• Volume 44,Issue 6,2020 Table of Contents
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    • Chromosome preparation and karyotype of the lined seahorse (Hippocampus erectus)

      2020, 44(6):907-914. DOI: 10.11964/jfc.20190911950

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      Abstract:Since the lined seahorse Hippocampus erectus was introduced into China in 2009, it has become the major aquacultured seahorse species in China. With the development of its aquaculture, the genetic quality of the species should be evaluated to provide fundament for artificial breeding study. The karyotype is varied among species, and is directly related to the genetic quality. Thus karyotype is the basis for identifying taxonomic status and study on phylogeny of a certain species. Study on karyotype would contribute to the studies on the genetic identification and community analysis. In order to explore the cytogenetical characters of the lined seahorse H. erectus, the metaphase chromosome was obtained from the dorsal fin of six-month old fish by colchicine incubation and hot air drying methods. Clear images of the chromosomes indicate the dorsal fin is an appropriate tissue for chromosomal investigation in seahorses. There were 22 pairs of chromosomes in diploid (i.e. n=22, and 2n=44). The karyotypes of both sexes were examined separately. There were significant differences in karyotype between males and females, male karyotype formula is 2n=2sm+20st+22t, and female karyotype formula is 2n=1m+2sm+20st+21t. Heterotypic sex chromosome was found in female H. erectus, so its sex chromosome belongs to ZW/ZZ type. The preparation of chromosome, karyotype and heterotypic sex chromosome in the lined seahorse were reported for the first time. The present study lays a good foundation for studies on cytogenetics, genetic breeding and protection of genetic resources of the lined seahorse.

    • Expression of MITF gene and its correlation with shell color in Crassostrea gigas

      2020, 44(6):915-923. DOI: 10.11964/jfc.20190611829

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      Abstract:In order to understand the expression of MITF gene and its association with shell color in the Pacific oyster Crassostrea gigas, we verified the four MITF genes in oyster, analyzed the sequence and compared with multiple sequences of other species. And the transcriptome of each stage of oyster development was analyzed. We also studied the mRNA expression in different tissues and mantle of black shell and white shell oysters. We found that three of the four MITF genes were pseudogenes, which were confirmed by transcriptome and RT-PCR, and the only expressed MITF gene in oyster encodes 448 amino acids. MITF protein is a hydrophilic and unstable protein and contains a N-terminal domain (MITF_TFEB_C_3_N superfamily) and HLH domain which is a highly conserved functional domain. Transcriptome analysis found that MITF was expressed at various stages of ontogeny of C. gigas, and the expression reached the highest level at the juvenile stage. The results of mRNA expression in tissues showed that the expression level of MITF in mantle was significantly higher than those in other tissues. The expression level of MITF in the adductor muscle of oysters with black shell was significantly lower than that of oysters with white shell. However, the expression level in the mantle of oysters with black shell was higher than that of oysters with white shell, but not significant. Both in black and white shell oysters, the expression of MITF gene in the outer edge of the mantel is significantly higher than in the inner edge. The results show that MITF gene of C. gigas might participate in the regulation of the melanin’s formation and the development of oysters at the early stage of oyster shell formation, and it might also regulate tyrosinase Tyr2 gene of oyster and participate in the formation of melanin in mantle and shell. This study lays a foundation for further study on the formation mechanism of shell color in oysters.

    • Effects of environment and feeding factors on the distribution of different body lengths of Sebastes schlegelii in the reef areas of Shandong Province

