For thousands of years, shellfish reefs have been synonymous with Indigenous culture and the Moreton Bay region. Since European settlement, these once thriving marine communities have lost 95% of their habitat in the Pumicestone Passage due to unsustainable harvesting, disease, poor water quality, urbanisation and industrial pollution.
In 2015, Healthy Land and Water began coordinating the Pumicestone Shellfish Restoration Project by developing the experimental design, raising community awareness and collaborating with Traditional Owners. By December 2017, approvals were granted allowing Healthy Land and Water, alongside project funders Unitywater, Moreton Bay Regional Council and state and federal government, to begin the innovative approach to improve water quality through the delivery of biofiltration and increased fish stocks.
The project will be monitored for three years by the University of the Sunshine Coast marine science team. It is expected the trial will later encompass the entire Moreton Bay Marine Park with hopes of shellfish reefs being fully restored.
Our valuable partners include Joondooburri Trust, Kabi Kabi First Nation, Sunfish, Digsfish Services Pty Ltd, Carlo Sain, University of the Sunshine Coast, Ozfish, the Community Benefit Fund and the Regional Landcare Facilitator Program.
The intent is to restore previous shellfish habitat for environmental remediation and as fish habitat and to acknowledge and protect Aboriginal cultural heritage values. If the concept can be proven on a small scale by the establishment of self-sustaining subtidal oyster reefs in Pumicestone Passage which are accompanied by improvements in fisheries production, these data can be used to justify and inform estuary restoration efforts in other areas of Moreton Bay and/or on larger scales.
The approved one hectare trial area is within the Moreton Bay Marine Park, and outside the Mooring Zones, Fish Habitat Area, Navigation Channel, located in an area with depth range of -5.2 to -2.5 metres Highest Astronomical Tide. All of the Pumicestone Passage is within the high risk maritime development zone. Achieving state government approval as one of the first such approvals in Queensland was a protracted process with agencies working together to ensure the outcomes are legislatively and ecologically sound.
This trial installed in December 2017 features a variety of reef structures including patch reefs of shell confined by reef balls, steel cages with shell, and a biodegradable potato starch matrix (BESE- Elements) developed in the Netherlands by Bureau Waardenburg, used here for the first time in Australia. Live and dead shell were used.
Preliminary monitoring results are promising with fish mapping by University of the Sunshine Coast showing a doubling of total fish abundance, species richness and harvestable fish abundance at the reefs site, when compared to nearby control sites. It appears the BESE-Elements reefs were consistently surrounded by a higher average diversity and abundance of fish, than at the nearby control sites and at the other reef deployment methods. Also it appears fish distributions across lower Pumicestone Passage have been modified slightly following the installations of the reefs, with some species having moved closer to the reef area. Much more data is needed before we can properly analyse these broad, seascape-scale effects, and account for the major seasonal variations that take place in the system.
The invertebrate monitoring results undertaken by OzFish Unlimited at nine months after installation are also promising, confirming that natural S. glomerata spatfall occurred subtidally in the restoration area, with an average of 56.16 spat collected from 100 shells. Spatfall was highest on shells in crate modules (mean 80.33 spat per 100 shells, range 64-98) and lower on patch reefs (mean 32 spat per 100 shells, range 28-34). Also evident was prolific colonisation by corraline algae and soft corals, which helped cement the loose shells together into a reef formation.