Abstract:To study the effects of different origins of feed on growth, plasma biochemical indexes, antioxidant capacity, liver and intestinal histology of Micropterus salmoides, 180 largemouth basses[initial average weight (12.45±0.07) g] were randomly divided into 2 groups with three replicates at a stock density of 30, and commercial compound diet and fresh frozen Hypophthalmichthys molitrix were allocated to each of two groups of fish for a feeding period of 84 days. Results suggest that group with commercial compound diet behaves significantly lower than the other group on weight gain rate(WGR), specific growth rate (SGR) and feed conversion ratio (FCR), with the same conclusion on the liver protease activities. And the former performs higher than the latter on protein efficiency ratio (PER), hepatosomatic index (HSI) and viscerosomatic index (VSI) than the other group, similar to the hepatic glycogen contents. But significant difference disappeared in muscle glycogen and intestinal amylase activities between 2 groups. The AST activities, glucose (GLU) and MDA contents and Ca/P ratio of largemouth basses fed with commercial compound diet are significantly higher than those fed with fresh frozen trash fish group, but the activities of ALP, SOD, GSH-Px and the contents of TP, TG, UREA, Ca, P in plasma are significantly lower than fresh frozen trash fish group. No significant difference was observed in ALT, TC and insulin contents of plasma among all groups. The histological study showed that ultrastructure of the liver and the intestine in the commercial compound diet treatment were abnormal. Serious vacuolization in liver, the severe mechanical damage of intestinal villi were found in commercial compound diet group. The study, under given conditions, indicates that fresh frozen H. molitrix is more appropriate to feed M. salmoides compared with commercial compound diet. The latter not only affected the growth of largemouth bass but also did harm to the liver and intestine of largemouth bass. Therefore, feed formulation technology for largemouth bass could be further developed, referring to nutritional composition of fresh frozen H. molitrix and the metabolic properties.

Abstract:This study intends to explore the health and immunologly mechanism of fermented soybean meal replacing fish meal affecting the growth of the Litopenaeus vannamei based on varying immune-related enzymes activity and genes transcription levels. Five experiment diets were designed, in which 30% of fish meal diet (FM) as the control group, and 4% (FSM4), 8% (FSM8), 12% (FSM12) and 16% (FSM16) of the fermented soybean meal were used to replace 9.7%, 19.4%, 29.1% and 38.8% of the fish meal respectively. After 60-day feeding test for L. vannamei[initial weight=(7.62±0.23) g], the growth performance, muscle nutrition composition, serum and hepatopancreas immune enzymes activity, the expression levels of HSP70 mRNA in hepatopancreas and Toll receptor mRNA, IMD mRNA and LZM mRNA in gill were determined. The results indicated that the substitution of fermented soybean meal for fish meal had no significant effect on the survival rate of the shrimp compared with the control group, both too low and too high levels of fermented soybean meal reduced the specific growth rate of shrimp. Muscle crude protein content was lower in the addition group of fermented soybean meal than the FM group with no significant difference except FSM12, crude fat has a tendency to decrease with the increase of fermented soybean meal, and the lowest value was found in the FSM16 group. The serum alanine aminotransferase (ALT) in FSM4 and FSM16 groups was significantly higher than that of control group, and the aspartate amino transferase (AST) was the highest and lowest in FSM4 group and FSM8 group respectively; except FSM12 group, serum ALP showed no marked difference between other FSM groups and the control group; as for TP in serum and MDA in hepatopancreas, there was no statistic difference either between FSM groups (except FSM16 group) and the control. With the increase of the amount of fermented soybean meal, the level of gill Toll receptor mRNA expression increased, and the level of IMD mRNA expression increased first and then decreased, and excessive or less of the added fermented soybean meal would decrease the expression of LZM mRNA in gill, while the expression of HSP70 mRNA in hepatopancreas increased with the increase of fermented soybean meal. To sum up, in the conditions of this experiment, optimum amount of the fermented soybean meal was 8% to 12%, i.e replacing 19.4% –29.1% of fish meal without affecting the growth of the tested shrimp, accompanied by improved immune-enzyme activity and changed expression of immune related genes, however, too high substitution can cause excessive stress response.