      2020, 44(6):924-935. DOI: 10.11964/jfc.20190511802

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      Abstract:In order to study the impact of environmental and feeding factors on the distribution of rockfish (Sebastes schlegelii) in artificial reef areas, this study used environmental and fishery data of three reef areas in Shandong Province from 2017 to 2018. Fish body length was divided into 10 groups by using the mean of the coefficient of variation, and the interval was 33 mm. Using Bray-Curtis similarity index to compare the similarity of the body length composition of rockfish in different regions, detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) were used to describe the effects of environmental factors on the S. schlegelii distribution of different body length groups; the composition of the food of S. schlegelii was detected by using the stomach contents analyses. The results showed that the body length composition similarity index of Xixiakou and Changdao artificial reef areas was 70.66%. Compared with Xixiakou and Changdao, the Qiansandao artificial reef area has a low similarity index with them, which is 54.94% and 59.46% respectively. The distribution of S. schlegelii with larger body type (299-365 mm) is more correlated with depth, WQI and chemical oxygen demand (COD), and it prefers to live in a deep, nutrient-rich environment. Small body type (35-200 mm) S. schlegelii prefers environment with shallow sea areas and good water quality. The older (2-3 years old) large body length (200-365 mm) S. schlegelii mainly consumes fish, shrimp and crabs, and the dominant bait is fish (IRI, %=65.94). Younger (0-1 year old) small body length (35-200 mm) individuals mainly feed on shrimp and crab, the dominant bait is shrimps (IRI, %=45.69). Consequently, the application of juvenile-fish-protection artificial reefs in shallow water can provide shelter for juvenile S. schlegelii; concentration on fishing in deep water can reduce the bycatch of juvenile S. schlegelii, and then their resources can be proliferated and protected.

    • Analysis of spatiotemporal fish density distribution and its influential factors based on generalized additive model (GAM) in the Yangtze River estuary

      2020, 44(6):936-946. DOI: 10.11964/jfc.20190911940

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      Abstract:Understanding the relationship between fisheries resources and environmental factors, and also the spatial and temporal distribution of fisheries resources, plays an important role in the process of making fishery management and protection strategies. Under the policy background of “the Yangtze River Great Protection”, carrying out such research has an important ecological significance for fisheries protection and recovery in the Yangtze estuary. Based on the survey data from 2006 to 2017 in the Yangtze estuary, relationship between fish density and environmental factors was stusied based on GAM, meanwhile, the seasonal distribution of fish density in 2017 was predicted. The results showed that explained deviance in the seasonal optimal model was 69.6%, 55.9%, 51.4% and 47.4% respectively, and the mean slope of regression line of 100-time cross validation ranged from 0.62 to 0.88. Salinity, water temperature and dissolved oxygen (DO) were found to be the significant environmental factors. In general, in spring, summer and autumn, salinity was considered to have a positive relationship with fish density. In summer, autumn and winter, water temperature was found to be the significant environmental factor, and in Autumn, a positive relationship was found. In spring, autumn and winter, DO was found to be the significant environmental factor, and in winter, a positive linear relationship was found. In 2017, there was a relativelg high value of fish density in summer. In the four seasons, relatively low value of fish density was found to exist in the natural extension waters of the southern branch of the Yangtze estuary. In the natural extension waters of Chongming Island to the sea, the fish density is relatively higher.

    • Discrimination of geographical population of jumbo flying squid (Dosidicus gigas) using the trace elements in the nuclear part of eye lenses

      2020, 44(6):947-958. DOI: 10.11964/jfc.20190411753

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      Abstract:To analyze the difference of trace elements in the nuclear part of eye lenses in different sea areas and test the performance of the microelements in the identification of geographical population of Dosidicus gigas, the research samples were taken from China’s ocean-going squid fishing boats in Ecuadorian, Peruvian and Chilean exclusive economic zones (EEZs) in the southeast Pacific Ocean in 2015 and 2017. The trace elements of eye lenses were determined to study as the population origin by applying the stepwise discriminant analysis, etc. The results showed that the trace elements in the nuclear part of eye lenses were significantly different among the three regions from the Ecuadorian, Peruvian and Chilean EEZs except for Al27 and Si29. The results of stepwise discrimination showed that the trace elements in the nuclear part of the eye lenses could be used to identify different geographical populations of D. gigas, and the overall discrimination success rate was 69.2%. The discrimination success rates of Ecuador, Peru and Chile were 87.0%, 70.0% and 52.0%, respectively. If the samples of the two regions from the Peruvian and Chilean EEZs were combined and then judged with Ecuador, the overall success rate rose to 89.7%, compared with 95.70% and 87.30% off the coast of Ecuador, Peru and Chile, respectively. Mg25 can be used to identify D. gigas from Ecuador with Peru and Chile, while Cu63 can identify Peruvian and Chilean. The high rate of mis-classification between Peru and Chile indicated that the two may belong to the “Southern Hemisphere” population, while Ecuador may be independent of the “Southern Hemisphere” and “Northern Hemisphere” populations due to different marine environments.

