2021 Vol. 43, No. 8
Display Method:
2021, 43(8): 1-16.
doi: 10.12284/hyxb2021056
Abstract:
A high resolution numerical model based on a proven FVCOM with a Lagrangian particle tracking module was introduced to simulate water particle movement under differences controlling conditions, including the tide, wind, boundary circulation flow, temperature, salinity, wave coupling etc. Combined with simulate results and the actual drift bottles movement paths, factors influencing Ulva prolifera were discussed. The results showed that the migration path of U. prolifera firstly migrated northward along the coast of northern Jiangsu to the sea area near the abandoned Huanghe River
A high resolution numerical model based on a proven FVCOM with a Lagrangian particle tracking module was introduced to simulate water particle movement under differences controlling conditions, including the tide, wind, boundary circulation flow, temperature, salinity, wave coupling etc. Combined with simulate results and the actual drift bottles movement paths, factors influencing Ulva prolifera were discussed. The results showed that the migration path of U. prolifera firstly migrated northward along the coast of northern Jiangsu to the sea area near the abandoned Huanghe River
2021, 43(8): 17-30.
doi: 10.12284/hyxb2021114
Abstract:
Transparent exopolymer particles (TEP) play an important role in the marine micro-food web and the marine carbon cycle. The distribution patterns and influencing factors of TEP in the coast of eastern Fujian in summer are investigated in this research. The results show that the contents of TEP (calculated with xanthan gum as the standard substance, the same below) in the coast of eastern Fujian ranged from 25.2 μg/L to 935.5 μg/L, with an average value of (201.8±177.9) μg/L. The level of TEP is high in the near-shore and low in the far-shore, which in surface layer is lower than that in bottom layer. Correlation analysis shows that TEP in the research area are positively correlated with turbidity, silicate, phosphate, nitrite, nitrate and ammonium concentration, negatively correlated with pH, DO concentration and Net-level phytoplankton. The results of chlorophyll a fractions show that Net-level phytoplankton in the area may contribute more to TEP than other size phytoplankton. Comparing with phytoplankton as the main controlling factor of TEP in the open ocean, TEP in the coast of eastern Fujian in summer are mainly produced by phytoplankton in the decline stage, and its distribution is mainly affected by the resuspension of particles. The results can not only further clarify the differences between the influencing factors of TEP in the coastal waters and the open ocean, but also supplement the gaps in the study of TEP distribution in different regions of coastal waters in China.
Transparent exopolymer particles (TEP) play an important role in the marine micro-food web and the marine carbon cycle. The distribution patterns and influencing factors of TEP in the coast of eastern Fujian in summer are investigated in this research. The results show that the contents of TEP (calculated with xanthan gum as the standard substance, the same below) in the coast of eastern Fujian ranged from 25.2 μg/L to 935.5 μg/L, with an average value of (201.8±177.9) μg/L. The level of TEP is high in the near-shore and low in the far-shore, which in surface layer is lower than that in bottom layer. Correlation analysis shows that TEP in the research area are positively correlated with turbidity, silicate, phosphate, nitrite, nitrate and ammonium concentration, negatively correlated with pH, DO concentration and Net-level phytoplankton. The results of chlorophyll a fractions show that Net-level phytoplankton in the area may contribute more to TEP than other size phytoplankton. Comparing with phytoplankton as the main controlling factor of TEP in the open ocean, TEP in the coast of eastern Fujian in summer are mainly produced by phytoplankton in the decline stage, and its distribution is mainly affected by the resuspension of particles. The results can not only further clarify the differences between the influencing factors of TEP in the coastal waters and the open ocean, but also supplement the gaps in the study of TEP distribution in different regions of coastal waters in China.
2021, 43(8): 31-40.
doi: 10.12284/hyxb2021118
Abstract:
To investigate the changes in mercury (Hg) speciation in vegetated sediments of the wetlands in Changjiang River Estuary, China, following the invasion of Spartina alterniflora, we determined total mercury (THg), methylmercury (MeHg), toatal organic carbon (TOC), reduced sulfur (S) and grain size in core sediments (0−40 cm) vegetated with different plants in wetlands. The results showed that: (1) the mean concentrations of THg were 49.9−100.9 μg/kg in sediments vegetated by S. alterniflora,
To investigate the changes in mercury (Hg) speciation in vegetated sediments of the wetlands in Changjiang River Estuary, China, following the invasion of Spartina alterniflora, we determined total mercury (THg), methylmercury (MeHg), toatal organic carbon (TOC), reduced sulfur (S) and grain size in core sediments (0−40 cm) vegetated with different plants in wetlands. The results showed that: (1) the mean concentrations of THg were 49.9−100.9 μg/kg in sediments vegetated by S. alterniflora,
2021, 43(8): 41-53.
