2024 Vol. 46, No. 7
Display Method:
2024, 46(7): 1-15.
doi: 10.12284/hyxb2024036
Abstract:
This study uses the data of the China’s new generation geostationary-orbit meteorological satellite FY-4B to observe the internal solitary wave (ISW) and study the propagation speed of ISW in the northern South China Sea (NSCS). Firstly, the observable ISW region of the FY-4B satellite was discussed by using ARGI data of 500 m resolution, and the NSCS was confirmed as the research area. Then, the MTI method (Multitemporal Image Comparison method) was used to calculate the propagation velocity of ISWs in NSCS using GHI data of 250 m resolution, and the average propagation velocity of ISW in NSCS is about 1.78 m/s. The average velocity in the eastern deep sea was 3.02 m/s, and it decreased to 1.90 m/s after westward transmission near Dongsha Islands. After the division of Dongsha Islands, the velocity of ISW in the south was faster than the north, with 2.08 m/s and 1.54 m/s, respectively. Finally, the velocity decreases to 0.42 m/s after westward to the nearshore region, then dissipates. Compared with the results of the MTI method and theoretical propagation velocity calculated by the eKdV (extended Korteweg-de Vries) equation in the two-layer mode, and the correlation coefficient between them reached 0.89. Prove the feasibility of using the eKdV theoretical equation to invert the propagation velocity of ISW in the NSCS. Finally, the results of calculating the propagation velocity of ISW by combining measured data with remote sensing images were compared with the results of MTI method. The correlation between the two reached 0.93. This article verifies the high temporal resolution characteristics of geostationary-orbit optical remote sensing data, which have significant advantages in calculating the propagation speed of ISW. It has certain significance for research work such as inversion of ISW parameters in the NSCS.
This study uses the data of the China’s new generation geostationary-orbit meteorological satellite FY-4B to observe the internal solitary wave (ISW) and study the propagation speed of ISW in the northern South China Sea (NSCS). Firstly, the observable ISW region of the FY-4B satellite was discussed by using ARGI data of 500 m resolution, and the NSCS was confirmed as the research area. Then, the MTI method (Multitemporal Image Comparison method) was used to calculate the propagation velocity of ISWs in NSCS using GHI data of 250 m resolution, and the average propagation velocity of ISW in NSCS is about 1.78 m/s. The average velocity in the eastern deep sea was 3.02 m/s, and it decreased to 1.90 m/s after westward transmission near Dongsha Islands. After the division of Dongsha Islands, the velocity of ISW in the south was faster than the north, with 2.08 m/s and 1.54 m/s, respectively. Finally, the velocity decreases to 0.42 m/s after westward to the nearshore region, then dissipates. Compared with the results of the MTI method and theoretical propagation velocity calculated by the eKdV (extended Korteweg-de Vries) equation in the two-layer mode, and the correlation coefficient between them reached 0.89. Prove the feasibility of using the eKdV theoretical equation to invert the propagation velocity of ISW in the NSCS. Finally, the results of calculating the propagation velocity of ISW by combining measured data with remote sensing images were compared with the results of MTI method. The correlation between the two reached 0.93. This article verifies the high temporal resolution characteristics of geostationary-orbit optical remote sensing data, which have significant advantages in calculating the propagation speed of ISW. It has certain significance for research work such as inversion of ISW parameters in the NSCS.
2024, 46(7): 16-28.
doi: 10.12284/hyxb2024062
Abstract:
Digital bathymetric models (DBMs) are important basic geographic information data in the fields of offshore engineering construction, resource development, environmental protection and so on. The existing global public DBMs products such as GEBCO (The General Bathymetric Chart of the Oceans), SRTM (The Shuttle Radar Topography Mission) and ETOPO (Earth Topography) have different data types, data sources and product accuracy in different sea areas. In order to reconstruct China’s offshore bathymetric model using global bathymetric data and DBMs products, this paper proposed a weighted fusion reconstruction framework based on bathymetric partition. Firstly, the reliability and applicability of six commonly used DBMs products (GEBCO_2022, SRTM30_PLUS, SRTM15_V2.5.5, TOPO_25.1, DTU10, ETOPO_2022) were compared and analyzed in five dimensions (overall accuracy, different water depths, route profiles, geographical partitions, local details). Then, considering the bathymetric and topographic characteristics, the study area was segmented and partitioned, and the optimal DBMs products in the partition were selected, and the optimal weighted fusion was carried out with the minimum error as the constraint. Finally, the fusion results were processed by measured value recovery, smooth filtering and other post-processing to form a high-precision seamless bathymetric model with 15" resolution in offshore waters around China’s coastline. The results showed that the RMSE of the fusion results was reduced by 27%, 14%, 14% and 13% compared with SRTM30_PLUS, GEBCO_2022, SRTM15_V2.5.5 and ETOPO_2022, and the details of the topograhy were also retained. The feasibility of the fusion framework was proved, which could provide a reference for the fusion reconstruction and timely updating of large-scale seabed topography from multiple datasets.
