Characterization and antioxidant activities of marine pepsin soluble collagen from the skin of yellow goosefish Lophius litulon

Characteristics and antioxidant activities of pepsin-soluble collagen(PSC) from yellow goosefish( Lophius litulon) skins were investigated. PSC was characterized as a type I collagen, and its imino acid content was 193 residues/1 000 residues. PSC's denaturation temperature was ~17.56°C and Fourier transform infrared spectra confirmed the presence of triple helices. Solubility analysis showed good solubility at acidic pH(1–6) or low Na Cl concentrations(≤2%). PSC showed scavenging activity against hydroxyl radicals and superoxide anions in a concentration-dependent manner. Furthermore, PSC could protect D-galactose-induced skin aging by significantly controlling malondialdehyde formation and improving the activity of superoxide dismutase, glutathione peroxidase, catalase, glutathione, and hydroxyproline. PSC may be a promising antioxidant in appropriate applications.     

Current status of small yellow croaker resources in the southern Yellow Sea and the East China Sea

We used data from bottom trawl surveys to study the factors influencing the abundance of small yellow croaker, Larimichthys polyactis, in the southern Yellow Sea (SYS) and the East China Sea (ECS). The resource density index (RDI) was generally higher in summer and autumn than in spring and winter. RDIs were also significantly greater in the SYS than in the ECS in summer and autumn. The bottom water salinity and depth of spatial distribution of small yellow croaker was similar between the two areas in summer, but different in other seasons. Regression analysis suggested that environmental factors such as bottom water temperature, salinity, and depth influenced the RDIs in summer in these areas. Growth condition factor (GCF) in the two areas varied monthly and the croaker in the SYS grew more slowly than those in the ECS. This was likely due to the low bottom temperature of the Yellow Sea Cold Water Mass in summer and autumn or to higher human fishing pressure in the ECS. To ensure sustainable utilization of the croaker stocks in these regions, we recommend reducing the fishing intensity, increasing the cod-end mesh size, and improving the protection of juveniles.     

Relationships of growth and mortality to enzymatic activity,and the relative mRNA expression of cultured scallops Patinopecten yessoensis in the Yellow Sea,China

The bottom aquaculture of yesso scallop(Pa tinopecten yessoensis)has developed rapidly in the north of Yellow Sea,China,but not without accompanying productivity problems.We,therefore,conducted field surveys to investigate factors related to growth and mortality rates of bottom-cultured scallops after release.Specifically,we focused on the effects of total antioxidant capacity(TAOC)and three key enzymes involved in antioxidant and metabolic function:glutamic pyruvic transaminase(GPT),lactic dehydrogenase(LDH),and superoxide dismutase(SOD).Across summer and winter,we also measured the relative mRNA expression of GPT and SOD to understand their seasonal variation in the scallops,along with how such variation correlated to growth and mortality.Results show that bottom cultured scallops experienced mass mortality during the first six months post-release.During winter(December),scallops grew more rapidly and suffered less mortality than in summer(August).The observed lower performance probably resulted from less advantageous environmental factors during the summer seasons,such as high temperature and low dissolved oxygen.These environmental stressors enhance protein consumption while decreasing energetic resources in scallops.Furthermore,scallops in summer exhibited high antioxidant levels that probably competed for energy with process integral to growth and survival.These negative factors combined to elevate mortality rates.In conclusion,we provided evidence suggesting correlations between metabolic/antioxidant activity and growth and mortality of bottom-cultured yesso scallops.These correlations implied us an accurate method to estimate the performance of bottom culture system.Suggestions about innovative aquaculture techniques were also discussed in the study.Our results might provide a possible guideline to the improvement of bottom culture techniques for this commercially valuable seafood species.     

Age and growth of chub mackerel (Xcomber japonicus) in the East China and Yellow Seas using sectioned otolith samples

Although chub mackerel (Scomber japonicus) is a primary pelagic fish species, we have only limited knowledge on its key life history processes. The present work studied the age and growth of chub mackerel in the East China and Yellow Seas. Age was determined by interpreting and counting growth rings on the sagitta otoliths of 252 adult fish caught by the Chinese commercial purse seine fleet during the period from November 2006 to January 2007 and 150 juveniles from bottom trawl surveys on the spawning ground in May 2006. The difference between the assumed birth date of 1st April and date of capture was used to adjust the age determined from counting the number of complete translucent rings. The parameters of three commonly used growth models, the von Bertalanffy, Logistic and Gompertz models, were estimated using the maximum likelihood method. Based on the Akaike Information Criterion (AIC), the von Bertalanffy growth model was found to be the most appropriate model. The size-at-age and size-at-maturity values were also found to decrease greatly compared with the results achieved in the 1950s, which was caused by heavy exploitation over the last few decades.     

