Shellfish Reef Restoration in Pumicestone Passage – MBRC Briefing Note 8 April 2015
Dr B K Diggles, DigsFish Services, Banksia Beach, ben@digsfish.com
Executive Summary

Shellfish reefs (oysters, mussels etc.) are “the lungs” of healthy estuaries, providing
various “ecosystem engineering” services including filtering to clean the water, shoreline
stabilisation and food for fish and crabs. However, < 5% of historical oyster populations
remain in Pumicestone Passage, due mainly to disruption of their breeding cycle.

Restoration of lost subtidal shellfish reefs has provided substantial improvements to
water quality, fisheries habitat and ecosystem productivity in other parts of the world; e.g.
o
o
o
in NZ, subtidal mussel reefs had 1370% more fish compared to control areas
shellfish reefs in the US removed up to 283% more nitrogen than mud banks
shellfish reefs in the US result in cleaner water, less turbidity and seagrass recovery

Precedents have been set with shellfish reef restoration projects in the USA, NZ and now
in Port Phillip Bay, Victoria. There is considerable community support (including
environmental, indigenous and recreational fishing groups) to undertake a shellfish
restoration project in Pumicestone Passage.

The shellfish in restored reefs are not for harvest for human consumption, but are placed
in the ecosystem for environmental remediation (water filtration and uptake of nitrogen,
carbon etc.) and as fish habitat (i.e. “natural artificial reefs”).

Small scale trials in Pumicestone Passage have indicated restoration of subtidal shellfish
reefs is feasible, and improvements in fish and invertebrate biomass of 500-1000% (or
more) can be expected if shellfish reefs can be restored on a large scale.

Funding estimates have been developed for a scientifically monitored pilot shellfish reef
restoration project in Pumicestone Passage. Initially, $50,000 is required for detailed
mapping and permit approvals (Phase 1). The Toorbul Fish Stocking Association Inc.
has raised c. $50,000 for Phase 2 (on water R&D trials). The community is looking to
various other sources for the remaining funds required (c. $310,000 +) for Phase 2.

The Moreton Bay Regional Council is in a prefect position to help get the ball rolling in
this regard, and SEQ Catchments seek funding from MBRC for Phase 1 (planning,
permitting, $50,000) and a contribution towards Phase 2 (R&D, $100,000 +).

Economic analysis suggests that shellfish reef restoration projects will yield full return on
investment in c. 5 years, based on improved fisheries yield alone, ignoring the probable
longer term economic benefits from increased fishing and wildlife associated tourism,
reduced likelihood of nuisance algal blooms etc., and so on.

If the concept can be scientifically proven on a pilot scale, these data can be used to
justify larger scale restoration efforts using funding from development offsets (based on
nitrogen and carbon sequestration models), investments by Government, as well as
donations from private companies, the fishing industry and the general public.
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Introduction

Reefs of filter feeding shellfish (oysters, mussels etc.) are “the lungs” of healthy
estuaries, providing various “ecosystem engineering” services including:
o food and habitat for fish and crustaceans
o filtration of water which reduces turbidity and nutrient loading
o carbon sequestration and nutrient cycling (uptake of nitrogen)
o bentho-pelagic coupling (transferring energy from the sun via phytoplankton into
animal material)
o shoreline stabilisation and more.
Shellfish reefs are ecosystem
engineers



Historically,
Pumicestone
Passage had very large
populations of Sydney rock
oysters and hairy mussels both
intertidally and subtidally in
reefs down to around 4 meters
below the low tide mark.
These shellfish were an
important source of food and
materials
for
indigenous
people and early European
settlers, and thus are of great
historical
and
cultural
significance.
However today, shellfish reefs are functionally extinct in many estuaries along Australia's
east coast. Research has shown less than 5% of historical oyster reef remains in
Pumicestone Passage, with the 95% loss occurring over the last 150 years.
Historical overfishing destroyed many reefs but today the mechanisms disrupting
shellfish populations appear mainly due to poor water quality linked to urban and
agricultural runoff and sewerage contamination. These immunosuppress the shellfish,
resulting in disease, while siltation and eutrophication (excess nutrient loading) prevents
oyster and mussel recruits from being able to settle on subtidal surfaces, disrupting their
lifecycle and preventing natural regeneration of shellfish reefs without intervention.
Only in the last 10-15 years have scientists realized the importance of actively restoring
shellfish reefs in estuarine ecosystems, in order to regain the lost ecosystem services.
Restoration of shellfish reefs

