Abstract:This study applied cluster analysis and MDS sequence analysis to catch-rate data of fish species from bottom-trawl surveys in the Bohai Sea in August of 2012 to 2016. We selected keystone species of the fish community in the Bohai Sea, based on the annual contributions of similar species within clusters and different species between various clusters. (1) When the similarity contribution rate ranged from 29.93% to 35.69%, the fish communities in the Bohai Sea were clustered into 7, 9, 6, 5 and 6 groups for 2012-2016 consecutively, with corresponding MDS coefficients equaling 0.16, 0.14, 0.18, 0.15, and 0.17 respectively. (2) There were significant differences (=0.001) in the species composition of the fish community groups among the five years. The fish species were identified for each year that had cumulatively contributed to about 80% of the difference between community groups and occurred in more than half of the groups. Unfortunately, no common species was identified for all five years. was identified in three years. For species which contributed to more than 10% of the between-groups difference and displayed a more than 50% of occurrence in a year, none occurred in four or five years, only occurred in three years. (3) Similarly, the fish species were identified for each year that had cumulatively contributed to about 80% of the difference within groups and occurred in more than half of the groups. No species were common to three or more years. Three species (i.e. Synechogobius hasta) occurred in two of the five years. For species which had contributed to more than 10% of the within-groups difference and displayed greater than 50% occurrence in a year, no species occurred in more than four years, only Chaeturichthys stigmatias and occurred in two years. (4) Based on the annual cumulative or single similarity or difference contribution rates of every fish species to community groups, we conclude that is the primary keystone species in the fish community structure of the Bohai Sea, the Chaeturichthys stigmatias and . This conclusion is supported by the ratio, correlation, and regression of the average catches per station of these four species to that of all the pelagic or demersal species, and the annual dominance indices of these species. Results of this study provide a scientific basis for the adjustment of the fishing industry and the maintenance of fishery resources in the Bohai Sea.

Abstract:Tilapia () is one of the most important fishery species in the world and has been introduced and cultured widespreadly because of its fast growth rate, strong reproductive capacity, good adaptability and omnivorous feeding habit. However, disease has become the biggest threat for tilapia breeding. Recently, the epidemic and outbreak of tilapia disease caused substantial economic losses to aquaculture industry. Breeding resistant variety in tilapia was unimportant way to solve the problem of disease. The molecular marker assisted selection (MAS) has become an efficient breeding method for selecting and breeding tilapia, and will accelerate genetic improvement and increase selection intensity for disease resistance. The single nucleotide polymorphism (SNP) markers are used in many genetic and breeding studies because they are abundant in genomes, and can be genotyped easily. Ikaros is a kind of transcription factor with zinc finger structure that is essential to the development of lymphocyte and to the maintenance of normal immune function. Therefore, to obtain large amount of effective SNP molecular genetic markers and to perform MAS for disease resistance in tilapia, it is essential to study immune related candidate and to examine whether the SNPs in the gene are associated with disease resistance. In this study, the 5' regulatory region sequence of , length of 4178 bp, were obtained through Genome Walking method from . Bioinformatics software was used to analyze the 5' regulatory region sequence of gene. The predicted transcriptional start site (TSS) was in the initiation codon (ATG) upstream of 931 bp, and the core promoter regions was located at -57 bp to 48 bp when the TSS was specified as 1. The predicted promoter regions of gene included basic start of substructure components:TATA box, CCAAT box and octamer. The analysis of transcription factor binding sites (TFBS) showed that abundant of TFBS were located at -2200 bp to 1200 bp in 5' regulatory region of gene, such as GATA-1, Homeobox, CDP CR3+HD and AP-1. The analysis of CpG islands showed that two CpG islands were in 5' regulatory region sequence of gene, one of which was located in promoter regions and the other of which was located in the first exon. Five SNPs in the 5' regulatory region of gene were detected by direct sequencing method from the parents (P₀), which are named SNP1 (g.562, G>A), SNP2(g.217, G>T), SNP3(g.-53, C>T), SNP4(g.-220, T>C) and SNP5(g.-579, T>C). The five SNPs were sited in various regulatory elements in promoter regions which could have major implications for exact expression of gene. Based on Snapshot method analysis, the frequencies of alleles and genotypes were calculated in susceptible groups and resistant groups of ). The polymorphisms and genetic parameter of the SNPs in resistant groups and susceptible groups were calculated by software Popgen 32 and PIC. The result showed that the polymorphism information content (PIC) of the 5' regulatory region of SNPs was 0.0872~0.3747, suggesting that all the SNPs had moderate of intermediate polymorphism. The correlation between SNPs and resistance to was analyzed by software SPSS 17.0, the results showed that four of them (SNP2, SNP3, SNP4and SNP5) were significantly associated with the resistance to <0.05). Moreover, All of the SNPs in the 5' regulatory region of could formed one haplotype block and five haplotypes from the prediction of linkage disequilibrium analysis used software Haploview 4.2. The haplotypes (GGCTT) were significantly associated with the resistance to <0.05), and two of the haplotypes (GGTCT and GTCCC) were significantly associated with <0.05). Furthermore, the SNP2 and SNP5 were completely linked with each other ('=1), which could be selected as tag SNP for research of genetic breeding in . The results suggest that the four SNPs (SNP2, SNP3, SNP4 and SNP5) and the haplotypes (GGCTT) in the 5' regulatory region of could be potential genetic markers for future molecular selection of .

