Millions of deep-sea eels gather near Tasmania seamount

Researchers have quantified a massive annual gathering of basketwork eels (Diastobranchus capensis) near Patience Seamount, located south of Tasmania within the Huon marine park. A study led by Ben Scoulding of the Australian scientific agency CSIRO reveals that at peak times, the congregation can include up to 2.8 million eels, with a combined weight exceeding 3,500 metric tons.

The aggregation covers an area approximately three kilometers long and two kilometers wide, extending up to 150 meters above the seabed. While commercial fishers reported unusual concentrations as early as the 1980s and footage captured the phenomenon in 2007, recent sonar and underwater surveys between 2023 and 2025 have allowed scientists to estimate the true scale of the event.

Scientists believe the eels gather primarily for reproduction, as examined specimens show advanced reproductive conditions. However, the specific reason why they choose Patience Seamount over approximately 120 other similar underwater mountains in the region remains an unanswered question.