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Cloning and transcriptional regulation of slitrk3 gene promoter in large yellow croaker (Larimichthys crocea)
ZHOU Ruitao, YUE Zhufeng, JI Jiaojun, WEN Jing, JIANG Dan, WANG Zhiyong, FANG Ming
 doi: 10.12131/20220309
[Abstract](66) [FullText HTML](17) [PDF 1000KB](1)
Slitrk3, a neurosynaptic-related protein, can regulate the development of inhibitory synapses. To explore the transcriptional regulation mechanism of slitrk3 gene of the large yellow croaker (Larimichthys crocea) can provide a new idea for solving the problems of growth, stress and anti-stress in the L. crocea culture. We conducted a multiple sequence alignment and a phylogenetic tree analysis of amino acids for Slitrk3 in L. crocea and other species to investigate the transcriptional regulation mechanism of the neural cell adhesion molecule for slitrk3 gene. Besides, we predicted the potential core promoter regions, CpG islands and transcription factor binding sites of slitrk3 gene by bioinformatics methods, and detected the Luciferase activity of promoter of slitrk3 gene by the Dual-Luciferase Reporter System. Bioinformatics analysis shows that the amino acid sequences of Slitrk3 were highly conserved in fish. There were two transcription start sites, two CpG islands, and multiple transcription factor binding sites such as Sp1, GR, C/EBPα and C/EBPβ in promoter of slitrk3 gene. Dual-Luciferase Reporter System shows that the regions from −1970 to −1614 bp and from −1 210 to −667 bp contained positive regulatory elements; while the regions from −1614 to −1210 bp, from −667 to −376 bp and from −376 to −147 contained negative regulatory elements; and the regions from −147 to +16 bp might be core promoter of slitrk3 gene. The results lay a theoretical foundation for the further study of transcriptional regulation mechanism of slitrk3 gene in L. crocea.
Spatial-temporal changes in western and central Pacific warm pool and their impact on distribution of Katsuwonus pelamis
LIN Hongyu, WANG Jintao, CHEN Xinjun, JIANG Mingfeng, XU Zi'an, LEI Lin, LYU Zehua
 doi: 10.12131/20220235
[Abstract](145) [FullText HTML](69) [PDF 2050KB](30)
The western and central Pacific tropical waters are largest fishing ground for the skipjack tuna (Katsuwonus pelamis) in the world. To rationalize the development and utilization of the fishery resources of K. pelamis free-swimming school fishery in the Western and Central Pacific Ocean, we derived the gravity center by calculating the resource abundance index based on the data of for skipjack tuna from 1995 to 2019 from the Western and Central Pacific Fisheries Commission. Besides, we conducted a Pearson correlation analysis by combining sea surface temperature (SST) and Oceanic Niño Index (ONI). The results show that the catch per unit effort (CPUE), which can be used to characterize the resource abundance of the gravity center of free swimming school of skipjack, was significantly correlated with the longitude of the gravity center of the warm pool and the longitude of the right edge. The relative positions and trends of the CPUE and warm pool indicators (Longitude of the gravity center of the warm pool and longitude of the right edge) were different under different climate modes but were the same under the same climate mode. The results show that the changes in the gravity center of the fishing grounds can be predicted by the warm pool's changes in the gravity center. By constructing the spatial-temporal distribution relationship between the warm pool field and the resource abundance, we found that the right edge of the warm pool could be associated with the spatial distribution of the free swimming school of skipjack, which provides an indication of the fishing ground boundary of free-swimming school stock in commercial fishing purse-seine skipjack tuna, and provides a scientific basis for its resource exploitation and conservation.
Evaluation of gel properties of heat-induced surimi of Ictalurus punctatus from four genealogies
WANG Xin, LI Mengzhe, ZHANG Wei, KONG Yunfei, XIONG Zhiyu, SHI Tong, BAO Yulong, YUAN Li, ZHANG Shiyong, WANG Minghua, CHEN Xiaohui, GAO Ruichang
 doi: 10.12131/20220198
[Abstract](136) [FullText HTML](39) [PDF 1688KB](6)
Ictalurus punctatus has less fishbones and more meat, very suitable for being processed into surimi products. In order to evaluate the processing characteristics of surimi of I. punctatus from different genealogies, we selected the dorsal muscle of the four genealogies of "Jiangfeng No.1" I. punctatus (DZ1-1, KB4-1, K2-1, 46-1) which were prepared into surimi after rinsing, chopping, dewatering and refined filtration, and heated them at two stages to make heat-induced surimi gels. By measuring the thermal stability of surimi protein, physical and chemical properties of the surimi gels, such as whiteness, texture, water holding capacity and gel strength, we analyzed the heat-induced gels of I. punctatus from different genealogies. The results show that compared with the other genealogies, the surimi myofibrillar protein of DZ1-1 genealogy had higher thermal stability, and the relative content of β-folding and β-turning structure was higher, which affected the gel quality of heat-induced surimi. There are no significant differences in the whiteness of heat induced surimi gels prepared by different genealogies of I. punctatus, with water holding capacity over 80%. The gel strength of the DZ1-1 genealogy was 2.7×102 g∙cm, which was better than other genealogies, while the hardness, springiness and gumminess of the DZ1-1 genealogy were not different from the KB4-1 genealogy, but significantly better than the other two genealogies. In conclusion, the DZ1-1 genealogy is more suitable for surimi processing.
Analysis on differences of microbial community structure and main flavor substances of Cyprinus carpio var. Jinbei cultured in paddy fields and ponds
YU Meijuan, YANG Hui, YU Changsheng, CAI Jiaoming, BU Zilong, ZENG Xianwen
 doi: 10.12131/20220270
[Abstract](104) [FullText HTML](20) [PDF 1406KB](11)
It is important to study the differences of intestinal flora and fish flavor quality of Cyprinus carpio var. Jinbei under different culture modes for its breeding optimization. We applied illumina high-throughput sequencing technology to analyze intestinal microflora of C. carpio var. Jinbei cultured in paddy fields (FGF) and ponds (FGP), respectively. Besides, we used liquid chromatography (LC) to determine the flavor substances, and used headspace solid phase microextraction combining with gas chromatography-ion mobility spectrometry (HS-SPME-GC-IMS) to determine the volatile flavor substances. Then we calculated the taste activity value and relative odor activity by combining the sensory threshold. Significant difference analysis shows that Vibrio, Bacteroides, Alteromonadales, Shewanella, Pseudomonas psychrophila and Brevinema were the main bacteria in FGF group, while Moraxella and Klebsiella were the main bacteria in FGP group. The contents of IMP and flavor activity in FGF group (1.676 g·kg−1 and 6.705) were significantly higher than those in FGP group (0.246 g·kg−1 and 0.985). The contents of umami amino acids and sweet amino acids in FGF group (0.143 and 2.052 g·kg−1) were higher than those in FGP group (0.109 and 2.001 g·kg−1). However, the contents of bitter amino acids in FGF group (3.193 g·kg−1) were lower than those in FGP group (3.836 g·kg−1). Moreover, the components of volatile compounds were complex, and the types of key odor compounds (ROAV≥1) and compounds that could modify the overall flavor (0.1≤ROAV<1) were different. The correlation analysis between bacteria genera and flavor substances shows that Vibrio, Bacteroides, Klebsiella and Morganella were significantly correlated with flavor substances (0.01≤P<0.05 & 0.001≤P<0.01 & P<0.001). The results indicate that cultivation mode affects the intestinal microbes of fish, and affects the flavor quality of fish indirectly.
Effects of cold stress-induced dormancy methods on life characteristics and nutritional quality indexes of Patinopecten yessoensis during anhydrous living-preservation
CHANG Xiangyang, JIANG Peihong, DENG Jie, FAN Xiuping, QIN Xiaoming
 doi: 10.12131/20220304
[Abstract](102) [FullText HTML](60) [PDF 2827KB](17)
Exploring the best method to induce the dormancy of scallops (Patinopecten yessoensis) before live transport can provide a theoretical basis for their survival and circulation. Referring to the actual industrial circulation, we treated the samples by three methods of natural cooling of crush ice, acute continuous cooling and gradient cooling, so as to explore the effects of different cooling and dormancy methods on the survival rate, life characteristics and nutritional quality of scallops during anhydrous living-preservation. The results show that the survival rate of the gradient cooling group was 93.33% after 3 d of keeping alive at 4 ℃, significantly higher than that of the acute and natural cooling groups. In the process of cooling dormancy, regular electrocardiogram could not be detected in the natural and acute cooling groups due to the sudden temperature change, and the heart rate in the gradient cooling group showed a regular slow decline. During the live transport, the heart rate in each group showed a decreasing trend. After 3 d of keeping alive, the irregular heart rate in the natural ice cooling group was no longer observed, while the irregular heart rate in the gradient and acute cooling groups was still observed. The edge mantle retraction ratio and the response time of all three cooling groups tended to increase gradually (Those of natural and acute cooling groups were significantly higher than those of gradient cooling groups), and the heart rate was negatively correlated with the response time of the mantle. The contents of water, crude protein, crude fat and muscle glycogen all showed a decreasing trend, and the consumption of glycogen was the largest. Less loss of nutrients before live transport was observed in the gradient cooling groups compared with the other groups. The microstructure also shows that the closed shell muscles in the gradient cooling group were closely arranged without an obvious fracture. This study indicates that inducing P. yessoensis to enter dormancy or semi-dormancy state by gradient cooling and then keeping them alive without water, is beneficial to improving the survival rate of living P. yessoensis, reducing the loss of nutrients during the live transport, and maintaining the vitality of living P. yessoensis, so it is more conducive to its anhydrous living-preservation.
Enzymatic extraction and physicochemical properties of Porphyra haitanensis protein
LENG Meng, LIN Duanquan, WENG Ling, ZHANG Lingjing, MIAO Song, CAO Minjie, SUN Lechang
 doi: 10.12131/20220242
[Abstract](189) [FullText HTML](78) [PDF 4668KB](17)
Abalone viscera is rich in hydrolytic enzymes that can decompose algal polysaccharides. In order to realize the highly efficient extraction and industrial production of Porphyra haitanensis protein, we used abalone visceral enzymes to break the cell wall of P. haitanensis to extract porphyra protein, and compared the physicochemical properties in proteins prepared by freeze drying and air drying. The results show that the optimal enzymatic conditions were obtained as follows: enzyme dosage of 7.6%, enzymatic hydrolysis time of 2.8 h, enzymatic hydrolysis temperature of 35 ℃, and material-to-liquid ratio of 1:25. The protein yield under above conditions was (238.65±2.13) mg∙g−1. The results of appearance morphology and cell morphology of Porphyra haitanensis indicate that abalone viscera enzymatic digestion could break down the cell wall of P. haitanensis significantly. Freeze-dried P. haitanensis protein (FPP) showed better solubility and emulsification properties than spray-dried P. haitanensis protein (SPP) at different pHs (P<0.01), while the surface hydrophobicity and contact angle of SPP were higher than those of FPP (P<0.01). Scanning electron microscopy shows that FPP had a smooth lamellar surface, while SPP had a more uniform spherical particle size with grooves on the surface. In conclusion, the abalone viscera enzyme was effective in breaking down the cell wall of P. haitanensis and leaching out the water-soluble proteins. All the prepared proteins had good physicochemical properties, while the freeze-dried proteins are better than air-dried proteins.