First record of Paraonella platybranchia （Hartman, 1961） （Polychaeta： Paraonidae） from the Yellow Sea

This paper reports for the first time a species of polychaetous family Paraonidae, Paraonella platybranchia (Hartman, 1961), a rare species found previously only in the coast near the boundary between the United States and Mexico, and it was recently discovered in the samples collected in 1982 from Chinese side of the Yellow Sea. This is the first record of the species in China as well as in the Northwest Pacific.     

Survival, growth and immune activity of scallop Chlamys farreri cultured at different depths in Haizhou Bay(Yellow Sea,China)during hot season

Survival, growth and immune response of the scallop, Chlamys farreri, cultured in lantern nets at five different depths (2, 5, 10, 15, and 20 m below the sea surface) were studied in Haizhou Bay during the hot season (summer and autumn) of 2007. Survival and growth rates were quantified bimonthly. Immune activities in hemolymph (superoxide dismutase (SOD) and acid phosphatase (ACP)) were measured to evaluate the health of scallops at the end of the study. Environmental parameters at the five depths were also monitored during the experiment. Mortalities mainly occurred during summer. Survival of scallops suspended at 15 m (78.0%) and 20 m (86.7%) was significantly higher than at 2 m (62.9%), 5 m (60.8%) or 10 m (66.8%) at the end of the study. Mean shell height grew significantly faster at 10 m (205.0 μm/d) and 20 m (236.9 μm/d) than at 2, 5 or 15 m in summer (July 9 to September 1); however, shell growth rate at 20 m was significantly lower than at the other four depths in autumn (September 2 to November 6). In contrast to summer, scallops at 5 m grew faster (262.9 μm/d) during autumn. The growth of soft tissue at different depths showed a similar trend to the shell. Growth rates of shell height and soft tissue were faster in autumn than in summer, with the exception of shell height at 20 m. SOD activity of scallops increased with depth, and ACP activity was significantly higher at 15 and 20 m than at other depths, which suggests that scallops were healthier near the bottom. Factors explaining the depth-related mortality and growth of scallops are also discussed. We conclude that the mass mortality of scallop, C. farreri, during summer can be prevented by moving the culture area to deeper water and yield can be maximized by suspending the scallops in deep water during summer and then transferring them to shallow water in autumn.     

The suspended sediment concentration distribution in the Bohai Sea, Yellow Sea and East China Sea

The distribution of the suspended sediment concentration (SSC) in the Bohai Sea, Yellow Sea and East China Sea (BYECS) is studied based on the observed turbidity data and model simulation results. The observed turbidity results show that (i) the highest SSC is found in the coastal areas while in the outer shelf sea areas turbid water is much more difficult to observe, (ii) the surface layer SSC is much lower than the bottom layer SSC and (iii) the winter SSC is higher than the summer SSC. The Regional Ocean Modeling System (ROMS) is used to simulate the SSC distribution in the BYECS. A comparison between the modeled SSC and the observed SSC in the BYECS shows that the modeled SSC can reproduce the principal features of the SSC distribution in the BYECS. The dynamic mechanisms of the sediment erosion and transport processes are studied based on the modeled results. The horizontal distribution of the SSC in the BYECS is mainly determined by the current-wave induced bottom stress and the fine-grain sediment distribution. The current-induced bottom stress is much higher than the wave-induced bottom stress, which means the tidal currents play a more significant role in the sediment resuspension than the wind waves. The vertical mixing strength is studied based on the mixed layer depth and the turbulent kinetic energy distribution in the BYECS. The strong winter time vertical mixing, which is mainly caused by the strong wind stress and surface cooling, leads to high surface layer SSC in winter. High surface layer SSC in summer is restricted in the coastal areas.     

