Content uploaded by Simon Branigan
Author content
All content in this area was uploaded by Simon Branigan on Sep 29, 2019
Content may be subject to copyright.
A preview of the PDF is not available
Restoration Guidelines for Shellfish Reefs
Abstract and Figures
This guide is for practitioners, managers and community members to provide both guidance in decision-making for establishing shellfish reef restoration projects and examples of different approaches undertaken by experienced practitioners in a variety of geographic, environmental and social settings.
The guide both updates and expands on the original Practitioners Guide (Brumbaugh et al.), capitalising on the improvements in knowledge around the ecological function of bivalves in their coastal environments as well as on the depth and breadth of experience that now exists globally.
The restoration approach is aligned to the Society for Ecological Restoration's International standards for the practice of ecological restoration and was developed by a global team of writers and editors.
Figures - uploaded by Simon Branigan
Author content
All figure content in this area was uploaded by Simon Branigan
Content may be subject to copyright.
... Moreover, restoration efforts often exist within dynamic, crowded seascapes, so stakeholder engagement, sitespecific logistics and local feasibility are also key in determining the suitability of a site for native oyster restoration. Although such factors have typically been tackled within ongoing project management (Schuster & Doerr, 2015;Fitzsimons et al., 2019), gauging stakeholder opinion and logistical challenges are critical from early on in site selection. Indeed, recent site selection activities in western Australia also include such factors in their site selection processes (Cook et al., 2022). ...
... Site selection for native oyster habitat restoration projects has been identified as a priority research area (Pogoda et al., 2020a;zu Ermgassen et al., 2020a). While there are many examples of site selection for native oyster habitat restoration across a range of spatial scales, and existing guidelines provide broad themes for consideration (Fitzsimons et al., 2019;Preston et al., 2020a), a comprehensive overview of the many considerations which should be accounted for in site selection is currently lacking. To support more efficient and successful restoration practices, this study uses the Delphi process to draw upon pan-European expertise to identify the most important factors in site selection for European native oyster habitat restoration projects. ...
... The listed factors were proposed based not only on the experts' experience with site selection processes to date, but also incorporating their experience of managing projects, and their understanding of facilitating factors in project success. The resulting list of factors therefore provides a comprehensive overview of not only the key abiotic factors which may be included in habitat suitability modelling, but also factors relating to project logistics (Figure 3b), biotic (Figure 3d) and socio-economic factors (Figure 3e), which are critical in project planning and execution(Fitzsimons et al., 2019;Preston et al., 2020a). The listed 'Essential' socioeconomic factors, such as stakeholder interest and support(Figure 4), underpin project acceptance and can be pivotal in acquiring funding, project approval and/or social licence to operate(Imeson & van den Bergh, 2006;Deitch et al., 2021;Lupp et al., 2021). ...
The European native oyster ( Ostrea edulis ) is a threatened keystone species which historically created extensive, physically complex, biogenic habitats throughout European seas.
Overfishing and direct habitat destruction, subsequently compounded by pollution, invasive species, disease, predation and climate change have resulted in the functional extinction of native oyster habitat across much of its former range.
Although oyster reef habitat remains imperilled, active restoration efforts are rapidly gaining momentum. Identifying appropriate sites for habitat restoration is an essential first step in long‐term project success.
In this study, a three‐round Delphi process was conducted to determine the most important factors to consider in site selection for European native oyster habitat restoration projects.
Consensus was reached on a total of 65 factors as being important to consider in site selection for European native oyster habitat restoration projects. In addition to the abiotic factors typically included in habitat suitability models, socio‐economic and logistical factors were found to be important. Determining the temporal and spatial variability of threats to native oyster habitat restoration and understanding the biotic factors present at a proposed restoration site also influence the potential for project scale‐up and longevity.
This list guides site selection by identifying: a shortlist of measurable factors which should be considered; the relevant data to collect; topics for discussion in participatory mapping processes; information of interest from the existing body of local ecological knowledge; and factors underpinning supportive and facilitating regulatory frameworks.
... Tropical marine systems generally harbour greater biodiversity than temperate systems (Gray, 1997;Roberts et al., 2002) and this also holds true for oysters where the diversity of species is higher in the tropics (Guo et al., 2018). Despite this, tropical oysters remain underrepresented in global reviews and oyster reef restoration manuals (Beck et al., 2011;Fitzsimons et al., 2019;Fitzsimons et al., 2020;Zu Ermgassen et al., 2020). ...
