Fishery Forecast Research Of The Sthenoteuthis Oualaniensis In The Open South China Sea Based On Marine Environmental Factors

The South China Sea,also known as the South China Sea,has a vast sea area with a total area of 3.5 million square kilometers,of which the sea area within the traditional boundary of our country is about 2 million square kilometers and the open seas area is more than 1.4 million square kilometers.The South China Sea is the only tropical ocean in China,with a unique marine environment and rich biodiversity.Among them,there are more than 25,000 fish species,and the annual catch can reach7 million tons.In recent years,the South China Sea offshore overfishing,fishery resources decline,while the open seas are rich in cephalopods and tuna resources.Therefore,vigorously developing the open South China Sea fisheries is one of the effective ways to shift the pressure of offshore fishery production,reduce fishing intensity,conserve offshore fishery resources,and ensure green sustainable development of the ocean.Sthenoteuthis oualaniensis is an ocean cephalopod and abundant resources in the South China Sea.According to the survey and evaluation of the South China Sea Fisheries Research Institute of the Chinese Academy of Fishery Sciences,the catch of catfish in the South China Sea in 2014-2017 was over 4 million tons,and the catch in 2018 was over 5 million tons.At present,the annual catch of sthenoteuthis oualaniensis in China is only 100,000 tons,which is obviously in an undeveloped state.It can be seen that the development potential of the sthenoteuthis oualaniensis resources in the South China Sea is huge.sthenoteuthis oualaniensis is rich in various nutrient elements and is an extremely high-quality,high-protein,low-fat aquatic product with great economic value.Because the habitat of the sthenoteuthis oualaniensis is greatly affected by the sea surface temperature and the distribution of bait,changes in its habitat environment directly affect its distribution and yield.Therefore,it is important to strengthen the research on the influence of habitat factors on the fishing ground of sthenoteuthis oualaniensis.However,due to the problems and challenges of high fishery production cost,low level of fishing technology,and lack of fishery forecast information in the open South China Sea,so far,the open South China Sea has not established a relatively complete fishery forecast system.Therefore,using the habitat suitability index(HSI)model to study the fishing status of sthenoteuthis oualaniensis can accurately predict the migratory activity of the sthenoteuthis oualaniensis and the distribution of fishing grounds,and provide a scientific basis for the sustainable production of sthenoteuthis oualaniensis in the open South China Sea.This article selects the fishery data of the Sthenoteuthis Oualaniensis in the open South China Sea from the large-scale light falling-net fishing vessels in Beihai,Guangxi Zhuang Autonomous Region in 2013-2018.First,a generalized linear model(GLM)is used to test the significance of each selected environmental factor to screen for significant variables.Second,a generalized additive model(GAM)is used to standardize the nominal CPUE.Then,the abundance of the sthenoteuthis oualaniensis fishery resource abundance was characterized by the CPUE standardized by the generalized additive model,and the fishery forecast of the sthenoteuthis oualaniensis in the open South China Sea was studied and analyzed.According to the fishery data of the Sthenoteuthis Oualaniensis in the open South China Sea from the large-scale light falling-net fishing vessels in Beihai,Guangxi Zhuang Autonomous Region in 2013-2018 And the data of the South China Sea marine environment from January to December 2013-2018,the spatial-temporal distribution and habitat factors[SST、chla and SSH]the relationship of the sthenoteuthis oualaniensis fishing ground was studied.The results show that the more suitable operation ranges of SST,chla and SSH of the sthenoteuthis oualaniensis fishing ground from 1 to 12 in the sea areas of 4oN-24oN,104oE-124oE are:25-31℃,0.05-0.27mg/m~3,46-80cm.Through K-S test,the results showed that P>0.05,indicating that the sthenoteuthis oualaniensis range of SST,SSH,and chla for each month was used as data that could represent the distribution and quality of the sthenoteuthis oualaniensis fishing ground.In the HSI model,the weightings of each habitat factor represents the proportion of the impact on the formation and distribution of the sthenoteuthis oualaniensis fishing ground.Establish adaptive models based on sea surface temperature(SST),sea surface height(SSH),and sea surface chlorophyll a concentration(chla)to assign different weight coefficients a,b,and c,formula:a+b+c=1,using Weighted geometric mean method,arithmetic mean method,minimum method and maximum method to establish HSI model.The HSI model was tested using the fishery data of sthenoteuthis oualaniensis from the large-scale light falling-net fishing vessels in Beihai,Guangxi Zhuang Autonomous Region in 2018-2019.The results showed that the HSI model based on the arithmetic mean method had the best simulation results,with an accuracy rate of more than 80%.When the January SST,chla,SSH weight coefficients are 1,0,0;February SST,chla,SSH weight coefficients are 0.6,0.2,0.2;March SST,chla,SSH weight coefficients are 0.6,0.2,0.2;April SST,chla,SSH weight coefficients are 0.7,0.15,0.15,respectively;May SST,chla,SSH weight coefficients are 0.7,0.15,0.15,respectively;June SST,chla,SSH weight coefficients are 0.15,0.15,0.7;July SST,chla,SSH weight coefficients are 0.15,0.7,0.15,respectively;August SST,chla,SSH weight coefficients are 0.15,0.15,0.7;September SST,chla,SSH weight coefficients are 0,0,1;October SST,chla,SSH weight coefficients are 0.15,0.7,0.15,respectively;November SST,chla,SSH weight coefficients are 0.2,0.2,and 0.6;December SST,chla,SSH weight coefficients are 0.7,0.15,and 0.15,the model has the highest accuracy.The HSI value calculated from the January-December 2018-2019 period through the arithmetic average method HSI model with the best weight.combined with Arc GIS10.5 and the HSI value of each month as the base map,is superimposed with the CPUE from January to December 2018-2019.The graph shows that except for the points with higher CPUE in June,October,and December,which do not correspond to the areas with higher HSI,the points with higher CPUE in other months basically appear in areas with higher HSI.The monthly average CPUE and HSI The change trend is more consistent,and there is a certain positive correlation.The relationship between the two is obtained by fitting a univariate linear equation:CPUE=-3084.6759+6606.6423 HSI(P=0.0001,R~2=0.8142).By comparing the predicted value with the actual value,The relative error between the predicted value and the actual value in June is the largest,and it is basically the same in April,but the average relative error is 8.25%,so it can be judged that the model has higher accuracy.The three habitat factors of SST,chla,and SSH are used to establish the HSI The model can better predict the production of sthenoteuthis oualaniensis.