Dr Ben Diggles1 (Ozfish), Porter R, Vardon K, Hawthorne S, MacFarlane C, Porter R, Porter J, Veary E, Veary A, Copeland C

Dr Ben Diggles is a marine biologist who specialises in study of the health of aquatic animals and their environment.  He is a director of DigsFish Services, an internationally recognised fish health consulting company based on Bribie Island, which was established in 2003 to provide aquatic animal health services to Industries and Governments throughout Australasia.  Dr Diggles has published hundreds of papers and reports over the past 30 years on issues as diverse as parasites and diseases of wild and aquacultured fish and shellfish, national and international biosecurity frameworks, pathogen risk analyses, fish welfare, fish kill investigations and environmental standards for fishing tournaments.  For more information, see www.digsfish.com

Abstract:

The Pumicestone Shellfish Habitat Restoration Trial was undertaken to investigate methods for restoring lost subtidal shellfish reefs in Pumicestone Passage, northern Moreton Bay.  Samples of recycled oyster shells deployed subtidally (3-5 meters depth) on experimental shellfish reefs were collected by divers every 3 months and examined for evidence of natural spatfall from rock oysters (Saccostrea, Ostrea, Crassostrea, Dendostrea spp.), other bivalves and invertebrate epibionts. After 12 months deployment, 7-meter diameter patch reefs constructed from recycled oyster shells that maintained a reef height > 50 cm above the surrounding substrate attracted natural spatfall ranging from 59 (covered) to 125 (uncovered) spat per 100 shells deployed, with 76% survival. Samples obtained from cage modules and a 2-meter diameter patch reef 24 months after their deployment found spatfall for the cage module had increased to 154 spat per 100 shells (82% survival), showing recruitment continued to occur at least 24 months post-deployment. In contrast, only 31 spat per 100 shells with low survival (19.4%) was evident on the 2-meter diameter patch reef after 24 months, probably due to reduced reef height (<20 cm) due to ongoing anchor damage. Biodiversity was high, with shells sampled from all reef types displaying colonisation by invertebrate epibionts which cemented shells into monolithic reef formations. Evidence of subtidal oyster spat recruitment and survival over successive years in uncovered shells piled > 50 cm above the bottom suggests that oyster reef restoration is feasible in Pumicestone Passage, and potentially also wider Moreton Bay.