A giant ball of 2,800,000 eels is having an orgy off the coast of Australia

| Senior science and technology reporter Published October 28, 2026 12:36pm Updated October 28, 2026 12:39pm To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video For almost 10 months straight every year, millions of eels gather at a deep-sea mountain near Australia to have an orgy. The 2.8 million basketwork eels, which weigh nearly 3.5million kilograms, cram into Patience Seamount just south of Tasmania just to mate. A study led by Australia’s scientific research agency CSIRO, published today in Royal Society Open Science, counted them for the first time. The eels, known to scientists as Diastobranchus capensis, are slimy scavengers that look like purple-ish woven noodles. They’re usually found across the southern coasts of Australia and Africa but have been slithering to a specific ridge at Patience Seamount since the 1980s, peaking from March to May before dispersing in October. Study lead author Ben Scoulding told the Australian Broadcasting Corporation his team carried out surveys between 2023 and 2025 to count how many eels make the blob. Basketwork eels swimming above the seabed at Patience Seamount (Picture: CSIRO) They annually swarm a patch of seamount within the Huon Marine Park (Picture: CSIRO) They used a ‘really expensive scientific fish finder’, as Scoulding put it, called a hydro-acoustic survey, to ping sound waves down below. The sound would bounce off anything it knocks into, allowing the researchers to see all the wriggling eels. Dr Scoulding said the ball was about 1,000 metres deep and covered an area about two by three kilometres wide. ‘One of the interesting things is the persistence of the aggregation,’ he said, adding: ‘It is there for the majority of the year.’ CSIRO caught a few eels and found they all had empty stomachs, with most of the females close to laying eggs, called spawning. This suggests they may stop eating as they prepare to join the writhing eel ball. Some of the eels hadn’t recently eaten (Picture: CSIRO) A sonar cross-section of the ridge shows just how many eels were crammed into one area (Picture: CSIRO) The study’s count is far higher than an estimation made in 2015, which was 10s of thousands of eels in April that year. Previous catches have similarly found both males and females in peak spawning condition, suggesting they came for a reproductive reason. Dr Scoulding says his team’s findings don’t reveal why the eels have chosen Patience Seamount for their, uh, orgy. Populations of the eel on the slopes in New Zealand have declined 85% in the past 40 years, though it’s unclear if drops at Patience Seamount have happened before. And they have good reason to throw these oceanic sex parties – basketwork eels are vulnerable of becoming endangered, according to the International Union for Conservation of Nature’s Red List. Fisheries are accidentally catching the eels, causing the eel population to slowly but ‘significantly’ decrease, the global scientific authority says. Get in touch with our news team by emailing us at webnews@metro.co.uk. For more stories like this, check our news page. Arrow MORE: Aussie prison inmate loses bid to be allowed Vegemite in jail Arrow MORE: TV star Damien Richardson avoids jail over Nazi salute but must visit Holocaust museum Arrow MORE: Solar storm fears as ‘modest’ flare soaks plane with 1.5 times more radiation than normal News Updates Stay on top of the headlines with daily email updates.