doi: 10.12284/hyxb2021082
Abstract:
The Zhujiang River Mouth Basin is a petroleum-bearing basin with a high degree of exploration in the northern continental margin of the South China Sea, the analysis of fault characteristics is crucial to its basin evolution model and hydrocarbon accumulation mechanism. According to the high-resolution seismic data and drilling data, the fine seismic geological interpretation of the Kaiping Sag in the southwest of the basin is carried out. Based on the fault grade and scale, the fault structure type is divided into the first-level basin-controlled fault, the second-level sag-controlled fault and the third-level control fault based on the level and scale of faults belt fracture and four-level control ring fracture, identify “Y” shaped faults, stepped faults, and heart-shaped faults combination styles on the seismic section, identify three plane combinations of parallel, goose, and oblique based on the fault plane distribution Types of quantitative statistics of the fault strike characteristics show that under the action of the right-handed stress field, from the Eocene to the Early Miocene, the strike direction continued to rotate clockwise in the direction of NE→EW→NW, and the fracture activity gradually weakened. It is also believed that due to the impact of the Indian-Eurasian plate collision, the subduction and retreat of the Pacific plate and the continuous southward movement of the ancient South China Sea, the Zhujiang River Mouth Basin formes a typical extensional tensile stress field environment. It contributes to the development of three groups of faults in the near NE direction, the EW direction and the near-NW direction during the Eocene-Oligocene period. It provides an explanation and supplement to the geological structural characteristics of Kaiping Sag, and provides a reference for the development characteristics and genetic mechanism of the ocean-continent transition zone on the northern margin of the South China Sea.
The Zhujiang River Mouth Basin is a petroleum-bearing basin with a high degree of exploration in the northern continental margin of the South China Sea, the analysis of fault characteristics is crucial to its basin evolution model and hydrocarbon accumulation mechanism. According to the high-resolution seismic data and drilling data, the fine seismic geological interpretation of the Kaiping Sag in the southwest of the basin is carried out. Based on the fault grade and scale, the fault structure type is divided into the first-level basin-controlled fault, the second-level sag-controlled fault and the third-level control fault based on the level and scale of faults belt fracture and four-level control ring fracture, identify “Y” shaped faults, stepped faults, and heart-shaped faults combination styles on the seismic section, identify three plane combinations of parallel, goose, and oblique based on the fault plane distribution Types of quantitative statistics of the fault strike characteristics show that under the action of the right-handed stress field, from the Eocene to the Early Miocene, the strike direction continued to rotate clockwise in the direction of NE→EW→NW, and the fracture activity gradually weakened. It is also believed that due to the impact of the Indian-Eurasian plate collision, the subduction and retreat of the Pacific plate and the continuous southward movement of the ancient South China Sea, the Zhujiang River Mouth Basin formes a typical extensional tensile stress field environment. It contributes to the development of three groups of faults in the near NE direction, the EW direction and the near-NW direction during the Eocene-Oligocene period. It provides an explanation and supplement to the geological structural characteristics of Kaiping Sag, and provides a reference for the development characteristics and genetic mechanism of the ocean-continent transition zone on the northern margin of the South China Sea.
2021, 43(8): 54-65.
doi: 10.12284/hyxb2021090
Abstract:
Based on the analysis of the rare earth element (REE) geochemical characteristics and clay mineral assemblages of Core TS6 sediment samples in the southern area of Southwest Taiwan Basin, South China Sea, the provenance and characteristics of its changes, material transport mechanism of sediments in the study area over the last 19 ka (the last deglaciation) are discussed. The comprehensive analysis of provenance shows that the rivers in Taiwan are the main provenance of sediments in the study area. The rivers in the west of Taiwan contribute more than the rivers in the east, and the Zhujiang River also transports part of sediments to the study area. Due to the large differences on the types and contents of the main clay minerals in different provenance areas, it is judged that the illite and chlorite of the clay minerals in the study area are mainly provided by the rivers in Taiwan; the kaolinite is mainly provided by the Zhujiang River and the less content of montmorillonite is provided by Luzon Island in the southeast. Since the last deglacial period, the input of terrigenous materials in the study area has been gradually reduced under the control of sea level changes. The provenance changes reflected by the combination of clay minerals are mainly controlled by changes in climate and ocean currents, and the influence of multiple factors may be superimposed.
Based on the analysis of the rare earth element (REE) geochemical characteristics and clay mineral assemblages of Core TS6 sediment samples in the southern area of Southwest Taiwan Basin, South China Sea, the provenance and characteristics of its changes, material transport mechanism of sediments in the study area over the last 19 ka (the last deglaciation) are discussed. The comprehensive analysis of provenance shows that the rivers in Taiwan are the main provenance of sediments in the study area. The rivers in the west of Taiwan contribute more than the rivers in the east, and the Zhujiang River also transports part of sediments to the study area. Due to the large differences on the types and contents of the main clay minerals in different provenance areas, it is judged that the illite and chlorite of the clay minerals in the study area are mainly provided by the rivers in Taiwan; the kaolinite is mainly provided by the Zhujiang River and the less content of montmorillonite is provided by Luzon Island in the southeast. Since the last deglacial period, the input of terrigenous materials in the study area has been gradually reduced under the control of sea level changes. The provenance changes reflected by the combination of clay minerals are mainly controlled by changes in climate and ocean currents, and the influence of multiple factors may be superimposed.
