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Response of caspase genes to Streptococcus agalactiae in cells of spleen of golden pompano (Trachinotus ovatus)
GAO Jie, GUO Huayang, LIU Mingjian, LIU Baosuo, ZHU Kecheng, ZHANG Nan, GUO Liang, ZHANG Dianchang
 doi: 10.12131/20220099
[Abstract](172) [FullText HTML](48) [PDF 1104KB](13)
In order to explore the response of apoptosis related genes in the spleen of Trachinotus ovatus infected by Streptococcus agalactiae, we infected the spleen tissues of T. ovatus by S. agalactiae for a pathological observation. The blood routine indexes of the fish before and after infection, as well as different times (0 h, 6 h,12 h, 24 h, 48 h, 72 h, 96 h, 120 h) after infection, the serum lactate dehydrogenase (LDH), spleen alkaline phosphatase (ALP), and acid phosphatase (ACP) and quantitative analysis of Caspase-3, Caspase-8, and Caspase-9 genes. The results reveal that after artificial infection with S. agalactiae, the body of T. ovatus showed obvious pathological changes, mainly manifested as protruding eyes, turbidity and bleeding. Histopathological observation shows that the spleen tissue had inflammatory lesions. Compared with the control group, the number of red blood cells (RBC), hemoglobin concentration (Hgb) and hematocrit (HCT) in the infected group decreased significantly, while the number of white blood cells (WBC), neutrophils (NE) and lymphocytes (LYM) increased, and the mean red blood cell volume (MCV) increased. The activities of serum LDH, spleen ALP and ACP were up-regulated with time. The expressions of Caspase-3, Caspase-8 and Caspase-9 were significantly up-regulated in spleen. The results show that the body of T. ovatus infected by S. agalactiae had an obvious immune response.
Characteristics of feeding acoustic signals of Litopenaeus vannamei fed with pellets of different sizes
CAO Zhengliang, SHEN Mengting, LI Zhaocheng, WANG Zihao, WANG Xiuxiu
 doi: 10.12131/20220080
[Abstract](298) [FullText HTML](105) [PDF 2626KB](30)
Prawns will make noises passively when they eat. Investigating the effects of different particle sizes of pellet feed on the characteristics of feeding sound signals of L. vannamei can provide a theoretical basis for the application of automatic feeding based on feeding sound signals. With passive acoustic method, we recorded the acoustic signals of L. vannamei (Body length of 9−10 cm) feeding pellets of different sizes (0.4, 0.8 and 1.2 mm) in the laboratory. The results of the waveform, spectrogram and spectrum map reveal that the characteristics of feeding acoustic signals by feeding pellets of different sizes were similar, and the frequencies were 5−45 kHz. The spectral frequency peak of acoustic signals of the shrimps fed with pellets of 0.4 and 0.8 mm was about 17 kHz, and that of shrimps fed with pellets of 1.2 mm was about 10 kHz. In addition, there were obvious differences in the acoustic signals between feeding Nereis succinea and pellets. The frequency range of acoustic signals of feeding N. succinea was 5−45 kHz, and the spectral frequency peak was about 7 kHz. Finally, compared with the feeding acoustic signals of L. vannamei in farming pond, it is found that the signal characteristics collected in the pond were similar with those in the laboratory, and the only difference is that there was no secondary peak in the high frequency region of signals in the pond-cultured shrimp.
Research advances on processing and quality safety control technology of aquatic pre-made products
HUANG Hui, CHEN Shengjun, ZHAO Yongqiang, CEN Jianwei, YANG Shaoling, WANG Yueqi, XIANG Huan, LI Laihao, YANG Xianqing, WU Yanyan
 doi: 10.12131/20220190
[Abstract](373) [FullText HTML](59) [PDF 796KB](33)
Due to the growing demand for instant food and lifestyle change after the COVID-19, aquatic pre-made products become popular. The unique nutritional and functional characteristics and processing suitability of aquatic products make them suitable for the development of ready-to-eat, instant heat, instant cooked and ready-to-use pre-made products. However, due to their unique fishy taste, texture and perishable characteristics, appropriate pretreatment technology, flavor and quality improvement and maintenance technology as well as storage technology in the processing and storage process need to be adopted so as to improve the quality of pre-made products. The main factors affecting the quality and safety of aquatic product pre-made products include biological hazards, chemical hazards and physical hazards. Therefore, quality control technologies of aquatic pre-made products including the raw material collection, processing process and the cold chain transportation process are necessary. In the future, aquatic pre-made products should be more nutritious, high-quality and diversified because of the improvement of nutrition and quality control technology.
Mathematical analysis of morphometric attributes effects on body mass for four-month-old Plectropomus leopardus
YU Wei, LIN Heizhao, MA Zhenhua, WU Qia'er, CHEN Xueqing, YANG Yukai, HUANG Xiaolin, HUANG Zhong, ZHAO Wang, LI Tao, ZHOU Chuanpeng
 doi: 10.12131/20210253
[Abstract](358) [FullText HTML](91) [PDF 604KB](41)
To understand the relationship between the morphological traits and the body mass of coral trout (Plectropomus leopardus) is important for its breeding. In this study, we selected 159 individuals of the same batch of 4-month-old P. leopardus juveniles as the experimental objects to explore the correlation between the eleven morphological traits and body mass. The results show that there were significnat correlation between snout length (x9) and body mass (P<0.05), and extremely significant correlation between the other ten morphological traits and body mass. The results of path analysis reveals that the standard length (x2), body depth (x4), body width (x5), head height (x7), snout length (x9) were the main decisive morphological traits on body mass. The direct effect coefficient of body depth on body mass was 0.444, indicating that body depth mainly affected body mass through direct action. However, the other morphological traits mainly affected body mass indirectly via body depth. The total decision coefficient of five morphological traits on body mass was 0.853, indicating that these morphological traits were the main factors affecting body mass. After eliminating the morphological traits with insignificant coefficient to body mass, we established the multiple regression equation by multiple regression analysis. The morphological traits retained by the multiple regression analysis were consistent with that by path analysis.
Preparation and properties of collagen ACE inhibitory peptides from bone of eel (Anguilla japonica)
SHAO Yanqiu, HUANG Hui, LI Laihao, YANG Xianqing, CHEN Shengjun, HAO Shuxian, WU Yanyan, CEN Jianwei, DENG Shanggui
 doi: 10.12131/20210358
[Abstract](22) [FullText HTML](5) [PDF 3103KB](4)
To study the comprehensive utilization of by-products from eel processing, the angiotensin-converting enzyme inhibitory peptide was prepared from eel (Anguilla japonica) bone collagen by enzymatic hydrolysis. The ACE inhibitory activity and degree of hydrolysis were used as evaluation indexes, we determined the optimal hydrolysis conditions by single factor and response surface experiments. Furthermore, the amino acid composition and molecular mass distribution of the hydrolysate prepared under the optimized conditions were determined. The results show that alkaline protease was the optimal enzyme, and the optimal hydrolysis conditions were as follows: temperature of 50 ℃, mass concentration of 15 g·L−1, hydrolysis time of 5.25 h, enzyme dosage of 3.1% (Mass fraction) and pH of 9.2. Under these conditions, the ACE inhibitory activity was 70.33%, which was close to the predicted value. The molecular weight of peptides below 1 000 D and 1 000–3 000 D in enzymatic hydrolysate accounted for 57.02% and 36.55%, respectively. Amino acid composition analysis shows that the content of hydrophobic amino acids related to ACE inhibition activities (Such as Pro、Val、Ile、Leu、Phe) increased.
Optimization of thermal sterilization process for low-acid and acidified instant laver
GE Mengmeng, SHEN Jiandong, TANG Xiaohang, XIA Wenshui, XU Yanshun
 doi: 10.12131/20220003
[Abstract](279) [FullText HTML](93) [PDF 1039KB](34)
In order to optimize the sterilization process of laver (Porphyra spp.) and develop high-quality instant wet laver products, we measured the heat penetration curves during high-pressure heat treatment (110, 115, 121 ℃) and normal pressure heat treatment (85, 90, 95 ℃) for low-acid and acidified lavers (pH≤4.6). Combined with preservation experiment and microbial analysis, we determined the F-value (Safe sterilization heating time) corresponding to the two sterilization methods, and explored the effects of different temperature-time combinations on the sensory and nutritional quality of laver with the same F-value. Results show that low-acid laver could reach commercial sterility when F0 was 3 min under high-pressure heat sterilization, and acidified laver could also reach the preservation requirements when \begin{document}${F\,}_{93.3}^{8.89}$\end{document} was 5 min under normal pressure heat sterilization. Compared with high-pressure heat sterilization, acidification combined with normal pressure sterilization could obtain better texture and color. The toughness, hardness and sensory score of laver increased with the increase of sterilization temperature with the same F-value. In terms of nutrients, the total soluble sugar and free amino acids decreased with the increase of temperature in the high-pressure group. The highest free amino acids content was obtained at 90 °C in the normal-pressure group. In general, the texture, sensory and nutritional quality were better when the sterilization parameters were 90 °C, 11.5 min (Acidified group) and 115 °C, 8 min (Low-acid group).
Effect of low-temperature acclimation on survival, non-specific immune and antioxidant indexes of Epinephelus fuscoguttatus ♀×E. lanceolatus
YUAN Zhongjin, CEN Jianwei, LI Laihao, YANG Xianqing, HUANG Hui, WEI Ya, HAO Shuxian, ZHAO Yongqiang, WANG Yueqi, LIN Zhi
 doi: 10.12131/20220042
[Abstract](263) [FullText HTML](55) [PDF 966KB](2)
Investigating the best acclimation temperature conditions for Epinephelus fuscoguttatus ♀×E. lanceolatus ♂ can provide a theoretical basis for its survival and circulation. We decreased the water temperature to 24, 20, 18 and 16 ℃ at the rate of 0.5−1.0 ℃·h−1, then recorded the physiological responses and survival time, as well as the changes of water quality, non-specific immune index and antioxidant indicator. The results show that the survival time of the grouper increased with the decrease of temperature within the range of 24−16 ℃. When the water temperature was maintained at 16 ℃, the concentration of total ammonia nitrogen (TAN) increased slowly, and the survival time was the longest, up to 109 h. The non-specific immune and antioxidant parameters changed after the grouper being cultured at different temperatures for 48 h. Compared with the control group, the contents of complement protein 3 (C3), globulin (GLB) and total protein (TP) increased in 16 ℃ group significantly, while the other indexes had no significant changes. The activities of superoxide dismutase (SOD) and catalase (CAT) in the liver tissue in 16 ℃ group increased significantly. However, the activity of glutathione peroxidase (GPx) decreased significantly, but higher than those of the other temperature groups. Compared with the other temperature treated groups, the content of malondialdehyde (MDA) decreased significantly. Thus, 16 ℃ temporary culture can not only maintain good water quality, but also reduce the metabolic level of fish and maintain the homeostasis of internal environment, so as to reduce the damage caused by oxidative stress reaction. It is suitable for temporary culture and transportation of Epinephelus fuscoguttatus ♀×E. lanceolatus ♂.
Study on adsorption performance of zinc-based metal-organic framework for trimethylamine
LYU Daofei, LIN Jieling, XU Feng, YUAN Wenbing, ZHANG Yan, CHEN Xin
 doi: 10.12131/20220160
[Abstract](140) [FullText HTML](37) [PDF 1444KB](6)
Rich in proteins and other active substances, seafoods have been widely used in the food and cosmetic industries. How to remove fishy substances such as trimethylamine from seafoods with high selectivity is a challenge for the current seafood processing. In this paper, zeolite imidazole framework-8 (ZIF-8), zeolites socony mobil-5 (ZSM-5) and activated alumina were characterized by powder X-ray diffraction and scanning electron microscopy, and their adsorption performance for the typical fishy substance (Trimethylamine) was also investigated. Adsorption kinetics tests show that the adsorption saturation of the three adsorbents reached at about 600 min in a 200 mg·L−1 trimethylamine solution. The adsorption isotherms of the three adsorbents at 25 ℃ were tested and their adsorption capacities for trimethylamine followed a descending order of ZIF-8 (517.1 mg·g−1) > activated alumina (401.8 mg·g−1) > ZSM-5 (390.3 mg·g−1). Under the same conditions, the adsorption uptake of trimethylamine on ZIF-8 was 3.2 times higher than that on activated carbon, exceeding those of most materials in the same period. Fourier transform infrared spectroscopy tests and Zeta potential tests show that the adsorption interactions between ZIF-8 and trimethylamine were dominated by C-H···π interaction, C-H···N interaction and electrostati force.
Effects of nanometer selenium on immune protection and antioxidant ability of Eriocheir sinensis under hypoxia stress
JIA Huining, SHI Miaomiao, BIAN Yongle, SHI Chongjing, LIU Hengwei, SONG Xuehong, QIN Fenju
 doi: 10.12131/20220106
[Abstract](115) [FullText HTML](37) [PDF 1225KB](8)
Hypoxia stress will weaken the immune function and antioxidant capacity of Eriocheir sinensis. In order to reveal the immune protection and anti-oxidation regulation mechanism of nanometer selenium (nano-Se) on E. sinensis under hypoxia stress, we had fed E. sinensis with different doses of nano-Se (0, 0.1, 0.2, 0.4, 0.8 and 1.6 mg·kg−1) in basic diets for 90 d. After the feeding, we conducted a hypoxia stress test and injected Aeromonas hydrophila under hypoxia stress. The results show that: 1) The mortality of E. sinensis under hypoxia stress for 24 h and that infected with A. hydrophila under hypoxia stress reached 62.45% and 100%, respectively. The levels of hemocyanin and the hemocyte count in crab hemolymph, and the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in crab tissues increased significantly under hypoxia stress for 12 h (P<0.05), as well as there was a decreasing trend under stress to 24 h. The contents of lactic acid (LD) and malondialdehyde (MDA) continued to rise from 12 to 24 h under hypoxia stress. 2) Appropriate addition amount (0.1−0.4 mg·kg−1) of nano-Se reduced the mortality of E. sinensis significantly and the lethality of A. hydrophila under hypoxia stress (P<0.05), increasing the levels of hemocyanin, the hemocyte count and the activities of antioxidant enzymes (SOD, CAT, GSH-Px) under hypoxia stress significantly, but decreasing the contents of LD and MDA (P<0.05). The addition of 0.8−1.6 mg·kg−1 nano-Se had aggravated hypoxia stress injury. These results indicate that appropriate addition of nano-Se to the diets can improve the decrease of immune response and antioxidant ability of E. sinensis under hypoxia stress, and the optimal dose of nano-Se in basal diets is 0.2 mg·kg−1.
