Extraction Of Ocean Eddy And Its Relationship With The Distribution Of Ommastrephes Bartrami In The Northwest Pacific

The Northwest Pacific is located in the subtropical zone.It is an important sea area for large-scale commercial fishing by ocean-going fishing vessels in China.The high temperature,salinity Kuroshio intersect with the low temperature,salinity Oyashio.The sea conditions are complex.It is the active area of mesoscale eddy.The ocean eddy affects the momentum,heat,salinity,and large-scale flux of the air-sea system,and plays an important role in various physical and biochemical processes of the ocean.Previous studies have proven that the resources of Ommastrephes fishing ground and the position of Ommastrephes fishing are easily affected by the marine environment.Eddy has the above-mentioned many attributes in spatial distribution and structure.Its continuous movement is accompanied by upwelling and downflow,which can affect the transportation of marine materials and the mixing of seawater,and has special significance for the formation and change of fish fishing grounds.Ommastrephes bartramii is an important fish fishing object inhabiting this area in China.The correlation between the mesoscale eddy in the Northwest Pacific and the distribution of Ommastrephes bartramii fishing grounds is studied to reveal the distribution of fishing grounds with vortices and improve China's fishery resources.And the study of this correlation is to reduce the cost of fishing operations and improve the fishing efficiency of Ommastrephes bartramii fisheries.The study of mesoscale eddy extraction method is important to the analysis of eddy and fishing grounds.Therefore,this paper used sea surface height anomaly data to determine the eddy boundaries and centers based on the closed-line method without thresholds,and extracted the irregular vector eddies of the Kuroshio Extension in the Northwest Pacific Ocean.In order to prove the superiority of the results of this paper,the extraction results are compared with the raster maps of the original sea surface height anomaly data and the extraction results of the standard circular eddy in the traditional research method in the same study area at the same time.For analyzing the influence of the Northwest Pacific eddy on the distribution of Ommastrephes bartrami,the Kernel Density method was used to statistically analyze the spatial distribution of the core of the eddy and the position of the fishing ground with the data of Ommastrephes bartrami from the Northwest Pacific from 2005 to 2014.It extracted eddy cores and boundaries with irregular vector eddy extraction method in the same study area at the same time.The geospatial data overlay method was used to analyze the correlation between the mesoscale eddy attributes and the Ommastrephes bartrami fishing ground,build an eddy and fishing ground relationship database,statistically analyze the fishing ground position information,and analyze the relationship between the eddy and the fishing ground distribution based on the GAM model.It strived to find a quantitative relationship between eddy and fishing ground to improve the fishing efficiency of the Ommastrephes bartrami fishing.The findings are as follows:(1)It compared the eddy extraction results of June 1,1994,the original sea surface height anomaly data raster map,as well as the result of the standard circle in traditional research methods in the same study area at the same time in an eddy extraction method based on an ocean satellite altimeter.The eddy at the same position was enlarged in the same proportion.And the overlap rate was calculated.The maximum overlap rate is 100%,the minimum value is 58%,and the average overlap rate is 81%.It is more in line with the actual shape and position of the eddy in the ocean by fully considering the characteristics of the irregular shape of the ocean eddy,and integrating the advantages of the vector data structure.The method in this paper is suitable for the study of the relationship between eddies and fishing grounds was more accurate and easier than the traditional methods.(2)According to the results of Kernel Density method,the core of cold and warm eddy distributions were relatively high in June,July,August,September,and October,and the density became significantly smaller in November.However,the density peaks of the warm eddy were mostly located in west of 150 ° E.They were mostly located north of 40°N in June,July,August,and September,comparing with October,November.According to the results of statistical analysis of fishing site location,it was inferred that the fishing points with high catch around the cold eddy which may be located at the boundary of the cold eddy and inside the cold eddy.(3)According to the analysis results of the GAM model,the optimum eddy's amplitude range of the warm eddy occurrence fishing ground was 0.07 ? 0.08 km,the shortest distance between the optimal fishing ground fishing point and the eddy boundary was 50 ? 150 km.The shortest distance from the most suitable fishing ground to the eddy core was 100 ? 200 km.The core of the warm eddy closest to the fishing ground fishing point was more related to the fishing ground fishing point in the north.The optimum eddy's amplitude range of cold eddy were 0.07 ? 0.08 m and 0.1 ? 0.12 m.The shortest distance between the optimum fishing ground and the eddy boundary was 0 ? 180 km.The shortest distance between the optimal fishing ground and the eddy core were 100 ? 150 km,250 ? 320 km.The core of the cold eddy closest to the fishing ground fishing point was more closely related to the fishing ground fishing point in the southwest direction.The reason for this phenomenon may be the structural characteristics of the eddy,the transport of the eddy to seawater and the entrainment of living things.