Abstract:Based on the data by trawl surveys in August from 2009 to 2013 in the Laizhou Bay, we studied the fishery resources structures, such as species compositions, dominant species, spatial distribution and standing stock, to understand the effects of annual sediment flux from the Yellow River on the fishery resources structures in the Laizhou Bay. The result showed: (1)The relative biomass and species of fishery varied dramatically in interannual variation. Average catch of fish was more than those of crustaceans and cephalopods. And the catch of pelagic fish was significantly more than that of demersal fish, but the opposite phenomenon occurred in Aug. 2011. (2)The composition of dominant species was close to interannual variation, conducting succession from species which were high economic value and big to lower economic value and small species. The dominant species were different among 2009-2013. Main dominant species were Konosirus punctatus, Chaeturichthys stigmatias, Oratosquilla oratoria, Eupleurogrammus muticus and Loligo japonica. K. punctatus became the only dominant specie in 2010. (3)The Yellow River exports large amount of nutrients to the Laizhou Bay. The estuary of Yellow River and its adjacent area, a major fishery and spawning ground, have abundant species. The changes of sediment discharge from the Yellow River had effects on fishery resources structures and quantity of resources. The sediment discharges were significantly correlated with the number of fish species or demersal fish and the fishery resources. And the Yellow River sediment discharge was high significantly correlated with the biomass of demersal fish. In conclusion, the influence of the Yellow River sediment discharge into Laizhou Bay is an indispensable factor when we study the fishery resources and protect the larvae and juveniles.

Abstract:In order to study the effect of different hormones injection on marbled eel Anguilla marmorata ovarian development and to clarify the role of two gonadotropins in the process, this paper compares the induction effects treated by different hormone combinations through GSI(Gonadosomatic index), and a quantitative study by real-time fluorescent quantitative PCR(qRT-PCR)was applied to analyze the expression of the pituitary gonadotropin hormone subunits: GtHα, LHβ and FSHβ genes at different developmental ovary stages. The results showed that combination of CPE(carp pituitary extract)and hCG(human chorionic gonadotropin)can effectively induce the gonadal maturation of eels with GSI significantly increased. However, injection of androstenedione(ADSD)alone and mixture of ADSD, CPE and hCG didn't have significant impact on GSI which varied within 1%-3%. The results of quantitative fluorescence PCR showed that expression of LHβ and GtHα significantly increased among the CPE and hCG treated group, while the expression quantity of FSHβ was down-regulated. In conclusion, CPE and hCG could successfully induce female maturation, while injection of ADSD into female eel had no induction of gonadal development; meanwhile, LH plays a vital role in gonadal development in A. marmorata, and FSH plays a key role in early gonadal development, indicating that the FSH may be the key factor inducing the early development of eel's ovary.

Abstract:Mandarin fish Siniperca chuatsi is one of the most important piscivorous fish in freshwater ecosystem, and their natural resources in the Yangtze lakes have declined dramatically due to overfishing and eutrophication. The unreasonable use of fishing gears is often considered to be an important factor leading to overfishing. In this study, the catch structure characteristics of S. chuatsi captured by five fishing gears in a shallow lake(Xiaosihai Lake)along the middle reaches of the Yangtze River in 2007 were investigated and analyzed to explore the potential impact of the five fishing gears on the resource of S. chuatsi, and also provide basic data for fisheries management. The results indicated that a total of 359 samples of S. chuatsi were collected and the total length ranged from 92 to 600 mm. The dominant length ranged from 251 to 350 mm, accounting for 61. 0% of the total. The age structure of our collected samples contained 5 age groups ranging from 1 to 5, and most individuals were 2-3 years old accounting for 74. 6% of the total. Gill net, longline fishing and weir had strong fishing selectivity on S. chuatsi. The mature individuals with 2-year-old or above in S. chuatsi catches captured by gill net with 80 and 100 mm meshes accounted for 93. 3%. The average body weight of S. chuatsi captured by gill net was 466 g, and among them 57% individuals met the demand of "the standard S. chuatsi"(0. 4-0. 75 kg/ind. , having the best market price per kilogram). The mature individuals with 2-year-old or above in S. chuatsi catches captured by longline fishing accounted for 86. 9%, and the individuals of "the standard S. chuatsi" accounted for 43. 5% of the total. 90% of the S. chuatsi catches captured by weir were immature individuals under 1-year-old, which meant that weir was harmful to the recruitment population of S. chuatsi. The ranges of the total length of catches captured by electronic trawl-net and electric catching instrument were clearly higher, which indicated that the two fishing gears had little fishing selectivity on S. chuatsi. Their catches were dominated by 1- and 2-year old individuals, which may impact the population structural stability of S. chuatsi. Comparative analysis showed that gill net and longline fishing were good for sustainable utilization of S. chuatsi resources, and their catches could gain better economic benefit. So gill net(mesh should not be less than 100 mm.)was suitable to be the main fishing gear to fish S. chuatsi, and longline fishing could be an auxiliary fishing gear to fish S. chuatsi due to its low fishing efficiency. Weir was harmful to the recruitment population of S. chuatsi, so it was not suitable to fish S. chuatsi. The electronic trawl-net and electric catching instruments were both illegal fishing gears, which were extremely harmful to fisheries resources. Therefore, supervision work should be intensified so as to forbid the illegal use of these two gears.

