Fish assemblage structure in the hypoxic zone in the Changjiang (Yangtze River) estuary and its adjacent waters were analyzed based on data from bottom trawl surveys conducted on the R/V Beidou in June, August and Oct...Fish assemblage structure in the hypoxic zone in the Changjiang (Yangtze River) estuary and its adjacent waters were analyzed based on data from bottom trawl surveys conducted on the R/V Beidou in June, August and October 2006. Four fish assemblages were identified in each survey using two-way indicator species analysis (TWIA). High fish biomass was found in the northern part, central part and coastal waters of the survey area; in contrast, high fish diversity was found in the southern part of the survey area and the Changjiang estuary outer waters. Therefore, it is difficult to maintain high fishery production when high fish diversity is evenly distributed in the fish community. Fish became smaller and fish size spectra tended to be narrower because of fish species variations and differences in growth characteristics. Fish diversity increased, the age to maturity was reduced and some migrant species were not collected in the surveys. Fish with low economic value, small size, simple age structure and low tropic level were predominant in fish assemblages in the Changjiang estuary and its adjacent waters. The lowest hypoxic value decreased in the Changjiang estuary and its adjacent waters.展开更多
Based on data of demersal trawl Samples from 1987 to 1988 in the Zhujiang Estuary and its adjacent waters, relationships between fish community and environmental factors are studied by using clssification , MDS ordina...Based on data of demersal trawl Samples from 1987 to 1988 in the Zhujiang Estuary and its adjacent waters, relationships between fish community and environmental factors are studied by using clssification , MDS ordina-tion and several community parameters. The results shaw that the distribution of fish shoes is zoned by salinty anddivided into three types. The freshwater community which is restricted in the Lianhua Hill - Humen waterway is sim-ple and stable, the coastal community which lives in the shallow waters is complex, and the estuary community whichis idenhfied in the Lingdingyang area and affected by Physical and ecological pinemore greatly greatly has obvious seasonalvariations.展开更多
The intertidal zone (also known as seashore) are transition areas between land and sea, that are greatly influenced by the tide cycle, therefore, environmental parameters, such as temperature and salinity, oscillate a...The intertidal zone (also known as seashore) are transition areas between land and sea, that are greatly influenced by the tide cycle, therefore, environmental parameters, such as temperature and salinity, oscillate according to the periods in which these areas are exposed to air. Intertidal zones are highly diverse, which makes them key ecosystems for the development of sea life (both flora and fauna) exposed to drastic environmental change. The <span style="white-space:normal;font-size:10pt;font-family:;" "="">59 visual censuses campaigns were carried out during the full moon of each month from 2015 to 2019. Temperature, salinity and dissolved oxygen were recorded during each visual census and showed variations between years. Temperature showed two distinct seasons, warm and cold. A total of 14,995 organisms were recorded, belonging to 30 species, 28 genera, 15 families, five orders and one class. Ecological indices like species richness (SR), Shannon-Wiener’s diversity (H') and Fisher’s alpha (</span><i style="white-space:normal;"><span style="font-size:10pt;font-family:;" "="">α</span></i><span style="white-space:normal;font-size:10pt;font-family:;" "="">-Fisher) showed significant differences between years, 2015 and 2016 recorded as the most diverse years, while the lowest values were recorded in 2019. Therefore, fish communities of tide pools showed to be highly diverse, with 30 species recording similar relative abundances, and according to the BVI, only 11 species were dominant. Spatio-temporal variations of temperature, salinity and dissolved oxygen were highly </span><span style="white-space:normal;font-size:10pt;font-family:;" "="">cor</span><span style="white-space:normal;font-size:10pt;font-family:;" "="">related </span><span style="white-space:normal;font-size:10pt;font-family:;" "="">to</span><span style="white-space:normal;font-size:10pt;font-family:;" "=""> changes in fish community structure, and the dominance of certain species, which are of great importance for the structure and dynamic of the tide pool communities.</span><span style="white-space:normal;font-size:10pt;font-family:;" "=""> Therefore, the aim of the present study was to determine the fish community structure of tide pools during the low tide in the intertidal zone of a locality known as El Faro, on the west coast of La Paz, B. C. S., Mexico.</span>展开更多
