Deep-sea eel aggregation near Tasmania

Researchers from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) have quantified a massive annual gathering of basketwork eels, Diastobranchus capensis, near Patience Seamount in Australia’s Huon Marine Park.

Studies conducted between 2023 and 2025 using sonar and underwater surveys estimate that the congregation can reach up to 2.8 million individuals, with a combined weight exceeding 3,500 metric tons. The biological mass covers an area approximately three kilometers long and two kilometers wide, extending up to 150 meters above the seabed. Ben Scoulding, a CSIRO researcher, noted that in high-density areas, the seafloor appears as a “carpet of eels” positioned only centimeters apart.

While commercial fishers reported unusual concentrations as early as the 1980s, scientists believe the eels gather primarily for reproduction, as examined specimens show advanced reproductive conditions. The specific reason why the eels choose Patience Seamount over approximately 120 other similar underwater mountains in the region remains an unanswered question.