Abstract:Reisigl, a coccoid green microalga, is an oleaginous alga that can accumulate an unprecedentedly high level of arachidonic acid (ArA, 20:4w6)-rich triacylglycerols (TAG) under the growth stress of nitrogen starvation. ArA accounts for 68.0% of total fatty acids in TAG. How is ArA preferentially utilized for the biosynthesis of TAG? The Lands' cycle plays an important role in the composition change of fatty acids of phospholipids, thus altering the composition of fatty acids in TAG. Lysophosphatidylethanolamine acyltransferase (LPEAT), a key enzyme in the Lands' cycle, was the focus of the present study. was cloned using reverse transcription-PCR and 3°-and 5'-cDNA rapid amplification of cDNA ends technique. The full-length cDNA was 1303 bp long, and contained a 129-bp 5'-untranslated region (UTR) and 193-bp 3'-UTR. The length of the open read frame was 981 bp that encoded a 326-amino acid protein. The DNA sequence of with the isolated algal genomic DNA as a template, and it was 1871 bp long. Comparison of the cDNA and DNA sequences showed that possessed 6 introns that separated the coding sequence into 7 exons. Multiple sequence alignment and bioinformatics analysis of LPEATs from different species demonstrated that MiLPEAT possessed a phosphate acyltransferase domain, PlsC, thus suggesting that it was one member of the lysophospholipid acyltransferase (LPLAT) superfamily. MiLPEAT also had the 4 typical motifs, NH(x)₄D, GCxYVxR, FPEGT, and PVxPVx, which are characterized in the LPLAT superfamily. Both the prediction, as analyzed online by Wolfsport and Protein Prowler, and the presence of a dilysine motif at the carboxyl terminus of MiLPEAT, implied that MiLPEAT might reside at the algal endoplasmic reticulum and possibly participate in the secretion pathway. A neighbor-joining phylogeny was constructed on the basis of deduced amino acids of LPEATs from different species of plants. It illustrated that MiLPEAT was so different from LPEAT2 that they located at different clades due to their various characteristics of sequences. MiLPEAT was clustered phylogenetically with LPEAT1, suggesting their similar functions in the acylation of phospholipids. Quantitative real-time PCR detection pointed out that <0.05) at 8 h after treatment with nitrogen starvation in . By coincidence, the relative abundance of lysophosphatidylethanolamine (LPE) in the microalgal cells reduced by approximately 49% at an extreme significance level (<0.01) under the nitrogen starvation stress. The corresponding phosphatidylethanolamine (PE) generated from LPE as catalyzed by MiLPEAT, however, did not increase significantly. It is assumed that the net increase of PE under nitrogen starvation in was possibly utilized for TAG biosynthesis by the phospholipid DAG acyltransferase (PDAT), so that the content of TAG has been reported to increase. This research lays a foundation for us to understand the TAG and phospholipid biosynthetic pathway and how to regulate TAG synthesis in .

Abstract:The Pacific oyster, , is an aquatic species which is widely cultivated globally and cultured mainly in Liaoning, Shandong, and Jiangsu Provinces in China. In recent years, various problems such as disease and natural-resource depletion have brought enormous economic losses to the culture industry of owing to its rapid expansion. Therefore, studies on selective breeding for more stress-resistant strains are necessary. In the present study, we estimated the growth performance, heritability, and breeding value of ‘Haida No.1’ to analyze the growth and breeding performance using full-sib family mating experiments. In 2015, 21 full-sib and seven half-sib families were bred. We measured the shell height, shell length, shell width, and total weight of 30 individuals in each family at 200 days after hatching. The results showed that the shell height, shell length, shell width, and total weight were 17%, 27%, 29%, and 85% higher on day 200 compared with the natural population respectively. The heritability on day 200 ranged from 0.128 to 0.145, which is medium-low heritability Phenotypic correlation and genetic correlation were positive and ranged from 0.730 to 0.962 and from 0.503 to 0.768 respectively. Comparisons between the selection based on breeding value and phenotypic value, were approximately 70% consistent at the individual level and 70%−90% consistent at the family level. Selection efficiency for growth traits was 3%−34% higher at the family level and 17%−28% higher at the individual level based on breeding value than that based on the phenotypic value. The study can provide basic data for management of and expanding ‘Haida No.1’.

Abstract:To correctly determine the genetic structure of wild populations from Haihe, Yellow, Huaihe, and Yangtze River basins in Henan Province, we analyzed the population genetic diversity and differentiation of the species using mitochondrial CO I gene. A total of 110 individuals were sequenced, which have defined 40 distinct haplotypes. The average haplotype diversity and nucleotide diversity were 0.92077 and 0.02439, respectively. Analysis of molecular variance (AMOVA) indicated that most of the genetic variation existing among populations (60.59%), and the remaining 37.67% of genetic variation was attributed to differentiation within populations. The assignment of populations based on Neighbor-Joining (NJ) method revealed that populations from Yangtze River divided into two distinct mitochondrial DNA lineages, one clustered from the ZY population and the other clustered individuals from Haihe River, Yellow River and Huaihe River. This phylogenetic pattern is not consistent with the previous reported North and South Clades. Demographical history analysis indicated that populations had undergone a bottleneck which coincided with the middle Pleistocene and suffered from climate changes. Considering the genetic and phylogeographic results obtained in this study, appropriate measures are proposed to conserve population, especially for those with low genetic diversity in Haihe River basin.

