From Overabundance to Opportunity: Reforming Urchin Fisheries for Kelp Recovery in Port Phillip Bay

Pearl Mitchell, Global Voices National Fellow, COP30

Executive Summary

Climate-driven overabundance of Heliocidaris erythrogramma (Helio) is accelerating kelp forest decline in Port Phillip Bay (PPB) through overgrazing. This has created urchin barrens that strip reefs of biodiversity, fisheries habitat, and ecosystem function. Densities exceeding 60 urchins/m², well above the ecological threshold of 4/m², have contributed to 60% of kelp loss in four decades. Without intervention, barren zones will continue to expand, undermining the ecological and economic value of PPB and the broader Great Southern Reef (GSR), which contributes $11.6 billion annually to Australia’s economy.

This paper recommends an integrated reform of Victoria’s sea urchin management framework to increase commercial harvest as a kelp restoration tool. It proposes amendments to the Fisheries Regulations 2019 and Fisheries Act 1995 to establish a barren-zone licence category and enable translocation of urchins from barrens into aquaculture systems for roe enhancement. Implementation would be led by the Victorian Fisheries Authority (VFA) in partnership with industry and research institutions. Estimated costs are $1.2–1.6 million in the first year and $0.7–1.2 million annually, co-funded by government and industry. Success would be measured by reducing Helio densities below 4/m² across 70% of mapped barren reefs within ten years. 

Problem Identification

Within the GSR, PPB faces one of the most severe kelp declines, driven by the overabundance of Helio. Kelp, the primary food source for urchins, is being overgrazed, clearing patches of reef and leaving them in barren conditions. Although native, Helio populations have grown beyond sustainable levels due to warming seas, reduced lobster predation, and shifting nutrient dynamics (Carnell & Keough 2019). In some sites, densities exceed 60/m², more than ten times the ecological threshold of 4/m² required to maintain healthy reef function (Ling et al. 2019). Over the past four decades, kelp cover in PPB has declined between 59-98% (Carnell & Keough, 2019), with an average of 60% across all rocky reefs. 

The transformation of kelp forests into rocky barrens has severe ecological, economic, and social consequences. Kelp forests support high-value coastal fisheries, draw down carbon from the atmosphere, reduce nutrient pollution, buffer wave stress, and provide cultural significance to coastal communities (Bennett et al., 2016, Eger et al., 2023, Filbee-Dexter & Wernberg, 2020). Their loss has cascading effects on associated species, reducing the resilience of marine ecosystems to future climate pressures (Filbee-Dexter & Wernberg, 2018). If left unaddressed, barren areas will continue to expand, undermining long-term ecological and social returns (Smale et al., 2013; Bennett et al., 2016).

Context

The GSR spans Australia’s southern coastline and is among the nation’s most biodiverse and valuable marine ecosystems (Kirkman 1984; Bennett et al. 2015). Its kelp forests support species such as Southern Rock Lobster and Giant Cuttlefish, provide ecosystem services worth over $11 billion annually, and underpin 38 commercial fisheries valued at about $150 million each year (Eger et al. 2022; Johnson et al. 2005). The GSR also holds cultural significance for more than 46 Indigenous nations and supports coastal communities, with 70% of Australians living within 50 km of the coast (Thurstan et al. 2018; Bennett et al. 2016).

Climate change is intensifying stress on these ecosystems. Southeast Australian waters are warming two to four times faster than the global average (BoM 2024; CSIRO 2023), driving marine heatwaves, kelp loss, and population booms of two urchin species: Centrostephanus rodgersii (Centro) and Helio. Centro has expanded south to Tasmania, while Helio has proliferated across Victoria. 

The issue is not only that sea urchin populations are increasing, but that these surges are transforming kelp forests into persistent barren states through continuous grazing. Helio can create barrens at densities of around 8/m² and maintain them at 4/m² (Kriegisch et al., 2016), a level where kelp cannot regenerate naturally, leading to ecosystem collapse (Ling et al., 2009). These conditions are reinforced by ecological feedbacks, known as hysteresis, that sustain degradation even after pressures subside. Urchins persist in food-poor environments by lowering their metabolic rates, allowing populations to survive for decades (Spindel et al., 2021). Helio is particularly resilient, maintaining metabolic function under warming and acidified conditions (Harianto et al., 2020). This adaptability makes recovery difficult without targeted removal. However, research in PPB shows that even partial reductions in urchin density can trigger early kelp recruitment and improve reef condition, especially in semi-degraded areas where remnant kelp persists (Graham, 2023). Current Policy Interventions Australia’s current response to urchin overabundance focuses on culling and commercial harvest. Culling involves the manual removal or destruction of urchins by SCUBA divers (Miller et al., 2022) and is mainly funded through government and community restoration programs. For example, Parks Victoria has removed over 25,000 black sea urchins from the Beware Reef Marine Sanctuary since 2019 under the Victorian Government’s Biodiversity Response Planning program. Although effective in restoring kelp cover in targeted areas, culling is costly, publicly funded, and limited to shallow reefs (Tracey et al. 2011; Miller & Shears 2023). It is best used as a short-term, complementary measure within broader management strategies.

