Innovative trial could be game-changer in restoring Australia’s shellfish populations

A new product being trialled in South-East Queensland could be a game-changer for shellfish restoration in Australia.    
  

A mesh bag made from biopolymers from 100 per cent vegetation that has been sustainably sourced is being tested to see if they can grow oyster clusters in the Maroochy River and Moreton Bay.  
  

OzFish Unlimited,  Australia's fishing conservation charity, has teamed up with Healthy Land and Water through the National Landcare Program and the Bunya Bunya Country Aboriginal Corporation to test out the pilot project.  
  

OzFish is using the trial to see if the mesh bags (known as BESE bags) could become a lightweight alternative to the Robust Oyster Baskets (ROBs), which are used to restore shellfish populations but are much heavier, expensive and more time consuming to construct.  

“The biggest issue is not just getting the shell in the water.  We want to create a 3-D structure to allow more organisms to grow on the shell such as baby oysters and also to provide habitat for fish,” said Abbie Taylor, OzFish Project Manager – South-East Queensland.    
  

“By creating a structure that’s got that height and complexity, you’re creating multiple areas for new oysters to recruit and creating additional habitat for crabs, worms, snails and all those other critters to hide in.    
 

“One of the benefits of this bag is they slot into each other. They’re like sandbags - they’ll cement in with each other.”  

OzFish volunteers and members of the Bunya Bunya Country Aboriginal Corporation placed 90 bags each at oyster leases in Moreton Bay and Bli Bli on the Maroochy River as part of the trial.   
  

“They come in 100-metre lengths and you can cut them to size. They’re super easy to fill. It’s like a sausage skin, you have a big roll and tie off one end with a knot or a C clip and you put it in a bucket, fill it with shell and then tie off the other end,” Taylor added.    

Dr Ben Gilby, a Senior Lecturer in Animal Ecology at the University of the Sunshine Coast, has been working with OzFish for several years and he is confident this project will deliver on multiple fronts, including water quality. 
  

“One adult oyster filters one bathtub of water per day. They take in a lot of nitrogen and a lot of pollutants out of the water column, which is one of the most important things they do,” he said.  

“They’re even doing things like taking sediment out of the water when floods come through and literally deposit it underneath them and store that for many years. They’re very efficient little creatures.”  

The BESE bags have been placed in intertidal areas and it will not be known until the end of the year at the earliest whether the trial has been successful with one of the main concerns that the local wildlife will find the material too tasty to resist.  If the trial works, they could be deployed in coastal and inland areas throughout Australia.    

Since European settlement in Australia in the late 1700s, shellfish have been nearly wiped out in many areas to critically endangered levels.  
  

“The best estimates are that somewhere between 96-99% of oysters are gone from Moreton Bay,” Dr Gilby added. “We talk a lot about endangered ecosystems like corals and seagrass but there’s none worse than oysters.”  

This project was funded by the Healthy Land and Water, the Australian Government’s National Landcare Program, OzFish Unlimited and BCF – Boating, Camping, Fishing.