Towards reconstruction of the lost reefs of Port Phillip Bay

Recreational Fishing Grants Program Research Report

Towards reconstruction of the lost shellfish reefs of Port Phillip Bay

Paul Hamer, Bob Pearce, Ross Winstanley

December 2013

Recreational Fishing Grants Program Research Report

Published by the Victorian Government, Department of Environment and Primary Industries, December, 2013 © The State of Victoria, Department of Environment and Primary Industries Melbourne 2013 This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968. Authorised by the Victorian Government, 1 Spring Street, Melbourne. Printed by DEPI Queenscliff, Victoria. Preferred way to cite this publication: Hamer, P., Pearce, B., Winstanley, R. (2013) Towards reconstruction of the lost shellfish reefs of Port Phillip Bay. Recreational Fishing Grants Program Research Report. Project SG/117. 34pp. ISBN 978-1-74326-593-2 (print) ISBN 978-1-74326-604-5 (pdf) Copies are available from the website www.depi.vic.gov.au/fishing Follow the links http://www.dpi.vic.gov.au/fisheries/about-fisheries/publications-and-resources/fisheries-reports For more information contact the DEPI Customer Service Centre 136 186 Disclaimer This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. Accessibility If you would like to receive this publication in an accessible format, such as large print or audio, please telephone 136 186, or email [email protected] Deaf, hearing impaired or speech impaired? Call us via the National Relay Service on 133 677 or visit www.relayservice.com.au This document is also available in PDF format on the internet at www.depi.vic.gov.au

Towards reconstruction of the lost shellfish reefs of Port Phillip Bay  Recreational Fishing Grants Program ii

Contents

Executive summary 1

Introduction 2

Part 1: Feasibility of shellfish reef restoration in Port Phillip Bay 8

Part 2: Potential locations for shellfish reef restoration in Port Phillip Bay 17

Part 3: Framework for developing shellfish reef restoration in Port Phillip Bay 25

Part 4: Trial project summary overview 26

Acknowledgements 28

References 29

Appendix 1 32

Towards reconstruction of the lost shellfish reefs of Port Phillip Bay  Recreational Fishing Grants Program iii

Executive summary

Recognition of the ecological role of shellfish reefs and the major declines and ongoing threats to these habitats worldwide has stimulated a number of major community/government/industry based partnership programs aimed at their protection, enhancement and restoration. Similar to coral reefs in the tropics, bivalve shellfish are the ecosystem engineers of bays and estuaries and have been defined as ‘essential fish habitat’ in the U.S.. Aside from their value as fish habitat, shellfish reefs provide other ecosystem services including nutrient cycling, water filtration, benthic – pelagic coupling, sediment stabilisation and carbon sequestration. Native flat ( angasi) and blue (Mytilus edulis planulatus) beds were once ecologically important features of significant areas of Port Phillip Bay and were recognised as important fish habitat by commercial and recreational fishers. While these two shellfish species are still common in Port Phillip Bay, they no longer occur on sediment areas in the densities or areal coverage required to be considered as ‘functional habitats’ or ‘ecosystem engineers’. Much of the loss of shellfish reef habitat in Port Phillip Bay can be attributed to dredge fishing of by the early colonists in the 19th century and more recent dredge fishing for and from the 1960s to mid 1990s (dredge fishing is no longer allowed in Port Phillip Bay). Disease, such as Bonamiasis, may have also impacted oyster populations in some areas, however, water quality and food supply, although variable, remains highly suitable for both species in the bay. One of the important impacts of fishing related declines of shellfish populations is the removal, destruction and burial of shell material that is required to provide essential substrates for settlement of larvae. This removal of shell may in part have limited the recovery of shellfish beds, even after dredge fishing was banned in 1996. There is now opportunity with the recent development of a local commercially operated hatchery supply of native flat oyster and mussel spat (small juveniles) to consider re-establishing lost shellfish beds in Port Phillip Bay. Once established, and if managed appropriately, shellfish beds can self-replenish and increase in size, to form more expansive 3-dimensionally complex and valuable bottom habitats for both fish and a variety of other marine biodiversity. There are a number of ecological, environmental, financial and logistical risks and constraints that need to be considered, and if necessary/possible, be ameliorated prior to embarking on a shellfish restoration program of any scale. This scoping report was commissioned by Fisheries Victoria in collaboration with the Albert Yachting and Angling Club to:  review the feasibility of shellfish reef restoration in Port Phillip Bay  develop a framework to guide the implementation of a shellfish reef restoration program  identify potential locations in Port Phillip Bay for shellfish reef restoration  design and cost a trial project to test likely success or otherwise of a larger-scale ongoing shellfish reef restoration program The outcomes of this scoping report, which included a workshop with experienced Port Phillip Bay recreational and commercial fishers, indicate that shellfish reef restoration is feasible and is supported by both sectors as an activity that would benefit fisheries in general and foster partnership between the two sectors to achieve a common long-term benefit. It was suggest that a trial project be developed with trial sites in the northern bay, Geelong Arm/western bay and eastern bay zones. A 3-year trial project and with costing of approximately $250, 000 is outlined.

