The property market might be booming around Noosa's waterways, but beneath the sparkling surface a very different population is dwindling.
Hundreds of kilograms of Sydney rock oysters are being added to the waterways around the Sunshine Coast town to bring a once thriving population back from the brink of extinction.
It's one of 13 locations across Australia, part of a federal government-funded program to help ecosystems recover from overfishing and habitat loss in the past century.
The Nature Conservancy's Megan Connell said the oysters would be added to new human-made reefs and "oyster gardens" under jetties to improve water quality and boost aquatic life.
"Oysters are ecosystem engineers," she said.
"They form the basis of the oyster reef ecosystem. They are the food for a range of fish species and they will also bring a number of other species in to live in the reef as well."
She said an adult oyster could filter about a bathtub of water a day.
"The main reason why we're doing this is to improve the biodiversity of the Noosa River, to create habitat and to improve the overall health of the river," Ms Connell said.
She said oyster populations in the river had been decimated since European settlement.
"Up until the early 1900s, oysters were prevalent but in the last 100 years or so, they've been pretty much completely gone," Ms Connell said.
How to grow an oyster?
The new shellfish were spawned from adult oysters taken from the Noosa River to a Bribie Island research facility.
Scientist Max Wingfield said it was a hands-on job to breed oysters in captivity.
"When they spawn, you can tell the males from the females and then we just manage the fertilisation," he said.
"When you've got a lot of oysters in a small amount of water, you've got to make sure that you get good genetic diversity.
"Then we grow them through in these tanks for three to four weeks through their free swimming planktonic larval stage.
"When the oysters are ready to stop swimming and turn into little baby oysters … we let the larvae settle and attach on the shell."
Larvae settled onto shells
To minimise waste, shells collected and dried locally around Noosa were used to grow the oysters on.
Mr Wingfield said it was the first time Sydney rock oysters had been settled onto shells for a reef restoration project.
"With a good spawn, they might produce five or six million eggs," he said.
"The aim is to produce 1.5 million spat to go out onto the oyster reefs, so that equates to about close to 500 of these bags of the oyster shells."
Coming full circle
Noosa Yacht and Rowing Club head chef Brandon Hanak said thousands of shells had already been collected for the project after the oysters were eaten by customers.
"There's probably about 20 to 40 dozen oysters [shells] collected per day here at the yacht club, and up to 30 dozen to 40 dozen per day on the weekends," Mr Hanak said.
"They normally go in the bin and they go into landfill, so this is a really good way to recycle."
Recovering marine ecosystems
The Nature Conservancy aimed to protect and restore 60 shellfish reefs across Australia and make it the first nation to recover a critically endangered marine ecosystem.
Noosa is the only Queensland location involved in the national reef building project.
"We're restoring four different locations, Tewantin, Goat Island and two locations in lower Weyba Creek," Ms Connell said.
She urged the Noosa community to help the oysters thrive.
"There's no restrictions on people fishing or collecting from our reefs," Ms Connell said.
"However, we're encouraging the local community to let the reef restoration process occur.
"It's really important to leave the reefs alone as much as we can."