Abstract:The physical and chemical property, glycosylation site, transmembrance domain, cellular localization, signal peptide of tilapia HSP70(tHSP70)and percent identity to the HSP70 derived from rainbow trout and other species(tHSP70)were analyzed by bioinformatics methods, and the full CDS of tHSP70 was amplified and cloned by using and the artificially synthesized cDNA. The expression plasmid of pGAPZa-HSP70 was constructed by the insertion of tHSP70 CDS into the pGAPZa-A vector, and the tHSP70 protein was then expressed in host strain of GS115. The supernatant was used to conduct the SDS-PAGE and Western-blotting, followed by the purification of tHSP70 by Ni₂⁺IDA affinity chromatography. Then the PAS staining was used to identify if the glycosylations occurred in tHSP70 protein after the expression from GS115. Then the non-expected band(about 100 bp)in the SDS-PAGE was identified by standard MALDI-TOF-MS procedure. Bioinformatic analysis showed tHSP70 contains 640 amino acids, the molecular weight is 70 274.5 mol/L and the isoelectric point is 5. 49. The half-life of tHSP70 is 30 h in mammalian reticulocyte(in vitro)and greater than 20 h in yeast, while it is more than 10 h in Escherichia coli. Additionally, the instability index and aliphatic index of tHSP70 is 36. 64 and 85. 58, respectively. Moreover, tHSP70 might totally contain 6 O-linked and 6 N-linked glycosylation sites. The cloned tHSP70 sequence was 100% identity to the sequence in NCBI database. The HSP70 protein could be efficiently expressed by methane induction of pGAPZa-HSP70 plasmid in GS115 strain. Except the 70 ku band, one 100 ku was observed on the SDS-PAGE and Western blotting gels. The PAS staining specific to the glycosyl radicals was performed and the positive signals indicated that this 100 ku band might be the consequence of glycosylations after expression in GS115. Western blotting showed the protein currently expressed was recognized by rabbit anti-human HSP70 antibody, and the MALDI-TOF-MS result demonstrated that the 100 ku protein was exactly the tilapia HSP70, 100% identity to the tilapia HSP70 in NCBI database. The present study provided experimental materials for the future cellular and immunological researches in tilapia.

Abstract:In order to study the role of anisodamine as an adjuvant in the immersion administration together with inactivated whole cell vaccines, gibel carps were administrated by immersion with inactivated Aeromonas hydrophila vaccine(inactivated Ah vaccine)with anisodamine on days 1 and 7. Spleens were sampled on days 2, 4, 7, 11, 14 and 21 after the second immersion immunization, and the expression levels of IgM, IL-1β, C3, C-lectin and lysozyme mRNAs in spleen were detected through the real-time fluorescence quantitative PCR(RT-PCR). The gibel carps from the control and immunization groups were challenged intraperitoneally with A. hydrophila YYK090901 at the dose of LD₅₀ concentration on day 21 and then mortality was determined and relative percent survival(RPS)was calculated. The results showed that the expression levels of IgM and IL-1β mRNAs of anisodamine-adjuvant vaccine group reached the peak on day 4,i.e. 28. 3 and 332. 7 respectively, but the adjuvant-free vaccine group reached the peak on day 11. The expression levels of C3, C-lectin and lysozyme mRNAs of the anisodamine-adjuvant vaccine group were significantly higher than those of the adjuvant-free group and the control, and those of the anisodamine-adjuvant group had longer expression duration than the others. The efficacy of inactivated Ah vaccine could be significantly improved by anisodamine through immersion administration, and RPS rate was 80. 0%. The results showed that anisodamine immersion administrated gibel carps together with inactivated whole cell vaccines can significantly promote the expresstion of IgM, IL-1β, C3, C-lectin and lysozyme mRNAs in spleen, and protect gibel carps better against A. hydrophila infection.

