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AEI 10:345-361 (2018)  -  DOI:

Barrens of gold: gonad conditioning of an overabundant sea urchin

Cassandra G. Pert1,2,*, Stephen E. Swearer2, Symon Dworjanyn3, Nina Kriegisch4, Giovanni M. Turchini5, David S. Francis5, Tim Dempster1

1Sustainable Aquaculture Laboratory - Temperate and Tropical (SALTT), Department of Biosciences, University of Melbourne, Victoria 3010, Australia
2National Centre for Coasts and Climate (NCCC), School of Biosciences, University of Melbourne, Victoria 3010, Australia
3National Marine Science Centre, Southern Cross University, Coffs Harbour, New South Wales 2450, Australia
4Institute for Marine & Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia
5School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia
*Corresponding author:

ABSTRACT: Overgrazing by the overabundant native purple urchin Heliocidaris erythrogramma has caused kelp-dominated reefs to shift to urchin barrens throughout southeastern Australia. These areas are characterised by low kelp abundance, low biodiversity and high urchin densities. As purple urchin gonads are a delicacy in many countries, commercial harvest from barrens could aid kelp recovery. However, the lack of macroalgae in these habitats, driven by high urchin densities, results in urchins with small, poor-quality roe that is commercially undesirable. To overcome this, we assessed whether urchin gonad quantity and quality could be improved with access to high-quality feed and optimal environmental conditions, a process known as ‘gonad conditioning’. Specifically, we (1) surveyed the quality of urchins from barrens and kelp sites in Port Phillip Bay, Australia, over 18 mo and (2) tested if gonad conditioning was effective on urchins from barrens during and after the harvest season. Field surveys revealed considerable variation in gonad size across sites, habitats and collection periods (mean gonad index range: 3 to 12%). Gonad conditioning with the best diet increased urchin gonad size by up to 2.8 times during the harvest season. Moreover, gonads of conditioned urchins from one barren were 3 times brighter in colour and contained lower concentrations of arsenic than wild urchins. In contrast, gonad conditioning at 22°C after the harvest season was ineffective. Our results show that targeted in-season harvest from barrens and subsequent gonad conditioning produces roe of commercial quality, promoting the use of urchin fisheries as a tool for managing urchin barrens.

KEY WORDS: Roe enhancement · Heliocidaris erythrogramma · Aquaculture · Urchin barren · Temperature · Purple urchin

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Cite this article as: Pert CG, Swearer SE, Dworjanyn S, Kriegisch N, Turchini GM, Francis DS, Dempster T (2018) Barrens of gold: gonad conditioning of an overabundant sea urchin. Aquacult Environ Interact 10:345-361.

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