Digital bathymetric models (DBMs) are important basic geographic information data in the fields of offshore engineering construction, resource development, environmental protection and so on. The existing global public DBMs products such as GEBCO (The General Bathymetric Chart of the Oceans), SRTM (The Shuttle Radar Topography Mission) and ETOPO (Earth Topography) have different data types, data sources and product accuracy in different sea areas. In order to reconstruct China’s offshore bathymetric model using global bathymetric data and DBMs products, this paper proposed a weighted fusion reconstruction framework based on bathymetric partition. Firstly, the reliability and applicability of six commonly used DBMs products (GEBCO_2022, SRTM30_PLUS, SRTM15_V2.5.5, TOPO_25.1, DTU10, ETOPO_2022) were compared and analyzed in five dimensions (overall accuracy, different water depths, route profiles, geographical partitions, local details). Then, considering the bathymetric and topographic characteristics, the study area was segmented and partitioned, and the optimal DBMs products in the partition were selected, and the optimal weighted fusion was carried out with the minimum error as the constraint. Finally, the fusion results were processed by measured value recovery, smooth filtering and other post-processing to form a high-precision seamless bathymetric model with 15" resolution in offshore waters around China’s coastline. The results showed that the RMSE of the fusion results was reduced by 27%, 14%, 14% and 13% compared with SRTM30_PLUS, GEBCO_2022, SRTM15_V2.5.5 and ETOPO_2022, and the details of the topograhy were also retained. The feasibility of the fusion framework was proved, which could provide a reference for the fusion reconstruction and timely updating of large-scale seabed topography from multiple datasets.
2024, 46(7): 29-40.
doi: 10.12284/hyxb2024068
Abstract:
Typhoons can have serious impacts on tidal flat ecosystems, particularly on the composition and distribution of macrobenthic communities. However, there is a lack of field data during typhoons, and the understanding of how typhoons affect the ecosystem is still limited. Therefore, this study conducted hydrodynamic observations and synchronous sampling of macrobenthic organisms before, during, and after Typhoon “Muifa”in September 2022, along the salt marsh-mudflat transect in the Chongming Dongtan area of the Changjiang River estuary. The study found: (1) During Typhoon “Muifa”, the effective wave height in the salt marshes was 2−4 times that of normal weather, and the combined wave-current shear stress was 10 times higher. (2) Within a week after Typhoon “Muifa”, the species number, abundance, and biomass of macrobenthic organisms in the salt marshes were 1.9, 3.8, and 3.0 times higher than before the typhoon, respectively. The dominant species of the salt marsh (Ilyoplax deschampsi, Assiminea sp., Assiminea violacea, Corbicula fluminea) increased by one (Assiminea violacea) compared with that before the typhoon (Assiminea sp., Ilyoplax deschampsi, Corbicula fluminea), and the primary dominant species shifting from Assiminea sp. to Ilyoplax deschampsi. (3) Within a week after Typhoon “Muifa”, the indicators of species number, abundance, and biomass of macrobenthos in the salt marsh increased, while the abundance of macrobenthic organisms on the mudflats at the forefront of the salt marsh decreased. This is attributed to the macrobenthic organisms (Ilyoplax deschampsi, Assiminea sp., Corbicula fluminea) on the mudflats migrating rapidly to the relatively less hydrodynamically stressed salt marshes during the strong hydrodynamic stress caused by the typhoon. (4) Two weeks after Typhoon “Muifa”, the abundance of macrobenthos in salt marshes recovered. The results of this study indicate that salt marsh vegetation not only provides ecological services such as wave attenuation, flow reduction, and shoreline protection, but also serves as a refuge for macrobenthic organisms during typhoons.
