Abstract:Larimichthys polyactis is an important economic bottom fish in China. Understanding the spatial and temporal distribution and abundance index of L. polyactis contributes to the scientific management of L. polyactis resources. In this study, the Geostatistical delta-generalized linear mixed models (geostatistical delta-GLMM) was used to analyze the spatial distribution of the wintering population of the Yellow Sea and Bohai Sea L. polyactis from 2001 to 2011 and from 2015 to 2017 in the central and southern Yellow Sea. The biomass index of L. polyactis was estimated by geostatistical delta-GLMM, ordinary Kriging interpolation-based method and design-based swept area method, respectively. The results showed that there were mainly three high-density areas of biomass areas in the overwintering ground of the Yellow Sea in 2001 and 2002, namely, the north (36°00'-37°37.5'N, 123°15'-124°15'E), the central (33°75'-36°00'N, 123°15'-124°75'E) and the southeast (32°00'-33°75'N, 124°00'-125°15'E), and the central region had the highest density. Since 2003, the biomass density of L. polyactis has declined, and the density core area in the north and southeast has declined more than the central density core area. In winter, the total biomass index of L. polyactis is contrary to the change trend of the annual yield of L. polyactis and fishing boat power, showing a downward trend. In most years, the number of stations is more than 37, and the range of stations covers the study area. The factors of sampling stations can be excluded, which indicates that the resources of L. polyactis are still facing overfishing and the population is in a declining state. By 2016-2017, the density core area became less obvious. The geostatistical delta-GLMM estimated the total biomass index of the L. polyactis in the winter of 2001-2017 is more accurate than that estimated by the swept area method and ordinary Kriging interpolation-based method.

Abstract:In order to understand the tempo-spatial distributions of fish resources in Jiaozhou Bay, we conducted four surveys on the fishery resources in Jiaozhou Bay by the underlying single trawl in 2016 and 2017. The surveyed results showed that there existed obvious differences in the seasonal variations in the density of fish resources. Individual density of fish resources was the highest in summer (233 427 ind/km²), followed by those in winter (40 746 ind/km²) and autumn (32 246 ind/km²), while that in spring was the lowest (18 080 ind/km²). Mass density of fish resources in winter was the highest (1 593.16 kg/km²), followed by those in summer (825.55 kg/km²) and spring (681.96 kg/km²), while that in autumn was the lowest (337.91 kg/km²). Among them, the average weight of fish in winter was the highest (39.10 g), followed by those in spring (37.72 g) and autumn (10.48 g), while that in summer (3.54 g) was the lowest. Compared with the historically surveyed data, the fish resources in Jiaozhou Bay have shown a significant downward trend during the past 30 years. The fish resource density (1 593.16 kg/km²) was lower than that in 1981-1982 (10 857.00 kg/km²) and 2008-2009 (2 196.00 kg/km²); the average individual mass of fish was 10.60 g, which was lower than that in 1981-1982 (37.70 g). There existed a trend of miniaturization and low-quality in the structure of fish community in Jiaozhou Bay. These changes may have been mainly caused by destruction of fish habitat and the deterioration of the ecological environment of the sea due to human activities.

Abstract:Grass carp (Ctenopharyngodon idella) is an important economic freshwater fish in China. Under intensive aquaculture conditions, the farmed grass carps often display excess fat accumulation, such as fatty liver, rotund shape and increased body lipid content. To evaluate the possibility of genetic improvement, this study estimated the phenotypic variability and correlation of lipid traits in C. idella. A total of 15 quantitative traits of 17 month-old C. idella among 296 individuals were analyzed by mathematical statistical methods. The results showed that intraperitioneal fat index IPF, hepatopancreas lipid content HLC and muscle lipid content MLC had high variation in C. idella, and the phenotypic variation coefficients ranged from 21.30% to 47.04%. Correlation analysis showed that there was a significant positive correlation among the three lipid traits, suggesting that the process of lipid deposition has a certain synchronization in different tissues of C. idella. Furthermore, factor and cluster analysis revealed that the observed 15 quantitative traits were roughly divided into 4 categories:body shape factor, body size factor, organ index factor, and body lipid content factor. IPF belonged to organ index factor, while HLC and MLC formed body fat content factor together. In addition, multivariate statistical analysis showed that the explanation degree of morphological traits on the variation of the three lipid traits ranged from 7.45% to 24.83%. By contrast, sagittal shape SS can, to some extent, predict body lipid traits. In summary, the lipid traits of C. idella have great potential for genetic improvement, and IPF would be an attractive character as breeding target. This study provided important reference for genetic improvement of lipid traits in C. idella.

