Abstract:Nile tilapia (Oreochromis niloticus) is an important economic fish species and has been farmed widely in south China. In order to study the inhibitory effect of EGCG on the degradation of myofibrillar protein in tilapia, the tilapia muscle was treated with EGCG with the concentrations of 0.002 5%, 0.01%, 0.02% and 0.03% respectively. The effects of different concentrations of EGCG on the myofibrillar protein salt solubility of tilapia muscle were investigated during storage. In addition, the targeted proteins of degradation inhibited by EGCG were studied by SDS-PAGE gel electrophoresis and mass spectrometry. The results showed that all of the different concentrations of EGCG had inhibitory effects on myofibrillar degradation, especially when the concentration of EGCG was 0.01%, the myofibrillar protein content was decreased from (82.42±0.65) mg/g on day 0 to (51.89±0.68) mg/g on day 12 (37.0% of descent rate), while the myofibrillar protein content of control group was decreased from (80.86±1.18) mg/g to (35.33±1.16) mg/g (56.3% of descent rate). The results of SDS-PAGE gel electrophoresis and mass spectrometry identification showed that targeted proteins of degradation inhibited by EGCGE were MHC, MLC and actin, respectively. The results of this study have some guiding significance for the preservation research of O. niloticus.

Abstract:Experimental ecological method was used to examine the changes in the distance moved per unit time and in the body surface area of the sea cucumber Apostichopus japonicus[with a body weight of (39.35±0.40)g] after they were shifted to an environment with a temperature of 15℃ and a DO concentration of 1 mg/L. The median lethal time (LT₅₀) of A. japonicus cucumber of two sizes[large-size:with a body weight of (32.70±4.46) g; small-size:with a body weight of (10.31±2.03) g] under hypoxia (1 mg/L) and three different temperatures (15℃, 20℃ and 25℃, with 15℃ as the optimum temperature) was also investigated. The diurnal metabolism in the A. japonicus of two sizes at different temperature (15℃, 20℃ and 25℃) and different DO levels[1, 3 and 6.5 mg/L (normoxia)] were also investigated to evaluate the effect of temperature and dissolved oxygen on the survival, metabolism and athletic ability of A. japonicus. The results showed that first, when they were placed at a temperature of 15℃ and a DO concentration of 1 mg/L, the movement speed of A. japonicus was decreased gradually and finally all died at 72 h. The body surface area of A. japonicus increased first and then declined, and during the whole hypoxia period, the body of sea cucumber was elongated, higher than those in the control group. At the DO concentration of 1 mg/L, the LT₅₀ for the large and small-size A. japonicus was 54.0 h and 44.7 h, respectively, at the temperature of 15℃, higher than those at the temperature of 20℃ (48.9 h and 39.3 h, respectively) and those at the temperature of 25℃, (33.4 h and 28.9 h, respectively). The tolerance to low oxygen in the large-size A. japonicus was higher than the small-size one. Compared with those at the temperature of 20℃ and 25℃, the two sizes of A. japonicus at the temperature of 15℃ were the most active at three DO levels. But compared with those at 15℃ and normoxia, the metabolic intensity of A. japonicus was also restrained at the DO concentration of 1 mg/L. Our analysis has shown that under hypoxia stress, A. japonicus might employ some strategy such as elongating body to increase the body surface area to increase O₂ intake, decreasing movement speed and reducing metabolic intensity to cope with hypoxia and hence the survival time was prolonged.

Abstract:The jumbo squid Dosidicus gigas is widely distributed throughout the Eastern Pacific Ocean.It is most abundant in Peruvian waters. D. gigas is now one of the most important target species in Chinese squid jigging fishery. In addition, D. gigas whose trophic level is in the middle of the food chain plays an important role in marine ecosystem, as both a predator and prey. In this study, the research on population structure, age, growth, reproduction habit, feeding ecology and migration path of D. gigas was reviewed. The fisheries biology, the trend of the relevant studies and the latest research progress were comprehensively summarized. We also discussed the issues of previous researches and proposed the future research directions, which includes more effective methods for age validation, amino acid stable isotope analysis for foraging ecology and a synthetic method consisting of mark-recapture, electronic tag, and natural marker for migration path. Meanwhile, the migration routes of D. gigas in the Eastern Pacific Ocean were plotted by analyzing and concluding the results of previous studies. This study will provide the basis for the rational exploitation and utilization and scientific management of D. gigas.