Development of vertebral column and appendicular skeleton in larvae and juveniles of Platax teira
GUO Huayang, LIU Mingjian, GAO Jie, ZHU Kecheng, LIU Baosuo, GUO Liang, ZHANG Nan, SUN Jinhui, ZENG Chen, YANG Jingwen, LIU Bo, ZHANG Dianchang
 doi: 10.12131/20220058
[Abstract](264) [FullText HTML](97) [PDF 3140KB](16)
Understanding the developmental time sequence characteristics of the spine and appendage skeletal system of Platax teira can provide a theoretical basis for its seedling breeding, environmental adaptation and classification. We stained and analyzed the spine, pectoral fin, pelvic fin, anal fin and caudal fin of P. teira larvae (0–30 dah) by the method of cartilaginous and bony staining. The results show that there were 24 vertebrae, and the tail bone was composed of five subcaudal bones and two upper caudal bones. The development sequence of appendage branch fin bones was pectoral fin, abdominal fin, caudal fin, anal fin and dorsal fin. The first hatched fish already had pectoral branch fin bone primordium and notochord. At 4 dah, the pectoral fin and pelvic fin developed first; at 7 dah, medullary arch and vein arch appeared; at 13 dah, the morphology and number of larval bones were basically stable; at about 26 dah, ossification began in juvenile fish, and the spine and spine were the first to complete ossification; at 30 dah, the larvae entered the juvenile stage, and their appearance has been fixed. The typical characteristics were three black bands on the head, trunk and tail, and the body was white silver. When being stimulated or stressed by external stimulation, the body color changed to black instantly, and the shape had no difference from that of the juvenile. The developmental sequence of the spine and appendage bones was basically the same with that of other sea fish, but the time nodes and number of the development of bone were different.
A preliminary study on reproduction and feeding habits of Lutjanus gibbus from Meiji Reef of Nansha
WANG Teng, LIU Yong, LI Chunran, LI Chunhou, TANG Guanglong, XIAO Yayuan, LIN Lin, WU Peng
 doi: 10.12131/20210379
[Abstract](234) [FullText HTML](58) [PDF 942KB](38)
Lutjanus gibbus, a kind of coral reef fish with delicious meat and high economic value, whose spawning aggregation can easily lead to overfishing. Based on 67 individuals of L. gibbus collected by diving fishing in the waters of Meiji Reef in July 2020, we investigated its basic biological characteristics, including sex ratio, sexual maturity body length, egg diameter characteristics, fecundity and feeding habits, in order to provide basic biological data for the protection and management of L. gibbus. The results show that the ratio of female to male of L. gibbus was 2:1; the 50% sexually mature body lengths of males and females were 204.757 and 201.623 mm, respectively; the egg diameter of Stage IV gonadal was 0.176–0.419 mm with an average of 0.296 mm; the frequency distribution of egg diameter was unimodal. The fecundity of L. gibbus was 51 858–276 205 eggs with an average of 139 145 eggs. Its fecundity had a significant power function relationship with body length and body mass. The preys of L. gibbus from Meiji Reef were crabs, fish, snails, shellfish and shrimps. The stable isotope study shows that the average trophic level of L. gibbus was 3.33, and its feeding habits changed significantly with individual development (The niche width was narrower and the trophic level was higher).
Effect of trichloroisocyanouracic acid on antibiotic resistance genes in aquaculture water of shrimp
XIA Taotao, SU Haochang, HU Xiaojuan, XU Yu, WEN Guoliang, CAO Yucheng, YU Zhaolong
 doi: 10.12131/20210361
[Abstract](219) [FullText HTML](38) [PDF 784KB](3)
In order to explore the feasibility of removing and controlling the spread of antibiotic resistant genes (ARGs) by the fishing oxidant trichloroisocyanuric acid (C3Cl3N3O3) in the aquaculture water environment, we applied the real-time quantitative PCR to monitor and determine the ARGs concentrations in the offshore source water, storage water of sedimentation tank and reserved water after oxidation and disinfection for 29 d. The final concentration of trichloroisocyanuric acid used for oxidation and disinfection was 40 mg·L−1. The target ARGs were commonly found in the aquaculture environments, including sul1, sul2, tetX, tetM, floR, cmlA and qnrA. The results show that sul1, sul2, floR and tetX were the dominant ARGs among the above mentioned water samples. The number of types and total concentration of ARGs were the highest in offshore source water. The total concentrations of ARGs in the storage water of sedimentation tank were lower than those in the offshore source water, especially that the concentrations of sul2 and floR were 0.86 and 0.34 lg lower than those in the offshore source water, respectively. After the oxidation and disinfection by trichloroisocyanuric acid, the total concentrations of ARGs in the reserved water decreased, and compared with the offshore source water, the concentrations of sul2 and floR decreased by 1.58 and 1.30 lg, respectively. The results indicate that offshore source water is the main source of ARGs in the aquaculture environment. Oxidation and disinfection treatment on offshore source water with trichloroisocyanuric acid can reduce the concentrations of common ARGs in the aquaculture water significantly, which is helpful to prevent and control the spread of ARGs in aquaculture environments.
Estimation of genetic parameters and its breeding progress for body mass and body length of Cyprinus carpio var. Quanzhounensis
DU Xuesong, CHEN Zhong, WEN Luting, PAN Xianhui, HUANG Yin, ZHOU Kangqi, LIN Yong, LI Zhe, LUO Hui, QIN Junqi
 doi: 10.12131/20210353
[Abstract](234) [FullText HTML](52) [PDF 858KB](28)
In order to improve the growth rate of the cultured population of Cyprinus carpio var. Quanzhounensis in Quanzhou, two generations of breeding were carried out by family breeding method. The body mass and body length indexes of 3 699 individuals in 121 families of G0, G1 and G2 generations of C. carpio were measured. The heritability, phenotypic correlation and genetic correlation of body mass and body length traits were estimated by mixed linear model. The selection progress of G0−G2 generations was evaluated by the method of breeding value and least square value estimation based on target traits. The results show that the coefficient of variation of body mass and body length was 0.50−0.72 and 0.18−0.22 respectively. The heritability estimates were 0.132 (P<0.01) and 0.122, respectively (P<0.01). The genetic correlation and phenotypic correlation were 0.921 (P<0.01) and 0.995 (P<0.01), respectively. The value of selective reaction in body mass estimated by breeding value based on target traits and least square estimation was 12.82% and 15.45%, respectively, while 2.76% and 6.60% in body length, respectively, which indicates that the evenness of body mass was low, not conductive to breeding production, but had high breeding and improvement potential. In general, this population of C. carpio var. Quanzhounensis obtained effective genetic progress after two successive generations by the family breeding, but with a modest progress. In is suggested that molecular-assisted selection (MAS) and marker-assisted large-scale mixed families' selection should be adopted in the future breeding so as to improve the breeding efficiency.
Molecular cloning, expression profile and subcellular localization of nanos1 gene from Macrobrachium rosenbergii
ZHOU Nan, WANG Yakun, HONG Kunhao, WEI Jie, YU Lingyun, ZHU Xinping
 doi: 10.12131/20220067
[Abstract](146) [FullText HTML](42) [PDF 4100KB](1)
To investigate the function of the nanos1 gene in the reproductive development of Macrobrachium rosenbergii, we cloned its nanos1 gene. The cDNA sequence was 2 811 bp, encoding 243 amino acids. Phylogenetic analysis shows that it had the highest homology with Eriocheir sinensis, higher homology with nanos1 in fish but lower homology with mammals. We detected the expression level of the gene at different embryonic developmental stages and in larvae by real-time fluorescence quantitative PCR. The results show that the expression level of nanso1 mRNA was the highest at unfertilized stage, significantly higher than that at fertilized stage and the other embryonic developmental stages (P<0.05). During the embryonic development, the expression was the highest at fertilization stage, significantly higher than that at cleavage stage and very significantly higher than that at late embryonic development (P<0.01). The expression level of this gene at cleavage stage was significantly higher than that from blastocyst stage to larval stage. The expression level from blastocyst stage to larval stage was low and there was no difference. In situ hybridization shows that nanos1 mRNA was expressed in the cytoplasm of oocytes and primary oocytes (Oc1, Oc2, Oc3 and Oc4). The results show that nanos1 is closely related to the development of female germ cells of M. rosenbergii.
Research on effect of hypoxia stress on liver tissue of zebrafish (Danio rerio) based on transcriptomics technology
SONG Ruhao, HU Ruiqin, LI Genfang, ZHANG Zhicong, XU Qianghua
 doi: 10.12131/20220038
[Abstract](137) [FullText HTML](49) [PDF 1168KB](32)
To explore the regulatory mechanism of fish response to hypoxia stress, we stressed 1-month-old wild zebrafish (Danio rerio) by hypoxia to 1.5 mg·L−1 for 2 months, and then investigated the liver tissues by transcriptome sequencing and comparative analysis. According to the KEGG analysis performed on 3 270 differential genes in normoxia and hypoxia groups, the genes mainly enriched in pathways such as cell proliferation, lipid metabolism, carbohydrate metabolism and amino acid metabolism. Among them, the up-regulated 1 864 genes were mainly related to cell proliferation, while the down-regulated 1 406 genes were mainly involved in lipid metabolism. We performed a GO enrichment analysis on the differential genes, and found that the function of iron ion banding was significantly different. Based on the analysis of expression of iron metabolism-related genes, the iron ion storage related genes fthl28 and fthl31 changed significantly, which suggests that the iron ion content in zebrafish liver (ZFL) tissue changes significantly under hypoxic stress. Moreover, we conducted the in vitro validation experiments by using ZFL cells which were subjected to 0.1% (Volume fraction) O2 hypoxia stress. The results show that with the prolongation of hypoxia stress time, the survival rate of ZFL cells decreased, and the expression of iron metabolism-related genes and ferritin in the cells decreased significantly. In conclusion, iron metabolism regulation is an important response process under hypoxia stress. Hypoxia may lead to disturbance of intracellular iron metabolism, and prolonging hypoxia time will form a new iron homeostasis. The study provides a theoretical basis and references for exploring the hypoxia adaptation mechanism of fish.
Molecular cloning and characterization in immune response of two C-type lectin genes (SaCD302 and SaMBL) from Symphysodon aequifasciatus
MA Tengfei, WEN Bin, LIU Xin, MIAO Lin, GAO Jianzhong, CHEN Zaizhong
 doi: 10.12131/20220018
[Abstract](212) [FullText HTML](69) [PDF 959KB](16)
Symphysodon aequifasciatus has a unique parental rearing behavior. In the previous study, two C-type lectins (CTLs) were found to be highly expressed in the skin of parent fish, but with different expression patterns. In order to investigate the difference in the potential immune functions of the specific CTLs, we cloned two CTL genes (SaCD302 and SaMBL), then simulated and analyzed their immune esponse patterns under pathological infection. The results show that the ORF region of SaCD302 and SaMBL were 741 and 795 bp in length, encoding 246 and 264 amino acids (aa), respectively. The SaCD302 sequence contained a signal peptide (aa 1–29), a C-type lectin-like domain (CTLD) (aa 32–169) and a transmembrane domain (aa 184–206). Two low complexity regions (aa 32–92 and aa 104–121) and a CTLD (aa 137–263) were expressed in SaMBL sequence. Moreover, SaCD302 and SaMBL shared the highest similarity with that of Archocentrus centrarchus. SaCD302 was highly expressed in the head kidney, followed by the liver and gill. Compared with the intestine, liver, spleen and gonads, the skin had the higher expression of SaMBL. After Aeromonas hydrophila infection, SaCD302 expression was significantly upregulated in the spleen, head kidney, intestine and skin, while SaMBL was only upregulated in the head kidney, intestine and skin, and these two genes were expressed in different temporal manners, indicating that they might play different roles in the immune defense of S. aequifasciatus.
Species identification and morphology of fish eggs from Jiangmen coastal waters in spring using DNA barcoding
CHEN Jing, HUANG Delian, WANG Xuehui, XU Lei, ZHANG Jian, LI Yafang, NING Jiajia, WANG Lianggen, LIU Shuangshuang, LIN Zhaojin, DU Feiyan
 doi: 10.12131/20220028
[Abstract](325) [FullText HTML](80) [PDF 1405KB](29)
Jiangmen is located in the southwest of the Pearl River Estuary. It is the spawning ground and nursery ground for various small fish. We identified the species of fish eggs from Jiangmen coastal waters of the Pearl River Estuary in sping based on DNA barcoding analysis, then described and preliminarily classified the morphological characteristics of fish eggs. We acquired a total of 13 taxa, which belonged to three orders and ten families. Four and eight taxa were identified to species and genus levels, respectively (Ambassis gymnocephalus, Gerres limbatus, Sillago sihama, Cynoglossus puncticeps, Sardinella sp., Stolephorus sp., Acanthopagrus sp., Alepes sp., Johnius sp., Sillago sp. and Cynoglossus sp.). One taxon was identified in family (Leiognathidae sp.). The results demonstrate that most fish eggs collected in the survey area can be classified by morphological characteristics such as shape, fish eggs size, perivitelline space, number and pigment distribution of oil globules. In addition, the colour, amount and distribution of pigments of the embryo are also important in species identification when the embryo is well developed. However, it is difficult to distinguish the closely related species only by the morphological characteristics of a single developmental stage. Further morphological studies should be conducted in the future.
Genetic structure analysis of Ochetobius elongatus between Yangtze River and Pearl River using multiple loci
CHEN Weitao, DUAN Xinbin, GAO Lei, LI Xinhui, YANG Jiping, WANG Dengqiang
 doi: 10.12131/20220007
[Abstract](248) [FullText HTML](53) [PDF 1013KB](2)
To protect the genetic diversity of a critically endangered species Ochetobius elongatus, taking seven individuals of O. elongatus collected from the field investigation in the Yangtze River as samples, we sequenced two mitochondrial genes (Cytb and ND2) and two nuclear genes (mhy6 and RAG2) for the seven samples by Sanger sequencing technique. Combining with the published four gene sequences of 52 O. elongatus samples in the Pearl River, we explored the genetic structure of O. elongatus between the Pearl River and the Yangtze River, so as to provide scientific support for its conservation. We applied phylogenetic analyses, haplotype networks and divergence time estimation. Phylogenetic analyses and haplotype networks reveal that O. elongatus populations in the two rivers generated two deep and independent lineages, and formed private alleles at the nuclear gene level. The results suggest that O. elongatus populations in the two rivers evolved independently without agene flow. The rapid lifting of the Qinghai-Xizang Plateau during the middle Pleistocene might be an important factor that triggered the split of O. elongatus populations in the two rivers 0.38~0.76 million years ago (Ma). In view of the strictly geographical division of O. elongatus populations between the two rivers at both mitochondrial and nuclear gene levels, we suggest that these two populations should be regarded as two evolutionary significant units, and targeted strategies should be urgently put forward to manage and protect its resources.
