Study On The Spatial-temporal Distribution Of Antarctic Krill(Euphausia Superba) Fishing Ground And Their Influencing Factors

The Antarctic krill,also known as Antarctic krill(Euphausia superba),is living in the Southern Ocean in a crustacean zooplankton,is the key link in energy and material flows in the Southern Ocean ecosystem.Antarctic krill biomass is about 1 to 2 billion tons,the annual catch is also 150 million tons,which is equivalent to the sum of the world catches,is available and the largest potential for fisheries resources nowadays.Therefore,it is of great significance to explore the spatial-temporal distribution of Antarctic krill fishing ground and their relations to the influencing factors to the reasonable development and management of the Antarctic krill resources and to further improve the fishing efficiency of the Antarctic krill.In this study,according to the data on the catch of Antarctic krill in the Southern Ocean of 48 fishing area of China's large trawlers from 2010 to 2015;and combined with the Sea surface temperature(SST),concentration of Chlorophyll a(Chl-a)data obtained from the remote sensing method.By the Catch per unit of fishing effort(CPUE)as a resource abundance index,using mathematical statistical methods and the geographic information software ARCGIS analyze the spatialtemporal distribution of Antarctic krill fishing ground and their relations to the influencing factors and by generalized additive models(GAM)analyze the effect of influencing factors on the spatial-temporal distribution of Antarctic krill fishing ground.The results are as follows:60°S~64°S?40°W~61°W is a well operating area of Antarctic krill.Overall,there are distinct seasonal changes in the Antarctic krill CPUE,except for November,the rest of the month can catch.The lower of CPUE appears in December(10.7t/h),until May of the next year,the CPUE gradually increase.The CPUE reaches the highest value in May(20.9t/h),and then a decrease trend could be found from May to the October.The CPUE reaches the lowest value in September(4.5t/h).From December to October of the following year,the fishery center moves towards the east roughly,and from December to Febuary of the following year,the fishery center moves towards the south,the latitude center also expansion towards the south.From March to June,the longitude center of fishing ground continued to move towards the north and there is a small change in the latitude center,where mainly distributed in nearby 62°S.Moreover,From July to October,there is a huge change in the fishery center,it roughly moves to the northeast and gets to the easternmost and northernmost in August and September respectively.The range of suitable SST and Chl-a in Antarctic krill fishing ground is also changed with the month,the suitable SST in Antarctic krill fishing ground ranges from-0.5? to 1?,the suitable Chl-a ranges from 0.2 mg/m3 to 0.38 mg/m3.It was suggested that summer and autumn(from December to May in the next year)were the main fishing seasons due to the suitable SST and Chl-a.The Antarctic krill fishery mainly distributed in the surrounding waters of the Antarctic Peninsula and its adjacent islands and the Antarctic krill migrate back and forth along the extension of the continental shelf as the month change from 2010 to 2015.The significance order from big to small of the effects of all fishing factors chosen by GAM on the spatial and temporal distribution of CPUE is longitude,trawling speed,Chl-a,SST,length of warp,horizontal expansion of the net mouth,net mouth height,month,trawling depth,latitude.The accumulation of deviance explained of model to CPUE is 76.83%.The deviance explained of temporal factor(month)is 1.9%.The deviance explained of spatial factor is 16.79%,which the contribution rate of the longitude is 16.7%.The deviance explained of environmental factor(month)is 11.61%.The deviance explained of fishing factor(month)is 19.2%,which the trawling speed is the largest impact factor in the contribution rate,the deviation explained was 9.2%.The F test showed that the longitude,trawling speed,net mouth height,horizontal expansion of the net mouth is significantly related to the CPUE(P < 0.05),while other factors have little to do with the CPUE of the Antarctic krill.Overall,the suitable values of the longitude in Antarctic krill fishing range from 47°W to 61°W.The suitable values of the trawling speed in Antarctic krill fishing range from 2.5Kn to 3.5Kn.The suitable values of the net mouth height in Antarctic krill fishing range from 25 m to 35 m.The suitable values of the horizontal expansion of the net mouth in Antarctic krill fishing range from 20 m to 30 m.