Abstract:There is one of the main areas of Chinese purse seine in the Central Equatorial Pacific Ocean. The fishing efforts for the free school fish stocks will be the trend of purse seine. To understand the environmental factors, which would affect the distribution of free school stock, is becoming more and more important. The free school stock is harder to catch than other types of fish, and the rate of failing sets is very high. This paper replaces the Catch per unit effort(CPUE)with the spatial points density as the index of stock abundance. The density of spatial points is treated as response variable, and we try to find out some significant variables from environmental factors based on the logbooks of Chinese Purse Seine fleets in 2015. Some factors are obtained as independent variables based on our experience or research articles, these variables are respectively:the distance to land (DIS), sea surface temperature (SST), net primary production (NPP) and mixed layer depth (MLD). First, the nonparametric estimate to these factors are calculated from relative covariate intensity function (rhohat) method. Second, using point process model (ppm) function of these factors, the intensity regression equation is given. The results show that:(1) The favorite environmental range of these variables, are 70-250 km in DIS, are 29.7-30.1℃ in SST, are 200-280 mg C/(m²·d) in NPP, and are 35.5-42 m in MLD, respectively. (2) There are positive relationships between the free school stock abundance with DIS within 0-70 km, SST within 28.5-29.8℃, NPP within 150-280 mg C/(m²·d), and MLD within 30-37 m, while there are negative relationships between the free school stock abundance with DIS above 250 km, NPP above 280 mg C/(m²·d), MLD above 37 m. And there are a random relationship between the free school stock abundance with SST above 30.2℃. (3)We get the optimal free school stock abundance regression equation of these factors through stepwise regression based on the AIC method. Among the environment factors that influenced the free school stock abundance, the order of importance factor is DIS>NPP>MLD>SST.

Abstract:Based on the mathematical simulation results of thermal discharge diffusion and the data taken from fishery resources surveying of the adjacent sea areas of Qinshan Nuclear Power Plant during spring (May,2010), summer (Sept.,2010) and winter (Dec.,2009), we divided the fish community distribution through cluster analysis method, explored and analyzed the effects of thermal discharge from Qinshan Nuclear Power Plant on fish community distribution of the adjacent sea areas,from the aspects of spatial distribution and species composition, species number and diversity of different communities, etc. The result showed that the adjacent sea areas of thermal discharge of Qinshan Nuclear Power Plant were divided into two communities in spring, summer and winter, namely:the sea areas affected by thermal discharge (i.e. community I, hereinafter referred to as the inside; located near the outlet of Qinshan Nuclear Power Plant, thermal discharged into the water made water temperature rise, the water temperature decreased outward diffusion) and the sea areas outside of the thermal discharge (i.e. community Ⅱ, hereinafter referred to as the outside). Differences of fish community structure showed differences of the characteristics of fish species quantity and diversity index were consistent in spring and summer, the outside was higher than inside, quantity density had a large difference, and the differences were significant in summer and winter, showing distinct characteristics. The quantity of fish species outside (14 kinds) > inside (6 kinds) in spring, the average value of individuals and weight diversity index (H_n') was similar, outside (2.30 and 1.93) > inside (1.76 and 1.56), quantity density had large difference, individual density outside (1.95×10³ ind/km) > inside (0.88×10³ ind/km), and weight density inside (6.14 kg/km²) > outside(2.26 kg/km²), mainly related to thermal discharge in spring affected fish spawning, fish assembled inside and had higher weight; similar to spring, in summer, the quantity of fish species, individuals and weight diversity index, individuals and weight density were all outside(11 kinds, 1.76, 1.92, 2.57×10³ ind/km and 9.06 kg/km²) > inside(9 kinds, 1.75, 1.65, 1.98×10³ ind/km and 3.67 kg/km²), mainly because the temperature of the sea water in summer was higher, thermal discharge into the sea water changed the characteristics of fish community inside, showed inside was lower than outside; and the winter was opposite to summer, all indicators were inside(15 kinds, 1.61, 1.86, 1.09×10³ ind/km and 8.64 kg/km²) > outside(7 kinds, 1.24, 1.13, 0.84×10³ ind/km and 4.72 kg/km²), mainly because the temperature of the sea water in winter was lower, probably related to thermal discharge making the proximal sea regions warmer than the surrounding sea waters, which could benefit the fish assemblies in winter because of a warm pool effect. Thermal discharge has different effects on fishes with different adaptabilities to temperature; some warm temperature fishes can be adapted to relatively low temperature, so the quantity of warm temperate fish species and fish species (8 kinds and 15 kinds) in the adjacent sea areas of thermal discharge were all the highest in winter among the three seasons, which was related to species distributed densely in the hot thermal discharge plume areas, thus formed the phenomenon that fish species in the adjacent sea areas of thermal discharge had more kinds than other communities.