Commercial fisheries provide an economic mechanism for urchin control but face constraints. Established in Victoria, Tasmania, and New South Wales in the 1980s and 1990s, these fisheries harvest urchins for their gonads (roe), which are sold into high-value export markets, mainly in Asia. While this model generates revenue and supports large-scale removals, poor roe quality from barren reefs limits profitability and reduces incentives for operators to target ecologically degraded areas.

Tasmanian Case Study: Centro

Tasmania provides the clearest example of scaling up commercial harvest for sea urchin control. Since 2018, a $5.1 million co-investment between the state government and the abalone industry has subsidised Centro removals, extended to 2026. The program enables extraction of up to 500 tonnes annually and has reduced biomass by about 50% in priority zones (Cresswell et al. 2025). Tiered subsidies and spatial management have directed industry effort toward ecologically significant but less profitable reefs, aligning economic incentives with ecological outcomes.

The initiative was strengthened by the formation of the National Centrostephanus Taskforce in 2023 and a Senate Inquiry that identified Centro as the greatest threat to southeastern kelp forests, recommending $55 million in Commonwealth funding. Although federal support is pending, Tasmania’s experience shows that co-funding and spatially targeted policy can enable commercial fisheries to deliver large-scale removals. Remaining challenges include market instability for Centro and the poor roe quality from barren urchins.

Roe Enhancement Case Study

Roe enhancement offers a potential solution to the low market value of urchins from barren reefs, where roe condition is generally poorer than in kelp forests due to reduced food availability (FAO 2022). The technique involves transferring low-value urchins into aquaculture systems, where they are fed high-quality diets for six to twelve weeks to improve gonad size and quality (FAO 2022). Developed in Japan, this approach is now being trialled in Australia. Deakin University’s AquaFI Lab has undertaken experimental conditioning, while Urchinomics and IMAS have attracted investor interest in similar models (AgriFutures 2021; Urchinomics 2017). Although there are currently no commercial sea urchin aquaculture ventures in Australia, research identifies Helio from Port Phillip Bay as a promising candidate for roe enhancement, provided regulatory barriers are addressed (AgriFutures 2021).

Victorian Context

Victoria’s sea urchin fishery remains underdeveloped despite strong potential to expand. PPB contains extensive barren reef areas and high densities of Helio, particularly in the southern and central zones (Graham, 2023). With Helio’s higher marketability than Centro and suitability for roe enhancement, Victoria is well placed to link ecological restoration with commercial opportunity. Restoring these reefs could generate a net benefit of $13.4 million, with a benefit–cost ratio of 1.10 (Cresswell et al., 2025). However, existing management frameworks constrain this potential.

The Victorian Sea Urchin Fishery (VSUF) has operated since 1985, transitioning from experimental permits to a licensed fishery in 2014. It is managed under the Fisheries Act 1995 (Vic) and Fisheries Regulations 2019 (SR No. 163/2019), which authorise the take of urchins “by hand for sale” through Sea Urchin Access Licences. Management is guided by the Sea Urchin Fishery Baseline Management Arrangements, currently under review to transition into a formal management plan. Licences are uncapped, but quota allocations are limited and held by existing operators, preventing new entrants. Each licence is linked to individual transferable quotas (ITQs), which operate as tradable assets. When Centro was removed from quota management in 2024, industry pushback highlighted the sensitivity of reform, as ITQs represent significant financial investments (VSUDA 2024).

A stock assessment in 2002 established a Total Allowable Commercial Catch (TACC) of 40 tonnes for Helio across four management zones to support the development of a commercial fishery (Worthington & Blount, 2003). The quota was based on extrapolated biomass estimates and assumed that urchins from barrens were unsuitable for harvest due to poor condition. However, new research estimates standing biomass in PPB at around 9,700 tonnes (Graham, 2023; Young et al., unpublished). Despite this, annual harvest remains low at 25-40 tonnes, less than 0.5% of the estimated stock. The exclusion of barren urchins creates a structural disincentive to target degraded areas.