Abstract:A study was conducted to evaluate the effect of the dietary inositol levels on growth, lipid metabolism and antioxidant activity of grass carp. Seven isonitrogenous (30.78% protein) and isolipidic (6.04% lipid) practical diets with graded levels of inositol (0, 50, 100, 150, 200, 300, 400 mg/kg) were fed to 25 juvenile fish averaging (15.00±0.15) g (mean±SE) in quadruplicate aquaria for 56 d. The results showed that the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR) and feed efficiency (FE) at dietary inositol levels of 100–150 mg/kg were significantly higher than those of other groups. With the increasing of inositol dietary level, the crude lipid contents of whole-body and liver and lipid deposition rate significantly increased when dietary inositol was 50-300 mg/kg, but the muscle lipid content of fish fed the 100 mg/kg inositol diet or higher was significantly lower than the control group and the group fed diet containing 50 mg/kg inositol. Intestinal lipase, plasma total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterin (LDL-C), high-density lipoprotein cholesterin (HDL-C) contents and high density/low density lipoprotein cholesterin (HDL-C/LDL-C) rose in first and then declined, and all reached the maximum at dietary inositol levels of 100–150 mg/kg, except the LDL-C content. Dietary inositol supplementation resulted in marked increase of carnitine palmityl tratnsferase-I (CPT-I) and acetylCOAcarboxylase (ACC) activities in liver and muscle. Compared with the control group, the growth rate of CPT-I in liver was lower than that of ACC, while the growth rate of CPT-I in muscle was higher than that of ACC. Significantly higher superoxide dismutase (SOD) activities in liver and muscle were obtained in fish fed 100–150 mg/kg than those fed the control, and lowest malondildehyde (MDA) concentration, transaminase (AST) and alanine transaminase (ALT) activities were also found in that. In conclusion, the appropriate dietary inositol supplementation to grass carp has an improving effect on growth performance and feed conversion efficiency, promotes the capacity on lipid digestion and the synthesis and degradation of tissue fatty acid, increases the crude lipid contents of whole-body and liver and decreases that in muscle, but improves antioxidant activity of liver and muscle. FE and SGR analyzed by broken-line regression indicated that the suitable inositol supplementation to practical dietary of grass carp is 90.3–96.4 mg/kg.

Abstract:Larimichthys crocea is the largest cultured marine fish species in annual production in China. It shows obvious sex-related dimorphism in growth, where females grow much faster than males. It is difficult to distinguish the gender of the L. crocea through morphological characters, and also it has no evolutionarily differential sex chromosome. Currently, examination of the gonads after dissection is the most reliable way to distinguish the phenotypic sex in this fish. Given that the traditional methods is unsuitable for the identification of phenotypic and genetic sex, it is then necessary to develop sex-specific molecular markers, which is indispensable in sex-control breeding and understanding the mechanism of sex determination in this species. In order to develop sex-specific markers, sequencing data of short-insert libraries of 2 females and 2 males (30×coverage) and a pool of 50 females and a pool of 50 males (50×coverage) were utilized in this study. In brief, the raw sequencing reads were cleaned by removing Illumina sequencing adapters, low-quality sequences. The cleaned reads were aligned to our custom genome assembly (ENA accession no.:PRJEB24300) of the large yellow croaker using BWA, and the genome-wide SNPs were further called. We detected that 11 SNPs (hereafter referred as SNP 1~11) demonstrated obvious difference in allele frequency between males and females through comparative genomic approach. We further genotyped the 11 SNPs in 15 females and 15 males by PCR and Sanger sequencing, and found SNP 5 and SNP 6 were homozygous in all females and heterozygous in all males, perfectly segregated between sexes. We then devised an allelic-specific PCR (AS-PCR) based on SNP 6 for amplifying one band (348 bp) in females and two bands (348 bp and 194 bp) in males, and genotyped near 2 200 L. crocea sampled from Fujian, Guangdong and Zhejiang province. The genotyping result showed that all females were with the 348 bp band and all males were with the extra 194 bp band besides the 348 bp band in the AS-PCR followed by electrophoresis assay, suggesting 100% accuracy of the method in sex identification. In conclusion, this study has detected and validated a male-specific (Y chromosome) SNP marker, and developed a simple method to identify the genetic sex for the large yellow croaker through the AS-PCR followed by electrophoresis assay. The finding provides an indispensible technical basis for sex-control breeding practice, genomic selection and the research on the molecular mechanism of sex determination in the L. crocea.

