillnet were 8.0 cm and 5.0 cm higher than those of T0 gillnet. When the current velocity increased, the projection area of T90 gillnet in the YZ plane was significantly larger, the working height of the netting was significantly higher than that of T0 gillnet, and the mesh expansion form was closer to the positive diamond, but at this time, the deformation degree of the lower half of the mesh of the two assembly methods was basically the same. The large solidity ratio not only leads to an increase in the current velocity and resistance through the mesh, but also sometimes changed the current state in the net, affecting the selectivity of fishing gear and quality of the catch. In this study, the form changes of PE and PA gillnets with different solidity ratios showed that under the four sets of current velocity conditions, the working height of gillnets of PE and PA materials was negatively correlated with the solidity ratio, the smaller the solidity ratio, the larger the working height of gillnet, the smaller the degree of deformation, the smaller the projection area of the netting in the XY plane, and the closer the mesh form to positive diamond expansion. Based on the influence of twine diameter, bar length, Reynolds number, on the resistance of the netting, the nonlinear fitting of different materials, solidity ratios and current velocities was obtained, and the expressions of deformation degree k of PE and PA materials were obtained, and according to the characteristics of the expression, the response surfaces of the specific current velocity, bar length and deformation degree k were obtained by response surface analysis method, and the calculated results were compared with the test results. The results showed that at a certain velocity, the longer the bar length, the smaller the twine diameter, and the greater the degree of the gillnet deformation. When the bar length was fixed, the degree of gillnet deformation k was negatively correlated with the current velocities and the twine diameter of netting; when the twine diameter was fixed, the smaller the current velocity, the larger the bar length, and the greater the degree of deformation k. In general, the calculated result was in good agreement with the test result, but the calculated result of the degree of deformation of PA gillnet at low current velocity (V=0.2 m·s-1) was quite different from the experimental test. To sum up, in the traditional gillnet operation, PA material twine is mostly selected, which is conducive to the full expansion of the netting in water. The solidity ratio is the key factor of whether the gillnet can maintain the ideal form in the current, the smaller the solidity ratio, the stronger the water crossing ability, the smaller the resistance in the horizontal direction, the higher the height of the gillnet, and the more the mesh tends to be positive diamond expansion.  Keywords: bottomset gillnet; model test; solidity ratio; hydrodynamic Related Articles | Metrics

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Screening analysis of hidden drugs in fishery nondrugs based on high resolution mass spectrometry 2023, 45(2): 227.  Abstract ( 83 )   PDF (1626KB) ( 414 )   Screening analysis of hidden drugs in fishery non-drugs  based on high resolution mass spectrometry LIU Yangfeng1,2, ZHANG Haiyan2, KONG Cong2, GU Runrun2,  ZHANG Kaiwen1,2, CHEN Gang3, ZHOU Junfang2, SHEN Xiaosheng2 (1. College of Food Science, Shanghai Ocean University, Shanghai201306, China; 2. East China  Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China;  3. Shanghai Jinshan District Aquatic Technology Promotion Station,Shanghai201599, China ) Abstract: Fishery nondrugs for aquaculture are important materials for production. Their quality is related to the sustainable development of aquaculture, as well as to the quality and safety of aquaculture products, food safety and ecological safety. In the long term, the Ministry of Agriculture and Rural Affairs has been paying great attention to the issue of aquaculture with input regulation, strictly adhering to the law for the production, operation and use of related products and other aspects of supervision and law enforcement. In order to evaluate the quality and safety of fishery nondrugs in the process of aquaculture, fishery nondrugs used in aquaculture in Shanghai area were studied in this paper .High resolution mass spectrometry screening technology was used to screen and analyze the hidden drug components of fishery nondrugs in aquaculture farms, fishery drug stores and network platforms in Shanghai, and to explore the harmfulness of pesticides and veterinary drugs in nondrugs fishery inputs to the quality and safety of aquatic products.From April 2020 to August 2020, a total of 300 fishery nondrug samples were collected in seven batches from various aquaculture farms and fishery pharmacies in Shanghai, and online platforms. According to the efficacy of their labels, the nondrugs collected for fishery use could be divided into 7 categories: water quality improver, sediment improver, antidote, microecological agents, impurity removal, growthpromoter agent and pesticide. The results showed that among 300 fishery nondrugs samples, 189 unlabeled drug components were detected in 104 samples, including 15 drug components, and the total screening rate was 34.7%. According to the source of screened drug samples, the detection rate of samples collected from fishery pharmacy was the lowest, 22.5%, followed by aquaculture farms, 25.3%, and network platform was the highest, 72.6%, three times that of the other two sources. Through onthespot visits and investigations, it is found that when farmers buy nonfishery drugs from pharmacies, they need to register their real names online in the pharmacies, and