Spatial And Temporal Variation Of Antarctic Krill Fishery In Waters Adjacent To The Antarctic Peninsula And Its Implication On Fishery Management

Antarctic krill is a key species in the Southern Ocean marine ecosystem,and its population changes may affect the stability of the whole ecosystem.For a long time,the trend of krill fisheries gradually shifting to FAO Area 48 and concentrating their distribution in local areas has triggered widespread concern about krill resources and the Antarctic ecosystem.However,the Southern Ocean marine environment is complex and there are many factors affecting the variability of the krill fishery,and there are many different perspectives on the drivers of the variability of the fishery.In this study,we analyzed the spatial and temporal variability of the Antarctic krill fishery and the characteristics of the marine environment of the fishing grounds in the Antarctic Peninsula,based on the production data of Antarctic krill fishing vessels and the marine environment data observed by satellite remote sensing in the region,and analyzed the environmental factors using a generalized additive model.A generalized additive mixed model(GAMM)was used to analyze the effects of environmental factors on krill production,CPUE and fishing effort.Subsequently,the effects of sea ice on the fishability of the Antarctic krill fishery were analyzed based on the model results.The results of the study are as follows:(1)The krill fishery in the waters around the Antarctic Peninsula is characterized by interannual and seasonal variations.2010—2021,the center of gravity of the krill fishery gradually shifts southward from the western South Shetland Islands to the Bransfield Strait;the krill fishery is mainly distributed in the western South Shetland Islands during the summer(December-February)and in the Bransfield Strait during the fall and winter(MarchJune).(2)The results of GAMM analysis showed that sea surface temperature had a significant effect on krill fishery and CPUE distribution in both summer and fall/winter.The optimum water temperature of the krill fishery varied with seasonal changes,and the optimum water temperature of the fishery in autumn and winter was lower than that in summer.The optimum chlorophyll a concentration in summer was 0—0.6 mg/m3,and the chlorophyll a concentration was positively correlated with krill production and CPUE in this range,while there was no significant relationship between chlorophyll a concentration and fishing vessel operation time.Among the bottom topography factors,bottom depth,depth variation magnitude and slope significantly affected the distribution of krill resources and fishing grounds,with bottom depth less than 1000m,krill production in autumn and winter,CPUE in summer and fishing vessel operating hours showed negative correlations with bottom depth.In the slope range of 0—2.5°,the slope was negatively correlated with krill production in autumn and winter and positively correlated with CPUE.(3)Sea ice concentration in the waters around the Antarctic Peninsula has shown a decreasing trend over the last 30 years,and the ice free period in the waters within Bransfield Strait was extended to May at the beginning of the 21 st century,which is consistent with the seasonal variation characteristics of krill fishing vessels.2010—2021,the sea ice concentration in Bransfield Strait showed a decreasing trend from March to May,accompanied by a decrease in sea ice concentration is accompanied by a significant increase in the krill catch within Bransfield Strait and its share of the catch in subarea 48.1.During this period,sea ice concentration in Bransfield Strait was low and the krill fishery was concentrated in this area.In June,sea ice concentration increased and the focus of the fishery and the location of operations shifted to the area of low sea ice concentration,where the sea ice concentration of fishing vessels did not exceed 30%,and the length of operations gradually increased with the decrease in sea ice concentration.(4)Changes in the marine environment,fishing grounds,and fishery distribution have brought new challenges to the management of Antarctic krill fisheries.In order to better conserve krill resources and manage krill fisheries,the development of new fisheries management mechanisms for Antarctic krill should take into account environmental changes and fishing vessel behavioral tendencies in the context of rapid climate change.Krill fishery management should also encourage scientific research and studies to strengthen data collection around management and conservation needs,and should further expand the coverage of acoustic surveys to include fishing hotspots where acoustic surveys have not yet been conducted,in addition to the role of environmental data collected on site by fishing vessels,and continuously update environmental information on fishing grounds in order to provide sufficient data support for studying the possible impacts of climate change.