Abstract:, an economically important, cold-water fish species, has rich nutritional value and high economic value. With the increase in artificial breeding and breeding intensification, the germplasm resources of have been degraded, which is revealed in individual miniaturization, slow growth, and decreased disease resistance. Therefore, it is necessary to screen the molecular markers of growth traits and use molecular-marker-assisted breeding. In order to acquire some reliable molecular genetic markers for growth-related traits, the correlation analysis of 26 SNP markers and growth-related traits in were analyzed using 114 samples with the same growth conditions. A principal component analysis showed that body weight accounted for 93.42% of the variance, the eigenvalue was greater than 1 and the accumulative variance ratio was more than 85%, and it was the first principal component of the growth traits of . Correlation analysis between genotypes of SNPs and growth traits indicated that <0.05), and showed a significant influence on total length and body length (ug25050-0-1678 and body weight, body height, total length, and body length ( and the body weight, body height, and body length were significantly associated (<0.01). We also estimated that the genetic diversity parameters for 4 loci were significantly correlated with the growth traits. The mean observed heterozygosity, expected heterozygosity, and polymorphism information content (PIC) were 0.2369, 0.2110 and 0.17 respectively. The polymorphism of ug25050-0-1678 and were significantly associated with growth traits, and could be used as important candidate molecular markers for breeding selection of . Our results could provide an effective basis for the study of genetic improvement and selective breeding in

Abstract:This study was conducted to investigate the effects of water temperature and fish size on feeding and growth of the lenok . The experimental fish of three sizes (7 g, 68 g, and 169 g) were reared at five water temperatures (6℃, 10℃, 14℃, 18℃, 22℃) using artificial diet. The results showed that the maximum feeding rate () was observed at 18℃ in small size, 14℃ and 18℃ in middle size, and 14℃ in large size () was obtained at 14℃ and 18℃ in small size and middle size, and at 14℃ in large size (<0.05). The maximum feeding rate and energy content of the lenok increased with increased fish size, however, the special growth rate decreased with increased fish size. Multiple regression model of SGR_w, of the lenok in relation to temperature and fish size was ln2-0.0157-0.0147T²-0.0021C_max and <0.05), while no interaction on SGR_w of the lenok between temperature and fish size was observed (>0.05). The results suggested that the optimum temperature for different fish sizes of the lenok was similar, which was between 14-18℃ based on maximum feeding rate (w).

Abstract:is an endemic fish in the upper Yangtze River. Due to overfishing, hydropower development and other human activities, the natural resources of have decreased during recent decades. The significance of behavioral studies for animal protection is widely accepted. The compilation and analysis of ethograms is the basis of further research on animal behavior. Due to variations in living environments, accurate ethograms of fish should be based on behaviors obtained from natural or semi-natural conditions. The present study aims to establish the behavioral ethogram of in nature. From November 2015 to March 2016, field behavioral observations of were conducted in the Guosheng River, which is located in Sichuan Province, China. A short reach of the Guosheng River, with a length of about 100 m and width of 10 to 13 m, was enclosed as the observation site. A total of 56 pairs of mature parents were released to the enclosure. The river could pass through the enclosure, but experimental fish could not escape. The behaviors of were recorded using underwater cameras and sampled by focal animal and was coded under the "posture, act, and environment" (PAE) coding system. A total of 10 postures, 22 acts, and 43 behaviors were recorded. According to biological functions, the recorded behaviors of were divided into 11 types, including ingestion and elimination, exploration, territoriality, estrus, mating, epimeletic, conflict, locomotion, aggregation, rest and sundry. The relative frequency and occurrence season of each behavior in relation to gender and juvenile were also given out. The behaviors of the juveniles were relatively simple and mainly related to ingestion, elimination, aggregation, and resting. The behaviors of matured were diversified with obvious gender differences, especially in the reproductive behaviors. During the reproductive season, female spent most of the time resting and showed few behaviors such as swimming or mating. While male showed various behaviors, especially endemic behaviors like territorial behavior, sneak mating, and epimeletic behavior. Gender differences in behaviors may reflect the reproductive strategy of , in which more energy is allocated for oocyte development in females and for behavior in males. The behavioral types of aquatic animals are significantly fewer than that of terrestrial higher animals, which may relate to the lower evolutionary level and simpler living environment of aquatic animals. The present study may enable further behavioral and protection research in , and give a reference to behavioral ethogram studies in other fish species.