Abstract:Based on the data collected from seasonal comprehensive surveys of the marine ecosystem in Pishan waters, the middle of Zhejiang Province in November, 2015 and in February, May, and August, 2016, the crab community characteristics such as species composition, dominance species and diversity were studied. The similarity of community structure and the relation between community structure and hydrological environment factors were analyzed. A total of 19 crab species were identified, which belonged to 9 genera in 6 families. The dominant species were Portunus trituberculatus, Charybdis japonica, C. bimaculata and Eucrate crenata. The composition of crab species and dominant species showed clear seasonal changes. The number of crab species in summer was the greatest and the least was in winter. The distribution of crab species at various depth of water showed the following trend. The species at 5-10 m and 10-15 m depth of waters was major, the water depth of less than 5 m and 15-20 m was minor. The diversity index of summer showed high range of variaton, the diversity index of winter showed lower values of variation. Diversity index of crab at the 10-15 m depth was higher, the 5-10 m depth of waters was lower. Based on redundancy analysis, surface water temperature, surface and bottom salinity were the most important environmental factors affecting the change of the crab species composition and community structure characteristics.

Abstract:The alternative cost method and opportunity cost method were used to evaluate the value of ecological services provided by seaweed aquaculture based on the study of seaweed farming in Zhejiang Province and Jiangsu Province from 2005 to 2014. The results showed that the value of direct ecological services mainly included three factors:the value of carbon capture, the value of eutrophication regulation and the value of heavy metal removal. The value of indirect ecological services included the value of avoided transformed forest land, avoided use of water resources, avoided use of fertilizer and avoided use of pesticide. In 2014, the values of three seaweed aquaculture direct ecological services are 0.41 million RMB, 1.97 million RMB, 0.61 million RMB for Zhejiang Province and 0.26 million RMB, 1.24 million RMB and 0.38 million RMB for Jiangsu Province, respectively; the value of four indirect ecological services are 464.87 million RMB, 11.61 million RMB, 3.09 million RMB and 11.77 million RMB for Zhejiang Province and 293.22 million RMB, 7.32 million RMB, 1.95 million RMB and 7.42 million RMB for Jiangsu Province. The total value of ecological services of seaweed aquaculture is far greater than the direct economic value of seaweed. The vast area of coastline indicates that seaweed farming has great potential for development, and the promotion of seaweed farming can not only be a solution to address the arable land and food crisis, but also has a positive effect on reducing carbon emissions, reducing nutrient pollution and coping with global changes.