An investigation of large-size light falling-net fishing vessels operating in South China Sea based on Beidou VMS data
QIAN Jing, LI Jiajun, CHEN Zuozhi, MA Shengwei, ZHANG Peng, QIU Yongsong, CAI Yancong
 doi: 10.12131/20220001
[Abstract](297) [FullText HTML](78) [PDF 2764KB](17)
Beidou vessel monitoring system (VMS), which monitors fishing operations of vessels by vessel position characteristics, can provide scientific references for the development and management of fishery. We explored the large-size light falling-net fishery in the South China Sea based on VMS data in 2018. Beidou VMS obtained a total of 8 821 681 records of 121 vessels from Guangdong, Guangxi and Hainan Provinces, with an average of 406 records per vessel per day. There is a difference in the frequency of Beidou VMS transmission among the vessels from different provinces, and VMS signals were more frequently transmitted when a vessel was operating in the open South China Sea than when it was fishing along the coast. The vessels mainly operated fishing in the Nansha Islands in spring, off the Pearl River Estuary in summer, and in the Beibu Gulf and Zhongsha and Xisha Islands waters in autumn and winter. In 2018, the vessels operated 19 986 fishing days in the South China Sea, decreasing from 7 768 d (38.87%) in spring, 4 738 d (23.71%) in autumn, 4 406 d (22.05%) in winter to 3 074 d (15.38%) in summer. Moreover, we discussed the advantages and disadvantages of Beidou VMS in monitoring the large-size light falling-net vessels. It is showed that using Beidou VMS to study the large-scale light falling-net vessel in the South China Sea can monitor their spatial distribution and dynamic changes quickly and comprehensively.
Effects of temperature on survival and growth of Paphia textile juveniles
WU Jiaying, DAI Mingshu, LIU Zhigang, LIU Xiaokun
 doi: 10.12131/20220155
[Abstract](84) [FullText HTML](19) [PDF 879KB](7)
In this study, we observed the effects of temperature on the survival and growth of Paphia textile juveniles by using experimental ecological methods, so as to provide references for the selection of the intermediate breeding site of the juveniles. The results show that: 1) The 48 h semi-lethal low and high temperatures were 4.95 and 33.39 ℃, respectively; the semi-lethal low and high temperatures at 96 h were 8.68 and 32.49 ℃, respectively; the 15 d semi-lethal low and high temperatures were 12.09 and 31.02 ℃, respectively. 2) At 10 ℃, the juveniles all died on the 10th day, and at 32 ℃, the survival rate of the juveniles on the 15th day was only 16.67%. 3) Taking the high and low temperatures of 50% of individuals which survived stably within 15 d as the critical temperature for survival, we found that the suitable survival temperature range of the juveniles was 12.09–31.02 ℃. Based on the group or groups with the highest survival rate (No significant difference between groups), the most suitable survival temperature range of juveniles was 14–28 ℃. 4) Based on the high and low temperatures corresponding to the average daily growth of 30% of the optimal group, the suitable growth temperature range of juveniles was 16.62–31.14 ℃. Based on the group or groups with the highest average daily growth (No significant difference between groups), the most suitable growth temperature range of juveniles was 24–28 ℃, and the optimal growth temperature was obviously biased towards the high temperature side within the suitable survival temperature range. In conclusion, it is inferred that P. textile juvenile is suitable for underwater bottom sowing in the southern sea area with a subtidal water temperature below 31 ℃.
Effect of five factors on removing ammonia nitrogen and nitrite by Rhodococcus ruber HDRR2Y fermentation
XU Yu, HU Xiaojuan, ZHANG Song, XU Wujie, SU Haochang, WEN Guoliang, CAO Yucheng
 doi: 10.12131/20220044
[Abstract](133) [FullText HTML](24) [PDF 760KB](4)
The bacteria Rhodococcus ruber is usually used in waste water and sewage treatment. In order to discuss the effect of environmental factors on R. ruber HDRR2Y's removing ammonia nitrogen and nitrite, we added the culture medium of R. ruber strain HDRR2Y to the aquaculture water containing high concentration of ammonia nitrogen (\begin{document}${\rm{NH}}_4^+ $\end{document}-N) and nitrite (\begin{document}${\rm{NO}}_2^- $\end{document}-N), and observed the changes of ammonia nitrogen and nitrite concentrations by the national standard method, so as to investigate the effect of the culture medium on the removal of ammonia nitrogen and nitrite. In addition, we carried out the Plackett-Burman experimental design according to five factors: temperature, rotating speed, salinity, inoculum amount, substrate (Ammonia nitrogen and nitrite) concentration, to explore the effect of these factors on the removal of ammonia nitrogen and nitrite by R. ruber. The results show that during the fermentation process, the mass concentration of strain HDRR2Y increased from 5×104 CFU·mL−1 to 4.08×109 CFU·mL−1 in the initial 36 h. After adding the culture medium, the mass concentration of ammonia nitrogen decreased from 15 mg·L−1 to 5.56 mg·L−1, with a removal rate of 62.96%, and that of nitrite decreased from 15 mg·L−1 to 6.95 mg·L−1, with a removal rate of 59.37%. Among the five factors, temperature and ammonia nitrogen concentration had the most significant effects on the removal of ammonia nitrogen by strain HDRR2Y (P<0.05) (Temperature>ammonia nitrogen concentration>rotation speed>biomass>salinity). Temperature and rotating speed were the two most significant factors affecting the removal of nitrite (P<0.05) (Temperature>rotating speed>salinity>nitrite concentration>bacterial count). It is showed that the culture medium of strain HDRR2Y is good for removing ammonia nitrogen and nitrite, and temperature is the most significant factor affecting the efficiency of HDRR2Y in removing ammonia nitrogen and nitrite.
Influence of statistical deviation of historical catch on stock assessment: a case study of western Atlantic Thunnus thynnus
FENG Ji, ZHU Jiangfeng, ZHANG Fan, LI Yanan, GENG Zhe
 doi: 10.12131/20220037
[Abstract](41) [FullText HTML](11) [PDF 1134KB](10)
Catch data, which is the most basic data required for stock assessment, is also most likely to cause reporting and statistical errors. Misreporting is one of the causes for statistical deviation of historical catch, which is currently prevalent in all types of fisheries worldwide. Analyzing the influence of statistical deviation of historical catch on stock assessment based on historical data helps to establish reasonable management objectives, and promote sustainable utilization of fishery resources. In this study, we selected western Atlantic bluefin tuna (Thunnus thynnus) as an example to evaluate the influence of statistical deviation of historical catch on its stock assessment. We carried out a stock assessment by using Age-Structured Assessment Program (ASAP), and investigated the effects of catch information inaccuracy on the assessment results by setting different levels of statistical deviation of historical catch. The results indicate that the estimated values of fishing mortality (F) and spawning stock biomass (SSB) changed in the same direction with the adjusted catch. With the increase of statistical deviation of catch, the relative difference of biological reference points also increased. The relative deviation rate of F-related biological reference points was less than 1% under all eight assumed statistical deviations of catch. When the statistical deviation of the historical catch was assumed as −20%, the maximum relative difference of SSB-related biological reference points was about 4%. The statistical deviation of catch had a more obvious impact on SSB-related biological reference points than F-related biological reference points. In conclusion, it is suggested to strengthen the source analysis of catch data quality issues, so that the scientific reconstruction of historical fishery data can be conducted to improve the accuracy and reliability of the stock assessment results.
Comparative analysis of nutritional composition of muscle from Siganus oramin living in different habitats
YANG Yukai, HUANG Xiaolin, SHU Hu, LIN Heizhao, WANG Lan, XUN Pengwei, YU Wei, HUANG Zhong, LI Tao
 doi: 10.12131/20210345
[Abstract](206) [FullText HTML](25) [PDF 803KB](11)
To provide basic data for the production of Siganus oramin formula feed, we measured the general nutritional composition, amino acids and fatty acids in the muscle of S. oramin from industrial farming, high pond farming and the wild by means of biochemical analysis, investigated the effects of habitat on muscle the nutrition and quality of S. oramin. The results show that compared with the wild fish, the contents of crude protein and crude lipid were higher but those of ash and moisture were lower in the muscle of the farmed fish, and the crude fat content in the industrial farmed fish was significantly higher than that of the other groups (P<0.05). Moreover, there were 17 common amino acids in the three kinds of fishes. Among them the glutamate content was the highest. Among the essential amino acids (EAA), lysine had the highest content. The essential amino acid index (EAAI) was highest in high-pond farmed fish but lowest in the wild fish. Furthermore, there were 26 species fatty acids in the two kinds of farmed fish but only 24 species were found in the wild fish. The contents of polyunsaturated fatty acids (PUFA), n-6 series C18:2n6c were highest in the two farmed fishes, while those of the C22:6n3 (DHA) and C20:5n3 (EPA) of n-3 series were significantly higher in the wild fish. The ratio of n-3/n-6 and the content of DHA+EPA in the wild fish were significantly different from the two farmed fishes (P<0.05). Thus, it is revealed that the farmed S. oramin's nutrition and flavor are better than the wild ones, but they lack n-3 PUFA such as DHA and EPA.
Display Method:
2022, 18(5).  
[Abstract](45) [PDF 760KB](18)
Research Paper
Evaluation of fisheries ecological environment in adjacent sea areas of Wanshan Archipelago in Pearl River Estuary in spring
WU Peng, LIU Yong, XIAO Yayuan, XIE Yufang, TANG Guanglong, LIN Lin, WANG Teng, LI Chunhou
2022, 18(5): 1-8.   doi: 10.12131/20210332
[Abstract](406) [FullText HTML](108) [PDF 1032KB](47)
Wanshan Archipelago plays an important role in the conservation of fishery resources in the Pearl River Estuary. However, there is still a lack of sufficient research on the fishery ecological status of the adjacent waters of islands and reefs in this region. Thus, we analyzed the characteristics of the seawater environment and zooplankton community in Wanshan Archipelago in April 2021. The results show that the seawater environment of Wanshan Archipelago was greatly influenced by fresh water input from the Pearl River coastal channels. Consequently, the concentration of dissolved inorganic nitrogen, nutrient quality index and eutrophication index were higher in the adjacent sea areas of Guishan Island and Dong'ao Island which are located in the northwestern Wanshan Archipelago. Eutrophication was observed in this area. Furthermore, the primary production in the seawater of these two islands was also higher, most with medium and low levels. The zooplankton communities of Wanshan Archipelago can be divided into three groups, and one of them affiliated to the adjacent sea areas of Guishan Island had a low Shannon-Wiener index value, indicating a potentially polluted seawater environment. However, high abundances of spawning and larval fish were observed at Guishan Island (133 egg·m−3 and 18 ind·m−3, respectively), suggesting that it is an important fish spawning area. The primary production and Pielou evenness index of zooplankton can reflect the correlation between water environment and zooplankton community in Wanshan Archipelago, and can indicate the state of water eutrophication.
A preliminary study on community structure of mesopelagic fish in cold seep of Xisha Islands
TIAN Han, JIANG Yan'e, ZHANG Jun, CHEN Zuozhi, XU Shannan, ZHU Jiangfeng, YU Wenming
2022, 18(5): 9-17.   doi: 10.12131/20210370
[Abstract](342) [FullText HTML](68) [PDF 880KB](25)
To recognize the fish composition of cold seep ecosystems, and provide a scientific basis for biodiversity conservation and monitoring in the relevant regions, we investigated the mesopelagic fish resources inside and outside the cold seep in the Xisha Islands by a mesopelagic trawler. A total of 106 species of mesopelagic fish had been identified which belong to 62 Genera, 31 Families and 12 Orders, with the dominant groups of Myctophiformes and Stomiiformes. Among them, 84 species of fish belonging to 54 Genera, 30 Families, 11 Orders were collected inside the cold seep; while 60 species of fish belonging to 32 Genera, 13 Families and 6 Orders were collected outside the cold seep. There were 38 shared species of mesopelagic fish belonging to 22 Genera, 9 Families, 5 Orders inside and outside the cold seep, and the main shared species were Chauliodus sloani, Ceratoscopelus warmingii and Diaphus garmani. The Jaccard species similarity index shows that the species similarity of mesopelagic fish was moderately different inside and outside the cold seep (I=35.8%). The average taxonomic distinctness (Δ+) of mesopelagic fish was significantly higher inside the cold seep than outside (P<0.01), but the variation in the taxonomic distinctness (Λ+) of mesopelagic fish community was inverse (P<0.01). From the perspective of pelagic distribution, there were significant differences in the species composition of the mesopelagic fish communities inside and outside the cold seep (P<0.01). In the surface waters, the mesopelagic fish diversity inside the cold seep was lower than outside, while it's inverse in the deeper water layers. There was a correlation between the fish communities at different stations inside and outside the cold seep in terms of water stratigraphy and timing, with higher similarity between the deeper layers inside the cold seep; and higher similarity between the nocturnal surface layers inside the cold seep area and the nocturnal surface layers outside the cold seep. The results show that there are differences in the mesopelagic fish communities inside and outside the cold seep, with more species of mesopelagic fish inside the cold seep and a higher diversity of species in the deeper water layers. Eight key species that distinguish the mesopelagic fish communities in the waters inside and outside the cold seep include Bolinichthys longipes and Vinciguerria nimbara, having a cumulative contribution of 56.06%.
Site selection of marine ranching in Wailingding Island sea area of Zhuhai
XIE Xiaoyan, CHEN Pimao, TONG Fei, YUAN Huarong, FENG Xue, YU Jing, YU Jie, SHU Liming
2022, 18(5): 18-29.   doi: 10.12131/20210241
[Abstract](402) [FullText HTML](135) [PDF 934KB](21)
Site selection of marine ranching plays a key role in marine ranching construction. Appropriate site is the precondition of a successful marine ranching construction. In this study, we selected 34 indicators as the factors for marine ranching suitability evaluation (Coastline stability, marine functional zoning, marine ecological red lines, aquaculture water tidal flat planning, marine engineering and facilities), and established an index system for marine ranching site selection. On this basis, according to the actual situation of Wailingding Island of Zhuhai, we selected eight indexes including length and area change intensity of island coastline, marine functional zoning, marine ecological red line, beach planning of aquaculture waters, ports, anchorages, navigable areas and submarine pipelines, to evaluate the suitability of marine ranching site selection in that sea area by using the spatial analysis method of GIS. The results show that there was no most suitable and more suitable area for marine ranching construction, and the areas of generally suitable and unsuitable areas for marine pasture construction were 33.09 and 45.59 km2, respectively. The suitable area for marine ranching construction was similar to the existing artificial reefs and planned marine ranching areas in Zhuhai.