Abstract:CYP302a1 is the key enzyme in biosynthesis of the ecdysteriods. The aim of this study is to analyze the function of CYP302a1 during the process of the molting in swimming crab Portunus trituberculatus. The full-length cDNA of CYP302a1 is cloned from Y-organs of the P. tritubertulatus. The length of the CYP302a1(Genbank accession NO.: KM596851)is 3 171 bp and contains an ORF of 1 626 bp encoding 541 amino acid. The amino acid contains 5 conserved domains including helix-C, helix-K, helix-I, PERF and heme-binding. The phylogenetic tree showed that CYP302a1 of P. trituberculatus was clustered with that of Tigriopus japonicas, which is separated from other CYPs. Tissue distribution showed that transcript of CYP302a1 was mainly detected in the Y-organ(YO)and far exceeded other tissues. The transcript level of CYP302a1 during molting cycle was determined by qRT-PCR. During molting process, levels of CYP302a1 in YO were extremely low during postmolt(stages A and B), began to increase during intermolt(stage C)and reached the peak at D₁ stage, then declined. The combined results showed that CYP302a1 might play an essential role in the molting of P. trituberculatus.

Abstract:A study was carried out to test the responses of juvenile yellow catfish Pelteobagrus fulvidraco to ammonia stress and bacterial challenge. The catfish(1. 94 ± 0. 05)g were randomly allocated to 2 groups(control group and exposure group)in triplicate for 56 days ammonia exposure. No differences were found in fish final weight, weight gain and feed efficiency between ammonia group and control group, but hepatosomatic index of fish in ammonia group was significantly higher than that of fish in control group. Ammonia and glutamine contents in the brain of fish in ammonia group were significantly higher than those of fish in control group, but glutamate content was not significantly different compared with the control. Superoxide dismutase, catalase and glutathione peroxidase activities were significantly lower in ammonia group than in control group, but thiobarbituric acid reactive substance content was significantly higher in ammonia group. Lysozyme activity, phagocytic index and respiratory burst of fish in ammonia group were significantly lower compared with the control group. After 14 days infection of Aeromonas hydrophila, cumulative mortality was not significantly different between ammonia group and control group. This study indicated that the glutamine accumulation in the brain was caused by chronic ammonia exposure; the toxic reactive oxygen species is not fully counteracted by the antioxidant enzymes; the immunosuppression is a process of gradual accumulation of immunosuppressive factors. Our findings support the multifactorial pathogenesis of ammonia toxicity in fish exposed to ammonia.

Abstract:In order to explore the distribution characteristics of anaerobic ammonium oxidation(AMX)and denitrifying anaerobic methane oxidation(DAMO)bacteria in four different wetlands in summer and the key environmental factors influencing the two anaerobic denitrifier bacteria, several 16S rDNA clone libraries were constructed and correlation analysis and canonical correspondence analysis were conducted. The selected wetlands include pond wetland, ditch wetland, surface flow constructed wetland, and subsurface flow constructed wetland. The obtained results showed that the highest identity of AMX sequences related to the representative strain Candidatus Brocadia fulgida were 99%, whereas the DAMO sequences were grouped as a clade separated to the DAMO representative strain C. Methylomirabilis oxyfera. In four wetlands in summer, the Shannon indices of AMX bacteria from high to low were: surface flow constructed wetland>subsurface flow constructed wetland > pond > ditch, and the Shannon indices of DAMO bacteria was in the order of pond>subsurface flow constructed wetland > ditch> surface flow constructed wetland. The TOC and NO₃^--N in overlying water were the main factors influencing the distribution of AMX bacteria and the water TN, NH₄⁺-N, pH and DO had large effects on the distribution of DAMO. Moreover, the OTU number of AMX is the highest in sediments of surface flow constructed wetland and that of DAMO is the highest in pond. These findings demonstrated the presence of AMX in all wetlands studied, but the presence of DAMO reaction is still uncertain. The main factors affecting the distribution of two kinds of anaerobic denitrifier bacteria were C, N and pH and DO.