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Introduction

Native flat oyster (Ostrea angasi) and (Mytilus edulis planulatus) beds were once ecologically important features of significant areas of Port Phillip Bay (i.e. Winstanley 1982; Nell 2001). The native flat oyster was an important part of the diet of aboriginals, as evidence by conspicuous presence of oyster shell in middens (Nell 2001). Data on mussel densities presented by Winstanley (1982) and Cohen et al., (2000) suggest a decline in abundance of mussels in north-east Port Phillip Bay of over 80% since 1980. Long-term changes in oyster abundance are less clear, however, significant decline of oyster populations in Port Phillip Bay is thought to have occurred in the 19th century due to an oyster dredge fishery in the bay (Fig. 1) and the use of oyster shells for lime production (Saville-Kent 1891; Nell 2001). In the review by Nell (2001), it is suggested that by the late 1800’s flat oyster fisheries in Victoria, and South were already fished out. The heavy fishing pressure by oyster dredgers in colonial times lead to the first Fisheries Bill – An act for the regulation of oyster fisheries in Victoria, 1858 (Fig. 2). Lynch (1966) indicates that oyster dredge fishing occurred at least up until the late 1950s early 1960’s in the Geelong Outer Harbour. Lynch (1966) states “for many years mollusc fisheries in Port Phillip were restricted to a portion of the Geelong Outer Harbour where Mud Oyster (Ostrea angasi) is dredged in the winter months. Fishermen are limited by law to a catch of 30 bushels (approximately 400 kg) of Mud Oysters in any one week” While the bay’s flat oyster population was likely to have been decimated by dredge fishing in the 1800’s, the cause(s) of the reduction in benthic mussel beds, and failure of both mussels and oysters to re-establish in large beds in the bay has been subject of debate. However, it is likely that the dredge fishery for and mussel between 1963 and 1996 had a significant impact on mussel populations and perhaps even the recovery of oyster populations in the bay. At its peak during the 1980s the dredge fishery involved up to 250,000 dredge tows per year in the bay and dredging activities were widely distributed throughout the bay (Coleman et al. 1997). Between 1979 and 1987 an average of 900 tonnes of mussels were removed from Port Phillip Bay each year, but after 1987 catches dropped to an average of less than 10 tonnes per year, mostly taken by divers, and nowadays the mussel market is entirely supplied by aquaculture (Winstanley 1982). Following the cessation of the dredge fishery for mussel and scallop in Port Phillip Bay, the North Pacific seastar (Asterias amurensis) became established. However, populations of this bivalve predator did not start to increase in a major way until the early 2000s (Parry et al. 2003). This was after the sampling program by Cohen et al. (2000) in 1998 which suggested that the major reduction of mussel abundance occurred prior to the major population growth of the North Pacific seastar, although the presence of the North Pacific seastar may now be limiting the re-establishment of significant mussel beds in the bay. Recreational and commercial fishers, particularly those targeting snapper, have long lamented the loss of shellfish beds in the bay as they were seen as providing important feeding and nursery habitats for this species. There were no studies conducted prior to the major loss of mussel or oyster beds that assessed their importance as habitat for snapper or other fish species in Port Phillip Bay, although mussels and other bivalve molluscs were indicated as important food for snapper in a study conducted in the early 1980s (Winstanley 1983), and in a more recent study conducted on samples collected between 1991 and 2000 (Restall 2001). Interestingly the occurrence of mussels in the diets of larger adult snapper was 4 to 5 times higher in the earlier study when benthic mussels were known to be more abundant in the Bay. Studies in other systems worldwide have indicated that shellfish beds provide important structural habitats for a variety of invertebrate and fish taxa (Breitburg and Miller 1998; Breitburg 1999; Coen et al. 1999; Peterson et al. 2003; Dealteris et al. 2004; Coen et al. 2011) and can provide increased protection from predators for newly settled fish (Stunz and Minello 2001) . In the U.S oyster reefs have been defined as ‘essential fish habitat’ (Coen et al. 1999). Aside from their value as fish habitat, shellfish reefs provide other ecosystem services including nutrient cycling, water filtration, benthic – pelagic coupling, sediment stabilisation and carbon sequestration (Coen et al. 2007ab; Grabowski and Peterson 2007; Coen at al. 2011; Tang et al. 2011).

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Old buried oyster shells in Corio Bay

Figure 1. Images of historic dredge fishing activities in Port Phillip Bay (top and left), and (below) old oyster shell exposed in sediments in Corio Bay

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Figure 2. Excerpt from the first fisheries act in Victoria – The Oyster Fisheries Act, 1859

A recent review of declines in oyster reef habitat has indicated the global scale of this issue, with over 90% reductions indicated for major estuaries of North America, Europe and Australia, including Port Phillip Bay (Beck et al. 2011; Diggles 2013). Loss of oyster reefs is commonly attributed to a combination of overfishing, removal of hard settlement substrate (i.e. mollusc shells, the oyster shells themselves), disease, sedimentation, pollution, and exotic species (Hargis and Haven 1999; Kirby 2004; Beck et al. 2011). The loss of oyster reefs has had major implication for water quality, biodiversity and fisheries in a number of large estuaries worldwide (e.g. Chesapeake Bay, USA, Dame 1979; Kemp et al. 2005; Coen et al. 2007ab). Recognition of the ecological role of shellfish reefs (reviewed in Coen et al. 2011) and the major declines and ongoing threats to these habitats has stimulated programs aimed at their protection, enhancement and restoration (Brumbaugh et al. 2010; Coen et al. 2011). The most prominent examples of these programs are along the east coast of North America where major partnership programs involving government, universities, private industry, conservation organisations, recreational and commercial fishing sectors, and community groups have been established with goals to increase the area of oyster reef habitat in major estuaries such

Towards reconstruction of the lost shellfish reefs of Port Phillip Bay  Recreational Fishing Grants Program 4 as Chesapeake Bay (i.e. Chesapeake Bay Oyster Foundation - http://www.youtube.com/watch?v=f- zt8lo0dgA&feature=plcpChesapeake Bay). These programs provide operational models and technical methods for restoration of shellfish habitat, and have now made significant gains in re-establishing oyster reefs (Schulte et al. 2009). Similar to coral reefs in the tropics, bivalve shellfish are the ecosystem engineers of bays and estuaries. While native flat oysters and mussels are still common in Port Phillip Bay, they no longer occur on sediment areas in the densities or areal coverage that is required for them to be considered as ‘functional habitats’ or ‘ecosystem engineers’. There is now opportunity with the recent development of a local hatchery supply of native flat oyster and mussel spat (small juveniles) to consider re-establishing lost shellfish beds in Port Phillip Bay. Once established, and if managed appropriately, shellfish beds can self-replenish and increase in size, to form more expansive 3-dimensionally complex and valuable bottom habitats. Successful restoration of shellfish beds, however, is not a simple matter of rearing young shellfish in the culture environment and then placing them at strategic locations in the wild to fend for themselves. There are a variety of ecological, environmental, financial and logistical risks and constraints that need be considered, and if necessary or possible, ameliorated prior to embarking on a restoration program of any scale. This scoping report has the primary objectives of:  reviewing the feasibility of shellfish reef restoration in Port Phillip Bay  developing a framework to guide the implementation of a shellfish reef restoration program  identify potential locations in Port Phillip Bay for shellfish reef restoration  designing and costing a trial project to test likely success or otherwise of a larger-scale ongoing shellfish reef restoration program

“Shellfish reefs provide structural habitat and increase biodiversity”

