Parts of the Freycinet Commonwealth Marine Reserve (CMR) east of Tasmania were opportunistically mapped by the Marine Biodiversity Hub during transit voyages between Hobart and the Flinders CMR, a focus of Hub research. The transit mapping, plus additional, targeted transects, revealed relict coastline reefs in 80─100 m depths extending north of Bicheno. The reefs appear relatively continuous in the CMR, and provide important habitat for Stripey Trumpeter, an important species for commercial and recreational fishers.
Further mapping detected reef features inshore of the relict coastline: complex granite reef systems supporting more substantial fish and invertebrate assemblages. Most notable was a 200 m long granite reef 7 km south-east of Bicheno that rose sharply from 80 m to 60 m. Benthic habitats and biodiversity have been photographed in repeated surveys with an autonomous underwater vehicle (AUV).
(AUV surveys were begun at Freycinet CMR during the Commonwealth Environment Research Facility Marine Biodiversity Hub; later surveys have been supported by the Integrated Marine Observing System, the Institute for Marine and Antarctic Studies and the Department of the Environment.)
Preliminary examination of the AUV imagery indicates that the relict reef systems are generally very low profile and partially sand-inundated, with a sparse coverage of sponges and similar invertebrates, few benthic fish, and with distinct brittlestar aggregations at the reef to sand interface. In stark contrast, the granite reef has an extensive and complex sponge, bryozoan and ascidian fauna and an abundant fish assemblage, dominated by Butterfly Perch.
Further work on the AUV imagery would provide a greater understanding of bioregional patterns, and year-to-year variability in biological indicators of change. The acquired imagery and metadata is available on the Australian Ocean Data Network.
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