Abstract:Chromosome banding pattern study is a useful tool in exploring evolutionary mechanisms of fish because it provides basic information on the banding number, size and morphology of chromosomes. Up to now, there has been no report on chromosome banding patterns in fishes. In order to understand the morphological characteristics of chromosome banding pattern and germplasm resources of Seriola aureovittata, we injected phytohemagglutinin (PHA) and colchicine, collected all the head kidney cells of one-year-old fish artificially bred from wild broodstock along the Dalian coast of China. The chromosomal division phase was prepared by low osmotic treatment, Kano's liquid fixation, air drying and Giemsa staining. We used different methods to deal with these three patterns. We investigated the banding features and morphological characteristics of multiple chromosomes banding pattern (C-banding, G-banding and Ag-NORs). Results show that (1) All of the 48 chromosomes have C-banding. The C-banding of S. aureovittata were located mainly in the centromere regions of chromosomes. The 2nd, 4th, 5th, 16th, 18th and 19th pairs of chromosomes show positive C-banding in the terminal region. However, chromosomes do not show entire positive and middle C-banding. According to the length of the C- band, the amount of heterochromatin calculated is 31.53%. (2)The Ag-NORs polymorphisms were specific in this fish. The silver staining pots were 1-2 in interphase nucleus. The number of Ag-NORs was mostly 2. A pair of nucleolar organizer regions was found on the 5th pair of chromosomes in the terminal region. (3) The size and location of G-banding are same in homologous chromosomes, but they are not same in the non-homologous chromosomes. Every chromosome has different amounts of darkly stained and faintly stained bands. There is no entire chromosome showing darkly stained or faintly stained G-banding. The 24 pairs of chromosomes have different G-banding features in the quantity, size, location and depth of staining; Statistics showed that there were 118 G bands in the chromosome of S. aureovittata, including 70 positive bands and 48 negative bands. The study of banding pattern of chromosomes can be used to understand the law of genetic variation, genetic composition, development mechanism and genetic mechanism of sex. It also has important reference value for determining the number of the genome, the origin of the species, the relationship of each other, the status of evolution, and the classification of the organisms.

Abstract:Mytilus coruscus adults were challenged by Vibrio splendidus in three concentrations (1×10⁶ cell/mL, 1×10⁷ cell/mL, 1×10⁸ cell/mL). The changes of immune indexes including nitric oxide synthase (NOS), nitric oxide (NO), superoxide dismutase (SOD) and malondialdehyde (MAD), and digestive enzyme activities including amylase and protease in digestive gland were determined during 72 h experiment period. The activities of NOS in foot, gill and digestive gland were measured after experimental challenges of 48 h. Only the activity of NOS in the digestive gland was significantly different from the control group, and the activity of NOS increased with the increase of initial concentration of V. splebdidus. The activity of NOS of digestive gland in the treatment group was significantly higher than that of the control group after the challenge of V. splebdidu, and the level of NOS significantly increased after 48 h. The content of NO was significantly higher than that in the control group. The content of NO increased first and then decreased, which had a similar trend with the activity of NOS. The activity of SOD was significantly higher compared with that of the control group after the challenge of V. splebdidu. The content of MAD in the treatment group was significantly lower than that in the control group after the challenge of bacteria. The activity of amylase in the treatment group was significantly lower than that in the control group. The activity of amylase descended first and then increased. The change of protease activity in the treatment group increased first and then decreased. This study indicates that V. splebdidu can promote the immune indexes and protease activity and inhibit amylase activity. The present study provides useful information for clarifying the immune mechanism of M. coruscus and Vibrio-mussel interactions.