    • Forms and releasing flux of phosphorus in the surface sediments in Haizhou Bay marine ranching

      2020, 44(6):959-968. DOI: 10.11964/jfc.20180611337

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      Abstract:In order to understand the impact of Haizhou Bay marine ranching construction on the phosphate exchange at sediment-water interface, multiple surface sediments, overlying water and interstitial water samples were collected from the Haizhou Bay ocean ranch area in May 2017. The different forms of phosphorus were extracted by SMT (Standard Measurement Test), including exchangeable phosphorous (Ex-P), iron-aluminum bound phosphorous (Fe/Al-P), calcium-bound phosphate (Ca-P), then their amounts were determined. The phosphorus exchange flux at the sediment-water interface was estimated under the phosphorus flux simulation incubation experiment. The results showed that the contents of the total phosphorus (TP), inorganic phosphorus (IP) and Ca-P in the surface sediments of Haizhou Bay marine ranching ranged from 392.44 to 463.46 μg/g, 219.21 to 282 μg/g and 117.73 to 130.07 μg/g, respectively. The IP was found as the major form of phosphorus. The order of the contents of different forms of phosphorus was Ca-P> Ex-P> Fe/Al-P. The contents of phosphorus in the control area were greater than that in the reef area. The concentrations of various forms of phosphorus in the overlying water were higher than the sediment pore water. Laboratory phosphorus flux simulation experiments showed that the content of various forms of phosphorus in sediments were higher after the incubation process, and IP still the main form of phosphorus. The exchange fluxes of TP, TDP, and ${\rm{PO}}_4^{3 - }$ at the sediment-water interface were estimated at −0.53—−0.05 mmol/(m2·d), −0.15—−0.01 mmol/(m2·d) and −0.03—−0.29 mmol/(m2·d), respectively. The exchange rate was faster at the initial stage of the incubation experiment, and then tended to stabilize. Compared with the control area, the exchange flux of phosphate in the marine ranching was slightly greater, but both showed the tendency that phosphorus migrate from the overlying water to sediment. It suggests that phosphorus in surface sediments acts as a sink of overlying water. These results are expected to provide scientific basis for the reef construction and restoration projects of Haizhou Bay Marine Ranch.

    • Effects of inorganic carbon source on nitrogen reduction and sedimentation performance of bioflocs