The lightweight design of hydraulic quadruped robots,especially the lightweight design of the leg joint Hydraulic Drive Unit(HDU),can improve the robot's response speed,motion speed,endurance,and load capacity.How...The lightweight design of hydraulic quadruped robots,especially the lightweight design of the leg joint Hydraulic Drive Unit(HDU),can improve the robot's response speed,motion speed,endurance,and load capacity.However,the lightweight design of HDU is a huge challenge due to the need for structural strength.This paper is inspired by the geometric shape of fish bones and biomimetic reinforcing ribs on the surface of the HDU shell are designed to increase its strength and reduce its weight.First,a HDU shell with biomimetic fish bone reinforcing ribs structure is proposed.Then,the MATLAB toolbox and ANSYS finite element analysis module are used to optimize the parameters of the biomimetic reinforcing ribs structure and the overall layout of the shell.Finally,the HDU shell is manufactured using additive manufacturing technology,and a performance testing platform is built to conduct dynamic and static performance tests on the designed HDU.The experimental results show that the HDU with biomimetic fish bone reinforcing ribs has excellent dynamic performance and better static performance than the prototype model,and the weight of the shell is reduced by 20%compared to the prototype model.This work has broad application prospects in the lightweight and high-strength design of closed-pressure vessel components.展开更多
The genetic population structure of red snapper Lutjanus malabaricus and orange-spotted grouper Epinepheluscoiodes in Brunei and Sabah was investigated using allozyme electrophoresis. Samples were collected from three...The genetic population structure of red snapper Lutjanus malabaricus and orange-spotted grouper Epinepheluscoiodes in Brunei and Sabah was investigated using allozyme electrophoresis. Samples were collected from threesites in Brunei for E. coiodes and from three sites in Brunei and Sabah for L. malabaricus. A total of 22 loci and 16loci were scored, respectively. The index of fixation (FST) for the E. coiodes population was 0.176 but, in general, itlacked within-population structuring. The FST was particularly high between Brunei Bay/Jerudong and Brunei Bay/Kuala Belait, suggesting genetic subdivision on a small spatial scale. Isolation of Brunei Bay from the South ChinaSea may constrain the movement of adult fishes and larval dispersal, thereby reducing homogeneity amongsubpopulations. All variable loci for E. coiodes were in Hardy–Weinberg equilibrium except for MDH* and GTDHP*(P < 0.01), in which two subpopulations showed an excess of heterozygotes (P < 0.01). The study on the L.malabaricus population showed a heterozygote deficit of approximately 60% in variable loci (FIS, genetic variationwithin population = 0.45;P < 0.05);however, the mean observed heterozygosity for the population far exceeded L.malabaricus populations in Australia and Indonesia. A FST value of 0.076 revealed moderate genetic differentiationamong subpopulations of L. malabaricus. The genotypes were likely to be drawn from the same distribution inJerudong and Kuala Belait. This study infers that sustainable management of snapper and grouper resources inBrunei waters must take into account the presence of a single stock and two stocks, respectively.展开更多
In the last decades, surface drag reduction has been re-emphasized because of its practical values in engineering applications,including vehicles, aircrafts, ships, and fuel pipelines. The bionic study of drag reducti...In the last decades, surface drag reduction has been re-emphasized because of its practical values in engineering applications,including vehicles, aircrafts, ships, and fuel pipelines. The bionic study of drag reduction has been attracting scholars' attentions. Here, it was determined that the delicate microstructures on the scales of the fish Ctenopharyngodon idellus exhibit remarkable drag-reduction effect. In addition, the underlying drag-reduction mechanism was carefully investigated. First,exceptional morphologies and structures of the scales were observed and measured using a scanning electron microscope and3-dimensional(3D) microscope. Then, based on the acquired data, optimized 3D models were created. Next, the mechanism of the water-trapping effect of these structures was analyzed through numerical simulations and theoretical calculations. It was determined that there are many microcrescent units with certain distributions on its surface. In fact, these crescents are effective in generating the "water-trapping" effect and forming a fluid-lubrication film, thus reducing the skin friction drag effectively.Contrasting to a smooth surface, the dynamics finite-element analysis indicated that the maximum drag-reduction rate of a bionic surface is 3.014% at 0.66 m/s flow rate. This study can be used as a reference for an in-depth analysis on the bionic drag reduction of boats, underwater vehicles, and so forth.展开更多
基金Supported by the National Natural Science Foundation of China (No. 30490233, 40906086)the National Basic Research Program of China (973 Program) (No. 2006CB400608)Taishan Scholar Program of Shandong Province, Postdoctoral creative foundation of Shandong Province and the Yellow & Bohai Sea Scientific Observation and Experiment Station for Fishery Resources and Environment, Ministry of Agriculture