... To assess the global diversity of reef-building oysters, we compiled a list of oyster genera known to contain reef-building species from reef restoration reviews and reports (Alleway et al., 2015;Fitzsimons et al., 2019;Pogoda et al., 2019;Zu Ermgassen et al., 2020). From this search five genera were identified: Crassostrea, Isognomon, Ostrea, Pinctada and Saccostrea. ...
... Reported extant remnant reef information including location, reef area, oyster density, abundance, and biomass has been recorded in Table 1 (see Supplementary Material for references), however these systems are likely degraded and therefore may not represent healthy, historic numbers. The identifi cation and characterisation of reference systems (remnant reefs with minimal degradation and healthy populations of oysters) are important for setting and monitoring restoration targets (Fitzsimons et al., 2019), and this represents a large knowledge gap for tropical oyster reefs. ...
Oysters are ecosystem engineers that form biogenic reef habitats in shallow coastal and estuarine waters and provide important ecosystem services. Widespread global declines have triggered a world-wide restoration movement, however a paucity of information on tropical oyster reefs has resulted in their exclusion from existing global assessments and, consequently, restoration. In this review we quantified the known global diversity of native reef-building oysters to compare diversity between temperate and tropical regions and assessed historic oyster reef presence and declines using two tropical case studies. We then summarised the biology, ecology, and benefits of tropical oyster reefs, which have four functional differences to temperate reefs: 1) the diversity of reef-building oysters is over four times higher in tropical than in temperate regions; 2) tropical reef-building oysters can have continuous spatfall throughout the year whereas temperate species have a defined season; 3) tropical reef-building oysters are generally faster growing than temperate reef-building oysters; and 4) tropical oysters commonly create mixed-species oyster reefs whereas temperate oyster reefs are generally formed by a single oyster species. There is evidence of unsustainable and destructive harvesting that has resulted in the decline of tropical oyster reefs, and these reefs should therefore be included in restoration efforts. We highlight knowledge gaps that can guide future research to develop important foundational information that will remove barriers to tropical oyster reef restoration.
... Obtaining permission to access a site or areas within a site may be an additional legal constraint set by the property owner. Funding is frequently cited as a major constraint for REMA plans, limiting the scope, frequency, and duration of restoration monitoring Fitzsimons et al. 2019) and constraining expectations for detecting whether anticipated benefits were generated within the duration of the REMA program (Fitzsimons et al. 2019). The setting and size of the site (e.g., site constraints) can limit what rehabilitation can be achieved due to isolation from sources of colonizing biota or other natural resources (e.g., water, light, sediment, nutrients), the establishment of fully functional ecological communities due to small size of a site, or the influx of contaminants or noxious species from surrounding properties (Shreffler and Thom 1993;Rice et al. 2005;. ...
... Obtaining permission to access a site or areas within a site may be an additional legal constraint set by the property owner. Funding is frequently cited as a major constraint for REMA plans, limiting the scope, frequency, and duration of restoration monitoring Fitzsimons et al. 2019) and constraining expectations for detecting whether anticipated benefits were generated within the duration of the REMA program (Fitzsimons et al. 2019). The setting and size of the site (e.g., site constraints) can limit what rehabilitation can be achieved due to isolation from sources of colonizing biota or other natural resources (e.g., water, light, sediment, nutrients), the establishment of fully functional ecological communities due to small size of a site, or the influx of contaminants or noxious species from surrounding properties (Shreffler and Thom 1993;Rice et al. 2005;. ...