Abstract:The carapace exoskeletal structure, and its change during the molt cycle of were studied using hematoxylin-eosin staining and the observation of paraffin sections using scanning electron microscopy (SEM). The results showed that the exoskeleton in the intermolt stage (C) is composed of three sub-layers:epicuticle, exocuticle, and an endocuticle, from the outer to the inner layer. The newly formed epicuticle, exocuticle, and endocuticle in the carapace occur in the late premolt D₄ and postmolt B stages. The exocuticle is in a strongly basophilic state but the endocuticle is in a weak eosinophilic state. The observation by SEM revealed that, in stage C, both exocuticle and endocuticle have lamellae comprised of parallel sheets of chitin-protein fibers, with abundant pore canals (pc). The stacking density of the lamellae in the exocuticle is higher than that in the endocuticle. The lamellae edges of the exocuticle are regular and the pore canals within them are approximately circular. On the other hand, there are rough edges and unequal-sized, fusiform pore canals in the endocuticle. There is a significant change in the ultrastructure in the newly formed exocuticle after molt. In stage D₄,the ultrastructure of the exocuticle is loose, and similar to the old endocuticle from stage C; however, the density of the exocuticle increases in stage A, which may be associated with calcification after molting.

Abstract:The pacific white shrimp, , is becoming one of the most popular cultured species in the world due to the advantages of rapid growth, low demand for animal feed and a high survival rate at high density. The has wide adaptability to salinity and better resistance to stresses, and successfully cultured in the alkaline water in China. In order to further improve the effect of aquaculture in alkaline water for better effective utilization of alkaline water, we carried out genetic breeding experiment of in alkaline water environment. The comparative experiments among 61 families of on the body weight and the survival rates were carried out in alkaline water (AW) environment. After 50 days of culture test, the results showed that body weight and survival rates of different <0.01) in AW, and the mean and CV were 7.25 g and 26.61%, 36.26% and 46.82%, respectively. In the meantime, different growth performance was observed among different families AW. The absolute growth rate (AGR) and specific growth rate (SGR) were 0.09 g/d and 1.82%/d. And the body weight of family 5121 was biggest in AW environment, AGR and SGR is 0.16 g/d and 2.34%/d, 7.54% higher than the mean of the families, and 12.95% higher than that of the lowest. The survival rates results indicated that the difference of survival rates of families in AW was significant, which was 26.61%, and the survival rates of each families were ranged from 1.00% to 63.33% in AW. The survival rates of family 5032 was the highest in AW environment, which was 63.33%, 36.72% higher than the mean of the families, and 62.33% higher than that of the lowest. The results suggested that the family selection of in AW environment has great genetic improvement potentials, and may provide a good reference for the next phase of the tolerance to AW environment of family selection. Through continuous family selection, it is possible to develop more suitable breed of for alkaline water. This will be of great significance for effectively promoting the health culture of in the alkaline water.

Abstract:In the present study, full length cDNA, encoding the ), was cloned using 3' Race and 5' Race techniques, and the sequence and structural analysis of was conducted using bioinformatics methods. The results showed that the full-length cDNA encoding consisted of 2021 bp nucleic acids in length, including a 5'-UTR of 36 bp, a 3'-UTR of 656 bp and an open reading frame (ORF) which encoded 442 amino acids. Analysis of the protein domain features showed that the deduced polypeptides contained two conservative domains characteristic of MH1 and MH2. Multiple sequence alignment revealed that the amino acid sequences of EsSmad3 have the 0.679, 0.691, and 0.619 identity with respectively. The tissue distribution of mRNA in sexually mature individuals and different muscle groups during the molt cycle in juvenile crabs, were analyzed using quantitative real-time PCR (qRT-PCR). In sexually mature crabs, the transcript was detected in the eyestalk, claw muscle, ovary, heart, hepatopancreas, epidermis, testicle, gill, and triangular membrane, and the expression level was relatively high in the eyestalk and testicle, and was low in the hepatopancreas and heart. In juvenile crabs, the transcript in different muscle groups was different depending on the molt stage. In walking leg muscles, the expression level was higher in inter-molt C stage than in the later pre-molt D_3-4 and post-molt A-B stages, but there was no statistically significant difference ( expression level decreased rapidly in the pre-molt D_3-4 stage (<0.05) and increased in the post-molt A-B stage, lasting to the inter-molt C stage ( expression level was much higher in the inter-molt C stage than in the post-molt A-B stage (stage. These results suggest that the expression of transcript in different muscle groups was related to the molt stage of is involved in muscle atrophy, growth, and rebuilding during the molt cycle of

Abstract:In order to increase the analysis efficiency of microsatellites in Chinese mitten crab (), we report four highly informative, multiplex PCR panels developed from 16 microsatellite markers. The multiplex PCR panels were used to evaluate the genetic diversities and parentage assignment for 95 individuals in 3 families. The results showed that the 16 microsatellite markers screened in this study were rich in polymorphism, for example the average of observed heterozygosity (_e) was 0.8164, and the average of polymorphism information content (PIC) was 0.7927. Cervus 3.0 software was used to determine parentage assignment for 95 individuals in 3 families, and the results revealed that the accuracy of parentage assignment using any 2 groups of multiplex PCR panels was more than 94.74%. When using any 3 groups of multiplex PCR panels, the accuracy of parentage assignment was greater than 98.95%. The accuracy of parentage assignment was greater than 100% using all four multiplex assays. Using the combination of set 1, set 2, and set 3, or the combination of set 1, set 3, and set 4, the accuracy of parentage assignment also reached 100%, so the selection of these combinations of multiplex PCR panels can not only get accurate genealogy information, but also reduce workload and costs. Therefore, these multiplex PCR panels can provide a convenient and efficient way for breeding and family management of .

