New oyster reefs in Oyster Harbour exceeding expectations in a bid to restore populations

Oyster Harbour is returning to its former glory with the results of two new oyster reefs built last year exceeding the expectations of researchers.

One million juvenile Australian flat oysters were released onto the reefs in January.

The reefs, built by The Nature Conservancy, cover 1650sqm of Oyster Harbour’s sea floor.

An additional 2000 mature oysters, grown at the Harvest Road aquaculture lease, were placed on the reefs with the hope of kick-starting the natural recruitment life cycle.

Project co-ordinator Alex Hams said the health of the oyster population — and the overall marine biodiversity — was better than he had hoped.

“Recent diving surveys indicate that survival of the oysters we placed on the new reefs is above our benchmark,” Mr Hams said. “In fact natural recruitment is exceeding mortality at one of the sites.

“Marine biodiversity has also increased in the area. For example, the reefs have enhanced the abundance of fish, particularly key recreational and commercial species such as juvenile pink snapper.”

The Australian flat oyster takes two to three years to reach maturity.

Given the right conditions, Mr Hams said they could live for more than 10 years.

“The oysters we have seeded onto the reefs in Oyster Harbour have already shown good levels of growth, with some of the front runners expected to reach breeding size by the end of 2021,” he said.

“It is important that the oysters are given a chance to reach this stage so that the population is resilient and sustainable, and show that we can recover an ecosystem on the brink of extinction.

“The oysters and other marine life that are growing on the reef will continue to grow and colonise the reefs until it reaches an equilibrium.

“In similar projects conducted elsewhere, this has been shown to take about five to seven years, at which time the oyster population will be self-sustaining and producing the next generation of oysters to maintain and hopefully grow their numbers.”

The reefs are part of the The Nature Conservancy’s national reef building project, which aims to build 60 new shellfish reefs by 2025. The Nature Conservancy says if they succeed, Australia will be the first country to recover a critically endangered marine ecosystem.