Influence of Antarctic sea ice variation on abundance and spatial distribution of Argentine shortfin squid Illex argentinus in the southwest Atlantic Ocean

Antarctic sea ice vatiation can have direct or indirect effects on the environments and a variety of marine organisms. The Sea Ice Extent was considered as an index to indicate the changes in Antarctic sea ice, and in this study, its impacts on fishing ground of Argentine shortfin squid Illex argentinus in the Southwest Atlantic Ocean were explored. In this study, the catch per unit effort (CPUE) was used to indicate squid abundance, and we evaluated the influences of sea ice extent and sea water temperature at different depths on stock variations of I. argentinus, based on the fishery data from January to June during 2013-2018 obtained from the Chinese squid-jigging Science and Technology Group as well as the sea ice extent data and the sea water temperature data of 5 m, 55 m, 95 m and 195 m depth on the fishing ground. The results indicated that the catch, CPUE, sea ice extent, sea water temperature at different depths exhibited significant annual and monthly variations. The correlation analysis suggested that Antarctic sea ice extent was positively correlated with CPUE on an annual and monthly scale. Sea ice extent was negatively correlated with annual and monthly sea water temperature at the depth of 5 m, but was positively correlated with sea water temperature at the depth of 95 m. Based on the histogram analysis, the monthly suitable and the most preferred sea water temperature for I. argentinus were evaluated at different depths. Positive relationship was found between the monthly percentages of suitable temperature at different depths accounting for the whole fishing ground and the sea ice extent, suggesting that the sea ice extent would affect the proportions of suitable habitats at different depths and further affect the abundance of I. argentinus. Our findings indicated that sea ice extent would have significant impacts on sea water temperature at different depths, and would further affect the fishing ground distribution and also squid abundance.