Abstract:Development of embryos, larvae, and juveniles of were observed using an optical microscope, with a digital camera at water temperatures of 28℃ to 29℃ and salinity of 24 to 25. Zygotes began the first cleavage at 50 min post-fertilization, developed to D-shaped larvae between 22 and 24 h, and the larvae developed eye points and feet at day 11 and entered the attachment metamorphosis stage. There was no significant difference in the time of embryo development between the selective and control lines (>0.05). The shell length and shell height were not significantly different at the embryonic and early larval stages between the selective and control lines (>0.05), but there was a significant difference in shell length and shell height at the post-larval and attachment metamorphosis stages between the selective and control lines (<0.05). The metamorphosis and survival rates of the selective line were significantly different from those of the control line (<0.05), and the selective line has obvious advantages. The results show that the growth of the early planktonic larval stage of was slow but at the post-larval and juvenile stages, it was rapid. The growth of shell length and shell height of was not synchronized. The growth speed of shell length exceeded that of shell height at the earlier larval stage, and at the later larval stage, the growth speed of shell height exceeded that of shell length; at 28 to 30 days, shell height exceeded shell length. At the larval and juvenile stages, the growth of the selective line significantly exceeded that of the control line. The selective line has obvious growth advantages and growth potential.

Abstract:Cells cultured play an important role in organism-resource protection and functional identification of genes, as well as mechanism exploration and prevention of animal disease. However, tissue cells that can survive for a long time are limited at present in marine shellfish. In this study, primary cultures of heart cells from the scallop were started using an explant method, and a primary culture system-which can keep the cells alive for a long time -was established using an optimizing-medium method. Effects of three basic media (L-15, M199, and L-15+M199) on the number of migrated cells from the explants and cell survival time were compared; the L-15 medium was verified to be the optimal basic medium for heart cells. Furthermore, the optimal supplemental-factor combination for heart cells was the L-15 medium supplemented with 5% FBS, 50 mmol/L taurine and 6 mmol/L Ca²⁺ (orthogonal experiment of three factors and three levels), in which cardiomyocytes could survive for 2 months . In this study, the results show that low concentration serum (5% FBS) was most favorable for the migration of cells from the tissue mass. With an increase in FBS concentration, the cell-migration ability was weaker, and the survival time of primary cells became shorter. After the addition of taurine, the survival time of primary cells was significantly prolonged. However, the Ca²⁺ (2 mmol/L, 4 mmol/L, and 6 mmol/L) had no significant effect on heart-cell cultures. Perhaps the additive taurine regulated intracellular Ca²⁺ to a suitable level, resulting in the addition of Ca²⁺ without significant improvement in the primary culture. In this primary culture, most cells were cardiomyocytes; part of the cardiomyocytes beat at regular intervals within a short time, and cardiomyocytes and myotubes were formed in part of the region. This phenomenon was also reported in the primary culture of heart cells of This study provides a useful foundation for further studies on basic biology and functional genes.

Abstract:Color polymorphism is relatively common in marine mollusks. Shell color affects the visual perception of products which, consequently, influences consumer preference and product value. To increase the value of the Pacific oyster (), five shell color strains (black, purple, orange, golden, and white) of have been developed through successive, selective breedings. The aim of this study was to evaluate the difference in the chemical composition and nutritional value of different organs of five shell-color strains and one control population. In this study, five biochemical compositions in adductor muscle, mantle, gill, and gonad-visceral mass were detected, including moisture, total protein, total fat, glycogen, and ash. Results indicate that the purple-shell strain showed a significantly higher fat content in the adductor muscle than that of the orange-shell strain (<0.05). The golden-shell strain showed significantly higher glycogen than in the black-shell, orange-shell, and control population, while the white-shell strain had significantly larger ash content in the mantle compared to the control population (<0.05). In addition, the orange-shell, purple-shell and white-shell color strains showed significantly lower glycogen in the gill than in the control population (<0.05), whereas there was no significant difference in the contents of five biochemical compositions in gonad-visceral mass between the control population and five shell-color strains. The nutritional composition appeared significantly different among the four organs. These results indicate that nutritive content significantly changed in the process of selective breeding, providing useful information for developing shell-color strains in future.

Abstract:This study investigated the effects of the partial substitution of dietary fish meal by corn-gluten meal on the growth, intestinal histology, and structure of intestinal bacteria in juvenile large yellow croaker () (mean initial weight 10.49 g±0.03 g). Six isonitrogenous (45% crude protein) and isolipidic (10% crude lipid) diets with various dietary protein levels (0%, 15%, 30%, 45%, 60%, and 75%, designated as FM, CGM15, CGM30, CGM45, CGM60, and CGM75, respectively) were formulated and fed to triplicate groups for 56 d. The results showed that the survival rate (SR), specific growth rate (SGR), and feed conversion ratio (FCR) were not significantly affected (>0.05). The observed intestinal histology (mucosa thickness, mucosal fold height, and goblet cell quantity) was not significantly affected in all of the groups (>0.05), but some epithelial cells in the CGM60 group were destroyed or rearranged in a disorderly manner and parts of the striated border and intestinal villus were destroyed, the mucosal fold height in the CGM75 group was lower than that in the other groups, and the density and numbers of mucosal folds decreased. An Illumina MiSeq high-throughput sequencing analysis of intestinal contents showed that the Chao1, Shannon, and Simpson indices, and Good's coverage in FM, CGM15, and CGM75 were not significantly affected (>0.05). The Firmicutes and Proteobacteria groups completely dominated the bacterial communities in juvenile , and genera were the most dominant bacteria in the microbial ecosystem. At the genus level, compared to the control group, the abundances of <0.05), the abundances of <0.05), and the abundance of <0.05). These results suggest that the optimal dietary-protein level is about 45% without adverse effects on growth, intestinal histology, and structure of intestinal dominant bacteria in juvenile .