Effects of elevated CO2 and photoperiod on growth and physiological performance of seedlings of Ulva prolifera
ZHOU Wei, WU Hui, HUANG Jingjing, ZHAO Xixing, WANG Jingwen, WANG Jinguo
2022, 18(5): 30-38.   doi: 10.12131/20210278
[Abstract](282) [FullText HTML](71) [PDF 1098KB](17)
Ulva prolifera seedlings, which are the main component of the natural "seed bank" of green tide algae, play an important role in the occurrence and development of green tide. In order to understand the causes of the early outbreak of the green tide of U. prolifera and provide basic data for its early warning and prevention, we studied the growth and physiological responses of seedlings after the seedlings being cultured at two different CO2 levels (LC: 400 μatm; HC: 1 000 μatm) in combination with three different photoperiods (LL: 10 L∶14 D; ML: 12 L∶12 D; HL: 14 L∶10 D). The relative growth rate of seedlings were significantly enhanced by elevated CO2 under three light-dark regimes (P<0.05). The seedlings showed an obvious higher growth rate and a lower dark respiration rate (Rd) by HL treatment than by ML treatment. The impact of elevated CO2 and illumination time on the photochemical performance was not obvious. Elevated CO2 and longer illumination time had negative effects on chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoids (Car) content. The results suggest that the growth and physiological of seedlings are significantly influenced by elevated CO2 and photoperiod (P<0.05). HC and HL promoted the growth of its seedlings and increased the possibility of outbreak of green tide caused by U. prolifera. This study provides basic data for indepth understanding of the causes of green tide algae outbreak.
Seasonal variatons of digestive tract index, histology characteristics and enzyme activity of Holothuria edulis
TAN Chunming, ZHAO Wang, MA Zhenhua, YU Gang
2022, 18(5): 39-45.   doi: 10.12131/20210356
[Abstract](347) [FullText HTML](94) [PDF 2083KB](19)
To reveal the environmental regulation mechanism and aquaculture of tropical sea cucumber, and provide scientific basis for its artificial breeding, we studied the seasonal variations of physiological and biochemical conditions of Holothuria edulis, monitored the changes of the digestive tract index, histology characteristics and enzyme activities of H. edulis. Results show that the feeding state of H. edulis was relatively vigorous in spring and summer, and exhibited similar characteristics to Stichopus japonicus's aestivation in winter, which is characterized by decline of body mass, atrophy of digestive tract tissue, emergence of a large number of cavities due to cell apoptosis, decrease of the thickness of transverse folds and decrease of the density of columnar epithelium in the intestinal wall structure. The digestive enzymes and immune enzymes activities of the digestive tract tissues were the highest in March and June, respectively. In December, except for the alkaline phosphatase activity that regulates metabolism, all the others were at low values. Therefore, it is preliminarily judged that H. edulis have hibernation phenomenon.
Effect of Haematococcus pluvialis on growth performance, antioxidant capacity and immune responses of Lates calcarifer
YU Wei, CHEN Xueqing, YANG Yukai, ZHANG Yanwa, HUANG Xiaolin, HUANG Zhong, LI Tao, MA Zhenhua, WU Qia'er, YU Gang, ZHOU Chuanpeng, LIN Heizhao
2022, 18(5): 46-54.   doi: 10.12131/20220002
[Abstract](228) [FullText HTML](35) [PDF 729KB](15)
Haematococcus pluvialis is enriched in astaxanthin. To investigate its effects in the diet of Lates calcarifer, we fed L. calcarifer by six diets containing 0 (C), 0.2% (H1), 0.4% (H2), 0.6% (H3), 0.8% (H4) and 1.0% (H5) H. pluvialis for 56 d. The results show that the specific growth rate (SGR) and weight gain rate (WGR) in H2, H3, H4 and H5 groups were significantly higher than those of the control group (P<0.05). Compared with the control group, the whole-body lipid protein content decreased significantly in the treatment groups (P<0.05). The dietary H. pluvialis improved the total antioxidant capacity (T-AOC) significantly (P<0.05), while the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) activities and malondialdehyde (MDA) content were significantly lower than those of the control group (P<0.05). Compared with the control group, the concentrations of red blood cell (RBC), hemoglobin (Hb) and complement 4 (C4) increased (P<0.05) in H3, H4 and H5 groups, but the concentration of low-density lipoprotein cholesterol (LDL-C) decreased significantly (P<0.05). Compared with the control group, the concentrations of cholesterol (TCHO) and triglyceride (TG) decreased significantly (P<0.05), but the lysozyme (LYZ) activity and immunoglobulin (IgM) concentration increased significantly (P<0.05). The regression analysis on the WGR indicates that the recommended optimum dietary H. pluvialis level for the growth of L. calcarifer is 0.66%.
Effects of dietary supplementation of inulin on survival, growth and intestinal microbiota of juvenile golden pompano (Trachinotus ovatus)
LAN Kunpeng, WU Guangde, WANG Jun, CHEN Xu, WANG Yun, ZHOU Chuanpeng, LIN Heizhao, MA Zhenhua
2022, 18(5): 55-65.   doi: 10.12131/20220082
[Abstract](86) [FullText HTML](34) [PDF 901KB](18)
Prebiotics, such as inulin, can promote the growth of beneficial bacteria in the intestinal tract of animals, improve immunity, survival rate and growth performance, and have broad application prospects in the field of animal nutrition and feed. We conducted an 8-week feeding experiment to investigate the effects of dietary inulin on survival, growth performance and intestinal microbiota of juvenile golden pompano (Trachinotus ovatus) [Initial average body mass of (18.85±0.02) g]. Six isonitrogenous and isolipidic basal diets were supplemented with 0 (Control), 0.3%, 0.6%, 0.9%, 1.2% and 1.5% inulin. Results show that 1.5% inulin group had the highest survival rate, significantly higher than the other groups (P<0.05), and no significant difference was found among the other groups (P>0.05). The specific growth rate was the highest in 1.5% inulin group. The hepatosomatic index and intraperitoneal fat were significantly lower in inulin-included groups. The hepatosomatic index first decreased then increased with increasing levels of dietary inulin, with the lowest value in 0.9% inulin group. 1.2% and 1.5% inulin groups had significantly lower hepatosomatic index than the other groups. The fish fed with inulin-included diets had higher gut villus height than that in the control group. Proteobacteria, Firmicutes and Bacteroidetes were the predominant species of intestinal microbiota communities, but their abundance varied. The highest and lowest abundances of Proteobacteria were observed in 1.5% and 0.6% inulin groups, respectively. 0.6% inulin group had the highest abundances of Bacteroidetes and Firmicutes. The lowest abundances of Firmicutes and Bacteroidetes were found in 1.5% inulin group and control group, respectively. The predominant species at genus level were Achromobacter, Brevundimonas and Pandoraea. Achromobacter was most abundant in 1.5% inulin group. 0.6% inulin group had the lowest abundances of Achromobacter, Brevundimonas, Pandoraea, Delftia and Sphingomonas. Inulin supplementation increased the abundances of bacteria that are beneficial to the host such as Achromobacter and Prevotella. The results indicate that dietary supplementation of inulin at 1.5% can improve the survival and growth performance of T. ovatus.
Protective effect of Xiaochaihu Decoction on D-GalN/ LPS-induced hepatocyte injury in hybrid grouper (Epinephelus lanceolatusy♂× E. fuscoguttatus♀)
ZOU Cuiyun, CHEN Xiaojing, WU Yingxin, HUANG Jinxiong, TAN Xiaohong, HU Xinyue, GAN Songyong, WU Jinhui
2022, 18(5): 66-73.   doi: 10.12131/20210362
[Abstract](199) [FullText HTML](82) [PDF 1104KB](9)
The study aims to evaluate the protective effect of Xiaochaihu Decoction (XCHD) on chemical hepatocyte injury. We treated the hepatocytes with D-GalN (20 mmol·L–1) and LPS (1 μg·mL–1) for 24 h to build a hybrid grouper (Epinephelus lanceolatus♂×E. fuscoguttatus♀) hepatocyte injury model, then pretreated the liver cells with different concentrations of XCHD (100, 200 and 400 μg·mL–1) (D-GalN/LPS damage), and measured the hepatocyte viability by the CCK-8 assay. Hepatocyte morphology was visualized by HE staining, and cell supernatants were collected to detect the content of the inflammatory factors INF-, COX-2, and PGE2, as well as the expression of apoptotic and immune-related genes in the cell cryoprecipitate. The results show that XCHD can improve the survival rate of hepatocytes, inhibit INF-γ activity and coX-2 and PGE2 contents in the supernatant of hepatocytes induced by D-GalN/LPS injury to a different extent, reduce LDH, AST and ALT contents and apoptosis rate of hepatocytes. Besides, it had a significant protective effect on the structure of hepatocytes, significantly inhibiting the up-regulation of apoptosis-related genes caspase-3, caspase-9 and P53, and enhancing the up-regulation of immune-related genes TLR3. According to the data from the statistical analysis, the inhibition effect was most obvious in the 200 μg·mL–1 XCHD group. In conclusion, XCHD has a protective effect on the chemical hepatocyte injury of Epinephelus lanceolatus♂×E. fuscoguttatus♀, and can prevent the occurrence and development of liver disease, which provides a new insight for the study of liver protection drugs in fish.
Responses of important virulence factors of Aeromonas veronii to environmental conditions
WANG Qian, DENG Yiqin, SUN Chengwen, LIN Ziyang, SU Wenxiao, LIU Mengyao, CHENG Changhong, GUO Zhixun, FENG Juan
2022, 18(5): 74-80.   doi: 10.12131/20210273
[Abstract](308) [FullText HTML](77) [PDF 838KB](12)
As important pathogenic factors of Aeromonas veronii, flagellin, quorum sensing and Type III secretion system (T3SS) are closely related to their pathogenicity and regulated by various environmental conditions. In order to study the effect of variation in external environmental factors on the pathogenic factors of A. veronii, we used the ascF, fliE and luxR factors of A. veronii as objects by real-time PCR method. The response of ascF, fliE and luxR genes to environmental factors such as temperature, pH, rotating speed and ions were explored at the transcription level. The results show that the three genes of A. veronii had a positive response to acidic environment (pH 6.5−7.0), low and medium speed (150−210 r·min−1), Zn2+ and Mg2+. The response patterns of the three genes of the two strains of A. veronii with different molecular types were different, indicating that the pathogenic mechanisms of A. veronii might be different. Besides, the important virulence factors of A. veronii were regulated by environmental conditions and showed different regular change. The results provide references for further research on the pathogenesis of A. veronii.
Effects of cbpD gene on virulence and related biological characteristics of Vibrio alginolyticus
SU Wenxiao, DENG Yiqin, ZANG Shujun, WANG Qian, LIN Ziyang, FENG Juan
2022, 18(5): 81-90.   doi: 10.12131/20220025
[Abstract](227) [FullText HTML](68) [PDF 1079KB](12)
In order to study the effect of the chitin binding protein D (CbpD) on the virulence and related biological characteristics of Vibrio alginolyticus, we constructed the cbpD gene deletion mutant strain of V. alginolyticus ZJ-T by homologous recombination technique. Then we compared the virulence to Danio rerio and other related physiological processes between the wild type strain and the cbpD gene mutant strain, including the growth ability, motility, extracellular protease secretion activity, hemolytic activity and antibiotic sensitivity, biofilm formation, hydrogen peroxide and copper ion resistance as well as ion absorption capacity. The results show that due to the absence of cbpD gene, the swimming motility, swarming motility and extracellular protease activity all reduced, while the resistance to copper ion of the mutant strain strengthened, and its virulence toD. rerio was weakened. However, the deletion of cbpD gene did not affect the growth of the strain in nutrient-rich medium, biofilm formation, hemolytic activity, stress response to H2O2, uptake and utilization of iron and sensitivity to most antibiotics. In conclusion, the results indicate that cbpD may promote the virulence by positively regulating the motility, extracellular protease secretion activity of V. alginolyticus.
Molecular characterization and expression of MAP2K1 gene in Hyriopsis cumingii
LIU Meiling, SHANGGUAN Xiaozhao, WANG Xiaoqiang, WANG Yayu, WANG Guiling, LI Jiale
2022, 18(5): 91-99.   doi: 10.12131/20210328
[Abstract](216) [FullText HTML](49) [PDF 1342KB](6)
In order to study the role of the MAP2K1 (MEK1) gene in the sex determination of Hyriopsis cumingii, we applied RACE (Rapid-amplification of cDNA ends) method to clone the MAP2K1 gene sequence. We conducted a real-time fluorescence quantitative analysis to compare MAP2K1 gene in six tissues (Gonads, adductor muscle, hepatopancreas, gills, mantle, foot), gonads at early developmental stage (1−8 month old) and the 1−3 years' level of expression in male and female glands of H. cumingii. We determined the location of MAP2K1 gene in the gonads of 2-year-old H.cumingii by in situ hybridization. The results show that the ORF region of MAP2K1 gene was 1 194 bp in length and encoded 397 amino acids. MAP2K1 gene was highly expressed in the ovary; the expression level was the highest at 2 months of age at early developmental stage; the expression results from 1−3 years of age show that the expression of MAP2K1 gene in the ovary was higher than that in the spermatozoa for the same period (P<0.05). The in situ hybridization results show that the MAP2K1 gene had a significant hybridization signal in the oocytes and eggs of female H. cumingii. RNAi results show that the expression of the downstream gene MAP2K1 gene decreased by 82.31% in females and 73.60% in males after interfering with the upstream gene C-MOS gene of MAP2K1 gene. In conclusion, MAP2K1 gene may be involved in the ovarian development process and is a female-biased gene in H. cumingii, and C-MOS gene affects its expression.