Extraction process of intestinal lipid droplets and lipid droplet-related proteins from tilapia
LI Jie, HUANG Hui, XIANG Huan, CEN Jianwei, WEI Ya, ZHAO Yongqiang, HAO Shuxian, LI Laihao
 doi: 10.12131/20220285
[Abstract](148) [FullText HTML](67) [PDF 1979KB](16)
Lipids in animals and plants exist in the form of lipid droplet (LD). It is very important to master the purification methods of lipid droplet and lipid droplet related protein (LDRP) for understanding the lipid changes and influence mechanisms of fish, and seeking appropriate regulatory approaches. In this paper, the lipid droplet and LDRP were separated and purified through centrifugation, resuspension and solubilization by using Oreochromis niloticus intestinal tissues as raw material. The results show that the intestinal adipose tissues were effectively removed by three times of centrifugation and three times of resuspension to obtain the pure lipid droplet. Although the concentration of LDRP protein extracted by solubilization was higher, the electrophoretic bands showed an obvious trailing phenomenon, indicating that the effect of lipid removal was poor, which affected the purity of LDRP extraction. Delipidation and solubilization need to be combined with four groups of organic solvents to obtain the LDRP extracted samples with high purity and good re-solubilization effects. The effects of centrifugation drying method and lipid droplet freezing on LDRP solubilization were not significantly different.
Effect of alginate oligosaccharides combined with low magnetic field freezing on structure and properties of myofibrillar protein of silver carp
CONG Haihua, LU Xiaoyan, ZHOU Qian, ZHANG Ziwei, ZHENG Zhihong, LIU Li, SONG Guanliang, LEI Huiwen, CHEN Jiwei
 doi: 10.12131/20220245
[Abstract](99) [FullText HTML](50) [PDF 895KB](11)
In order to obtain good preservation quality in the processing of aquatic pre-made products with silver carp (Hypophthalmichthys molitrix) as raw material, we designed a new freezing method. We investigated the structural and functional changes of myofibrillar protein (MP) by freezing alginate oligosaccharides (AO) at a mass fraction of 0.6% with a low magnetic field (LMF) of 2 mT, and used no treatment at −20 ℃ as the blank group. On this basis, we added AO and AO+LMF as the experimental group, added AO as the common freezing (CF) group at −30 ℃, and had frozen the MP for 28 d. By measuring the solubility, turbidity, surface hydrophobicity, sulfhydryl content, thermal stability, Fourier transform infrared spectroscopy and endogenous fluorescence spectroscopy, we comprehensively compared the structure and properties of frozen MP. The results show that there were no significant differences in the turbidity among the three freezing methods at −20 ℃. The protein solubility of CF group was 94.11%. After AO+LMF treatment, the exposure of hydrophobic groups reduced, with a higher total sulfhydryl content of 15 mmol·kg−1, and the exposure of tryptophan residues reduced, which protected its protein tertiary structure effectively. Fourier transform infrared spectroscopy shows that after AO modification and freezing, MP denaturation was the lowest, α-helix content was higher, and secondary structure was more stable. It it showed that 0.6% fucoidan with low magnetic field freezing treatment can better maintain the stability of MP in silver carp, which lays the foundation for the application of AO in frozen aquatic products and provides references for the further research on the low magnetic field freezing.
Preparation, separation and physicochemical properties of α-glucosidase inhibitory peptides from Miichthys miiuy
HUO Yumei, HU Xiao, WU Yanyan, JIANG Jinjin
 doi: 10.12131/20220269
[Abstract](115) [FullText HTML](19) [PDF 1454KB](4)
In order to achieve the high-value utilization of processing by-products of Miichthys miiuy, taking α-glucosidase inhibition rate as an index, we carried out a single factor experiment and applied the response surface methodology to optimize the preparation process of α-glucosidase inhibitory peptides from minced fish muscle of M. miiuy processing by-products. The optimal enzymatic hydrolysis conditions with trypsin were as follows: hydrolysis time 4.8 h, enzyme dosage 0.21%, hydrolysis pH 8.5, material-liquid ratio 1∶2 (m/V), hydrolysis temperature 46 ℃. On this basis, we analyzed the inhibitory activity of the enzymatic hydrolysates before and after the simulated gastrointestinal digestion in vitro, and drew the kinetic curve of enzyme inhibition. Then we separated the enzymatic hydrolysate by SephadexG-25 so as to investigate the molecular weight distribution and amino acid composition of the enzymatic hydrolysates. The results show that the α-glucosidase inhibitory rate increased to 61.79% after that the α-glucosidase inhibitory peptide was simulated gastrointestinal digestion in vitro. Its inhibition type on α-glucosidase was mixed type inhibition. The molecular mass of the enzymatic hydrolysate was concentrated below 3 kD, accounting for 91.85%. After the separation by G-25, the α-glucosidase inhibition rate of F4 fraction was 58.05%. In Group F4, 78.28% of peptides were less than 1 kD. The amino acid analysis shows that the enzymatic hydrolysate was rich in Asp, Glu, Arg, Tyr, Val, Ala, Leu and Lys.
Comparative transcriptome analysis in livers of female and male marine medaka (Oryzias melastigma)
ZHANG Linbao, TIAN Fei, CHEN Haigang, ZHANG Zhe, YE Guoling, LI Yitong, TANG Haiwei
 doi: 10.12131/20220250
[Abstract](155) [FullText HTML](37) [PDF 913KB](13)
As a gonochoristic model animal, marine medaka (Oryzias melastigma) is good for studying the sex-specific responses of organisms to xenobiotic pollutants. We used comparative transcriptomics technology to systematically investigate the differentially expressed genes (DEGs) between the liver tissues of female and male medaka. We identified 683 significantly up-regulated DEGs in the females, and 668 DEGs in the males. The high expressed DEGs in the females were involved in the reproductive and sex hormone synthesis pathways, such as vitellogenin and estrogen receptor. The top twenty DEGs in the males were involved in energy metabolism, cytoskeleton and muscle contraction, such as pyruvate kinase, creatine kinase, myosin and troponin. Except for the DNA mismatch repair protein, all the 17 DEGs had similar magnitude and expression trends by both qRT-PCR and RNA-seq analyses, which confirms the reliability of the RNA-seq data. The results demonstrate that the gene expression patterns are different in the livers of female and male medaka, and the DEGs provide a theoretical basis for promoting the molecular mechanism of sex-specific responses of medaka to xenobiotic pollutants.
Screening of antagonistic bacteria against visceral white-spots disease of Larimichthys crocea and preliminary study on its biological characteristics
LI Zhangchan, SHI Hui, XU Wenjun, HE Jie, XIE Jianjun, WANG Gengshen, WANG Wei
 doi: 10.12131/20220251
[Abstract](158) [FullText HTML](35) [PDF 1402KB](15)
In order to achieve the biological prevention and control of visceral white-spots disease of Larimichthys crocea, and promote the reduction of drug use in aquaculture, we isolated and screened the probiotics with an antagonistic effect on Pseudomonas plecoglossicid, which is a pathogen of visceral white spot disease in L. crocea, from the intestine of healthy L. crocea. The strains were screened by agar diffusion method, identified by physiological and biochemical characteristics and molecular biology analysis, and evaluated for hemolysis, drug sensitivity, safety, enzyme production ability and broad-spectrum antibacterial activity. Thirty-seven strains of potential probiotics were isolated and the three most potent strains were further characterized for their probiotic potential, named as P1-17, P2-33 and P3-11. The three most promising isolates were identified by sequencing the 16S rRNA gene and physiological and biochemical characteristics. Strains P1-17 and P2-33 were identified as Bacillus velezensis and P3-11 was identified as Enterococcus faecalis. According to the hemolytic test and disk diffusion method, none of the three strains had sigificant hemolytic rings, containing few drug resistance factors, so they had no potential pathogenicity. The result from the artificial infection safety test confirmed that these three strains of antagonistic bacteria had no pathogenicity to healthy L. crocea. The results of the antimicrobial spectrum show that two strains of Bacillus had an antagonistic effect on common aquatic pathogens such as Vibrio alginolyticus, V. harveyi and Photobacterium damselae. Moreover, two strains of Bacillus could produce amylase and protease, while the strain of E. faecalis only had an antagonistic effect on P. plecoglossicida. The study provides a scientific basis for the subsequent screening and application of intestinal probiotics in L. crocea.
Effect of density on antioxidant and nonspecific immunity of mud crab (Scylla paramamosain)
TIAN Yu, JIE Yukun, ZENG Xiangbing, YUE Yan, LIU Guangxin, CHENG Changhong, MA Hongling, GUO Zhixun
 doi: 10.12131/20220312
[Abstract](136) [FullText HTML](41) [PDF 823KB](5)
Density stress has a negative impact on the immune and antioxidant functions of aquatic animals. In order to improve the potential production of mud crab (Scylla paramamosain) and provide a theoretical basis for its aquaculture development, we cultured the mud crabs for 72 h at three different densities: 8 ind·m−2 (Low density group), 16 ind·m−2 (Medium density group), and 32 ind·m−2 (High density group) to study the effects of density on the antioxidant and immune capacity of mud crabs. The results of antioxidant enzyme activity show that the activities of catalase (CAT) and superoxide dismutase (SOD) in the high density group were significantly higher than those in the low density and medium density groups (P<0.05), but there was no significant difference in the glutathione peroxidase (GSH-Px) activity among the groups. Additionally, the malondialdehyde (MDA) content in the high density group was significantly higher than that in the low density and medium density groups. The activities of acid phosphatase (ACP), alkaline phosphatase (AKP) and lysozyme (LZM) in the high density group were significantly lower than those in the low density and medium density groups (P<0.05), but there was no significant difference between the medium density group and the low density group. The real-time PCR results indicate that the heat shock protein 70 (HSP70) expression level in the high density group decreased first and then increased, significantly lower than that in low density and medium density groups from 6th hour to 48th hour (P<0.05). The expression level of Caspase 3 in the high density group increased significantly after 6 h and decreased gradually after reaching the maximum level at 24th hour, but was always significantly higher than that in the low density group (P<0.05). In conclusion, high density culture can cause oxidative damage, leading to the decline of immunity of mud crabs. The stock density of 16 ind·m−2 has no significant effects on the antioxidant and immune abilities of mud crabs.
Effect of low temperature stress on antioxidant stress, apoptosis and histological structure of gills in cobia (Rachycentron canadum)
LI Yu, HUANG Jiansheng, CHEN Youming, WEN Zhenwei, OU Guanghai, HUANG Jianpeng, JIANG Xintao, XIE Ruitao, MA Qian, CHEN Gang
 doi: 10.12131/20220227
[Abstract](164) [FullText HTML](54) [PDF 3009KB](14)
The gill tissue of cobia (Rachycentron canadum) is sensitive to water temperature changes. In order to investigate the effect of low temperature stress on juvenile cobia, and reveal its response mechanism to low temperature stress, we designed two low temperature groups (18 ℃ and 21 ℃) and one control group (28 ℃), to analyze the antioxidant responses, expression of apoptosis-related genes and histological structure of the gills on 0, 4th and 7th day after the stress. The results show that the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in the low-temperature groups were significantly lower than those in the control group (P<0.05), while the malondialdehyde (MDA) mass concentration in the low-temperature groups was significantly higher than that in the control group (P<0.05). The expression of apoptosis-related genes bax, caspase-9, caspase-3, p53 and mdm2 increased significantly in the low-temperature groups, while the expression of Bcl-2 decreased significantly on 4th and 7th day (P<0.05). The TUNEL results reveal that low-temperature treatment increased the cell apoptosis rate of the gills, and caused lesions including fusion of secondary lamellae, necrosis of epithelial cell and hyperplasia of chloride cells. The results indicate that low-temperature stress causes oxidative stress, induces apoptosis and damages the structural integrity of the gills, which suggests that normal physiological functions of juvenile cobia can be affected by low temperature significantly.