Abstract:In order to investigate the cause and prevention measure of skin-ulcer of Silurus soldatovi in Heilongjiang River, the pathogenic bacteria were isolated from the liver, spleen and kidney of diseased S. soldatovi with conventional methods. Artificial infection experiment was carried out to prove the pathogenicity of isolated strains. The morphological, biochemical, molecular and characteristics, virulence genes and antimicrobial resistance to bacteria were examined. The results indicated that 3 pathogenic strains were isolated from diseased fish, named NY-8, NY-9 and NY-12, respectively. Artificial infection showed that NY-8 and NY-9 were highly pathogenic to experimental fish while NY-12 strain was less virulent to fish. Co-infection of 3 strains caused 100% mortality of fish with the same clinical signs as the natural case. Combining the biochemical and molecular characteristics of 3 strains, NY-8, NY-9 and NY-12 were determined to be Aeromonas veronii, A. salmonicida and A. hydrophila, respectively. The three strains contained two virulence genotypes, including hly+/aer+/act+/alt+/GCAT+ and hly+/aer-/act+/alt+/GCAT+. The pathogenicity of NY-8 and NY-9 carrying all five virulence genes was significantly higher than that of NY-12. Antimicrobial susceptibility tests showed that there were some differences in drug resistance spectrum in 3 strains. NY-8 and NY-9 were sensitive to 4 kinds of fluoroquinolones and resistant to aminoglycoside and nitrofurans antibiotics, while NY-12 was only sensitive to levofloxacin and florfenicol.

Abstract:The aim of this study is to investigate the toxic effects of ammonia-N stress on the histopathological changes of liver, gill and brain in juvenile cuttlefish (Sepia pharaonis). The S. pharaonis, whose initial average weight was (13.80±0.65) g, were first exposed to ammonia-N for 96 hours and then the 96 hours median lethal concentration was obtained. In this study, we established a control group (0 mg/L) and four different ammonia nitrogen concentrations of 1, 3, 6, and 12 mg/L for the acute ammonia toxicity experiment according to preliminary experimental results, and each ammonia-N level was respectively sampled at 96 h. The liver, gill and brain tissues were observed by optical microscope and transmission electron microscope. The results showed that the severity of lesions clearly differed among organs with the liver showing the most extensive damages, followed in order by the gill and brain. And there was no damage to the brain tissue. The damages of liver and gill increased with increasing exposure concentration and time. It is found that the liver is bright red, swollen, and easily eroding from the 96 h after exposure to no less than 6 mg/L ammonia. Microscopical observation showed that the liver displayed hypertrophy of hepatocytes, nuclear hypertrophy, cellular peripheral nucleus, hepato cellular vacuolation, hydropic degeneration, necrosis, dilatation in sinusoids, cellular outline indistinguishable and cytolysis. The transmission electron microscope observation showed the hepatocyte nuclear crinkle deformation, the nucleolus disappearance, the mitochondrial crista disorder, the vacuolation and the outer chamber swelling, and the number of Golgi bodies decreased. Microscopical observation showed shedding epithelial cells from gill lamella, irregular array and some necrosis phenomenon, vessel of gill filaments was pycnosis or even became cavum, and branchial swelling and congestion. The transmission electron microscope observation showed gill epithelium and chloride nuclear membrane breakage, and nuclear cleavage, mitochondrion has crinkle deformation, vacuolization and incomplete breakage. While the brain tissue and the optic lobes were observed, there was no cell damage in the brain tissue.

