Science & Tech · Science & Environment · 3 hrs ago
Researchers estimate 2.8 million eels gather off Tasmania to spawn
A CSIRO-led study estimates 2.8 million basketwork eels gather near Patience Seamount off Tasmania.
The site is in the Huon Marine Park, and the eels gather there each year to spawn.
Researchers used sound surveys and underwater cameras between 2023 and 2025 to estimate their numbers and map the aggregation.
The eels gather from December, their numbers peak from May to August, and they are gone by October.
The gathering is the only known deep-sea eel aggregation of its kind, though researchers do not know why the eels choose this particular seamount.
Basketwork eels are considered vulnerable to extinction, in part because they are caught as bycatch.
Researchers are studying whether eel populations around Australia and New Zealand also gather at Patience Seamount.
Researchers estimate that as many as 2.8 million basketwork eels gather to spawn near Patience Seamount off Tasmania.
A CSIRO-led study used acoustic and camera surveys to estimate the scale of the aggregation.
The eels gather at a site in the Huon Marine Park, about 1,000 metres deep and covering roughly 2 by 3 kilometres.
Researchers found that captured eels had empty stomachs and were close to spawning, supporting the view that the gathering is reproductive.
The reported peak timing differs between the articles: ABC says numbers peak from May to August, while ScienceAlert says they peak from March to May.
- Who
- Basketwork eels (Diastobranchus capensis).
- What
- Researchers estimate that up to 2.8 million gather in an annual aggregation. The gathering is believed to be for reproduction.
- When
- The eels begin gathering in December and disappear in October, according to ABC. The articles give different peak periods: March to May and May to August.
- Where
- Near Patience Seamount in the Huon Marine Park, off Tasmania.
- Why
- Researchers believe the eels gather to spawn. Why they choose Patience Seamount is not known.
This story does not have two clearly opposing sides.
Commercial fishers reported unusual numbers of basketwork eels around Patience Seamount.
A CSIRO camera survey captured the eel aggregation, according to ScienceAlert.
Recent surveys helped researchers estimate the number of eels in the aggregation, according to ABC.
A CSIRO-led study estimating the aggregation’s scale was published in Royal Society Open Science.
- Estimated peak number
- Up to 2.8 million eels
- Estimated total weight
- About 3.5 tonnes
- Species
- Basketwork eel (Diastobranchus capensis)
- Location
- Patience Seamount, Huon Marine Park
- Estimated depth
- About 1,000 metres
2 sources
What people are saying
It's the only known aggregation of … any deep-sea eel anywhere.
That's one of the biggest unanswered questions
At this stage, we have some good hypotheses, but we don't yet have a definitive answer.
Seeing so much biomass concentrated on such a small deep-sea feature is rare, and the scale, persistence, and likely reproductive nature of the aggregation make it one of the most remarkable fish aggregations documented in the deep ocean.