Mining of InDel marker and association analysis of hypoxia tolerance traits in Trachinotus ovatus based on resequencing
SAN Lize, LIU Baosuo, ZHANG Nan, GUO Liang, GUO Huayang, ZHU Kecheng, ZHANG Dianchang
2022, 18(5): 100-109.   doi: 10.12131/20210347
[Abstract](257) [FullText HTML](52) [PDF 1455KB](14)
Trachinotus ovatus is a fish with high oxygen consumption rate, and hypoxia can easily lead to its death. Screening for InDel molecular markers for hypoxia tolerance traits in T. ovatus and discovering functional genes affecting hypoxia tolerance traits can provide guidances for selecting and breeding T. ovatus with strong hypoxia tolerance. In this study, we applied the whole genome resequencing technology to analyze the InDel differences of T. ovatus gene, excavated the InDel sites that were significantly associated with hypoxia tolerance traits in T. ovatus, and explored the candidate genes related to hypoxia tolerance traits. Altogether 693.48 Gb was obtained by sequencing, and the average value of Q30 was 90.8%. A total of 2 574 178 InDel markers were found by annotation analysis. A total of 249 395 InDel markers were found in the 50 individuals in the tolerance group, of which 2 209 were located in exons. It is found that there were mutated genes in the nucleotide excise repair signaling pathway and cell adhesion molecules. Three InDel markers (InDel 22883061, InDel 24919481 and InDel 14451779) were found to be close to the significance threshold by association analysis between InDel markers and hypoxia tolerance trait. Nine candidate genes were obtained by annotation analysis. The selected InDel markers were of great value for selecting and identifying molecular marker selection breeding. The annotated candidate genes provide a basis and references for the study of the hypoxia tolerance mechanism of T. ovatus.
Effects of cold stress on black porgy tissue injury and apoptosis gene expression
WEI Mingliang, ZHANG Zhiwei, ZHANG Zhiyong, LIN Zhijie, ZHU Fei, JIA Chaofeng, MENG Qian, XU Dafeng, ZHANG Caojin
2022, 18(5): 110-117.   doi: 10.12131/20210372
[Abstract](366) [FullText HTML](66) [PDF 1974KB](50)
In order to explore the physiological adaptation mechanism of black porgy (Acanthopagrus schlegelii) under low temperature stress, we designed three temperature gradient groups (15, 10 and 5 ℃). Taking 15 ℃ as the control group and with a low temperature stress for 24 h, we studied the tissue structure changes, physiological, biochemical reactions and the expression of apoptosis genes before and after the cold stress. The results show that with the intensification of low temperature stress, the tissue damage such as liver vacuolation, gill lamellae contraction and breakage and muscle fiber breakage were aggravated. The content of triglyceride (TG) in the liver decreased significantly, while the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) as well as the content of total cholesterol (T-CHO) increased significantly, indicating that A. schlegelii had suffered from liver dysfunction and structural damage under cold stress condition. At 10 ℃, the liver reduced the damage of cold stress by decreasing expression levels of apaf-1, bax and caspase-1 genes, increasing expression of caspase-3 and diablo genes so as to reduce the loss of liver cells. When the temperature reached 5 ℃, the temperature exceeded A. schlegelii's physiological regulation threshold, so the degree of liver cell damage was aggravated. The expression of apaf-1, bcl-2 and diablo genes were promoted, while the caspase-3 gene expression was inhibited in order to maintain the homeostasis of liver cells to the greatest extent. It is showed that as the temperature decreased, the liver, gills and muscle damages of A. schlegelii increased. The liver regulated the expression of AST, ALT, T-CHO, TG and apoptotic pathway related genes to reduce the damage caused by tissue damage.
Hydrodynamic performance of Argentine shortfin squid (Illex argentinus) bottom trawl
HAO Yuxin, WAN Rong, ZHOU Cheng, YE Xuchang, GUAN Qinglong, ZHANG Xiaoxian
2022, 18(5): 118-127.   doi: 10.12131/20210343
[Abstract](249) [FullText HTML](60) [PDF 854KB](13)
Illex argentinus, inhabiting in shallow waters with a short life cycle, is an important economic cephalopod in the high seas fishing ground of the southwest Atlantic Ocean. Squid jigging and bottom trawling are the main fishing patterns to catch this species. However, there are some problems in bottom trawl, such as high energy consumption, and poor matching between vessel and trawl. Thus, it is necessary to understand the hydrodynamic performance of bottom trawl for I. argentinus. In this paper, we conducted a model experiment in the dynamic water tank to explore the effects of towing speed, horizontal spreading ratio, buoyancy weight ratio on the hydrodynamic performance of height of net opening, resistance, coefficient of energy consumption and power consumption. The model net was designed based on the small mesh six-panel single boat bottom trawl used for the main capture of I. argentinus [Main scale: 200 m×113.8 m (84.6 m)]. According to the Tauti's Law, the model experiment was scaled with the large scale ratio of 1∶30 and the small scale ratio of 1∶5. When the towing speed V was 3 kn and the horizontal spreading ratio L/S was 0.54, the buoyancy weight ratio increased from 0.6 to 0.7, the height of the net opening increased from 9.66 m to 14.1 m, and the resistance increased from 73.73 kN to 83.48 kN. However, with the increase of towing speed, the influence of the buoyancy weight ratio on the height of the net opening and resistance decreased. When the sweeping area of trawl opening was less than 200 m2, the energy consumption coefficient was greatly affected by the horizontal expansion ratio, on the contrary, it was greatly affected by the height of trawl opening. The power consumption increased with towing speed and horizontal spreading ratio. It accounted for more than 10% of main engine power for vessel when the towing speed was more than 4 kn.
Evaluation of scale effect on hydrodynamic force of V-shaped otter board based on CFD
LIU Jingbin, TANG Hao, XU Liuxiong, SUN Qiuyang, LIU Wei, YIN Liqiang, ZHANG Feng
2022, 18(5): 128-137.   doi: 10.12131/20210355
[Abstract](231) [FullText HTML](60) [PDF 1908KB](9)
The main way to study the hydrodynamic characteristics of the otter board is to build a physical model to measure its hydrodynamic characteristics based on the similarity law. In this study, we analyzed the lift, drag coefficient and flow field distribution of V-type otter board with three scale ratios (1∶2, 1∶3 and 1∶4) and three thickness (2, 5 and 10 mm), then we compared them with the corresponding model test results to explore the influence of different physical model scales on hydrodynamic estimation of the otter boards. The results show that: 1) With the increase of the angle of attack, the drag coefficient of otter board with all scales gradually increased, while the lift coefficient first increased and then decreased, and the lift-drag ratio decreased gradually. 2) When the angle of attack reached 30°, the apparent separation vortex appeared at the back of the otter board, resulting in the decrease of simulated lift force. 3) With the increase of the otter board model scale, the separation effect of the boundary layer on the otter board surface and the separation vortex of the flow field in the wake area increased gradually, and the lift, drag and lift-drag ratio of the otter board also showed an increasing tendency. The thickness of the mesh plate had little effect on the flow field, lift and resistance, and the average error of the maximum lift coefficient relative to the model test was 4.97%. As the model scale increased, the prediction error of hydrodynamic force decreased gradually.
Optimization on calculation method of horizontal illuminance for metal halide fish lamp around fishing boats
WANG Weijie, WAN Rong, KONG Xianghong, XIAO Yuchen
2022, 18(5): 138-144.   doi: 10.12131/20210320
[Abstract](237) [FullText HTML](80) [PDF 1262KB](12)
Monte Carlo simulation is an effective numerical simulation approach to calculate illuminance at target region by discretizing beam into photons and calculating illuminance based on tracking photon path. In order to calculate the horizontal illumination distribution of the fish lamp accurately, taking the metal halide fish lamp as an example, we analyzed and optimized the photon number and photon emission model in the process of Monte Carlo simulation. For the photon number, we carried out the numerical simulation by setting different photon numbers to analyze its influence on the stability of simulation results. Meanwhile, we presented a photon emission optimization model based on the luminosity distribution data of fish lamp and verified by the measured data. The results show that: 1) The larger the number of the simulated photon, the better the stability of the simulation result. Taking the calculation point with a horizontal distance of 5 m from the lamp as an example, when the value exceeded 108, the coefficient variance (CV) was 0.07% and when the value exceeded 1010, the CV was 0.05%. 2) Byusing the optimized model, the mean relative error (MRE) between the simulated and measured data reduced from 0.051 2 to 0.045 3. In addition, we calculated the light field illumination of fishing boats in the actual working environment by using the optimized model, and the average error between the calculated value and measured value was about 0.052 3.
Preparation of active peptide from Pinctada martensii adductor muscle and evaluation of its auxiliary hypoglycemic effect
LIAO Jin, LIN Haisheng, WU Bin, QIN Xiaoming, CAO Wenhong, GAO Jialong, ZHENG Huina, ZHANG Chaohua, TAN Qiqing
2022, 18(5): 145-152.   doi: 10.12131/20210377
[Abstract](288) [FullText HTML](90) [PDF 891KB](10)
To explore the potential nutritional value of shellfish active peptides, we hydrolyzed the adductor muscles of Pinctada martensii, Chlamys nobilis and Atrina pectinate by compound protease and flavor protease, and investigated the effects of protease types, enzymolysis time, pH, temperature and enzyme dosage of the enzymatic hydrolysate on the inhibitory activity on α-glucosidase, so as to screen out the optimal enzymatic hydrolysate and further verify its auxiliary hypoglycemic activity through animal experiments. Results show that the hydrolysate of three kinds of adductor muscle had α-glucosidase inhibitory activity. The enzymatic hydrolysate of P. martensii adductor muscle (EHPA) was most active with enzymolysis time of 3 h, pH of 7.0, enzymolysis temperature of 50 ℃ and enzyme dosage of 5 000 U·g−1. Under these conditions, the inhibitory activity of α-glucosidase was 24.54%, which was related to the content of small molecular pepride. The results of animal experiments indicate that EHPA had the activity of auxiliary hypoglycemia. In summary, EHPA has potential application value in developing functional food for auxiliary hypoglycemic function.
Research Notes
Geostatistics-based study on spatial-temporal distribution of Auxis thazard in South China Sea
ZHOU Xingxing, FAN Jiangtao, YU Jie, XU Shannan, CAI Yancong, CHEN Zuozhi
2022, 18(5): 153-159.   doi: 10.12131/20210327
[Abstract](233) [FullText HTML](76) [PDF 3744KB](25)
In order to study the spatial-temporal distribution characteristics of Auxis thazard, we analyzed the spatial-temporal distribution characteristics and ecological dynamics of Auxis thazard by geostatistical methods based on the data from the light falling-net fishery survey conducted in the South China Sea from 2016 to 2017. The results show that the distribution of A. thazard in the South China Sea was of mainly low-density, and there were few high-density sea areas. The seasonal aggregation characteristics of A. thazard in the offshore shallow waters were obvious, and the resource density index followed a descending order of summer>spring>autumn. The spatial distribution of A. thazard fishery had strong spatial heterogeneity, with the proportion of spatial structure over 75% in the four voyages. The spherical model was the main variation model, and the average main variation range was 1.861 0°. The A. thazard in the South China Sea was obviously characterized by southwest-northeast migration, and its spatial layout had a patch-like spatial distribution. The results can better reflect the spatial-temporal distribution characteristics of the A. thazard fishery in the South China Sea, which provides a scientific basis for its fishery analysis and management.
Effects of salinity stress on oxygen consumption rate, ammonia excretion rate and immune-related enzyme activities of Strombus luhuanus
CHEN Xu, ZHAO Wang, CHEN Mingqiang, TAN Chunming, YU Gang
2022, 18(5): 160-165.   doi: 10.12131/20210346
[Abstract](228) [FullText HTML](52) [PDF 746KB](14)
To investigate the adaptability of salinity stress of Strombus luhuanus, we studied the effects of different salinities [17, 22, 27, 32 (control group) and 37] on the oxygen consumption rate, ammonia excretion rate and immune-related enzyme activities of S. luhuanus by hydrostatic method. The results indicate that the oxygen consumption rate and ammonia excretion rate in the control group were significantly higher than those in the other groups (P<0.05). The activity of total superoxide dismutase showed no difference (P>0.05). Compared with the control group, the catalase activity in hepatopancreas groups increased to varying degrees, while the catalase activity in muscle groups was not significantly different (P>0.05). The peroxidase activities of hepatopancreas in the control group, salinity 27 and 37 groups were significantly higher than those in salinity 17 and 22 groups (P<0.05). The peroxidase activities of muscle in the experimental groups were significantly higher than that in the control group (P<0.05). The lysozyme activities of hepatopancreas and muscle in the control group were significantly higher than those in the other experimental groups (P<0.05). In summary, the oxygen consumption rate, ammonia excretion rate and activities of immune-related enzyme have significant effects on S. luhuanus under salinity stress.
Review Paper
Advances on antibiotic resistance genes (ARGs) in aquaculture environment
LI Danyi, WANG Xunuo, ZHANG Guangju, WANG Zenghuan, HUANG Ke
2022, 18(5): 166-176.   doi: 10.12131/20210207
[Abstract](441) [FullText HTML](95) [PDF 777KB](21)
Antibiotics play a significant role in the disease control of aquatic organisms and output increase of aquatic products. However, long-term abuse of antibiotics can result in the occurrence of antibiotic resistant bacteria (ARB) which harbor antibiotics resistance genes (ARGs) in aquatic organisms. The persistent existence, migration and spread of ARGs in aquaculture environment will potentially cause genetic pollution, destroy the ecological balance, and pose risks to human health. Therefore, how to constrain the spread of antibiotic resistance has attracted global attention. In terms of the research advancement of ARGs in aquaculture environment, this review systematically summarizes the status of ARGs pollution coupled with the source, migration and spread behavior of ARGs and their influencing factors, illustrates the correlations between ARGs and antibiotics, microbial communities and environmental factors, as well as discusses the effect of antibiotics, ARGs and ARB on ecological environment and human health. Thus, the paper reviews the management strategies and removal technologies of ARGs, and proposes the future research directions regarding ARGs, so as to provide references for revealing the pollution mechanism of ARGs and reducing the transmission risk of antibiotic resistance.
Display Method:
Study on relationship between body mass and blood indexes of juvenile Thunnus albacares
LIU Hongyan, FU Zhengyi, YU Gang, MA Zhenhua
 doi: 10.12131/20220077
In order to study the basic blood indexes of artificially bred yellowfin tuna (Thunnus albacares), we determined the concentrations or activities of albumin, triglyceride, total cholesterol, transaminase, lysozyme and phosphatase in its serum (W1: 400−900 g; W2: 900−1 400 g; W3: 1 400−1 900 g) with different body mass. The results show that there were significant differences among the albumin, triglyceride and aspertate aminotransferase groups (P<0.05). The glutamic pyruvic transaminase activity and total cholesterol concentration in W2 group were significantly lower than those in the other two groups (P<0.05). The ascending order of the concentrations of albumin, triglyceride and total cholesterol was W3>W1>W2. There was no significant difference in the alkaline phosphatase activity among the groups (P>0.05). The acid phosphatase activity in W1 group was significantly higher than that in the other two groups (P<0.05), and the lysozyme concentration in W1 group was not significantly different from that in the other two groups (P>0.05). The results reveal that there were differences in the blood indexes among the three groups of different mass; the difference between W2 group and the other two groups was greater, and the difference between W1 group and W3 group was smaller.