Study on large-scale artificial seedling breeding technology of Tapes dorsatus
ZHANG Kexin, LUO Zexin, ZHANG Yuan, ZHAN Jianqiang, LU Yining, LIU Zhigang
 doi: 10.12131/20220262
[Abstract](129) [FullText HTML](43) [PDF 789KB](8)
Based on the problem of seedling supply of Tapes dorsatus, we studied the key techniques of seedling breeding of T. dorsatus by a single factor comparison test, so as to provide references for its large-scale artificial breeding. The results show that: 1) With artificial temperature control, we used the compound algae in shrimp pond to promote the ripening of the parents instead of the pure monocytic algae, and the ripening rate was 282.6% higher than that of the control group. 2) By means of a series of measures such as warming and drying in shade to induce spawning, the rate of induced spawning increased by 50.9% compared with the control group. 3) In order to establish a closed seedling technology model, we added effective microorganisms to build a beneficial micro-ecosystem, and did not change the water during the seedling breeding period. The results reveal that the survival rate of larvae in pelagic period, juvenile growth rate and juvenile rearing rate were significantly higher than those of the control group. 4) We collected the spats by using vertival seedling collection combined with the bottom of the pool. The juvenile rearing rate and yield per unit area increased by 76.6% and 76.5%, respectively. 5) Taking the parents with body mass above 5% as breeding group, the shell length, body mass of juvenile and juvenile rearing rate increased by 6.6%, 17.03% and 8.43%, respectively compared with the control group. However, the variable coefficients of juvenile shell length and body mass decreased by 29.13% and 55.29%, respectively. The realized heritability "h2" of shell length and body mass at the juvenile stage reached 0.65 and 0.72, respectively. This study designed a new integrated innovative technology for the artificial seedling breeding of T. dorsatus, which achieves significant economic benefits and lays a foundation for the realization of its large-scale breeding of seedlings.
Structural characteristics and relative influencing factors of macrobenthos community in intertidal zone of Daya Bay
LI Xue, LI Yafang, CHEN Qinghua, NING Jiajia, WANG Lianggen, XU Lei, HUANG Delian, LIU Shuangshuang, ZHONG Chao, ZHANG Jian, WANG Xuehui, DU Feiyan
 doi: 10.12131/20220202
[Abstract](127) [FullText HTML](69) [PDF 884KB](17)
In recent years, the structure of macrobenthic community and ecological functions of intertidal zone in Daya Bay have changed significantly due to the influence of various factors such as anthropogenic disturbances. In order to understand the changing patterns of ecosystem functioning in the coastal waters of Daya Bay, we obtained the data on the macrobenthos and habitats in six intertidal sections (Three sands, two muds and one artificial shoreline) in summer (August) and autumn (November) of 2021, and analyzed their community structure characteristics and influencing factors. The results show that a total of 118 species were identified, including 82 species in summer and 64 species in autumn, among which molluscs had the largest quantity in both seasons followed by arthropods and annelids. The mean biomasses of the six sampling sections in two seasons were 589.36 and 188.22 g·m−2, and the mean abundances were 356.39 and 1 010.3 ind·m−2, respectively, with molluscs and arthropods accounting for a higher proportion. The results of cluster analysis and multidimensional scaling show that the macrobenthic fauna community in the survey areas displayed significant spatial differences. The macrobenthos in the intertidal zone of Daya Bay could be divided into three communities: sand facies, mud facies and artificial shoreline, among which the artificial shoreline community had the highest diversity index and best community stability. Distance-based redundancy analysis indicates that the structure of intertidal macrobenthic community was mainly affected by sediment type and anthropogenic disturbance.
Study on bacterial community structure in rearing water in small greenhouse of Litopenaeus vannamei
FANG Yuan, LI Hui, WANG Libao, WAN Xihe, SHI Wenjun, YANG Zeyu, JIANG Qi, SHEN Hui, HU Runhao, GUAN Xiaoping, YANG Jiaxin
 doi: 10.12131/20220205
[Abstract](204) [FullText HTML](85) [PDF 1748KB](42)
In recent years, small greenhouse has been a hot model of Litopenaeus vannamei culture. In order to elucidate the structure and changes of the microbial community in the rearing water of L. vannamei culture in small greenhouse and explore the reasons for high yield and high efficiency of this model, we analyzed the composition and function of the microbial community on 2nd, 44th, 69th and 96th day of water in the small greenhouse based on 16S rRNA sequencing results. The results show that the richness and diversity of water microbial community at late stage of small greenhouse were significantly higher than those at early stage. During the whole culture process, the dominant bacteria at the phylum level were Proteobacteria, Bacteroidetes and Actinobacteria, among which the abundance of Proteobacteria increased significantly on 69th day, and the abundance of Actinobacteria increased at early stage but decreased at later stage. At genus level, the abundance of Candidatus_Aquiluna was the highest on 2nd day (28.7%). Marivita was enriched at middle stage, with the highest abundance on 69th day (9.94%). The abundance of Flavobacterium gradually increased with the culture time, reaching the highest on 96th day (11.63%). PICRUSt2 predicts the function of the microbial communities, and the abundances of metabolic function in the top 20 were significantly higher on 69th and 96th day than on 2nd day. In particular, the functions of terpenoids and polyketides metabolism, lipid metabolism, xenobiotics biodegradation and metabolism were highly enriched. Through FAPROTAX identifying, the abundance of chemoheterotrophy increased significantly at the late stage. The correlation analysis of environmental factors shows that total nitrogen (TN) and chemical oxygen demand (COD) had the greatest impacts on the microbial community structure in greenhouse model. Microorganisms such as Marivita, Candidatus_Aquiluna and Rhodopirellula played the roles in sequestration of carbon and reduction of nitrogen and phosphorus. In conclusion, under the high density and high nitrogen and phosphorus culture conditions, the water microbial community in the small greenhouse played an important role in maintaining the stability of water environment and enhancing the immunity and disease resistance of prawns.
Purification effect of searice paddy field on brackish water environment of shrimp culture
ZHANG Xinxin, LI Ting, LI Shaowen, ZHU Changbo, ZHANG Bo, SU Jiaqi, RUAN Guoliang, ZHANG Xiaoyang
 doi: 10.12131/20220261
[Abstract](199) [FullText HTML](29) [PDF 844KB](18)
In order to explore the water purification effect of paddy field in the combined pond-paddy field farming system, we analyzed the biofiltration ability of sea rice paddy field in two shrimp culture seasons (Summer and winter). In the summer trial, the tail water of shrimp culture was purified by sea rice and common rice paddy fields with different planting densities, and the purification efficiency of sea rice paddy fields with standard planting density was the highest. After six weeks, the removal rates of ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, total phosphorus and chemical oxygen demand in standard sea rice treatment were 81.6%, 68.2%, 63.7%, 91.0% and 29.7%, respectively, which were significantly higher than those in the control treatment (P<0.05), and the removal rates of ammonia nitrogen and total inorganic nitrogen were significantly higher than those in the common rice treatment (P<0.05). In the winter trial, sea rice was harvested in the shrimp-rice pond, the average concentrations of ammonia nitrogen, nitrite nitrogen, total inorganic nitrogen and total particulate matter in the shrimp-rice ponds decreased by 51.5%, 40%, 36.7% and 11.2%, respectively, compared with the shrimp monoculture ponds (P<0.05). The average concentrations of nitrate nitrogen, total phosphorus and chemical oxygen demand, particulate organic matter and particulate inorganic matter were not significantly different from those in monoculture ponds (P>0.05). The results show that the sea rice paddy field has certain purification ability in both rice growing season and non-growing season, which helps to maintain a good water environment for shrimp growth.
Spatial heterogeneity of relationship between distribution of Uroteuthis chinensis and marine environment in offshore waters of northern South China Sea
CAI Yancong, SUN Mingshuai, XU Youwei, CHEN Zuozhi
 doi: 10.12131/20220288
[Abstract](123) [FullText HTML](55) [PDF 6329KB](10)
Cephalopods are one of the most potienial fishery species but are vulnerable to environment changes, and their complex interactions lead to the spatial heterogeneity in resource-environment relationship. Uroteuthis chinensis is an important economic species in the offshore waters of northern South China Sea, occuping a dominant position in the fishery community structure. Therefore, understanding the spatial characteristics of the resource-environment relationship is beneficial to its development, utilization and protection. Based on the fishery resources survey data in the offshore waters of northern South China Sea in summer of 2014, we established a geographically weighted regression (GWR) model to explore the spatial characteristics of the relationship between the resource distribution of U. chinensis and the marine environment in this area, and to reveal the main influencing factors. The results of model evaluation indexes show that the minimum Akaike information criterion (AIC) and adjusted R-Square (\begin{document}$R_{\rm{adj}}^2 $\end{document}) for GWR model were 224.81 and 0.46, respectively, both of which were better than those of the traditional global linear regression model. Thus, the GWR model could more truly reflect the spatial heterogeneity on resource-environment relationship for U. chinensis. The impact of chlorophyll a on resources was a coexistence of positive and negative effects in the whole sea, but the other environment variables had consistent positive effects on resources. The stock distribution in the coastal waters of Guangdong was mainly affected by sea surface salinity, sea surface temperature and chlorophyll a, and the latter two were the primary influencing factors in western Guangdong and Pearl River Estuary-Eastern Guangdong, respectively, but the Beibu Gulf was only significantly affected by water depth. Under the impact of dominant environmental factors, U. chinensis stock denstiy showed obvious regional differentiation characteristics, especially those in the Pearl River Estuary-Eastern Guangdong significantly different from the other areas. In conclusion, GWR model provides an effective means to explore and understand the local characteristics of cephalopod resource-environment relationship.
Fish habitat suitability analysis of Dongta spawning ground of Pearl River based on fisheries acoustic survey
WU Zhi, LI Yuefei, ZHU Shuli, YANG Jiping, XIA Yuguo, LI Jie
 doi: 10.12131/20220283
[Abstract](106) [FullText HTML](32) [PDF 1260KB](13)
As the largest spawning ground, the Dongta spawning ground is an important habitat for many rare and unique fish in the Pearl River, playing an important role in maintaining the supplement and diversity of early fish resources in the middle and lower reaches of the Pearl River. In order to evaluate the fish habitat suitability, we selected the suitable habitat of fish by a hot spot analysis based on the acoustic data from 2016 to 2019. Taking the terrain factors (Water depth, slope and aspect) as habitat indicators to calculate the fitness index range of each factor, we established the habitat suitability index (HSI) model by using the geometric mean method and calculated the HSI value. It is showed that the fish density ranged from 0.009 to 0.057 ind·m−3 in Dongta spawning ground. In terms of time, the fish density had been decreasing year by year, but in terms of space, the overall autocorrelation of fish distribution was not strong, while the local autocorrelation was strong in some areas. For example, the area adjacent to the spawning ground sandbar had been a hot spot in three years, and the "cold spot area" appeared in the downstream of the Datengxia Water Project and Shizui Section. The most suitable water depth range was 5–8 m, the suitable slope range was 1.0°–1.5° (Micro-slope), and the suitable aspect range was 90°–180° (Southeast direction). The average HSI value was 0.31±0.22, ranging from 0.02 to 0.95, and the high value was obtained mainly on both sides of the sandbar of the Dongta spawning ground but scattered on both sides of the river, where might be potentially suitable habitat areas. The main channel was basically the area with low HSI values. The HSI model was verified based on the acoustic data in 2017, and the fish density and HSI showed a linear positive correlation, which indicates that the established model in this paper can be used to analyze and evaluate the habitat suitability of river fish.