Regulatory fragmentation also limits integration between wild harvest and aquaculture. While Section 49(2) of the Fisheries Act 1995 (Vic) permits aquaculture operations, current regulations do not explicitly allow the take and translocation of wild urchins under a Sea Urchin Access Licence into aquaculture systems. This gap prevents Victoria from adopting international models, such as those in Japan, where barren removals are linked to aquaculture conditioning (FAO 2022).

Reducing Helio densities below 4/m² supports kelp recovery and improves roe quality, showing that restoration and commercial value can reinforce each other (Blount et al. 2017; Miller et al. 2024). The policy challenge for Victoria is not whether harvest can aid restoration, but how to integrate barren access, quota reform, and aquaculture innovation into a framework that promotes both ecological recovery and industry resilience.

Policy Options

Option 1: Amend Fisheries Regulations 2019 (Vic) to Create a Category for Barren-Zone Harvest Strategy

Option 1 would amend the Fisheries Regulations 2019 (Vic) (SR No. 163/2019) to introduce a new Sea Urchin Access Licence category authorising the take and translocation of urchins from mapped barren reefs for aquaculture under Section 49(2) of the Fisheries Act 1995 (Vic). The Victorian Fisheries Authority (VFA) would lead implementation, with costs partially recovered through existing licence levies and application fees under the Fisheries (Fees, Royalties and Levies) Regulations 2017 (Vic). Based on Tasmanian precedent, annual costs of approximately $1 million would be co-funded, with industry contributing $0.15–0.25 million for permit processing and management, and government supporting ecological monitoring at $0.5–1 million.

This mechanism would allow operators to remove low-value urchins from barrens and repurpose them for aquaculture, thereby improving roe quality and market value. Risks include misclassification of reefs, potential drift of ranching toward closed aquaculture systems, and opposition from existing licence holders concerned about competition and asset value.

Option 2:  Amend the Fisheries Act 1995 (Vic) Section 64A Quota Orders to Include Spatial Barren-Zone Quotas.

This option would revise Section 64A of the Fisheries Act 1995 (Vic) to allow spatially distinct quotas, prioritising removal or translocation of urchins from identified barren zones while maintaining limits in healthy reefs. The VFA could use existing PPB reef codes to issue zone-specific quota orders, allocating higher removal limits for barren areas. Implementation, including stakeholder consultation, is expected to cost around $0.5 million, based on comparable quota reviews in the Victorian Rock Lobster Fishery.  Implementation responsibility lies with the VFA, in consultation with the Victorian Sea Urchin Divers Association (VSUDA), leveraging existing quota-setting mechanisms. This option leverages existing powers, integrates with current reef coding, and builds on adaptive management lessons from Tasmania. Limitations include compliance challenges and potential displacement of effort without strong monitoring.

Option 3: Review the Sea Urchin Fishery Baseline Management Arrangements

Undertake a review of the Sea Urchin Fishery Baseline Management Arrangements to establish optimal harvest and functional eradication targets for Helio and Centro across Victoria’s management zones. These benchmarks would formally integrate ecological thresholds, reducing densities below 4/m² in priority barren zones, into fishery operations. Implementation would cost about $1M over four years to support ecological assessments, stakeholder consultation, and the design of an adaptive management framework. Although slower to deliver than regulatory reform, this option would provide long-term clarity, strengthen accountability, and link harvest outcomes to measurable ecological improvements.

Policy Recommendation

The preferred approach combines Options 1 and 2. This reform would amend the Fisheries Regulations 2019 (Vic) to establish a new Sea Urchin Access Licence category under Section 49(2) of the Fisheries Act 1995 (Vic), authorising the take and translocation of urchins from mapped barren reefs for aquaculture and roe enhancement. At the same time, Section 64A would be revised to enable zone-specific quota orders that exempt barren reefs from existing limits while maintaining quotas in healthy reefs. Together, these options would enable targeted removal of urchins, support passive kelp recovery, and create a pathway for commercial value without undermining existing licence security.