Abstract:Stenotrophomonas maltophilia is one of the major pathogens causing high lethality and infectious diseases of Ictalurus punctatus in recent years. In order to provide technical reserves for the prevention and treatment of this disease, S. maltophilia XH.SM.1 strain was subjected to whole genome sequencing and comparative genomics analysis, and its morphological characteristics were observed by scanning electron microscopy. Electron microscopic observation showed that the short rod-shaped bacteria at both ends of XH.SM.1 had a length of about (1.73±0.35) μm and a width of about (0.43±0.04) μm. XH.SM.1 strain contained a chromosome of 4.56 Mb with an average G+C content of 66.60%, 4 087 coding sequences (CDS).The genomic sequence was uploaded to NCBI and obtained accession number:PYBO01000001.1. By comparing with the VFDB database, three virulence genes with a higher confidence level were predicted. The results of collinear analysis showed that XH.SM.1 had good collinearity with 10 S. maltophilia at the level of completion. ARDB database prediction and genomic island analysis found that XH.SM.1 contains many drug resistance genes. The results of pan-genomic analysis showed that XH.SM.1 showed an open result, which is consistent with the phenotype of the pathogenic bacteria that are often found in the environment, indicating that it can adapt to the environment and the outside world. Its ability to communicate with genetic material is better.

Abstract:The prevalence of multiple emerging diseases including acute hepatopancreatic necrosis disease (AHPND) has caused serious economic losses of crustacean aquaculture industry in China in last several years. In order to analyzing the possible pathogenic agents related to the slow growth of Portunus trituberculatus from Weifang City, Shandong Province, the presence and infection of nine suspected pathogens in the disease P. trituberculatus individuals were investigated by using the molecular detection methods in present study. The nine pathogens included white spot syndrome virus (WSSV), Infectious Hypodermal and hematopoietic necrosis virus (IHHNV), shrimp hemocyte iridescent virus (SHIV), AHPND-causing Vibrio parahaemolyticus (Vp_AHPND), enterocytozoon hepatopenaei (EHP), covert mortality nodavirus (CMNV), yellow head virus (YHV) and hepatopancreatic parvovirus (HPV). Meanwhile, histopathological analysis and in situ hybridization (ISH) were performed on the clinical samples. Results of molecular analysis showed that the P. trituberculatus samples were determined to be positive of Vp_AHPND and negative of other seven pathogens. Multiple sequence alignment based on the amplicons of Vp_AHPND nested-PCR of the samples revealed that sequences of the amplicons from P. trituberculatus samples shared 99% similarity to the pirA^vp virulence gene from the pathogenic V. parahaemolyticus. Phylogenetic analysis indicated that the sequence from P. trituberculatus samples was clustered into the same branch with the reported PirA of pathogenic V. parahaemolyticus. Histological examination revealed necrosis of epithelial cells in hepatopancreas tubules, myonecrosis of cardiac muscle in heart, necrosis of epithelial columnar cells of gills, severe damage of nerve cell in the thoracic ganglion, as well as nuclear pyknosis in these tissues. Micrographs of ISH showed that blue-violet hybridization signals of the Vp_AHPND probes were present in the lesions of the hepatopancreas, myocardium, gills, and thoracic ganglia. The results indicated that the P. trituberculatus samples from the shrimp and crab polyculture ponds were naturally infected by Vp_AHPND, which caused serious pathological damages of the hepatopancreas, myocardium, gills, and thoracic ganglia. The present study revealed, for the first time, that Vp_AHPND infection in P. trituberculatus and the pathological changes caused by the infection. The results provided basic information for revealing the natural host species of Vp_AHPND, and for the prevention and control of AHPND of P. trituberculatus.

