The UTAS' Institute for Marine and Antarctic Studies' study used multibeam sonar mapping paired with an autonomous underwater vehicle to photograph the seafloor to depths greater than 30 metres to monitor the changes.

IMAS researcher Nick Perkins led a team to analyse seabed imagery collected from along the coast between 2011 and 2016. He said the technology could be used over large coastline sections to contribute to urchin management approaches to help control the expansion of barrens.

"[We covered] areas of rocky reef in the Bicheno region where the invasive long-spined sea urchin Centrostephanus rodgersii has been increasing in density in recent years," he said.

"This allowed us to track the changes to rocky reef ecosystems through time, gave us valuable insights into changes in biological communities across a wide range of depths and allowed us to match barrens occurrence to different levels of reef complexity."

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It analysed the Governor Island Marine Reserve, which has been closed to fishing for almost 30 years, and the study indicated the absence of fishing for extended periods provided resilience to barren formation, although barrens still develop.

Although it found areas inside the reserve may be more resistant to the establishment of barrens, Dr Perkins said there was no difference in the rate of increase of barrens inside and outside the reserve over the survey period.

"In 2016, barrens inside the reserve covered less than one per cent of the rocky reef surveyed, while sites outside the reserve had from three to 10 per cent barrens cover in that year. This may be because southern rock lobster, the urchin's main predator, exist in higher densities and at larger average sizes where fishing is excluded, which results in increased urchin predation," he said.

"The overall barren cover doubled over the five-year survey period regardless of whether areas were protected or not, which raises serious concerns around the likely longer-term trajectory of barren formation, especially as previous IMAS research shows that, once established, recovery of barrens habitat is problematic.

"We found that using multibeam seafloor mapping in the study areas enabled us to map out the spatial variation in reef depth and surface roughness, and to use this to more accurately predict where urchin barrens are more likely to form."

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