Immune protective efficacy of recombinant vaccine against Aeromonas hydrophila secreted proteins on zebrafish
LIN Xiaoke, WANG Yuqian, LIN Meizhen, HUANG Dongping, MIAO Yuxuan, LIN Xiangmin
 doi: 10.12131/20220266
[Abstract](88) [FullText HTML](18) [PDF 949KB](9)
Aeromonas hydrophila is a prevalent aquatic pathogen that poses a risk to fishery production and can cause zoonotic diseases. Therefore, prevention of transmission and infection of A. hydrophila is a critical issue to address. To develop a potential subunit vaccine and provide a theoretical basis for better preventing and treating A. hydrophila disease, we selected eight secreted proteins (ORF0322, ORF3982, ORF2874, ORF1767, ORF3984, ORF2546, ORF0472 and ORF1609) from an A. hydrophila virulent strain LP-2 based on our previous research. The qPCR test shows that all selected proteins were expressed normally, then they were cloned and purified. The cloned and purified recombinant proteins were administered to zebrafish through injection. After 28 days of immunization, qPCR analysis detects increasing expression of all relevant immune genes in the zebrafish, suggesting that these recombinant proteins were capable of eliciting an immune response. In order to evaluate the immune protection offered by the eight selected secreted proteins, a bacterial challenge experiment was conducted. The results show that six of the secreted proteins (ORF3982, ORF2874, ORF1767, ORF3984, ORF0472, ORF1609) exhibited a relative immune protection rate (RPS) greater than 50%, indicating that they held promise as vaccine candidates against A. hydrophila infection.
Effects of cysteine addition to low-fishmeal diets on metabolism of lipid and protein in juvenile Trachinotus ovatus
LIU Jiaxing, GUO Huayang, ZHU Kecheng, LIU Baosuo, ZHANG Nan, XIAN Lin, ZHANG Dianchang
 doi: 10.12131/20230030
[Abstract](72) [FullText HTML](10) [PDF 1066KB](50)
To investigate the effect of cysteine on the metabolic disorders of juvenile Trachinotus ovatus (10.05 ± 0.05) g caused by low fishmeal, we prepared a basal pomfret diet by using plant and animal proteins (Chicken meal, soybean protein concentrate, fermented soybean meal, etc.) as partial substitutes for fishmeal, and then added 0 (Group C0, control group), 0.30% (Group C1), 0.60% (Group C2), 0.90% (Group C3) and 1.20% (Group C4) cysteine to make five isonitrogenous and isoenergetic diets. The results of a 56-day feeding trial show that: 1) Cysteine enhanced protein anabolism in T. ovatus by activating the S6K/PI3K/TOR/4E-BP1 pathway. Supplementation with 0.6%−0.9% cysteine up-regulated the mRNA levels of ribosomal protein S6 kinase (S6K), target of rapamycin (TOR), phosphoinositide 3-kinase (PI3K) and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) in muscle, increased total protein (TP) in muscle and serum as well as muscle crude protein content, reduced serum ammonia (SA) and urea nitrogen (UN) in muscle and liver, promoting protein deposition in muscle. 2) Supplementation with 0.6%−0.9% cysteine inhibited lipid anabolism by down-regulating the expression level of peroxisome proliferator-activated receptors gamma (PPARγ) in muscle, decreasing the transcript level and enzyme activity level of Acetyl-CoA carboxylase (ACC) and fatty acid synthetase (FAS), while it up-regulated the expression level of peroxisome proliferator activated receptors-alpha (PPARα) in muscle, resulting in high hormone-sensitive lipase (HSL) and carnitine palmitoyl transferase 1 (CPT1) expression with increased enzyme activity, which in turn promoted β-oxidation of fatty acids in muscle, reducing protein consumption due to catabolism for energy supply. Thus, protein deposition in muscle is promoted.
AHP-based evaluation on site selection for offshore cage culture
ZHANG Pingping, LI Zherui, SONG Huaiying, CAI Huiwen
 doi: 10.12131/20220253
[Abstract](69) [FullText HTML](28) [PDF 755KB](17)
The planning and selection of appropriate location of cage culture areas are essential for improving the economic benefits and promoting the sustainable development of cage culture industry. However, several factors affecting cage culture include marine environment, production management and facility safety, which makes it a complex and multifactor decision-making process. Thus, developing an index system to evaluate the impact on the location of deep-water cage culture is important. This paper employs the analytic hierarchy process (AHP) to construct an index system model for deep-water cage culture site selection. The model includes three criteria layers and fourteen index layers, and quantitatively analyzed the relative importance of each criterion layer and index layer based on expert judgment. Natural factors are the most important indicators affecting the location of deep-water cage culture in the criteria layer, followed by restrictive factors and finally social factors. Among the fourteen secondary indicators, water quality was the most significant, while feed supply had the least impact. The AHP-based evaluation index system for deep-water cage culture site selection can accurately assess the importance of various factors. This findings are beneficial for appropriately arranging deep-water cage culture area, selecting regions suitable for deep-water cage culture, and providing guidance for optimizing and revising marine functional zoning.
Cloning and expression analysis of PCNA in Metapenaeus affinis
ZHANG Yan, LUO Zhiping, LI Yundong, YANG Qibin, JIANG Song, CHEN Chuanghua, HUANG Jianhua, YANG Lishi, CHEN Xu, JIANG Shigui, ZHOU Falin
 doi: 10.12131/20220297
[Abstract](127) [FullText HTML](50) [PDF 3360KB](28)
As a coprotein of DNA polymerase δ, proliferating cell nuclear antigen (PCNA) plays an important role in the process of DNA replication. There is a stage of vigorous cell proliferation during the ovarian development in Metapenaeus affinis, but little attention has been paid to its molecular mechanism. In this study, we applied rapid amplification of cDNA ends (RACE) technique to obtain the full length cDNA sequences of PCNA in M. affinis (MaPCNA), and analyzed the expression of MaPCNA related to ovarian development by real-time fluorescent quantitative PCR (qRT-PCR). The total length of MaPCNA was 1 144 bp, including 140 bp of 5' untranslated region, 221 bp of 3' untranslated region and 783 bp ORF encoding 260 amino acids. The molecular mass of MaPCNA protein was 28.82 kD and the theoretical isoelectric point was 4.5. The protein homology analysis shows that MaPCNA had high homology with other crustaceans. The result of tissue expression shows that Ma-PCNA was expressed in all tested tissues, with the highest expression in ovary (P<0.05). The expression of MaPCNA in ovary at different developmental stages showed significant changes (P<0.05), increasing from stage I to stage III gradually, decreasing significantly and then tending to be stable. The expression of MaPCNA showed a regular change trend at different larval developmental stages. The expression level of MaPCNA was the highest in oosperm, then began to decline, and became stable from the Nauplius VI. The results suggest that PCNA may play an important role in the ovarian development of M. affinis.
Diagnostic and pathological studies of epizootic ulcerative syndrome (EUS) outbreak in cultured albino Channa argus in Sichuan Province of China
FAN Wei, CHEN Mengzhu, GUO Xianghui, GENG Yi, CHEN Defang, OUYANG Ping, HUANG Xiaoli, LAI Weimin, WU Jun
 doi: 10.12131/20220321
[Abstract](81) [FullText HTML](40) [PDF 5071KB](16)
In order to determine the causes of the frequent occurrence of diseases in albino northern snakehead (Channa argus) in Sichuan Province of China during the cloudy, rainy autumn and winter, we carried out the reseach by techniques such as clinical observation, isolation and culture, as well as histology and molecular biology, etc.. Generally, the pathological study shows that the main manifestations of the diseased fish were skin peeling, exposing the subcutaneous muscle layer, and the deep ulcer of the muscle. Moreover, non-septate branching fungal hyphae with a diameter of 10–20 µm were observed in squash preparations under light microscopy. The pathogen was identified as invasive Aphanomyces invadans by isolation and purification and ITS sequence analysis. Histopathology reveals that the ulcer edge in the skin dermis and muscle was surrounded by mature granuloma. These granulomas could invade the normal muscles observed by naked eye and caused a further impact on the diseased fish. The findings indicate that the disease was Epizootic Ulcerative Syndrome (EUS), which is the first report of EUS in albino C. argus, providing the basic data for the identification and clinical diagnosis of A. invadans. The findings also suggest that a risk of host expansion of this fungus may exist.
Study on muscle fiber characteristics, metabolic enzymes and gene expression of caudal stalk of golden-backed carp (Cyprinus carpio var. Jinbei)
ZHANG Wenzheng, YANG Li, YAO Junjie, MENG Qingmi, JI Da
 doi: 10.12131/20220320
[Abstract](129) [FullText HTML](52) [PDF 2174KB](9)
Golden-backed carp (Cyprinus carpio var. Jinbei) is a common carp that has lived in rice fields for many generations through long-term natural and artificial selection. In order to promote its paddy field breeding model and provide data supports for the breeding of improved varieties by this model, we analyzed the caudal stalk muscle fibers, related metabolic enzymes and gene expressions by using histology, enzymology and molecular biology methods, and explored the adaptive characteristics of caudal stalk muscle growth under the shallow ecological conditions of rice field. The results show that the diameter of caudal stalk muscle fiber in paddy field group was larger than that in pond group at flowering stage and harvest stage with significant differences (P<0.05). The cross-section area of caudal stalk muscle fiber in paddy field group was larger than that in pond group at flowering stage and harvest stage, with significant differences at harvest stage (P<0.05), while the density of caudal stalk muscle fiber in paddy field group was smaller than that in pond group. There were significant differences at harvest stage (P<0.05). The activities of lactate dehydrogenase (LDH), catalase (CAT) and Ca2+-ATPase in metabolic enzymes were higher in paddy field group than in pond group at flowering stage and harvest stage. The expression level of peroxisome proliferation-activated receptor γ-coactivator α (PGC-1α) gene in paddy field group was significantly higher than that in pond group (P<0.05). The results reveal that the expression levels of adenylate activated protein kinase (AMPK) and silence-regulating factor 1 (SIRT1) gene in paddy field group were significantly lower than those in pond group at flowering stage and harvest stage (P<0.05). The resistance movement of the caudal stalk of golden-backed carp in rice field caused muscle hypertrophy, which was related with the activation of protein synthesis pathway, while its endurance exercise, was related with the mitochondrial biosynthesis. The higher PGC-1α expression level of golden-backed carp in rice flowering stage may be related with the increase of rice flowering, insects, biodiversity and biomass.
Display Method:
2023, 19(2).  
[Abstract](55) [PDF 730KB](21)
Research Paper
Variation in fish community structure in Beibu Gulf before and after La Niña event
LI Miao, XU Youwei, SUN Mingshuai, FAN Jiangtao, LI Jiajun, ZHANG Kui, CHEN Zuozhi
2023, 19(2): 1-11.   doi: 10.12131/20220144
[Abstract](431) [FullText HTML](112) [PDF 6921KB](45)
La Niña events will affect the life history and diversity of fish, leading to the succession of fish community structure in different sea areas. To understand the potential impact of La Niña events on the fish community structure in the 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 in the Beibu Gulf before and after La Niña event. The results show that the dominant species were Acropoma japonicum and Trachurus japonicus in summer of 2006, and T. japonicus, Decapterus maruadsi and A. japonicum in 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 towards 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, and 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.