Abstract:The estimation of the abundance of Chinese sturgeon, Acipenser sinensis, is of great significance to its conservation and the assessment of the ecological impact of hydropower construction. Based on its age-structure of the historical fishing data in the Yangtze River, we calculated the age-specific proportion of the adults, and then constructed an age-structured population model to estimate the abundance dynamics of A. sinensis, including the population sizes in the Yangtze River and the sea. Under the steady-state condition (prior to the Gezhouba river closure), we calculated that the amount of effective recruitment was 1 882 individuals every year, and the total number of the adult A. sinensis (female:13-34 year old, male:8-27 year old) was 32 260 individuals, with 15 310 of the male and 16 950 of the female. The numbers of adults in the Yangtze River (1 727 individuals) was 5% of the total in the Yangtze River and the sea. Using the sex ratio and old cohort proportion of historical fishing data, we estimated that the remnant spawning capacity of A. sinensis was only 6.5% after the river closure of the Gezhouba Dam, and 68%-80% of the old cohort was obstructed by Gezhouba Dam in the upper river. Then we estimated the dynamics of A. sinensis in the Yangtze River or/and the sea after 1981. The results show that after the river closure of Gezhouba Dam, the number of spawners in Yangtze River increased with the decrease of harvest number, and reached its peak in 1990 (about 2 200), then decreased rapidly, and was about 170 in 2010. The reduction of the spawning ground environmental capacity after the river closure of Gezhouba Dam was one of the reasons for the sharp decline of population size of A. sinensis.

Abstract:In the present study, brain aromatase gene (cyp19a1b) was cloned by using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA 5' and 3' ends (RACE) in Qihe crucian carp (Carassius auratus). We also examined the expression level of cyp19a1b in different development stages and different tissues by real-time PCR, and at the same time, expression profile of cyp19a1b after hCG injection and sex reversal induced by Letrozole treatment was also examined. The results showed that the full-length cDNA of cyp19a1b was 2 894 bp, including a 132 bp 5'-untranslated region (UTR), a 1 319 bp 3'UTR, and a 1 533 bp open reading frame (ORF) encoding a deduced protein with 510 amino acids. Sequence analysis revealed that Cyp19a1b from C. auratus showed the highest amino acid similarity with Cyprinidae fish, while has low similarity with other vertebrates include mammalian and reptiles. Tissue distribution by real-time PCR revealed that cyp19a1b was abundantly expressed in the brain, while barely detectable in other tissues. The expression of cyp19a1b was gradually upregulated from blastula stage, and peaked at neurula stage, then declined during the embryonic development stage. Ontogenic analysis demonstrated that cyp19a1b was expressed abundantly from 30 days after hatching (dah) in the brain, but kept a low level in the trunks. However, cyp19a1b decreased in the brain of sex-reversed males by Letrozole treatment. Intraperitoneal injection of human chorionic gonadotropin experiments showed that expression of cyp19a1b was significantly elevated at 8 h and persisted until 24 h after injection in the brain. These results suggested that cyp19a1b might be involved in the course of nervous system formation, gonad development and sex determination in C. auratus.

Abstract:To evaluate the genetic diversity and population structure in two generations of selected populations after using selective breeding, we carried out the genetic analysis in four wild populations (Hanjiang, Jiujiang, Shishou, Wujiang) and two selected populations (F₁ and F₂) of Ctenopharyngodon idella using a multiplex microsatellite PCR method. The results showed that the genetic variations of six C. idella populations were relative high and the genetic diversity parameters of two selected populations lower than wild populations except for average number of alleles (N_a). The Hardy-Weinberg equilibrium results showed that 62 loci of the 120 population-locus combinations deviated significantly from the Hardy-Weinberg equilibrium. The F_is of 51 loci were positive value while the others were negative in the 62 population-loci combinations. The AMOVA analysis showed that 3.75% of the variation were among populations, and 96.25% of that were within populations. The overall genetic differentiation index (F_st) was 0.038. The F_st analysis showed that the F_st values between the Shishou population, F₁ population and F₂ population were higher than 0.05, which were moderately differentiated. There was lower differentiation among the remaining populations. The F_st between F₂ population and four wild populations were higher than those between F₁ population and four wild populations. The Nei's genetic distance (D_n) results showed that the D_n values between two selected populations and four wild populations were higher than those among four wild populations. The UPGMA phylogenetic tree based on Nei's genetic distance showed genetic relationships between selected populations and wild populations were farther than those among four wild populations. The above results showed that the genetic diversity of two selected populations decreased compared to four wild populations, but they still have higher level of genetic diversity. The selective breeding had already changed population structure of two selected populations, but the change was not obvious. The results in this study provided an important reference for the establishment of a more complete and effective breeding program.