the process of purchasing drugs is also connected with relevant administrative departments, the whole sales process has a good traceability, product quality assurance is relatively good. The network platform purchase is directly through channels like Taobao, which does not need to register the information. The convenience and lower cost makes online purchase more acceptable for purchasers. The unlabeled drug component added in these products was three times the quantity of formal pharmacy, leading to obviously better shortterm use effect. Many farmers choose to buy online fishery nondrugs. However, the longterm use of such products leads to residues in aquatic products exceeding the maximum residue limit and causes pollution of aquaculture environment, further significantly resulting in other increased hazards. Therefore, the supervision of online platforms for the purchase of fishery nondrugs should be further strengthened and improved. According to properties of the detected drugs, there were 6 kinds of pesticides in the 15 kinds of drug components, including prometrazine, simetryne, simazine, carbendazim, trichlorfon and ethoxyquin; 8 kinds of veterinary drugs, including enrofloxacin, mequindox, erythromycin, gatifloxacin, florfenicol, sulfadiazine, ciprofloxacin and trimethoprim; and 1 kind of discontinued drug, pefloxacin. These stealthily added drugs had certain risks of excessive drug residues in aquaculture species and pollution of aquaculture environment. In terms of types of drugs screened out, a certain quantity of hidden drug components were screened out in different categories of nonfishery drugs, but there were great differences in the types of drugs screened out, among which the most hidden drugs were in water quality improvers. The main reason for adding multidrugs was to highlight the efficacy of the products, such as bactericidal, insecticidal, antiviral effects and so on. Pesticides and veterinary drugs were screened out in different categories of fishery  nondrugs, among which water quality improvers, substrate improvers and antidotes were screened out. Compared with other types of nondrugs for fishery use, the proportion of hidden pesticides screened out from the miscellaneous samples was the highest (45%) , and most of the screened pesticides were herbicides and insecticides, the utility model could enhance the impurity removal effect in nondrugs for fishery use. According to the types of drugs detected in the samples, of 104 samples containing hidden drugs, 57 screened out a single drug, 47 screened out 2 and more drugs, 25 screened out 3 and more drugs, 9 screened out 4 and more drugs, 3 screened out 5 and more drugs, and 2 screened out 6 drugs. 87.2% of the hidden drugs were 1010 000 μg·kg-1, of which 117(61.9%) were over 100 μg·kg-1 in 189 items. 10 000 μg·kg-1 or more accounted for 10.1% , and the highest content was 1 093 023 μg·kg-1, which was close to the effective concentration labeled on common veterinary drug product. If farmers use these products, the unintentional drug residue will be caused in aquaculture. While the effective withdrawal period before the sale of aquatic products on the market can not be guaranteed. It will possibly cause the residue exceeding the MRL in farmed aquatic products, resulting in product failure. This shows that the source of fishery nondrugs and the type and content of hidden drugs is one of the main reasons for drug residues in aquaculture aquatic products. The longterm use of such products will not only lead to aquaculture drug resistance and other problems, thus increasing drug residues in aquatic products. Residues of veterinary drugs in aquatic products may cause human poisoning, allergies, increased drug resistance of pathogenic bacteria and even lead to deformity and cancer in serious cases, and do great harm to people’s health. Drug residues can also cause secondary pollution to aquaculture water body and sediment, and cause certain harm risks to the aquaculture ecological environment. Keywords: high resolution mass spectrometry; fishery nondrugs; hidden drugs; screening analysis Related Articles | Metrics

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Research progress on application of AIS data in distant-water fishery 2023, 45(2): 237.  Abstract ( 202 )   PDF (1047KB) ( 434 )   Research progress on application of AIS  data in distant-water fishery XU Zhenqi1, WANG Jintao1,2,3,4,5, LEI Lin1,2,3,4,5, WU Feng1,2,3,4,5, CHEN Xinjun1,2,3,4,5 （ 1. College of Marine Sciences，Shanghai Ocean University，Shanghai201306，China； 2. Key Laboratory of Oceanic  Fisheries Exploration，Ministry of Agriculture and Rural Affairs，Shanghai201306，China；3. National Engineering Research  Center for Oceanic Fisheries，Shanghai201306，China；4. Key Laboratory of Sustainable Exploitation of Oceanic Fisheries  Resources，Ministry of Education，Shanghai201306，China；5. Scientific Observing and Experimental Station of  Oceanic Fishery Resources，Ministry of Agriculture and Rural Affairs，Shanghai201306，China ） Abstract: Pelagic fishery is an important industry of the national economy. Due to the distance from land and port, the lack of effective means of observation and regulation is not conducive to the sustainable development of this industry. Automatic identification system （AIS） is an open data transmission system applied between ship and shore, and between ship and ship. The signals are sent and received in very high frequency （VHF） through transponders, and detailed information such as ship’s movement position is recorded using global positioning system （GPS） receivers, and important information such as ship’s position, speed, heading, ship’s name and call sign can be exchanged automatically. The initial purpose of AIS is to ensure the safety of