Typhoons can have serious impacts on tidal flat ecosystems, particularly on the composition and distribution of macrobenthic communities. However, there is a lack of field data during typhoons, and the understanding of how typhoons affect the ecosystem is still limited. Therefore, this study conducted hydrodynamic observations and synchronous sampling of macrobenthic organisms before, during, and after Typhoon “Muifa”in September 2022, along the salt marsh-mudflat transect in the Chongming Dongtan area of the Changjiang River estuary. The study found: (1) During Typhoon “Muifa”, the effective wave height in the salt marshes was 2−4 times that of normal weather, and the combined wave-current shear stress was 10 times higher. (2) Within a week after Typhoon “Muifa”, the species number, abundance, and biomass of macrobenthic organisms in the salt marshes were 1.9, 3.8, and 3.0 times higher than before the typhoon, respectively. The dominant species of the salt marsh (Ilyoplax deschampsi, Assiminea sp., Assiminea violacea, Corbicula fluminea) increased by one (Assiminea violacea) compared with that before the typhoon (Assiminea sp., Ilyoplax deschampsi, Corbicula fluminea), and the primary dominant species shifting from Assiminea sp. to Ilyoplax deschampsi. (3) Within a week after Typhoon “Muifa”, the indicators of species number, abundance, and biomass of macrobenthos in the salt marsh increased, while the abundance of macrobenthic organisms on the mudflats at the forefront of the salt marsh decreased. This is attributed to the macrobenthic organisms (Ilyoplax deschampsi, Assiminea sp., Corbicula fluminea) on the mudflats migrating rapidly to the relatively less hydrodynamically stressed salt marshes during the strong hydrodynamic stress caused by the typhoon. (4) Two weeks after Typhoon “Muifa”, the abundance of macrobenthos in salt marshes recovered. The results of this study indicate that salt marsh vegetation not only provides ecological services such as wave attenuation, flow reduction, and shoreline protection, but also serves as a refuge for macrobenthic organisms during typhoons.
2024, 46(7): 41-50.
doi: 10.12284/hyxb2024078
Abstract:
Dosidicus gigas is an oceanic economic fish in the offshore waters of Peru, and its abundance is greatly affected by environmental factors. This study obtained the abundance of D. gigas through fishing logs from September to December in 2018−2021, combined with environmental factors, including surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH) and chlorophyll a concentration (Chl a) acquired from satellite remote sensing. Random forest model and ArcGIS were applied to analyze the correlations between the abundance of D. gigas and environmental factors. Results showed that the distribution of the center of gravity of fishing ground was concentrated in the range of 13°−21°S, 76°−87°W during 2018−2021, and the center of gravity shifted from northwest to the southeast from September to December. The results of random forest model analysis showed that, the impact of environmental factors on the abundance and distribution of D. gigas in the offshore waters of Peru varied among different months. The optimal SST ranged from 16.3℃ to 18.5℃, The optimal SSS ranged from 35.1 to 35.4, the optimal SSH ranged from 0.55 m to 0.60 m, the optimal Chla concentration ranged from 0.18 mg/m3 to 0.46 mg/m3. The predicted CPUE values derived from the random forest model were generally consistent with the nominal CPUE distribution, indicating the suitability of the random forest model for analyzing the relationship between D. gigas and environmental factors in the offshore waters of Peru. This study is of great significance for understanding the resource dynamics of D. gigas and guiding its production.
Dosidicus gigas is an oceanic economic fish in the offshore waters of Peru, and its abundance is greatly affected by environmental factors. This study obtained the abundance of D. gigas through fishing logs from September to December in 2018−2021, combined with environmental factors, including surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH) and chlorophyll a concentration (Chl a) acquired from satellite remote sensing. Random forest model and ArcGIS were applied to analyze the correlations between the abundance of D. gigas and environmental factors. Results showed that the distribution of the center of gravity of fishing ground was concentrated in the range of 13°−21°S, 76°−87°W during 2018−2021, and the center of gravity shifted from northwest to the southeast from September to December. The results of random forest model analysis showed that, the impact of environmental factors on the abundance and distribution of D. gigas in the offshore waters of Peru varied among different months. The optimal SST ranged from 16.3℃ to 18.5℃, The optimal SSS ranged from 35.1 to 35.4, the optimal SSH ranged from 0.55 m to 0.60 m, the optimal Chla concentration ranged from 0.18 mg/m3 to 0.46 mg/m3. The predicted CPUE values derived from the random forest model were generally consistent with the nominal CPUE distribution, indicating the suitability of the random forest model for analyzing the relationship between D. gigas and environmental factors in the offshore waters of Peru. This study is of great significance for understanding the resource dynamics of D. gigas and guiding its production.