Intertidal macrozoobenthic community structure and its disturbed state in Zhanjiang Bay
LI Beixing, LI Aoxue, DONG Jianyu, LYU Shaoliang, WANG Xuefeng
2023, 19(2): 12-20.   doi: 10.12131/20220199
[Abstract](165) [FullText HTML](67) [PDF 2928KB](17)
Macrozobenthos are ideal indicators for monitoring and evaluating the ecological environment of intertidal zones. Zhanjiang Bay is the largest harbor in western Guangdong. In order to reveal the characteristics and disturbed state of macrobenthos communities in the intertidal zone of Zhanjiang Bay as well as to provide a scientific basis for their ecological protection, we investigated five intertidal zones (Donghai Island, Dongtoushan Island, Luzhu Village, Techeng Island and Zhanjiang Bay Bridge) exposed to different anthropogenic pressures in Zhanjiang Bay in August 2020 (Summer) and January 2021 (Winter). We analyzed the species composition, distribution of abundance and biomass, and biodiversities of macrozobenthos. Besides, we studied the disturbed state of macrozoobenthos communities by using the taxonomic diversity indexes and Abundance-biomass comparison (ABC) curves. The results show that: 1) A total of 98 species appeared in the five intertidal zones, among which Mollusca (45 species) were the most, followed by Arthropoda (26 species) and Annelida (19 species). 2) The average abundance and biomass of the macrozoobenthos were all greater in winter (187 ind·m−2, 188.38 g·m−2) than in summer (174 ind·m−2, 171.27 g·m−2). The mollusk Lucina scarlatoi and the arthropod Fistulobalanus albicostatus were the dominant species both in summer and winter. 3) Bray-Curtis similarity clustering analysis on the communities and non-metric multidimensional scaling (nMDS) suggest that the communities in the five intertidal zones in summer and winter could be spatially clustered into four groups. Among them, Luzhu Village and Zhanjiang Bay Bridge formed a subgroup, Dongtoushan Island and Techeng Island formed a subgroup, and Donghai Island formed a subgroup in summer and winter. 4) The taxonomic diversity index and ABC curves show some differences in evaluating the anthropogenic stresses on the intertidal macrozoobenthic community in Zhanjiang Bay. Furthermore, the taxonomic diversity index shows that Dongtoushan Island and Zhanjiang Bay Bridge were affected by tourism, and were more severely disturbed in winter, while the ABC curves show that Luzhu Village was affected by shellfish farming and was more severely disturbed in summer. The study reveals that human activities have had a negative impact on the macrozoobenthic communities in the intertidal zones of Zhanjiang Bay.
Fishing characteristics of light fishing vessels in open South China Sea based on Beidou position data
SUN Huiyan, ZHOU Yanbo, MA Shengwei, TIAN Ji, XU Jingchun, LIU Zhiying, BI Jieting, WU Qia'er
2023, 19(2): 21-30.   doi: 10.12131/20220254
[Abstract](163) [FullText HTML](75) [PDF 1805KB](11)
Light falling-net is one of the main fishing operations in the open South China Sea. In order to strengthen the monitoring of the production of light falling-nets in the open South China Sea and the effective management of fishing activities of fishing vessels, we had analyzed the positioning time, longitude and latitude and other characteristics based on the Beidou position data of the open South China Sea light fishing vessels from February to May 2017. Combined with the operation time, contour line, etc., we applied the multi-layer filtration method to determine the operation state of the fishing vessels. Then we filtered the fishing vessel operating locations and time by threshold, used the filter window correction method to correct the state of vessels, calculated the operation time of fishing vessels, and compared with the fishing logbook recorded by fishermen. The results show that the error between the extracted results by Beidou position data and the actual results recorded by fishmen was small. The voyage accuracy operation was 100%, and the accuracy of voyage days was 94.30%. The accuracy rate of the same fishing date was 92.72%. The total average absolute error of the operation time was 1.12 h, and the average relative error was 2.1% with good consistency. The methods of judging the state of the light fishing-net vessels, determining the operation location, extracting the operation time and calculating the fishing effort provide new ideas for the analysis of the light fishing-net vessel and the quantification of its fishing intensity.
Spatial pattern characteristics of albacore tuna resources at different spatial scales in South Pacific
WANG Zhihua, YANG Xiaoming, TIAN Siquan
2023, 19(2): 31-41.   doi: 10.12131/20220046
[Abstract](254) [FullText HTML](107) [PDF 4378KB](14)
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 great ellipticity, and there was a significant eastwest 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) For 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) Data aggregated at larger scales reflect stronger spatial aggregation characteristics of resources. Besides, the hot spots of spatial pattern obtained from different scale data of same origin were different to some extent.
Genetic structure and demographic history of Mastacembelus armatus in southern China
GAO Shang, LI Yuefei, LI Jie, CHEN Weitao
2023, 19(2): 42-49.   doi: 10.12131/20220200
[Abstract](292) [FullText HTML](87) [PDF 3299KB](34)
In order to understand the genetic resources of Mastacembelus armatus populations in southern China, and to provide an important scientific basis for their management and protection, 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.
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, MUYITI Minawaer, CHEN Hanfei, SUN Shiping, MA Yanwu, CHEN Peng
2023, 19(2): 50-61.   doi: 10.12131/20220192
[Abstract](170) [FullText HTML](67) [PDF 1134KB](13)
The regulation of bacterioplankton is the core content of the environmental control strategy in shrimp aquaculture. 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, we conducted 12 weekly surveys 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 temperature on survival and growth of Paphia textile juveniles
WU Jiaying, DAI Mingshu, LIU Zhigang, LIU Xiaokun
2023, 19(2): 62-69.   doi: 10.12131/20220155
[Abstract](331) [FullText HTML](109) [PDF 797KB](47)
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 differences 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 differences 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 ℃.
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
2023, 19(2): 70-77.   doi: 10.12131/20220176
[Abstract](233) [FullText HTML](63) [PDF 723KB](30)
Gill is an important respiratory organ of prawns, the main target organ of nitrite toxicity effect, and also one of the main enrichment sites of microplastics. The gill tissue participates in the physiological processes of prawns such as osmoregulation, nitrogen excretion, immune function, etc., which is important for maintaining the prawns' health. 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 at 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 at different degrees after the stress. 3) The relative gene expression levels of the osmoregulation indexes such as ion transporters (VATP, NHE7, NKA-α, NKA-β and CA) and channel proteins (TIP4, CCP, CLC and AQP) occurred at 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 immunity, detoxification metabolism and osmotic regulation in the gills of L. vannamei, affecting its normal physiological functions.
Response to UV-B radiation and physiological mechanism of marine microalga Asterarcys sp.
LYU Jinting, PEI Haiwei, WEI Huaning, WU Hualian, LI Tao, WU Houbo, XIANG Wenzhou
2023, 19(2): 78-88.   doi: 10.12131/20220140
[Abstract](139) [FullText HTML](45) [PDF 913KB](7)
In order to investigate the response of microalgae to UV-B radiation and their physiological mechanism, and to improve their potential value, we selected Asterarcys sp. SCSIO-44020 as material, and exposed them to UV-B radiation under different radiation conditions (0, 10, 30, 50 and 70 min each time, corresponding to radiation doses of 0, 150, 460, 770 and 1 050 mJ·cm−2) every 48 h until the end of the culture. The results show that, after a 20-day cultivation, UV-B radiation of 10–50 min treatment group had no significant effect on the growth of algae compared with the control group (P>0.05), but the 70 min treatment group inhibited the growth significantly (P<0.05). With the increase of UV-B radiation time, the protein content increased gradually, but the total lipid content decreased, with no siginificant differences between different groups and the control group (P>0.05). The total carotenoid and mycosporine-like amino acids (MAAs) contents increased with the increase of UV-B treatment time, and reached the maximum values in 70 min treatment group, 1.75 times that of the control group. However, compared with the control group, the total carbohydrates and MAAs yields in 50 min treatment group increased 12.40% and 57.61%, respectively, reaching the maximum values. In conclusion, Asterarcys sp. has a strong ability to resist UV-B radiation, and the increase of MAAs is the key to its adapting to UV radiation. Moreover, intermittent treatment of 50 min UV-B radiation is an effective approach to regulate the production of MAAs and other products in microalga.
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
2023, 19(2): 89-97.   doi: 10.12131/20220153
[Abstract](285) [FullText HTML](131) [PDF 850KB](15)
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 aquaculture working vessel. 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 beat 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 but the lactic acid increased non-linearly with increasing tail beat times. The flow rate over 2 BL·s−1 resulted in a significant increase in the cortisol in P. leopardus blood (P<0.05). When the flow rate reached 3 BL·s−1, lactic acid 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 aquaculture 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 aquaculture working vessel sloshing suppression and the site selection of cage aquaculture waters.
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
2023, 19(2): 98-106.   doi: 10.12131/20220187
[Abstract](174) [FullText HTML](65) [PDF 1060KB](16)
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 mainly played transcriptional regulatory roles in the heart, liver and kidney after 3 h of hypoxic stress. 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 understanding the genetic mechanism of hypoxic stress.
Effect of submerged macrophytes planting mode on performance and economic profit of all-male adult Eriocheir sinensis culture
ZHANG Guangbao, JIANG Xiaodong, CHEN Wenbin, ZHOU Wenquan, LUO Ming, WU Xugan
2023, 19(2): 107-115.   doi: 10.12131/20220260
[Abstract](206) [FullText HTML](94) [PDF 1013KB](35)
The mono-sex culture of adult Chinese mitten crab (Eriocheir sinensis) is a new culture mode, and Elodea nuttallii, Hydrilla verticillata and Vallisneria natans are common submerged macrophytes in the adult E. sinensis aquaculture ponds. We investigated the effects of four planting modes (Mode I, single planting of E. nuttallii; Mode II, single planting of H. verticillata; Mode III, mixed planting of E. nuttallii and H. verticillata in equal proportions; Mode IV, mixed planting of E.nuttallii, H. verticillata and V. natans in equal proportions) on the growth, gonadal development, culture performance and profitability of all-male E. sinensis. The results show that: 1) There was no significant difference in the body mass among the four planting modes, but Mode I group had significantly higher weight gain rate (WGR) and specific growth rate (SGR) than the other groups from September to October, and Mode II had the lowest WGR and SGR (P<0.05). 2) Among the Mode I–IV, no significant difference was found in the puberty molting rate, gonadosomatic index (GSI) and hepatosomatic index (HSI) of adult male E. sinensis (P>0.05), and at the end of August, the puberty molting rate was slightly higher in mixed planting of E. nuttallii and H. verticilla than in the single submerged macrophyte group, while Mode I group had slightly higher HSI and GSI than the other groups at mid-November (P>0.05), reaching about 7.8% and 3.3%, respectively. 3) As for the size distribution of adult males, Mode I group had the lowest percentage of larger-sized males (≥250 g) and the highest percentage of smaller-sized males (150–174.9 g and <150 g). The survival rate of all-male adult E. sinensis was significantly correlated to the planting modes of submerged macrophytes (P<0.05), and Mode II and Mode III groups had higher survival rates and yields but lower feed conversion rates. 4) For the economic assessment, Mode II and Mode III groups had higher feed input, and Mode II and Mode IV groups had higher input of aquatic plant. Besides, the total return, net profit and return-on-investment (ROI) were highest in Mode II group but lowest in Mode IV group. In conclusion, planting H. verticillata (Mode II) or mixed planting of E. nuttallii and H. verticillata (Mode III) can improve the culture performance and economic profit of all-male adult E. sinensis.