ship navigation, which is a necessary navigation equipment for modern ships. The data generated by AIS has become an important data source for the study of pelagic fisheries because of its characteristics of wide coverage and high accuracy. This paper clarified the important role of AIS in pelagic fisheries by analyzing the characteristics of AIS data and its processing methods and the development and application of AIS technology at home and abroad. It explains how to extract and process AIS data effectively, including how to handle missing values and filter outliers and store them in an appropriate format, and finally how to apply the processed information to the field of pelagic fisheries through different algorithms and visualization processes. This paper focuses on three main application directions of AIS data in pelagic fisheries and the corresponding research methods. The identification of fishing vessel operation status and central fishing ground forecast are the most applied aspects in the field of pelagic fisheries, including the identification of fishing vessel operation status, calculation of fishing operation intensity, perception of fishing ground exploitation situation and dynamic changes by using the attribute features such as speed and heading in AIS trajectory data, which play an important role in the assessment of fishery resources and marine ecological protection. The monitoring of offshore fishing vessels and illegal fishing behavior is one of the most direct directions of AIS data application. AIS has great potential in monitoring unregulated fishing activities, and the larger and more perfect the amount of AIS data, the more accurate the monitoring of such activities. More and more scholars are exploring the application of AIS data in marine environmental protection and marine habitat management, which provides more tools to utilize and protect marine biodiversity. The application of AIS data is beneficial to improving the efficiency of marine habitat management, and also plays a role in monitoring overfishing in the high seas of pelagic fisheries. Then, we discusses the advantages and disadvantages of each method and its development prospects by comparing the research methods in different application directions. With the continuous progress of marine fisheries disciplines, modern statistics, artificial intelligence, machine learning and data mining and other disciplines and methods, the application models and research methods of AIS in fisheries science are becoming more and more diversified, promoting the progress and development of fisheries science, especially in fishing forecast technology and fishing vessel monitoring. However, there are certain problems and limitations of many methods and models in practical fisheries production applications. Therefore, we conclude with a summary of the important roles played by AIS data in pelagic fisheries applications and make a discussion of the shortcomings and deficiencies of related research methods. And a proposal for the optimization of AIS data applications in pelagic fisheries is presented, which is expected to provide a scientific basis for the sustainable development of pelagic fisheries. In the future, AIS may also solve more challenges including IUU monitoring and marine environmental protection to better serve the global marine fisheries. Keywords: AIS data; pelagic fishery; fishing state; fishery forecast; IUU; marine environment protection Related Articles | Metrics

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Research progress in function, influence factor and application of intestinal flora of shrimp 2023, 45(2): 248.  Abstract ( 138 )   PDF (800KB) ( 435 )   Research progress in function, influence factor and  application of intestinal flora of shrimp DING Lan1, XU Shengnan1, LUO Jinping2, GAO Quanxin2 （1. Bureau of Agriculture and Rural Affairs of Anji County, Huzhou Zhejiang313300, China;  2. College of Life Science, Huzhou University, Huzhou Zhejiang313000, China） Abstract: There are a large number and a wide variety of bacteria in shrimp intestines, which play important roles in nutrient absorption, growth and development and disease defense. Intestinal bacteria are the main members of intestinal microorganisms, which have been found to be closely related to growth stage, individual size and health status of shrimp. Moreover, once the dynamic balance of intestinal flora of shrimp deviates from the normal and healthy range, the shrimp will exhibit metabolic abnormalities and tissue lesions, leading to the invasion of pathogenic microorganisms. With the continuous deepening of research, experts and scholars at home and abroad have begun to explore the unknown functions of shrimp intestinal microflora and made much progress in recent years, mainly involving growth and development, environmental stress, disease occurrence, feed nutrition, and water quality conditions. During the entire development process of shrimp, the structure of intestinal microflora undergoes significant changes. Intestinal microflora can be adjusted based on shrimp feed, feeding patterns, and nutrient requirements for growth and development, so the dynamic balance of symbiosis is more beneficial to both parties, thereby promoting shrimp growth. The abundance of Actinobacteria significantly increases with the extension of culture time of Litopenaeus vannamei, while αProteobacteria showes an opposite trend of change. γProteobacteria is the dominant bacteria in healthy shrimp, accounting for 40% of L. vannamei and 90% of Penaeus monodon. During the early development stage of P. monodon, Proteobacteria dominates, but Actinomycetes becomes the dominant bacteria in the intestinal tract of adult shrimp. γ and α Proteobacteria and Flavobacteria