      2020, 44(6):969-977. DOI: 10.11964/jfc.20190411719

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      Abstract:The ectopic biofloc reactor was used to compare the simulated carbon sources (NaHCO3) concentration of 0.0 g/L (control group), 0.5 g/L, 1.0 g/L and 1.5 g/L of simulated aquaculture wastewater which affected the nitrogen reduction and sedimentation performance of the bioflocs in two stages: organic carbon source existed (stage I for 21 d) and organic carbon source was missing (stage II for 21 d). The results showed that the effluent ammonia nitrogen concentration in the first-stage control group was significantly higher than that in the other treatment groups (P < 0.05), but generally decreased first and then stabilized. The nitrite nitrogen and nitrate nitrogen in each group accumulated a small amount; the biofloc biomass and sedimentation rate of the control group were significantly lower than the treatment groups (P < 0.05), and the difference between the treatment groups was not significant. There was no significant difference in the concentration of ammonia nitrogen and nitrite nitrogen in the effluent of each group in stage II (P > 0.05). The concentration of nitrate nitrogen in the control group was higher than that in treatment groups, and the concentration of ammonia nitrogen decreased rapidly. At this stage, the biomass and sedimentation rate of the bioflocs decreased, and the 1.0 g/L NaHCO3 treatment group showed better sedimentation effect; the particle size distribution also tends to be uniform. During the whole experimental period, the removal efficiency of ammonia nitrogen reached 97.8% and the nitrite nitrogen did not accumulate significantly at different concentrations of inorganic carbon source. The sedimentation rate and biomass of bioflocs in the treatment groups were significantly higher than those in the control group (P < 0.05). The results show that the addition of inorganic carbon source can improve the nitrogen reduction performance of bioflocs and enhance its sedimentation rate. After removing the organic carbon source, the biofloc reactor can maintain the ammonia nitrogen removal capacity, but caused nitrate nitrogen accumulation, and reduction of biofloc organisms. When the organic carbon source was missing, the inorganic carbon source (≥0.5 g/L) could help the biofloc reactor to maintain its ammonia nitrogen removal capacity.

    • Effects of salinity stress on immune-related parameters of the Nile tilapia (Oreochromis niloticus)

      2020, 44(6):978-986. DOI: 10.11964/jfc.20190911984

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      Abstract:In order to explore the effects of salinity stress on the immunity of the Nile tilapia (Oreochromis niloticus), we conducted acute and chronic salinity stress experiments on tilapia with body weight of (35±5) g and some immune-related parameters of the serum were tested. In acute salinity stress, the salinities of 0, 5 and 15 were set, and the enzyme activities of SOD, CAT, GSH-Px and AKP in serum were detected by sampling at 6, 12, 24, 48 and 96 h after stress respectively. In the chronic experiment, four salinity levels of 0, 10, 20 and 30 were set, and the enzyme activity of SOD, CAT, GSH-Px and AKP in serum was detected after 8 weeks of stress. The results showed that: SOD activity in serum increased with salinity at 6, 12 and 24 h under acute salinity stress, but at 96 h, enzyme activity in the salinity 15 group was significantly lower than that in 5 group. Under chronic salinity stress, the enzyme activity of each group decreased significantly with the increase of salinity. CAT activity in serum decreased significantly with the increase of salinity at 12 h and 24 h under acute salinity stress, and there was no significant difference after that. GSH-Px activity in serum decreased significantly with the increase of salinity at 6, 12 and 48 h after stress. AKP activity in serum significantly decreased with the increase of salinity at 6h after stress. Under chronic stress, the 20 group was significantly lower than the other groups. In the experiment of susceptibility to Streptococcus agalatiae after chronic stress, the susceptibility of the salinity 10 group to S. agalatiae had no obvious difference compared with 0, the susceptibility of 20 and 30 groups were higher than 0 group. This study showed that both kinds of stress could cause changes in immune-related indicators: acute salinity stress experiment showed that the salinities of 5 and 15 caused oxidative damage to the tilapia, but tilapia could gradually adapt to this change. Chronic salinity stress experiment showed that salinity above 20 could inhibit the activity of many immune indicators of tilapia, resulting in increased susceptibility to S. agalatiae.

    • Genetic parameter analyses of growth traits at 30 days post-hatching in bighead carp (Hypophthalmichthy nobilis)

