What happened: A team led by CSIRO marine scientist Ben Scoulding estimated that up to 2.8 million basketwork eels, weighing about 3,550 tonnes together, gather at Patience Seamount, an extinct volcanic peak in Australia's Huon Marine Park off Tasmania. The estimate comes from nine acoustic surveys between 2023 and 2025, checked against towed camera footage and physical samples, and was published in Royal Society Open Science.

Why it matters: Most females carried advanced-stage eggs and the eels had empty stomachs, which points to a spawning gathering rather than a feeding one. Of roughly 120 seamounts in the area, this is the only one where such gatherings have been recorded, which makes it a rare site worth protecting.

How much agreement is there? Broad agreement. This is a measurement study; the authors note sonar alone can't separate eels from orange roughy that also gather there, which is why they combined methods.

Could someone help? Marine park managers and ocean-science students can use counts like this as a baseline to tell whether the gathering is holding up over time.