Effects of mesoscale eddies and sea ice on trawl-survey CPUE ofEuphausia superba in Scotia Sea

Driven by the Antarctic Circumpolar Current, the Scotia Sea is characterized by frequent mesoscale eddy activity and is one of the most active eddy regions in the Southern Ocean. Antarctic krill (Euphausia superba), a key species in the polar ecosystem, is highly concentrated in this sea area, forming one of the world’s most important commercial fishing grounds. However, the regulatory mechanism of mesoscale dynamic processes and sea ice conditions on the spatial distribution of krill resources remains unclear. Based on satellite-derived eddy tracks, sea ice concentration data and krill trawl fishery data, we analyzed the spatial distribution and characteristic properties of mesoscale eddies as well as the spatial pattern of sea ice. A generalized additive model was established to explore the effects of eddy evolutionary stage, relative distance from fishing locations to the nearest eddy center, sea ice concentration, and fishing longitude and latitude on catch per unit effort (CPUE) of Antarctic krill. The results showed that mesoscale eddies in the Scotia Sea present a zonal aggregation pattern. Cyclonic eddies are slightly more numerous with stronger dynamic intensity, while anticyclonic eddies have larger spatial scales. Sea ice concentration displayed a decreasing gradient from the southeast to the northwest. In the northern study area, krill CPUE increased significantly with rising latitude, while its longitudinal variation was insignificant. Eddy evolutionary stage, relative distance to eddy center, and sea ice concentration exerted significant effects on krill CPUE. Within anticyclonic eddies, CPUE declined markedly with the increase of sea ice concentration, with high-CPUE areas concentrated in low sea ice concentration regions. In cyclonic eddies, krill CPUE showed strong habitat stability, and its distribution centroid shifted toward moderate sea ice concentration and medium relative distance ranges. This study clarifies the joint regulation of mesoscale eddy dynamics and sea ice conditions on the spatial distribution of Antarctic krill, providing scientific support for polar fishing ground identification and fishery resource management.