Study on distribution characteristics and storage variation of semicarbazide in Macrobrachium rosenbergii
GAO Fangfang, WANG Di, CHEN Shengjun, DENG Jianchao, FENG Yang, PAN Chuang, LI Chunsheng
 doi: 10.12131/20220138
Semicarbazide (SEM) is a toxic substance, which is a marker residue to determine whether Nitrofurazone is used illegally or not. To explore the detection of SEM in Crustacean aquatic products, we detected the SEM content of M. rosenbergii by High Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS). The results show that SEM was detected in different parts of M. rosenbergii, higher in the cephalothorax and shrimp shell [Average: (32.02±3.75) and (26.85±13.90) μg·kg−1], but lower in the muscle and liver [Average: (1.35±0.67) and (5.56±0.87) μg·kg−1], and all exceeded the residue limit standards in China (1 μg·kg−1). The SEM content in the shrimp shell and shrimp meat increased with the prolongation of storage time, but that in the shrimp shell was higher than 1.0 μg·kg−1. Different storage temperatures had a little effect on the SEM content of M. rosenbergii. Therefore, when taking SEM as a marker for Nitrofurazone residue detection of M. rosenbergii, the detection time and background content factors should be considered so as to avoid false judgment; and in order to ensure the authenticity and accuracy of the test results, the crushed shell should be avoided in preparing samples.
Study on tyrosinase inhibitory activity and Cu2+ binding activity of tilapia skin peptides
SONG Yuqiong, HU Xiao, XIANG Huan, CHEN Shengjun, LI Laihao, YANG Xianqing, WU Yanyan, MA Haixia
 doi: 10.12131/20220097
To find out whether the tilapia (Oreochromis spp.) skin collagen peptides can effectively inhibit melanin production, we used three kinds of proteases to hydrolyze the tilapia skin, and filtered the tilapia skin tyrosinase (TYR) inhibitory peptides (TSTIP) with the highest inhibitory activity. Then we studied the relevance between TYR inhibitory activity and Cu2+ binding activity. The results show that the product of tilapia skin hydrolyzed by alcalase for 4 h exhibited both the highest TYR inhibitory activity and Cu2+ binding activity, which were significantly positively correlated (R=0.856). When TSTIP was bound to Cu2+ or tyrosinase, the intrinsic fluorescence absorption had a consistent decreasing trend, but the UV absorption increased and the maximum absorption wavelength had a red shift. For FTIR results, TYR and Cu2+ bound to TSTIP mainly by carbonyl and amino groups. Circular dichroism shows that the β-turn and random curl contents of the two conjugates decreased relatively, while the β-fold content increased relatively, which was more obvious for TSTIP-Cu2+. In conclusion, the structural change of TSTIP-TYR is similar with that of TSTIP-Cu2+, which indicates that TSTIP can inhibit TYR's activity by binding to its Cu2+ active site.
Anesthetic effect and tissue oxidative injury for Litopenaeus vannamei by two anesthetics
WEI Zhengkun, DONG Hongbiao, ZHAO Wen, CHEN Fei, ZHANG Chuanxiang, CHEN Jian, GONG Baohua, ZHU Changbo, ZHANG Jiasong
 doi: 10.12131/20220070
To provide references for the application of two anesthetics in Litopenaeus vannamei, we studied the anesthetic effects of eugenol (20, 30, 40, 60, 80, 100, 120, 140, 160 mg·L−1) and MS-222 (800, 900, 1 000, 1 100, 1 200, 1 300, 1 400, 1 500, 1 600 mg·L−1) on L. vannamei with body mass of (14±3) g. Besides, we tested the secondary stress injury on the physiological functions and pathomorphologic changes by the two anesthetics. The results show that: 1) Eugenol of 80 mg·L−1and MS-222 of 1 400 mg·L−1 induced L. vannamei to enter the stage of deep anesthetic within 3 min, and return to the normal stage within 5 min. 2) The gills and hepatopancreas of L. vannamei were injured by the two anesthetics, and the antioxidant indexes of gills in the eugenol group reached the maximum value earlier than the MS-222 group. The Caspase-3 activity in the eugenol group decreased significantly after anesthesia recovery of 6 h, while that in the MS-222 group increased significantly (P<0.05). The Na+/K+-ATPase activity in both the groups decreased significantly (P<0.05). Pathomorphologic analysis shows that the two anesthetics could cause deformation or lysis of gills and hepatopancreas, and the eugenol group could recover after anesthesia recovery of 6 h. In conclusion, eugenol and MS-222 have anesthetic effects on L. vannamei, but the concentration of MS-222 is higher and the secondary stress damage to the body is more serious.
Effects of dietary supplementation with powder of Antarctic krill (Euphausia superba) on growth performance, body composition and color of Litopenaeus vannamei
LI Wenheng, WANG Haitao, SHAN Hongwei, GAO Chang, LI Jiqing
 doi: 10.12131/20220074
To determine the application effect of Euphausia superba powder (PE) in shrimp culture, we designed five groups [S0 group (No PE supplementation), S5 group, S10 group, S15 group, and S20 group (5%, 10%, 15% and 20% PE supplemented to the feed, respectively)] for a 35-day experiment on Litopenaeus vannamei [Body mass of (7.27 ± 0.88) g]. The effect of dietary supplementation with PE on the growth performance, body composition and color of L. vannamei were evaluated. The results show that: 1) PE supplementation improved the survival rate (SR) of L. vannamei significantly (P<0.05), and the final body mass (FBW), weight gain rate (WGR) and specific growth rate (SGR) of L. vannamei in S15 group were significantly higher compared with the other groups (P<0.05). 2) With the increase of PE supplementation, the crude fat content of L. vannamei increased gradually, and those in S10 group, S15 group and S20 group were significantly higher than that in S0 group (P<0.05). Additionally, the brightness (L*) of the cephalothorax and the yellowness (b*) of the carapace of L. vannamei decreased gradually, which were significantly lower than those in S0 group (P<0.05). 3) PE supplementation to the feed increased the astaxanthin content in the hepatopancreas and crustacean of L. vannamei significantly (P<0.05), and the effect was positively associated with PE supplementation. The expression level of the LVPBP75 related to body color was also positively correlated with PE supplementation. The results indicate that dietary supplementation with PE, especially with 15% PE, can improve the growth, astaxanthin content, body color as well as expression level of LVPBP75 of L. vannamei.
Heavy metal enrichment characteristics and risk assessment of typical fishes in tropical seagrass beds
JIANG Rui, WU Yunchao, HUANG Xiaoping, LIU Songlin, CHEN Qiming
 doi: 10.12131/20220118
The ingestion of seagrass by herbivorous fish will affect the transfer process of metal elements in seagrass beds, and the accumulation of heavy metals will cause human ingestion risks. Taking two typical fish species (Siganus guttatus and S. fuscessens) eating seagrasses in two tropical seagrass beds as main research objects, we determined the enrichment of heavy metals and their contamination, and assessed the dietary exposure risk in seagrass bed environment and fishes. Then we further explored the transfer characteristics of heavy metals in seagrass bed ecosystems. The results show that the contents of Cu, Cd, Zn and Pb in fish muscles were at a low level. There are significant positive correlations between Cu and Pb, and between Zn and CD. The enrichment effects of Zn and Cu were greater than those of Cd and Pb, but only Zn showed an potential enrichment effect in these two fish muscles. The Zn contents in these two fishes showed a serious pollution risk, while Pb contents showed slight pollution, but the contents of Cu and Cd were at a normal risk level. Eating these two fishes has little health risk. Due to the different growth rate and food sources, the content, pollution and enrichment of heavy metals in S. fuscessens are slightly higher than those in S. guttatus. The contents and enrichment of heavy metals in seagrass beds are generally higher than those in fishes. The accumulation of heavy metals mainly occurs in seagrass, and the heavy metal content in fish decreases with higher trophic levels.
Genetic diversity and population structure of Gymnocypris przewalskii based on SNP markers
LUO Hui, FANG Di'an, HE Miao, MAO Chengcheng, KUANG Zhen, QI Hongfang, XU Dongpo
 doi: 10.12131/20220091
To investigate the genetic diversity and genetic differentiation of natural resources of Gymnocypris przewalskii, and provide references for its conservation measures, we collected 72 individuals of G. przewalskii from six natural populations in Qinghai Lake to analyze the genomic SNP and genetic characteristics by using simplified genome sequencing. Altogher 1 600 061 SNP markers were obtained, and 45 266 high-quality SNP loci were screened for genetic analysis after filtering. The average Pi diversity index was 0.317 0–0.327 4. The average observed heterozygosity (Ho) and expected heterozygosity (He) were 0.459 4–0.482 3 and 0.336 7–0.344 4, respectively. The genetic distance (D) was 0.018 4–0.023 3 and the genetic differentiation index (Fst) were not significant (P>0.05). AMOVA analysis shows that the genetic variation was 102.37% within populations. Further more, both population structure and phylogenetic tree analysis show that the six G. przewalskii populations clustered into one glade with similar genetic structure. In contrast, the genetic structure obtained from DAPC analysis was relatively clearer, showing that the Haergai, Heima and Shaliu River populations cross-clustered with each other, while the remaining three populations clustered into three other branches. In conclusion, the observed heterozygosity of the six geographic populations was higher than the expected value, with a homogeneous population structure.
Spatio-temporal distribution of habitat patterns of Scomber japonicus in East China Sea under future climate conditions
WU Xiaoci, FENG Zhiping, YU Wei
 doi: 10.12131/20220126
To investigate the effects of global climate change on the habitat pattern of Scomber japonicus in the East China Sea and to slow down the adverse effects of climate change on the fishing ground of S. japonicus, based on the water temperature data of 2.5 m (Temp_2.5 m), 25 m (Temp_25 m) and 50 m (Temp_50 m) output by CMIP6 climate model, we analyzed the spatio-temporal changes of the habitat in the East China Sea under three future climate conditions (SSP126, SSP370 and SSP585). The results show that for SSP126, Temp_2.5 m, Temp_25 m and Temp_50 m showed relatively minor changes. For SSP370 and SSP585, Temp_2.5 m, Temp_25 m and Temp_50 m showed an overall upward trend. The three factors also changed in the spatial distribution during 2015−2020, 2055−2060 and 2095−2100. The habitat suitability index (HSI) on the fishing ground and proportion of suitable habitat of S. japonicus in the East China Sea from 2015 to 2100 showed a similar downward trend under SSP126, SSP370 and SSP585 conditions. However, the proportion of unsuitable habitat area from 2015 to 2100 increased under SSP126, SSP370 and SSP585 conditions. The suitable habitats of S. japonicus were mainly distributed in the waters of 122°E−126°E and 28°N−30°N during 2015−2020, 2055−2060 and 2095−2100, while the unsuitable habitat was mainly distributed in the middle of fishing ground. In addition, the gravity center of suitable habitat of S. japonicus tended to move northward. The results suggest that the global warming is unfavorable for the formation of suitable habitat of S. japonicus in the East China Sea.
Ecological health assessment of Cyprinus carpio and Leiocassis longirostris national aquatic germplasm resources reserve in Huaihe River
WANG Dongwei, CHEN Yongjin, FANG Di'an, ZHOU Yanfeng
 doi: 10.12131/20220109
In order to explore the water ecological health status of Cyprinus carpio and Leiocassis longirostris national aquatic germplasm resources reserve in Huaihe River, according to the survey results of phytoplankton community structure in 2020 and combined with the morphological functional group classification, we constructed the ecological health evaluation system of the reserve based on the biological integrity index of phytoplankton. Besides, we carried out the Mann-Whitney non-parametric test and correlation analysis of the candidate parameters to determine the final evaluation parameters, and used the ratio method to determine the grading evaluation standard for the evaluation of the health status of the reserve water. The results show that the evolution trend of dominant functional groups of phytoplankton was III+IV+V (Spring)→III+IV+V+VI (Summer)→V+VI (Autumn)→IV+V+VI (Winter). Except that the dominant functional groups in the core area were III+ IV+V+VI, the dominant functional groups of the experimental area, the Guo river and the Huaihe River were III+IV+V+VI. 68.06% of the sampling sites in the reserve were evaluated as "average" or above, indicating that the overall water ecological health status was good. Specifically, the temporal pattern of winter was better than autumn, followed by summer, and the worst was in spring; the spatial pattern of Huaihe River mainstream was better than Guohe River, and the experimental area was better than the core area.
Establishment of reverse transcription droplet digital PCR assay for detection of Tilapia Lake Virus
LI Min, LI Yongfu, HUANG Yuhao, CHEN Zhuojun, MO Zuanlan, ZHONG Qunfang, LI Benwang, ZHANG Xianpeng
 doi: 10.12131/20220184
To establish an assay of reverse transcription droplet digital PCR (RT-ddPCR) for Tilapia Lake Virus (TiLV), we designed a pair of specific primers and probe based on the conserved region of TiLV segment 3 and evaluated the specificity, sensitivity and repeatability of this method. The structured standard curve was evaluated by using TiLV-cDNA as a template. Finally, the samples were tested. When the concentrations of primers and probes were 500 and 300 nmol·L−1 and the annealing temperature was 54.2 ℃, the established TiLV RT-ddPCR amplification reaction efficiency was the highest, the distribution boundary of the positive and negative droplets was the most obvious, and the average copy number was higher. The RT-ddPCR of TiLV had a lower limit of detection with 2 copies·μL−1 and showed a good linear relationship between 1–90 000 copies·μL−1 (Correlation coefficient R2=0.995 8). There was no amplification reaction to other viruses in aquatic animals. The CV of ddPCR for TiLV-cDNA was 4.86%. There was no cross reaction with the positive samples of other five common aquatic animal disease viruses [Carp edema virus (CEV), Koi herpesvirus (KHV), Grass carp reovirus (GCV), Cyprinid herpesvirus 2 (CyHV-2), Red sea bream iridovirus (RSIV)]. Among the 53 detected samples, 48 were negative, three of five proficiency testing samples were positive, consistent with satisfactory previous proficiency testing results. Thus, a more sensitive, specific, repeated molecular biological detection method for TiLV was established, which can be used for early rapid diagnosis and provided a technical support for the differential diagnosis of TiLV disease. The method provides references for TiLV infection.
