Study On The Characteristics Of Antarctic Krill Fishery And Its Relationship With Marine Environmental Factors

Under the background of global fishery resources decline,Antarctic krill(Euphausia superba),as a high-quality animal protein source,has become an important target species of Marine fishery worldwide due to its huge biological resources.The exploitation of Antarctic krill resources began in the 1970s.Since2014,China has gradually absorbed foreign technology to participate in the exploitation of Antarctic krill resources.However,China’s krill trawling fishery is currently facing problems such as old fishing boats,low domestic production rate of nets and weak grasp of fishing grounds.It is of great significance to understand the change of krill resources in The Antarctic,to master the response mechanism of krill resources population to the change of sea conditions in the fishery,and to explore the formation mechanism of krill fishery,so as to improve the efficiency of fishery management and ensure the sustainable development of fishery in China.This study is based on the fishing log data of the 2013/2014-2019/2020 fishing season of the large trawler Long Teng,an Antarctic krill fishing vessel of China National Fisheries Corp.,combined with the measured fishery biological data and remote sensing observation data of the Marine environment.Statistical analysis methods such as ArcGIS 10.5 and Generalized Additive Model(GAM)were used.The relationship between the Catch per unit of effort(CPUE)and the main influencing factors of krill were studied.The results are as follows:During the postgraduate period,the author went to the Antarctic sea for two years on board the ship"Long Teng"as an Radio officer.During this period,I went deep into the production line,got familiar with the Antarctic krill fishing and management system and other relevant contents,and obtained a lot of first-hand information about the Antarctic krill,such as fishing logs,navigation logs,biological data and so on.(1)On the whole,the annual average CPUE of Antarctic krill showed an increasing trend,and the number of operations also increased gradually.The proportion of the monthly average CPUE and the number of operations per month has obvious seasonal variation,the proportion of the monthly average CPUE and the number of operations per month is higher in summer and autumn,and it decreases obviously in winter.In the fishing s~eason from 2013/2014 to 2019/2020,the annual average CPUE of Long Teng’s Antarctic krill showed an overall upward trend,which was relatively stable,with an overall average of 5.973T/10~6m~3.The months with the highest monthly CPUE values were concentrated in the Antarctic summer and autumn(December to May of the following year).The monthly AVERAGE CPUE value in September(1.450T/10~6m~3)was significantly lower than that in other operating months.The monthly average CPUE value was the highest in March(7.988T/10~6m~3),and continued to decrease in the following months.The trend of the line chart of the monthly average CPUE and the monthly operation ratio of Antarctic krill was similar,except for October and November,the production times accounted for the least in September,and the production times accounted for more than 75%in summer and autumn,when the monthly average CPUE of Antarctic krill was higher.Therefore,summer and autumn are the best seasons for krill.The body length of krill was mainly in the range of 30～38mm(M grade),accounting for 49%.When the body length increased,the corresponding operation times were about less.(2)The spatial and temporal distribution of the barycenter of Antarctic krkrus fishery was different in each subregion.The barycenter of Antarctic krkrus fishery shifted from the northeast tip of south Shetland Islands in 2015 to the narrow area between the Antarctic Peninsula and South Shetland Islands in the southwest direction.48.2 The center of gravity of fishing grounds in the region is located in the northwest of south Orkney Islands and relatively concentrated.48.3 The center of gravity of fishing area is distributed in the northeast sea of South Georgia Island,and the center of gravity of fishing area is close to the offshore distance.Longteng wheel in the fishing pole fishing season,except for two month in October,November never production operation,are made in other assignments,fisheries in the center of gravity difference is bigger,from each of the fishing season began in December to next march,fisheries centre of gravity is distributed in the area and 48.2 the 48.1 area,fishing season begins in 48.2 the main area of production,With the passage of time,the center of gravity of the fishery shifted to sub-area 48.1,and gradually shifted to sub-area 48.3 in June and July.Among them,December and June are special.December is the beginning of the fishing season,and only 48.2 sub-zone has been produced.(3)In spatial dimension,the distribution of Antarctic krill operating areas and CPUE in each subregion showed obvious spatial distribution pattern,mainly distributed in the Antarctic Peninsula and the waters around the islands.48.1 The operating area of sub-region is widely distributed,mainly around south Shetland Islands,and the area with high CPUE per unit of fishing area is concentrated in the narrow sea area between South Shetland Islands and the Antarctic Peninsula.48.2The operation area of sub-zone is concentrated,all distributed in the northern sea near the South Orkney Islands,and the CPUE high value area of unit fishing area is mainly located in the east.The operating area of subzone 48.3 is distributed along the northeast coast of South Georgia Island,and the CPUE value of unit fishing area close to the island is generally higher.(4)The SST ranges from-2℃to 2.5℃in the Antarctic krill fishing grounds,and the average SST ranges from-1.5℃to 1℃in the high CPUE region,indicating that krill resources are abundant in the sea areas with low water temperature.The sea surface salinity ranges from 33.8PSU to 34.8PSU,and the average sea surface salinity ranges from 34.4PSU to 34.8PSU in the region with high CPUE value.The sea surface height ranges from-2.5m to 0m,and the average CPUE high value area ranges from 2.5m to-2.0m,which is suitable for fishing operations.The chlorophyll-A concentration ranges from 0 mg/m~3to 4.0 mg/m~3,and the average CPUE high value range ranges from 0 mg/m~3to 2.0 mg/m~3,which is the ideal concentration of chlorophyll-A in fishing operations.(5)GAM model results show that:The effects of all factors on CPUE value in descending order were towing speed,towing depth,latitude,sea surface height,sea surface salinity,network port height,chlorophyll-A concentration,longitude,sea surface temperature and population temperature.The total interpretation error rate of all factors was 29.9%,and population temperature had significant influence on CPUE value(P<0.01).Longitude,sea surface salinity,sea surface temperature,network height,latitude,sea surface height,towed depth,trawl speed and chlorophyll-a had significant effects on CPUE(P<0.001).The optimum fishing range is 60°S～65°S,42°W～46°W.The suitable SST range is-2℃～2℃.The suitable sea surface salinity ranges from 34.4PSU to 34.7PSU.The suitable sea surface height ranges from-2.3m to-1.9m.The height of the network port ranges from 14m to 25m.The suitable towing speed range is 2kN～3kN;The temperature range of shrimp colony suitable for operation is-2℃～2℃.