Abstract:A 60-d feeding experiment was conducted to investigate the effects of basic diet with four different additives of yeast polysaccharide(6. 3 g/kg), Paracoccus marcusii(10⁹ cfu/kg), rhubarb(Rhei Radix et Rhizoma, 25. 0 g/kg)and florfenicol(15. 0 mg/kg)on non-specific immunity and expression of intestinal immune gene(Aj-p105, Aj-p50, Aj-rel and Aj-lys)in sea cucumber[Apostichopus japonicus, mean initial body weight(4. 6 8± 0. 36)g]. Five groups of sea cucumbers were fed with the basal diet(control group), basal diet with yeast polysaccharide, P. marcusii, rhubarb, and florfenicol supplementation, respectively. Each diet was randomly fed to five tanks at a density of 10 sea cucumbers per tank. The results showed that the phagocytosis and respiratory burst activities of the coelomocytes of sea cucumber fed diets with P. marcusii supplementation were significantly higher than those in the control group. Dietary yeast polysaccharide supplementation significantly enhanced the phagocytosis activity of the coelomocytes compared with the control group. However, the respiratory burst activity of the coelomocytes in the florfenicol group was significantly lower than that in the control group. At transcriptional level, the relative expression of Aj-p105 and Aj-p50 genes in mid-intestine tissue of sea cucumber in yeast polysaccharide and P. marcusii groups were significantly higher than those in the control group with increase of 43. 2% and 63. 1% in yeast polysaccharide group, and with increase of 49. 8% and 48% in P. marcusii group, respectively. The relative expression of Aj-lys gene in P. marcusii group was significantly higher than that in the control group with an increase of 46. 4%. The relative expression of Aj-p105 in rhubarb group was significantly higher than that in the control group. While the expression of Aj-p50, Aj-rel and Aj-lys genes in mid-intestine of sea cucumber in florfenicol group was significantly decreased compared to the control group. In summary, these results suggested that dietary yeast polysaccharide and P. marcusii would enhance the non-specific immunity of sea cucumber, but feeding florfenicol may have an opposite effect.

Abstract:In May 2014, a severe infectious disease occurred among the farmed rainbow trout(Oncorhynchus mykiss)in Dujiangyan, Sichuan Province, associated with 40% and 80% mortality in juvenile fish and fingerlings, respectively. Bacteriologic test, histological examination, pathogenicity tests, virus isolation, multiple RT-PCR assay and phylogenetic analysis were performed to explore its causes and the epidemic law. Principal symptoms included darkening of the body, distension of abdomen, yellow mucoid fluid fecal casts from anus. Internally, hemorrhage occurred in the swim bladder and peritoneum, gastric distention and enteritis were observed. Bacteriologic test was negative. Histopathologically, anterior kidney, kidney and spleen showed degeneration and necrosis in the haematopoeitic tissue. Necrosis of the eosinophilic granular cells(EGCs)in the intestinal wall was also observed. Hepatocytes also showed degeneration and necrosis with some intracytoplasmic inclusions emerged in the hepatocyte. After filtration treatment, the spleen and kidney homogenate was injected intraperitoneally into 20 healthy trouts, and the injected trouts displayed similar clinical symptoms as the fish that was naturally infected. Trouts died acutely in the trial group with a cumulative mortality rate 75%. The filtrated homogenate was also inoculated into the epithelioma papulosum cyprini(EPC)cells, and the typical cytopathic effect was formed after three blind passages. Multiple RT-PCR reaction of tissue homogenates from the fish naturally infected, the fish artificially infected and the infected cells were performed, and the results showed all IHNV-positive. The sequenced amplification products shared 99. 9% identity with that of IHNV nucleoprotein gene(GenBank access number: KJ421216). Phylogenetic analysis based on the "mid-G" sequences showed that the isolate was classified into Asian isolates, belonging to the genogroup JRt. This is the first report of IHNV infection in cultured rainbow trout associated with mass mortality in Southwestern China.