This dual approach addresses current constraints by allowing barren harvest without devaluing existing licences. Creating a barren-only category would mitigate industry pushback observed after previous Centro quota changes (VSUDA 2024) while broadening the levy base to support research and compliance. Mapping should build on existing PPB reef surveys and vessel monitoring system (VMS) data to distinguish active fishing areas from barrens, ensuring removals occur only where densities exceed the ecological threshold of 4/m².

The Victorian Fisheries Authority (VFA) would lead implementation in partnership with  VSUDA, Abalone Council Victoria, Deakin University, and the Fisheries Research and Development Corporation (FRDC). Estimated costs are $1.2–1.6 million in the first year and $0.7–1.2 million annually. First-year costs are higher due to one-off establishment activities such as regulatory design, baseline data collection, and initial compliance setup, common in fisheries management reforms (Mangin et al., 2018). Industry would contribute $0.15–0.3 million per year through levies and fees, while government would fund ecological monitoring and enforcement ($0.5–0.9 million annually).

Achieving density reductions below 4/m² across 30–40% of mapped barrens within five years would represent substantial progress, consistent with ecological evidence that recovery is gradual and site-dependent (Kriegisch et al., 2016; Ling et al., 2009). This phased target also reflects current workforce and funding capacity, allowing adaptive scaling as early recovery indicators emerge. Importantly, restoring barren reefs would expand viable fishing grounds for existing operators, improving long-term fishery productivity and supporting sustainable industry growth.

Risks

Risk and Barriers

Implementing this reform presents challenges. Mapping and delineating barren reefs is technically complex and requires detailed ecological surveys to avoid misclassification. Workforce capacity within the VFA is limited, particularly for processing new permits, enforcing spatial quotas, and conducting ecological monitoring. Industry participation will also depend on the commercial viability of aquaculture ranching and roe enhancement, which remains unproven at scale in Victoria.

These barriers can be mitigated through partnerships with AgriFutures and the FRDC to strengthen mapping and monitoring. Interest from Deakin University’s AquaFI Lab and private investors in developing roe enhancement systems provides a foundation for pilot programs. Proactive consultation with current operators will be crucial to highlight that reducing barren densities improves reef health and expands productive fishing grounds, supporting the long-term viability of abalone, rock lobster, and other reef-dependent fisheries.

Social and political resistance may arise if new barren-harvest licences are seen to reduce quota value or alter market dynamics. Economically, reliance on roe enhancement and aquaculture exposes the sector to market volatility, as reduced demand or profitability could limit engagement. Environmentally, urchin populations fluctuate naturally, and intensive removals could risk overharvesting, though current harvest makes this unlikely.

Cultural risks may emerge if expansion proceeds without co-design with Traditional Owners, potentially conflicting with Sea Country values and responsibilities. Politically, the reform could face opposition if costs rise or ecological outcomes take time to appear. While these risks are manageable, they must be balanced against the far greater ecological and economic costs of allowing barren expansion to persist in PPB.

References

Bennett, S., Wernberg, T., Connell, S. D., Hobday, A. J., Johnson, C. R., & Poloczanska, E. S. (2016). The “Great Southern Reef”: Social, ecological and economic value of Australia’s neglected kelp forests. Marine and Freshwater Research, 67(1), 47. https://doi.org/10.1071/MF15232

Carnell, P. E., & Keough, M. J. (2019). Reconstructing historical marine populations reveals major decline of a kelp forest ecosystem in Australia. Estuaries and Coasts, 42(3), 765–778. https://doi.org/10.1007/s12237-019-00525-1

Carnell, P. E., & Keough, M. J. (2020). More severe disturbance regimes drive the shift of a kelp forest to a sea urchin barren in south-eastern Australia. Scientific Reports, 10(1), 11272. https://doi.org/10.1038/s41598-020-67962-y

Cresswell, K. A., Little, L. R., Hartmann, K., Gardner, C., Keane, J. P., Ling, S. D., &

Bradshaw, S. C. (2025). When overfishing is the sustainable option. Nature Sustainability, 8(5), 498–507. https://doi.org/10.1038/s41893-025-01526-8

Eger, A. M., Blain, C. O., Brown, A. L., Chan, S. S. W., Miller, K. I., & Vergés, A. (2024). Kelp forests versus urchin barrens: A comparison of ecosystem functions and services provided by two alternative stable marine habitats. Proceedings of the Royal Society B: Biological Sciences, 291(2034), 20241539. https://doi.org/10.1098/rspb.2024.1539

Graham, T. D. J. (2023). Restoration of kelp beds on degraded temperate rocky reefs (Doctoral thesis, Deakin University). Deakin University Research Repository.