Abstract:A 56-day feed trial was carried out to investigate the effects of chitosan oligosaccharide (COS) and/or mycotoxin adsorbent on the intestinal mucosa structure and gut flora of . Four isonitrogenous and homoenergetic diets were prepared on the basal diet by adding 0 mg/kg (COS or mycotoxin adsorbent), 250 mg/kg COS, 2500 mg/kg mycotoxin adsorbent, 250 mg/kg COS+2500 mg/kg mycotoxin adsorbent, and named as C0, C0.25, M2.5 and C0.25+M2.5, respectively. The with an initial weight of 0.23±0.02 g were randomly assigned into 4 groups. The results showed as follows:the combined use of COS and mycotoxin adsorbent helped improve the index of intestinal morphology, group C0.25+M2.5 showed significant difference (<0.05) about the intestinal villus length with group C0, C0.25, and showed significant difference (<0.05) about the intestinal width with group M2.5, moreover, the thickness of muscle layer in this group was significantly higher than others (>0.05) about effective OTUs (Operational taxonomic unit) among groups; index of Observed species and Shannon index and PD (Phylogenetic diversity whole tree) value in group C0.25+M2.5 were significantly lower (<0.05) than those of group M2.5 and remarkably higher than group C0.25, but showed no significant difference (>0.05) with group C0. At the phylum level, microbial floras detected in this experiment mainly belonged to Proteobacteria, Firmicutes or Bacteroidetes, group C0.25+M2.5 showed the minimum of Proteobacteria and the maximum of Firmicutes, group C0 showed the minimum of Bacteroidetes. At the level of genus, species mainly detected were and in group C0.25+M2.5 were lower than that of control group. Group C0.25+M2.5 showed the lowest content of Photobacterium and the highest content of Pseudoalteromonas. It can be concluded that adding COS and mycotoxin adsorbent in diets had no effect of on microbial floras, nevertheless, optimized the index of intestinal morphology and the structure of gut flora, but can promoted intestinal health, and is better than a single adding groups.

Abstract:Twelve hundred and fifty individuals of were sampled from the coast of Zhaitang Island, Qingdao (using stow nets, in 2015), and their sex ratio, secondary sexual characteristics, gonadosomatic index (GSI), gonad maturity levels, egg diameter, and number of embryos in the pouch were examined. The results showed that the abundance of females was higher than that of males in the area, with a total sex ratio of 1.75:1, deviating significantly from a 1:1 sex ratio, and the sample comprised 63.28% females, 36.24% males, and 0.48% underage individuals. The gonadosomatic index (GSI) range in males in the breeding population was maintained at a relatively low level of 0.01% to 4.85%, and the GSI in females ranged from 0.05% to 128.99%, and was significantly different from that of the males (S. schlegeli quickly matured from March to May. After spermiation, some sperm cells remained in the testis of male , showing that multiple spermiation events may occur. In the female breeding groups, different phases of eggs appeared in the stage Ⅲ-VI ovary, and the egg-diameter distribution had two peaks, indicating a multiple-batch spawning pattern. The number of mature eggs in the stage V ovary was in accordance with the number of eggs in the paternal brood bags, and the embryos in the paternal brood bags were at the same stage, suggesting monogamous mating, or polygamy whereby males mated with multiple females on the same day. Evidence for the mating patterns of on the coast of Zhaitang Island needs to be shown by behavioral observation and microsatellite analysis.

Abstract:Mesopelagic fishes are a key component of oceanic ecosystems. Feeding rhythm is important for the study of energy flow and material cycles in food webs that include mesopelagic fish. In this study, we examined the feeding rhythm of based on trawl-survey data from October 2014, on the north slope of the South China Sea, and analyzing their feeding intensity. (1) The lengths of sampled ranged from 28 mm to 110 mm, concentrated in the range of 50 to 59 mm. There was no significant relationship between body length and feeding intensity ( started feeding at about 18:00 every day (rising together with zooplankton), finished feeding at about 05:30 the next morning (sinking with the zooplankton), and fed continuously during that period. The average feeding intensity of among five sampling times, ranged from 1.50 to 2.57, showing an increasing trend. (3) There was a significant difference in the feeding intensity of between evening, and night or early morning, reflected in the comparison of three periods, namely 18:30-19:30 and 01:00-02:00, 04:45-05:50, and 06:30-07:30 (=0.007 respectively). In addition, there was a highly significant difference ( between 03:30-04:30 and 04:45-05:50. (4) The percentage of feeding intensities of among 5 periods showed a wave trend, the fourth feeding-intensity percentage had the highest value at 06:30-07:30, the zero feeding intensity percentage had the highest value at 18:30-19:30, and was half of this value at 03:30-04:30, and then decreased continuously until 06:30-07:30. In general, showed continuous feeding and egestion from evening to the next morning, while feeding was concentrated during the morning. In conclusion, a mesopelagic fish species, fed on zooplankton from evening to the next morning, with habits of diel vertical migration and egestion from 01:00 till a certain time the next day. plays an important role in material and energy flow on the continental slope of the South China Sea.