2024, 46(7): 51-61.
doi: 10.12284/hyxb2024084
Abstract:
In order to explore the differences in the structural characteristics of macrobenthos communities in different artificial reefs in the Yellow Sea and Bohai Sea and to evaluate the conservation effect of artificial reefs on biological resources, a simultaneous survey of macrobenthos in four artificial reefs in the Yellow Sea and Bohai Sea was carried out in autumn 2021. A total of 61 macrobenthos species were collected, among which annelids accounted for the most (47.54%). The biomass of macrobenthos in each reef area was higher than that in the control area, and the conservation effect of macrobenthos resources in the old reef area was the best, and the average biomass was 4.19 times that of the control area. The Shannon-Wiener index H' and richness index d of each reef region were higher than those of the control region, and the long reef age region was higher than the short reef age region. The ABC curve shows that the stability of the community in the long-aged reefs is better than that in the short-aged reefs. There are different dominant species in each artificial reef area, but polychaetes are the dominant species in all artificial reef areas. Reef survey sites were roughly divided into 3 groups by cluster analysis and non-metric multidimensional scale ranking (NMDS). Similarity analysis test (ANOSIM) showed that there were significant differences in community structure among reefs (R = 0.651, p < 0.01). The results of SIMPER (percentage of similarity analysis) show that the average percentage of dissimilarity in each reef interval is above 77%. The results show that the artificial reef habitat plays a certain role in the conservation of macrobenthos, and the macrobenthos community varies in different reef regions. This study can provide basic data and basis for the evaluation of artificial reef construction.
In order to explore the differences in the structural characteristics of macrobenthos communities in different artificial reefs in the Yellow Sea and Bohai Sea and to evaluate the conservation effect of artificial reefs on biological resources, a simultaneous survey of macrobenthos in four artificial reefs in the Yellow Sea and Bohai Sea was carried out in autumn 2021. A total of 61 macrobenthos species were collected, among which annelids accounted for the most (47.54%). The biomass of macrobenthos in each reef area was higher than that in the control area, and the conservation effect of macrobenthos resources in the old reef area was the best, and the average biomass was 4.19 times that of the control area. The Shannon-Wiener index H' and richness index d of each reef region were higher than those of the control region, and the long reef age region was higher than the short reef age region. The ABC curve shows that the stability of the community in the long-aged reefs is better than that in the short-aged reefs. There are different dominant species in each artificial reef area, but polychaetes are the dominant species in all artificial reef areas. Reef survey sites were roughly divided into 3 groups by cluster analysis and non-metric multidimensional scale ranking (NMDS). Similarity analysis test (ANOSIM) showed that there were significant differences in community structure among reefs (R = 0.651, p < 0.01). The results of SIMPER (percentage of similarity analysis) show that the average percentage of dissimilarity in each reef interval is above 77%. The results show that the artificial reef habitat plays a certain role in the conservation of macrobenthos, and the macrobenthos community varies in different reef regions. This study can provide basic data and basis for the evaluation of artificial reef construction.
2024, 46(7): 62-72.
doi: 10.12284/hyxb2024080
Abstract:
Yellowfin tuna (Thunnus albacares) and skipjack tuna (Katsuwonus pelamis) are pelagic and highly migratory species, serving as primary targets in global pelagic fisheries. Their population distribution and abundance are susceptible to the impacts of climate-induced changes in the marine environment, exhibiting a response lag. In order to explore the influence of climate change on the juvenile populations of yellowfin tuna and skipjack tuna in the western and central Pacific Ocean (WCPO) and the associated lag effects, this study, based on Long Short-Term Memory (LSTM) neural networks, analyzed the impact of the Oceanic Niño index (ONI) on the Catch per Unit Effort (CPUE) of yellowfin tuna and skipjack tuna in the WCPO purse seine fishery from 1982 to 2021. Different time step lengths were employed to simulate the lag effects (0−12 months) of CPUE response to ONI. The results indicate LSTM is a suitable tool for analyzing the lag effects of relationship between the abundance of pelagic species, such as yellowfin tuna and skipjack tuna, and environmental factors like ONI. In the WCPO regions north and south of the equator, there exists a time lag in the response of juvenile yellowfin tuna and skipjack tuna CPUE to ONI, with the optimal lag period being 12 months for each region. The correspondence of the optimal lag period with the age of the harvested population (nearly 1 year) suggests that the reproductive capacity or survival rate of juvenile yellowfin tuna and skipjack tuna is influenced by climate change and the resulting changes in the marine environment. The research methodology and results provide new insights for subsequent studies in analyzing the stock dynamics and distribution of key species in the WCPO.
