“Our main theory is they come together when they’re moulting as a ‘safety in numbers’ approach because that’s when they’re most vulnerable to predators,” Camprasse said.

Source: https://www.theage.com.au/national/victoria/diving-for-an-explanation-to-the-mysterious-migration-of-giant-crustaceans-20230615-p5dgrm.html?ref=rss&utm_medium=rss&utm_source=rss_national

There is little scientific data collected around spider crabs, Deakin research fellow in spider crab ecology Dr Elodie Camprasse told 9news.

Source: https://www.9news.com.au/national/spider-crab-news-native-spider-crabs-gather-melbournes-port-phillip-bay-every-winter/9e4b1c72-6032-417d-83ad-62d2e1ed2c65