The purpose of this report is to demonstrate that incorporating ecosystem services (ES) in restoration effectiveness monitoring and assessment (REMA) is feasible, practical, and provides strategic value that can enhance the success of restoration projects. Ecosystem restoration is pursued for a variety of reasons, typically to improve the condition of the ecological structure and/or function of a parcel of land. Philosophically, it may be argued that the ultimate reason for restoration is to increase the flow of benefits from nature to people who use or care about that parcel. Although the explicit inclusion of ES as part of a restoration project’s goals has been recommended in several influential restoration guides, relatively few restoration projects have done so. Possible reasons for the slow adoption of ES in restoration include perceptions that measuring them is difficult, costly, requires special expertise, that goals to improve ES for people are contrary to goals to improve nature for its own sake, and/or the lack of guidance on how to identify, quantify, or assess ES. Those challenges are met directly with this report which provides general approaches for identifying and prioritizing ES, particularly via stakeholder engagement, for transforming those into project goals and monitoring metrics, for using ES to assess restoration effectiveness, and to communicate progress toward restoration goals in terms that resonate with different audiences (i.e., communities, landowners, tribes, agencies, regulators, and other stakeholders). Additionally, this report provides in-depth consideration for incorporating ES into three restoration communities of practice (CoP): conservation based-restoration, contaminated site cleanup based restoration (where terminology used includes remediation and revitalization), and compensatory
mitigation-based restoration. The audience for this report includes restoration/remediation/revitalization practitioners, project or program managers, stakeholders (including nearby communities), regulators, and research scientists.
... While oyster reef restoration is relatively new in Australia (Gillies et al. 2018), reestablishment of lost oyster reefs and their ecosystem services have been successfully implemented elsewhere over the last four decades (Fitzsimons et al. 2019). Oyster reef restoration on the east coast of the United States has often been implemented at large scales using industrial techniques, however, there have also been many small-scale citizen science initiatives. ...
Oyster gardening is a community‐driven activity where oysters are grown in cages hanging off docks or other coastal infrastructure. Besides the provision of adult oysters for restoration programmes, oyster gardening may also support other ecosystem services such as providing habitat for fishes and invertebrates as well as encouraging community involvement and citizen science. Australia's first oyster gardening programme was undertaken in a canal estate on Bribie Island in Moreton Bay, Queensland between October 2016 and November 2017. Oyster gardens consisting of plastic mesh cages were deployed with either three species of bivalves (polyculture), or exclusively Sydney Rock Oysters (monoculture) to investigate whether the habitat value differed between the two garden types. After one year of growth, polyculture cages supported higher abundances and species richness of both invertebrates and fish compared to the monoculture gardens. Our study showed that oyster gardening can provide habitat for a range of invertebrate and fish species in the highly modified coastal environment of a canal estate. Further studies are needed to discern whether these oyster gardens would also support larger and mobile fauna, such as species with commercial and recreational importance.
... Oyster reefs are three-dimensional habitats for diverse species assemblages that stabilize shorelines, improve water quality, and promote denitrification (Grabowski et al., 2012;Newell, 2004;Wells, 1961). To conserve these ecological functions and rebuild this important economic fishery, large-scale restoration projects have been increasing in recent decades Fitzsimons et al., 2019). In the Gulf of Mexico, major oyster reef restoration efforts have taken place during the 21st century (Bersoza Hern andez et al., 2018), but the region has also experienced major oyster die-offs due to several freshwater diversion events (Gledhill et al., 2020;Grabowski et al., 2017). ...
Global changes in precipitation patterns have increased the frequency and duration of flooding events. Freshwater inflows into estuaries reduce salinity levels and increase nutrient inputs, which can lead to eutrophication and impaired water quality. Oysters are important ecosystem engineers in coastal environments that are vulnerable to co‐occurring environmental stressors associated with freshwater flooding events. Successful recruitment is necessary to maintain adult oyster populations, but early life stage responses to multiple stressors are not well understood. Flood‐associated stressor conditions were observed near oyster habitats at multiple locations across the northern Gulf of Mexico during peak recruitment months in the spring and summer of 2021. In the laboratory, we examined the interactive effects of acidification, hypoxia, and low salinity on larval and juvenile life stages of the eastern oyster (Crassostrea virginica) to better understand the impact of flooding events on oyster development and survival. Salinity stress in isolation reduced larval growth and settlement, and decreased survival and growth at the juvenile stage. Hypoxia was more stressful to oyster larvae than to juveniles, whereas low pH had negative effects on juvenile growth. There were no synergistic effects of multiple flood‐associated stressors on early oyster life stages and effects were either additive or predicted by the salinity stress response. The negative impacts of flooding disturbances on recruitment processes in benthic populations need to be considered in restoration planning and flood control mitigation strategies as the frequency and intensity of extreme freshwater events continue to rise worldwide.
... They also support rich algal and microphytobenthic communities, providing food for grazers that live within the reef [6]. By better understanding the ecological interactions that occur between species and their spatial variation, we can better appreciate and value them for their contribution to nature alone [49]. Studies have shown that bivalves, in particular oysters, are capable of increasing species abundance and richness, as well as overall biomass [35,50]. ...
