Weedy seadragon

How it lives

It lives in kelp and seagrass beds beside shallow rocky reefs, mostly at about 2 to 30 m, and is seen alone or in pairs. It is a weak swimmer. The male carries the eggs fixed to the underside of his tail. One source reports about 120 eggs laid on the male, and another reports up to 250 young from a single brood. Incubation is roughly 4 to 8 weeks depending on the source. Fish become mature at about 2 years, and tagged adults in a Sydney study lived for more than 8 years.

Where it goes

Weedy seadragons do not migrate. Adults stay close to home: most tagged adults moved under 200 m over their lifetime in one Sydney study, and another study gives 50 to 500 m. Genetic work found separate groups in central New South Wales, southern New South Wales, Victoria and Tasmania, which points to little mixing between regions.

We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.

Populations

The IUCN (assessed 2024, published 2025) rates it Vulnerable under criteria A2bc, meaning a suspected population decline. Earlier it was rated Least Concern (2016). Its range runs along southern Australia from about Port Stephens in New South Wales to Geraldton in Western Australia, including Tasmania. No total population count was found. A 2023 analysis of citizen-science survey data reported a 59% decline between 2011 and 2021, but a 2024 preprint by Schlögl and Booth concluded that the data are too sparse to support that figure. Habitat loss, pollution and warming seas are named as the main concerns. The species is protected in New South Wales and Tasmania.