Moreton Bay – Shellfish Reef Project

All photography provided by Robbie Porter

INTRODUCTION

Moreton Bay has lost many thousands of hectares of fish habitat such as seagrass and saltmarsh but by far the biggest loss has been that of shellfish reefs (over 95%). These largely unseen and lesser known reefs were once the life blood of our bay. This project will restore these reefs.

WHAT HAPPENED TO THE REEFS?

Since European settlement oysters have been over fished. Many were harvested as food but the majority were harvested for the lime in their shells. This lime was used to make Cement for the building industry. Today in many places, including Moreton Bay, shellfish reefs are considered functionally extinct. After 2 centuries of dredging the sea floor, shellfish have no structures to grow on and the populations are too low to allow successful spawning. The lack of shellfish reef adversely affects water quality and aquatic life and they are not coming back without our help.

WHAT ARE SHELLFISH REEFS AND WHY DO WE NEED THEM?

Shellfish reefs are living ecosystems. They are made up by many shellfish but in Moreton Bay the main 3 reef forming species are;

·         Rock Oysters (Saccostrea glomerata)

·         Pearl Oysters (Pinctada albina sugillata)

·         Hairy Mussel (Trichomya hirsute)

These shellfish create complex and vertical structures which are ideal homes, breeding locations and food for a vast array of fish and other marine animals. Every hectare of living shellfish reef produces 1.5ton of fish.

Shellfish are nature’s water filters. A single adult oyster can filter nearly 200 litres of water every day. It is estimated that at the time of European settlement the oysters in Moreton Bay would filter a volume of water equal to the volume of water in the entire bay every week.

WHO WILL BENEFIT?

703,000 people, representing 17% of all Queenslanders recreationally fish every year making it one of our most popular pastimes. Restoring shellfish reefs will benefit;

·         Amateur and commercial fishers by increasing the volume of fish that can live and breed in the bay.

·         First Australians by reinstating an important traditional food source.

·         All bay users including; bathers and casual day users, boat users, charter and tour operators, scuba divers, school science groups, commercial and recreational wormers by improving water quality, fish numbers and reduce silt.

HOW WILL WE RESTORE REEFS?

Our project will recycle oyster shell collected from wholesale oyster handlers and restaurants. These shells are currently dumped as land fill. We will turn this rubbish into a valuable resource and use them to create shellfish reefs in Moreton Bay.

THE STEPS TO DO THIS ARE;

1.       Create an Oyster Shell Recycling Facility

2.       Collect oyster shell from seafood businesses and restaurants

3.       Dry these shells in the sun for 4 months to sterilise them and then wash them

4.       Place this clean shell into 1m x 1m wide x .5m high moulds that can be transported

5.       Place shell-filled moulds into the oyster lease so that oyster spat (baby oysters) can collect on the shells and grow on each other until they cement all of the shell together and form a clump of oysters called a “Bio Block”

6.       Leave these “Bio Blocks” on the lease for approximately 1 year until they are fully cemented together and the oysters are strong and healthy enough to survive transportation

7.       Take the Bio Blocks out of the moulds and return the moulds to the recycling facility for re-use

8.       Place the Bio Blocks, only containing oyster shell and living shellfish, back into Moreton Bay in areas where they once existed

THE RESULT

In the first year we will produce 200 Bio Blocks. They will be placed 3 metres apart and 3 wide in snaking ribbons on the sea floor. This way we will create a 300m x 6m wide oyster reef wildlife corridor.

We will scale this up over the coming 10years with the goal of creating 100 hectares of oyster reef in a decade.

CONCLUSION

This project is an essential step toward restoring the oyster reefs of Moreton Bay. The successful implementation of this plan will ultimately bring back hectares of fish habitat and improve the overall water quality and environmental diversity of Moreton Bay. Supplying native shellfish with viable host sites and injecting billions of living oysters into the environment will kick-start the regeneration of these reefs. Once established they will be self generating and continue to grow until they reach the level they were 2 centuries ago.  

WITH YOUR HELP, LET’S MAKE MORETON BAY A PRISTINE ENVIRONMENT WHICH CAN HELP OFFSET MODERN PRESSURES ON THE BAY.