Abstract:Measurement of fish target strength is one of the core components of fisheries hydroacoustics. Research focused on offshore fish in the South China Sea has not met the needs of fisheries-resource estimations. As a typical offshore fish, little is known about the target-strength characteristics of S. sihama, a Kirchoff ray-mode approximation was used to calculate the theoretical target strength of 19 samples and the morphological parameters, calculated using a model of the fish, were obtained using an X-ray machine (SOFTEX M-100) belonging to the South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences. The changes in patterns of target strength of with tilt angle were obtained by calculating programmatically at different frequencies. The empirical formulas of target strength of with body length were established for different frequencies and the distribution function of the tilt angle was produced using a data-fitting method, and compared with the conventional expression. The results show that the various patterns of target strength of with tilt angle at 70 kHz, 120 kHz, and 200 kHz, show multiple-peak-like distributions, and the variation of target strength with the tilt angle is more sensitive at higher frequencies. As the number of crests increased, the maximum target strength corresponding to the tilt angle increased. Maximum target strength of occurs between -15° and 5° at 70 kHz, and the maximum target strength appears between -10° to 0° at 120 kHz and 200 kHz. The position of maximum target strength occurred differently at each frequency. The varying characteristics of target strength of with body length changed under different frequencies and distribution functions of the tilt angle. When the angle function is (-5°, 15°), frequency is 120 kHz, and when the angle function is (0°, 10°), frequency is 200 kHz, the empirical formula and the conventional expression curve of target strength with body length coincide, the degree of fit is higher, and the conventional S. sihama. In other cases, there are some deviations in the two formulas, and the direct fitting parameter equation is more appropriate. The study confirms that the Kirchoff ray-mode approximation can reflect the target-strength characteristics of , providing a useful reference for the study of target strength of inshore fish in the South China Sea and a scientific basis for improving the accuracy and credibility of hydroacoustic assessment of fisheries resources.

Abstract:Based on survey data from fishery resources and on the ecological environment in the Jiaozhou Bay during 2015-2016 and 1980-1982, we constructed ecosystem models of Jiaozhou Bay for these two periods using Ecopath with Ecosim 6.5 software. The models of the Jiaozhou Bay consisted of 21 functional groups. Based on the two models, we compared and analyzed the differences in ecosystem structure, function, and attributes. The trophic structure of the Jiaozhou Bay ecosystem in 2015-2016 had changed, with a decrease in the proportion of top predator biomass and an increase in the proportion of R. philippinarum, and the mean trophic level of fishery catch had reduced. The energy flow of the Jiaozhou Bay ecosystem was mainly dominated by a grazing food chain, and the system-energy-transfer efficiencies increased from 15.83% in 1980-1982 to 16.35% in 2015-2016. Analysis of the keystones species for Jiaozhou bay ecosystem indicated that is a keystones species in both the 1980-1982 and 2015-2016 periods. Compared with the 1980s ecosystem, the scale of the Jiaozhou Bay system had increased and the net system production increased by 5 times by 2015. The parameters of the ratio of total primary production to total respiration increased from 1.267 in 1980-1982 to 2.518 in 2015-2016. In addition, the connectance index, system omnivory index, and Finn's cycling index decreased from the 1980s to 2015-2016. In conclusion, the maturity and stability of the Jiaozhou Bay ecosystem has been reduced over the past 30 years, and the system has shown a trend moving from a mature stage to an immature stage. In short, the Jiaozhou Bay ecosystem is currently in an unstable, young stage.

Abstract:Water temperature is an important factor affecting fish activities, and fish in stages such as breeding, growth, and development, have different demands in terms of water temperature. Based on survey data from four seasons in 2014 to 2015-using frequency and biomass approaches and the R language drawing technique-the water-temperature distribution characteristics of small yellow croaker () were analyzed and compared. The results show that the ranges of temperature distribution, determined using frequency and biomass, were obviously different, and the proportion of the former covers a relatively high proportion of survey stations, and the latter has a higher proportion of accumulated biomass. The latter is in the condition of ensuring a high biomass accumulation proportion, and can also have a higher proportion of station coverage in special seasons, such as summer and fall; based on the biomass to determine the temperature range can better reflect the distribution characteristics of target objects. Compared with the results of historical research, the water-temperature distribution range of this paper is basically consistent, and it is concluded that the water temperature distribution range of small yellow croaker is relatively stable. The results of this paper reflect the general characteristics of P. polyactis, and the distribution of temperature and space of the two groups was obviously different. One group was distributed northward, and the most southern distribution did not go beyond Zhoushan fishing ground; the other group was distributed southward, and the most northern distribution did not go beyond the Yangtze River-estuary fishing ground. The difference in the environmental characteristics of the population distributions can be used as a basis for population division. The results of this paper can be used as a side evidence for the division of . The results show that resource clustering in the spring and winter was higher than that in the summer and winter. The cold-season population structure was single, mainly the winter bait-chasing population, and the warm-season population structure complex, including spawning, recruitment, and other groups; the warm season appears multiple high biomass water temperature range, which may be related to different temperature preferences of the different groups.