Restoration of lost subtidal shellfish reefs has provided substantial improvements to
water quality, fisheries habitat and fisheries productivity in other parts of the world. e.g.
in NZ, subtidal mussel reefs had 13.7 times (1370%) more fish compared to control
areas, while researchers in the US have measured 10-100 times (1000%-10,000% !) more
2




biomass of fish and large invertebrates on restored oyster reefs, as well as 283% increase
in nitrogen uptake in comparison with adjacent sand/mud banks.
In the US, restoration of shellfish reefs is seen as a critical component of the estuarine
rehabilitation process as they restore degraded estuaries to regain lost ecosystem services.
Without shellfish reefs, full recovery of seagrasses seldom occurs and the estuary remains
vulnerable to algal blooms, low dissolved oxygen and other problems.
The shellfish in restored reefs are not for harvest for human consumption, but are placed
in the ecosystem solely for environmental remediation and as fish habitat (i.e. “natural
artificial reefs”).
Precedents have been set with shellfish reef restoration projects in estuaries overseas (e.g.
Chesapeake Bay, USA1, Hauraki Gulf, New Zealand2, while Australia’s first shellfish
reef restoration project is now underway in Port Phillip Bay, Victoria3.
Australia’s first national shellfish reef restoration workshop was held recently in
Melbourne (6 Feb 2015), and a national strategy document is in preparation.
Proof of concept micro trials
Dr Ben Diggles and Ningi oyster grower Carlo Sain conducted a micro-trial over 7 weeks from
October till mid December 2014 to measure whether oysters would naturally recruit to clean reef
building material placed in Pumicestone Passage. The trial involved placing 5 kg of clean oyster
shells at 3 levels: intertidally, subtidal A (2.1 meters below low water) and subtidal B (3.1 meters
below low water). The results found
50
that oyster spat settlement increased
Spatfall per kg
with water depth (Fig. 1), showing that
of shell
40
oyster reef restoration is a feasible
option for Pumicestone Passage.
30
The most exciting data was related to
20
recruitment of fish and invertebrates to
the oyster shell substrates. Clumps of
10
many hundreds of embryonated fish
eggs were observed only in oyster shells
0
taken from subtidal collectors (Fig 2),
Intertidal
Subtidal A Subtidal B
while invertebrates such as mud crabs
(0 m)
(-2.1 m)
(-3.5 m)
and small black grapsid crabs (c. 10 mm
Fig 1. Oyster spatfall at different water depths.
wide, Fig. 3) were 4 to 5 times more
abundant in oyster shells held in subtidal collectors. This suggests that given 95% of subtidal
oyster reef area in Pumicestone Passage has been lost, improvements in fish and invertebrate
biomass upwards of 500-1000% (or more) could be expected if subtidal shellfish reefs could be
restored in Pumicestone Passage on a large scale. This would be a similar result to those
described in previous shellfish reef restoration projects conducted overseas.
1
http://www.chesapeakebay.net/trackprogress
http://reviveourgulf.org.nz/about.html
3
http://www.natureaustralia.org.au/news/melbournes-lost-reefs-rediscovered.xml
2
3
Figs 2 (left) and 3 (right). During small scale R&D trials, large numbers of fish eggs (left) and small crabs (right)
were found to recruit to subtidal (but not intertidal) shellfish reef material placed in Pumicestone Passage.
Community support for shellfish reef restoration
Shellfish reef restoration projects in other parts of the world have generated significant
community support because of their many cultural, social and economic benefits. Locally, the
concept has generated significant support from the community, including traditional owners such
as Ngunda – Joondoburri and Gubbi Gubbi, fishing groups such as the Toorbul Fish Stocking
Association and Sunfish Moreton Inc., local oyster farmers and conservation groups. We also