Abstract:Epidermal growth factor(EGF)plays important roles in growth, wound healing and metamorphosis, etc. The pearl oyster Pinctada fucata is a commercially important species cultured for pearl production, in which a series of developmental transformation occur in young stage and an injury will happen during nuclear insertion. In order to evaluate the function of EGF gene during P. fucata larval development, tissue growth and nuclear insertion. In this study, cloning and expression of an EGF-like gene was carried out to provide some background for further study on growth development and pearl culture improvement. As a result, a full length cDNA of 4 107 bp was obtained and named Pf-egf1. The complete ORF encoded 234 amino acid residues, including a signal peptide, a transmembrane domain and an EGF-like domain. The EGF-like domain contained six cysteines that can form three disulfide bonds, consistent with the characteristics of Epidermal Growth Factor protein family. However, the remaining Pf-egf1 sequences were quite different from other EGF family members. So we speculated that Pf-egf1 is probably a novel EGF-like gene. The tissue expression profile showed that Pf-egf1 expressed in all the six tissues tested(mantle, muscle, gill, hepatopancreas, pearl sac, intestines and gonad), with significantly higher expression in intestines than in other tissues. The expression of Pf-egf1 presented an increasing trend from trochophore stage to metamorphosis stage in larval development, with significantly higher expression in metamorphosis stage than in other stages. The observations above indicated that Pf-egf1 gene may play important roles in intestine repairing and larval metamorphosis in P. fucata, possibly through promotion of cell proliferation, and thus can benefit to some extent further studies on modulation of growth and pearl culture.

Abstract:Catch per unit effort(CPUE)of a fishery is often used as an abundance index which is usually assumed to be proportional to the stock abundance. Observed fisheries CPUE data are, however, influenced by many factors, in addition to fish population abundance, including spatial-temporal factors such as area and season and environmental factors such as sea surface temperature(SST)and sea surface salinity. The impacts of these factors on CPUE may shift the assumed proportionality between observed CPUE and stock abundance. Thus, CPUE standardization is needed to remove the impacts of factors other than population abundance. Many statistical models have been developed for CPUE standardization such as General Linear Model(GLM)and General Additive Model(GAM). Generally, statistical methods always assume the independence of the observed CPUEs. However, this assumption is invalid for a fish school and distribution because of their spatial autocorrelation. Therefore, in this study, we take a CPUE standardization of red flying squid(Ommastrephes bartramii)as an example. Based on the fishing data in jigging fishery by Chinese fishing fleet and the corresponding SST data and the Chlorophylla data in the Northwest Pacific Ocean from June to November from 1999 to 2012, the spatial autocorrelation is incorporated into the standard general linear model(GLM). Four distance models(Gaussian, exponential, linear and spherical)are examined for spatial autocorrelation using the CPUE standardization of red flying squid. It is found that the four spatial-GLMs always produce the better goodness-of-fit to the data than that for the standard GLM. And the exponential model generates the best goodness-of-fit to the data in the four distance models. Therefore, it is suggested that spatial autocorrelation into CPUE standardization should be considered when the nominal CPUEs are strongly spatially autocorrelated.