Effects of Bacillus on growth and survival, immunity and digestive enzyme activities of Babylonia areolata
ZHANG Yuwei, ZHAO Wang, DENG Zhenghua, HUANG Xingmei, WEN Weigeng, SUN Jingfeng, WANG Ruixuan
 doi: 10.12131/20220060
In order to explore whether Bacillus can replace antibiotics in the culture of Babylonia areolata, during the growth and development of B. areolata from early veliger larva to juvenile, we used Bacillus (Bacillus coagulans, B. licheniformis) and antibiotics (sulfamethoxazole) for artificial regulation to study their effects on the growth, survival, immune and digestive enzyme activities of B. areolata. The results show that Bacillus and sulfamethoxazole promoted the growth of each trait index of B. areolata, and the difference among them was not significant (P>0.05). The survival rate of the Bacillus group was significantly higher than that of the control group and the sulfamethoxazole group in the later veliger larva stage (P<0.05). The activities of AKP, ACP, CAT, POD, MDA, GSH-Px, TAOC, SOD, LPS and AMS in Bacillus group were higher than those in the control group and the sulfamethoxazole group. The results show that appropriate use of Bacillus (B. coagulans and B. licheniformis) during the seedling breeding of B. areolata can improve the immunity and disease resistance of the body, increase the activity of digestive enzymes, promote the growth of larvae and improve the survival rate, and the effect is better than that of sulfamethoxazole.
Morphological development and growth of larvae, juvenile and young red saddleback clownfish (Amphiprion ephippium)
LI Tao, HUANG Xiaolin, YANG Yukai, LIN Heizhao, HU Jing, PENG Jiacheng, HUANG Zhong, YU Wei
 doi: 10.12131/20220059
In order to study the early developmental characteristics of red saddleback clownfish (Amphiprion ephippium), and provide a theoretical reference for its breeding we had continuously observed and analyzed the morphological and growth characteristics of larvae, juveniles and young individuals. The body of 0 dah (Days after hatching) individuals (Total length 4.472‒6.152 mm) was translucent with obvious fin membrane, only a small part of yolk sac remaining, and feeding had been started. For 7 dah individuals (Total length 5.213‒12.985 mm), the fin membrane disappeared, and the development of each fin basically completed and the bands began to appear on the head, entering into juvenile stage. Then bands began to appear in the middle of the body and fully formed on the head. For 23 dah individuals (Total length>7.652 mm), the whole body was covered by scales, and the bands in the middle of the body extended to the abdomen, with yellow fins, and the trunk was mainly red pigment and yellow pigment, entering young fish stage. For 28 dah individuals, the middle band fully formed, then the bands gradually disappeared from the middle. For 130 dah individuals, the middle band disappeared completely, while the head band disappeared completely until about 160 dah. At this time, the shape and body color of young fish were the same with that of adult fish. In general, the growth of larval, juvenile and young of A. ephippium showed a trend of slow-rapid-slow trend with the increase of age. The formation and disappearance of white band on the head and middle part of the body were the most obvious features during the early development stage of A. ephippium.
Comparison and optimization of total phosphorus determination method in mariculture tailwater
LIU Yan, TONG Fei, CHEN Pimao, YUAN Huarong, FENG Xue
 doi: 10.12131/20220056
In order to improve the efficiency of the determination of total phosphorus (TP) in the mariculture tailwater, we determined the TP content by microplate reader instead of spectrophotometer in mariculture tailwater, and optimized the digestion method of TP, the type of microwell plate and the amount of sample. The results show that there was no significant difference between 60 min of digestion using a temperature-controlled heating plate and 30 min of digestion using an autoclave (P>0.05). The sensitivity of the assay was better than those of the other experimental groups (200 µL for 96-well plate, 200 µL for 96-well quartz plate, 200 and 500 µL for 48-well plate, 500 µL and 1 mL for 24-well plate) when using a 48-well plate with 1 mL of sample. The linear correlation between phosphate concentration and absorbance was the best (R2=0.999 9) for the 48-well plate with 1 mL and the 96-well plate spiked with 200 µL. The accuracy and precision validation of TP determination in mariculture tailwater showed that the relative error (RE) and relative standard deviation (RSD) of the 48-well plate spiked with 1 mL were higher than those of the other experimental groups (96-well plate 200 µL, 96-well quartz plate 200 µL, 48-well plate 200 µL and 500 µL, 24-well plate 500 µL and 1 mL). The recoveries of disodium glycerophosphate (β-GLP) and sodium hexametaphosphate (SHMP) were 98.2%−99.6% and 93.4%−97.1%, respectively, and the limit of quantification (LOQ) of TP were 0.25 µmol·L−1; the RE and RSD of 96-well ELISA plate spiked with 200 µL were −14.03%−0.21% and 2.63%−14.23%, respectively, and the recoveries for β-GLP and SHM were 94.7%−99.0% and 88.9%−97.3%, respectively, and the LOQ of TP was 0.55 µmol·L−1. At TP concentration of 0.55−6.4 µmol·L−1, the accuracy and precision of the two optimized methods meet the determination requirements and can be used for the determination of TP in mariculture tailwater.
Study on lipid accumulation and contribution to reproductive energy in female Illex argentinus
SONG Wei, ZANG Na, FENG Yixuan, LIN Dongming
 doi: 10.12131/20210348
To explore the accumulation of tissue fat and its contribution to reproductive energy during gonadal development of Illex argentinus has important theoretical value for understanding its reproductive investment strategy, as well as the sustainable development and utilization of resources. By using tissue energy density measurement technology and fat extraction technology, we measured and analyzed the energy density of mantle soma, digestive gland, ovary and oviduct eggs of female I. argentinus before and after degreasing, as well as the fat content per unit mass, fat energy and proportion of each tissue. Results indicate that the energy density of all tissues decreased significantly after lipid extraction. During the maturation, female I. argentinus maintained a relative stable level of the lipid content and percentage of lipid energy in mantle soma and oviduct eggs. However, there was a significant decreasing trend in the lipid content and percentage of lipid energy in the digestive gland but an increasing trend in the ovary (Maximum in Phase IV) along with maturation. Furthermore, Pearson's r analysis indicates that there was a significantly negative relationship in the lipid content, lipid energy and percentage of lipid energy between gonadal tissues (Combination of ovary and oviduct eggs) and digestive gland, but without a significant relationship between gonadal tissues and mantle soma. In summary, female I. argentinus exhibits tissue-specific lipid content and lipid energy accumulation. The lipid content has a significant contribution to the reproductive energy, and lipids in the gonadal tissues are apparently derived from concurrent food intake, which further supports the argument that energy allocation to reproduction in I. argentinus mainly depends on the income resources.
Study on habitat of Coilia mystus in Pearl River Estuary, China
XIE Yufang, WU Peng, LIU Yong, XIAO Yayuan, TANG Guanglong, WANG Teng, LIN Lin, LI Chunhou
 doi: 10.12131/20220029
Exploring the habitat suitability of Coilia mystus, a migratory fish in the Pearl River estuary, can provide scientific basis for the protection and utilization of fishery resources of C. mystus. Based on the date collected by bottom-trawl in the Pearl River Estuary during winter in 2019 and summer in 2020, we constructed the habitat suitability index (HSI) model of C. mystus, taking the water depth, bottom salinity, bottom temperature, as well as bottom dissolved oxygen as indicator environment indicators. The analytic hierarchy process (AHP) was used to calculate the weight of the indicators. The arithmetic mean (AMM) and the geometric mean (GMM) were used to build a model. Then a suitability curve was developed and the HSI of C. mystus was calculated. Results show that the optimal bottom salinities for C. mystus in the Pearl River Estuary in winter and summer were 21.03−30.55 and 20.25−25.82, respectively; the mass concentrations of suitable dissolved oxygen were 6.79–7.28 and 3.85–4.01 mg·L−1, respectively; the suitable water depths were 11.69–20.10 and 7.80–9.23 m, respectively; the suitable bottom temperatures were 19.84–19.95 and 28.36–9.44 ℃, respectively. The sites with HSI value greater than 0.5 accounted for 17.39% of the total survey sites. The study shows that the suitability of C. mystus was low, and its suitable habitats in the Pearl River Estuary are mainly located in the Sousa chinensis Nature Reserve in the Neilingding sea area.
Effects of different light intensity on plasma biochemical indices of Euthynnus affinis on sunny and cloudy days
WANG Wenwen, ZHOU Shengjie, HU Jing, FU Zhengyi, XIAO Bo, DU Hengyi, YANG Rui, YU Gang, MENG Xiangjun, MA Zhenhua
 doi: 10.12131/20220224
Illumination is an important factor in aquaculture. Exploring the changes in the plasma physiology and biochemistry of Euthynnus affinis can provide references for the regulation of its optimal environmental factors. We designed four sampling time to investigate the light intensities on sunny days [2.7 lx (6:00), 1 116 lx (12:00), 913 lx (18:00) and 1 lx (24:00)] and those on cloudy days [1.9 lx (6: 00), 698 lx (12:00), 192 lx (18:00) and 1.4 lx (24:00)], so as to study the changes in the plasma cortisol, total cholesterol, triglyceride, malondialdehyde content, myeloperoxidase activity, lysozyme activity and immunoglobulin M concentration. The results show that there was no significant difference in the cortisol, malondialdehyde concentration and lysozyme activity among the four groups on sunny days, but all reached the maximum at 18:00 on cloudy days. Besides, the concentraions of cortisol and malondialdehyde were significantly higher than those at 18:00 on sunny days (P<0.05), while the lysozyme activity was significantly lower than that at 18:00 on sunny days (P<0.05). The total cholesterol content reached the maximum at 12:00 on sunny day and 18:00 on cloudy day, with no significant difference on sunny day and cloudy day at 12:00. However, it was significantly higher at 18:00 on cloudy days than on sunny days. The triglyceride content and myeloperoxidase activity reached the maximum both on sunny and cloudy days at 6:00, without significant difference. The immunoglobulin M concentration reached the maximum at 24:00 both on sunny and cloudy days, and it was significantly lower on sunny days than on cloudy days at 24:00 (P<0.05). The results show that the E. affinis is more suitable for surviving on sunny days, but it can adapt to the changes of light intensity in different weather by its active physiological adjustment, thereby reducing the damage of environmental factors to its physiological and immune functions.
Spatio-temporal changes of bacterioplankton communities in Litopenaeus vannamei desalinated ponds and their responses to physicochemical factors
QI Feng, SHAWUTI Rebiguli, XIAN Yulan, HAN Junjun, MINAWAER Muyiti, CHEN Hanfei, SUN Shiping, MA Yanwu, CHEN Peng
 doi: 10.12131/20220192
The regulation of bacterioplankton is the core content of the environmental control strategy in shrimp agriculture. Exploring the general rules of the construction of bacterioplankton community can further promote the research on water quality regulation for shrimp ponds. Using 16s rRNA high-throughput sequencing technology, 12 weekly surveys were conducted in Litopenaeus vannamei desalinated ponds.The results indicate that a total of 2 854 OTUs (97% similarity) were obtained from 48 samples (Archaea belonged to 2 phyla, 1 class, 1 family and 1 genus and bacteria belonged to 30 phyla, 59 classes, 98 orders, 199 families and 433 genera, among which 25 genera were dominant flora). The dominant flora had high similarity in the composition, but with great differences in the distribution and relative abundance in each pond. The total average phylogenetic diversity index was 77.57, ranging from 24.39 to 111.65; the total average Shannon diversity index was 3.96, ranging from 2.64 to 5.06; the total average species richness index was 716, ranging from 229 to 1 054. NMDS analysis shows that the community structure of bacterioplankton in each pond varied greatly at the early stage of aquaculture, but not so greatly at the middle and late stages. The results of redundancy analysis shows that the labile phosphorus, total alkalinity, dissolved oxygen and sulfide were the main environmental factors affecting the distribution characteristics of community structure of bacterioplankton.
Effects of different crosslinking agents on properties of agar/sodium alginate composite films
WANG Pai, YANG Shaoling, QI Bo, YANG Xianqing, LI Chunsheng, WANG Di, ZHAO Yongqiang, LI Laihao, HU Xiao, CHEN Shengjun
 doi: 10.12131/20220134
In order to improve the application performance of agar/sodium alginate composite membrane, we used agar and sodium alginate as film-forming base material, glycerol as plasticizer, ferulic acid, tannin acid, citric acid and succinic acid as crosslinking agents to prepare the agar/sodium alginate composite films by solution casting method. Then we studied the effects of four crosslinking agents on the properties of the composite films based on the mechanical properties, water resistance, moisture resistance, opacity, fourier transform infrared spectroscopy (FT-IR) and microstructure of the composite films. The results show that the four crosslinking agents improved the tensile strength, water resistance and moisture resistance of the composite films significantly (P<0.05), but reduced the transparency significantly (P<0.05). The crosslinking agents had the best improvement effect on the composite films with additions of ferulic acid and tannin acid of 5%, citric acid and succinic acid of 10%. Among the four crosslinking agents, citric acid cross-linked film had the best performance, and when the addition of citric acid was 10%, each index reached the optimal values [The tensile strength was 46.98 Mpa; the elongation at break was 17.87%; the water solubility was 24.17%; the swelling ratio was 38%; the water vapor permeability (WVP) was 0.51 g·mm·(m2·h·KPa)−1]. FT-IR analysis shows that citric acid and succinic acid improved the properties of the composite films by esterifying with −OH of agar and sodium alginate, and ferulic acid or tannin acid achieved crosslinking by forming intermolecular hydrogen bonds with agar and sodium alginate. Scanning electron microscopy (SEM) analysis shows that agar and sodium alginate had good compatibility, and the cross section of composite film became denser and smoother with the addition of crosslinking agents. Therefore, moderate addition of crosslinking agent to agar/sodium alginate composite films can improve the physical and chemical properties of composite films at different degrees, which provides scientific references for the preparation and application of packaging films.