2021, 43(8): 66-80.
doi: 10.12284/hyxb2021098
Abstract:
The radial sand ridges is a typical sedimentary accumulation body distributed off the coast of Jiangsu Province. Under the influence of the sediment supply of the Changjiang River and the Huanghe River as well as the coastal tidal current, the typical silty-muddy tidal flats are developed, and the sediment elements can record the important information of the environmental changes of the tidal flats. Three short core samples were collected in the tidal flat of radial sand ridges to establish a reliable chronological framework and geochemical element testing, and 14 elements with high X-ray fluorescence (XRF) core scanner analysis signal strength were selected for clustering and correlation method to extract environmental information. The sedimentary environment changes of the northern Jiangsu radial sand ridges under the influence of human activities and coastal environment changes in the past 100 years were studied. The results indicate that the contents of Si, Ca and Fe in the core sediments of typical tidal flat profile in this area are relatively high, and the contents of Si, Ca and Fe increasing from north to south, while the contents of Mn, Ba, Cu and Zn are low, and the little changes in contents at all profiles changes. In terms of vertical change, Si, Ca and Fe have the same vertical change trend, while Ni, Zn and S have the opposite change trend with Si, Ca and Fe in different sediment cores. Correlation and clustering analysis show that Si, Ca and Fe have high correlation, that is, they have similar geochemical behavior and consistent material source. In addition, it is negatively correlated with elements Ni, Cu and Zn, suggesting that these elements have different geochemical behaviors with the former. The sedimentary environment changes of the tidal flat are obvious and show different patterns in different regions in the northern Jiangsu radial sand ridges, and the material source, hydrodynamic environment and human activities are the main reasons leading to the change of the sedimentary environment.
The radial sand ridges is a typical sedimentary accumulation body distributed off the coast of Jiangsu Province. Under the influence of the sediment supply of the Changjiang River and the Huanghe River as well as the coastal tidal current, the typical silty-muddy tidal flats are developed, and the sediment elements can record the important information of the environmental changes of the tidal flats. Three short core samples were collected in the tidal flat of radial sand ridges to establish a reliable chronological framework and geochemical element testing, and 14 elements with high X-ray fluorescence (XRF) core scanner analysis signal strength were selected for clustering and correlation method to extract environmental information. The sedimentary environment changes of the northern Jiangsu radial sand ridges under the influence of human activities and coastal environment changes in the past 100 years were studied. The results indicate that the contents of Si, Ca and Fe in the core sediments of typical tidal flat profile in this area are relatively high, and the contents of Si, Ca and Fe increasing from north to south, while the contents of Mn, Ba, Cu and Zn are low, and the little changes in contents at all profiles changes. In terms of vertical change, Si, Ca and Fe have the same vertical change trend, while Ni, Zn and S have the opposite change trend with Si, Ca and Fe in different sediment cores. Correlation and clustering analysis show that Si, Ca and Fe have high correlation, that is, they have similar geochemical behavior and consistent material source. In addition, it is negatively correlated with elements Ni, Cu and Zn, suggesting that these elements have different geochemical behaviors with the former. The sedimentary environment changes of the tidal flat are obvious and show different patterns in different regions in the northern Jiangsu radial sand ridges, and the material source, hydrodynamic environment and human activities are the main reasons leading to the change of the sedimentary environment.
2021, 43(8): 81-92.
doi: 10.12284/hyxb2021078
Abstract:
The submarine topographic features and distribution types of the Xuande atoll in the Xisha Islands have important indications for the influence of regional geological structure, sea level rise and fall, and ocean hydrodynamics. In order to study the submarine topography and geomorphology of the Xuande atoll, we detailed survey in the Xuande atoll of the Xisha Islands, including side scan sonar, single-beam sounding, and surface sediment sampling. The results show that: (1) Xuande atoll is a type of incomplete atoll, with lagoon deposits in the middle, and four water channels with a water depth of about 60 m had been divided, namely, the gate of the Xishazhou at the northwest of the atoll, the “Red Grass Gate” of the Nanshazhou-Yongxing, the gap on the west side of the atoll, and the gap on the south side of the atoll; (2) according to the geomorphic features, the underwater geomorphic types of the Xuande atoll are divided into 3 grades and 11 types of grades classification systems. The dynamic geomorphology units such as sand waves and grooves in the study area show that the submarine features in the shallow water area of Xuande atoll are controlled by prevailing monsoons and wave sites. The tidal channel water body formed by the deep water entrance is the main factor shaping the dynamic geomorphology of the Xuande atoll lagoon area. There are six levels of underwater terraces on the seaward slope in the southeastern part of the study area. By comparing the characteristics of the coral reef terraces in the South China Sea, the genesis of the seaward slope terraces on the Xuande atoll is likely to be a combination of global sea level changes and crustal subsidence.