      2020, 44(6):883-893. DOI: 10.11964/jfc.20190911986

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      Abstract:The aim of this study was to estimate the genetic improvement potential of early growth traits in bighead carp (Hypophthalmichthy nobilis). The practices of mass spawning (group 1) and artificial insemination (group 2) were carried out using two populations of H. nobilis, and 672 fries at 30 dph (days post-hatching) were collected from each group, that were used for the further analyses of early growth traits. Based on microsatellite markers, total of 628 and 660 individuals from group 1 and group 2, respectively, were assigned with unambiguous pedigrees and reconstructed with population diallel cross combinations. Extremely significant unequal parental contributions were detected in both groups. The extremely significant differences in BW (body weight) and SL (standard length) were detected among families in both groups, and the significant differences in BW and SL were detected among diallel cross combinations in group 2. Furthermore, the positive values in mid-parent heterosis (0.39%–7.64%) and special combining ability (SCA) (0.01–0.02) of two growth traits were detected in the hybridized combinations. Based on the animal model and restricted maximum likelihood (REML) algorithm, the heritability estimates of BW and SL in H. nobilis (30 dph) were calculated at 0.47 and 0.49, respectively. The extremely significant genetic and phenotypic correlations were found between BW and SL, with 0.89 and 0.83, respectively. The results indicated that the early growth traits of H. nobilis could be improved through family construction, cross breeding and selective breeding, but the unequal parental contribution should be taken into account in practical breeding programs.

    • Effects of replacing fish meal with defatted black soldier fly (Hermetia illucens) larvae meal on growth performance, nutrient retention, serum biochemical parameters and digestive enzymes activity of juvenile Pelteobagrus fulvidraco

      2020, 44(6):987-998. DOI: 10.11964/jfc.20190411736

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      Abstract:A 56-d feeding trial with 480 yellow catfish (Pelteobagrus fulvidraco) juveniles [(1.67±0.01) g initial body weight] was carried out to estimate the effect of replacing fish meal with defatted black soldier fly larvae meal (DBSFLM) on growth performance, nutrient retention, serum biochemical parameters and digestive enzymes activity of juvenile P. fulvidraco. Fish were randomly allocated into four isolipidic and isoprotein dietary treatments which were formulated by replacing 0 (T0), 20% (T20), 40% (T40) and 60% (T60) of fish meal (FM) protein with DBSFLM. Each treatment was randomly assigned to triplicate groups of 40 fish per aquarium. Fish were fed twice daily to apparent satiation. With increasing content of DBSFLM, the final body weight (FBW), weight gain rate (WGR) and specific growth rate (SGR) of yellow catfish increased first and then decreased. Growth performance of FBW, WGR and SGR in T20 were highest and higher than T60, whereas the feed conversion rate was the lowest. The feed intake in T20 and T60 was higher than that in control and T40 groups. With the increasing content of DBSFLM, the intraperitoneal fat index (IFI) was declining, T60 group was lower than control, and ash, calcium retention declining with T40 and T60 groups lower than control.There was no difference of condition factor, viscera index, hepatosomatic index, intestine index and gastric index among treatments. Nutrient retention such as protein,lipid and phosphorus, moisture, crude protein, lipid and ash in whole body were not affected by dietary treatments. Compared with control, the serum cholesterol and triglyceride were reduced and the high density/low density lipoprotein cholesterol increased in T20, T40 and T60 groups and pepsase and intestinal trypsin increased in T40 group. Results suggested that the growth performance and body composition of yellow catfish juveniles were not affected by dietary DBSFLM and the optimal alternative ratio was 20%, which was better than control. The replacement of fish meal with DBSFLM may reduce IFI, serum triglyceride, cholesterol and ash, calcium retention and increase protease activity.

    • Molecular characterization of two growth hormone receptor genes, and association analysis between microsatellite polymorphism and growth traits in the topmouth culter (Culter alburnus)