Harianto, J., Carey, N., Byrne, M., & Przeslawski, R. (2020). Warming and acidification reduce the physiological performance of temperate sea urchins: Implications for ecosystem stability. Marine Environmental Research, 155, 104886. https://doi.org/10.1016/j.marenvres.2020.104886

Kriegisch, N., Reeves, S., Johnson, C. R., & Ling, S. D. (2016). Phase-shift dynamics of sea urchin overgrazing on nutrified reefs. Marine Ecology Progress Series, 558, 1–12. https://doi.org/10.3354/meps11894

Ling, S. D., Johnson, C. R., Ridgway, K., Hobday, A. J., & Haddon, M. (2009). Climate‐driven range extension of a sea urchin: Inferring future trends by analysis of recent population dynamics. Global Change Biology, 15(3), 719–731. https://doi.org/10.1111/j.1365-2486.2008.01734.x

Ling, S. D., Kriegisch, N., Woolley, B., & Reeves, S. E. (2019). Density‐dependent feedbacks, hysteresis, and demography of overgrazing sea urchins. Ecology, 100(2), e02577. https://doi.org/10.1002/ecy.2577

Mangin, T., Costello, C., Gaines, S. D., & Lynham, J. (2018). Are fishery management upgrades worth the cost? Proceedings of the National Academy of Sciences of the United States of America, 115(22), 5690–5695. https://doi.org/10.1073/pnas.1721392115 

Miller, K. I., Balemi, C. A., Bell, D. R., Blain, C. O., Caiger, P. E., Hanns, B. J., Kulins, S. E., Peleg, O., Spyksma, A. J. P., & Shears, N. T. (2024). Large‐scale one‐off sea urchin removal promotes rapid kelp recovery in urchin barrens. Restoration Ecology, 32(1), e14060. https://doi.org/10.1111/rec.14060

Minuti, J. J., Byrne, M., Campbell, H., Hemraj, D. A., & Russell, B. D. (2022). Live‐fast‐die‐young: Carryover effects of heatwave‐exposed adult urchins on the development of the next generation. Global Change Biology, 28(19), 5781–5792. https://doi.org/10.1111/gcb.16339

Pert, C., Swearer, S., Dworjanyn, S., Kriegisch, N., Turchini, G., Francis, D., & Dempster, T. (2018). Barrens of gold: Gonad conditioning of an overabundant sea urchin. Aquaculture Environment Interactions, 10, 345–361. https://doi.org/10.3354/aei00274

Spindel, N. B., Lee, L. C., & Okamoto, D. K. (2021). Metabolic depression in sea urchin barrens associated with food deprivation. Ecology, 102(11), e03463. https://doi.org/10.1002/ecy.3463

Thurstan, R. H., Brittain, Z., Jones, D. S., Cameron, E., Dearnaley, J., & Bellgrove, A. (2018). Aboriginal uses of seaweeds in temperate Australia: An archival assessment. Journal of Applied Phycology, 30(3), 1821–1832. https://doi.org/10.1007/s10811-017-1384-z

Unuma, T., Sakai, Y., Agatsuma, Y., & Kayaba, T. (2015). Sea urchin aquaculture in Japan. In N. P. Brown & S. D. Eddy (Eds.), Echinoderm aquaculture (1st ed., pp. 75–126). Wiley. https://doi.org/10.1002/9781119005810.ch5

Warren-Myers, F., Swearer, S., Francis, D., Turchini, G., & Dempster, T. (2019). Harvest method does not affect survival and condition during gonad enhancement of an overabundant sea urchin. Aquaculture Environment Interactions, 11, 143–148. https://doi.org/10.3354/aei00305

Worthington, D. G., & Blount, C. (2003). Stock assessment of the short-spined sea urchin (Heliocidaris erythrogramma) in Port Phillip Bay (Marine and Freshwater Resources Institute Report No. 47). Department of Primary Industries, Victoria.

Young, M. A., Critchell, K., Miller, A. D., Treml, E. A., Sams, M., Carvalho, R., & Ierodiaconou, D. (2023). Mapping the impacts of multiple stressors on the decline in kelps along the coast of Victoria, Australia. Diversity and Distributions, 29(1), 199–220. https://doi.org/10.1111/ddi.13654

Young, M., Graham, T., & Deakin University. (unpublished data). Estimates of Heliocidaris erythrogramma biomass in Port Phillip Bay derived from reef-scale abundance data.

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