The submarine topographic features and distribution types of the Xuande atoll in the Xisha Islands have important indications for the influence of regional geological structure, sea level rise and fall, and ocean hydrodynamics. In order to study the submarine topography and geomorphology of the Xuande atoll, we detailed survey in the Xuande atoll of the Xisha Islands, including side scan sonar, single-beam sounding, and surface sediment sampling. The results show that: (1) Xuande atoll is a type of incomplete atoll, with lagoon deposits in the middle, and four water channels with a water depth of about 60 m had been divided, namely, the gate of the Xishazhou at the northwest of the atoll, the “Red Grass Gate” of the Nanshazhou-Yongxing, the gap on the west side of the atoll, and the gap on the south side of the atoll; (2) according to the geomorphic features, the underwater geomorphic types of the Xuande atoll are divided into 3 grades and 11 types of grades classification systems. The dynamic geomorphology units such as sand waves and grooves in the study area show that the submarine features in the shallow water area of Xuande atoll are controlled by prevailing monsoons and wave sites. The tidal channel water body formed by the deep water entrance is the main factor shaping the dynamic geomorphology of the Xuande atoll lagoon area. There are six levels of underwater terraces on the seaward slope in the southeastern part of the study area. By comparing the characteristics of the coral reef terraces in the South China Sea, the genesis of the seaward slope terraces on the Xuande atoll is likely to be a combination of global sea level changes and crustal subsidence.
2021, 43(8): 93-104.
doi: 10.12284/hyxb2021062
Abstract:
DNA barcoding technology is a tool for rapid and accurate species identification using short orthologous DNA sequence. In this study, both traditional morphology and DNA barcoding technology was used to accurately identify ichthyoplankton species in the Changjiang River Estuary and its adjacent waters. Morphological description was carried out at the same time. The results showed that in spring and summer of 2016 and summer of 2017, 55 species of ichthyoplankton were obtained, belonging to 9 orders and 19 families. Among them, there were 35 species of Perciformes at most. The seasonal variation of ichthyoplankton in fish group was not obvious, while there was significant seasonal variation in species. Only Coilia mystus, Engraulis japonius and Larimichthys polyactis appeared both in spring and summer. It was the first time to describe the morphological characteristics of Harpadon nehereus larva and juvenile. In addition, the quantifiable characters, fin development and melanin distribution of larvae and juvenile of Harpadon nehereus, Chelon affinis, Eleutheronema tetradactylum, Sillago japonica and Paraplagusia japonica, were described and drew. The research could provide a scientific basis for the study of fish nursery in estuaries, and also provide a new way for the accumulation of taxonomic data in the early stage of fish development.
DNA barcoding technology is a tool for rapid and accurate species identification using short orthologous DNA sequence. In this study, both traditional morphology and DNA barcoding technology was used to accurately identify ichthyoplankton species in the Changjiang River Estuary and its adjacent waters. Morphological description was carried out at the same time. The results showed that in spring and summer of 2016 and summer of 2017, 55 species of ichthyoplankton were obtained, belonging to 9 orders and 19 families. Among them, there were 35 species of Perciformes at most. The seasonal variation of ichthyoplankton in fish group was not obvious, while there was significant seasonal variation in species. Only Coilia mystus, Engraulis japonius and Larimichthys polyactis appeared both in spring and summer. It was the first time to describe the morphological characteristics of Harpadon nehereus larva and juvenile. In addition, the quantifiable characters, fin development and melanin distribution of larvae and juvenile of Harpadon nehereus, Chelon affinis, Eleutheronema tetradactylum, Sillago japonica and Paraplagusia japonica, were described and drew. The research could provide a scientific basis for the study of fish nursery in estuaries, and also provide a new way for the accumulation of taxonomic data in the early stage of fish development.
2021, 43(8): 105-117.
doi: 10.12284/hyxb2021072
Abstract:
In order to improve the forecasting ability of the fishery forecast model for the longline bigeye tuna (Thunnus obesus), we proposed a marine environment feature extraction method based on deep convolutional embedded clustering (DCEC), combined with generalized additive model (GAM) for forecasting the longline bigeye tuna fishing grounds in the Southwest Indian Ocean. We used the MODIS-Aqua and MODIS-Terra sea surface temperature (SST) three-level inversion image data (in days) from January to December in 2018 at 0.041 6°×0.041 6° to construct a DCEC model, determined the optimal number of clusters based on the Davies-Bouldi index (DBI), and extracted the category feature value (FM) of each month’s sea surface temperature (SST); we used monthly 1°×1° bigeye tuna longline fishery data from January to December in 2018 generated from the Indian Ocean Tuna Commission (IOTC), and calculated the catch per unit effort (CPUE); we matched the monthly category feature value FM and the monthly average value of Chl a concentration with the CPUE data to construct an improved GAM; we matched the monthly average SST, the monthly average Chl a concentration and CPUE data to build a basic GAM; we used the joint hypothesis test (F test) to verify the influence of model explanatory variables; we used akaike information criterion (AIC), mean square error (MSE), and draw the frequency distribution diagrams and box diagrams of measured and predicted values, etc., to analysis the improvement effect of the improved GAM compared to the basic GAM. The results showed that: (1) the category feature value (FM) extracted based on the DCEC model could better reflect the temporal and spatial dynamic characteristics of SST in the Southwest Indian Ocean, and was related with the climatic conditions, monsoon conditions, and hydrological characteristics in the Southwest Indian Ocean; (2) the factor interpretation of FM was higher than that of the monthly average SST in GAM, which means FM had more significant impact on the CPUE of bigeye tuna. The high catch rate was concentrated in the areas where the FM category was 2, 10, 24 with intersections between the warm and cold currents; (3) the AIC of the improved GAM was reduced by 9.17% than that of the basic GAM and MSE of the improved GAM was reduced by 26.7% than that of the basic GAM; the frequency distribution of the CPUE logarithmic value predicted by the improved GAM was closer to the normal distribution, and the high frequency distribution interval was closer to that of the measured value; the scatter plot showed that the CPUE predicted by the improved GAM had a significant correlation with the measured CPUE, with r equaled to 0.60. This study proves the effectiveness of the DCEC model in extracting marine environmental features, and can provide a reference for the further study on the bigeye tuna fishery forecast.
