Restocking Depleted Wild Stocks—Long-Term Survival and Impact of Released Blacklip Abalone (Haliotis rubra) on Depleted Wild Populations in New South Wales, Australia

Abstract

The potential for restocking with hatchery organisms as a tool to rebuild depleted populations of blacklip abalone (Haliotis rubra) was investigated through replicated, control-impact studies in New South Wales, Australia. Long-term survival (>2 years) of hatchery-reared and released abalone, their impact on wild abalone abundance, and the effect of diffuse versus concentrated release was investigated on natural reefs. Long-term survival of released hatchery abalone varied between releases but averaged about that expected for wild abalone. There was no significant effect of released juveniles on the persistence or recruitment of wild abalone. Significantly greater numbers of all (released and wild) abalone persisted at release locations through time, while the total number of wild abalone increased significantly through time at release and control locations. There was no significant difference in long-term survival of abalone released in clusters of high density (2–4%) or in a diffuse or concentrated array (0–9%). These results show that restocking can supplement natural rebuilding processes of depleted wild abalone populations in New South Wales, Australia.

Keywords:

• fishery
• stock-enhancement
• rebuilding
• management
• experimental controls

ACKNOWLEDGMENTS

Funding for this research was provided by the Australian Fisheries Research and Development Corporation (project no. 1998/219). The New South Wales Department of Primary Industries (Fisheries and Aquaculture)–Abalone Fishery Research Group provided significant in-kind support. Members of the NSW Abalone Fishery Industry provided strong support, and Southern Ocean Seafoods (NSW) Pty Ltd and Twofold Bay Quality Bait Supplies Pty Ltd assisted with the tanking of juveniles prior to release. The South Australian Research and Development Institute (Aquatic Sciences) provided valuable support for completion of this manuscript. Peter Gibson, Craig Brand, Judy Upston, and Craig Blount provided invaluable field support. Mike Heasman, Nick Savva, Craig Brand, and Peter Gibson supported the rearing of all abalone. Valuable advice and comments on this research and/or improvements on the manuscript were provided by Neil Andrew, Peter Cook, Cameron Dixon, Kai Lorenzen, Stephen Mayfield, Craig Mundy, Ben Stobart, and two anonymous reviewers.