Native oyster ( Ostrea edulis ) habitat has been decimated across the majority of its natural range as a result of human activity. In recent decades, oyster restoration projects have gathered increasing support due to their potential to provide ecosystem services that offset increasing pressure from human development, resource demand, and also climate change. These ecosystem services are reviewed here, so as to inform the potential benefit of restoration projects. Ecosystem services can be divided into four categories: provisioning services through direct utilisation of oysters and the species they support, regulating services that help maintain a healthy environment, habitat services that benefit biodiversity, and cultural services that can influence tourism and wider cultural values. Ecosystem services are often interlinked in complex networks, though these can be linked back to two overarching ecosystem functions, stemming from either the filter feeding activity of oysters, or the physical reef structure that they provide. The MARINEFF oyster enhancement reefs installed in the Solent, September 2020, are intended to support the extensive Solent Oyster Restoration Project initiated by the Blue Marine Foundation. The expectation is that they will facilitate both oyster settlement and the release of larvae for the repopulation of the Solent system. This may contribute to the recovery of ecosystem services mentioned in this review. It is important to note however that there is a lack of baseline data for native oysters, and the ecosystem service values they provide are poorly constrained, meaning that ecosystem service estimates are derived largely from other species of oyster. This inhibits our ability to accurately calculate and model natural capital provided by native oysters, highlighting the necessity for further research so as to inform management and restoration targets.
This document has been prepared in cooperation with Federal, Indigenous, and State malacologists (mollusk scientists), environmental toxicologists, restoration specialists, and other subject matter experts to provide best practices for freshwater mussel injury determination, early identification of restoration
opportunities, injury quantification and damages determination (also referred to as claim development), and restoration planning, implementation, and monitoring. The experts address the effects of hazardous substance releases and oil spills on freshwater mussels’ complex life histories and essential ecological roles, and offer solutions that will lead to the restoration, recovery, and protection of these organisms that provide important ecosystem services.
Restoration of mussels typically focuses on either subtidal or intertidal habitats, although it is important to consider the full historical range of a species. However, it remains unclear how environmental changes can impact the ability of mussels to survive in tidal heights where they occurred historically. Additionally, there is limited research on the viability of reducing mussel stock size for restoration purposes. In this study, green-lipped mussels Perna canaliculus of 2 size classes (80 and 60 mm) were assessed when transplanted as a single size class or as mixed cohorts in 9 m ² plots at 3 shore heights (i.e. neap low tide, spring low tide, and subtidal). The mussels were sampled over a 1 yr period to understand the effect that shore height and size class had on mussel metrics, such as survival, growth, and condition. The results revealed that shore height had a greater effect than size class on mussel survival, with a total loss of mussels transplanted into areas that were exposed at neap tides in contrast to 39% mussel survival transplanted into areas that were only exposed on spring low tides. Further, mussels transplanted in the adjacent subtidal had higher overall survival (74%). This suggests that aerial exposure time determines the upper vertical limit for restoration by transplantation of mussels sourced from aquaculture, despite their historical distribution. The results of this study also support the use of smaller mussels (~60 mm) for transplantation for mussel reef restoration, as a 25% reduction in size resulted in 50% more mussels being deployed.
1. Ecological restoration includes specific technical phases over the course of an ecosystem recovery process. In the marine environment and for oyster reef restoration, the installation and implementation of pilot reefs close the gap between feasibility studies with small-scale experiments and designated upscaling for marine conservation measures.
2. Against this background, this study presents the design, planning and installation of the first pilot oyster reef in offshore sublittoral regions of the North Sea. The work was conducted as part of marine protected area management in the Natura 2000 site Borkum Reef Ground in the German Bight, in the area of historical offshore oyster grounds.
3. It includes logistical considerations, material selection, methodology for reef base construction and deployment of European flat oysters Ostrea edulis as spat-on-shell, young and adult single seed oysters, and spat-on-reef, as well as the development of an efficient monitoring approach for reef-associated biodiversity.
4. Native Oyster Restoration Alliance monitoring methodologies, such as underwater visual census and seabed images were selected, tested and successfully adapted for the pilot oyster reef and study site. The evaluation and optimization of offshore sublittoral oyster reef monitoring are presented here, and biodiversity metrics are put into perspective with data from recent and historical studies.
