Research And Application Of The Electronic Fishing Logs Correction Of Lighting Cover Net Vessels In The Open Sea Of South China Sea

The South China Sea,the largest landward sea in the country,covers an area of about 3.5 million square kilometres.The South China Sea has huge reserves of fishery resources and is one of the traditional operating fishing grounds of Chinese fishermen,and is also the richest sea area in terms of fishery resources among the four major sea areas of China.In recent years,with the intensification of overfishing of inshore fisheries,there has been a shift towards further exploitation of the rich fishery resources off the South China Sea.Light cover net is a new fishing gear fishing method developed rapidly in the early 1990 s,mainly catching phototropic pelagic fish and cephalopods,representing species such as Sthenoteuthis oualaniensis,Auxis thazard,Auxis tapeinosoma,and Decapterus macarellus,etc.Due to its simple operation,high catch,good production efficiency and stable operation,it has become one of the main fishing operations in the open sea of South China Sea.Fisheries data is the basis for conducting fisheries science research,and its accuracy directly affects the accuracy of the research results.The traditional paper fishing logbook is the main source of fisheries data,which only roughly records the operating time,operating location,catch type and catch amount of fishermen during their trips to the sea.The use of paper fishing logbooks to collect data not only requires huge human and material resources,and paper materials are easy to lose and damage,inconvenient management,and query statistics are difficult,low utilization rate,it is difficult to provide data support for fisheries management and production.Electronic fishing logbook is the use of Beidou wireless transmission terminal and other electronic devices to collect relevant fishing vessel dynamics and information data such as catches,with the advantages of easy to fill out with easy to fill out,comprehensive coverage of different fishing areas,easy to save and query,not easy to lose and damage,high utilization rate.However,because the electronic fishing logbook collection process is vulnerable to other factors,mainly including natural factors(sea conditions,weather,etc.)and human factors(crew literacy,responsibility,etc.),these factors may lead to the existence of misreporting and omission of electronic fishing logbook data.Therefore,it is also necessary to further improve the accuracy of electronic fishing logbooks to facilitate systematic and accurate grasp of the actual and changing conditions of fisheries production and promote fisheries management and development.In this paper,the 2017 Bei Dou vessel position data and fishing logbook data and2020 Bei Dou vessel position data and electronic fishing logbook data were selected.Firstly,based on the 2017 Beidou vessel position data,the multi-layer filtering method was used to determine the operation status of the light-covered nets fishing vessels,and on this basis,the isobath method was used to extract the operation voyage,operation date,operation duration and operation position of the fishing vessels,and the corresponding fishing logbook data were compared to judge the accuracy of Beidou vessel position data extraction.The results show that the error between the extraction results of Beidou vessel position data and the results of fishing logs actually recorded by fishermen is small,the accuracy rate of voyage is 100%,the accuracy rate of voyage days is 94.30%;the accuracy rate of the same operation date is 92.72%;the total average absolute error of operation duration is 1.12 h,and the average relative error is2.1%,which has good consistency.The operating hours of lighted cover net fishing vessels were extracted using 2020 Beidou vessel position data and compared with the operating hours data recorded in electronic fishing logbooks for analysis.The operation duration was extracted by applying the Bei Dou vessel position data,and the operation duration recorded in the electronic fishing log was corrected,and the correction models based on linear regression and BP neural network for the electronic fishing log operation duration data were established respectively,and finally the effect evaluation of the corrected electronic fishing log operation duration data was carried out.The results show that the average error between the operation duration of Bei Dou vessel position data extraction and the operation duration of electronic fishing logbook records is 1.98 h,which needs to be corrected..The accuracy of the models constructed by both methods was improved after correction of the electronic fishing log operation hours data,and the average relative errors were reduced by 10.37% and 10.44%,respectively,and the BP neural network method was more effective.The BP neural network model was used to calibrate the electronic fishing log data of lighted hooded nets fishing vessels in 2020,and the statistical analysis of lighted hooded nets fishing vessels off the South China Sea was carried out,and finally the fishing volume of lighted hooded nets fishing vessels off the South China Sea was estimated.