New oyster habitats show that Moreton Bay is no longer a basket case

Oysters are thriving on volunteer-built baskets dotted up and down Brisbane’s coast.

The baskets, which were developed by not-for-profit OzFish, have been shown by scientists to house 3 million new oysters, and 4.5 million other animals.

“By returning oysters, it’s not just about the individual animals. It’s like returning coral reefs – you’re returning an entire ecosystem,” says Marina Richardson, a PhD candidate at Griffith University, who led the research.

“These oysters are actually habitat forming: they build these three-dimensional reef structures. And with those reef structures, you get the entire food web that goes along with it – so everything from little worms and amphipods, to your middle predators, and then all the way up to your top predators, which will come in and feed on them.

“They’re also filter feeders. So it’s returning those water filtration ecosystem services that we’re missing.”

Richardson says that the once-great oyster ecosystem in Moreton Bay had collapsed in the 19^th century, thanks to lime-burning and unsustainable harvesting by Europeans.

But the baskets look like they can help restore the environment.

Read more: Next Big Thing: Oysters natural?

“They have been deploying these into different locations – an intertidal location to test that out, and then at their restoration site at the Port of Brisbane, which is subtidal,” says Richardson.

The baskets were developed by Robbie Porter, a senior project officer at Ozfish, after years of trialling different methods. They’re called robust oyster baskets, or ROBs.

The ROBs look like triangular steel cages, about the size of an oven. OzFish has deployed 4,000 of them around the Brisbane coast.

“We thought for years that the baskets seemed to be working, but we wanted a scientific assessment and invited the Griffith University team to verify just how many shellfish and other animals were there,” says Porter.

Richardson said the oysters were counted with the help of third-year undergraduate Griffith students in an estuarine ecology course.

“We collected them from both the intertidal and subtidal locations, and then they [the students] worked in collaboration with Ozfish, and also under researchers at Griffith, to quantify the abundance and diversity of invertebrates that had moved into the robust oyster baskets, and they also counted the shellfish as well.

“We could compare which areas had sort of the greatest number of spats – that’s baby oysters – and adult oyster recruitment, as well as the overall community.”

Read more: Indigenous people farmed oysters sustainably for 5000 years

Based on the samples they collected, the researchers calculate that the baskets have housed 3 million new oysters in the area, and 4.5 million other species.

Richardson says it should be straightforward to scale up the ROB deployment.

“Because ROBs don’t rely on hatchery-produced spat, their use can be widespread.”

The team is now planning to work with local authorities to see if they can deploy and assess ROBs at a larger scale.