A single longspined sea urchin has been found in Tasmania’s remote southwest waters, marking the most westerly sighting of the invasive species in the state.
The 127mm urchin was discovered between Port Davey and Low Rocky Point, well outside its usual range on the east coast.
“This is quite notable because it’s the westernmost urchin ever reported in the state,” Dr John Keane, a senior research fellow at the University of Tasmania’s Institute for Marine and Antarctic Studies, said.
“We typically see dense populations on the east coast and some around Port Arthur. However, sightings are increasing across our southern reefs.”
Warming sea temperatures over the past 50 years have allowed longspined sea urchins to expand hundreds of kilometres south from New South Wales into Tasmanian waters.
Dense populations have transformed parts of the east coast into barren underwater landscapes, stripping reefs of kelp and seaweed.
More than 15% of Tasmania’s east coast is now urchin barrens, with over 150 species affected by the habitat loss.
Dr Keane said while one urchin wasn’t cause for alarm, the sighting highlighted the potential threat.
“While a single individual is not a problem, this sighting highlights the extent of the threat if our waters continue to warm,” he said.
Commercial divers have removed more than eight million urchins from Tasmanian reefs since the state government’s incentivised harvest program began in 2018.
The discovery comes as the commercial harvest season ramps up, with roe quality now at its peak.
Dr Keane encouraged Tasmanians to help eat the problem.
“Prime centro harvest season is from now until June,” he said, referring to the urchin’s nickname derived from its scientific name Centrostephanus rodgersii.
“If you eat centro in the off season it can taste bitter and some people may find it off-putting.”
“For the next four months it’s sweet and it’s when you want to consume this international delicacy.”
Divers who spot longspined sea urchins outside their usual range are encouraged to report sightings to IMAS.
