Wild weather linked to weedy seadragon deaths

“Our investigation revealed the unprecedented deaths of seadragons were likely caused by a series of intense east coast low storms along with a marine heatwave. The extreme weather triggered record-breaking 14m high waves and eight times the normal rainfall.

“These storms caused significant ocean surges and underwater pressure changes, which seadragons struggle to handle. A significant portion of the local seadragon population was lost, and despite some recovery, populations around Sydney are still down.”

The study, Mass stranding of common (weedy) seadragons (Phyllopteryxtaeniolatus) in Sydney: impacts and implications was recently published in the Journal of Fish Biology.

There are three varieties of seadragon found in southern Australia – Weedy, Leafy and Ruby seadragons. They live in kelp forests or seagrass beds on or near shallow, rocky reefs, which also support many other marine species.

Small shrimp-like crustaceans called mysids are a major food source for seadragons. Mysids disappeared from Sydney coastal waters for many months in early 2022, and so a lack of food also likely contributed to seadragon deaths.

“As climate change drives more intense marine heatwaves and storms, along with stronger winds and heavier rainfall, this could pose a serious threat to the survival of seadragon populations,” said Professor Booth.

If someone finds a washed-up seadragon, UTS researcher and coauthor Giglia Beretta advises photographing the animal (including an item for scale in the image), recording where and when it was found, and emailing the details to assist with research.

Images can also be uploaded to iNaturalist Australasian Fishes. The collection of weedy seadragon carcasses is only allowed under strict permits – touching the protected species could result in a fine. 

Dead animals can be collected with the permission of Professor Booth under his UTS Fish Ecology Lab DPI permit. The animals can provide important information for ongoing population studies.