Yellowfin tuna (Thunnus albacares) and skipjack tuna (Katsuwonus pelamis) are pelagic and highly migratory species, serving as primary targets in global pelagic fisheries. Their population distribution and abundance are susceptible to the impacts of climate-induced changes in the marine environment, exhibiting a response lag. In order to explore the influence of climate change on the juvenile populations of yellowfin tuna and skipjack tuna in the western and central Pacific Ocean (WCPO) and the associated lag effects, this study, based on Long Short-Term Memory (LSTM) neural networks, analyzed the impact of the Oceanic Niño index (ONI) on the Catch per Unit Effort (CPUE) of yellowfin tuna and skipjack tuna in the WCPO purse seine fishery from 1982 to 2021. Different time step lengths were employed to simulate the lag effects (0−12 months) of CPUE response to ONI. The results indicate LSTM is a suitable tool for analyzing the lag effects of relationship between the abundance of pelagic species, such as yellowfin tuna and skipjack tuna, and environmental factors like ONI. In the WCPO regions north and south of the equator, there exists a time lag in the response of juvenile yellowfin tuna and skipjack tuna CPUE to ONI, with the optimal lag period being 12 months for each region. The correspondence of the optimal lag period with the age of the harvested population (nearly 1 year) suggests that the reproductive capacity or survival rate of juvenile yellowfin tuna and skipjack tuna is influenced by climate change and the resulting changes in the marine environment. The research methodology and results provide new insights for subsequent studies in analyzing the stock dynamics and distribution of key species in the WCPO.
2024, 46(7): 73-87.
doi: 10.12284/hyxb2024086
Abstract:
The crown-of-thorns starfish (CoTS) outbreak has caused severe damage to coral reefs in China and the Indo-Pacific region. Fish predators have been considered as an important factor in controlling the population outbreak, but there is a lack of research on the fish that can prey on crown-of-thorns starfish in China. By collecting coral reef fish from five outbreak areas of crown-of-thorns starfish in the Xisha Islands, CoTS DNA was detectedin the intestinal contents of the reef fish using PCR technology, and which compared with reported CoTS larval predators. The results showed that a total of 62 fish belonging to 23 families, 36 genera and 50 species were captured in this survey. CoTS DNA was detected in the gut contents of four fish species, namely Naso lituratus, Dascyllus reticulatus, Chelilinus trilobatus and Lethrinus erythropterus. Among them, N. lituratus, C. trilobatus and L. erythropterusare reported for the first time as potential predators of CoTS. This study has identified the potential predators of CoTS for the first time in China, providing important references for the development of early prevention and control techniques for crown-of-thorns starfish.
The crown-of-thorns starfish (CoTS) outbreak has caused severe damage to coral reefs in China and the Indo-Pacific region. Fish predators have been considered as an important factor in controlling the population outbreak, but there is a lack of research on the fish that can prey on crown-of-thorns starfish in China. By collecting coral reef fish from five outbreak areas of crown-of-thorns starfish in the Xisha Islands, CoTS DNA was detectedin the intestinal contents of the reef fish using PCR technology, and which compared with reported CoTS larval predators. The results showed that a total of 62 fish belonging to 23 families, 36 genera and 50 species were captured in this survey. CoTS DNA was detected in the gut contents of four fish species, namely Naso lituratus, Dascyllus reticulatus, Chelilinus trilobatus and Lethrinus erythropterus. Among them, N. lituratus, C. trilobatus and L. erythropterusare reported for the first time as potential predators of CoTS. This study has identified the potential predators of CoTS for the first time in China, providing important references for the development of early prevention and control techniques for crown-of-thorns starfish.
2024, 46(7): 88-99.