Candidate shellfish species for restoration

The two main candidate species for shell fish restoration in Port Phillip Bay are the native flat oyster (Ostrea angasi) and the blue mussel (Mytilus edulis planulatus). Below are a few useful facts about their biology:

Native flat oyster

 can grow up to 20 cm, and may live for over 20 years  reach maturity at 2-3 years age  changes sex  fertilisation of eggs occurs within the shell and the larvae are brooded within the gill chamber

Towards reconstruction of the lost shellfish reefs of Port Phillip Bay  Recreational Fishing Grants Program 5

 larvae are released (in 100,000s’) at ~180 µm and drift for several days to a week before settling on hard substrates (i.e. other shells, rocks, man-made structures etc.)  reproduction and larval brooding occurs between October to December  settlement is highest during summer (December – February)  flat oysters are vulnerable to high mortality from infection with Bonamia (a protozoan parasite), and this is more common in high density, stressed populations  growth is best in areas with stable bottom, salinities of 15 to 35 ppt, low sediment accumulation, and oxygen concentrations greater than 5 ppm  flat oysters feed by filtering phytoplankton and other particle matter from the water column  predators may include fish, starfish, crabs, , rays

Figure 3. Native flat oyster, Ostrea angasi

Blue mussel

 can grow up to 10 cm, and may live for 20+ years  reach sexual maturity by 1-2 years age at 4-5 cm length  sexes mostly separate  broadcast spawns both eggs and sperm with fertilisation occurring in open water  larvae are free swimming and can stay in the from 2 weeks to several months  the settlement stage (pediveliger) can periodically settle and re-enter the plankton if the right substrate is not found  prefer to settle on filamentous materials such as fine algae or rough textured surfaces, and can form large beds on sediments and hard substrates

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 there are no known diseases of mussel in Port Phillip Bay  they feeed by filtering phytoplankton from the water  predators may include fish, starfish, crabs, octopus, rays

Figure 4. Dense bed of blue mussels growing on sediment, Mytilus eduliis planulatus

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Part 1: Feasibility of shellfish reef restoration in Port Phillip Bay

The first step in feasibility assessment is establishing the overarching goal(s) and objectives. Any barrier to achieving the goals and objectives will need to be identified and removed for the project to be deemed feasible. Ongoing risks will need to be identified and their management or amelioration be feasible over the longer-term for the project as a whole to be considered feasible and worthwhile pursuing. The overriding goal of the shellfish reef restoration considered by this scoping review is: To increase fish habitat and food resources in Port Phillip Bay through increasing the area of native shellfish populations To achieve this goal requires the development and implementation of approaches to establish self- sustaining/renewing shellfish populations on the seabed, and overtime to achieve an increase in the area of shellfish reef habitat within Port Phillip Bay.

Technical

The key technical requirements for shellfish reef restoration include:

1. A reliable source of suitable quantities of spat or older life-stages of the particular shellfish species 2. Effective and cost-efficient methods for setting spat, transporting and out-planting of juvenile and/or more advanced shellfish stages to the wild

Production and supply of shellfish

Fortunately over the last 5 years Fisheries Victoria scientists in collaboration with the local shellfish aquaculture industry have developed culture systems and infrastructure for the production of both native flat oyster and mussel spat (Figs. 5, 6). These systems and infrastructure along with expert staff have now been transferred under a long-term lease agreement to the commercial shellfish aquaculture industry. The now commercially operated facility has capacity to supply significant quantities of native flat oyster and mussel spat, and if required, older life stages can be supplied from grow out on commercial leases in the bay (Fig. 6). The ability of the commercial industry to supply a variety of developmental stages/sizes of oysters and mussels is critical for the implementation and ongoing operation of shellfish reef restoration activities. The commercially operated hatchery and grow out facilities can supply shellfish to order, which is a significant advantage to a shellfish restoration program, both for costing and planning of experimental trials or larger scale restorations. Further, the ability of the industry to hold oysters and mussels in their grow out areas means that supply is not restricted to particular periods of the year (i.e. reproductive periods, hatchery operation cycles etc.), greatly increasing flexibility of experimental designs and restoration activities.

Feasible methods for transferring and establishing hatchery produced shellfish in the wild

There are various available approaches for establishing hatchery produced shellfish in the wild. However, there are several key technical questions that need to be considered, before deciding on a methodology: 1. What life stage will be introduced? 2. How will they be introduced? 3. Will they need to be protected from predation and physical disturbance/fishing, and if so how? These three questions are clearly not independent and answering them may require pilot experimental studies. Rather than review feasibility of all possible approaches we will consider methodology that is most feasible and best suited to the environmental and ecological setting of Port Phillip Bay, and for which there is some prior information on local species.

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The development of culture and grow out methods by scientists and industry (both local and international), along with industry experience of issues such as survival rates, growth and predation impacts provides a considerable base of knowledge to underpin development of approaches for re-establishing shellfish beds. Determining which life-stages/size to reintroduce to the natural environment will require a cost benefit analysis, informed by a trial study which considers the objectives (i.e. creating self-renewing wild adult populations), production costs, predation impacts, survival and growth across a range of size classes in the natural environment. Initial predation experiments could also be conducted in the laboratory to determine resistance of particular size classes to key predators (i.e. sea stars, fish), and preferences of key predators for particular size classes. This could inform minimum size classes for field introductions, out planting requirements to achieve success in the face of predation impacts, and or the need for predator exclusion devices. Further, such laboratory trials could indicate whether to focus restoration efforts on oysters as opposed to mussels. Either approach is feasible given the capacity of the industry to supply shellfish of various sizes, and the availability of flow through seawater aquaria facilities at DEPI, Queenscliff. Studies on success of other shellfish restoration programs, particularly along the east coast of North America, suggest that where hard substrate and associated vertical relief is lacking re-establishing shellfish reefs will be more successful if 3-dimensional hard substrates are introduced prior to or along with the shellfish introductions (Hargis and Haven 1999; Schulte et al. 2009). Other anecdotal information from local industry experts suggests that oysters in particular survive and grow better when raised off the sediments, and are possibly less prone to infestations and associated mortality from the parasitic protist Bonamia (M. Williams, pers. com.). Earlier flat oyster grow out trials in Port Phillip Bay indicated similar growth in racks one metre above the bottom and mid-water using sub-surface flotation (Reilly and Hickman 1994) suggesting that oysters don’t necessarily need to be high up in the water column to achieve acceptable growth rates. Provision of hard substrates to promote and improve rates of shellfish reef restoration have typically involved laying beds of old oyster or other mollusc shell material (termed “cultch’). Laying beds of cultch that have previously been set with cultured oyster spat is a common approach that is applied in North American programs (see Fig. 7) . Obviously a supply of shell material is essential for this approach, and this is perhaps a limiting factor in Victoria, at least in the initial stages. Recycled shell from the scallop fishery, or the growing oyster aquaculture sector may be a source of shell material future (i.e. recycled shell from restaurants or processers). However, for a trial project the most feasible hard substrates to provide a reef base or ‘core’ would be rocks, bricks or limestone blocks, cleaned recycled concrete, hebel blocks or other artificial structures such as purpose built reef modules. There are clearly a variety of options for establishing reef bases, and performance of different material types could be investigated in a trial study. Factors such as substrate complexity, surface roughness and size of cryptic spaces is likely to be important for increasing survival rates of young shellfish, particular by allowing greater refuge from predation (Hargis and Haven 1999). Earlier studies indicate that any rock or artificial substrates could be improved for oyster settlement by coating/gluing fine particles of crushed sterilised mollusc shell (preferably scallop or oyster shell) (i.e. Hickman and O’Meley 1988).