      2020, 44(6):894-906. DOI: 10.11964/jfc.20190211669

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      Abstract:To better study the structure and function of the growth hormone receptor (GHR) of the topmouth culter, Culter alburnus, the DNA sequences of GHR1 and GHR2 were cloned based on mRNA data from the transcriptome of C. alburnus. Bioinformatics analysis was performed and the polymorphic microsatellite loci in the GHRs were tested in 120 samples which were bred in the same batch and cultured in the same pond. The full length of GHR1 cDNA is 3 498 bp, with an open reading frame (ORF) of 1 818 bp, and a 605 amino acid residue encoded protein. The full length of GHR2 cDNA is 1 743 bp, and with an ORF of 1 743 bp, and a 580 amino acid residue encoded protein, the amino acid sequences of GHR1 and GHR2 both comprised a signal peptide, extracellular region, transmembrane region, and intracellular region, and are 37.2% similar. There were marked differences in their structures. GHR1 has seven cysteine residues in its extracellular region of GHR1, but GHR2 has only five. GHR1 has three N-glycosylation sites more than GHR2. In the intracellular domain, there are 10 tyrosine residues in GHR1, but only 5 in GHR2, indicating that the two proteins may have different biological functions. Homologous amino acid sequence alignment showed that the GHRs are highly conserved with GHRs from other Cyprinidae. There were both 9 introns in the GHRs of C. alburnus, the length of intron 1 and 2 in GHR1 is over 10 kb so that they were not amplified in this experiment. Six microsatellite loci were found in the obtained sequence: the microsatellite locus (CT)6 in the exon 2 of GHR1 was located in the signal sequence coding region, and no polymorphism of the (AC)5 in intron 8 was detected; there were four microsatellite loci in GHR2, including (TG)5 in intron 1, (TATC)5(AT)15(AC)11(AT)14(TG)6 and (TA)15 in intron 7, which belonged to highly polymorphic loci (PIC > 0.5). The (GAAG)5 microsatellite loci in intron 6 was moderately polymorphic (PIC = 0.463). The number of genotypes detected using two microsatellite loci in intron 7 was 50 and 61, respectively, which had good potential for individual identification. Correlation analysis indicated that the four polymorphic microsatellite loci were all closely related to the growth traits. The cloning and the characterization of microsatellites of GHR gene may provide a reference for further study of its biological function and molecular marker assisted breeding in C. alburnus.

    • Effect of proteolytic soybean meal in low-fish-meal-diet on growth performance and stress resistance of Litopenaeus vannamei

      2020, 44(6):999-1012. DOI: 10.11964/jfc.20190511796

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      Abstract:In order to explore how to reduce the amount of fish meal while maintaining the good growth performance and stress resistance of Litopenaeus vannamei, in this study, the basic diet containing 10% fish meal was added with 0% (A), 2.5% (B), 3.5% (C), 4.5% (D) and 5.5% (E) of proteolytic soybean meal (PSM) to produce five groups of isonitrogonous isoenergetic feed. L.vannamei juveniles with initial body weight of (0.45+0.02) g were fed for 8 weeks. Then the growth performance and stress resistance of L.vannamei were assessed. The results showed that the final body weight of shrimps in each experimental group ranged from 14.65 to 15.38 g/individual after 8-week culture experiment, and there were no significant differences in weight gain, survival rate and feed coefficient among the groups. The crude protein content of shrimp muscle in group A was significantly lower than those in other experimental groups. The crude fat contents of shrimp muscle in group C, D and E were significantly higher than that in group A. There was no significant differences in ash and moisture content among other groups. The activities of hepatopancreas protease, hepatopancreas amylase, hepatopancreas lipase, serum lysozyme and serum T-SOD in shrimp fed D and E diets were significantly higher than that in group A. The serum MDA content in group A was significantly higher thsan those in other groups. In the stress test of artificial acute infection with high dose Vibrio Parahaemolyticus, the cumulative mortality of shrimp in group A at 48 h and 60 h post Vibrio infection was significantly higher than that in group D. The expression levels of Toll receptor, immune deficiency (IMD) and Lysozyme were detected in shrimp gill tissues after artificial acute infection with low dose V.parahaemolyticus. The results showed that the peak values of Toll receptor, IMD and Lysozyme mRNA expression appeared in group C at 24 h post infection, group B at 42 h post infection and group D at 24 h post infection, respectively. To sum up: in the feed containing 10% fish meal, the effect of proteolytic soybean meal less than 5.5% on the growth performance of L.vannamei is not significant. The dietary proteolytic soybean meal could significantly increase the crude protein content and crude fat content in muscle and decrease the MDA content in shrimp serum. Under the experimental conditions, the dietary proteolytic soybean meal significantly changes the resistance of L.vannamei to Vibrio and the temporal and spatial expression of immune-related genes. Using 4.5% proteolytic soybean meal in feed containing 10% fish meal can obtain the best anti-Vibrio ability of cultured L.vannamei.