文摘Fish assemblage structure in the hypoxic zone in the Changjiang (Yangtze River) estuary and its adjacent waters were analyzed based on data from bottom trawl surveys conducted on the R/V Beidou in June, August and October 2006. Four fish assemblages were identified in each survey using two-way indicator species analysis (TWIA). High fish biomass was found in the northern part, central part and coastal waters of the survey area; in contrast, high fish diversity was found in the southern part of the survey area and the Changjiang estuary outer waters. Therefore, it is difficult to maintain high fishery production when high fish diversity is evenly distributed in the fish community. Fish became smaller and fish size spectra tended to be narrower because of fish species variations and differences in growth characteristics. Fish diversity increased, the age to maturity was reduced and some migrant species were not collected in the surveys. Fish with low economic value, small size, simple age structure and low tropic level were predominant in fish assemblages in the Changjiang estuary and its adjacent waters. The lowest hypoxic value decreased in the Changjiang estuary and its adjacent waters.
文摘Based on data of demersal trawl Samples from 1987 to 1988 in the Zhujiang Estuary and its adjacent waters, relationships between fish community and environmental factors are studied by using clssification , MDS ordina-tion and several community parameters. The results shaw that the distribution of fish shoes is zoned by salinty anddivided into three types. The freshwater community which is restricted in the Lianhua Hill - Humen waterway is sim-ple and stable, the coastal community which lives in the shallow waters is complex, and the estuary community whichis idenhfied in the Lingdingyang area and affected by Physical and ecological pinemore greatly greatly has obvious seasonalvariations.
文摘The intertidal zone (also known as seashore) are transition areas between land and sea, that are greatly influenced by the tide cycle, therefore, environmental parameters, such as temperature and salinity, oscillate according to the periods in which these areas are exposed to air. Intertidal zones are highly diverse, which makes them key ecosystems for the development of sea life (both flora and fauna) exposed to drastic environmental change. The <span style="white-space:normal;font-size:10pt;font-family:;" "="">59 visual censuses campaigns were carried out during the full moon of each month from 2015 to 2019. Temperature, salinity and dissolved oxygen were recorded during each visual census and showed variations between years. Temperature showed two distinct seasons, warm and cold. A total of 14,995 organisms were recorded, belonging to 30 species, 28 genera, 15 families, five orders and one class. Ecological indices like species richness (SR), Shannon-Wiener’s diversity (H') and Fisher’s alpha (</span><i style="white-space:normal;"><span style="font-size:10pt;font-family:;" "="">α</span></i><span style="white-space:normal;font-size:10pt;font-family:;" "="">-Fisher) showed significant differences between years, 2015 and 2016 recorded as the most diverse years, while the lowest values were recorded in 2019. Therefore, fish communities of tide pools showed to be highly diverse, with 30 species recording similar relative abundances, and according to the BVI, only 11 species were dominant. Spatio-temporal variations of temperature, salinity and dissolved oxygen were highly </span><span style="white-space:normal;font-size:10pt;font-family:;" "="">cor</span><span style="white-space:normal;font-size:10pt;font-family:;" "="">related </span><span style="white-space:normal;font-size:10pt;font-family:;" "="">to</span><span style="white-space:normal;font-size:10pt;font-family:;" "=""> changes in fish community structure, and the dominance of certain species, which are of great importance for the structure and dynamic of the tide pool communities.</span><span style="white-space:normal;font-size:10pt;font-family:;" "=""> Therefore, the aim of the present study was to determine the fish community structure of tide pools during the low tide in the intertidal zone of a locality known as El Faro, on the west coast of La Paz, B. C. S., Mexico.</span>
文摘The lightweight design of hydraulic quadruped robots,especially the lightweight design of the leg joint Hydraulic Drive Unit(HDU),can improve the robot's response speed,motion speed,endurance,and load capacity.However,the lightweight design of HDU is a huge challenge due to the need for structural strength.This paper is inspired by the geometric shape of fish bones and biomimetic reinforcing ribs on the surface of the HDU shell are designed to increase its strength and reduce its weight.First,a HDU shell with biomimetic fish bone reinforcing ribs structure is proposed.Then,the MATLAB toolbox and ANSYS finite element analysis module are used to optimize the parameters of the biomimetic reinforcing ribs structure and the overall layout of the shell.Finally,the HDU shell is manufactured using additive manufacturing technology,and a performance testing platform is built to conduct dynamic and static performance tests on the designed HDU.The experimental results show that the HDU with biomimetic fish bone reinforcing ribs has excellent dynamic performance and better static performance than the prototype model,and the weight of the shell is reduced by 20%compared to the prototype model.This work has broad application prospects in the lightweight and high-strength design of closed-pressure vessel components.