Figure 5. Industry operated shellfish and algal food culture facilities at Queenscliff.

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c)

a)

d)

e) b)

Figure 6. a) hatchery produced mussel spat, b) hatchery produced mussels grown out on ropes, c) hatchery produced native flat oyster spat, d) hatchery produced oyster spat settled on scallop shell, e) hatchery produced oysters settled on scallop shell and on grown in the bay on drop-lines.

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Figure 7. Images of oyster reef restoration activities in the eastern U.S. a) laying culttch (oyster shell) to form a reef base, b) cultch with hatchery reared oyster spat attached, c) community maintained grow out cages to get oysters to predation resistant sizes, d) large-scale cultch with spat deployment from barge, e) metal frames with small/medium size (young) oysters suspended in bags to exclude predattors, f) same as figure e) but after oysster have grown to larger size, g) and h) oysters growing on artificial reef mmodules.

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Protection of larger restoration areas from predation is logistically difficult and unlikely to be feasible in the long-term. Predation is part of the natural system in which restored reefs will exist and their long-term development will depend on the balance between natural predation rates and recruitment of new shellfish. However, protection of localised areas (i.e. cluster of adults, newly introduced seeded substrates) within a larger restoration area is likely to be feasible using mesh fences or cages. Divers could also remove sea stars from restoration areas periodically to allow newly out planted shellfish to grow beyond predation risk threshold sizes. Again trial studies are required to evaluate the impacts and ongoing risks of predation as a barrier to achieving the goals and objectives of shellfish reef restoration in Port Phillip Bay. Finally protection of restoration sites from physical damage due to shipping, dredging, commercial and recreational fishing activities (i.e. anchors) is recommended. The feasibility of longer term protection from physical damage needs to be considered in site selection to ensure choice of restoration sites does not overlap with future plans for dredging or expansion of shipping routes or anchorage zones. Consultation with commercial and recreational fishing sectors is also important to determine the codes of practice or gear restrictions to mitigate against physical damage from these activities. The legislative framework exists with the jurisdiction of Fisheries Victoria and DEPI to implement spatial closures or other restrictions via temporary Fisheries Notice to prevent undesirable physical impacts on restoration sites.

Operational

The key operation requirements include: 1. Availability of vessels both suitable and cost-effective for transport and deployment of shellfish and or substrates with attached shellfish 2. Capacity to monitor and evaluate the performance of restoration activities 3. Ongoing management/governance of a longer-term program Recent experience with artificial reef deployment in Port Phillip Bay has demonstrated the local availability of suitable vessels and skilled operators. DEPI - Fisheries Victoria staff have relevant experience for planning and overseeing deployment operations, including generation of maps and positional data to guide deployment activities. Fisheries Victoria scientists can also design, plan and oversee monitoring and evaluation programs, with potential to link these activities with Universities or recreational fishing/diving groups to reduce costs by embedding student projects or citizen science within the monitoring and evaluation program. Fisheries Victoria has suitable vessels, dive equipment, underwater still and video cameras, and can use in- house and contracted scientific divers to conduct underwater aspects of deployment and monitoring activities. During the initial development and trial phase of shellfish reef restoration it may be most efficient to place responsibility for operational management and governance within government. Fisheries Victoria has the expertise, governance and reporting structures and equipment to conduct an experimental trial phase. Further, it is likely that trial restoration areas would need to be closely managed to minimise impacts of physical disturbance by fishers (i.e. anchors, nets, fishing lines). Approvals may also be required, and this process, including development of applications, meetings and consultation etc., will be most efficient if managed by government staff with experience in this area. Fisheries Victoria also has access to suitable aquaria facilities for conducting predation trials and has close linkages with the commercial hatchery that would supply the oysters and mussels. Beyond a trial a broader partnership program could be established with its own governance and operational management framework.

Socio-economic

Costs associated with shellfish restoration activities can be attributed to six key areas:  Strategic development and consultation  Program design, including pilot/trial experiments  Planning and approvals processes

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 Purchase of live shell fish, cultch, or other materials to support shellfish reef creation  Transport and deployment  Monitoring and evaluation  Ongoing management and communication The costs of shellfish reef restoration, even with significant volunteer support, is not trivial, and funding will need to be raised to support both the establishment of a trial program (i.e. proof of concept), and the ongoing operation of a larger program. Clearly costs increase with scale and the stated objectives (i.e. target size and number of restored area etc.). Suitable funding sources need to be identified and consultation with potential funding sources should occur early (strategic development) to build support and confidence in long-term funding options. Seed money should be sought in the initial stages to fund pilot studies to demonstrate likelihood of success or otherwise of a large-scale program. Costs associated with a pilot trial phase are indicated in part 4. Generating broader community support and funding base Shellfish reef restoration has a range of benefits beyond provision of fish habitat and food sources (reviewed by Coen et al. 2011). Benefits such as increased biodiversity, ecological resilience, connectivity, and water quality will allow a broader base of community support, social license and funding options beyond traditional fisheries interests and funding sources. These should be explored through discussions with environmental management agencies, NGOs, community conservation groups, and private industry. As an example; the not-for-profit Chesapeake Bay Oyster Recovery Partnership (ORP) (http://www.oysterrecovery.org/) established nearly 20 years ago, is a cooperative coalition of multiple partners that undertakes a large-scale restoration program planting disease-free oysters back into the Chesapeake Bay (eastern U.S.A). Under the auspices of the ORP, funding has been raised and a coordinated program has planted 4 billion oysters on 1,500 acres of oyster reefs and nearly 30,000 bushels of shell have been recycled to provide substrates for new oysters. The ORP also operates a Shell Recycling Alliance, supports a community based oyster grow out program and provides shellfish aquaculture and fishery support services. While the extent and value of shellfish to Port Phillip Bay’s ecosystem and fisheries is perhaps not as significant as that of Chesapeake Bay, the ORP model provides an example of an enduring cooperative program for habitat restoration involving various sectors of the community and private industry with interests in both fishing and conservation.

