Institute for Marine and Antarctic Studies researchers have completed the first assessment of the state's long-spined sea urchin fishery, finding that between 2001 and 2016, about 153 tonnes of sea urchin biomass was added to Tasmania's waters per year.

Harvesting increased rapidly as a result of a subsidy introduced in 2016/17, with 185 tonnes removed in 2017/17 and 560 tonnes in 2018/19.

The species is believed to have become established in Bass Strait in the 1960s and was first reported off Tasmania's north-east coast in 1978 having extended south from NSW due to the warm East Australia Current caused by climate change. Sea urchin have since expanded down the East Coast.

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They are known to damage kelp forests through overgrazing, creating flow-on effects for native species, as well as commercial and recreational activities. Once established on a reef, sea urchin create barren patches of rock and can exist in a "starvation state" for decades.

The assessment's lead author, Katie Cresswell, said there was evidence that catch rates were falling in the heavily-harvested areas off the coast of St Helens.

"While harvesting for the entire coast is sustainable despite the increases in total catch, there is evidence of stock reduction in the most heavily fished areas over time," Dr Cresswell said.

"This suggests that, for the more heavily fished areas, catch rates will fall, which will create an incentive for divers to move southward down the coast.

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"The effect of divers shifting to new areas means that we won't necessarily see sharp declines in catch rates if high levels of harvest continue to occur."

In addition to harvesting, the rebuilding of rock lobster stocks - the key predator of sea urchin - could also help to reduce their numbers, along with the potential use of sea urchin waste in agricultural industries. Culling has also been considered and while it can remove sea urchin faster than harvesting, it is labour-intensive and costly.

Co-author Caleb Gardner said all interventions were based on the best available research.

"Commercial harvesting is one of a number of actions taken to reduce the number of these invasive urchins, with most interventions based on IMAS research and supported by the state government and the Tasmanian Abalone Council under the Abalone Industry Reinvestment Fund," Professor Gardner said.