New research highlights the important role that sea ice plays in the migration of young Antarctic krill, potentially linking distant parts of the Southern Ocean in ways that were not previously recognized. Published in Global Change Biology Communications, the study models how ocean currents, sea ice movement, and the vertical and horizontal migration of krill influence their movement across the southwest Atlantic sector of the Southern Ocean during winter. Lead author Aditya Sharma, a Ph.D. student with the Australian Antarctic Program Partnership at the University of Tasmania, explains that krill do not simply drift with ocean currents. Instead, they use sea ice as a transport system, moving vertically between the ocean and ice and horizontally while in the open water. This behavior changes the paths they take, allowing them to travel farther and reach new areas. Krill recruitment — the survival of young krill to their first birthday — is the main factor that determines how many krill there are in a given year and how their population changes over time. Krill larvae depend on sea ice for food and shelter during winter, which is crucial for their survival. Understanding where krill go during this time could be as important as knowing where they are found in summer. The study shows that the same starting group of krill can take very different paths from one year to the next, illustrating the unpredictable nature of the Southern Ocean. Using 32 years of high-resolution data on ocean currents and sea ice movement, the researchers modeled how krill are transported across the Southern Ocean. They simulated the movement of "virtual krill" released in the southwest Atlantic sector from April to October, a critical time for the survival of young krill. The model tested extreme scenarios where krill either spent all their time in sea ice or in open water, helping the team understand the maximum impact of their behavior on movement patterns. The model found that krill tend to move eastward away from the Antarctic Peninsula, largely due to the Antarctic Circumpolar Current. When relying only on ocean currents, only 4% of simulated krill moved west, while 17% moved east. However, when krill spent all their time near sea ice, 21% moved west and 48% moved east, showing a significant shift in transport patterns. This suggests that sea ice plays a crucial role in shaping krill migration. Antarctic krill are a keystone species in the Southern Ocean, playing a vital role in the marine ecosystem, nutrient cycling, and carbon storage. They are also the target of the world's largest fishery in the Southern Ocean, which is carefully managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The fishery is currently limited to the southwest Atlantic sector of the Southern Ocean, divided into six management zones. The tip of the Antarctic Peninsula is a major recruitment hotspot, and the study shows that krill from this area can be transported to all other management zones and even into the neighboring Bellingshausen Sea. However, the flow of krill is not balanced — the peninsula is more of a source than a destination, exporting krill widely while receiving fewer inputs. This has important implications for fisheries management, as changes in krill movement due to shifting sea ice conditions could affect krill availability in different regions. Understanding these connections can help improve stock assessments and support sustainable fishing practices. As Antarctic sea ice continues to decline, the pathways that transport young krill across the Southern Ocean may change, potentially altering how krill populations are connected to different fishing areas. This research provides a better understanding of how krill move across the ocean, which is essential for managing the fishery in a way that supports both the ecosystem and human use.