Abstract:In order to detect the antigenicity of moonlighting protein FBA (fructose-1,6-bisphosphate aldolases), fba gene from Streptococcus iniae DX09 isolated from Ictalurus punctatus was cloned. The related properties of FBA protein were predicted and its immunization efficacy assay was conducted. rFBA protein was obtained by prokaryotic expression systems and purified by Ni-NTA-Sefinose Column. The purified rFBA protein was used to immunize rabbits (Oryctolagus cuniculus) to obtain the polyclonal rabbit anti-rFBA sera for antigenicity detection. The results showed that fba gene had an ORF with 882 bases, encoding 293 amino acids with a C₁₃₇₈H₂₁₇₂N₃₆₈O₄₂₂S₈ formula, 30.9 ku molecular mass, and a 5.01 theoretical isoelectric point. Furthermore, the deduced amino acids comprised phosphorylation sites, not containing the transmembrane domain and signal peptide sequence. The conserved domains, namely aldolase were predicted via NCBI conseverd domains tool. The comparative analysis revealed an exaggerated degree of homology with other S. iniae FBA protein in amino sequences. Additionally, high antigen index of the deduced amino acids was predicted using DNAstar-Protean, which means it can form numerous epitopes. rFBA proteins formed into inclusion bodies were found in the pellet and a band about 47 ku was observed by SDS-PAGE. Moreover, western blot analysis showed that rabbit anti-rFBA sera can combine with the mycoprotein specifically. Immunization efficacy assay suggested that rFBA prevented S. iniae DX09 infecting I. punctatus with a 55% protective rate. In this study, our results showed that rFBA possesses nice antigenicity and optimal immune protection, implying that the FBA protein can be a subunit vaccine candidate against S. iniae in I. punctatus.

Abstract:In order to assess the minerals values of five shell colors (black, purple, orange, golden and white) strains of Crassostrea gigas and one control population, the inductively coupled plasma atomic emission spectrometer and visible near-infrared reflectance spectroscopy were used to determine the minerals (Mg, Fe, Zn, Cu, Mn and Se) in different organs (mantle, gill, adductor muscle, and gonad-visceral mass). Results indicated that the purple shell, orange shell and black shell strains showed a significantly higher Zn content than that of control population (P<0.05), while the purple shell color strain had significantly higher Cu content than the golden shell color strain and control population (P<0.05), but the golden shell color strain showed a significantly higher Mn content compared with the purple shell and black shell color strains in the mantle (P<0.05). The golden shell color strain showed significantly higher Mn in gill than the black shell color strain and control population (P<0.05), whereas there was no significant difference in other minerals (P>0.05). In addition, the orange shell and purple shell color strains had significantly higher Zn content than the control population in adductor muscle (P<0.05). When considering the minerals in gonad-visceral mass, the orange shell color strain showed significantly higher Zn and Mn contents than the control population (P<0.05), and had significantly higher Cu content than the golden shell color strain (P<0.05). Mineral contents displayed significant difference among the four tissues. The contents of minerals in adductor muscle were significantly lower than those in mantle, gill and gonad-visceral mass (P<0.05). These results indicated that minerals significantly changed in the process of selective breeding, providing useful information for developing shell color strains in future.