Environmental and ecological

Environmental feasibility largely relates to,  suitability of substrate, and;  suitability of water quality (salinity, temperature, dissolved oxygen, turbidity/sedimentation) for shellfish to survive, grow, reproduce and expand their population size and areal coverage. Ecological feasibility relates to factors such as;  availability of food,  predation,  competition,  diseases/parasites. Native flat oysters and mussels have existed in Port Phillip Bay for thousands of years (Holgate et al. 2011) and can be found on a variety of substratum types in Port Phillip Bay, including soft sediments and hard substrates such as rocks, shell and wood. Experience in culture of Ostrea angasi however indicates that they prefer, roughed textured mineral based (i.e. shell, concrete, limestone) as opposed to organic substrates (i.e. wood, plastics) for settlement (Hickman and O’Meley 1988; M. Williams, personal communication). A key requirement for establishment and expansion of a shellfish bed is availability of suitable settlement substrates. Removal of shellfish by humans in the past, unlike natural predation or mortality, removes the shells which provide settlement substrate for new generations. For oyster or mussel reefs to grow in size and become 3-dimensional habitats they require the accumulation of shell over time (Hargis and Haven 1999). This accumulation may take many years. Further, shellfish, and oysters in particular, set, survive, reproduce

Towards reconstruction of the lost shellfish reefs of Port Phillip Bay  Recreational Fishing Grants Program 13 and grow better when elevated off the bottom as opposed to when lying flat on the sediments (Hargis and Haven 1999; Schulte et al. 2009). Therefore to expedite the creation of 3-dimensional shellfish reefs it is recommended that a base of hard substrate is established in the restoration area if it does not already exist naturally. This is highly feasible, as discussed previously. Water quality requirements and tolerances of Ostrea angasi have not been specifically tested, and are expected to vary across life-stages/sizes (i.e. Soletchnik 2007) , but as they are an estuarine species they are adapted to tolerate a range of salinity, temperature and dissolved oxygen levels. Information for other species and discussions with aquaculture scientists at Queenscliff suggest that Ostrea angasi will unlikely grow or survive well in low salinities (< 15 ppt) (Silva et al. 2011). However, such low salinity conditions do not occur in Port Phillip bottom waters. Salinity fluctuations of Port Phillip Bay bottom water, even immediately adjacent to the Yarra River mouth in Hobsons Bay typically exceed 30 ppt, and rarely drop below 5-10 ppt on the surface, even under high flow events. Port Phillip Bay is shallow and well mixed with DO levels typically greater the 80% saturation (i.e. > 5 mg/L), which is above levels that can lead to oyster mortality or impacts on feeding and growth (i.e. <4 mg/L is undesirable, Vaquer-Sunyer and Duarte 2008). While the Bay’s physico-chemical water quality (temperature, salinity, dissolved oxygen) is not considered a major risk to oyster or mussel survival, high sediment loads and siltation that could smother or bury shellfish and their essential settlement substrates could have a significant impact on natural recruitment and survival rates and therefore the success/natural expansion of restoration area. Typical suspended sediment loads in Port Phillip Bay, and even in the Hobsons Bay adjacent to the Yarra mouth are below 100 mg/L (You et al. 1997). These higher suspended solid levels in some areas of Port Phillip Bay are unlikely to kill oysters and mussels, but may have sub-lethal affects (i.e. impacts on growth, condition, reproduction) (Loosanoff 1961; Grant et al. 1990). Suspended sediment loads in most areas of Port Phillip Bay may not present a major risk to shellfish survival, but the impacts of siltation and burial is uncertain. It has been suggested that flat oysters living on the sea bed could be at significant risk from siltation (Yonge 1960; Moore 1977; Lenihan and Peterson 1998). Raising of newly established shellfish from the sea bed will ameliorate the risks from storm events or other episodic high sediment loads and siltation that could lead to smothering or burial. This would be particularly important in areas of low currents where storm induced sedimentation will not be readily flushed away. Finally, it is clearly not advised to attempt shellfish reef creation in areas subject the high sediment loads from dumping of dredge spoil. The specific food requirements for different life-stages of oysters and mussels to survive, grow and successfully reproduce in the wild have not been determined locally, and are indeed difficult to specify since food supply and feeding in the wild is influenced by both algal concentration and currents (Pogoda et al. 2011). However, it is suggested that Chlorophyll a (Chl a) concentrations between 1 and 55 µg/L are recommended for pacific oysters ( gigas) (i.e. Silva et al. 2011 and references therein), and trials in offshore environments demonstrated high survival and satisfactory growth of (closely related to Ostrea angasi) at Chl a concentrations between 3 and 28 µg/L (Pogoda et al. 2011). Recent Chl a measurements in Port Phillip Bay, across a range of locations and times typically range between <1 to 20 µg/L (Longmore 2012) . Higher Chl a typically occurs in the north and east of Port Phillip Bay due to the nutrient inputs from the Yarra River and a clockwise transport of the Yarra River plume along the northern and eastern shoreline in to the Carrum Bight region (Fig. 8).

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Figure 8. Aerial view of Port Phillip Bay, showing the clockwise transport of the Yarra River plume after a major flow event.