Abstract:Carassius auratus var. dongting originates from Beimin Lake, Hunan. Compared to other Carassius spp., C. auratus var. dongting had a higher growth rate and larger body size, and we therefore hypothesized that these growth advantages were related to polyploidization. To verify this hypothesis, a 9 microsatellite ploidy identification method was developed to examine the ploidy level of C. auratus var. dongting, and flow cytometry assays and chromosome karyotype assays were used to further confirm the findings. The results showed that 9 microsatellites could completely distinguish 37 ploidy-known specimens. The genotyping results showed that all the 136 ploidy-unknown individuals were triploid, all three genotypes (AAA, AAB/ABB, and ABC) were observed in this population. The mean DNA content of blood cells in C. auratus var. dongting (159.42±5.64) was 1.5 times that of blood cells in C. auratus var. red (102.43±3.54), and the results from microsatellite markers were totally concordant with those from flow cytometry analysis. The karyotype analysis revealed that the number of chromosomes was 3n=156±and the karyotypic formula was 3n=39m+36sm+81sta, NF=231. This study not only established a microsatellite-based system for ploidy identification of C. auratus, but also systematically confirmed that C. auratus var. dongting is triploid.

Abstract:In order to explore the melanocortin receptor 1 gene (MC1R) in Amphilophus citrinellus embryo development and the formation of the body color expression location and function of the test preparation of MC1R gene RNA is antisense probes, T7 has sense direction of transcription of RNA probe concentration is 447.529 ng/μL, SP6 direction of transcription antisense RNA probe concentration is 342.698 ng/μL. After 10 to 20 times dilution probe was used for in situ hybridization, the MC1R gene probe expression positioning shows that A. citrinellus embryo developmental hybridization signal was weakening trend in general, the intestinal phase and bubble phase, yolk and lateral embryonic body parts have a hybridization signal distribution; in the film stage, hybridization signals appeared in the spine, yolk sac and yolk sac contents and pigment cells. There is a signal distribution on the yolk surface. In general, hybridization signals are specifically expressed in chordate, yolk sac and yolk sac contents and pigment cells, and the sense probe as a negative control group in five embryonic stages without any signal, sage MC1R expression positioning shows that the signal is revealed in A. citrinellus pigment cells that play an important regulating role in differentiation, migration, and are also associated with nerve, nutrition, immune function, preliminary establishment of fish body color related gene function and orientation of the entire embryo in situ hybridization method.

Abstract:To investigate the changes of flavor components of Oreochromis niloticus during the processing of Shanghai smoked fish, high performance liquid chromatography (HPLC), amino acid auto-analyzer and gas chromatography-mass spectrometry (GC-MS) were employed to analyze and identify the flavor components of Shanghai smoked fish in four processing stages (fresh O. niloticus, the first pickling, the first pickling followed by frying and Shanghai smoked fish products). The results showed that IMP, as main umami nucleotide, its contents of later stages were significantly higher than that of the earlier stages. Moreover, the contents of free amino acids and taste amino acids had the same trend as the IMP, among them, aspartic acid and glutamic acid had the greatest influence on the flavor of Shanghai smoked fish. In addition, 50, 84, 78 and 82 volatile components were detected in fresh O. niloticus, first pickling, first pickling followed by frying and Shanghai smoked fish products respectively, which were mainly composed of aldehydes, ketones, alcohols and hydrocarbons. Therefore, its fishy smell of O. niloticus was greatly improved by pickling and frying as they were the main cause of its flavor formation.

Abstract:In this study, the black rockfish (Sebastes schlegelii) was selected as the research object. Three groups with different temperature treatments were set up, including high temperature group (24℃), control group (20℃) and low temperature group (16℃). Histology, ELISA and qRT-PCR methods were used to investigate the effect of different temperatures on gonadal differentiation and the potential mechanism. The results showed that at 40 dpb, the gonads developed fastest at 24℃, and slowest at 16℃. The female ratio were 70.0%, 42.9% and 33.3%, at 24℃, 20℃ and 16℃ respectively. At 24℃ and 20℃, high level of E₂ lasted for a long time and T level decreased sharply at 30-35 dpb. At 16℃, E₂ level dropped rapidly, and the T was still at a high level at 35 dpb. It indicated that at high temperature, the E₂ level was high, whereas T level was fairly low during gonad differentiation, and the gonad tended to be female; on the contrary, the gonad preferred to be male. At 24℃, the cyp19a1a mRNA expression was significantly up-regulated at 35-40 dpb, which may be associated with the partial female gonad development at high temperature. At 16℃, The ERβ2 mRNA expression was significantly decreased at 30-50 dpb. The inhibition of ERβ2 expression may be related to the partial male gonad development at low temperature. At 24℃ and 20℃, foxl2 mRNA expression was at relative high level at 25-35 dpb, and the expression level of low temperature treatment group began to increase at 30 dpb. It indicated that the high expression of foxl2 may be related to the rate of ovarian differentiation during the early stage of gonadal differentiation. At 30-50 dpb, the general trend of expression levels of sox3, sox9 and dmrt1 was consistent, indicating there is a connection between the expressions of the three genes, which might be related to the rate of testis differentiation.