Abstract:In order to study a mass culture method for photosynthetic bacteria Rhodopseudomonas, from January 5, 2015 to April 26, 2016, the freshwater compound fish feed with tap water was put in plexiglass columns in a greenhouse for fermentation, and neither other substances nor bacteria strain was added during the culture. During the experiment, with the decay of the feed, a kind of dark red substance gradually appeared on the inner wall of the container, and the attachment area gradually spread to the entire inner wall, and then the water body gradually turned to dark red. The results showed that the highest content of TN, TP and TOC in the water was nearly 1 200 mg/L, 700 mg/L and 2 700 mg/L, respectively, during the feed decay, and then they decreased. The high throughput sequencing analysis for the microorganisms showed Rhodopseudomonas was the most dominant genus in either the attached microorganisms or the planktonic microorganisms, and the relative abundance reached 73.19% and 54.31%, respectively, when the water was dark red. It showed that the high density culture of the attached or planktonic Rhodopseudomonas was achieved. The massive culture mechanism for Rhodopseudomonas in this experiment was deduced here:firstly, the compound fish feed was degraded into micromolecule substances with heterotrophic bacteria, followed by the concentration of nitrogen, phosphorus, carbon, metal ions, vitamins, trace elements and other micromolecule, which met the demand of the high density growth of Rhodopseudomonas with the conditions of appropriate water temperature, light and other physical factors, and then Rhodopseudomonas massively grew to become the dominant genus. This research provides a method for mass culture of Rhodopseudomonas with fermentation of aquatic compound feed and water, which also provides useful information for the large-scale culture of other heterotrophic bacteria that can biodegrade macromolecules.

Abstract:Anchoveta (Engraulis ringens) forms the largest production in the world's single species fishery. Therefore, study of the relationship between the Peruvian upwelling and E. ringens fishing ground could help understand the mechanisms about the formation of this fish's fishing ground. Therefore, Our study aims to summarize the regularity of the upwelling and temperature to the E. ringens fishing ground formation. In this study, we used the upwelling velocity (UV) as the index of Peruvian upwelling, and combined the temperature (T) and temperature anomaly (TA) data in the fishing ground from 2005 to 2009 to analyze their effects on the fishing ground which was indicated by the nominal catch per unit effort (CPUE). The results showed that UV, T and TA in the fishing ground was 1.42×10^-5-7.44×10^-5 m/s, 16.61~19.42℃ and 1.87-1.69℃, respectively. In addition, we used the generalized additive model (GAM) to analyze the influence of environmental factors on CPUE. The GAM could explain the changing trend of nominal CPUE as 67%. The optimum range for each environmental factor based on GAM was UV:less than 4.5×10^-5 m/s; T:18.4-19.5℃ and TA:-2-0.2℃. When UV was lower than 4.5×10^-5 m/s, the CPUE nearly remained the same with UV. However, when UV was higher than this value, the GAM showed the decreasing trend of CPUE. The studies suggested that the upwelling's impact to the E. ringens fishing ground was not following the pattern "the higher, the better". There was also optimum range of upwelling velocity for the fishing ground. the results indicated that the optimum sea surface wind, moderate upwelling and appropriate temperature condition were beneficial to the fishing ground formation.

Abstract:In order to investigate the function of AraC-family transcriptional factor AetY (U876_01475), we constructed the aetY deletion mutant strain ΔaetY using homologous recombination with Aeromonas hydrophila Chinese epidemic strain NJ-35 as a parental strain. The corresponding gene-complemented strain CΔaetY was also constructed. Biofilm formation ability, auto-aggregation activity, drug resistance to enrofloxacin and pathogenicity were detected in NJ-35, ΔaetY and CΔaetY strains. The inactivation of aetY caused a significant decrease in biofilm formation, auto-aggregation and MIC value for enrofloxacin. The virulence of ΔaetY to Danio rerio was significantly reduced, and the LD₅₀ value had an increase of more than 400 times. The above characteristics of CΔaetY were restored to the same level of the wide type strain. This study for the first time investigated the function of AraC-family transcriptional factor AetY in A. hydrophila, which will provide a basis for further exploration of AetY role in pathogenic mechanism.