have support from catchment management and NRM groups including SEQ Catchments, the
Healthy Waterways partnership, as well as from scientists in the QLD State Fisheries
Department. Projects like this would raise community awareness of issues related to the health
of local waterways, and would provide a message to the public that “something tangible” is
being done to improve the aquatic environment in Pumicestone Passage and Moreton Bay.
Scientific research and development needs
Prior to undertaking a full scale shellfish reef restoration project in Pumicestone Passage, some
research and development is necessary in order to gain the most out of the process long term.
The R&D needs at this time include:
Phase 1
 Conduct studies to precisely determine times of peak natural shellfish spat settlement.
 Identify suitable areas where historic shellfish reefs were present in water >2-3 meters
deep at low tide in Pumicestone Passage.
 Liase with stakeholders, government authorities and wider community to identify suitable
sites for a pilot reef restocking project and obtain permissions. Criteria should include no
disruption to navigation, hard bottom, depth sufficient to make it difficult for public to
destock reefs.
 Obtain permissions/permits from relevant authorities (Marine parks, QLD Transport etc)
Phase 2
 Conduct baseline surveys of biodiversity, biomass and disease prior to reef restocking.
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
Compare effectiveness of several different methods of construction of shellfish reef
modules (different materials, structure/relief/water depth, regular maintenance or “set and
forget”) for recruitment and growth of oysters, mussels, invertebrates and fishes.
 Scientific monitoring of shellfish growth, survival, diseases, carbon and nitrogen uptake,
water quality (improvements in clarity, nutrients etc.) and fisheries productivity (fish
catch rates, seagrass coverage) to quantitate the effectiveness of the process.
Phase 3
 If the concept can be proven on a small scale and significant improvement in fisheries
production and/or water quality are measured, these data can then be used to design
environmental offset models to fund estuary restoration efforts on larger scales and/or in
other areas of Moreton Bay.
Funding and return on investment
Analysis suggests that shellfish reef restoration projects will yield full return on investment in c.
5 years, based on improved fisheries yield alone (Creighton et al. 2015). Other economic
benefits likely to accrue are related to improved water quality (reduced frequency of algal
blooms, seagrass regeneration due to improved water clarity, improved light penetration from
shellfish filter feeding and increased nutrient availability from shellfish faeces). The present net
socio-economic and cultural losses from missing shellfish reefs should also be considered. In the
longer term indirect economic benefits through increased fishing and wildlife associated tourism
are also likely to accrue. We envisage the program would proceed in 3 phases, namely:
Funding for Phase 1. (mapping, shellfish settlement, obtain permit approvals –$50,000)
The local community, in collaboration with Sunfish Moreton Inc., the Toorbul Fish Stocking
Association Inc., SEQ Catchments and QLD State Department of Fisheries are seeking funds to
undertake detailed hydrographic mapping of Pumicestone Passage to identify a proposed
research reef restoration site, investigate times of peak natural shellfish spat settlement and
obtain the relevant permit approvals. It is estimated this will require in the vicinity of $50,000.
A total of $50,000 is sought from the Moreton Bay Regional Council to fund phase 1.
Funding for Phase 2 (Full scale scientific R&D trials – minimum $310,000+)
