The purpose of the Pumicestone Passage Shellfish Reef Restoration project is to restore shellfish reef populations for the benefit of the Moreton Bay ecosystem and the community.

Not only are shellfish a vital part of Indigenous cultural heritage, but they are also an incredibly important cog in marine ecosystems. Shellfish are fondly known as the 'kidneys of the coast' due to their natural filtration properties and their ability to improve water clarity by drawing in particles and distributing them to the seafloor.

Once grown, one shellfish can filter up to 100 litres of water a day, helping to create an environment that allows many other plant and animal species in estuaries and coastal bays to thrive.

The data and outcomes from this project can also be used to justify and inform larger-scale restoration efforts in other areas of Moreton Bay.

A bit of history

Up until the turn of the last century, Moreton Bay supported magnificent intertidal and subtidal shellfish beds which had always been a valuable food and cultural resource for Traditional Owners. The oyster industry was the foremost industry carried on in the early days of Moreton Bay’s history and local development. The oysters were used for a variety of purposes – not just eating. Queensland’s early roads were made out of shells from midden heaps, with live and dead oysters thrown into lime burners for cement. It did not take long for overharvesting, disease, and water pollution to deplete shellfish stocks to the point where they are now functionally extinct in Pumicestone Passage.

In 2015, Healthy Land & Water launched the Pumicestone shellfish habitat restoration project, alongside Traditional Owners, community and recreational fishing groups, a local oyster farmer, Moreton Bay Regional Council, Unitywater, and the University of the Sunshine Coast (USC), to work toward restoring Pumicestone Passage’s lost shellfish habitats.

After years of research, the project team settled on a plan to install artificial shellfish reefs in a Pumicestone Passage trial area. The artificial reefs are designed to provide an attachment point for shellfish, and the embedded recycled shells act as a food source for shellfish larvae as they mature. As shellfish populations expand, they support the growth of important fish species, enhance marine biodiversity and ultimately improve water quality in the Moreton Bay region.

Bureau Waardenburg’s Wouter Lenjkeek prepares the potato starch artificial reef he helped develop.

In December 2017, the first artificial shellfish reefs were installed within a one-hectare site offshore of Kakudu Beach at Bribie Island. The trial area is located within Moreton Bay Marine Park, and the artificial reefs were installed in an area with a depth range of between 2.5 and 5.2 metres.

Three different structures were embedded underwater, including patch reefs of shell weighted with reef balls, steel cages full of recycled shell, and an Australian-first biodegradable potato starch matrix that was developed in the Netherlands by Bureau Waardenburg. A combination of recycled and live shells was used within the structures.

In December 2018, a second array of artificial reefs were installed within the test area. The new reefs, made up of live and recycled shells collected by OzFish Unlimited volunteers at the Ningi Transfer Station, are designed to increase the process of reef adhesion and productivity.

The project is being monitored by the University of the Sunshine Coast marine science team. Since the first stage of reefs was installed in December 2017, initial results look promising.

A University of Sunshine Coast (USC) study released in late 2018 found fish abundance, species richness, and harvestable fish numbers had doubled since the installation. The potato starch matrix reefs appear to be the most successful installation so far, with the study finding the potato starch reefs are consistently surrounded by a higher average diversity and abundance of fish when compared to nearby control sites.

The study found evidence of prolific colonisation by corraline algae and soft corals, which helped cement the loose shells together into a reef formation. Most excitingly, fish distributions across the lower Pumicestone Passage have expanded slightly since the installations, and some species have moved closer to the reef areas.

However, much more data is needed before an accurate conclusion can be formed regarding the success of the artificial reef installations. Ongoing research by USC is analysing the broad effects of the trial and taking into account major seasonal variations that could impact the findings. 

This habitat restoration project is funded by the Australian Government's National Landcare Program.

This habitat restoration program is delivered in collaboration with the Pumicestone Passage Fish Restocking Association, Moreton Bay Regional Council, Boating Camping Fishing (BCF) through OzFish Unlimited, and Unitywater.

Significant in-kind support came from OzFish volunteers in their oyster gardening project, shell recycling, and invertebrate monitoring, the University of the Sunshine Coast, SunFish, Ngunda Joondoburri Land Trust, and Kabi Kabi First Nation.

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• Second stage of shellfish restoration project launched
  
• Historic bid to restore Pumicestone Passage shellfish habitat launches at Bribie Island
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