In order to improve the forecasting ability of the fishery forecast model for the longline bigeye tuna (Thunnus obesus), we proposed a marine environment feature extraction method based on deep convolutional embedded clustering (DCEC), combined with generalized additive model (GAM) for forecasting the longline bigeye tuna fishing grounds in the Southwest Indian Ocean. We used the MODIS-Aqua and MODIS-Terra sea surface temperature (SST) three-level inversion image data (in days) from January to December in 2018 at 0.041 6°×0.041 6° to construct a DCEC model, determined the optimal number of clusters based on the Davies-Bouldi index (DBI), and extracted the category feature value (FM) of each month’s sea surface temperature (SST); we used monthly 1°×1° bigeye tuna longline fishery data from January to December in 2018 generated from the Indian Ocean Tuna Commission (IOTC), and calculated the catch per unit effort (CPUE); we matched the monthly category feature value FM and the monthly average value of Chl a concentration with the CPUE data to construct an improved GAM; we matched the monthly average SST, the monthly average Chl a concentration and CPUE data to build a basic GAM; we used the joint hypothesis test (F test) to verify the influence of model explanatory variables; we used akaike information criterion (AIC), mean square error (MSE), and draw the frequency distribution diagrams and box diagrams of measured and predicted values, etc., to analysis the improvement effect of the improved GAM compared to the basic GAM. The results showed that: (1) the category feature value (FM) extracted based on the DCEC model could better reflect the temporal and spatial dynamic characteristics of SST in the Southwest Indian Ocean, and was related with the climatic conditions, monsoon conditions, and hydrological characteristics in the Southwest Indian Ocean; (2) the factor interpretation of FM was higher than that of the monthly average SST in GAM, which means FM had more significant impact on the CPUE of bigeye tuna. The high catch rate was concentrated in the areas where the FM category was 2, 10, 24 with intersections between the warm and cold currents; (3) the AIC of the improved GAM was reduced by 9.17% than that of the basic GAM and MSE of the improved GAM was reduced by 26.7% than that of the basic GAM; the frequency distribution of the CPUE logarithmic value predicted by the improved GAM was closer to the normal distribution, and the high frequency distribution interval was closer to that of the measured value; the scatter plot showed that the CPUE predicted by the improved GAM had a significant correlation with the measured CPUE, with r equaled to 0.60. This study proves the effectiveness of the DCEC model in extracting marine environmental features, and can provide a reference for the further study on the bigeye tuna fishery forecast.
2021, 43(8): 118-127.
doi: 10.12284/hyxb2021104
Abstract:
The sustainable utilization of fishery resources is the basis of resources exploitation. Based on the statistical data of catches in the East Indian Ocean from 1950 to 2018 provided by the food and agriculture organization of the united nations, and combined with the trophic level (TL) of relevant fish species provided by Fishbase, the changes of mean trophic level (MTL) and fishing-in-balance (FiB) index of catch in the East Indian Ocean during 69 years, so as to determine the sustainable utilization of fishery resources in the Eastern Indian Ocean were discussed in this paper. The results showed that the catches in the East Indian Ocean showed a steady increasing trend from 1950 to 2018. The catches of Tenualosa ilisha, Clupea pallasi and Rastrelliger kanagurta were the important catch species in the East Indian Ocean from 1950 to 2018, and their cumulative annual yield accounted for more than 10% of the total catch. The variation of MTL could be divided into three stages: from 1950 to 1974, the MTL was high and its value range was 3.39−3.71 with the average of 3.60±0.07, the annual catch showed a steady increase trend, the average annual growth rate was 6.4%; from 1975 to 1999 the annual MTL fluctuated from 3.21 to 3.51 with an average of 3.35±0.08, the annual catch showed a small and steady increase trend, the average annual growth rate was 4.8%; during 2000 to 2018, the annual MTL from 2000 to 2018 was 3.31−3.43, with an average of 3.38±0.03, and the annual catch showed a slow and steady increasing trend, with an average annual growth rate of 1.6%. The mean FiB index of the three stages was 0.59±0.22, 0.94±0.14 and 1.25±0.04, respectively. The value of FiB index showed a steady increasing trend and the range of annual variation was smaller, which indicated that the community structure in the East Indian Ocean was becoming more and more stable. The degree of development and utilization of fishery resources increased, while the decline in MTL was small, and the FiB index showed an upward trend, indicating that the increase in fish catches could make up for the decrease of MTL; and when only populations with TL greater than 3.25 were counted, the average MTL values of 1950−1974, 1975−1999, and 2000−2018 were 4.16±0.04, 4.18±0.04, and 4.19±0.03, respectively, showing a small and stable increase trend, indicating that the fishery resources of the high-trophic population were not damaged. It is concluded that the marine ecosystem of East Indian Ocean is stable and the fishery resources are under-exploited.