5. Results show a few mobile fauna species (e.g., fish and decapods) as first colonizers after reef construction. One year later, biodiversity increased due to a larger number of invertebrate and fish species. However, the pilot oyster reef community still represents an early recolonization stage, with lower biodiversity than historical records.
6. This study presents a proof of concept for the design, planning and construction of an offshore oyster reef and indicates stages in the recovery process. Strategies to optimize and to complement reef-monitoring in challenging environments are discussed, emphasizing additional molecular and functional analyses for future assessments.
The loss of newly translocated species directly contributes to low rates of reintroduction success in both terrestrial and aquatic ecosystems. In this study, experimental reintroductions of green-lipped mussels Perna canaliculus into a shallow coastal habitat were conducted across 5 week-long experimental translocations within a 10 mo period (April 2021-January 2022) to relate temporal variations in predator abundance, predator size, and environmental parameters (water temperature, rainfall, days before/after full moon, turbidity, wind speed, wind direction) to variations in mussel survival. Predator counts from timelapse camera images gathered over the first 4 d after each deployment were used as a proxy for potential predator pressure. Timelapse images (n = 8561) allowed for a census of 2371 individuals from 10 different mobile species, 5 of which were known bivalve predators (Australasian snapper, New Zealand eagle ray, rig shark, octopus, and an unidentifiable ray species), with Australasian snapper contributing to 98% of overall species counts. At the end of the study, mean mussel survival ranged from 0 ± 0 SE% to 56 ± 8 SE% and was best predicted by changes in turbidity and the total number of predators among deployments (R ² = 0.445). Patterns in predator abundance were best explained by time of year and did not share strong correlations among environmental parameters (rho = 0.015). These results suggest that planning deployments of mussels for cooler times of the year when water clarity is high and predator abundance is low may substantially increase immediate survivorship of translocated mussels and improve reintroduction success.
Fisheries managers, seafood harvesters, and other commercial fishing stakeholders are increasingly seeking information regarding the regional economic impacts resulting from fisheries management decisions. This project contributes to addressing this need by generating estimates of key economic measures associated with the commercial fishing industry - and connected industries - of the Choptank River System. This project is a Regional Economic Impact Analysis, which accounts for changes in spending and the resulting changes in regional economic activity.
https://spo.nmfs.noaa.gov/content/tech-memo/estimating-ecological-benefits-and-socio-economic-impacts-oyster-reef-restoration
Ecological restoration, when implemented effectively and
sustainably, contributes to protecting biodiversity; improving
human health and wellbeing; increasing food and water security;
delivering goods, services, and economic prosperity; and
supporting climate change mitigation, resilience, and adaptation.
It is a solutions-based approach that engages communities,
scientists, policymakers, and land managers to repair ecological
damage and rebuild a healthier relationship between people
and the rest of nature. When combined with conservation and
sustainable use, ecological restoration is the link needed to
move local, regional, and global environmental conditions
from a state of continued degradation, to one of net positive
improvement. The second edition of the International Principles
and Standards for the Practice of Ecological Restoration
(the Standards) presents a robust framework for restoration
projects to achieve intended goals, while addressing challenges
including effective design and implementation, accounting
for complex ecosystem dynamics (especially in the context of
climate change), and navigating trade-offs associated with land
management priorities and decisions.
Ecological restoration, when implemented effectively and sustainably, contributes to protecting biodiversity; improving human health and wellbeing; increasing food and water security; delivering goods, services, and economic prosperity; and supporting climate change mitigation, resilience, and adaptation. It is a solutions-based approach that engages communities, scientists, policymakers, and land managers to repair ecological damage and rebuild a healthier relationship between people and the rest of nature. When combined with conservation and sustainable use, ecological restoration is the link needed to move local, regional, and global environmental conditions from a state of continued degradation, to one of net positive improvement. The second edition of the International Principles and Standards for the Practice of Ecological Restoration (the Standards) presents a robust framework for restoration projects to achieve intended goals, while addressing challenges including effective design and implementation, accounting for complex ecosystem dynamics (especially in the context of climate change), and navigating trade-offs associated with land management priorities and decisions.