Abstract:Marine fisheries provide a major source of food and livelihoods for people worldwide. Fishery management plays an important role in achieving sustainable fisheries. Catch per unit effort (CPUE) data from either fishery independent or -dependent surveys are the most informative for variations in population size over time, meanwhile catches from the fishery-dependent survey are also required to assess fishing. If these data are inaccurate, the statistical analyses would be biased, leading to mismanagement of fishery resources. However, systematic distortions appeared in world fisheries catch trends. Moreover, due to lack of fishery scientific investigation, CPUE data were mainly from commercial fishing, and influenced by spatial-temporal factors, environmental factors and also spatial autocorrelation problem. Therefore, it is important to understand the impacts of distorted fishery data on stock assessments. This study used catch and CPUE data of the albacore (Thunnus alalunga) fishery in the South Atlantic. Simulations were conducted to estimate biological reference points (BRPs), i.e., maximum sustainable yield (MSY), B_MSY, F_MSY, B₂₀₁₁/B_MSY, and F₂₀₁₁/F_MSY using non-equilibrium surplus production models based on ASPIC (ASM) and Bayesian state-space modelling (BSM). Simulations were conducted under the following scenarios:① both catch and CPUE data are accurate; ② only catch data is misreporting; ③ only CPUE data is misreporting, and ④ both catch and CPUE data are misreporting. Five levels (coefficient of variation, CV=1%, 5%, 10%, 20%, and 30%) of stochastic errors were superimposed on catch and CPUE data. The estimated MSYs were 2.866×10⁴ t and 2.836×10⁴ t, B₂₀₁₁/B_MSY were 1.366 and 1.324, F₂₀₁₁/F_MSY were 0.627 and 0.667 by ASM and BSM, respectively, for the first scenario. Larger B_MSY (31.48×10⁴ t) and smaller F_MSY (0.091) were obtained by ASM. These results indicate that this fishery was in a good condition in 2011. Overestimate B_MSY and underestimate F_MSY were obtained using distorted catch and CPUE data by ASM, and distorted CPUE data made more impact than distorted catch data. Absolute percentage bias of estimated BRPs by BSM had a tendency to increase with the stochastic error increasing, and smaller than those by ASM, especially B_MSY and F_MSY. BSM can deal with the stochastic errors better than ASM. Therefore, BSM is suggested to be applied in fishery stock assessment when the fishery data include stochastic error.

Abstract:The optimal proliferation condition of Siniperca chuatsi rhabdovirus (SCRV) in CPB cells was determined through detecting the viral copy numbers by Real-Time Reverse Transcription PCR (qRT-PCR). Two inoculation methods including synchronous and asynchronous inoculation and different culture conditions such as the amount of inoculated virus, FBS concentration of the culture medium were investigated in this study. The virus was harvested when the CPE reached 80% and then RNA was extracted for qRT-PCR detection. Results showed that all the above factors had obvious influence on the SCRV proliferation in vitro. When compared with the viral yields in unit volume, asynchronous inoculation method was superior to the synchronous inoculation. The highest amount of virus (5.59×10¹⁰ copies/mL) were obtained when cultured in L-15 medium containing 2% fetal bovine serum at 28℃ for 48 h with MOI=10 and inoculation for 1.5 h. While the viral yields with unit cost was compared, 4 proliferation conditions with synchronous inoculation method were singled out which were superior to asynchronous inoculation. The highest viral yields per unit cost (4.88×10¹³ copies/yuan) were obtained when SCRV was inoculated to the CPB cells at the middle-log phase with a MOI=0.03 and cultured with L-15 medium containing 6% fetal bovine serum and harvested after culturing at 28° C for 70 h. In conclusion, viral yield and the medium cost were studied as the assessment criteria for SCRV proliferation in CPB cells in this paper, and it provided the theoretical basis for SCRV vaccine production with low cost through the comprehensive viral yield analysis of the medium cost.