doi: 10.12284/hyxb2024108
Abstract:
Biodiversity serves as a crucial biological foundation for ecosystem stability. This study aimed to investigate the biodiversity of the southeast Pacific and its response to marine environmental conditions through analyzing Zeta diversity in equatorial waters, and offshores of Ecuador and Peru based on species data from the AquaMaps database. This study also examined the biodiversity indices, including Margalef index, Shannon-Wiener index and Pielou index, and evaluated the relationships between these biodiversity indices and marine environment factors by using mixed-effects models. The results revealed that there were a total of 118 species commonly recorded across the three study areas, with fish being the predominant species group. Analysis of Zeta diversity revealed that the average compositional similarity was 24.00 species in the Equatorial waters, 18.00 species off the coast of Ecuador and 12.00 species offshore of Peru. The Zeta ratio notably increased from Zeta order 2 to Zeta order 5 across the study areas, stabilizing thereafter. The biodiversity indices were calculated as follows: in the equatorial waters the Margalef index was 13.34 ± 3.56, the Shannon-Wiener index was 3.80 ± 0.25, and the Pielou index was 0.61 ± 0.01. In the offshore of Ecuador, the indices were 37.58 ± 36.49 for the Margalef index, 4.67 ± 0.92 for the Shannon-Wiener index, and 0.63 ± 0.02 for the Pielou index. In the offshore of Peru, the indices were 22.83 ± 18.95 for the Margalef index, 4.22 ± 0.76 for the Shannon-Wiener index, and 0.62 ± 0.02 for the Pielou index. Significant differences were observed in sea surface temperature, salinity, chlorophyll a concentration, and mixed layer depth between the equatorial waters, and offshores of Ecuador and Peru. The biodiversity indices showed significant negative correlations with sea surface temperature and salinity, but the effects from chlorophyll a concentration and mixed layer depth were not determined. The study suggests that the species composition in the equatorial water, and offshores of Ecuador and Peru in the southeast Pacific is predominated by fish, and biodiversity varied spatially, with the highest biodiversity indices recorded in the offshore of Ecuador.
Biodiversity serves as a crucial biological foundation for ecosystem stability. This study aimed to investigate the biodiversity of the southeast Pacific and its response to marine environmental conditions through analyzing Zeta diversity in equatorial waters, and offshores of Ecuador and Peru based on species data from the AquaMaps database. This study also examined the biodiversity indices, including Margalef index, Shannon-Wiener index and Pielou index, and evaluated the relationships between these biodiversity indices and marine environment factors by using mixed-effects models. The results revealed that there were a total of 118 species commonly recorded across the three study areas, with fish being the predominant species group. Analysis of Zeta diversity revealed that the average compositional similarity was 24.00 species in the Equatorial waters, 18.00 species off the coast of Ecuador and 12.00 species offshore of Peru. The Zeta ratio notably increased from Zeta order 2 to Zeta order 5 across the study areas, stabilizing thereafter. The biodiversity indices were calculated as follows: in the equatorial waters the Margalef index was 13.34 ± 3.56, the Shannon-Wiener index was 3.80 ± 0.25, and the Pielou index was 0.61 ± 0.01. In the offshore of Ecuador, the indices were 37.58 ± 36.49 for the Margalef index, 4.67 ± 0.92 for the Shannon-Wiener index, and 0.63 ± 0.02 for the Pielou index. In the offshore of Peru, the indices were 22.83 ± 18.95 for the Margalef index, 4.22 ± 0.76 for the Shannon-Wiener index, and 0.62 ± 0.02 for the Pielou index. Significant differences were observed in sea surface temperature, salinity, chlorophyll a concentration, and mixed layer depth between the equatorial waters, and offshores of Ecuador and Peru. The biodiversity indices showed significant negative correlations with sea surface temperature and salinity, but the effects from chlorophyll a concentration and mixed layer depth were not determined. The study suggests that the species composition in the equatorial water, and offshores of Ecuador and Peru in the southeast Pacific is predominated by fish, and biodiversity varied spatially, with the highest biodiversity indices recorded in the offshore of Ecuador.
2024, 46(7): 100-109.
doi: 10.12284/hyxb2024098
Abstract:
The albacore tuna (Thunnus alalunga) is an oceanic migratory fish species, whose fishing ground distribution is linked to various environmental factors. Based on the longline fishing logs of albacore tuna in the south Pacific from 2016 to 2021, oceanic remote sensing data including the Southern Oscillation Index (SOI), Sea Surface Temperature (SST), Chlorophyll-a (CHLA) concentration and Dissolved Oxygen (DO) concentration were utilized. With spatiotemporal and environmental factors as input layer and catch per unit effort (CPUE) as output layer, a genetic algorithm (GA) was utilized to optimize the structure of a 9-13-1 BP neural network. CPUE standardization was carried out for albacore based on GA-BP neural network to investigate the spatiotemporal variation and influencing factors on the abundance of albacore tuna resources. The model evaluation results indicated that the GA-BP neural network had better effect than the BP neural network. Predictive analysis showed that SST and DO concentration were the primary environmental factors influencing the shifts in the core area of albacore tuna fishing grounds, with the most productive fishing areas having SSTs between 18℃ and 20℃, and DO concentration levels above 210 mmol/m³. The predicted and actual center of gravity for fishing grounds largely coincided, and the standardized CPUE trends over time were generally consistent with nominal CPUE. The research has demonstrated that the utilization of GA-BP neural networks can effectively predict the distribution of fishing grounds for albacore tuna, providing a reference basis for tuna fishery production and management.