    • Isolation and identification of two new isolates of genotype II grass carp reovirus and comparision of their biological characteristics

      2020, 44(6):1013-1024. DOI: 10.11964/jfc.20190611846

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      Abstract:In order to study the virulence and biological characteristics of different isolates of grass carp reovirus (GCRV) type II, we researched two new isolates of genotype II GCRV, ZH180804 and CQ180701, which were isolated from diseased and healthy Ctenopharyngodon idella, respectively. The characteristics of cell culture, pathogenicity, genomic segment, gene sequence and phylogenetic differences of the two strains were compared and analyzed. The results showed that mortality rate of ZH180804 to C. idella and Gobiocypris rarus were 80%, 100%, and those of CQ180701 were 10%,0%, respectively. The data of mortality rate showed that ZH180804 is a virulent strain, and CQ180701 is a low virulent strain. Cell infection experiment showed the two isolates could proliferate in grass carp swim bladder cells (GSB), Gobiocypris rarus egg cells (GRE) and (G. rarus fin (GRF) cells, but did not cause cytopathic effect (CPE), and viral multiplication of ZH180804 strains was 1 000 times higher than that of CQ180701 strains. The banding patterns of two isolates in sodium dialkyl sulfate-polyacrylamide gelelectrophoresis (SDS-PAGE) were partially identical, but there were some differences between the segments of S7, S8, S9, S10 and S11. The sequence homology of the S7 and S11 genes between two viruses are 98% and 99%, respectively. Phylogenetic analysis indicated that isolates ZH180804 and CQ180701 belong to the same branch, and it means that they are very closely related. All results above indicate that two strains of GCRV type II isolated from diseased and healthy grass carp have more common characteristics, but their replication ability and pathogenicity are different.

    • Delayed influence of quality-determination-period emersion on the recovery of live scallop (Patinopecten yessoensis) re-immersed

      2020, 44(6):1025-1035. DOI: 10.11964/jfc.20190611832

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      Abstract:To explore the delayed influence of post-harvest treatment on the quality change of live scallops, the experiment was performed in two post-harvest stages, including a quality determination period (QDP) corresponding to on-board handling and post quality determination period (P-QDP) corresponding to land-based treatment. There were three chilled-emersing treatments of different duration during the QDP: 12 h(E12), 24 h(E24) and 48 h(E48). In the P-QDP scallops are re-immersed into sea water for 24 h (E12'nd E24'). The quality of live scallops was measured by mass loss rate, survival rate, pH, glycogen content, ATP and ATP-related compounds, AEC value and SOD activity. The results show that the quality of QDP scallops declined in different degrees: E48 presented a 100% mortality and the survival rate in 24 h was 100%. Glycogen content declined sharply from 18.95 (Initial) to 14.66 mg/g (12 h). The QDP had a delayed influence on live scallop in the P-QDP: all indicators show E12' and E24' can recover temporarily but the shelf-life of E12' is superior to E24'. The study shows that there is a quality determination period post-harvest during which the handling has delayed influence on the recovery of live scallop after re-immersing. The post-harvest scallops can be recovered and 12 h treatment in the QDP is helpful for recovery. If treatment conditions are effectively chosen during the QDP, live scallops would have better recovery after re-immersing, otherwise, if overstressed during the early post-harvest stage i.e. QDP, even if indicators are good by the end of the period, depletion would continue in the P-QDP, affecting vitality and shelf-life of live products.

