Antarctic robot ‘Lassie’ uncovers thousands of icefish nests beneath Antarctic ice

The opportunity for this find came after the massive A68 iceberg, spanning 5,800 square kilometers, broke away from the Larsen C Ice Shelf in 2017. This event opened a new window for exploration. Using a remotely operated vehicle (ROV), scientists observed more than a thousand circular nests on the seafloor. Each nest was swept clean of the plankton debris that blanketed the surrounding sediment, creating a landscape of geometric order across the ocean floor.

The sand depressions visible in images mark these nests: some stand alone at the bottom right, others form curved lines at the center, and still others cluster together at the top left. All appear free from the layer of phytoplankton detritus covering the nearby seabed -- a sharp contrast easily seen in the central portion of the image.

The Expedition

The Weddell Sea Expedition of 2019 had two primary objectives: to carry out a wide-ranging scientific survey in the waters around the Larsen C Ice Shelf and to search for the wreck of Sir Ernest Shackleton's ship, the Endurance, lost in 1915. Scientists were particularly focused on the vital role of Antarctica's floating ice shelves, which act as barriers that slow the flow of glaciers from the continent's interior. When these shelves thin or disintegrate, that stabilizing effect disappears, allowing land ice to move more quickly into the ocean and raise global sea levels.

The calving of iceberg A68 created a rare scientific opportunity. Researchers could now study a part of the seabed that had been completely sealed off until the ice broke away, providing a real-time look at how the region was responding to environmental change.

Aboard the South African polar research vessel SA Agulhas II, the team deployed autonomous underwater vehicles (AUVs) and a remotely operated vehicle (ROV) to navigate the same kind of dense sea ice that had crushed Shackleton's ship over a century earlier. The pack ice again proved formidable, preventing the team from locating the Endurance in 2019. However, their experience maneuvering through these conditions and operating advanced underwater technology paved the way for the later Endurance22 expedition, which successfully found the remarkably preserved wreck in March 2022, resting 3,008 meters below the surface.

A Story of Survival

The nest builders turned out to be a species of Antarctic rockcod known as the yellowfin notie (Lindbergichthys nudifrons). Each circular nest was likely tended by a parent fish guarding its eggs from predators. Researchers believe this behavior reflects a collective survival strategy. The dense groupings illustrate the "selfish herd" concept, in which individuals in the center are protected by those on the edges. The solitary nests along the perimeter are thought to belong to larger, stronger fish capable of defending their territory alone. The result is a balanced mix of cooperation and competition that enhances the entire colony's chances of survival.

Why It Matters

This discovery holds far more than academic interest. It offers strong evidence that the region represents a Vulnerable Marine Ecosystem, a fragile yet vital habitat that supports Antarctic biodiversity. The finding adds to earlier studies, including Purser et al. (2022), which identified one of the world's largest fish breeding colonies in the Weddell Sea.

Together, these findings strengthen the case for designating the Weddell Sea as a Marine Protected Area. Safeguarding this region would help preserve not only its iconic wildlife, such as penguins and seals, but also the hidden nurseries that sustain the Antarctic food web. The discovery serves as a powerful reminder that even in the planet's most extreme environments, life finds ways to organize, adapt, and thrive.