The sustainable utilization of fishery resources is the basis of resources exploitation. Based on the statistical data of catches in the East Indian Ocean from 1950 to 2018 provided by the food and agriculture organization of the united nations, and combined with the trophic level (TL) of relevant fish species provided by Fishbase, the changes of mean trophic level (MTL) and fishing-in-balance (FiB) index of catch in the East Indian Ocean during 69 years, so as to determine the sustainable utilization of fishery resources in the Eastern Indian Ocean were discussed in this paper. The results showed that the catches in the East Indian Ocean showed a steady increasing trend from 1950 to 2018. The catches of Tenualosa ilisha, Clupea pallasi and Rastrelliger kanagurta were the important catch species in the East Indian Ocean from 1950 to 2018, and their cumulative annual yield accounted for more than 10% of the total catch. The variation of MTL could be divided into three stages: from 1950 to 1974, the MTL was high and its value range was 3.39−3.71 with the average of 3.60±0.07, the annual catch showed a steady increase trend, the average annual growth rate was 6.4%; from 1975 to 1999 the annual MTL fluctuated from 3.21 to 3.51 with an average of 3.35±0.08, the annual catch showed a small and steady increase trend, the average annual growth rate was 4.8%; during 2000 to 2018, the annual MTL from 2000 to 2018 was 3.31−3.43, with an average of 3.38±0.03, and the annual catch showed a slow and steady increasing trend, with an average annual growth rate of 1.6%. The mean FiB index of the three stages was 0.59±0.22, 0.94±0.14 and 1.25±0.04, respectively. The value of FiB index showed a steady increasing trend and the range of annual variation was smaller, which indicated that the community structure in the East Indian Ocean was becoming more and more stable. The degree of development and utilization of fishery resources increased, while the decline in MTL was small, and the FiB index showed an upward trend, indicating that the increase in fish catches could make up for the decrease of MTL; and when only populations with TL greater than 3.25 were counted, the average MTL values of 1950−1974, 1975−1999, and 2000−2018 were 4.16±0.04, 4.18±0.04, and 4.19±0.03, respectively, showing a small and stable increase trend, indicating that the fishery resources of the high-trophic population were not damaged. It is concluded that the marine ecosystem of East Indian Ocean is stable and the fishery resources are under-exploited.
2021, 43(8): 128-138.
doi: 10.12284/hyxb2021126
Abstract:
In this study, histological observation of gonadogenesis, gonadal differentiation and first annual gonadal development in cobia (Rachycentron canadum) was performed based on paraffin section and H.E. staining method. The results of histological observations showed that the primordial germ cells (PGCs) arrived at the genital ridge at 7 dph (days post hatching), then the somatic cells began to aggregate around the PGCs. At 15 dph, the PGCs were enclosed entirely by somatic cells and formed the primary gonad. Two types of primary gonads with noticeable histological differences could be observed at 34 dph. The presence of clusters of oogonia characterized a part of primary gonads. The other primary gonads showed a narrower cross-section with fewer germ cells, which were presumed to be undifferentiated testis. Similar to other fishes, ovarian differentiation of cobia was anterior to testicular differentiation. The anatomical indication of ovarian differentiation was the ovarian cavity formation, which occurred at 44 dph. The cytological differentiation of testis began at about 50 dph and was characterized by the presence of spermatogonial acinar-clusters. The first annual development of testes could be divided into five stages (I, II, III, IV, V), while the development of the ovaries was divided into three stages (I, II, III). Testes and ovaries were both developed to early Stage I at 60 dph. All of the testes developed to Stage II at 90 dph; the ovaries were still at Stage I. More than half of the testes developed to Stage III and part of the ovaries developed to Stage II at 120 dph. The testes were mainly developed to Stage III at 150 dph; most of the ovaries were at Stage II. The testes were still at stage III, and the ovaries were developed to Stage II at 185 dph. Most of the testes developed to Stage IV at 210 dph, but the ovaries were still at Stage II. At 360 dph, the testes entered Stage V, and most of the ovaries developed to Stage III. These findings could clarify gonadal development characteristics and provide a theoretical basis for the artificial breeding of cobia.
