A new study published in Nature Sustainability highlights Tasmania’s innovative and globally relevant approach to managing an invasive marine species—by intentionally overfishing it. The Longspined Sea Urchin (Centrostephanus rodgersii), which has damaged over 15% of Tasmania’s kelp forests, is being controlled through a government-subsidised commercial fishery that removes about 1.2 million urchins annually. Researchers from IMAS and CSIRO found that this strategy has halved the urchin population compared to what it would be without intervention. Using modelling, the team identified where subsidies should support targeted overfishing and where sustainable harvests can continue without financial aid. The goal is “functional eradication”— keeping urchin numbers low enough to prevent ecosystem collapse, rather than total removal. The study challenges traditional views on conservation by showing that fishing a pest species can be both ecologically and economically sustainable. The findings have global implications for managing invasive and range-extending species worsened by climate change.

Fast facts:

• The larvae of Longspined Sea Urchin (Centrostephanus rodgersii) drifted south from NSW on a strengthening East Australian Current and settled in Tasmania’s warming waters. Adults were first recorded in St Helens in 1978.
• These voracious feeders have transformed over 15% of Tasmania’s healthy kelp beds into barren rock, called urchin barrens.
• Over 150 species are lost or displaced where barrens form, significantly reducing the productivity of reef-based fisheries like abalone and rock lobster.
• Longspined Sea Urchins spawn in late winter, with larvae only developing in waters above 12°C—Tasmania’s coastal waters now exceed this due to climate change.
• IMAS and CSIRO have partnered with government, industry, and communities to assess and guide control efforts, expand roe processing, and explore fertiliser production from waste.
• The commercial fishery removes around 470 tonnes (1.2 million urchins) annually and has been rated ‘sustainable’ since 2019.
• Urchin roe is a global delicacy; most of Tasmania’s catch is exported internationally.
• Urchins are hand-harvested by divers down to 26m depth. Kelp regrowth has been observed where urchin populations are reduced.
• Harvest incentives are supported by the Abalone Industry Reinvestment Fund, running through 2026.
• A 2023 Federal Senate Inquiry recommended a national investment in urchin control; the proposal is still under consideration.

Full Institute for Marine and Antarctic Studies (University of Tasmania) article available here: https://www.utas.edu.au/about/news-and-stories/articles/2025/eat-the-problem-when-overfishing-is-a-sustainable-option