Abstract:Migration and distribution of aquatic animals have always been considered as the research hotspots of aquatic ecology, and the aim is to understand the pattern of migration and the relationship between migration and environmental factors. This kind of research plays an important role in the protection and management strategy of aquatic animals. Monitor by tagging, prediction by species distribution models, speculation based on analysis of microchemistry and stable isotope recorded in organism tissues are the three main methods and have widely been used in the research aspects including species distribution under climate influence. The three methods consist of many technological tools, models and test contents in its own method system respectively, but little study has focused on the summary of these methods, and collaborative usage of the three methods has not received high attention. So the three main methods for understanding migration and distribution of aquatic animals were reviewed. Meanwhile, literature research on migration and distribution of aquatic animals using related methods was introduced to some extent. The three methods were recognized as effective tools for understanding migration and distribution of aquatic animals, and the present study has focused on the comparison among the different means which were used in each of the three methods, but little research has displayed high value on collaborative usage of the three methods. In addition, statistical analysis of catch can be used to know the migration pattern of fishes and other fishery resources in fishery. The suggestions listed in this paper can provide good reference for the research on migration and distribution of aquatic animals.

Abstract:In order to analyze ecological characteristics of Arctic fish species, based on scientific information available on Alaska Arctic marine fish ecology, the present study analyzes the ecological characteristics and importance of 104 fish species from the following aspects, i.e., depth distribution, trophic level, diel vertical migration, seasonal migration, and ecological, traditional culture and commercial importance. The results indicate that most of Arctic fish species studied are pelagic or mesopelagic and living in continental shelf or shelf slope shallower than 1 000 m. Most of the fish in the Arctic Alaska have diel vertical movements with daytime descending and nighttime rising. The trophic level of those species ranged from 3.0 to 4.5 and few fish species at higher or lower trophic levels. The importance of most of fish species is unknown and only a few fish species play a key role in the Arctic Alaska marine ecosystem, traditional culture and commercial fishery based on the data available. About half of fish species demonstrates either diel vertical migration or seasonal movement. Based on clustering analysis, 5 ecological groups contain 104 Arctic fish species, considering depth of distribution, diel vertical migration, seasonal movement and trophic level as variables; however, 3 importance groups can be identified with ecological, traditional culture and commercial importance as variables. The results from the present study can provide data support for further studying on ecology of Arctic fish species and exploitation potential evaluation of Arctic fish resources and also provide reference information for China's participation in potential exploitation of Arctic fish resources and international negotiation.

Abstract:The wide coverage of the north and south seas of China makes the ecological environment geographically different. Octopus minor inhabiting different sea areas thus formed corresponding apparent differences in morphology. A multi-variate analysis method including the principal component analysis, discriminant analysis, One-Way ANOVA and stepwise discriminant analysis was used to comprehensively analyze the 14 morphological indexes of 11 natural O. minor populations along the coasts of China and a population discriminant function was established. The results showed that the arm formula of O. minor was 1 > 2 > 3 > 4 and the web formula was A > B > C > D > E. Principal component analysis showed two principal components were constructed with a cumulative contribution rate of 66.067%. The first principal component included the MW/TL, HW/TL and FFL/TL, with their contribution rate of 36.979%, while the second principal component contained the TWt/TL, ML/TL and FL/TL with the contributory rate of 29.088%. Importantly, the Penghu group can be clearly distinguished based on the scatter plots of principal component analysis. The integrative discrimination accuracy was 60.400% based on the discriminant functions. One-Way analysis of variance (ANOVA) implied that there are significant differences between the number of suckers in the arms of Penghu and the other populations. The cluster analysis revealed that five northern populations and the Yilan population grouped together at first, then clustered with Shengsi, Nanjidao and Lianjiang, then finally clustered with Penghu, while Quangang formed into a separated group. All of those indicated that five northern populations showed high morphological similarity while it was not the case for the southern populations. And there are significant variations between the northern and southern populations. Especially Penghu and Quangang populations exhibited/showed relatively large differences with the others. In summary, eleven O. minor populations in the coastal Chinese sea exhibited significant morphological divergence, and the morphological diversity was relatively high.