There is a growing body of science to suggest that there is a mutualistic relationship between habitat restoration projects and community volunteers and participation. Restoration projects and programs benefit from community participation via an added labor force and by fostering community investment and support, which is critical for project success and future restoration investments. Community participants gain physically and psychologically rewarding experiences from being a part of restoration projects, while fostering an environmental ethos. Oyster restoration serves as particularly ideal opportunities for engaging community volunteers and participation. These additional values provided to a community where oyster restoration is taking place is an important additive benefit that oyster restoration provides. The nature by which many oyster restoration projects are implemented offers satisfying opportunities for community members to participate in physically rewarding, hands-on work. Many oyster restoration programs are also ideal for incorporating student or citizen science, or broad-scale education and outreach. Despite the growing science to support the value of volunteer and community participation, coupled with increased oyster restoration, there is a paucity of information for project managers to turn-to for guidance as to how community participation can be built into oyster restoration projects and programs. This chapter presents five cases from the United States to demonstrate the broad, and often unique, opportunities to incorporate community and volunteer participation into oyster restoration.
Coastal ecosystem restoration is accelerating globally as a means of enhancing shoreline protection, carbon storage, water quality, fisheries, and biodiversity. Among the most substantial of these efforts have been those focused on re‐establishing oyster reefs across the US Atlantic and Gulf coasts. Despite considerable investment, it is unclear how the scale of and approaches toward oyster restoration have evolved. A synthesis of 1768 projects undertaken since 1964 reveals that oyster substrate restoration efforts have primarily been concentrated in the Chesapeake Bay and the Gulf Coast, have been heavily reliant on oyster shell, and have re‐established 4.5% of the reef area that has been lost across all regions. By comparing costs to ecosystem service benefits, we discovered that the return‐on‐investment of oyster restoration varies widely, but generally increases with project size. To facilitate the recovery of coastal ecosystems and their services, scientists and resource managers must adopt a new restoration paradigm prioritizing investment in sites that maximize economic and ecological benefits and minimize construction costs.
Management actions to protect endangered species and conserve ecosystem function may not always be in precise alignment. Efforts to recover the California Ridgway’s Rail (Rallus obsoletus obsoletus; hereafter, California rail), a federally and state-listed species, and restoration of tidal marsh ecosystems in the San Francisco Bay estuary provide a prime example of habitat restoration that has conflicted with species conservation. On the brink of extinction from habitat loss and degradation, and non-native predators in the 1990s, California rail populations responded positively to introduction of a non-native plant, Atlantic cordgrass (Spartina alterniflora). California rail populations were in substantial decline when the non-native Spartina was initially introduced as part of efforts to recover tidal marshes. Subsequent hybridization with the native Pacific cordgrass (Spartina foliosa) boosted California rail populations by providing greater cover and increased habitat area. The hybrid cordgrass (S. alterniflora × S. foliosa) readily invaded tidal mudflats and channels, and both crowded out native tidal marsh plants and increased sediment accretion in the marsh plain. This resulted in modification of tidal marsh geomorphology, hydrology, productivity, and species composition. Our results show that denser California rail populations occur in invasive Spartina than in native Spartina in San Francisco Bay. Herbicide treatment between 2005 and 2012 removed invasive Spartina from open intertidal mud and preserved foraging habitat for shorebirds. However, removal of invasive Spartina caused substantial decreases in California rail populations. Unknown facets of California rail ecology, undesirable interim stages of tidal marsh restoration, and competing management objectives among stakeholders resulted in management planning for endangered species or ecosystem restoration that favored one goal over the other. We have examined this perceived conflict and propose strategies for moderating harmful effects of restoration while meeting the needs of both endangered species and the imperiled native marsh ecosystem.
As part of an applied research project, an engineering design and structure deployment study was conducted to investigate the feasibility of performing in-situ larval set of Crassostrea virginica within a temporarily deployed containment barrier. The intent of the barrier was to contain free-swimming larvae to maximize set on emplaced shell substrate. The project site was located in the Chesapeake Bay waters of Maryland (USA) in a tidal tributary adjacent to the Patuxent River. The project included a practical ocean engineering approach to specify barrier and mooring system components by investigating environmental design criteria, applying computational fluid dynamic techniques, and characterizing the barrier and mooring leg shape and tension with catenary equations. Following analysis and component specification, both the barrier and mooring system components were deployed. The structure consisted of two, 15 m length sections of Type-III turbidity curtain with a skirt depth of 4.57 meters, but adjustable with furling lines. The structure enclosed an area of about 65 m2 with clean oyster shell substrate and was held vertically in the water column with ∼0.3 meter floats at the surface and chain at the bottom of the skirt. It was deployed with an 8-point spread mooring configuration to maintain its shape in a 0.51 m/s current and 0.75 meter waves. After deployment, larvae were introduced into the enclosed volume and allowed three days to set before removing the barrier. A companion biological field study demonstrated that the technique could add over 180 juvenile oysters/m2 to the site with clean cultch. Recommendations for a potential scaled-up version are also discussed.
