About 2.8 million eels gather to spawn beside a seamount off Tasmania

About 2.8 million basketwork eels meet each year on a ridge beside Patience Seamount, off Tasmania, and a new study argues they are there to spawn. ABC News reported on October 28, 2026, on a CSIRO-led paper in Royal Society Open Science.

The aggregation is inside Huon Marine Park. Lead author Ben Scoulding said it is the only known gathering of any deep-sea eel. Basketwork eels, Diastobranchus capensis, grow to about 1.8 metres and carry a crosshatch pattern that gives them the name. Surveys from 2023 to 2025, using cameras and the ship's acoustic gear, put the mass at about 3,500 tonnes. The sound bounces off the swim bladder. The densest fish are almost touching along a ridge northwest of the peak, about 1,000 metres down, across an area of roughly 2 by 3 kilometres. Farther out, the spacing thins to something like one eel in a living room.

They start arriving in December, peak from May to August, and leave by October. Caught fish had empty stomachs. One female had already spawned and the others were close. Huon Marine Park holds about 120 seamounts, and the eels use this one. Why is still open, as is whether eels from around Australia and New Zealand all come here. The species is listed as vulnerable, in part because it is caught with orange roughy. The paper estimates a spawning crowd. It does not yet trace the larvae.