Abstract:Species richness is the most fundamental concept of diversity. The observed number of species in surveys are commonly used to represent the species richness in marine areas, however, this approach may lead to certain underestimations due to observational errors. This study used the marine fish community in Southern Shandong Peninsula as an example to test methods for reducing errors in species richness estimation. Non-parametric methods, Chao, Jackknife1, Jackknife2 and Bootstrap, were used to estimate the number of species in the waters of Southern Shandong Peninsula, based on bottom-trawl survey data collected in October 2016. In addition, we examined the factors that can influence the performance of non-parametric methods. The results show that the number of species in the community, estimated by four non-parametric methods, showed remarkable variations:265, 248, 235 and 206 for Jackknife2, Chao, Jackknife1 and Bootstrap, respectively. In addition, the four methods also showed differences in standard deviation, and the standard deviation was the largest in Chao, followed by Jackknife, and was lowest in Bootstrap. The results of MDS showed that fish assemblages could be divided into two communities and the number of species have large differences. The estimated values in community I were 250, 238, 219 and 191; the number of species estimated in community Ⅱ were 86 and 100. Comparative studies show that the sampling intensity and number of species affect the estimation of non-parametric methods. This study provides a method reference and comparison criterion for the comparison of species richness with different sampling efforts.

Abstract:Energy accumulation is a vital index to indicate the level of reserve for organisms, especially for semelparous cephalopod species due to their short life-span and fast growth. In this study, using the mathematical methods and technology of energy-density determination, the relationship between body weight and mantle length, as well as the energy accumulation of somatic tissues including mantle, arms, and fins, were investigated for the jumbo squid, off Peru. The squid specimens were randomly sampled from the catch of a Chinese jigger fleet during the fishing season from June to August 2014, in the high sea off Peru (10°26°S-17°17°S, 79°17°W-82°39°W), and a total of 173 specimens were collected (107 females, 66 males). The results showed that the averages of both mantle length (ML) and body weight (BW) in female were (262.12±38.33) mm and (541.69±251.69) g respectively; while in males, the values were (251.37±31.90) mm ML and (449.78±179.99) g BW respectively. The effect of sex on the exponent "b" of the BW-ML relationship was significant, suggesting that there was a significant difference in the body growth between female and male individuals. The maximum energy density was detected in the mantle tissue for both female and male individuals, with an average of (20.56±1.12) kJ/g and (20.67±0.76) kJ/g respectively; followed by the arm tissue, with an average of (20.09±1.25) kJ/g and (19.95±0.87) kJ/g respectively. For the fin tissue, the energy density was detected at the minimum value, with an average of (19.92±1.05) kJ/g and (19.63±0.96) kJ/g for female and male individuals respectively. For the same somatic tissue, there was no statistical difference in the energy density between females and males (>0.05). The energy accumulated in different somatic tissues, however, was significantly different (<0.05), and the mantle tissue was showed the highest energy accumulation. In females, the percentage of energy accumulation was about 63.14%, 25.23%, and 11.63% for the mantle, arms, and fins respectively. In males, the percentages were about 65.89%, 22.91%, and 11.20% for the mantle, arms and fins respectively. Meanwhile, the energy accumulated in the soma of the mantle, arms, and fins significantly increased with body growth for both female and male individuals (<0.05), and the energy significantly increased along with the distribution from lower to higher latitudes (<0.05). These findings indicate that the process of energy accumulation in the somatic tissues of off Peru is the procedure for feeding and body growth.

Abstract:Based on the citation information provided by Institute of Scientific and Technical Information of China, the citation analysis was conducted on according to the citation data during 2013-2016. The results showed that there were 605 articles published by Journal of Fishery Sciences of China from 2013-2016, which were cited for 881 times, with a paper reference rate of 64.46% and an average cited frequency of 1.46 (times/article). A total of 4221 papers were cited before the deadline (December 31, 2016), and the total cited frequency was 7458 times. Among the core journals, other cited rate has maintained a high level of 90%, the immediacy index is basically kept at 13%, and the funded paper ratio is about 80%. Through the distribution of key words in the text, it is found that the hottest topic of research is "growth" (70 articles), following by "gene cloning" (44 articles) and "" (23 articles). During 2013 to 2016, there were 1463 first-authorscited on . Among those, the more highly cited papers respectively belong to the 7 research fields such as fishery resources and the sustainable development, fishery ecology and environment, aquatic genetic breeding, aquatic nutrition and feed, fish disease research, aquaculture technology and quality&safety of aquatic products processing. In addition, 20 senior authors, 20 institutions and 20 highly cited authors have been selected to provide the talent information reserve for periodicals. According to bibliometrics analysis, fisheries science research hot spots, core authors and institutions were efficiently explored, which provides support for the development of periodicals and references for researchers to understand the status of the subject.