Oysters and mussels return to Gippsland Lakes thanks to three year restoration project

An area larger than the MCG’s playing field has been successfully populated with oysters and mussels in a big win for Gippsland Lakes health.

What happened: A three year reef restoration project in Gippsland Lakes has been recognised by the United Nations after showing significant signs of recovery, with mussels, native oysters and marine life flourishing.

Why do Gippsland Lakes need restoring?

The program manager at the East Gippsland Catchment Management Authority, Sean Phillipson, told the Monitor that Blue Mussel and Australian Flat Oyster reefs were once abundant across Victoria and South Australia – but fell into decline from overharvesting, pollution and waterway changes. 

• 🗣️ “Physical disturbance to the reefs are the most likely cause of decline,” Phillipson said. “Changes in water quality and other environmental conditions are also factors.”

In Victoria, more than 95 percent of shellfish reefs that once covered the bays and estuaries in the state have been lost.

• An oyster dredge fishery, which operated in the Gippsland Lakes in the 1920s and a Blue Mussel fishery, which operated in the lakes from the 1970s to the 1990s likely contributed to the decline in the shellfish reefs.

Three year plan: In March 2022, The Nature Conservancy (TNC), with support from the East Gippsland Catchment Management Authority, began restoration work on 2.5 hectares of reef at a site near Nyerimiland, located between Lakes Entrance and Metung.

• The project is part of TNC’s national Reef Builder project, which aims to restore shellfish reefs at 21 locations around the country.

How to build a reef?

Phillipson said: “The first step is planning where the reef patches will go, and then the work is actually relatively simple.”

After 17 reef patches were chosen, locally-sourced limestone rock was placed onto the Gippsland Lakes seabed at the locations, forming the base of the shellfish reefs.

🗣️“The lake bed is essentially sand or mud. Placing limestone provides a hard surface, because mussels and oysters need a hard substrate to attach to when they're little, tiny larvae and grow,” Phillipson said.

Baby Australian flat oysters are then placed on the limestone to form the basis of the reef. 

• Blue Mussels, which naturally form in the lakes, will then grow on top of the limestone and oysters in time.

🗣️“The oysters grow on top of each other, and you get this three dimensional building of shellfish on shellfish, kind of like a coral reef,” Phillipson said.

• “It creates structural complexity on the lake bed, and that encourages all sorts of stuff. Not only shellfish, but there’s homes for seahorses, fish and crustaceans.”

Great success: Recent surveys revealed a thriving underwater ecosystem, with mature Blue Mussels carpeting the seafloor, large Australian flat oysters, and a diverse mix of marine life including fish, sea stars, crabs and nudibranchs.

Phillipson said the restoration has brought back a thriving ecosystem that was lost. 

• 🗣️“A complex underwater habitat is great for marine biodiversity. It's the basis of the food chain.”

Shellfish reefs also keep waterways healthy by filtering water, which supports fish populations.

United Nations recognition

In December last year, the project became the first Australian initiative recognised as a UN World Restoration Flagship, a designation that honours the best examples of large-scale and long-term ecosystem restoration around the world.

• The designation recognises “the planet’s most ambitious, science-based and inspiring examples of large-scale ecosystem restoration”.

More than 150 local residents and school children also participated in citizen science activities around the reefs, with support from Friends of Nyerimilang, Nungurner Primary School and the Gippsland Lakes Fishing Club.