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
2023, 19(2): 116-123.   doi: 10.12131/20220048
[Abstract](304) [FullText HTML](81) [PDF 1048KB](13)
In order to solve the problems such as the current low level of automation in the fishing of Antarctic krills (Euphausia superba) in China, and the error in determining the fishing depth by manually observing the fish detector image, we proposed a dynamic truss trajectory planning method based on the metadata of Antarctic krill sonar equipment. First, we analyzed the data sent back by the underwater acoustic instrument EK80 scientific echo sounder, obtained the target intensity of krills at different depths, and used statistical methods to determine the krills resources at this depth, so as to get the densest depth (Y) of krills 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 krills. 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.
Effect of enzymolysis alginate oligosaccharide on myofibrillar protein in simulated oral digestion
CONG Haihua, ZHOU Qian, WU Youzhi, LU Xiaoyan, YANG Tian
2023, 19(2): 124-132.   doi: 10.12131/20220204
[Abstract](127) [FullText HTML](91) [PDF 934KB](5)
Processing silver carp (Hypophthalmichthys molitrix) into surimi products can improve consumers' acceptance and its economic value. Enzymolysis alginate oligosaccharide (EAO) can quickly react with myofibrillar protein (MP) extracted from silver carp to improve functional characteristics. Food will undergo physical and chemical changes after oral processing. To better understand the effects of oral digestion on the EAO-modified MP, we extracted the MP from fresh silver carp which was added 0.45 mg·mL−­1 EAO to create a complex (EAO-MP). Then we investigated the variations of Fourier infrared spectroscopy, endogenous fluorescence spectroscopy, UV absorption spectroscopy, contents of sulfhydryl and active sulfhydryl, surface hydrophobicity, and hydrogen bonds in the simulated oral digestion of silver carp MP (Group M) and EAO-MP (Group A). The results show that, after the simulated oral digestion, the random coil structure and total sulfhydryl content increased, while the surface hydrophobicity decreased significantly in Group M (P<0.05), which demonstrates that the secondary and tertiary structures of MP had changed due to the effect of simulated oral digestive fluid. Besides, the random coil in Group A decreased by 2.97% after adding EAO. At three different digestion times, the α-helix increased by 7.29%, 2.73% and 5.55%, respectively, compared with Group M. Additionally, the hydrogen bond content increased significantly in Group A (P<0.05), revealing that MP and EAO were bonded to a covalent polymer by the hydrogen bond force. The significant increase in surface hydrophobicity and decrease in sulfhydryl content show that the addition of EAO promotes the expansion of the protein structure of MP in simulated oral digestive fluid. In conclusion, the addition of EAO can promote the molecular structure of silver carp MP to expand in the simulated oral digestive fluid, which may be conducive to the subsequent digestion and absorption of protein.
Effect of osmosis treatment on meat quality and myofibrillar protein of freeze-dried tilapia
WEI Lina, LI Laihao, HAO Shuxian, HUANG Hui, YANG Xianqing, XIANG Huan, ZHAO Yongqiang, CEN Jianwei, WEI Ya
2023, 19(2): 133-141.   doi: 10.12131/20220256
[Abstract](143) [FullText HTML](58) [PDF 801KB](6)
In order to explore the effect of osmotic treatment on improving the freeze-drying efficiency of tilapia meat and the quality of dried products after rehydration, and to provide theoretical supports for the development of freeze-dried tilapia meat products, we pretreated the tilapia meat with salt, propylene glycol and compound penetrant (Salt+propylene glycol), followed by blanching and freeze-drying. Then we analyzed the effects of penetrant pretreatment on the cooking loss, freeze-drying characteristics, rehydration rate and myofibrillar protein characteristics of tilapia meat. The results show that salt, propylene glycol and composite penetrant could reduce the cooking loss and improve the drying efficiency of tilapia meat. The freeze-drying time of composite osmotic treatment was the shortest (19 h), and the drying time of fish after the salt and propylene glycol osmotic treatment was 20 h, which was significantly shorter than that of the control group (24 h). The propylene glycol and composite penetrant improved the rehydration of dried fish significantly (P<0.05), and the rehydration rate of dried fish treated with propylene glycol was the highest (71.11%), which was significantly higher than that of the control group (P<0.05). Salt penetration had a significant effect on the texture of dried fish after rehydration (P<0.05), among which hardness and elasticity had the greatest effects [(94.3±3.9) g and (3.44±0.23) mm, respectively]. Propylene glycol had no significant effects on the hardness of fish, but could improve the elasticity. The addition of salt accelerated the oxidation of myofibrillar protein, and the contents of myofibrillar protein and sulfhydryl decreased 0.32 mg·mL−1 and 0.47 μmol·g−1, respectively, while the surface hydrophobicity and carbonyl content increased 4.10 μg and 0.23 nmol·mg −1, respectively. SDS-PAGE shows that the myosin heavy chain band disappeared. Propylene glycol osmotic protective agent slowed down the formation of ice crystals and inhibited the protein oxidation during pre-freezing. The mass concentrations of ionic bond and hydrogen bond increased by 0.65 mg·mL−1 and 0.33 mg·mL−1, respectively, the mass concentration of disulfide bond decreased (P<0.05), which improved the protein stability. Therefore, the compound penetrant can inhibit the protein oxidation effectively during the processing process and keep good taste of dried fish after rehydration, which is suitable for the pretreatment of tilapia before vacuum freeze-drying.
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
2023, 19(2): 142-149.   doi: 10.12131/20220134
[Abstract](334) [FullText HTML](86) [PDF 946KB](11)
Agar and sodium alginate are hydrophilic colloids extracted from algae, with good film-forming and biodegradability. 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 value [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.
Research Notes
Cloning and expression analysis of SERCA gene of Sipunculus nudus in oocytes
SU Yonglin, ZHONG Ruzhuo, GUO Zhicheng, WANG Qingheng
2023, 19(2): 150-160.   doi: 10.12131/20220226
[Abstract](143) [FullText HTML](47) [PDF 2432KB](14)
The change of intracellular calcium (Ca2+) concentration is an important factor in oocyte maturation. As a member of the P-type ATPase family and a crucial regulator of intracellular calcium transport, sarco/endoplasmic reticulum calcium adenosine triphosphatase (SERCA) is a key enzyme. To investigate the function of SERCA in the development of the oocytes of Sipunculus nudus, we obtained the full length of S. nudus SERCA (Sn-SERCA) cDNA by using RACE technique, and determined the Sn-SERCA relative expression level in different oocyte developmental periods by using real-time fluorescence quantitative PCR (qRT-PCR). The results indicate that the overall length of the Sn-SERCA was 3 840 bp, the 5'UTR was 196 bp, the 3'UTR was 581 bp, and the open reading frame was 3 060 bp, encoding 1 020 amino acids. Sn-SERCA had TGES and DKTGT which were the P-type ATPase family's two conserved motifs and were necessary for catalytic reactions. According to multiple sequence alignment, motif analysis, and predictions of tertiary structures, the SERCA homologous proteins exhibited great conservatism. The phylogenetic tree analysis shows that the Sn-SERCA formed a broad branch with homologous protein sequences from invertebrates such as Lumbricus rubellus and Lingula anatine. The result of qRT-PCR demonstrates that the Sn-SERCA was significantly expressed in the late yolk vigorous synthesis period and had the maximum value during coelomic fluid development. When the oocytes moved to the nephridioduct, the Sn-SERCA expression was considerably higher than that at other time (P<0.05). The variable expression of Sn-SERCA in different periods of oocyte development suggests that Sn-SERCA is crucial in the development and germinal vesicle breakdown in S. nudus oocytes.
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
2023, 19(2): 161-169.   doi: 10.12131/20220197
[Abstract](272) [FullText HTML](78) [PDF 833KB](17)
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), specific growth rate (SGR), and 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%.
Effects of different light intensity on plasma biochemical indexes 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
2023, 19(2): 170-176.   doi: 10.12131/20220224
[Abstract](350) [FullText HTML](132) [PDF 721KB](24)
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 they 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 (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 on both sunny and cloudy days at 6:00, without significant difference. The immunoglobulin M concentration reached the maximum at 24:00 on both 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.
Display Method:
Effects of tea polyphenol on tissue and cell culture of Pinctada martensii mantle
FANG Wei, DING Ruixia, CHEN Mingqiang, WANG Yu, ZHAO Wang, WEN Weigeng, Ma Zhenhua
 doi: 10.12131/20230049
To improve the effects of tea polyphenols on tissue and cell culture of Pinctada martensii mantle, we explored the optimization effect of adding different concentrations of natural extract tea polyphenols on the mantle tissue and cell culture medium. The results show that when the added amount of tea polyphenols was 0.5%–2.0%, the biological activity of P. martensii mantle cells was significantly higher than that of the control group, and the best added amount was 1.0%. The five groups of completely culture medium (0%, 0.5%, 1.0%, 1.5% and 2.0%) all promoted the growth and proliferation of cells, and the growth curves of the cells were all in an "S" shape. When the addition of tea polyphenols was 1%, the proliferation effect of the mantle cells was the best. The mantle tissue and cells proliferated a large number of free cells and secreted nacre normally in the optimal culture medium. The mass concentration of Ca2+ in the culture medium decreased first and then increased along with the process of tissue and cell proliferation, but was always lower than the initial concentration. The study further optimized the P. martensii mantle tissue and cell culture medium, which provides a theoretical basis for promoting the cultivation of P. martensii nuclear pearls.
Seasonal variation of fishery resources in Wailingding marine ranching and adjacent waters
FENG Xue, DAI Xiaojie, FAN Jiangtao, CHEN Pimao
 doi: 10.12131/20220308
The Wailingding waters of the Pearl River Estuary have always been an important traditional fishing ground and migration channel for fishery resources. In recent years, great changes have taken place in habitats under the dual pressure of human activities and climate change. In order to deeply understand the seasonal variation of fishery resources, based on the survey data of the marine ranching in Wailingding waters of the Pearl River Estuary in 2020 and 2021, we applied the spatial analysis method to explore the seasonal dynamics and characteristics distribution of different catch species, and summarized the fishing ground center of gravity. The results show that the total resource density in spring was higher than that in autumn, distributing in a patchy pattern. In spring, fish schools were concentrated in the southern waters, but moved northwestward in autumn. The density distribution of fish resources was similar to that of total resources. In spring, the center of gravity of fish resources was located in the southwest direction, but moved northwestward in autumn. The resource density of crabs in spring was relatively uniform and increased in autumn, and the high-density sea areas increased, distributing in a flaky pattern, and the center of gravity of resources moved from west to northeast. The resource density of shrimps in spring was lower than that in autumn, and the center of gravity of resources moved northeastward. The resource density of mantis shrimps was low and the center of gravity of resources was located in the western sea area in spring, but moved northeastward in autumn. The resource density of cephalopoda in spring was higher than that in autumn, distributing in a flaky pattern, and the center of gravity of resources moved from east to west.
