Perspectives for flat oyster reef restoration
Dutch experiences with shellfish & eco-engineering
November 2012,
Christiaan van Sluis, Jeroen Jansen and Aad Smaal
Why restoration?
Provision of ecosystem services through:
• Filter feeder: filtration + nutrient regeneration
• Reintroduction reef habitat by ecosystem engineer (N2000)
• Fish & bird feed: oysters and associated species
• Potential for sustainable exploitation
Stimulation of flat oysters makes sense:
- natural, cultural & culinary heritage
Daniel Ridgway Knight:
The oyster gatherer
Regime shifts in changing ecosystems
Questions:
- Where there oysters before
- Why oysters disappeared?
Can we find and
reduce barriers
to reintroduction?
Scheffer et al. 2001
Ecosyste
m s
tate
Unknown environmental conditions
!
Why am I (I-mares) here?
Some NGO’s support restoration of flat oyster beds
Group of people willing to contribute
IMARES works on shellfish restoration and culture:
● Mussel bed monitoring and restoration
● Flat oyster aquaculture in the Dutch Delta
● Building with Nature - ecosystem engineering
1) MUSSELWAD –monitoring existing beds
Research: Why mussel beds disappear/remain over years?
Understanding bank development and survival through:
Hydrodynamics, erosion by waves, wind and tides
● By dissipating wave action, mussels on the edge
project mussels in the middle (Donker et al,
submitted).
● Mussel banks originate at low dynamic sites
How does predation determine survival?
2) Mussel bed restoration for birds
1) Seeding on existing and created littoral oyster banks
● Oysters occur in most mussel banks
● Oysters protect mussels against erosion
● Oysters form predation refuges for small mussels
● Also without mussels oysters are foraging ground
2) Seeding on former littoral mussel banks
Monitoring mussel bed condition
● bed density and mussel density
● Individual mussel condition, foraging birds, waves, current velocities
Flat oyster culture in the Dutch Delta
How to ensure survival and growth:
Expert knowledge of:
● Spat collection
● Larval assessment
● Disease monitoring with CVI
● Development of genetic identification
● Hatchery capacity & Purification breeding
IMARES participates in local shellfish culture group
Shellfish knowledge groups - Oysterculture
Activities
Share: Qualities, characteristics and skills
Construct alliances with others partners
Give trust (and hence receive it)
Results:
Increased rentability
Maximized “learning from each other”
with shared profits
Good functioning and innovating shellfish industry
Industry
Innovators
(Leads)
Science
(supports and
facilitates)
Innovation
Knowledge transfer
Government
(Facilitates)
Building with Nature – shellfish reefs
Loss of intertidal flats due to morphological misbalance
Question:
Can we stabilize intertidal flats with shellfish reefs?
- Morphology
- Biology
- Governance
Oyster reef creation in the Southwest Delta
Using shellfish reefs against erosion of intertidal flats
Experience
Height in the intertidal
Fouling
Recruitment
ECOBAS Bangladesh:
Eco-engineered coastal defence integrated with
sustainable aquatic food production
More lessons on turbidity, inundation time and hydrodynamic stress
Building with Nature: lessons learned
Biosphere
Minimum population size for sufficient recruitment: spawning stock biomass (adult females) needed (potentially aquaculture)
Competition: selection of brood stock: adaptive capacity, disease free self-sustaining, competitive (with Pacific oyster)
Fouling
Food availability
Bonamia
Support each life stage
Hydrosphere
Hydrodynamics, currents (flushing of larvae), waves, wind, tides
Temperature (Sensitive, but also adaptive to low temperature)
Nutrients and pollution
Salinity
pH
Turbidity
Contaminants (TBT & Cupper)
Lithosphere and Atmosphere
Presence of hard substrates for settling (Sedentary life)
Substrate within dispersal range
Sedimentation
Silt vs. organic matter
Governance
•Awareness: need for public & stakeholder involvement
•Funding opportunities
•Cost effectiveness: knowledge based approach
•Legislation, sometimes new activities not allowed
•see > 30 recommendations of Ashton & Brown in prep
Discussion
Breaking barriers:
Reason for disappearance.
- Diseases – is this a real obstacle?
- Disturbance – wind parks
- Regime shift (s)? – don’t know
Habitat suitability (4 Spheres)
Governance – policy support