Invasive Sea Urchin Population Growth

IMAS surveys of invasive Long-spined Sea Urchins on reefs along Tasmania’s East Coast have measured the size of increases in the urchin population and the barren areas they create by overgrazing kelp beds.

Led by Principal Investigator Dr Scott Ling, researchers conducted SCUBA and towed-underwater-video surveys spanning 156 sites across 13 East Coast locations between Eddystone Point and Recherche Bay, repeating a baseline survey carried out in 2001/02.

A report on the latest survey released today found that since 1978, when a single Long spined Sea Urchin was found in St. Helens, the Tasmanian population has grown to an estimated 20 million.

For eastern Tasmania, over the last 15-years the urchin population has grown from an estimated 11 million to more than 18 million, with an average increase in urchins of 170 tonnes per annum.

Along the open coastline from Eddystone Point to Tasman Island, urchin barrens now cover an estimated 15 per cent of reefs at depths of 4-40 metres, up from 3 per cent in 2001/02.