Predation One the biggest risks in relation to feasibility of shellfish reef restoration in Port Phillip Bay is predation. Two species, in particular, the native 11 arm sea star Coscinaterias muricata and the exottic North Pacific seastar Asterias amurensis, are voracious bivalve predators. Both species are known to predate on mussels of all sizes, but their relative abilities to predate on larger adult flat oysters, or their selectivity for different sizes is unclear. Other fish and crustacean predators such as crabs, octopus, leather jacket, globe fish and snapper, may also impact on the survival of shell fish, particularly the smaller size classes. Predator exclusion through use of cages or specific methods for out planting is feasible, and may be essential forr protecting newly planted shellfish for a period of time. Irrespective of what methods for out planting are used, understanding of susceptibility to predation and potential predation rates will be important to developing estimates of numbers and sizes of shell fish required to be out planted to establish and maintain populationns against predators. This is obviously important for assessing feasibillity and cost/benefit of a larger program. Again experimental trials are recommended to inform these estimates. Disease Another risk to shellfish reef restoration successs is disease. For native flat oyster in Port Phillip Bay the greatest risk is due to Bonamiasis. Bonamiasis results from infection with the protozoan Bonamia (currently the Bonamia species in Port Phillip Bay is not known). Infections are most problematiic for sexually mature oysters and can result in high mortality rates of oysters over 2-3 year age. Fortunatelyy, Bonamia does not have any known human health implications. To date, no notifiable diseases have been identiffied in Australian blue mussels. Therreefore unlike oysters, disease outbreaks and associated mortality is not considered a major risk for mussel reef restoration. While the risk of Bonamiasis related mortalities cannot be totally removed, it is thoughht that Bonamiasis is more prevalent in high density beds on the bottom and that stress is a critical factor in Bonamiasis outbreaks (Hickman et al. 2000). Therefore the risk of Bonamiasis can potentially be reduced by keeping the newly establish oysters off the bottom (lower stress froom sedimentation and improved filterinng/feeding), and only re-

Towards reconstruction of the lost shellfish reefs of Port Phillip Bay  Recreational Fishing Grants Program 15 establishing at moderate initial densities. Ongoing monitoring of newly establish beds is important to identify if outbreaks occur, which may be a barrier to further out planting. Oyster brood stock introduced to the Queenscliff hatchery are sourced from Bonamia free farms in Port Phillip Bay and there is a strict testing protocol to ensure that this occurs (M. Williams, personal communication). Therefore there is low risk of introducing hatchery reared Bonamia infected oysters to the out planting/restoration sites. However, if translocation of adult brood stock from wild beds to the enhancement area was to occur it would be important to follow similar testing protocols to ensure Bonamia free oysters are translocated (see below). Ultimately we still know very little about the factors that trigger outbreaks of Bonamiasis, individual susceptibility and transmission, and this limits our ability to develop mitigation approaches. Much more work is required to understand, test and develop approaches to mitigate the impacts of Bonamiasis. Carefully design restoration experiments could contribute to increasing knowledge in this area.

Management and approval processes

The act of out planting of hatchery produced shellfish and associated hard substrates to unreserved sea bed in Port Phillip Bay (i.e. Crown land) would likely be subject to approval under the Coastal Management Act and the Fisheries Act. The approvals under both these acts would have their own requirements in terms of risk assessment, monitoring and reporting. The fact that man-made artificial reefs structures have recently been deployed in Port Phillip Bay under Coastal Management Act consent would indicate that approval for shellfish reef creation and enhancement is feasible. Further, a ‘works on water permit’ would be required from Parks Victoria for deployment operations in Port Phillip Bay. It would be important that any restored or enhanced shell fish areas were protected from removal of the shellfish. Ongoing management of the enhanced or restored areas could involve a range of legislative instruments under the Fisheries Act to mitigate against removal of the shellfish by commercial or amateur fishers. Translocations of wild oysters among areas within Port Phillip Bay would carry the risk of introducing Bonamia infected oysters to uninfected areas. It is thought that flat oysters in some areas of Port Phillip Bay are more prone to outbreaks of Bonamiasis than others (A. Clarke, personal communication). However, the spatial patterns of Bonamia prevalence in the bay or the local environmental conditions that are conducive to outbreaks of Bonamiasis are poorly understood and clearly require further studies. In relation to rehabilitation of oyster beds in the bay it would currently not be advisable to translocate wild brood stock among different regions. Introductions of new brood stock to an area should only come from known uninfected sources.

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Part 2: Potential locations for shellfish reef restoration in Port Phillip Bay

Choice of locations for shellfish reef restoration can be informed by knowledge of areas of historic and/or current occurrence, as these locations likely have important ecological and environmental attributes conducive to shellfish populations. However, where major losses have occurred to historic shellfish beds it is important to have some knowledge of why these losses may have occurred and whether or not the issue(s) responsible for shellfish losses are still occurring or likely to re-occur in the future. To obtain some historical and present context on the occurrence and locations of major shellfish beds in Port Phillip Bay we reviewed literature and conducted a workshop with invited guests from the commercial and recreational fishing sectors and the aquaculture industry.

Information derived from literature

Native flat oyster

There is limited historical documentation on the distribution and abundance of Ostrea angasi in Port Phillip Bay. Historical records have, however, suggested that oysters were important in colonial times. Native flat oyster apparently occurred in large natural beds prior to European settlements, particularly in the Geelong Arm, but declined markedly soon after settlement, likely due to overfishing and possibly also disease (Hickman et al. 2000). Fisheries Victoria researchers working on oyster culture in the late 1980’s reported dense oyster beds at Point Henry and Arthur the Great region of the Geelong Arm/ Geelong Outer Harbour (Hickman et al. 2000). These areas were used for brood stock collections, but heavy mortalities were recorded in these areas in 1991, thought to be the result of an outbreak of Bonamiasis (Hickman et al. 2000). Abundant oyster shell and lime kilns in the Geelong area suggest that oysters beds were once a major feature of the Geelong Arm and Corio Bay. Figure 1 shows evidence of old oyster shells buried under soft sediment in Corio Bay, and large banks of old oyster shell occur off Pt Henry (P. Hamer, personal observation). The shallow waters in this region would have been highly suited to the early sail powered dredge fishery. Surveys of benthic molluscs in the early 1960’s by Macpherson (1966) and in the early 1970’s by Poore and Rainer (1974) indicated that native flat oysters were very widespread through the bay (Fig. 9), although the actual numerical data specific to the species was not presented. Similary, Hamer et al. (1996) used underwater video quadrat sampling to quantify abundance of sessile invertebrates on sediments (primarily sea squirts, flat oysters, mussels and the European fan worm), and while data specific to oysters was not presented the highest abundances of sessile invertebrates were recorded in the northern region of the bay. The study by Cohen et al. (2000) provides a more comprehensive data set on oyster abundance and distribution across 30 sampling station in the bay sampled by diver deployed sled in 1998. In this study native flat oysters were also widespread throughout the bay, but interestingly were not recorded from the two stations in the Geelong Arm (Fig. 10). The highest biomass of native flat oyster was recorded in the north eastern and central regions of the bay, consistent with the earlier studies. On the shallower coarse sandy areas they reported on average 5 oyster per 100 m2 , on the intermediate depth sands, 10 oyster per 100 m2 and on the deeper mud substrate in the central bay, 38 oysters per 100 m2 (Fig. 10).