Abstract:In order to study the expression pattern and function of the reproductive regulatory molecular VASA during gonadal development of the freshwater crab, Sinopotamon henanense(ShVASA), we have cloned the partial sequence of vasa gene in the freshwater crab, S. henanense (Shvasa). Based on the sequence, in the present study, we prepared the specific anti-VASA polyclonal antibody for exploring the expression pattern and function of ShVASA protein during gonadal development. A specific segment of 813 bp of Shvasa gene was selected and cloned into pET32a vector to construct the prokaryotic expression vector pET32a-Shvasa. After the recombinant vector was transferred into Escherichia coli, the recombinant VASA protein was expressed under the induction of IPTG. SDS-PAGE analysis showed that the fusion protein, which was about 47 ku, mainly existed in the supernatant. Using the fusion protein purified by Ni-NTA His-Bind affinity chromatography column as antigen, we immunized the New Zealand white rabbits, and obtained the polyclonal antibody of ShVASA protein. The titer of anti-VASA polyclonal antibody reached 1×10⁵ in ELISA assay. Furthermore, we identified the specificity of the antibody gained in this study. Immuno-adsorption and Western blot analysis indicated that the produced anti-VASA polyclonal antibody could specifically bind to the fusion protein as well as the natural ShVASA protein extracted from ovary. These results will provide a powerful tool for identification of germ cells in S. henanense and other crabs, and for the study on the function of VASA protein in decapoda.

Abstract:The morphology is an important criterion for the evaluation of carb breed quality of Eriocheir sinensis. High-quality carb breed were thought to possess patent rostral spine and verruca as well as relatively longer periopods, but it remains unclear whether these morphological characteristics can be stably inherited and be served as indicators for selective breeding of E. sinensis. Therefore, thirty-six morphological indices were used to evaluate the changes and difference of juvenile E. sinensis from pond-reared(PR) and wild-caught(WC) populations before and their offspring from the first generation (G1) and the second generation (G2) after the selective breeding programs; and the analysis methods included One-Way Analysis of variance, discriminant analysis, principal component analysis and cluster analysis for discrimination. The results showed that:(1) in One-Way Analysis of variance, there were significant differences between unselected PR and WC populations (G0) in the 16 and 15 out of 36 morphological indices for females and males respectively, and these differences disappeared gradually during selection so that no significant difference could be found in 36 morphological indices after selection for two generations (G2); (2) in discriminant analysis, the accuracy rate of discrimination were 93%-100% between unselected populations and this value decreased obviously after first and second generation of selection (G1 and G2), only 56.67%-76.67%; (3) in principal component analysis, only G0 individuals of PR and WC population could be divided into two independent groups by the first two principal components; in terms of WC populations, G0 individuals were separated from G1 and G2 individuals, and it is hard to distinguish G0, G1 and G2 individuals of PR population between each other either; (4) in cluster analysis, G0, G1 and G2 individuals of PR population clustered with G1 and G2 individuals of WC population while G0 of WC individuals clustered independently, whether females or males. In conclusion, although there was significant difference in many morphological indices between WC and PR juveniles, these differences disappeared gradually during the selection process, and the similar morphological indices were found in the juveniles of G2 between PR and WC populations. Therefore, morphological characteristics could not be used as effective indices for the selective breeding of E. sinensis.