Killing effect of compound peroxymonosulphate powder on four common aquatic pathogens
LI Shengping, DONG Jing, YANG Yibin, SONG Yi, LIU Shaochun, AI Xiaohui
 doi: 10.12131/20230053
To study the disinfection validity of compound peroxymonosulfate powder in aquaculture, we evaluated its killing effect on grass carp (Ctenopharyngodon idella) reovirus (GCRV), channel catfish (Ictalurus punctatus) virus (CCV), Aeromonas hydrophila and Streptococcus agalactiae, and studied the germicidal effects of three factors (Organic matter, temperature and pH). Moreover, we conducted a killing assay of the target bacteria in pond aquaculture water and a pharmacodynamic test of crucian carp (Carassius auratus) with A. hydrophila disease. The results show that the compound peroxymonosulfate powder had a significant killing effect on the four pathogens. Reducing organic matter concentration in bacterial suspension, appropriately increasing temperature or decreasing pH of disinfectant could promote the germicidal effect. In addition, through the killing assay of target bacteria and pharmacodynamic test of crucian carp, we further confirmed the disinfectant validity on target bacteria and significant therapeutic effect of crucian carp infected with A. hydrophila. Thus, the study indicates that compound peroxymonosulfate powder can be used as a potential candidate for disinfectant in aquaculture.
Effects of replacement of fish meal by fermented cottonseed meal on growth performance, feed utilization and intestinal bacteria community of juvenile golden pompano (Trachinotus ovatus)
WU Guangde, LAN Kunpeng, CHEN Xu, WANG Yun, ZHOU Chuanpeng, LIN Heizhao, MA Zhenhua, WANG Jun
 doi: 10.12131/20230036
Fermented cottonseed meal (FCSM) is a high-quality plant protein ingredient with potential to replace fishmeal in feed. To evaluate the suitability of FCSM as a protein source in the diet of juvenile golden pompano (Trachinotus ovatus) and its appropriate replacement level, we had fed the juveniles with initial body mass of (12.57±0.25) g by five diets to replace 0% (Control group), 25%, 50% and 100% of fishmeal by FCSM for seven weeks, and the fish meal in reference diet was 35%. Then we investigated the effects of FCSM replacement of fishmeal on the survival, growth, feed utilization performance and intestinal microflora of the juveniles. The results show that the survival, growth, feed efficiency, dietary protein and lipid deposition rates were lower in FCSM treatments compared to those in reference diet, while the differences between 25%, 50% replacement groups and the reference diet were not significant (P>0.05). However, the liver antioxidant system was stimulated, and the activities of total superoxide dismutase (T-SOD) and catalase (CAT) in 75%−100% replacement groups were higher than those in the control group. In addition, the liver hematoxylin-eosin-stained sections show that the cellular vacuolation phenomenon was aggravated. The contents of total protein, albumin and globulin in serum in 100% replacement group were reduced, and the protein synthesis capacity of liver might be impaired. The high-level replacement of fish meal by FCSM affected the composition of intestinal flora, with the abundance of beneficial bacteria decreasing and that of harmful bacteria increasing. Taking into account both growth performance and fish health, it is recommended to replace fish meal with 25% FCSM in the diet for T. ovatus.
Comparative study on breeding density of Lutraria sieboldii in nursery culture and adult culture in Beibu Gulf beaches of Guangxi Province, China
WANG Chaoqi, XU Bingjie, WU Tao, YANG Ling, LIU Yiming, PAN Ying
 doi: 10.12131/20230046
In order to investigate the efficient nursery culture mode and reasonable breeding density of Lutraria sieboldii, we had carried out an experiment at three different beaches in Beibu Gulf, Guangxi Province (Beihai, Qinzhou and Fangchenggang) using the same density gradient from February 2021 to April 2022. Two nursery culture modes, box and basket, were employed, followed by adult culture in baskets to compare the growth performance and survival rate of L. sieboldii at each stage. The results indicate that the box culture mode was more effective than the basket culture mode in Beihai and Fangchenggang, while the basket culture mode was more suitable for Qinzhou. The appropriate densities in Beihai, Fangchenggang and Qinzhou were 1 500, 1 000 grains·box−1 and 500 grains·basket−1, respectively. At the adult culture stage, the appropriate density in Beihai was 40 grains·basket−1, and the survival rates at the end of the culture period in Qinzhou and Fangchenggang were 0. The results show that the changes of water temperature, beach temperature, salinity, pH and dissolved oxygen (DO) in Beihai are the smallest and the water quality environment is the most stable. Besides, the water quality environment in Qinzhou and Fangchenggang changes greatly and is unstable. The sediment particle size of Beihai beach is dominated by coarse sand and medium sand, whereas Fangchenggang and Qinzhou beaches is dominated by medium sand and fine sand, and Qinzhou beach is dominated by fine sand. The results of phytoplankton survey indicate that Beihai has the highest quantity and diversity of algae, followed by Fangchenggang and Qinzhou. Thus, it is showed that L. sieboldii is suitable for nursery culture in both Beihai and Fangchenggang sea areas, and for adult culture in Beihai sea area.
Development trend of trawl fishery and its impact on fishery resources in South China Sea
SU Li, XU Youwei, ZHANG Kui, CHEN Zuozhi
 doi: 10.12131/20230027
Trawl is the most important fishing gear in the marine fishery production of the South China Sea, in which trawl fishery occupies a dominant position. The number of trawlers increased from 6 730 in 1986 to 14 599 in 2003, then dropped and had remained at about 9 000 since 2010, with the gross tonnage of trawlers ranging from 212 864 t to 826 442 t, showing a steady increasing trend. However, the total power of trawlers increased from 440 438 kW in 1986 to 1 735 173 kW in 2005, and then showed a decreasing trend. The average tonnage and power of single vessels showed a significant increasing trend from 1986 to 2017, and the yield of trawl fishery ranged from 46.43×104 t to 172.79×104 t, accounting for 39.16%–62.96% of the total fishing production in the South China Sea with a significant decreasing trend. The yield per kilowatt ship and per ton ship ranged from 1.03 to 1.63 and from 1.40–3.90 t, respectively, both were highest in 1999 and then showed a decreasing trend. According to the statistical results of the proportion of juveniles of eight important economic fish species, the proportion of juvenile biomass and average proportion of quantity in the trawl catches from 1992 to 2020 was 24.35%–84.28% and 40.9%–89.84%, respectively. Pennahia argentata, Trichiurus japonicus and Trachurus japonicus had the highest proportions of the juveniles. Due to the poor selectivity of trawl operation, the damage to the juveniles and marine ecological environment is relatively severe. Therefore, we should control its operation area strictly, and operate trawls in the open sea, so as to promote the conservation and sustainable utilization of offshore fishery resources.
Prediction of dissolved oxygen in water of aquaculture ship based on CNN-GRU hybrid model
SU Huifeng, DING Lesheng, WANG Xuwang, CHEN Musheng, CHEN Xiao
 doi: 10.12131/20220298
Dissolved oxygen (DO) content is a critical factor that affects the healthy growth of aquatic products in aquaculture ships. Accurate prediction of DO content is necessary to improve aquatic production and quality. To increase the accuracy of DO prediction , we used data collected from a Trachinotus ovatus culture experiment as a sample, we established a hybrid model for DO prediction in aquaculture ships by applying the convolutional neural network (CNN) and gated recurrent unit (GRU) methods. Based on Pearson correlation analysis, we selected four predictors, namely dissolved oxygen content, temperature, pH value and circulating water flow, which were trained and calibrated to predict the DO content. The model proposed in this paper outperformed CNN, GRU and long short-term memory (LSTM) models in all evaluation indexes, and its root mean square error (RMSE), mean absolute error (MAE) and determination coefficient R2 were 0.119, 0.084 and 0.976, respectively. The results indicate that the model proposed in this paper has the greatest prediction precision and can meet the demand for DO content prediction in the actual production of aquaculture ships, which provides references for monitoring and early warning of DO content in the production process of aquaculture ships.
Prokaryotic expression and polyclonal antibody preparation of Nesfatin-1 protein in Micropterus salmoides
LIU Fan, LIU Xinxin, SONG Caixia, LI Xilei, ZHANG Jun, SU Shiping
 doi: 10.12131/20230012
Nesfatin-1 protein can affect fish adipogenesis and metabolism by regulating gene expression and signaling pathways. To investigate its physiological functions in largemouth bass (Micropterus salmoides), we constructed and purified a prokaryotic expression plasmid, and prepared a murine polyclonal antibody to this protein. The pET32a-Nesfatin-1 recombinant plasmid was obtained by amplifying the gene sequence of Nesfatin-1 protein and constructing a prokaryotic expression vector. The protein expression was induced by isopropyl-β-D-thiogalactosid (IPTG), and the fusion protein was purified by nickel ion affinity chromatography and immunized in Balb/c mice to obtain a polyclonal antibody against Nesfatin-1. The results show that the Nesfatin-1 protein had a gene sequence length of 246 bp; the concentration of the Nesfatin-1 fusion protein in the supernatant of the bacterial broth was 1.05 mg·mL−1, and its relative molecular mass was 30 kD. Western blot analysis shows that the polyclonal antibody could specifically bind to the recombinant protein; the potency of the antibody reached over 1: 204 800 by indirect ELISA. The results of immunofluorescence detection indicates that the antibody specifically recognized the protein in the hepatopancreas of largemouth bass and was diffusely distributed in the hepatopancreas, showing strong positive reaction around the blood vessels. In this study, the Nesfatin-1 fusion protein of largemouth bass was successfully expressed and purified, and a specific murine polyclonal antibody was prepared, which can provide the functional protein and specific antibody for further study of the biological role.
Environmental impact mechanism of skipjack tuna fishery in Western and Central Pacific Ocean based on Multi-scale Geographical Weighted Regression Model (MGWR)
ZHENG Haohao, YANG Xiaoming, ZHU Jiangfeng
 doi: 12131/20230014
Katsuwonus pelamis is an important resource for tuna purse seine fishing in the Western and Central Pacific, and its resource distribution is significantly affected by the environment. In order to explore the characteristics of spatial heterogeneity of environmental impact on tuna catch rate, we used the 1°×1° fishery and marine environmental data of the Western and central Pacific Ocean tuna purse-seine from 2005 to 2019 in mainland China, and investigated the standardized environmental factors and catch rates by using Multi-scale Geographically Weighted Regression (MGWR) method. The results show that: 1) Compared with the traditional Generalized Additive Model (GAM), the Geographically Weighted Regression (GWR) and MGWR with spatial heterogeneity of environmental impacts had improved the fit performance significantly. 2) Significant spatial non-stationarity was found for each environmental factor on the distribution of tuna resources. The degree of spatial heterogeneity (The magnitude of the coefficient of variation for each environmental variable) of each environmental factor on the distribution of tuna catch rate followed a descending order of Sea Water X Velocity at 55 m depth (U55) > Sea Surface Temperature (SST) > Net Primary Productivity (NPP) >Sea Water Salinity at 100 m depth (S100) > Sea Water Y Velocity at 55 m depth (V55). 3) The effects of the environmental factors were found to have significant scale effects. 4) Overall, the positive effects of S100, NPP, SST, V55 and U55 on the catch rate of tuna were 73.5%, 64.8%, 66.8%, 80.8% and 32.3% in order of magnitude; among them, S100, NPP and SST on the spatial distribution of bonito catch rate were similar, specifically in terms of east-west differences, with positive effects mainly west of 170°E and negative effects east of 170°E; U55 was the factor with predominantly negative effects.