Characterization and expression analysis of ho1 from Sander lucioperca under acute hypoxia stress
JI Yudan, SUN Zhipeng, LYU Weihua, LU Cuiyun, CAO Dingchen, LIU Tianqi, ZHOU Jia, ZHENG Xianhu
 doi: 10.12131/20220187
Sander lucioperca is extremely sensitive to hypoxia, and is prone to hypoxia stress and death during intensive breeding and seedling transportation. In order to investigate the regulating effect of heme oxygenase 1 (HO1) in the response to hypoxia of S. lucioperca, we cloned the full-length cDNA sequence of ho1 gene by RACE (Rapid amplification of cDNA ends) technology. The results indicate that the cDNA length was 1 256 bp (840 bp ORF, 162 bp 5'-UTR and 254 bp 3'-UTR), encoding 279 amino acids. The multiple sequence alignment shows that the similarity of Ho1 with Siniperca chuatsi, Dicentrarchus labrax and Micropterus salmoides was 91.84%, 88.69% and 88.11%, respectively. Real-time quantitative PCR discloses that ho1 was expressed in all the tested tissues, with the highest concentration in the brain, followed by the kidney, liver and gills. During the first 3-hour hypoxic stimulation of Pikeperch, ho1 primarily responded in the skin and gills. But after 3 h of hypoxic stress, ho1 mainly played transcriptional regulatory roles in the heart, liver and kidney. At 12th hour of reoxygenation, the expression levels of ho1 in all the tissues except the liver returned to a normal level, and hypoxia stress had an enormous effect on the expression of ho1 in the liver. The study reveals that ho1 gene is involved in the molecular regulation mechanisms of S. lucioperca in response to hypoxia and plays an important biological role, which provides theoretical references for the understanding of the genetic mechanism of hypoxic stress.
Effects of egg product on growth performance, muscle nutrients, and intestinal microflora of Procambarus clarkii
XIAO Wenfu, HU Bing, CUI Xuehai, CAO Manxia, YAO Haihang, LI Peng, YU Lijuan, YUAN Hanwen, GAO Weihua, TIAN Juan
 doi: 10.12131/20220128
To evaluate the application effect of spray-dried egg product in the diet of Procambarus clarkii, we formulated five isonitrogenous and isoenergetic diets containing 0% (Control group), 2.0%, 4.0%, 6.0% and 8.0% spray-dried egg product, which replaced 0% (CON), 25% (R1), 50% (R2), 75% (R3) and 100% (R4) fishmeal, respectively, to feed the shrimps [Initial body mass (9.02±0.12) g] for six weeks. The results show that there were no significant differences in the specific growth rate, feed conversion ratio, feeding rate, survival rate and hepatosomatic index among all the groups (P>0.05). The weight gain rate in R4 group decreased significantly compared with the CON group (P<0.05). The contents of crude protein, essential amino acid and total amino acid in abdominal muscle in R4 group increased significantly compared with the CON group (P<0.05). The contents of crude fat and ash in muscle in R2, R3 and R4 groups were significantly higher than those in the CON group (P<0.05). There were no significant differences in the contents of 17 hydrolyzed amino acids in muscle among all the groups (P>0.05). Compared with the CON group, the intestinal protease activities increased significantly but the amylase activities decreased significantly in egg product supplementation groups, and the intestinal lipase activity increased significantly in R3 and R4 groups (P<0.05). The serum alkaline phosphatase activity and total protein content in R2, R3 and R4 groups increased significantly than those in the CON group (P<0.05). The bacterial abundances of Clostridium sensu stricto and Lysobacter in R3 group were significantly higher than those of the other groups, while the bacterial abundance of Streptococcus in R4 group was significantly higher than that of the other groups (P<0.05). In conclusion, when the diet of P. clarkii contains 6% fishmeal, the spray-dried egg product can replace 75% fishmeal.
Effects of fermented Astragalus membranaceus on growth, digestion, immune function and ammonia nitrogen resistance of Epinephelus fuscoguttatus
XIAO Bo, ZHOU Shengjie, WANG Yinggang, FU Zhengyi, FANG Wei, YU Gang, MA Zhenhua
 doi: 10.12131/20220197
To develop a new type of aquatic feed additive for promoting growth and enhancing immune function, we cultured Epinephelus fuscoguttatus with body mass of (44.48±2.06) g for 56 d by adding fermented Astragalus membranaceus with proportions of 0% (Control group), 0.25%, 0.5%, 1%, 2% and 4% (L0, L1, L2, L3, L4 and L5 groups), and then conducted an ammonia nitrogen stress test. Taking growth, digestion and immune function as the indicators, we evaluated the physiological, biochemical and stress-resistant effects of fermented A. membranaceus on E. fuscoguttatus, and determined the optimal ratio. The results show that: 1) Compared with the control group, the addition of fermented A. membranaceus increased the weight gain rate (WGR) and specific growth rate (SGR), as well as the activities of digestive enzymes in gastrointestinal tract significantly (P<0.05), but reduced the feed conversion ratio (FCR) of E. fuscoguttatus in L3 and L4 groups significantly (P<0.05). 2) Before the ammonia nitrogen stress, fermented A. membranaceus increased the liver antioxidant performance significantly (Except L5 group, P<0.05), but decreased the liver malondialdehyde (MDA) content and serum glutamic-oxalacetic transaminase (GOT) activity significantly (P<0.05). The serum glutamic-pyruvic transaminase (GPT) activity, glucose (GLU) concentration and serum triglyceride (TG) concentration in L3, L4 and L5 groups were significantly lower than those in the control group (P<0.05). 3) After the ammonia nitrogen stress, fermented A. membranaceus did not improve the antioxidant performance of liver, but reduced the MDA content in liver (Except L5 group), the activities of GOT and GPT as well as the GLU concentration in serum (Except L4 and L5 groups) significantly (P<0.05). In conclusion, the recommended feed additive proportion of fermented A. membranaceus is 1%–2%.
Genetic structure and demographic history of Mastacem- belus armatus in southern China
GAO Shang, LI Yuefei, LI Jie, CHEN Weitao
 doi: 10.12131/20220200
In order to understand the genetic resources of Mastacembelus armatus populations in southern China, and provide important scientific basis for the management and protection of the genetic resources of M. armatus, we collected 140 individuals from 16 geographical populations from seven independent river systems in southern China and sequenced two mitochondrial genes (COI and Cytb) via PCR amplification and Sanger sequencing, and finally revealed the genetic structure and demographic history of M. armatus populations by phylogenetic analysis, haplotype network, population genetic analysis and Bayesian skyline plot. The results show that M. armatus populations consisted of three lineages (I, II and III) and split between 0.596 and 0.676 million years ago (Ma). Haplotype network shows that there was a common domain distribution among different lineages, and suggests that there might be two diffusion routes between Hainan Island population and mainland population. Population genetic analysis finds significant genetic differentiation (FST=0.676, P<0.001) and isolation by distance pattern (R=0.463, P=0.001) among M. armatus populations, implying that spatial distance was an important factor for genetic differentiation of M. armatus. Demographic analysis shows that M. armatus populations experienced population expansion at 0.025 Ma.
Effects of nitrite and microplastic stress on immune, detoxification metabolism and osmoregulation-related indicators in gills of Litopenaeus vannamei
XING Yifu, DUAN Yafei, WEI Zhengkun, ZHU Xuanyi, HUANG Jianhua, ZHANG Jiasong
 doi: 10.12131/20220176
In order to investigate the effects of single and combined stress of nitrite and microplastics on the physiological functions of gill tissues of Litopenaeus vannamei. We designed the control group, 20 mg·L−1 nitrite stress group (NIT), 10 μg·L−1 microplastic stress group (MP), 20 mg·L−1 nitrite and 10 μg·L−1 microplastic composite stress group (NM), and then measured the changes of immune and osmotic regulation in gills of shrimps on the 14th day. The results show that: 1) The oxidative stress indicators such as the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2), and the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) changed in different degrees after the stress. 2) The detoxification metabolic indicators such as the relative expression levels of cytochrome P450 (CYP450), glutathione S-transferase (GST) and apoptosis factor (CASP-3) were disturbed in different degrees after the stress. 3) The relative gene expression levels of the osmoregulation indexes such as ion transporters (VATP, NHE, NKA-α, NKA-β and CA) and channel proteins (TIP4, CCP, CLC and AQP) occurred in different degrees of disorder after the stress. 4) The apoptosis index sucha as the relative expression level of apoptosis factor (CASP-3) gene decreased significantly in the three groups (P<0.05). Thus, it is inferred that nitrite and microplastic stress can induce the changes of immune, detoxification metabolism and osmotic regulation in the gills of L. vannamei, affecting its normal physiological functions.
Effect of different flow velocity on tail beat frequency and blood physiology of Plectropomus leopardus
QIAN Zhenjia, XU Jincheng, ZHANG Chenglin, YU Youbin, LIU Huang
 doi: 10.12131/20220153
Water flow is one of the important ecological factors that affect the physiology and growth of fish. Studying the stress level changes of Plectropomus leopardus under flow velocity stress, and clarifying the maximum flow velocity that the fish can tolerate, can provide a theoretical basis for the cage culture site selection, intensive flow culture and deep-sea industrial boat culture. Taking P. leopardus [Body length (11.38±1.48) cm, body mass (34.71±11.57) g] as the research object, we designed a hydrostatic control group (0 cm·s−1 or 0 BL·s−1, body length·s−1) and three experimental groups (11.4, 22.8 and 34.2 cm·s−1 corresponding to 1, 2 and 3 BL·s−1) by a self-made fish swimming experimental device, so as to explore the effect of 40-min water flow stimulation on its tail swing frequency change, blood glucose, lactic acid and cortisol content in blood. The results show that there was a linear correlation between the tail beat frequency and water velocity. The blood glucose and cortisol levels increased linearly with the number of tail beat, but the lactate increased non-linearly with the number of tail beat. The flow rate over 2 BL·s−1 resulted in a significant increase in cortisol in the blood of P. leopardus (P<0.05). When the flow rate reached 3 BL·s−1, the blood lactate and blood glucose levels increased significantly (P<0.05). In conclusion, the upper limit of tolerance to flow velocity of P. leopardus was 2 BL·s−1. When the flow velocity of cultured water was higher than 2 BL·s−1, the stress level and metabolic load increased significantly and the stress effect appeared (P<0.05). The results provide references for the farming workboat system of swinging and the site selection of net tank culture waters.
Truss rod trajectory planning based on cubic B-spline curve and Dynamic Window Algorithm
DAI Yang, YAO Yuqing, ZHENG Hanfeng, WEI Bo, YANG Yuhao, WANG Yongjin, ZHANG Yu
 doi: 10.12131/20220048
Aiming at the current low level of automation in the fishing of Antarctic krill (Euphausia superba) in China, and the error in determining the fishing depth by manually observing the fish detector image, a dynamic truss trajectory planning method based on the metadata of Antarctic krill sonar equipment is proposed. First, we analyzed the data sent back by the underwater acoustic instrument EK80 scientific echo sounder, obtained the target intensity of krill at different depths, and used statistical methods to determine the resource of krill at this depth, so as to get the densest depth (Y) of krill corresponding to each horizontal distance (X). Then we used cubic B-spline curve and Dynamic Window Algorithm to carry out the global path planning and local path planning. The planned route passed through the densest depth of these krill. The results show that the total length of the planned path was 1 054 m, and the total time was 614 s. The maximum deviation distance tracked by the Dynamic Window Algorithm was only 3.3 m, which was less than the expected maximum deviation distance of 5 m. The proposed method can: 1) Avoid the impact of artificial judgment of resource depth on the fishing volume effectively, and improve the fishing efficiency. 2) Realize the automatic planning of the truss forward route with the best fishing efficiency.
Variation in fish community structure before and after La Niña event in Beibu Gulf
LI Miao, XU Youwei, SUN Mingshuai, FAN Jiangtao, LI Jiajun, ZHANG Kui, CHEN Zuozhi
 doi: 10.12131/20220144
To understand the potential impact of La Niña events on fish community structure in Beibu Gulf, based on the bottom trawl survey data of fishery resources in July 2006 and July 2008, we analyzed the variation in the fish community structure before and after La Niña event in the Beibu Gulf. The results show that the dominant species were Acropoma japonicum and Trachurus japonicus in the summer of 2006, and T. japonicus, Decapterus maruadsi, A. japonicum and Evynnis cardinalis in the summer of 2008. T. japonicus and A. japonicum were the common dominant species in the two years. The diversity index (H') and evenness index (E1 and E2) did not differ significantly between years, but the richness index (D') differed significantly. After the La Niña event, the density of warm-water fish resources, such as A. japonicum, decreased, while that of warm-water fish resources, such as T. japonicus and D. maruadsi, increased. Besides, T. japonicus and D. maruadsi moved in the direction of the coast of the Beibu Gulf. The diversity index of the Beibu Gulf coastal sites (C1–C22) was significantly different before and after the La Niña event (P<0.05). The results of cluster analysis and non-metric multidimensional scale ranking show that the fish community spatial distribution was more stable, the main difference was in the western coast of Hainan Island. The La Niña event resulted in a decrease in water temperature and an increase in primary productivity in the Beibu Gulf, causing an increase of the density in small pelagic fish stocks such as T. japonicus and D. maruadsi. In conclusion, when the fishing pressure is relatively stable, the significant variation in the fish community structure in the Beibu Gulf is closely related to the La Niña event.
Spatial pattern characteristics of albacore tuna resources at different spatial scales in South Pacific
WANG Zhihua, YANG Xiaoming, TIAN Siquan
 doi: 10.12131/20220046
Albacore tuna (Thunnus alalunga) is the main target species of longline fishery, accounting for 1/3 of the annual catch of tuna. Since the fishery resources of T. alalunga are rich in South Pacific, to explore the spatial pattern characteristics of its fishery resources in that sea area, and to analyze whether there are differences in the spatial scale are important for the rational utilization and protection of its fishery resources in South Pacific. We aggregated the longline fishing logs of the Chinese mainland from 2015 to 2019 at three spatial scales (1°, 2° and 5°) by season, and calculated their spatial pattern characteristics based on the 5°grid data from Western and Central Pacific Fisheries Commission (WCPFC). The results show that: 1) The spatial pattern of T. alalunga resources in the South Pacific was characterized by large ellipticity, and there was a significant east-west distribution in the direction of the spatial pattern at all scales. The spatial pattern characteristics of resources (Distribution range, flatness, azimuth, etc.) had similar and obvious seasonal fluctuation characteristics. 2) The spatial pattern of resources obtained from three different scales of the same origin had a small difference, while that from different sources had a great difference. 3) In the same scale of 5°grid data, the resource center of the spatial pattern in China was more southeast and about 10°east in longitude than that of the data from the WCPFC. 4) The aggregation degree of resource spatial pattern obtained from large-scale data was stronger than that from small-scale aggregation data. Besides, the hot spots of spatial pattern obtained from different scale data of same origin were different to some extent.