Abstract:In order to solve the problems in the alginate production process of low-viscosity and ultra-low-viscosity, in this study, we degraded Laminaria japonica (cultivated in Qingdao, Shandong) with align lyase to produce low-viscosity and ultra-low-viscosity aliginate and investigated the effects of molecular weight, pH and temperature on viscosity, then the optimum conditions for alkali digestion were determined. On this basis, we studied the effects of enzyme dosage, enzymolysis time and initial viscosity of raw materials on alginate products. The results showed that the low-viscosity and ultra-low-viscosity alginate can be obtained within 30 min. of enzymatic hydrolysis when the amount of enzyme was controlled within the range of 100~500 U/g, which the low-viscosity alginate can be obtained when the amount of enzyme was 100~330 U/g and the ultra-low-viscosity alginate can be obtained when the amount of enzyme was increased to 330~500 U/g. Meanwhile we found that the enzymatic hydrolysis of alginate samples was with high uniformity of molecular weight, and the water saving rate was as high as 10%~50% during the technology process. At the same time, it was found that the viscosity of the hydrolyzed sample was not correlated with the initial viscosity of the raw material, so the process had extensive applicability of the raw materials.

Abstract:Based on the data collected from the bottom trawl survey and environmental investigation in November 2014 and May 2015, this paper studied the community structure of fish assemblage and its relationships with 6 major environmental factors in Sanmen bay. The results show, a total of 33 fish species were captured, species composition was dominated by seasonal migratory species, the settling species played a leading role in biomass, and the species were mainly composed of warm water fishes. There were 5 kinds of dominant species in autumn and spring, Collichthys lucidus, Harpodon nehereus, Trypauchen vagina were the common dominant species; NMDS and ANOSIM analysis revealed that the survey stations could be divided into 2 groups, of which one group was mainly distributed on the inside of the bay and the other one was mainly in the estuary; Significant difference was detected between the different stations in each season; The size spectrum analysis showed that the slope and intercept of fish community structure have obvious seasonal differences in Sanmen bay. RDA analysis showed that the fish communities structure was dominated by environmental factors such as temperature, dissolved oxygen, suspended matter and pH.

Abstract:Fish sauce is a widely used seafood condiment in East and Southeast Asia. Fresh fish or shrimp is generally used as raw material, and mixed with a lot of salt (usually 20%-30%), and then produced by long-term fermentation in an open environment. Fish sauce is characterized by delicious taste, nutrient-rich and so on. There are some problems of traditional fish sauce such as too long fermentation time, bio-amine accumulation, product quality inconsistencies and so on, however, the use of specific microbial starters is expected to solve these problems. On the basis of summarizing the traditional fish sauce production process, this paper focused on the enzyme-producing microbial species in traditional fish sauce, as well as researches and applications of using microorganisms to promote fish sauce fermentation and improve the quality of fish sauce products.

Abstract:A large number of natural lakes have experienced severe disturbances of the enclosure aquaculture for fish farming purposes. Nevertheless, the impacts of the enclosure aquaculture on fish fauna are still largely unknown. We hence evaluated the impacts of enclosure aquaculture on fish communities based on seasonal fishery survey in enclosure (EA) and non-enclosure aquaculture area (NEA) in the Huayanghe Lake in 2016. A total of 46 (belonging to 6 orders, 12 families, 35 genera) and 57 fish species (belonging to 6 orders, 11families, 40 genera) were collected in EA and NEA, with dominant Cyprinidae accounting for 65.22% and 63.16% of the total respectively. The dominant species in NEA were Hemiculter leucisculu and Coilia brachygnathus while Hypophthalmichthys molitrix and Aristichthys nobilis were dominant in EA. The percentage of riverine species in EA declined from 21.05% to 15.22% compared with NEA. The Richness index, fish density and the Margalef's diversity index were significantly lower, whereas the Pielou's diversity index were significantly higher in EA than in NEA. The fish fauna differences between EA and NEA were determined by the abundance of Coilia brachygnathus, H. leucisculus, Cyprinus carpio, Neosalanx tangkahkeii, Carassius auratus, Hemirhamphus kurumeus, H. molitrix and A. nobilis.