Abstract:Based upon five contigs coding for carbonic anhydrase(CA)from a pyrosequencing transcriptome of Myrmecia incisa, gene-specific primers were designed for CA gene cloning from this green microalga. Five CA genes, named MiαCA1, MiαCA2, MiβCA1, MiβCA2 and Mi_γCA were cloned by using the technique of rapid amplification of cDNA ends. The open reading frames of the cloned full-length cDNAs were 963 bp, 1 089 bp, 1 041 bp, 738 bp and 687 bp in length, encoding putative proteins composed of 320, 362, 346, 245 and 228 amino acids, respectively. The encoded CA proteins were rich in hydrophobic amino acids which accounted for 41. 25%, 45. 31%, 43. 35%, 42. 45% and 43. 42% of total amino acids, respectively. Neighbor-joining(NJ)phylogenetic tree inferred from the putative proteins of CA genes indicated that these cloned CA genes were divided into three clades: MiαCA1 and MiαCA2 in α-CA clade, MiβCA1 and MiβCA2 in β-CA one and Mi_γCA in γ-CA one. MiαCA1 and MiαCA2 are characterized by 3 conserved His residues, MiβCA1 and MiβCA2 are by 2 conserved Cys and 1 conserved His residues whereas Mi_γCA is found to use Arg, His and Asn instead of the reported 3 residues of His to bind Zn²⁺ to form their catalysis centre. MiαCA1, clustered with CAH3 from Chlamydomonas reinhardtii in the NJ phylogenetic tree, had a two-part leader sequence, suggesting that it might be localized and associated with PSII in the thylakoid lumen like CAH3. MiαCA2, close to CAH1 after protein alignment, had a signal peptide which could lead the mature MiαCA2 to the periplasmic space resembling CAH1 in C. reinhardtii. It was predicted that this CA could function as CAH1 to transfer HCO₃^- into CO₂ for photosynthesis. Two β-CAs, MiβCA1 and MiβCA2, were clustered with CAH7 and CAH 8 from C. reinhardtii, which might be involved in interconversion between HCO₃^- and CO₂ in the cytoplasm of M. incisa. Mi_γCA, grouped with γ-CA from higher plants, was expected to be associated with the complex I of mitochondrial electron transport chain to work. The 5 cloned CA genes from M. incisa should be localized at various regions of the algal cells to cooperate with each other for the reversible interconversion of CO₂ and HCO₃^- so as to modify pH and transfer CO₂ among the organelles.

Abstract:Blunt snout bream (Megalobrama amblycephala) is one of the major freshwater aquaculture species in China, and aquaculture of this species has been rapidly expanded in the last decade. Efforts have been made over the past two decades, especially in the case of farmed fish species, to understand the dietary nutritional requirement. However, dietary nutritional requirements have generally been based on growth and deficiency symptoms, rather than on the health status indicators including immune responses and disease resistance. Generally, the physiological outcomes attributed to these nutrients or additives are presumed to be translated to good health and protected water environment. In addition, some ingredients such as vitamin have showed to play an important role in immunity function of fish. Aqua-feeds of the future are expected to impart dual benefits of good growth and health to the farmed organism, and preventive health care through nutritional means is certainly a strategy to ensure sustainability in environment friendly aquaculture. Indeed, this review addressed these concerns by providing an overview of published nutrient requirements(dietary protein, lipid, carbohydrate, vitamins and minerals)on the growth and the links between nutrition, immune response and resistance to diseases of M. amblycephala, and the influence of water temperature on the determination of these nutrients requirement in order to provide scientific references for efficient development of compound feed for this species.

Abstract:The aim of this paper is to investigate the impact of temperature stress on the oxygen and energy metabolism in hepotopancreas of shrimp Litopenaeus vannamei. In the present study, the impact of low and high temperature on the superoxide anion(O₂^-· )production, superoxide dismutase(SOD)activity, catalase(CAT)activity and glutathione(GSH)concentration, and the nitric oxide synthase(NOS)activity and the synthesis of nitric oxide(NO)was detected by their corresponding biochemical methods. In addition, the concentration of adenosine triphosphate(ATP)was also examined. The results showed that O₂^-· production could be induced significantly after cold stress at 15 ℃ and heat stress at 31and 35 ℃. SOD activity was showed a similar changing profile with the concentration of O₂^-· after thermal stress between 15 and 31 ℃. Compared with heat stress, CAT activity was enhanced more significantly after cold stress. However, GSH concentration increased significantly after high temperature stress. The NOS activity and NO concentration increased significantly after heat stress. However, ATP concentration increased significantly after both low temperature and high temperature stress, and it returned to the control level after 24 h recovery. Conclusion: Thermal stress could lead to oxygen metabolism disorder in the hepatopancreas of shrimp L. vannamei, which might induce antioxide enzymes response. Our findings suggested that SOD, CAT and GSH might play different roles in shrimp response to thermal stress. Also, NO might play an important role in induction of many signaling pathways to response to thermal stress. In addition, more ATP was produced after cold and heat stress. Our findings indicated that thermal stress lead to oxygen metabolism disorder, which might be due to the temperature stress beyond the oxygen and capacity limited thermal tolerance(OCLTT)of L. vannamei. The disorder of oxygen metabolism might have an important impact on energy metabolism and other physiological activities of L. vannamei.