are the dominant microflora of L. vannamei at different stages of early development. During the larval stage of L. vannamei, Vibrionaceae occupies an absolute advantage in the intestinal flora, but in juvenile and adult stages, Rhodobacteraceae gradually replaces Vibrionaceae as the dominant bacteria. In the early stage, the intestinal microflora of shrimp is variable, but in the later stage of development, it is relatively stable. In order to coexist with the host, the intestinal microflora of healthy shrimp regards pathogenic microorganisms as invasive species. Once the balance of intestinal flora changes significantly, harmful microorganisms will seize the opportunity to invade, leading to disease of host. There is a significant correlation between the intestinal microflora structure of shrimp and the outbreak of diseases. After an outbreak of disease, the normal activity of the intestinal microflora of L. vannamei is abnormal and presents a relatively disordered state. In recent years, experts and scholars have proposed the concept of microbiotaforage Z scores (MAZ), which is a time variant index of intestinal microflora based on the age of the host. MAZ is relatively stable in healthy shrimp, but once diseases occur, MAZ will decline sharply. Therefore, analysis of the structure of host intestinal microflora can assess the health level and susceptibility to pathogens. The core microflora of healthy shrimp is generally dominated by the orders Verrucomicrobiales and Alteromonadales, but during the outbreak of disease, the core microflora gradually shifts to a structure with the orders Rhodobacterales, Vibrionales, and Flavobacteria. There is a significant positive correlation between the immune status of shrimp and relative abundance of intestinal core flora. In order to make the dynamic balance of the intestinal flora and its symbiotic state with the host more conducive to adapting to changes in the external environment, the shrimp intestinal flora can be changed according to environmental conditions of water (ammonia nitrogen, water temperature, salinity, pH, etc.). As an important ecological factor, salinity is crucial for the growth of cultured shrimp. The intestinal microflora of L. vannamei is closely related to the salinity of water. In highly saline water, multiple conditional pathogens in the intestinal tract increases, leading to a sharp decline in the health level of the shrimp. With the continuous changes of salinity, conditional pathogenic bacteria increase and beneficial bacteria decrease, indicating that continuous changes in salinity can lead to serious imbalance in the structure of intestinal flora and may lead to intestinal dysfunction. Research on the response mechanism of salinity stress to P. monodon has shown that the abundance of Vibrio in high salinity group is higher than that in low salinity group, while the abundance of Shewanella in low salinity group is higher than that in high salinity group. Based on the theory of coevolution, it can be inferred that the interaction between shrimp and its intestinal flora is formed through longterm coevolution, and this symbiotic mechanism can ensure the colonization and reproduction of intestinal bacteria. In other words, the evolution of shrimp intestinal microflora follows Darwin’s law of evolutionary dynamics, and shrimp host and their intestinal microflora must adapt to each other to survive. Establishing criteria for the intestinal microflora of healthy shrimp at different stages of development will help to assess the health level and development status of shrimp. The growth and development, phenotypic traits, and stress resistance characteristics of shrimp are closely related to the composition and structure of intestinal microflora. Therefore, establishing a relationship model between economic traits and intestinal microflora using bioinformatics, macrogenomics and molecular biology will be helpful in improving economic traits and productivity through optimizing the microflora structure. China is recognized as a major shrimp production and consumption country in the world, but there are many problems in China’s shrimp industry, such as frequent disease outbreaks, low feed utilization, and water environmental pollution. Intestinal microflora as a symbiotic partner of shrimp has become the focus of research on healthy shrimp farming. In the process of shrimp culture, it is necessary to rationally mix the nutritional components of the diet at different stages of development to fully utilize the beneficial functions of intestinal flora, thereby promoting intestinal health. Therefore, it is necessary to build a shrimp specific intestinal bacterial strain bank and develop shrimp specific probiotic preparations. In general, the beneficial function of intestinal microflora has been widely recognized, but precise microflora regulation technology is still in the initial stage. An indepth understanding of the functional characteristics of intestinal flora can lay an important theoretical foundation for the healthy culture of shrimp and improve the production capacity and development and utilization of probiotics. This paper briefly describes the relationship between intestinal flora and growth and development, and disease occurrence. And the effects of feed nutrition and environmental stress on the intestinal flora of shrimp are further reviewed. Finally, this paper looks forward to the research and application trend of shrimp intestinal flora. The paper provides scientific basis for exploring the function of intestinal microbiota, improving shrimp intestinal nutritional health and developing new functional intestinal probiotics. Keywords: shrimp; intestinal flora; phenotypic traits; environmental stress Related Articles | Metrics