    • Dynamic analysis of night fishing vessels in the Yellow Sea based on VIIRS-DNB data

      2020, 44(6):1036-1045. DOI: 10.11964/jfc.20190411759

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      Abstract:VIIRS/DNB satellite nighttime light image was used as the data source for studying the dynamics of fishery vessels. A total of 719 nighttime light images were recorded in the Yellow Sea in 2016. We designed a new method to extract the light point information of the nighttime operation vessels in the Yellow Sea. Analysis of the lighting points in combination with the China-Korea Fishery Agreement Area and the Yellow Sea area fishery division. The results show that the seasonal distribution change of fishery lights is significant, and the number of fishing boats in the four seasons shows the trend of autumn> spring> summer> winter. The number of light points is the largest in South Korea's waters, followed by China's side waters, and that in the waters in China and South Korea agreement zone is the smallest. Combined with the light point density map, the Korean side waters have higher intensity and wider distribution range in autumn, while other seasons have moderate intensity, and high-grade agglomeration areas are distributed in coastal waters all year round; the Chinese side waters have lower intensity in summer and winter, higher intensity in spring and autumn, and the overall intensity of the year is low but the distribution is broad. The number of light points in both sides has obvious seasonal patterns, and the proportion of light points decreased by 86.9% during the closed fishing season. Therefore, it is inferred that most of the light points identified in this study are fishery vessels, which can be used to provide reference for night fishing activities.

    • >ROUNDUPS
    • Research progress of the genetic diversity, origin and evolution of Carassius auratus in China

      2020, 44(6):1046-1062. DOI: 10.11964/jfc.20190811926

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      Abstract:Carassius auratus is the important aquaculture fish in China and has high economic value, which can be classified into two subspecies: C. auratus auratus and C. auratus gibelio. C. auratus has strong adaptability, primarily inhabits freshwater and is widely distributed with complex genetic background and different morphology and ploidy. At present, scholars have studied the genetic diversity, origin and evolution of different C. auratus with various methods. And there are big differences in research results, due to the differences of research methods, objects and standards. This paper summarizes the resourses and genetic diversity as well as the origin and evolution of C. auratus in China. We found that there exist abundant germplasm resources and genetic diversity of wild C. auratus in China, and the genetic variation of different local groups of wild C. auratus is great, which indicated a great breeding potential of them. The same gynogenetic clones show high genetic homogeneity, and various gynogenetic clones display abundant genetic diversity. The genetic diversity of goldfish bred according to human preference is much lower than that of wild C. auratus. The origin and evolution of C. auratus gibelio, C. auratus var. pengze, and other C. auratus and goldfish are also discussed in this paper. Although the origin of C. auratus gibelio is controversial, most of the results still support the perspective that “C. auratus gibelio and C. auratus belong to the same species, and triploid C. auratus gibelio is a population differentiated from C. auratus under special circumstances”. C. auratus var. pengze may be exotic fish of natural waters which escaped from the pond where the C. auratus gibelio is raised or originated from the wild C. auratus, which has obvious growth advantages and was selected for its obvious fine traits. Also, the discovery of different gynogenetic clones makes the genetic relationship between C. auratus var. pengze, C. auratus gibelio, and wild C. auratus more complicated, and further comparative study is needed. In most areas of China, there are a high likelihood of independent origins of the triploid wild C. auratus gibelio, and a lower possibility of spreading to other water systems after forming in one place. That doesn't rule it out that the early history of fish farming induced the invasion of some C. auratus geographic groups. Goldfish may originate from the wild C. auratus in the middle and lower reaches of the Yangtze river in China. It first evolved into grass goldfish, and then differentiated into fantail goldfish and dragon-eye goldfish. Yet as time passed and with artificial selection, fantail goldfish was further differentiated into bubble eye goldfish and dragon-eye goldfish was further differentiated into oval goldfish. Although there are many varieties of goldfish, but they belong to the same maternal origin from the perspective of mitochondrial genome. By reviewing the previous research aiming at C. auratus in China, this study analyzes and discusses the present situation of germplasm resources, existing problems and future research of C. auratus, and provides a basis for reasonable utilization and protection of C. auratus resources, and to promote the good and fast development of C. auratus industry.

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