基金the Universiti Brunei Darussalam through research grant no.PNC2/2/RG/1(18).
文摘The genetic population structure of red snapper Lutjanus malabaricus and orange-spotted grouper Epinepheluscoiodes in Brunei and Sabah was investigated using allozyme electrophoresis. Samples were collected from threesites in Brunei for E. coiodes and from three sites in Brunei and Sabah for L. malabaricus. A total of 22 loci and 16loci were scored, respectively. The index of fixation (FST) for the E. coiodes population was 0.176 but, in general, itlacked within-population structuring. The FST was particularly high between Brunei Bay/Jerudong and Brunei Bay/Kuala Belait, suggesting genetic subdivision on a small spatial scale. Isolation of Brunei Bay from the South ChinaSea may constrain the movement of adult fishes and larval dispersal, thereby reducing homogeneity amongsubpopulations. All variable loci for E. coiodes were in Hardy–Weinberg equilibrium except for MDH* and GTDHP*(P < 0.01), in which two subpopulations showed an excess of heterozygotes (P < 0.01). The study on the L.malabaricus population showed a heterozygote deficit of approximately 60% in variable loci (FIS, genetic variationwithin population = 0.45;P < 0.05);however, the mean observed heterozygosity for the population far exceeded L.malabaricus populations in Australia and Indonesia. A FST value of 0.076 revealed moderate genetic differentiationamong subpopulations of L. malabaricus. The genotypes were likely to be drawn from the same distribution inJerudong and Kuala Belait. This study infers that sustainable management of snapper and grouper resources inBrunei waters must take into account the presence of a single stock and two stocks, respectively.
基金supported by the National Natural Science Foundation of China(Grant Nos.51305282,51505183&51325501)Program for Excellent Talents of Liaoning Provincial Committee of Education(Grant No.LJQ2014071)
文摘In the last decades, surface drag reduction has been re-emphasized because of its practical values in engineering applications,including vehicles, aircrafts, ships, and fuel pipelines. The bionic study of drag reduction has been attracting scholars' attentions. Here, it was determined that the delicate microstructures on the scales of the fish Ctenopharyngodon idellus exhibit remarkable drag-reduction effect. In addition, the underlying drag-reduction mechanism was carefully investigated. First,exceptional morphologies and structures of the scales were observed and measured using a scanning electron microscope and3-dimensional(3D) microscope. Then, based on the acquired data, optimized 3D models were created. Next, the mechanism of the water-trapping effect of these structures was analyzed through numerical simulations and theoretical calculations. It was determined that there are many microcrescent units with certain distributions on its surface. In fact, these crescents are effective in generating the "water-trapping" effect and forming a fluid-lubrication film, thus reducing the skin friction drag effectively.Contrasting to a smooth surface, the dynamics finite-element analysis indicated that the maximum drag-reduction rate of a bionic surface is 3.014% at 0.66 m/s flow rate. This study can be used as a reference for an in-depth analysis on the bionic drag reduction of boats, underwater vehicles, and so forth.
