Sonar and Cameras Reveal Scale of Deep-Sea Eel Gathering

The scale of a gathering already known to scientists. The gathering was already known, and the surveys helped estimate its scale.

Clue: A seasonal aggregation of basketwork eels at Patience Seamount, off Tasmania, could contain up to 2.8 million animals, according to a study led by Australia's CSIRO. Although the gathering was already known, researchers used surveys from 2023 to 2025 to estimate its scale.

Sonar alone could not reliably distinguish the eels from other fish. Sonar alone could not reliably separate eels from other fish, so the team also used images.

Clue: The team combined acoustic measurements with underwater images because sonar alone could not reliably separate the eels from other fish. Evidence from sampled females supports the idea that the animals gather to reproduce, but exactly why they select this seamount remains unresolved.

Samples support the idea that the eels gather to reproduce. Evidence from sampled females supports a reproductive purpose, but the article does not claim every eel was observed reproducing.

Clue: The team combined acoustic measurements with underwater images because sonar alone could not reliably separate the eels from other fish. Evidence from sampled females supports the idea that the animals gather to reproduce, but exactly why they select this seamount remains unresolved.