Subtidal reef for native oysters in Inner Harbour, Port River

December 5, 2018

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3 layer design of subtidal reef by Phill McPeake

3d design for subtidal reef, developed by Phill McPeake

A small trial reef, for native oysters, was built today in the Inner Harbour.

Foundation trials have shown, to date, that our native oysters Ostrea angasi (as adults and spat) are able to thrive in the Port River, living in oyster baskets.

Consequently, the Port River Shellfish Restoration Project team has been investigating how substrate might provide a more permanent home.

The Foundation has brought together lots of volunteer resources to trial a reef constructed from clean recycled shell in coir bags. The idea of using the shell in bags was stimulated by the example of OceanWatch in Sydney Harbour and the bags sourced from them.

With approval through a PIRSA Permit, and with the assistance of The Nature Conservancy, clean recycled Pacific oyster shell was sourced from SA oyster growers. The shell was sorted and bagged in Ardrossan and brought to Adelaide by ECF volunteers.

Renewal SA provided a Permit for the reef to be constructed in the Inner Harbour. The site, just to the north east of the Jervois Bridge, is within the Permit Area and chosen because of the wooden boards there on the River floor.

The reef was constructed today with 3 layers of bags, following Phill McPeake’s design, plus some terracotta tiles. Last year terracotta tiles proved effective as settlement plates for native oyster spat, when some of our adult oysters spawned.

The water temperature today was 21 degrees, and we’ve seen some spat on our tags, so we hope we’ve not missed this year’s spawning season.

The build was made possible by the involvement of Port River Shellfish Restoration Project team members, especially Travis Howson with his punt and skippering skills, Phill McPeake who directed construction and Steve Reynolds of the Marine Life Society who recruited the diving team. The team of four BSAC Adelaide divers did the work of guiding the bags into place and joining the bags underwater at the corners of the structure.