Horse mussel (Modiolus modiolus) shellfish reefs are a threatened and declining habitat in the North East Atlantic and support high levels of biodiversity. Shellfish can influence the surrounding water column and modify the quality of material that reaches the seabed by filtering water, actively depositing particles and changing the benthic boundary layer due to surface roughness. In the present study M. modiolus biodeposition was measured in a field location for the first time. The results show that M. modiolus enhance sedimentation and contribute to the downward flux of material to the seabed. Approximately 30% of the total sediment deposition was attributed to active filter feeding and overall, the presence of horse mussels enhanced deposition two fold. The results are discussed in terms of the potential for horse mussel reefs to provide ecosystem services to society, through functions such as benthopelagic coupling and sediment stabilisation. Highlighting the societal benefits supplied by marine habitats can help prioritise conservation efforts and feed into the sustainable management of coastal water bodies.
Victoria has lost vast areas (>95%) of native flat oyster (Ostrea angasi, Sowerby 1871) and blue mussel (Mytilus edulis galloprovinicialis, Lamarck 1819) reefs from estuarine and coastal waters since European settlement. We document the decline of these reefs by examining indigenous use of shellfish, the decimation of oyster reefs by dredge fishing in early colonial days (1840s–1860s) and later removal of mussel reefs by the mussel and scallop dredging industry (1960s‒1990s). Review of current scientific information reveals no notable areas of continuous oyster reef in Victoria and we consider this habitat to be functionally extinct. While the large-scale removal and destructive fishing practices that drove the rapid declines have not occurred since the mid-1990s, a natural recovery has not occurred. Recovery has likely been hampered historically by a host of factors, including water quality and sedimentation, lack of shell substrate for settlement, chemical pollution impacts, disease of native flat oysters (Bonamia), and more recently introduced species that compete with or prey on shellfish. However, research in the United States has demonstrated that, by strategic selection of appropriate sites and provision of suitable settlement substrates, outplanting of aquaculture-reared oysters and mussels can re-establish shellfish reefs. While a long-term sustained and structured approach is required, there is potential to re-establish shellfish reefs as a functioning ecological community in Victoria’s coastal environment.
The eastern oyster (Crassostrea virginica) remains at historically low levels throughout the Chesapeake Bay. Recent efforts to restore oysters in the bay have focused on establishing a series of sanctuaries, or no-take zones, to increase oyster broodstock in selected tributaries. Oyster parasites continue to affect the rate of recovery in these tributaries; however, innovative management strategies, advances in aquaculture technology, and the availability of disease-tolerant broodstock from the lower Chesapeake Bay are providing ways to involve the public directly in restoration of this resource. A 1996 management decision to transplant large wild-caught oysters onto an oyster broodstock sanctuary reef in the Great Wicomico River, Virginia, was followed by greatly increased abundance of juvenile oysters throughout that river in 1997. Using that result as a model for strategic oyster reef restoration, citizens and school students have been enlisted to grow large numbers of hatchery-produced native oysters for restocking other sanctuary reefs throughout Chesapeake Bay. Efforts to supplement natural oyster populations in Hampton Roads, Virginia, began in May 1998, with the transplanting of 65,000 hatchery-produced oysters grown by school students. The oysters were transplanted onto strategically located sanctuary reefs constructed in the Lynnhaven and Elizabeth rivers. Surveys of these reefs following the oysters' spawning season have revealed order-of-magnitude increases in the abundance of juvenile oysters on both reefs, and correspondingly high spat settlement rates on oyster grounds surrounding the reefs. These results demonstrate that stocking strategically located broodstock reefs with hatchery-produced oysters grown by citizens can be an effective strategy for oyster restoration in the Chesapeake Bay.