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‐2 g m

Figure 9. Map showing distribution and relative biomass of epifaunal invertebrates sampled by grab sampler (dominated by blue mussel and native flat oyster) in Port Phillip Bay in 1970 - 71 (from Poore and Rainer 1974).

‐2 Number/biomass 100 m

Figure 10. Map showing distribution and relative numbers and biomass of native flat oyster sampled by divers in Port Phillip Bay in 1998 (from Cohen et al. 2000).

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Blue mussel

Dredge surveys of blue mussels in Port Phillip Bay were conducted by Winstanley (1982) in the early 1980’s and provide a valuable indication of blue mussel abundance and distribution at this time (Figs. 11 ab). The surveys by Winstanley showed dense beds of mussels on soft-sediments in eastern Port Phillip Bay in 1980 (i.e Carrum Bight area), but a reduction in abundance and contraction of distribution between surveys in 1980 and 1981. These survey data can be compared to data collected by the dive surveys in 1998 (Cohen et al. 2000). In 1998 highest blue mussel densities were recorded in the north of the bay (Hobsons Bay area), where densities of 196 mussels per 100 m2 were recorded on sandy substrate (Fig. 12) (Cohen et al. 2000). The survey by Winstanley in 1980 indicated densities of over 2000 mussels per 5 min dredge tow (i.e. over 135 per 100 m2) off Carrum in the eastern part of the bay (Fig 11 a). In 1980, Winstanley (1982) recorded densities of over 480 mussels per 100 m2 at a region in the entrance to the Geelong Arm (Fig. 11 a). While the density of mussels reported by Winstanley (1982) in eastern Port Phillip Bay is comparable to the densities reported by Cohen et al. (2000) for northern Port Phillip Bay in 1998, Cohen et al. (2000) indicated that densities in eastern Port Phillip Bay in 1998 were generally less than 20 per 100 m2 (85% less than 1980 records by Winstanley) (Fig. 12). Finally, Winstanley (1982) also indicated a significant decline between 1980 and 1981, indicating that mussel densities can change rapidly, although it is unclear the role of fishing versus environment factors in causing this rapid decline, which was general across the bay (Fig. 11 ab). Clearly high density mussel beds have occurred in northern and eastern Port Phillip Bay in the past.

a) ‐2 b) ‐2 Number 1480 m Number 1480 m

Figure 11. Distribution and abundance of blue mussels in Port Phillip Bay surveyed by dredge in; a) 1980, and b) 1981. Data are presented as numbers of mussels per dredge haul, and a dredge haul covered was approximately 1480 m-2 (from Winstanley 1982).

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‐2 Number/biomass 100 m

Figure 12. Distribution and abundance of blue mussels surveyed by diver transects in Port Phillip Bay in 1998. The number or biomass are per 100 m2, transects were 100 m long x 1m wide (from Cohen et al. 2000).

Information derived from workshop

A half day workshop was conducted at the Albert Park Yachting and Angling Club on 12 November 2012 (appendix 1). The workshop was attended by long-time experienced recreational and commercial fishers, scientists and fisheries managers, and was chaired by Mr Ross Winstanley, who had conducted earlier work on the bay’s shellfish populations during the 1980’s. The immediate objective for the workshop was to identify suitable locations in Hobsons Bay, and other regions of the bay for a trial study to demonstrate the feasibility of restoring natural shellfish based ecosystems. The workshop began with an overview of shellfish reef restoration, and then discussions of the current and historical occurrence of significant flat oyster and mussel beds in Port Phillip Bay. The bay was divided into four zones (Fig. 13) and large maps of the four zones were provided to the participants who were each provided opportunity to impart their knowledge on shellfish beds in the bay and mark key areas on the maps. The information provided by the participants was collated and used to create maps, shown in figure 14-16, of anecdotal areas of high shellfish abundance to further inform choice of locations to conduct a trial restoration project. A total of 21 areas of historic shellfish beds were identified across the Geelong Arm/western Bay, Northern bay, and Central eastern bay zones (Figs. 14-16), however, no major areas were suggested for the southern bay zone (hence no figure for this zone included), although scallops are abundant in this zone. Participants in the workshop made particular reference to:  areas in 7-10 m in the north of the bay, off Altona, Williamstown, Princess Pier, St Kilda, Hampton and Sandringham that used to have mixed beds of mussel and oyster

Towards reconstruction of the lost shellfish reefs of Port Phillip Bay  Recreational Fishing Grants Program 20

 a broad area from Beaumaris to Frankston in about 10 -12 m depth that used to have dense mussel beds  historic oyster beds and abundance of old oyster shell in sediments the Geelong Arm, ie. off Pt Henry  mussel beds in shallow waters around the north western shore of Corio Bay, Pt Lillias and Pt Wilson in the Geeelong Arm (see Fig. 14).

Figure 13. MMap of Port Phillip Bay with bathymetry and marine navigation chart overllay showing the four major zones that were used to identify anecdotaal areas of historic high shellfish abundance.

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Figure 14. MMap of the Geelong Arm showing areas of anecdotal/historic mussel and oyster beds (circled areas, see table below). Area 4 circled red is suggested as a possible area for trial restorations of shellfish beds.

1 Areas of old oyster shell buried in mud around western Corio Bay 2 Mussel beds on sediment 3 Mussel beds on inshore reefs 4 Historic oyster beds with mussels on sediment (priority restoration area) 5 Mixed oysters and mussels 6 Mussel beds

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Figure 15. MMap of northern Port Phillip Bay showing areas of anecdotal/hhistoric mussel and oyster beds (circled areas, see table below). Areas circled red are possible areas for trial restorattion of shellfish beds.