The albacore tuna (Thunnus alalunga) is an oceanic migratory fish species, whose fishing ground distribution is linked to various environmental factors. Based on the longline fishing logs of albacore tuna in the south Pacific from 2016 to 2021, oceanic remote sensing data including the Southern Oscillation Index (SOI), Sea Surface Temperature (SST), Chlorophyll-a (CHLA) concentration and Dissolved Oxygen (DO) concentration were utilized. With spatiotemporal and environmental factors as input layer and catch per unit effort (CPUE) as output layer, a genetic algorithm (GA) was utilized to optimize the structure of a 9-13-1 BP neural network. CPUE standardization was carried out for albacore based on GA-BP neural network to investigate the spatiotemporal variation and influencing factors on the abundance of albacore tuna resources. The model evaluation results indicated that the GA-BP neural network had better effect than the BP neural network. Predictive analysis showed that SST and DO concentration were the primary environmental factors influencing the shifts in the core area of albacore tuna fishing grounds, with the most productive fishing areas having SSTs between 18℃ and 20℃, and DO concentration levels above 210 mmol/m³. The predicted and actual center of gravity for fishing grounds largely coincided, and the standardized CPUE trends over time were generally consistent with nominal CPUE. The research has demonstrated that the utilization of GA-BP neural networks can effectively predict the distribution of fishing grounds for albacore tuna, providing a reference basis for tuna fishery production and management.
2024, 46(7): 110-119.
doi: 10.12284/hyxb2024088
Abstract:
In the field of aquaculture, a comprehensive exploration of the growth and developmental mechanisms of Mytilus coruscus lays the theoretical foundation for molecular regulation of growth and development. In order to investigate the expression patterns of genes associated with the growth and development differences in M. coruscus larvae, this study employed transcriptome sequencing and real-time quantitative PCR analysis techniques, conducting a preliminary examination of the differential expression of genes and molecular pathways related to growth characteristics. The research places particular emphasis on the impact and regulatory roles of the mammalian target of rapamycin (mTOR) signaling pathway in the growth and development of M. coruscus larvae. By analyzing the gene expression patterns at different developmental stages (Trochophore larvae stage, D-veliger larvae stage, Veliconcha larvae stage, Pediveliger larvae stage, and Juvenile stage), the results suggest that the mTOR signaling pathway may play a specific role in the growth and development of M. coruscus larvae. Seven key genes associated with growth were successfully identified. As the developmental process progresses, the expression of genes in the mTOR signaling pathway exhibits dynamic changes across different developmental stages. Among these changes, the expression levels of the PI3K, TSCI/2, and mTOR genes initially increased, followed by a decrease, and subsequently rose again. In contrast, IGFI expression exhibited an initial increase followed by a decline. Meanwhile, the expression of EIF4B, RPS6KB, and AKT genes demonstrated an overall downward trend. This differential gene expression pattern reflects the potential regulatory influence of the mTOR signaling pathway on cell fate and biological functions during various developmental stages of M. coruscus larvae, thereby impacting their growth and development. Therefore, this study provides a preliminary exploration of the expression patterns of key genes in the mTOR signaling pathway during the growth and development of M. coruscus larvae. These genes play a crucial role in regulating the molecular functions and growth characteristics of M. coruscus larvae, offering foundational data for a deeper understanding of the physiological adaptation, metabolic processes, and growth variations in marine bivalves.