Abstract:To study the biological significance and function of sperm flagellar protein 1 (Spef1) in the formation and assembly of spermatozoa, rapid amplification of cDNA ends (RACE) and qRT-PCR techniques were used to clone the gene cDNA of the Spef1 in Sepiella japonica and analyse the tissue expression specificity. The results showed that a 1 135 bp full-length cDNA of Spef1 gene from S. japonica (described as SjSpef1) was obtained, which consisted of a 178 bp 5' untranslated region (UTR) and a 165 bp 3'UTR. The predicted open reading frame (ORF) was 792 bp, molecular weight of the deduced protein was 30.567 7 ku, and its pI was 7.03. The SjSpef1 was hydrophilic, without signal peptide sequence and transmembrane regions, and it might play a intracellular role. Secondary structure analysis revealed that it contained rich spiral structures (49%). Homology modeling indicated that CH2 domain of Spef1 mainly consisted of four spiral structures, which were connected by some loop structures. The multiple sequence alignment showed that SjSpef1 had the highest similarity with Octopus bimaculoides which was 59.49%, which showed that Spef1 was not very conserved in evolution. Phylogenetics analysis based on Spef1 demonstrated that S. japonica had the closest relationship with O. bimaculoides. SjSpef1 gene was expressed significantly in testis by qRT-PCR. Its cloning and analysis of tissue specific expression will be of great significance to exploring its cellular localization and biological function in the future.

Abstract:Euryhaline fish, which can survive and grow in a wide range of salinity environment, have a complex mechanism to deal with salinity change. It is generally believed that at the isotonic environment, the energy consumption of fish used for osmotic regulation is the least, which was beneficial to fish growth. No previous study has reported about the isotonic point in Lateolabrax maculatus. Therefore, in this study, the blood osmotic pressure, Na⁺/K⁺/Cl^- concentration, Na⁺-K⁺-ATPase activity and relative gene expressions were detected during the periods of water desalination and freshwater adaptation. Result showed that the isotonic point of L. maculatus was 11.4 according to the changing characteristics of the osmotic pressure in fish plasma and the corresponding osmotic pressure of different water salinities. During the experiment of water desalination, both the concentrations of Na⁺, K⁺ and Cl^-and serum osmotic pressure were decreased significantly, with a slow recovery after freshwater adaptation. The results of mRNA expression of NKA genes in gill showed that the change trend of NKAα1a and NKAα1b was similar to Na⁺-K⁺-ATPase activity, except that the expression of NKAα1a in fresh water was not significantly different from that of the 30 seawater group, but the expression level of NKAα1b in fresh water was lower than 30 seawater group. After 1 day's water desalination, the expression level of NKAα3 decreased significantly, and remained low expression during fresh water adaptation. This study provided theoretical basis for desalination culture of L. maculatus.

Abstract:This study was conducted to determine the role of efflux pump inhibitors in amphenicols resistance of Vibrio species from mariculture. A total of 41 intermediate/high-level florfenicol-resistant Vibrio isolates were tested, including V. parahaemolyticus (14), V. alginolyticus (17), V. harveyi (8), and V. vulnificus (2). To investigate the effect of efflux pump on amphenicols resistance, minimal inhibitory concentrations of chloramphenicol and florfenicol with/without efflux pump inhibitors were determined using the agar dilution method. NMP, reserpine, CCCP and PAβN were used as efflux pump inhibitors in this study. PCR amplication method was used to detect the efflux pump genes and integron-related genes. The results showed that 39 strains and 11 strains were resistant to florfenicol and chloramphenicol, respectively. As is shown, 100% (41/41) of the 41 Vibrio isolates tested were detected positive for amphenicols efflux pump genes floR, but only 17.1% (7/41) for cmlA gene, and pexA, fexA, fexB and optrA could not be detected. Furthermore, Int1, SXT, and ISCR1 were found in 46.3% (19/41), 46.3% (19/41), and 63.4% (26/41) of the 41 Vibrio isolates tested, respectively. Antibiotic susceptibility testing suggested that CCCP was an effective efflux pump inhibitor in the treatment for the amphenicol resistance of Vibrio species. The prevalence of amphenicol resistance, efflux pump genes and integron-related elements in Vibrio sp. derived from marine aquaculture in China was observed and was likely due to the extensive use of amphencols. The use of efflux pumb inhibitors, e.g. CCCP, might be an effective tool to control the amphenicol resistance in Vibrio species.