Researchers Found Hundreds of Mysterious Dimples on the Seafloor Near Antarctica. Now They Know What Creature Made Them The indentations are nests of fish called yellowfin notie, and they are not randomly scattered—rather, they appear to have been arranged in distinct patterns Sarah Kuta - Daily Correspondent November 6, 2025 8:56 a.m. While seaching for Ernest Shackleton's lost ship Endurance in 2019, researchers stumbled across clusters of indentations on the seafloor. Weddell Sea Expedition 2019 Scientists were using an underwater robot to explore the waters around Antarctica when they came across a peculiar scene: The seafloor was dotted with hundreds of mysterious dimple-like indentations. At first, the researchers were totally perplexed. Working aboard the polar research vessel S.A. Agulhas II, they went back and forth, debating what the imprints might be—and what might have made them, reports BBC Wildlife Magazine’s Melissa Hobson. Now, the scientists say they have an answer. The depressions were nests created by yellowfin notie (Lindbergichthys nudifrons), a type of fish that thrives in the extreme cold of Antarctic waters. Researchers describe their discovery in a new paper published October 28 in the journal Frontiers in Marine Science. Fun fact: A big berg When the giant iceberg A68 broke free from the Larsen C ice shelf in 2017, it made news, even becoming a social media star. It's no wonder: The iceberg was twice as large as the entire country of Luxembourg and was even visible from space, before breaking up into smaller pieces. The discovery “goes to show that exploration of our world is still underway, with constant new findings,” lead author Russ Connelly, a marine biologist at the University of Essex in England, tells CNN’s Ashley Strickland. Researchers discovered the yellowfin notie nests during the 2019 Weddell Sea Expedition. The mission, which took place in January and February 2019, included scientists from around the world. It had several goals. A big one was to find Ernest Shackleton’s lost ship Endurance, which became trapped in sea ice and sank in 1915. But the team also wanted to investigate ice shelves in the Weddell Sea, particularly a largely unexplored region of the Larsen C ice shelf on the Antarctic Peninsula. In July 2017, a massive, 2,200-square-mile iceberg called A68 broke free from the ice shelf, revealing a huge swath of newly accessible seafloor below. “That calving event provided a unique opportunity to study a region undergoing rapid environmental change, specifically the first chance to study previously inaccessible areas of the seabed that were once underneath A68,” Connelly writes in a commentary accompanying the paper.The researchers didn’t find the Endurance—though another group located it three years later in 2022—but they did learn plenty about the Weddell Sea, one of the most remote and least studied regions on the planet, Connelly writes. The yellowfin notie nests, for example, were a major find. In total, the team documented 1,036 nests across five sites. The researchers found larvae in and around 72 of them. Video footage also revealed new insights about the creatures, including how they arrange their nests to ensure the survival of their young. The nests, which had all been cleared of plankton, were not randomly scattered. Instead, they were “organized into distinct patterns, forming a vast, geometric fish neighborhood on the seafloor,” Connelly writes. Over 1,000 Strange Markings Discovered On Antarctic Seafloor Many of the nests were arranged in clusters, and the scientists suspect this setup helps keep the eggs safe from hungry predators, like brittle stars and ribbon worms. Once the eggs are laid, males stand guard for roughly four months to ensure the little ones don’t get eaten. Since yellowfin notie males are known to defend the area surrounding their nest—up to about 9.8 inches away—the clusters likely make everyone safer. Some of the nests were more isolated, perched on the outskirts of the communities. Researchers think those are inhabited by larger, stronger fish that are better suited to defend themselves and their eggs on their own. The arrangement is an example of the “selfish herd” theory, which posits that animals “reduce their domain of danger by putting other individuals between themselves and an approaching predator,” the researchers write in the paper. Similar defensive nesting patterns have been observed in other species of fish, though this is the first time scientists have documented it in yellowfin notie. “The entire community is a dynamic interplay between cooperation and self-preservation,” Connelly writes. Nearly 15 percent of the active nests had pebbles in and around them, and some had been built next to rocks. The researchers suspect the fish might be taking advantage of stones that fall off icebergs as they melt. These rocks “are ideal to lay eggs on as they allow good oxygenation of the eggs, helping to prevent rotting on the seafloor, whilst also providing a barrier to animals living within the muds to eating the eggs,” Autun Purser, an ecologist at the Alfred Wegener Institute who was not involved with the research but reviewed the paper for the journal, tells CNN. Zooming out, the scientists hope their findings will help support efforts to get the Weddell Sea designated as a marine protected area. The move would not only help protect charismatic creatures like penguins and seals, but also “these hidden nurseries that form part of the Antarctic food web,” Connelly writes. “These underwater environments are a powerful reminder that even in the planet’s most extremes, life finds a way to build complex, resilient communities,” he adds. Get the latest stories in your inbox every weekday.

The indentations are nests of fish called yellowfin notie, and they are not randomly scattered—rather, they appear to have been arranged in distinct patterns