Survival, growth and immune activity of scallop Chlamys farreri cultured at different depths in Haizhou Bay (Yellow Sea, China) during hot season

Survival, growth and immune response of the scallop, Chlamys farreri, cultured in lantern nets at five different depths (2, 5, 10, 15, and 20 m below the sea surface) were studied in Haizhou Bay during the hot season (summer and autumn) of 2007. Survival and growth rates were quantified bimonthly. Immune activities in hemolymph (superoxide dismutase (SOD) and acid phosphatase (ACP)) were measured to evaluate the health of scallops at the end of the study. Environmental parameters at the five depths were also monitored during the experiment. Mortalities mainly occurred during summer. Survival of scallops suspended at 15 m (78.0%) and 20 m (86.7%) was significantly higher than at 2 m (62.9%), 5 m (60.8%) or 10 m (66.8%) at the end of the study. Mean shell height grew significantly faster at 10 m (205.0 μm/d) and 20 m (236.9 μm/d) than at 2, 5 or 15 m in summer (July 9 to September 1); however, shell growth rate at 20 m was significantly lower than at the other four depths in autumn (September 2 to November 6). In contrast to summer, scallops at 5 m grew faster (262.9 μm/d) during autumn. The growth of soft tissue at different depths showed a similar trend to the shell. Growth rates of shell height and soft tissue were faster in autumn than in summer, with the exception of shell height at 20 m. SOD activity of scallops increased with depth, and ACP activity was significantly higher at 15 and 20 m than at other depths, which suggests that scallops were healthier near the bottom. Factors explaining the depth-related mortality and growth of scallops are also discussed. We conclude that the mass mortality of scallop, C. farreri, during summer can be prevented by moving the culture area to deeper water and yield can be maximized by suspending the scallops in deep water during summer and then transferring them to shallow water in autumn.     

Wind stress field over the Bohai Sea,the Yellow Sea and the East China Sea

Seasonal and annual with stress fields over the Bohai Sea, the Yellow Sea and the East China Sea were computed from the wind rose data compiled in the Climatic Atlas of Chinese Offshore Areas and North-west Pacific and published by the Ocean Press in 1982. 684 wind roses in 2° latitude by 2° longitude boxes constructed from 278,815 wind reports are involved in the present study. The computations are principally intended as a data source for further research. Some oceanographic consequences are expounded on.     

Methane in the Yellow Sea and East China Sea: dynamics,distribution, and production

Journal of Oceanology and Limnology - The Yellow Sea (YS) and East China Sea (ECS) are important marginal seas of the western Pacific. Understanding the dynamics of methane (CH4) in the YS and ECS...     

Impact of microzooplankton and Calanus sinicus (Brodsky, 1962) on phytoplankton in the Yellow Sea during early summer

Dilution incubations and Calanus sinicus addition incubations were simultaneously conducted at five stations in the Yellow Sea in June of 2004 to evaluate the impact of microzooplankton and Calanus sinicus on phytoplankton based on the Chlorophyll a (Chl-a) levels. The Chl-a growth rates (k) ranged from 0.60–1.67 d⁻¹, while microzooplankton grazed the Chl-a at rates (g) of 0.29–0.62 d^t-1. The addition of C. sinicus enhanced the Chl-a growth rate (Z) by 0.004–0.037 d⁻¹ ind.⁻¹ L. C. sinicus abundance ranged from 84.1–160.9 ind. m⁻³, which occupied 90.7%–99.1% of the copepod (>500 μm) population. The in-situ increase in phytoplankton by C. sinicus community was estimated to be 0.000 4–0.005 9 d⁻¹. These results showed that microzooplankton were the main grazers of phytoplankton, while C. sinicus induced a slight increase in the levels of phytoplankton.     

Population genetic structure of the mantis shrimp Oratosquilla oratoria(Crustacea: Squillidae) in the Yellow Sea and East China Sea

The mantis shrimp O ratosquilla oratoria is an ecologically and economically important species in the Western Pacific. In present study, the population genetic structure of O ratosquilla oratoria from the Yellow Sea and East China Sea was examined with mitochondrial DNA control region sequences. In total, 394 samples were collected from 18 locations and 102 haplotypes were obtained. For the Yellow Sea, the overall nucleotide diversity and haplotype diversity were 0.006 9 and 0.946 8, respectively; while across all the East China Sea locations, the overall nucleotide diversity and haplotype diversity were 0.027 94 and 0.979 0, respectively. The results of AMOVA and pairwise F_(ST)(0.145 2, P 0.001) revealed moderate differentiation between the Yellow Sea and East China Sea populations of O. oratoria. However, neither the neighbor-joining tree nor haplotype network showed clades with geographic pattern, which indicated considerable gene flow was existed between the Yellow Sea and East China Sea, and supporting the high larval dispersal ability in this species. Mismatch distribution analysis and neutrality tests suggested that O. oratoria has undergone population expansion event, and the Pleistocene glacial cycles might have an impact on the historical demography of O. oratoria. The genetic information obtained in this study can provide useful information for sustainable improvements for capture fisheries management strategies.     