Abstract:Dissolved oxygen is one of the most important factors affecting the fish growth and metabolism. Some fish exposition to hypoxia and super-saturated dissolved oxygen may result in oxidative stress evidenced by variation in activities of antioxidant enzymes. Mugil cephalus has higher economic value, and it has not been reported that there are the effects of different dissolved oxygen variation on the growth, energy metabolism and oxidative stress. In order to find the relationship and consequences, experiments were carried out according to experimental ecology, bioenergetics and physiology methods. The experiments were conducted under five modes of variation of different dissolved oxygen, i. e. N(7. 0 mg/L), N-L(7. 0→1. 5 mg/L), S-N(14. 0→1. 5 mg/L), S-N-L(14. 0→7. 0→1. 5 mg/L), and S(14. 0 mg/L)treatments, respectively. The healthful individuals(16. 07 ± 0. 11)g in mean initial total weight were cultivated for 56 days in the cycling water installation. The specific growth rate, oxidative stress indicators were measured including the content of LD, SOD, T-AOC, ASOR, MDA, T-GSH, GSSG, and GSH in the plasma, muscle, liver and gill. Then the healthful individuals(31. 47 ± 1. 44)g in mean final total weight were selected and the oxygen consumption rate, ammonia excretion rate, O: N ratios were measured. The results showed that five modes of variation of different dissolved oxygen had a significant effect on the growth of mullet. The SGR of mullet in the N, S and S-N treatments were significantly higher than in N-L and S-N-L treatments. The ammonia excretion rate and O: N ratios in S treatment was the highest compared to the other treatments. Five modes had a great influence on the oxidative stress indicators. The study found out that liver was the most important organ to respond to the oxidative stress. The metabolic rate decreased in the modes containing the hypoxia stage, moreover, the mullets need to consume more material and energy involved in the oxidative stress which caused decline of the growth rate. The content of T-GSH was negative correlation to the oxidative stress, and it seems that the glutathione system plays an important adaptive role.

Abstract:To understand the long and consecutive variation characteristics of fishery species structure in the East China Sea and the Yellow Sea, using the method of clustering and average trophic level analysis, stages and features of main fishery species structure variation have been summed up and analyzed, and the main fishery species have been classified into groups, and the relation between average trophic level and fishery resources density has been analyzed, based on 14-consecutive-year fishery resources survey data in autumn from 1999 to 2012 by paired bottom trawl. The results show that the development of fishery species structure could be divided into 3 stages, including the early stage of jellyfish bloom(1999—2003), the outbreak stage of jellyfish bloom(2004—2007)and the later stage of jellyfish bloom(2008—2012). In the early stage, variation period of fishery resources is 2 years; but in the later stage the period changed to 1 year. With 5 years of development after jellyfish bloom, it seemed that fishery species structure recovered to a stage close to the early stage of jellyfish bloom. By clustering method the main fishery species could be classified into 6 species groups, including blooming(e. g. Stomolophus meleagris), advantage(e. g. Trichiurus japonicus and Pseudosciaena polyactis), unusual(e. g. Trachurus japonicus), common(e. g. Psenopsis anomala, Pampus argenteus and Setipinna taty), jellyfish accompanying(e. g. Cyanea nozakii and Aurelia aurita)and rare(e. g. Scomber japonicus, Harpadon nehereus etc. )species groups. By comparing quantities of species before and after jellyfish bloom, the species of rare species group could be classified into 3 groups: one with species whose quantity changed from high to low(e. g. Harpadon nehereus, Coelorhynchus multispinulosus etc. ), one changed from low to high(e. g. Scomberomorus niphonius, Solenocera melantho etc. )and the other with no change(e. g. Scomber japonicus), who in these groups had some characters of indicator species for ecosystem health state. Based on the data of 14 years, the relation between average trophic level and fishery resources density was significantly negative(P< 0. 001), whose equation was TL=-0. 896 5· ln(CPUE)+ 14. 142 1(TL means average trophic level, CPUE means catch per unit effort). The relation shows that the average trophic level of the marine ecosystem decreases with the increase of its total resources quantity, and vice versa.