Sea Dragon Death Toll Mounts During South Australia's Algal Bloom

A recent report has documented nearly 1,700 sea dragon mortalities during South Australia's harmful algal bloom (HAB), with hopes of a strong breeding season next month. The report, led by local marine ecologist Janine Baker, analyzed 1,540 reports uploaded by 253 people to a citizen science platform about sea dragons, pipefish, and seahorses from January 1, 2025, to May 31, 2026.

Habitat and Mortality

About 1,524 weedy sea dragons were recorded dead in South Australia, while 159 leafy sea dragons were also reported dead. "The weedy and the leafy in particular occur in South Australia as a world hotspot," said sea dragon researcher David Booth from the University of Technology Sydney. "People have come from all over the world to places like Rapid Bay to see these amazing animals."

The HAB first emerged in South Australian waters in early 2025, affecting areas such as Encounter Bay, St Vincent and Spencer gulfs, Investigator Strait, and waters off Kangaroo Island. Sea dragons, part of the Syngnathidae family, have small gill pores that can be easily clogged by microalgae, making them vulnerable to the bloom.

Species Affected

Deaths caused by HAB spanned 13 species in the family, including pipefish and seahorses. At least 787 seagrass-dwelling brushtail pipefish mortalities were recorded, along with 574 spotted pipefish and 42 long-snout pipefish. More than 160 short-head seahorse were recorded, while the south-eastern Australian big-belly seahorse washed up in small numbers.

Breeding Season and Conservation Efforts

Professor Booth said sea dragons were entering their October breeding season in SA, and researchers were looking at ways to boost sea dragon numbers, including bringing pregnant males into the laboratory to hatch the eggs and rear their fry before releasing them. "They have a much higher survival rate that way and can boost the population," he said. "But that's only of use if we can fix the habitat. There's been so much habitat destruction — huge losses of sponges, kelp, seagrasses — all those sorts of things that these animals need, and their food in little shrimps."

"We really need to be working on that and we are. There's habitat restoration going on but it is a big job," Professor Booth added. This includes shellfish reef restoration projects across multiple locations, and research to restore approximately 6,000 hectares of seagrass meadows — natural filters of microalgae — that have been lost from Adelaide's coastline since the 1950s.

Full Impact Unknown

The report stated that the HAB's impact on the full population of Syngnathidae remained unknown because there had not been an official systematic survey undertaken in the past or present. Janine Baker said previous data came from divers, snorkellers, beachgoers, independent research surveys, museums, fishers, and trawler bycatch, with much of it dating from the 1980s to 2000s.

"There is no doubt that leafy sea dragon numbers are lower than pre-bloom in those inshore habitats, but offshore numbers away from dived locations remain undocumented," Janine Baker said.