IMAS research reveals invasive sea urchin managed through overfishing commercially

One of Tasmania’s largest wild fisheries species is being overfished, but scientists say it’s a good thing. Why they say this practice could save species across the globe.

Long-spined sea urchin. Picture: Peter Mathew

New IMAS research has determined that overfishing – and eating – of one particular pest is helping to protect delicate marine ecosystems in Tasmania.

In a new paper published on Friday in Nature Sustainability, a team of scientists from the University of Tasmania’s Institute of Marine and Antarctic Science (IMAS) have revealed that the establishment of a commercial fishery for “edible pests” like the long-spined Sea Urchin to overfish the species intentionally can save and protect vital marine ecosystems.

The larvae of long-spined Sea Urchin drift on a current south from New South Wales to waters in Tasmania.

Due to warming climates and warmer waters, the species has taken hold, with the urchin first recorded on mainland Tasmanian reefs in St Helens in 1978.

Katie Cresswell senior research fellow at IMAS with a long spine sea urchin. Katie has conducted research into the impact of commercial fishing of the long spine sea urchin population. Picture: Nikki Davis-Jones

Once settled in a reef, the urchins can affect more than 150 species in the area, including destroying 15 per cent of kelp beds into marine deserts called urchin barrens.

The reef-based fisheries like abalone and rock lobster are also heavily impacted by the spread of the long-spined Sea Urchin.

The joint research between IMAS and the CSIRO investigates long-spined sea urchin management in Tasmania and how to slow the spread and reduce the numbers of urchin.

Senior research fellow and lead author Dr Katherine Cresswell said the research first found that commercial fisheries dramatically cut back on sea urchin populations.

“We see from our work that the urchin’s population would be double what it currently is without the fisheries,” she said.

“Considering they started in 2009 and are mainly operating where other fisheries already exist for abalone or oysters, they have done a fantastic job.”

Urchin barren in Tasmania. Picture: John Keane.

In 2018, funding was delivered by representatives from the Tasmanian Government, abalone industry and researchers to direct $5m of funds for preventing further urchin barrens and impacting fishery industries.

With further targeting in 2019, total annual catches for long-spined sea urchins rose to have an average of 500t, or 1.3 million urchins, over the past 5 years, making it one of the state’s largest wild fisheries by tonnage.

Dr Cresswell said their research established a new computer program that can model where commercial fisheries are well-placed in Tasmania, to ensure industry funding and sustainability.

“We investigated different management scenarios to guide decision-making, including which regions would make more sense to ‘overfish’ using the limited funding for subsidies, and which to allow to operate as a stand-alone sustainable fishery, operated by existing fisheries,” she said.

Commercial diver harvesting Centro. Picture: Matt Testoni

“Areas on the east coast like Fourmile, Bicheno and Forestier were determined to be ‘low-risk’ for urchin barrens and mass increases in urchin populations, meaning they don’t need targeted overfishing to manage the populations.

“‘High-risk’ areas such as St Helens, Schouten and Maria Island would benefit from the targeted commercial fisheries in those areas to manage populations.”

As the model can help decide where it is best to target resources for invasive species, Dr Cresswell said it can have worldwide implications for pest management, including controlling species like the invasive lion fish and where is best to commercially overfish.

Originally published as IMAS research reveals invasive sea urchin managed through overfishing commercially