In this study, histological observation of gonadogenesis, gonadal differentiation and first annual gonadal development in cobia (Rachycentron canadum) was performed based on paraffin section and H.E. staining method. The results of histological observations showed that the primordial germ cells (PGCs) arrived at the genital ridge at 7 dph (days post hatching), then the somatic cells began to aggregate around the PGCs. At 15 dph, the PGCs were enclosed entirely by somatic cells and formed the primary gonad. Two types of primary gonads with noticeable histological differences could be observed at 34 dph. The presence of clusters of oogonia characterized a part of primary gonads. The other primary gonads showed a narrower cross-section with fewer germ cells, which were presumed to be undifferentiated testis. Similar to other fishes, ovarian differentiation of cobia was anterior to testicular differentiation. The anatomical indication of ovarian differentiation was the ovarian cavity formation, which occurred at 44 dph. The cytological differentiation of testis began at about 50 dph and was characterized by the presence of spermatogonial acinar-clusters. The first annual development of testes could be divided into five stages (I, II, III, IV, V), while the development of the ovaries was divided into three stages (I, II, III). Testes and ovaries were both developed to early Stage I at 60 dph. All of the testes developed to Stage II at 90 dph; the ovaries were still at Stage I. More than half of the testes developed to Stage III and part of the ovaries developed to Stage II at 120 dph. The testes were mainly developed to Stage III at 150 dph; most of the ovaries were at Stage II. The testes were still at stage III, and the ovaries were developed to Stage II at 185 dph. Most of the testes developed to Stage IV at 210 dph, but the ovaries were still at Stage II. At 360 dph, the testes entered Stage V, and most of the ovaries developed to Stage III. These findings could clarify gonadal development characteristics and provide a theoretical basis for the artificial breeding of cobia.
2021, 43(8): 139-151.
doi: 10.12284/hyxb2021060
Abstract:
In this study, marine nematode samples were collected from Dalian Xiajiahezi Beach near the Bohai Sea and Dalian Golden Beach near the Yellow Sea in December 2015, and the community structure and diversity characteristics of marine nematodes in two sandy intertidal zones were studied. The results showed that there were significant differences in the abundance, dominant species, trophic structure and diversity of marine nematodes at the two beaches. The average abundance of marine nematodes were (592.0±318.9) ind./(10 cm2) in the Xiajiahezi Beach, and (54.6±53.8) ind./(10 cm2 ) in the Golden Beach, which was significantly lower than that in the Xiajiahezi Beach. A total of 43 species of marine nematodes were identified, and 13 common species. The dominant species of marine nematodes in the Xiajiahezi Beach were Daptonema sp.1, Daptonema sp.2, Theristus sp.1, Setosabatieria sp.1, Prochromadorella sp.1, Daptonema sp.3, Paracyatholaimus sp.1, Sabatieria breviseta, which were mainly non-selective sedimenous nematodes. The dominant species in the Golden Beach were Oncholaimus sp.1 Chromadorita sp.1, Theristus sp.2, Neochromadora sp.1, Enoplus sp.1, Prochromadorella sp.1, which were mainly omnivorous or predatory nematodes. There were significant differences in species number (S), Margalef’s species richness (d) and Shannon–Wiener index(H′) between the two sandy beaches, and the values were significantly higher in the Xijiahezi Beach than the Golden Beach. The Analysis of Similarity tests (ANOSIM) results showed that there were significant differences in marine nematodes community structure between the two beaches. Interstitial water temperature and median diameter (MDΦ) were the main environmental factors that cause differences in marine nematode community structure and diversity. The characteristics of the marine nematodes community in the Xijiahezi Beach were also different among different tidal zones due to the variations of sediment granularity and pH. The diversity of marine nematodes in low tidal zone was higher than that in high and mid tidal zones, and the abundance of omnivores and predators was higher, which reflected the complex structure of the marine nematodes community. In the Golden Beach, there was no significant difference in environmental factors in different tidal zones, and the difference in nematodes community structure and diversity of tidal areas was not significant and relatively uniform. In addition, hydrodynamic force function was also an important factor that causes differences in marine nematode community structures at the studied beaches. On the one hand, hydrodynamic force affected the community characteristics of marine nematodes by influencing the deposition of sediments with different particle sizes. On the other hand, hydrodynamic force could affect the dispersity of nematodes which in turn affects their tidal distribution.