Mitochondrial DNA control region diversity and population structure of Pacific herring (Clupea pallasii) in the Yellow Sea and the Sea of Japan

To investigate the genetic variation and population structure of Pacific herring in the Yellow Sea and the genetic differentiation between the Yellow Sea and the Sea of Japan,fragments of 479-bp mitochondrial DNA control region were sequenced for 110 individuals collected from three different periods in the Yellow Sea and one locality in the Sea of Japan.High haplotype diversity and moderate nucleotide diversity were observed in Pacific herring.AMOVA and exact test of population differentiation showed no significant genetic differentiations among the three populations of the Yellow Sea and suggested the populations can be treated as a single panmictic stock in the Yellow Sea.However,a large and significant genetic differentiation(WST50.11;P50.00) was detected between the populations in the Yellow Sea and the Sea of Japan.The high sea water temperature in the Tsushima Strait was thought a barrier to block the gene exchange between populations of the two sea areas.The neutrality tests and mismatch distribution indicated recent population expansion in Pacific herring.     

Studies on the breeding habits of the minke whale (Balaenoptera acutorostrata) in the Yellow Sea

Minke whales caught in the Yellow Sea range from 4.16 m to 8.60 m in length with an average length of 6.93 m for the female and 6.14 m for the male. Sex ratio of the female is 74.3%. The pregnancy ratio of all sexually matured females is 65.8%. The minimum size of the pregnant whale observed is 6.60 m in length. Females having a body length of more than 7 m long are all sexually matured. According to the studies on the embryos obtained from the females caught in the northern Yellow Sea, there is only one breeding season each year. Mating mostly occurs from July through September, and the length of pregnancy is ten to eleven months with the peak of calving from May through July. Most females breed one calf each time, only two cases with twins. Sex ratio of female fetus is 56.6%, and the newly born calf measures 250–270 cm in body length. This paper was published in Chinese inOceanologia et Limnologia Sinica 13 (4): 338–345.     

Seasonal phenology of the heterotrophic dinoflagellate Noctiluca scintillans(Macartney) in Jiaozhou Bay and adjacent coastal Yellow Sea,China

Seasonal variations in numerical abundance, cell diameter and population carbon biomass of the heterotrophic dinoflagellate Noctiluca scintillans were studied for 10 years from 2004 to 2013 in Jiaozhou Bay and adjacent coastal Yellow Sea, China, and their ecological functions were evaluated. In both areas, N. scintillans occurred throughout the year and demonstrated an essentially similar seasonality; the cell abundance increased rapidly from the winter minimum to an annual peak in late spring and early summer, and decreased gradually toward the autumn-winter minimum. The peak abundance differed by years, and there was no consistent trend in long-term numerical variations. The cell diameter also showed a seasonal fluctuation, being larger in spring and early summer than the other seasons. Estimated carbon biomass of N. scintillans population reached to a peak as high as 90.3 mg C/m~3, and occasionally exceed over phytoplankton and copepod biomass. Our results demonstrate that N. scintillans in northwestern Yellow Sea displays the seasonal phenology almost identical to the populations in other temperate regions, and play important trophic roles as a heterotroph to interact with sympatric phytoplankton and copepods.     

Growth and mortality of small yellow croaker (Larimichthys polyactis) inhabiting Haizhou bay of China

Length frequency data of small yellow croaker(Larimichthys polyactis) were acquired from the survey vessel in May,July,September and December,2011 in Haizhou Bay of China.In this study,921 fish individuals were analyzed for the estimation of growth and mortality parameters.Between length and weight,the power coefficient b was 2.7321,2.9703,3.0418 and 2.7252 for the 4 surveying months,respectively.The estimated von Bertalanffy growth function parameters were 230mm(L ∞) and 0.26yr-1(K) as were calculated with ELEFAN method equipped in FiSAT computer package.With length-converted catch curve analysis,the total mortality rate(Z) and its 95% confidence interval were 2.16(1.69-2.64) yr-1,0.59(0.15-1.04) yr-1,1.16(0.80-1.52) yr-1 and 0.96(0.70-1.23) yr-1 for the 4 surveying months,respectively,with the pooled data the value was 1.15(0.81-1.48) yr-1.The natural mortality rate(M) was 0.516 yr-1 as was calculated with Pauly’s equation(the annual average sea water temperature was 11℃).Therefore,fish mortality rate was 0.634 yr-1.The yield-per-recruit analysis indicated that when t c was 1,F max was 0.7 and F 0.1 was 0.55.Currently,the age at first capture is about 1 year and F current was 0.634.Therefore,F current was larger than F 0.1 and less than F max.This indicates that current fish mortality is at a dangerously high level.With Gulland method,the biological reference point for fishery(F opt) was estimated as 0.516 yr-1,lower than current fish mortality.Accordingly,reducing catch in the region was strongly recommended.     