Cloning, expression and application of a chitinase gene from Micromonospora aurantiaca
WANG Dou, YOU Jinruo, SHEN Xuanri, LI Yongcheng, XIA Guanghua, HE Yanfu, ZHANG Xueying
 doi: 10.12131/20230029
In this study, a novel carbohydrate 18 family chitinase gene Machi3 was cloned from the genomic DNA of marine microorganism Micromonospra aurantiaca and successfully expressed in Escherichia coli. The optimal reaction temperature and pH for MaChi3 were 55  ℃ and 7.0, respectively. MaChi3 showed good stability below 55  ℃ and at pH of 6−9. The activity of MaChi3 was slightly promoted by Mg2+, Ca2+, Tween 40 and Tween 80. The recombinant chitinase showed hydrolytic activity toward α-chitin, colloidal chitin, shrimp shell powder, chitosan (50%~95% of deacetylation), starch and cellulose, among which the highest activity of 2.24 U mg−1 was observed in colloidal chitin. The results of scanning electron microscopy suggests that the fiber structure of chitin became loose after pretreatment with HCl, so it was more favorable to the hydrolysis of MaChi3. The Km and Vmax values of MaChi3 toward colloidal chitin were 5.93 mg·mL−1 and 8.58 μmol·(min·mg)−1, respectively. In addition, the main product of colloidal chitin hydrolyzed by MaChi3 was N, N-diacetyl chitobiose with a yield of 285.54 mg·g−1. MaChi3 shows good catalytic activity, which is beneficial for its development and application in the biotransformation of chitin.
Study on error and correction model of fish length measurement based on imaging sonar
PENG Zhanfei, SHEN Wei, ZHANG Jin
 doi: 10.12131/20220279
Imaging sonar can measure the length of fish images within its scanning beam. To improve the accuracy of imaging sonar’s measurement of fish length, we conducted an experiment to determine the fish length by using Adaptive Resolution Imaging Sonar (ARIS). We compared and analyzed the fish length error in acoustic image based on the measured length of a trail fish and the image length at a known position of the ARIS scanning beam. The results indicate that the main influencing factor of fish image length measurement error was the angle between the fish and the sonar beam. As the angle increased, the measurement error of fish length decreased. There was no significant interactive effect of detection distance of ARIS on length measurement error of fish in the 4 M field. The error between the fish image length and the fork length was minimal, with an average error of 2.1 cm. Furthermore, the image length of fish had a good linear relationship with the total length and fork length, and the fitting degree R2 of the linear modified model was 0.995 1 and 0.990 5, respectively. The study shows that fish image length based on fork measurements is more effective. Additionally, the error analysis of the angle between fish and sonar beam on image length and the sonar image length modified model also provide preliminary references for obtaining more accurate fish length information.
Comparative analysis of dynamic stability characteristics of T0 and T90 codends
ZHANG Feng, TANG Hao, LIU Wei, SUN Qiuyang, ZHU Meixi, ZHANG Can, SHAN Chenxu, GUO Xuhao
 doi: 10.12131/20230018
Changing mesh orientation is a key appraoch to enhancing codend selectivity, but it may also alter the hydrodyna-mic performance of the codend. In order to quantify the differences in hydrodynamic and stability between T0 (A diamond mesh) and T90 (A 90°turned mesh) codends, we investigated the hydrodynamic characteristics, geometric shape, and fluttering motions of T0 and T90 codends with different twine diameters under varying flow velocities and catch sizes in a flume tank. Results show that the mesh opening angle in the middle part of T90 codend was approximately 1.2 times larger than of T0 codend. Moreover, the middle section of T90 codend had less shrinkage and greater width than T0 codend. The drag of T90 codend was, on average, larger than that of T0 codend and increased by 1.09 times with the simulated catch size. During the catch stage, the amplitude of the drag oscillations of the codend increased with increasing flow velocity and catch size, with T90 codend exhibiting larger amplitudes than T0 codend. There was no significant correlation between longitudinal displacement amplitude of the empty codend and current speed. Additionally, longitudinal displacement oscillations amplitudes in T0 codend were higher than those in T90 codend. The longitudinal displacement oscillations amplitudes in both codends increased with catch size and current speed, but decreased with twine diameter. The use of a thick diameter T90 codend can improve selectivity and stability, and increase the hydraulic resistance of the codend. The findings of this study can be applied to enhance the hydrodynamic characteristics, selectivity and stability of mid-water trawl codend.
Effects of dietary fishmeal replacement by Periplaneta americana meal on biochemical indexes, disease resistance and metabolomics of juvenile Oncorhynchus mykiss
CHEN Li, XU Jiaxin, LI Liujia, ZHAO Chengfa, LONG Xiaowen
 doi: 10.12131/20220208
Periplaneta americana is an insect protein source, rich in protein, fat and bioactive components, which may become a potential alternative source of fishmeal for development and application. In order to study the effects of dietary fishmeal replacement by P. americana meal on the growth, biochemical indexes, disease resistance and metabolomics of juvenile Oncorhynchus mykiss, we formulated two isonitrogen and equal energy diets to replace 0% and 50% of the dietary fishmeal with P. americana meal, and had fed the juveniles with an initial body mass of 3 g for 18 weeks. At the end of feeding trial, we challenged the juveniles with Aeromonas hydrophila. The results show that: 1) The growth performance and survival rate after the challenge in the experimental group were significantly higher than those in the control group (P<0.05). 2) The levels of serum immunoglobulin (IgM), total antioxidant capacity (T-AOC), lysozyme (LZM) in liver and catalase (CAT) in head kidney in the experimental group were significantly higher than those in the control group (P<0.05). 3) The results of metabolomics analysis shows that the differential metabolites in serum mainly involved in eight biochemical metabolic pathways, including glycerophospholipid metabolism, sphinolipid metabolism, Valine, leucine and isoleucine of biosynthesis and so on. The contents of lysophosphatidylcholine (LysoPC) and phosphatidylcholine (PC) which involved in glycerophospholipid metabolism were significantly up-regulated in the experimental group. In conclusion, 50% dietary fishmeal replacement with P. americana meal can improve the growth performance, antioxidant capacity, immunity and resistance to A. hydrophila of juvenile O. mykiss significantly.
Photophysiological response of Gracilariopsis bailinae to temperature and light intensity
HUANG Yongjian, CUI Jianjun, CHEN Xinyi, GUO Youyou, XIN Rong, LIAO Jiawei, CHEN Chunli, XIE Enyi
 doi: 10.12131/20220318
There existed species differences in the adaptation of macroalgae to temperature and light intensity. Gracilariopsis bailinae is a large algae that likes high temperature. In order to scientifically guide its application in mariculture and marine ecological restoration, we investigated the photosynthetic physiological response characteristics of G. bailinae to temperature and light intensity by using chlorophyll fluorescence technology, combined with changes in photosynthetic pigment content and growth rate of algae. We measured various physiological parameters, including specific growth rate (SGR), photosynthetic pigments content [Chlorophyll a (Chl a), carotenoid (Car), and phycobiliprotein], and chlorophyll fluorescence parameters [Maximum photochemical efficiency of PSII (Fv/Fm), actual light conversion efficiency (ΦPSII), electron transfer rate (ETR), and photochemical quenching (qP), and non-photochemical quenching (NPQ)] of G. bailinae cultured at five different temperatures (15, 20, 25, 30, 35 ℃) and four different light intensities (1 000, 3 000, 6 000, 9 000 lx). Results reveal that temperatures and light intensities had a significant interaction effect on the parameters measured, except for Car and Fv/Fm (P<0.01). The SGR, phycobiliprotein contents, and chlorophyll fluorescence parameters of G. bailinae increased significantly as temperature increased (P<0.05), whereas high light intensity treatment led to a significant decrease in photosynthetic pigments content and values of Fv/Fm, ΦPSII, ETR, and qP, but a significant increase in NPQ and SGR (P<0.05). These results indicate that G. bailinae can enhance its survival capacity under high temperature conditions by increasing the synthesis of phycobilin, and achieve photoprotection under high light conditions by increasing heat dissipation and decreasing photosynthetic pigment synthesis.
Pollution analysis and dietary exposure risk assessment of lipophilic toxins in shellfish from Beibu Gulf seafood market in Guangxi Province
JIANG Shanshan, ZHANG Chenxiao
 doi: 10.12131/20230024
Lipophilic shellfish toxins are widely distributed and will be transmitted to consumers through the food chain, posing a great threat to human health. The Beibu Gulf in Guangxi Province is an important mariculture area in China, accounting for more than half of the national output. To estimate the potential dietary exposure risk of coastal residents in that area, and to provide a scientific basis for the establishment of toxin limit standards, we analyzed the contents of lipophilic shellfish toxins by liquid chromatography tandem mass spectrometry. We have used a 24-hour dietary review method to investigate the consumption of marine products by coastal residents for seven consecutive days. Then we calculated the value of estimated daily intake (ESI) of toxins in the diet by using the marine biological toxin point assessment method, and evaluated the edible safety by comparing with the acute reference dose (ARfD) recommended by the European Food Safety Agency. The proportion of samples contaminated with toxins followed a descending order of gyrodimine (GYM) (83.02%), okadaic acid (OA) (51.16%), dinophysis toxin (DTX-2)(40.91%) and homo-yessotoxin (Homo-YTX) (8.6%), with the peak values of 105.4, 31.39, 38.19 and 159.6 µg·kg−1, respectively. The concentrations of toxins varied with different seasons and species. Among the six kinds of shellfish, the highest contents of OA and GYM were found in oyster samples, and the peak values were found in winter and autumn samples, respectively. The contents of DTX-2 in autumn and winter samples were significantly higher than those in spring and summer samples. Homo-YTX was only detected in scallop and mussel samples in summer and autumn. Dietary survey shows that the average daily shellfish consumption of coastal residents in Beibu Gulf was 45 g·d−1. The ESI value in OA toxin was estimated to be 0.26 μg·(kg·d)−1 based on the shellfish consumption and body masses of local residents, less than the ARfD value [0.3 μg·(kg·d)−1] set by the European Union (EU). However, based on the shellfish consumption and body masses of local residents provided by the EU, the ESI value [0.34 μg·(kg·d)−1] was higher than the ARfD value. The results suggest that although the detection rate of lipophilic shellfish toxin in shellfish samples was lower than the safe limit value set by the EU, there is a risk of dietary exposure to OA toxin for the Beibu Gulf residents.
Effect of Oceanic Niño index on interannual CPUE of yellowfin tuna (Thunnus albacares) in Western and Central Pacific Ocean based on ARIMA model
WANG Xiao, LIU Wenjun, ZHANG Jian
 doi: 10.12131/20230007
As a highly migratory pelagic fish, yellowfin tuna (Thunnus albacares) has high ecological and economic value. The western and central Pacific Ocean (WCPO) is the sea area with the highest tuna production of all oceans. In order to understand and predict the response of yellowfin tuna to climate change at different life stages in WCPO, we used the catch data of yellowfin tuna in purse seining and pelagic longlining and Oceanic Niño index (ONI) data from 1990 to 2020 in the WCPO to validate the applicability of general ARIMA (Autoregressive integrated moving average) model and dynamic ARIMA model, and to explore the influence of the ONI on the interannual CPUE (Catch per unit effort) of yellowfin tuna. The results show that: 1) General ARIMA models could be used for long-term fitting of annual CPUE of yellowfin tuna in the WCPO, taking full account of the variability characteristics of annual CPUE of yellowfin tuna. 2) Compared with the general ARIMA model, the dynamic ARIMA model provided a better fit and a higher correlation between the fitted and true values, as well as smaller mean absolute and root mean square errors. 3) The influence of the ONI on the annual CPUE of yellowfin tuna differed between the northern and southern equatorial regions of the WCPO, with the ONI being a more critical factor and a better model fit relatively north of the equator. 4) The ONI had different impacts on the annual CPUE of yellowfin tuna in different fisheries in the WCPO, with a 1–2 years' lag in the ONI for the yellowfin tuna longline fishery in the WCPO, and a faster impact on the purse seine fishery during strong El Niño and strong La Niña events, without a lag.