Toorbul Fish Stocking Association has c. $50,000 in funds dedicated to restocking Pumicestone
Passage. They support a shellfish reef restoration project but their funds should only be used in
Phase 2 to put reef modules in the water. The remaining funds (c. 310+ K) needed for design
and proper monitoring of a full scale scientific trial will need to come from elsewhere. Other
sources of funds (Council, NRM, FRDC, Government sources) are also being investigated.
MBRC funding sought for Phase 2 (R&D): $100,000 + K
Funding for Phase 3 (Scale up to full scale estuary restoration – minimum $1 million +)
Once scientific validation of the process is completed, funding for the scaling up and broader
implementation of shellfish reef restoration in Pumicestone Passage could be done using
development offsets (based on nitrogen and carbon sequestration models), investments by
Government, as well as donations from private companies and the general public.
5
Potential Shellfish Reef Experimentation Zone, Pumicestone Passage
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Further reading:
Beck MW and 14 other co-authors (2011).
Oyster Reefs at Risk and Recommendations for Conservation,
Restoration, and Management. Bioscience 61: 107-116
Creighton C, Boon PI, Brookes JD, Sheaves M (2015). Repairing Australia’s estuaries for improved fisheries
production – what benefits, at what cost ? MarFW Res DOI 10.1071/MF14041
Diggles BK (2013). Historical epidemiology indicates water quality decline drives loss of oyster (Saccostrea
glomerata) reefs in Moreton Bay, Australia. NZ J Mar FW Res 47: 561-581.
McLeod IM, Parsons DM, Morrison MA, Van Dijken SG, Taylor RB (2013). Mussel reefs on soft sediments: a
severely reduced but important habitat for macroinvertebrates and fishes in New Zealand. MarFW Res 48:48-59.
Schulte DM, Burke RP, Lipcius RN (2009).
Science 325: 1124-1128.
Unprecedented Restoration of a Native Oyster Metapopulation.
Contact List:
Role
Oyster health, Scientific advice
Toorbul Fish Stocking Assoc. (seed
funding)
Oyster Farming
QLD Oyster Growers Assoc.
The Nature Conservancy
Sunfish
Ngunda- Joondoburri
Gubbi Gubbi
BIEPA
SC Environmental Council
Moreton Bay Eco-Alliance
SEQ Catchments
Healthy Waterways
QLD Fisheries (DEEDI)
Bribie Island Aquaculture Centre
Moreton Bay Regional Council
Pumicestone Pass. Catchment Nwk.
Noosa Council
Sunshine Coast Regional Council
University of QLD
University of Sunshine Coast
Contact name
Dr Ben Diggles
Mark Higham
Barry Evans
John Daley
Carlo Sain
Jerry Crandall
Kerry Jones
Jane Clout
Contact details
ben@digsfish.com
toorbultavern@bigpond.com,
bwmh1@bigpond.com
gd055@hotmail.com
seeker1948@hotmail.com
Dr James Fitzsimons
Boze Hancock
Bryan DeAngelis
Rob King
Jeff Ahchay
Judy Lynne
Fred Palin
Nurdon Serico
John Oxenford
Narelle McCarthy
Ian Bell
Simon Brown
Dr. Paul Maxwell
Matt Campbell
Peter Lee
Allan Sutherland
Gary Parsons
Erin Porter
Peter Armstrong
Cr Frank Pardon
Cr Joe Jurisevic
Cr Rick Baberowski
Bill Haddrill
Greg Skilliter
Ian Tibbetts
Thomas Schlacher
Neil Tindale
jfitzsimons@TNC.ORG
bhancock@TNC.ORG
bdeangelis@TNC.ORG
sunfishenvironmental@gmail.com
jahchay@live.com.au
judylynne@sunfishqld.com.au
fredpalin@live.com
nurdon.serico@tpg.com.au
biepa.mail@gmail.com, john@oxenford.net
info@scec.org.au
Dinga-bell@bigpond.com
SBrown@seqcatchments.com.au
paul.maxwell@healthywaterways.org
Matthew.Campbell@daff.qld.gov.au
Peter.Lee@daff.qld.gov.au
mayor@moretonbay.qld.gov.au
gary.parsons@moretonbay.qld.gov.au
erin.porter@moretonbay.qld.gov.au
Peter.armstrong@sunshinecoast.qld.gov.au
Frank.Pardon@noosa.qld.gov.au
Joe.Jurisevic@noosa.qld.gov.au
rick.baberowski@sunshinecoast.qld.gov.au
bill.haddrill@sunshinecoast.qld.gov.au
g.skilleter@uq.edu.au
i.tibbetts@uq.edu.au
tschlach@usc.edu.au
ntindale@usc.edu.au
kerryjones0108@gmail.com
jclout@kooringaloysters.com.au
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