DNA barcode assessment of Ceramiales (Rhodophyta) in the intertidal zone of the northwestern Yellow Sea

A total of 142 specimens of Ceramiales(Rhodophyta) were collected each month from October 2011 to November 2012 in the intertidal zone of the northwestern Yellow Sea. These specimens covered 21 species,14 genera,and four families. Cluster analyses show that the specimens had a high diversity for the three DNA markers,namely,partial large subunit r RNA gene(LSU),universal plastid amplicon(UPA),and partial mitochondrial cytochrome c oxidase subunit I gene(COI). No intraspecific divergence was found in our collection for these markers,except for a 1–3 bp divergence in the COI of Ceramium kondoi,Symphyocladia latiuscula,and Neosiphonia japonica. Because short DNA markers were used,the phylogenetic relationships of higher taxonomic levels were hard to evaluate with poor branch support. More than half species of our collection failed to find their matched sequences owing to shortage information of DNA barcodes for macroalgae in Gen Bank or BOLD(Barcode of Life Data) Systems. Three specimens were presumed as H eterosiphonia crispella by cluster analyses on DNA barcodes assisted by morphological identification,which was the first record in the investigated area,implying that it might be a cryptic or invasive species in the coastal area of northwestern Yellow Sea. In the neighbor-joining trees of all three DNA markers,H eterosiphonia japonica converged with D asya spp. and was distant from the other Heterosiphonia spp.,implying that H. japonica had affinities to the genus Dasya. The LSU and UPA markers amplified and sequenced easier than the COI marker across the Ceramiales species,but the COI had a higher ability to discriminate between species.     

Daptonema parabreviseta sp. nov. (Xyalidae,Nematoda) from the Jiaozhou Bay of the Yellow Sea,China

A new species of free-living marine nematode of the genus Daptonema Cobb, 1920 is described from the sublittoral sediment of the Jiaozhou Bay, Qingdao. Daptonema parabreviseta sp. nov. is characterized by having narrowed anterior end; small funnel-shaped buccal cavity; short cephalic setae; spicules with bulbiform proximal end and pointed distal end; gubercunalum tubular shape with a blunt dorsal apophysis. The female genital system presents a spacious postvulval sac. The new species closely resembles Daptonema brevisetosum Thanh & Gagarin, 2009. However, it differs from Daptonema brevisetosum by having relatively narrowed head (10 μm vs 20 μm); spicules with bulbiform proximal end and pointed distal end, not bifurcated at distal end. Female genital system with a spacious postvulval sac (vs absent).

     

Reproductive cycle of Ophiopholis mirabilis (Echinodermata: Ophiuroidea) in Zhangzi Island area,northern Yellow Sea

Ophiopholis mirabilis is a common species with a high population density on the western coasts of the northern Pacific Ocean.The number of O.mirabilis has been increasing recently in the scallop aquaculture zone(the Zhangzi Island area,northern Yellow Sea) in China.To explore the mechanism of its population variation,the reproductive cycle of O.mirabilis was investigated in this area(39°04'N;122°51'E) from February 2017 through January 2018 and determined by the monthly gonad index(GI),histological examinations of the gonads and the oocyte size-frequency distribution.O.mirabilis had a clear annual reproductive cycle that was synchronous between males and females.Sea temperature and food availability played important roles in O.mirabilis reproduction.The GI value was less reliable for determining reproductive activity in O.mirabilis because the nutritive tissues within the gonads may be utilized to synthesize gametes,leading to a decrease in GI during maturation.The histological results also show that abundant nutritive phagocytes were present in the gonads of O.mirabilis,which,together with the germ cells,affected the weight of the gonads.In addition,the mature oocytes of O.mirabilis were relatively small(75-150 μm),indicating that the larval development was planktotrophic.This study provided insights into the reproductive patterns and biology of O.mirabilis and is an essential basis for the quantity control of this species in aquaculture areas.