7 Mussels on reef 8 Mussel of reef 9 Area of old shell 10 Mussels on reef 11 Mussels on reef 12 Oysters (two areas), oysters still present 13 Oysters and mussel on sediment 14 Oyster and mussels on sediment 15 Oyster and mussels on reef 16 Oyster and mussels on reef/rubble 17 Large areas of mussel beds and patches of oysters on sediments 18 Oyster and mussels on reef

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Figure 16. MMap of central and eastern Port Phillip Bay showing areas of anecdotal/hiistoric mussel and oyster beds (circled areas, see table below). Areas circled red are possible areas for trial restoration of shellfish beds.

19 Large areas of mussel beds on sediments 20 Large areas of mussel beds on sediments 21 Area of patchy oysters

There was broad consensus among the workshop participants about the historic existence on large areas of mussel beds in Port Phillip Bay, particularly in thhe northern and eastern regions and tthat these areas coincided with productive fishing grounds (Figs. 15, 16). The fisher knowledge on historic mussel areas is consistent with the scientific surveys by Winstannley in 1980 and 81 (Fig. 11). There was less fisher knowledge of historic oyster beds, but observations of oysters on the deeper muds annd areas of old oyster shell in the Geelong Arm are consistent with historical information on occurrence of oysters in the bay (particularly the major loss from the Geelong Arm) and more recent survey work by Cohen et al. (2001) (Fig. 10). One participant in the workshop made the interesting observation of significant amounts of oyster shell in the old St Kilda tip site while fossicking for old bottles. Other comments that suppoort historic high abundance of mussels, in particular, growing on the sediments of the northern bay region were that after strong south-westerly blows large quantities of live mussel clumps would be washed up the St Kilda –Port Melbourne shoreline (i.e. 1960s-70s). The workshop participants (recreational and commercial fishers) were supportive of tthe concept of restoring shell fish reef habitats in Port Phillip Bay as an activity that would benefit fisheries in ggeneral and foster partnership between the two sectors to achieve a common long-term benefit. It was suggest that a trial project be developed with trial sites in the northern bay, Geelong Arm/western bay, and eastern bay zones.

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Part 3: Framework for developing shellfish reef restoration in Port Phillip Bay

Figure 17. outlines a conceptual framework for developing a shell fish restoration program in Port Phillip Bay. It describess an adaptive phased approach starting from establishing the case for resttoration through to conducting smaller scale trials to infoorm the development of technical systems and appproaches, and identify risks, with ‘stop go’ stages to ensure that transition to a large-scale program occurs only if it is well founded and highly likely to achieve success in meeting goals and objectives and provide appropriate value to beneficiaries for the investment. This report sits at the stop-go stage 3 in that it has investigated the case for shellfish reef restoration in Port Phillip Bay, stakeholder support and beneficiaries, and assessed the feasibility. The next stage in the process involves developing/refining the technicaal aspects and then demonstrating the success of shellfish reef restoration at a medium scale (i.e. acre to hectare scale areas). These next stagges require funding to occur. Funding sources will need to be identified and engaged to progress beyond thhis feasibility study. Part 4 below provides an example of what an experimental medium-scale trial project migght look like, along with cost estimattes and likely time-lines.

Figure 17. FFramework for developing a shell fish restoration program in Port Phillip Bay

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Part 4: Trial project summary overview

Figure 18. Overview of a trial project of shellfish reef restoration in Port Phillip Bay.

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Figure 18. Aerial view of Port Phillip Bay showing approximate areas recommended for trial shellfish reef restoration in western, northern and eastern Port Phillip Bay.

A trial project is recommended to establish the systems and approaches for a guiding a cost-effective refined longer-term restoration program. The trial would begin with ‘on-land’ testing of predattion resistance of oysters, (we are already aware that mussels of all stages are vulnerable to predators) at different sizes/stages of development, focusing on seastars (Native 11 arm, Coscinsaterias muricata, and North Pacific Asterias amurensis) and several common fish species (i.e. snapper Pagrus auuratus, leather jacket Meuschenia species, and globe fish Diodon nicthemerus). Depending on resources available, predation by octopus and crabs could also be tested. This will allow potential predation losses to be incorporated into planning of the field deployment phase of the trial. The other ‘on-land’ component of tthe trail would involve establishing the design and testing of oyster settlement modules. Modules may needd to have certain surface characteristics (i.e. roughness, cryptic spaces) to support high settlement success and post-settlement survival rates. Further, settlement/survival rates per surface area of module are impoortant to know for planning larval production requirements and module sizes/numbers for field trials. Thhe ‘on-land’ components would occur in the first year of a trial, during spring and summer. Once the ‘oon-land’ components are completed, ‘stage 2 – field trials’ can be conducted in an informed manner. The second year ‘winter’ of a 3 years trrial project would allow time to produce the required modules, predation exclusion devices, survey and prepare field sites, and plan hatchery operattions and deployment schedules. Modules would be settled with oysters during spring/summer and deployed in mid/late summer, along with mussels purchased directly from mussel farms. Monitoring of trial sites forr abundance and growth of the deployed shellfish would occur within one month of initial deployment and then every 4 months post- deployment for approximately two years. The 3 year ttrial program, involving three trial areas of approximately ¼ acre area in Port Phillip Bay (Fig. 18), out planting of 2-3 million oysters and 10,000 mussels, along with follow up monitoring and evaluation would be expected to cost approximately $250,000 (see Fig. 18).

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Acknowledgements

This project was funded by the Victorian Government using Recreational Fishing Licence fees. We would like to acknowledge the Recreational Fishing Licence Fees and Fisheries Victoria for providing funding to support the workshop and production of this scoping report. We would also like to thank the Albert Park Yachting and Angling Club for supporting the workshop and their ongoing involvement and passion for promoting habitat restoration in Port Phillip Bay. John Mercer, Andrew Clarke and Mike Williams provided valuable advice on oyster and mussel history in Port Phillip Bay, biology and aquaculture production.

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Appendix 1

Agenda of the workshop on potential of shellfish reef rrestoration in Port Phillip Bay held at Albert Park Yachting and Angling Club on 12 November 2012.

Towards reconstruction of the lost shellfish reefs of Port Phillip Bay  Recreational Fishing Grants Program 32

Work shop attendees

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