In this study, marine nematode samples were collected from Dalian Xiajiahezi Beach near the Bohai Sea and Dalian Golden Beach near the Yellow Sea in December 2015, and the community structure and diversity characteristics of marine nematodes in two sandy intertidal zones were studied. The results showed that there were significant differences in the abundance, dominant species, trophic structure and diversity of marine nematodes at the two beaches. The average abundance of marine nematodes were (592.0±318.9) ind./(10 cm2) in the Xiajiahezi Beach, and (54.6±53.8) ind./(10 cm2 ) in the Golden Beach, which was significantly lower than that in the Xiajiahezi Beach. A total of 43 species of marine nematodes were identified, and 13 common species. The dominant species of marine nematodes in the Xiajiahezi Beach were Daptonema sp.1, Daptonema sp.2, Theristus sp.1, Setosabatieria sp.1, Prochromadorella sp.1, Daptonema sp.3, Paracyatholaimus sp.1, Sabatieria breviseta, which were mainly non-selective sedimenous nematodes. The dominant species in the Golden Beach were Oncholaimus sp.1 Chromadorita sp.1, Theristus sp.2, Neochromadora sp.1, Enoplus sp.1, Prochromadorella sp.1, which were mainly omnivorous or predatory nematodes. There were significant differences in species number (S), Margalef’s species richness (d) and Shannon–Wiener index(H′) between the two sandy beaches, and the values were significantly higher in the Xijiahezi Beach than the Golden Beach. The Analysis of Similarity tests (ANOSIM) results showed that there were significant differences in marine nematodes community structure between the two beaches. Interstitial water temperature and median diameter (MDΦ) were the main environmental factors that cause differences in marine nematode community structure and diversity. The characteristics of the marine nematodes community in the Xijiahezi Beach were also different among different tidal zones due to the variations of sediment granularity and pH. The diversity of marine nematodes in low tidal zone was higher than that in high and mid tidal zones, and the abundance of omnivores and predators was higher, which reflected the complex structure of the marine nematodes community. In the Golden Beach, there was no significant difference in environmental factors in different tidal zones, and the difference in nematodes community structure and diversity of tidal areas was not significant and relatively uniform. In addition, hydrodynamic force function was also an important factor that causes differences in marine nematode community structures at the studied beaches. On the one hand, hydrodynamic force affected the community characteristics of marine nematodes by influencing the deposition of sediments with different particle sizes. On the other hand, hydrodynamic force could affect the dispersity of nematodes which in turn affects their tidal distribution.
2021, 43(8): 152-159.
doi: 10.12284/hyxb2021132
Abstract:
Water flow is an important environmental factor that affects whether barnacles, oysters, algae, and other aquatic organisms can successfully attach to fishing equipment. Changes in water velocity will change the metabolism of algae and restrict the spread of barnacles and oyster larvae. The accuracy of the flow velocity data plays a vital role in studying the attachment mechanism of organisms attached to fishery equipment. Acoustic Doppler Velocimetry (ADV) is an important device for measuring the flow velocity. However, factors such as bubbles and large suspended solids in the water will affect the correlation coefficient and signal-to-noise ratio of ADV, resulting in outliers in the flow velocity data and reducing the accuracy of the data. Based on the domestic and foreign mainstream algorithms—robust estimation method and the three-dimensional phase space thresholding method, actual measured flow velocity data of ADV are taken as an example to compare and study the detection effects of the two post-processing methods. The results showed that the average detection rate of the robust estimation method was 4.95%, the kurtosis coefficient decreased by 77.71%, the average detection rate of the three-dimensional phase space thresholding method was 14.60%, and the kurtosis coefficient decreased by 84.05%. Comprehensive analysis showed that the three-dimensional phase space thresholding method had a better processing effect, and its detection accuracy was higher than that of the robust estimation method, but there was a phenomenon of overprocessing. It was recommended that the three-dimensional phase space thresholding method be used when dealing with data with an outlier content of less than 5%, and for data whose outliers deviate from the sample average, the robust estimation method was recommended. This article is of great significance for reducing the error of flow velocity data and accurately and quantitatively studying the influence of water flow on the attachment amount and types of fishery equipment attached organisms. It also provides a scientific basis for the subsequent development of a post-processing algorithm with high detection accuracy and less overprocessing.
Water flow is an important environmental factor that affects whether barnacles, oysters, algae, and other aquatic organisms can successfully attach to fishing equipment. Changes in water velocity will change the metabolism of algae and restrict the spread of barnacles and oyster larvae. The accuracy of the flow velocity data plays a vital role in studying the attachment mechanism of organisms attached to fishery equipment. Acoustic Doppler Velocimetry (ADV) is an important device for measuring the flow velocity. However, factors such as bubbles and large suspended solids in the water will affect the correlation coefficient and signal-to-noise ratio of ADV, resulting in outliers in the flow velocity data and reducing the accuracy of the data. Based on the domestic and foreign mainstream algorithms—robust estimation method and the three-dimensional phase space thresholding method, actual measured flow velocity data of ADV are taken as an example to compare and study the detection effects of the two post-processing methods. The results showed that the average detection rate of the robust estimation method was 4.95%, the kurtosis coefficient decreased by 77.71%, the average detection rate of the three-dimensional phase space thresholding method was 14.60%, and the kurtosis coefficient decreased by 84.05%. Comprehensive analysis showed that the three-dimensional phase space thresholding method had a better processing effect, and its detection accuracy was higher than that of the robust estimation method, but there was a phenomenon of overprocessing. It was recommended that the three-dimensional phase space thresholding method be used when dealing with data with an outlier content of less than 5%, and for data whose outliers deviate from the sample average, the robust estimation method was recommended. This article is of great significance for reducing the error of flow velocity data and accurately and quantitatively studying the influence of water flow on the attachment amount and types of fishery equipment attached organisms. It also provides a scientific basis for the subsequent development of a post-processing algorithm with high detection accuracy and less overprocessing.
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