In the field of aquaculture, a comprehensive exploration of the growth and developmental mechanisms of Mytilus coruscus lays the theoretical foundation for molecular regulation of growth and development. In order to investigate the expression patterns of genes associated with the growth and development differences in M. coruscus larvae, this study employed transcriptome sequencing and real-time quantitative PCR analysis techniques, conducting a preliminary examination of the differential expression of genes and molecular pathways related to growth characteristics. The research places particular emphasis on the impact and regulatory roles of the mammalian target of rapamycin (mTOR) signaling pathway in the growth and development of M. coruscus larvae. By analyzing the gene expression patterns at different developmental stages (Trochophore larvae stage, D-veliger larvae stage, Veliconcha larvae stage, Pediveliger larvae stage, and Juvenile stage), the results suggest that the mTOR signaling pathway may play a specific role in the growth and development of M. coruscus larvae. Seven key genes associated with growth were successfully identified. As the developmental process progresses, the expression of genes in the mTOR signaling pathway exhibits dynamic changes across different developmental stages. Among these changes, the expression levels of the PI3K, TSCI/2, and mTOR genes initially increased, followed by a decrease, and subsequently rose again. In contrast, IGFI expression exhibited an initial increase followed by a decline. Meanwhile, the expression of EIF4B, RPS6KB, and AKT genes demonstrated an overall downward trend. This differential gene expression pattern reflects the potential regulatory influence of the mTOR signaling pathway on cell fate and biological functions during various developmental stages of M. coruscus larvae, thereby impacting their growth and development. Therefore, this study provides a preliminary exploration of the expression patterns of key genes in the mTOR signaling pathway during the growth and development of M. coruscus larvae. These genes play a crucial role in regulating the molecular functions and growth characteristics of M. coruscus larvae, offering foundational data for a deeper understanding of the physiological adaptation, metabolic processes, and growth variations in marine bivalves.
2024, 46(7): 120-130.
doi: 10.12284/hyxb2024060
Abstract:
The concentrations of dissolved manganese (dMn) in the Zhujiang Estuary-Qiongdong Sea area in October 2017 and the northeast-central part of the South China Sea (SCS) in September 2020 (the research areas are referred to as the northern South China Sea, NSCS) were determined by online concentration-flow injection analysis. The results showed that the concentration of dMn in the NSCS ranged from 0.7 nmol/L to 8.6 nmol/L, with an average of (2.6 ± 1.3) nmol/L. The concentration of dMn was higher in the coastal area and decreased with distance from the coast, dMn in the Zhujiang Estuary-Qiongdong Sea area was higher than that in the northern and central of the SCS. The vertical profiles of dMn normally was highest in the surface layer, gradually decreased with depth and increased dMn in the intermediate water with relatively low dissolved oxygen, and then kept low concentration in the deep water. The factors affecting the distribution of dMn in the NSCS mainly include water mass mixing, particulate adsorption-desorption and regeneration in low oxygen environment etc. Mn-rich shelf water was transported to the slope of NSCS along the upper layer (< 80 m). Using salinity and dMn as tracer to study the intrusion of Kuroshio subsurface water (KSSW) into the SCS in autumn 2020, the results showed that the KSSW intrusion was mainly concentrated at the potential density surfaces of 24.5～25.0 kg/m3, and the intrusion scope extending to 117.5°E in the west and 20°N in the south. The concentration of dMn in the intermediate water of the central SCS (400～1 500 m, DO < 100 μmol/L) increased, and the concentration of dMn was positively correlated with apparent oxygen consumption (AOU), which indicated that remineralization process in low oxygen environment (DO < 100 μmol/L) affected the distribution of dMn in the NSCS.
The concentrations of dissolved manganese (dMn) in the Zhujiang Estuary-Qiongdong Sea area in October 2017 and the northeast-central part of the South China Sea (SCS) in September 2020 (the research areas are referred to as the northern South China Sea, NSCS) were determined by online concentration-flow injection analysis. The results showed that the concentration of dMn in the NSCS ranged from 0.7 nmol/L to 8.6 nmol/L, with an average of (2.6 ± 1.3) nmol/L. The concentration of dMn was higher in the coastal area and decreased with distance from the coast, dMn in the Zhujiang Estuary-Qiongdong Sea area was higher than that in the northern and central of the SCS. The vertical profiles of dMn normally was highest in the surface layer, gradually decreased with depth and increased dMn in the intermediate water with relatively low dissolved oxygen, and then kept low concentration in the deep water. The factors affecting the distribution of dMn in the NSCS mainly include water mass mixing, particulate adsorption-desorption and regeneration in low oxygen environment etc. Mn-rich shelf water was transported to the slope of NSCS along the upper layer (< 80 m). Using salinity and dMn as tracer to study the intrusion of Kuroshio subsurface water (KSSW) into the SCS in autumn 2020, the results showed that the KSSW intrusion was mainly concentrated at the potential density surfaces of 24.5～25.0 kg/m3, and the intrusion scope extending to 117.5°E in the west and 20°N in the south. The concentration of dMn in the intermediate water of the central SCS (400～1 500 m, DO < 100 μmol/L) increased, and the concentration of dMn was positively correlated with apparent oxygen consumption (AOU), which indicated that remineralization process in low oxygen environment (DO < 100 μmol/L) affected the distribution of dMn in the NSCS.
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